http://registry.faa.gov/N771MM
NTSB Identification: ERA15FA085
14 CFR Part 91: General Aviation
Accident occurred Monday, December 29, 2014 in Lake Worth, FL
Probable Cause Approval Date: 03/06/2017
Aircraft: ROBINSON HELICOPTER R22 BETA, registration: N771MM
Injuries: 1 Fatal, 1 Serious.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The purpose of the instructional helicopter flight was to review advanced maneuvers in preparation for the student pilot’s upcoming stage check. The student stated that he and the flight instructor had conducted 3 approaches and landings before initiating a practice autorotation. He stated that as the helicopter descended through 100 ft in the autorotation, the instructor applied throttle in an attempt to recover, but the engine did not respond. A witness stated that, about halfway through the helicopter’s autorotative descent, it appeared to momentarily level off before abruptly entering a nose-down attitude and descending to ground contact. A surveillance video showed the helicopter descending rapidly at a steep angle in the last 2 seconds before impact. The helicopter impacted terrain about 700 ft north of the runway threshold, fatally injuring the instructor and seriously injuring the student. Postaccident examination of the helicopter and a test run of the engine revealed no mechanical anomalies that would have precluded normal operation.
The flight school’s published procedure for practice autorotations instructed the pilot to initiate the maneuver first by lowering the collective, then reducing the throttle to idle. The practice of reducing the throttle to idle was contrary to manufacturer guidance for this maneuver, which stated that the throttle should be adjusted only enough to allow for a small tachometer needle separation in order to reduce the chance of inadvertent engine stoppage during the maneuver. The practice of reducing throttle to idle introduced greater susceptibility to a loss of engine power, though it could not be determined whether a loss of power occurred before the accident.
Based on conflicting statements from the student, it could not be determined who was controlling the helicopter during the entry into and throughout the autorotation before about 100 ft. The helicopter’s trajectory described by a witness and as captured on surveillance video suggested a rapid, uncontrolled descent during the final portion of the autorotation, consistent with a main rotor stall; likely as a result of a premature application of collective pitch. This allowed the rotor rpm to decay below the normal operating range at an altitude that was insufficient for power recovery. In the event that the helicopter did experience a loss of power during the maneuver, the helicopter should have been able to attain a safe landing following a steady-state autorotation. The helicopter manufacturer published notices to pilots warning that main rotor stall due to low rotor rpm could occur rapidly, at any airspeed, and that if allowed to develop, recovery could become “virtually impossible.”
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
A main rotor stall due to low rotor rpm, which resulted in an uncontrolled descent into terrain. Contributing to the accident was the flight instructor’s delayed remedial action.
***This report was modified on January 25, 2017. Please see the public docket for this accident to view the original report.***
HISTORY OF FLIGHT
On December 29, 2014, at 1025 eastern standard time, a Robinson R22 Beta, N771MM, was substantially damaged when it impacted terrain while performing an autorotation near Palm Beach County Park Airport (LNA), Lake Worth, Florida. The flight instructor (CFI) was fatally injured, and the student pilot sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which departed about 0940. The flight was operated by Palm Beach Helicopters, Inc., and was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.
A witness, who was a CFI, reported that he and a student were taxiing their airplane to runway 15 for takeoff when they heard the accident helicopter announce its position on a right base leg, with the intent to conduct an autorotation to taxiway Bravo. The CFI then offered to hold at the airplane's present position to allow the helicopter more room to conduct the maneuver. He stated that the helicopter pilot thanked him, and shortly thereafter, he observed the helicopter enter a "rapid descent typical of [autorotation]" from an altitude of between 800-1,000 feet above ground level (agl). About 500 feet agl, the helicopter appeared to level off, then pitched abruptly nose-down and descended to ground contact. Just prior to impact, he heard a panicked radio transmission from the helicopter that was mostly unintelligible. He also stated that, based on the accent he heard, he believed the CFI onboard the helicopter was conducting all radio transmissions.
Another CFI, who was taxiing a helicopter with a student on the south side of the airport, reported hearing the accident helicopter transmit, "we're going in the grass" over the airport's common traffic advisory frequency. Shortly thereafter, an airplane in the airport traffic pattern reported that there was a helicopter down, and the CFI in the helicopter flew to the accident site to render assistance.
In a statement to law enforcement two days after the accident, the student pilot recounted that he and the CFI were practicing autorotations following a simulated engine failure. The student stated that he could not recall whether he or the CFI initiated the autorotation. About 100 feet above ground level, the CFI said, "We're going down, we're going down," and at that time, the CFI was controlling the helicopter. The student stated that, until that point, the autorotation had "appeared pretty normal," and he added, "I don't know if the engine cut off, or the engine didn't turn back on."
In a subsequent interview, conducted about two weeks after the accident, the student stated that the flight was Lesson 2 in Stage 3 of the school's private pilot training course. He reported that he could not recall most of the accident flight, but recalled that prior to the accident, he and the CFI had been flying for approximately 40 minutes and had conducted 2 or 3 steep approaches as well as a maximum-performance takeoff. The accident autorotation was the first of the accident flight. He stated that he could not recall who initiated the autorotation or the rotor rpm indication during the maneuver. He remembered that the CFI was controlling the helicopter as it descended through about 100 feet above ground level, and as the CFI rolled on the throttle in an attempt to recover, there was no response from the engine. The CFI stated, "We're going down, we're going down." The student also stated that, on the downwind leg of the traffic pattern, he observed the CFI using his cell phone and stated that he appeared to be conducting a video call, as he briefly saw someone on the phone's screen. He stated that the CFI turned the phone to face outside of the helicopter as if he was showing the view out the helicopter's windscreen to the individual on the phone. He could not recall when the CFI discontinued the use of the phone.
In a written statement provided after the interview, the student recalled that the CFI "asked for the controls," on the downwind leg of the traffic pattern prior to entering the autorotation. The student stated that he "handed over the controls and looked south out my door enjoying the view." The student then recalled looking at the ground "in a nose down attitude" as the helicopter descended, and seeing the CFI "fighting with the cyclic and collective."
Surveillance video from a building near the accident site captured approximately the last 2 seconds of the flight before impact, and showed the helicopter descending rapidly at a steep angle.
PERSONNEL INFORMATION
The CFI held commercial pilot and flight instructor certificates, both with ratings for rotorcraft-helicopter and instrument helicopter; as well as an airframe and powerplant mechanic certificate. His most recent Federal Aviation Administration (FAA) first-class medical certificate was issued in March 2014. Review of operator records revealed the CFI had about 397 total hours of flight experience, of which about 280 hours were in the accident helicopter make and model. He had accumulated about 121 hours of flight instruction given.
The student held an FAA second-class medical and student pilot certificate, which was issued in December 2012. He reported about 37 total hours of flight time, all of which was in the accident helicopter make and model.
AIRCRAFT INFORMATION
The helicopter was manufactured in 1996 and was equipped with one Lycoming O-360 series, 145 hp reciprocating engine. Review of maintenance records provided by the operator indicated that the helicopter's most recent 100-hour inspection was completed on December 1, 2014. At that time, the airframe had accumulated a total time of 4,162.9 hours, and the engine had accumulated 1,978.7 hours since its most recent overhaul. The helicopter's 2,200-hour inspection was completed on February 13, 2013 at a total airframe time of 2,184.2 hours.
METEOROLOGICAL INFORMATION
The 0953 automated weather observation at PBI recorded wind from 180 degrees at 7 knots, 10 miles visibility, scattered clouds at 2,100 ft, temperature 26 degrees C, dew point 22 degrees C, and an altimeter setting of 30.13 inches of mercury. Review of a carburetor icing probability chart revealed the potential for serious carburetor icing at glide power.
WRECKAGE AND IMPACT INFORMATION
The helicopter came to rest on its left side in a grassy area about 700 feet northwest of the runway 15 threshold at LNA. The wreckage path was oriented approximately 140 degrees magnetic, and extended about 75 feet from the initial impact point to where the fuselage came to rest. The initial impact point was identified as a large metal stake, about 3 feet in height. The second point of impact was a small crater measuring about 4 feet long and 1 foot deep, located about 15 feet past the initial impact point. A portion of the forward skid crosstube was located in the crater. The vertical stabilizer, horizontal stabilizer, and portion of the tail rotor came to rest next to the crater. The tail boom was separated from the fuselage, and fractured into several pieces, some of which displayed signatures consistent with main rotor blade contact. The skids separated from the fuselage and were fractured into several sections, which were located along the wreckage path.
The fuselage exhibited downward crushing, and the cabin was fractured aft of the seat structures. Both the auxiliary and main fuel tanks were intact and contained fuel, and both fuel caps were secure. The fuel vent tubes were separated from the auxiliary tank by impact, which allowed fuel to drain from the tanks following the accident.
The main rotor remained attached to the fuselage. One blade was bent up and displayed several chordwise creases along its span. The second blade was bent up about 45 degrees near its root. Neither blade displayed significant leading edge damage. The tail rotor drive shaft separated from the helicopter during the accident sequence, and a 5-foot portion was located about 500 feet west of the main wreckage. The aft portion of the tail rotor drive shaft was not recovered.
The helicopter was removed from the accident site and transported to a secure facility for further examination. Flight control continuity was confirmed from the cockpit area to the main rotor system. Tail rotor control continuity was established from the cockpit to the intermediate flex coupling. The main rotor gearbox rotated smoothly by hand with no anomalies observed. Examination of the v-belts, sheaves, and overrunning clutch also revealed no anomalies. Tail rotor drive continuity was established from the upper drive sheave to the intermediate flex coupling. The tail rotor gearbox rotated smoothly, with no anomalies noted.
The engine remained attached to the airframe at its mount. The mixture control wire was impact-separated from the mixture control arm. The carburetor heat control was bent, and was in the off position. The carburetor air box was partially crushed, and the carburetor heat slider valve was in a mid-travel, partially open position. The carburetor remained attached to the engine, and the throttle control arm was observed about 1/8 inch from the full-throttle position. The exhaust system was partially crushed. The sparkplugs were removed and displayed normal wear characteristics. The engine was rotated by hand at the cooling fan, and thumb compression was obtained on all cylinders. Crankshaft continuity was established to the accessory gears. Oil was added to the engine to facilitate a test run, and when power was applied to the engine starter, the engine started, accelerated, and ran continuously for several minutes utilizing the fuel onboard. A magneto check was performed with no anomalies noted.
The engine was shut down, and the carburetor, oil filter, and oil suction screen were removed for examination. The carburetor float bowl contained blue liquid consistent with 100LL aviation fuel, and did not display any sign of contamination. There was no damage to the internal components of the carburetor, and the fuel inlet screen was absent of debris.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy was performed on the CFI by the Office of the District Medical Examiner, District 15, Palm Beach County, Florida. The cause of death was identified as blunt force injuries. Toxicological testing was performed by the FAA Bioaeronautical Sciences Research Laboratory in Oklahoma City, Oklahoma. Testing was negative for carbon monoxide, ethanol, and all tested-for drugs and their metabolites.
ADDITIONAL INFORMATION
Cell Phone Information
The CFI's cell phone was retained for examination in the NTSB vehicle recorders laboratory; however, the device was passcode-protected and could not be unlocked. Usage records obtained from the cellular service provider could not conclusively determine whether the phone was in use at the time of the accident.
Practice Autorotations
According to the pilot training syllabus provided by the flight school, the objective of Stage 3, Lesson 2 was for the student to practice advanced maneuvers and procedures, including normal and steep approach, normal and maximum performance takeoff, hovering, hover taxi, air taxi, ground reference maneuvers, emergency operations, autorotation to a power recovery, loss of tail rotor, stuck pedal, hovering out of ground effect, and confined area operation.
Review of the student's training record indicated that he completed Stage 2 of the syllabus on December 23, 2014. Instructor notes for the previous flight, dated December 22, 2014, indicated, "gap in training is evident in proficiency, basic straight [and] level unsatisfactory, [aeronautical decision making] needs work, approaches need work."
The flight school specified that all 180-degree and straight-in autorotations be terminated with a power recovery throughout the private pilot training course. School policy stated that all landings and practice autorotations were to be performed to a hard-surfaced runway or taxiway.
The flight school's written procedures for a straight-in autorotation with power recovery indicated that the maneuver should be initiated at an altitude of 700 feet agl after clearing the area for potential traffic conflicts and applying carburetor heat. Upon selecting a landing site, the autorotation was entered by lowering the collective to its full-down position, then rolling the throttle to the full idle position, where the procedure specified it should be held "firmly against the stop for the remainder of the autorotation." About 40 feet agl, the recovery was initiated by applying aft cyclic to bring the helicopter to a skids-level attitude, where it was held for 3 seconds prior to entering a flare. At that time, the throttle was "crack[ed] open" to allow the rpm governor to operate, forward cyclic applied, and the collective raised to bring the helicopter to a hover about 5 feet agl. The maneuver guide also stated, "Make an IMMEDIATE power recovery if the following conditions do not exist through 100' AGL: Aircraft aligned with touchdown point; Rotor RPM in the green; Airspeed within +/- 5 [knots] of 65 [knots]; Rate of descent <1,500 fpm".
The manufacturer's Pilots Operating Handbook outlined the following procedure for a practice autorotation with a power recovery: "1. Adjust carb heat as required. 2. Lower collective to down stop and adjust throttle as required for small tachometer needle separation. CAUTION: To avoid inadvertent engine stoppage, do not chop throttle to simulate a power failure. Always roll throttle off smoothly for a small visible needle split. 3. Adjust collective to keep rotor RPM in green arc and adjust throttle for small needle separation. 4. Keep airspeed 60 to 70 KIAS. 5. At about 40 feet AGL, begin cyclic flare to reduce rate of descent and forward speed. 6. At about 8 feet AGL, apply forward cyclic to level aircraft and raise collective to control descent. Add throttle if required to keep RPM in green arc."
Robinson Helicopter Company Safety Notice SN-38, "Practice Autorotations Cause Many Training Accidents," stated, "There have been instances when the engine has quit during practice autorotation. To avoid inadvertent engine stoppage, do not roll throttle to full idle. Reduce throttle smoothly for a small visible needle split, then hold throttle firmly to override governor. Recover immediately if engine is rough or engine RPM continues to drop."
Safety Notice SN-24, "Low RPM Rotor Stall Can Be Fatal," stated, "Rotor stall is very similar to the stall of an airplane wings at low airspeeds. As the airspeed of an airplane gets lower…the angle of attack of the wing must be higher for the wing to produce the lift required to support the weight of the airplane…The same thing happens during rotor stall with a helicopter except it occurs due to low rotor RPM instead of low airspeed. As the RPM of the rotor gets lower, the angle of attack of the rotor blades must be higher to generate the lift required to support the weight of the helicopter…Even if the collective is not raised by the pilot to provide the higher blade angle, the helicopter will start to descend until the upward movement of air to the rotor provides the necessary increase in blade angle of attack…The increased drag on the blades acts like a huge rotor brake causing the rotor RPM to rapidly decrease, further increasing the rotor stall. As the helicopter begins to fall, the upward rushing air continues to increase the angle of attack on the slowly-rotating blades, making recovery virtually impossible, even with full down collective."
FAA publication P-8740-71, "Planning Autorotations,"was intended to raise flight instructor awareness to the hazards of training students in autorotations and provide guidelines and parameters for conducting practice autorotations. The pamphlet concluded, "The number one error in practice autorotations is the failure of the flight instructor to take control of the aircraft and terminate the maneuver before it progresses to a point where the flight instructor is not capable of recovering the aircraft in time to prevent damage to the aircraft or injury to personnel.
REMEMBER: As a flight instructor, you are the most knowledgeable and experienced person in that helicopter. Do not let your student fly the helicopter into some corner of its performance envelope where it is not recoverable."
Luis Aviles and Jonathan Desouza
NTSB Identification: ERA15FA085
14 CFR Part 91: General Aviation
Accident occurred Monday, December 29, 2014 in Lake Worth, FL
Aircraft: ROBINSON HELICOPTER R22 BETA, registration: N771MM
Injuries: 1 Fatal, 1 Serious.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
HISTORY OF FLIGHT
On December 29, 2014, at 1025 eastern standard time, a Robinson R22 Beta, N771MM, was substantially damaged when it impacted terrain while performing an autorotation near Palm Beach County Park Airport (LNA), Lake Worth, Florida. The flight instructor (CFI) was fatally injured, and the student pilot sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which departed about 0940. The flight was operated by Palm Beach Helicopters, Inc., and was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.
A witness, who was a CFI, reported that he and a student were taxiing their airplane to runway 15 for takeoff when they heard the accident helicopter announce its position on a right base leg, with the intent to conduct an autorotation to taxiway Bravo. The CFI then offered to hold at the airplane's present position to allow the helicopter more room to conduct the maneuver. He stated that the helicopter pilot thanked him, and shortly thereafter, he observed the helicopter enter a "rapid descent typical of [autorotation]" from an altitude of between 800-1,000 feet above ground level (agl). About 500 feet agl, the helicopter appeared to level off, then pitched abruptly nose-down and descended to ground contact. Just prior to impact, he heard a panicked radio transmission from the helicopter that was mostly unintelligible. He also stated that, based on the accent he heard, he believed the CFI onboard the helicopter was conducting all radio transmissions.
Another CFI, who was taxiing a helicopter with a student on the south side of the airport, reported hearing the accident helicopter transmit, "we're going in the grass" over the airport's common traffic advisory frequency. Shortly thereafter, an airplane in the airport traffic pattern reported that there was a helicopter down, and the CFI in the helicopter flew to the accident site to render assistance.
In a statement to law enforcement two days after the accident, the student pilot recounted that he and the CFI were practicing autorotations following a simulated engine failure. The student stated that he could not recall whether he or the CFI initiated the autorotation. About 100 feet above ground level, the CFI said, "We're going down, we're going down," and at that time, the CFI was controlling the helicopter. The student stated that, until that point, the autorotation had "appeared pretty normal," and he added, "I don't know if the engine cut off, or the engine didn't turn back on."
In a subsequent interview, conducted about two weeks after the accident, the student stated that the flight was Lesson 2 in Stage 3 of the school's private pilot training course. He reported that he could not recall most of the accident flight, but recalled that prior to the accident, he and the CFI had been flying for approximately 40 minutes and had conducted 2 or 3 steep approaches as well as a maximum-performance takeoff. The accident autorotation was the first of the accident flight. He stated that he could not recall who initiated the autorotation or the rotor rpm indication during the maneuver. He remembered that the CFI was controlling the helicopter as it descended through about 100 feet above ground level, and as the CFI rolled on the throttle in an attempt to recover, there was no response from the engine. The CFI stated, "We're going down, we're going down." The student also stated that, on the downwind leg of the traffic pattern, he observed the CFI using his cell phone and stated that he appeared to be conducting a video call, as he briefly saw someone on the phone's screen. He stated that the CFI turned the phone to face outside of the helicopter as if he was showing the view out the helicopter's windscreen to the individual on the phone. He could not recall when the CFI discontinued the use of the phone.
In a written statement provided after the interview, the student recalled that the CFI "asked for the controls," on the downwind leg of the traffic pattern prior to entering the autorotation. The student stated that he "handed over the controls and looked south out my door enjoying the view." The student then recalled looking at the ground "in a nose down attitude" as the helicopter descended, and seeing the CFI "fighting with the cyclic and collective."
Surveillance video from a building near the accident site captured approximately the last 2 seconds of the flight before impact, and showed the helicopter descending rapidly at a steep angle.
PERSONNEL INFORMATION
The CFI held commercial pilot and flight instructor certificates, both with ratings for rotorcraft-helicopter and instrument helicopter; as well as an airframe and powerplant mechanic certificate. His most recent Federal Aviation Administration (FAA) first-class medical certificate was issued in March 2014. Review of operator records revealed the CFI had about 397 total hours of flight experience, of which about 280 hours were in the accident helicopter make and model. He had accumulated about 121 hours of flight instruction given.
The student held an FAA second-class medical and student pilot certificate, which was issued in December 2012. He reported about 37 total hours of flight time, all of which was in the accident helicopter make and model.
AIRCRAFT INFORMATION
The helicopter was manufactured in 1996 and was equipped with one Lycoming O-360 series, 145 hp reciprocating engine. Review of maintenance records provided by the operator indicated that the helicopter's most recent 100-hour inspection was completed on December 1, 2014. At that time, the airframe had accumulated a total time of 4,162.9 hours, and the engine had accumulated 1,978.7 hours since its most recent overhaul. The helicopter's 2,200-hour inspection was completed on February 13, 2013 at a total airframe time of 2,184.2 hours.
METEOROLOGICAL INFORMATION
The 0953 automated weather observation at PBI recorded wind from 180 degrees at 7 knots, 10 miles visibility, scattered clouds at 2,100 ft, temperature 26 degrees C, dew point 22 degrees C, and an altimeter setting of 30.13 inches of mercury. Review of a carburetor icing probability chart revealed the potential for serious carburetor icing at glide power.
WRECKAGE AND IMPACT INFORMATION
The helicopter came to rest on its left side in a grassy area about 700 feet northwest of the runway 15 threshold at LNA. The wreckage path was oriented approximately 140 degrees magnetic, and extended about 75 feet from the initial impact point to where the fuselage came to rest. The initial impact point was identified as a large metal stake, about 3 feet in height. The second point of impact was a small crater measuring about 4 feet long and 1 foot deep, located about 15 feet past the initial impact point. A portion of the forward skid crosstube was located in the crater. The vertical stabilizer, horizontal stabilizer, and portion of the tail rotor came to rest next to the crater. The tail boom was separated from the fuselage, and fractured into several pieces, some of which displayed signatures consistent with main rotor blade contact. The skids separated from the fuselage and were fractured into several sections, which were located along the wreckage path.
The fuselage exhibited downward crushing, and the cabin was fractured aft of the seat structures. Both the auxiliary and main fuel tanks were intact and contained fuel, and both fuel caps were secure. The fuel vent tubes were separated from the auxiliary tank by impact, which allowed fuel to drain from the tanks following the accident.
The main rotor remained attached to the fuselage. One blade was bent up and displayed several chordwise creases along its span. The second blade was bent up about 45 degrees near its root. Neither blade displayed significant leading edge damage. The tail rotor drive shaft separated from the helicopter during the accident sequence, and a 5-foot portion was located about 500 feet west of the main wreckage. The aft portion of the tail rotor drive shaft was not recovered.
The helicopter was removed from the accident site and transported to a secure facility for further examination. Flight control continuity was confirmed from the cockpit area to the main rotor system. Tail rotor control continuity was established from the cockpit to the intermediate flex coupling. The main rotor gearbox rotated smoothly by hand with no anomalies observed. Examination of the v-belts, sheaves, and overrunning clutch also revealed no anomalies. Tail rotor drive continuity was established from the upper drive sheave to the intermediate flex coupling. The tail rotor gearbox rotated smoothly, with no anomalies noted.
The engine remained attached to the airframe at its mount. The mixture control wire was impact-separated from the mixture control arm. The carburetor heat control was bent, and was in the off position. The carburetor air box was partially crushed, and the carburetor heat slider valve was in a mid-travel, partially open position. The carburetor remained attached to the engine, and the throttle control arm was observed about 1/8 inch from the full-throttle position. The exhaust system was partially crushed. The sparkplugs were removed and displayed normal wear characteristics. The engine was rotated by hand at the cooling fan, and thumb compression was obtained on all cylinders. Crankshaft continuity was established to the accessory gears. Oil was added to the engine to facilitate a test run, and when power was applied to the engine starter, the engine started, accelerated, and ran continuously for several minutes utilizing the fuel onboard. A magneto check was performed with no anomalies noted.
The engine was shut down, and the carburetor, oil filter, and oil suction screen were removed for examination. The carburetor float bowl contained blue liquid consistent with 100LL aviation fuel, and did not display any sign of contamination. There was no damage to the internal components of the carburetor, and the fuel inlet screen was absent of debris.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy was performed on the CFI by the Office of the District Medical Examiner, District 15, Palm Beach County, Florida. The cause of death was identified as blunt force injuries. Toxicological testing was performed by the FAA Bioaeronautical Sciences Research Laboratory in Oklahoma City, Oklahoma. Testing was negative for carbon monoxide, ethanol, and all tested-for drugs and their metabolites.
ADDITIONAL INFORMATION
Cell Phone Information
The CFI's cell phone was retained for examination in the NTSB vehicle recorders laboratory; however, the device was passcode-protected and could not be unlocked. Usage records obtained from the cellular service provider could not conclusively determine whether the phone was in use at the time of the accident.
Practice Autorotations
According to the pilot training syllabus provided by the flight school, the objective of Stage 3, Lesson 2 was for the student to practice advanced maneuvers and procedures, including normal and steep approach, normal and maximum performance takeoff, hovering, hover taxi, air taxi, ground reference maneuvers, emergency operations, autorotation to a power recovery, loss of tail rotor, stuck pedal, hovering out of ground effect, and confined area operation.
Review of the student's training record indicated that he completed Stage 2 of the syllabus on December 23, 2014. Instructor notes for the previous flight, dated December 22, 2014, indicated, "gap in training is evident in proficiency, basic straight [and] level unsatisfactory, [aeronautical decision making] needs work, approaches need work."
The flight school specified that all 180-degree and straight-in autorotations be terminated with a power recovery throughout the private pilot training course. School policy also stated that landings and autorotations at LNA were performed to the runways or to the grassy areas next to runways 15/33 and 09/27.
The flight school's written procedures for a straight-in autorotation with power recovery indicated that the maneuver should be initiated at an altitude of 700 feet agl after clearing the area for potential traffic conflicts and applying carburetor heat. Upon selecting a landing site, the autorotation was entered by rolling the throttle to the full idle position, where the procedure specified it should be held "firmly against the stop for the remainder of the autorotation." About 40 feet agl, the recovery was initiated by applying aft cyclic to bring the helicopter to a skids-level attitude, where it was held for 3 seconds prior to entering a flare. At that time, the throttle was "crack[ed] open" to allow the rpm governor to operate, forward cyclic applied, and the collective raised to bring the helicopter to a hover about 5 feet agl. The maneuver guide also stated, "Make an IMMEDIATE power recovery if the following conditions do not exist through 100' AGL: Aircraft aligned with touchdown point; Rotor RPM in the green; Airspeed within +/- 5 [knots] of 65 [knots]; Rate of descent <1,500 fpm".
The manufacturer's Pilots Operating Handbook outlined the following procedure for a practice autorotation with a power recovery: "1. Adjust carb heat as required. 2. Lower collective to down stop and adjust throttle as required for small tachometer needle separation. CAUTION: To avoid inadvertent engine stoppage, do not chop throttle to simulate a power failure. Always roll throttle off smoothly for a small visible needle split. 3. Adjust collective to keep rotor RPM in green arc and adjust throttle for small needle separation. 4. Keep airspeed 60 to 70 KIAS. 5. At about 40 feet AGL, begin cyclic flare to reduce rate of descent and forward speed. 6. At about 8 feet AGL, apply forward cyclic to level aircraft and raise collective to control descent. Add throttle if required to keep RPM in green arc."
Robinson Helicopter Company Safety Notice SN-38, "Practice Autorotations Cause Many Training Accidents," stated, "There have been instances when the engine has quit during practice autorotation. To avoid inadvertent engine stoppage, do not roll throttle to full idle. Reduce throttle smoothly for a small visible needle split, then hold throttle firmly to override governor. Recover immediately if engine is rough or engine RPM continues to drop."
Safety Notice SN-24, "Low RPM Rotor Stall Can Be Fatal," stated, "Rotor stall is very similar to the stall of an airplane wings at low airspeeds. As the airspeed of an airplane gets lower…the angle of attack of the wing must be higher for the wing to produce the lift required to support the weight of the airplane…The same thing happens during rotor stall with a helicopter except it occurs due to low rotor RPM instead of low airspeed. As the RPM of the rotor gets lower, the angle of attack of the rotor blades must be higher to generate the lift required to support the weight of the helicopter…Even if the collective is not raised by the pilot to provide the higher blade angle, the helicopter will start to descend until the upward movement of air to the rotor provides the necessary increase in blade angle of attack…The increased drag on the blades acts like a huge rotor brake causing the rotor RPM to rapidly decrease, further increasing the rotor stall. As the helicopter begins to fall, the upward rushing air continues to increase the angle of attack on the slowly-rotating blades, making recovery virtually impossible, even with full down collective."
FAA publication P-8740-71, "Planning Autorotations,"was intended to raise flight instructor awareness to the hazards of training students in autorotations and provide guidelines and parameters for conducting practice autorotations. The pamphlet concluded, "The number one error in practice autorotations is the failure of the flight instructor to take control of the aircraft and terminate the maneuver before it progresses to a point where the flight instructor is not capable of recovering the aircraft in time to prevent damage to the aircraft or injury to personnel. REMEMBER: As a flight instructor, you are the most knowledgeable and experienced person in that helicopter. Do not let your student fly the helicopter into some corner of its performance envelope where it is not recoverable."
14 CFR Part 91: General Aviation
Accident occurred Monday, December 29, 2014 in Lake Worth, FL
Aircraft: ROBINSON HELICOPTER R22 BETA, registration: N771MM
Injuries: 1 Fatal, 1 Serious.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
On December 29, 2014, at 1025 eastern standard time, a Robinson R22 Beta, N771MM, was substantially damaged when it impacted terrain while maneuvering for landing at Palm Beach County Park Airport (LNA), Lake Worth, Florida. The certificated flight instructor (CFI) was fatally injured, and the student pilot sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which departed about 0940. The flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.
In a statement to law enforcement, the student pilot recounted that he and the CFI were practicing emergency procedures following a simulated engine failure. The student pilot said that he entered an autorotation after the throttle was reduced to idle, and the helicopter was in an autorotational descent when the accident occurred. He could not completely recall the sequence of events leading up to the accident, but stated that as the helicopter descended through 100 feet, he remembered the CFI saying, "we're going down."
Another CFI, who was taxiing a helicopter with a student on the south side of LNA, reported hearing the accident helicopter transmit, "we're going in the grass" over the airport's common traffic advisory frequency. Shortly thereafter, an airplane in the airport traffic pattern reported that there was a helicopter down, and the CFI flew to the accident site to render assistance.
The helicopter came to rest on its left side in a grassy area about 700 feet northwest of the runway 15 threshold at LNA. The wreckage path was oriented approximately 140 degrees magnetic, and extended about 75 feet from the initial impact point to where the fuselage came to rest. The initial impact point was identified as a large metal stake, about 3 feet in height. The second point of impact was a small crater measuring about 4 feet long and 1 foot deep, located about 15 feet past the initial impact point. A portion of the forward skid crosstube was located in the crater. The vertical stabilizer, horizontal stabilizer, and portion of the tail rotor came to rest next to the crater. The tail boom was separated from the fuselage, and fractured into several pieces, some of which displayed signatures consistent with main rotor blade contact. The skids separated from the fuselage and were fractured into several sections, which were located along the wreckage path.
The fuselage exhibited downward crushing, and the cabin was fractured aft of the seat structures. Both the auxiliary and main fuel tanks were intact and contained fuel, and both fuel caps were secure. The fuel vent tubes were separated from the auxiliary tank by impact, which allowed fuel to drain from the tanks following the accident.
The main rotor remained attached to the fuselage. One blade was bent up and displayed several chordwise creases along its span. The second blade was bent up about 45 degrees near its root. Neither blade displayed significant leading edge damage. The tail rotor drive shaft separated from the helicopter during the accident sequence, and a 5-foot portion was located about 500 feet west of the main wreckage. The aft portion of the tail rotor drive shaft was not recovered.
The helicopter was removed from the accident site and transported to a salvage facility for further examination. Flight control continuity was confirmed from the cockpit area to the main rotor system. Tail rotor control continuity was established from the cockpit to the intermediate flex coupling. The main rotor gearbox rotated smoothly by hand with no anomalies observed. Examination of the v-belts, sheaves, and overrunning clutch also revealed no anomalies.
Tail rotor drive continuity was established from the upper drive sheave to the intermediate flex coupling. The tail rotor gearbox rotated smoothly, with no anomalies noted. Power was applied to the engine starter, and utilizing the fuel onboard, the engine started, accelerated smoothly, and ran continuously for several minutes with no anomalies noted.
Jonathan Desouza, 25, a student pilot, said his instructor, Luis Aviles, 34, of West Palm Beach, was doing an emergency procedure simulation for engine failure when their aircraft crashed, killing Aviles and severely injuring Desouza.
"I guess when we went to bring the motor back on, the motor just didn't start back up," Desouza told Sun Sentinel news partner WPEC-Ch. 12 on Tuesday.
Preliminary information indicated the pilots possibly were practicing the procedure when the Robinson R-22 helicopter crashed at 10:20 a.m. Monday at John Prince Park, said Allison Diaz, a National Transportation Safety Board air safety investigator who is leading the inquiry.
The safety board said it could take a year to complete the comprehensive investigation.
"We'll be investigating things such as the pilot's training record, medical history, the helicopter's maintenance history, and environmental factors such as weather," Diaz said.
Desouza said his instructor had control of the helicopter when the aircraft went down. He said the last thing he remembers is Aviles telling him they were going to crash.
"Three seconds later we hit the ground," he said. "And I pretty much blacked out."
He said he doesn't remember anything after the crash, and when he came to, he was in the back of a medical helicopter heading for Delray Medical Center.
According to Federal Aviation Administration records, Aviles was a certified helicopter flight instructor. He also had an instrument rating, a commercial pilot's license and a helicopter mechanic license.
Records for Desouza were unavailable because he is a student pilot.
Desouza's neighbor, Conroy Casella, 57, said several neighbors know him through Desouza's pressure cleaning service. "He does well at it," Casella said. "He's a great kid. God, I hope he pulls through."
The NTSB said Palm Beach Helicopters owned the helicopter, according to WPEC-Ch. 12. Aviles is listed as an employee of the business, according to its website.
Aviles' biography on the company's website said he served in the U.S. Marine Corps before he started teaching flight instruction. He moved from New Jersey to Palm Beach County in 2012 and obtained an aeronautical sciences degree from Palm Beach State College, according to the website.
Palm Beach Helicopters' president could not be reached for comment despite phone calls.
At about 11:30 a.m. Tuesday, the helicopter was moved to an aircraft salvage facility in Fort Pierce, as part of the investigation.
Before that, representatives from the Federal Aviation Administration, the helicopter manufacturer and engine manufacturer met Tuesday morning at the crash site to gather information that would have otherwise been lost when the helicopter was relocated.
A preliminary report from the NTSB is expected in about 10 business days, but a more-detailed factual report is expected to be released in about 12 months. About 60 days after that, investigators should have a probable cause for the crash, Diaz said.
An FAA spokeswoman told Ch. 12 the helicopter that crashed had no prior accidents or incidents.
According to FAA records, the helicopter is registered to LLB Enterprises Group Inc., out of Fort White, Fla. Robinson Helicopters said on its website the R-22 seats two, and was used for a number of operations, including flight training and livestock mustering.
http://www.sun-sentinel.com
Two pilots may have been practicing an emergency procedure during a routine training flight when the helicopter they were in crashed north of the Lantana Airport, killing one and seriously injuring the other, federal officials said Tuesday.
Preliminary information indicates the pilots possibly were practicing the procedure when the Robinson R-22 helicopter crashed at 10:20 a.m. Monday at John Prince Park, said Allison Diaz, a National Transportation Safety Board air safety investigator who is leading the inquiry.
It's among the possibilities being considered in the crash that killed flight instructor Luis Aviles, 34, of West Palm Beach, and injured student pilot Jonathan Desouza, 25, of Boynton Beach.
Investigators don't know who was piloting the helicopter during the crash, but said they hope to talk with Desouza, who was hospitalized. Talking to him should "shed some light on what was going on at the time of the accident," Diaz said.
The National Transportation Safety Board said it could take a year to complete the comprehensive investigation.
"We'll be investigating things such as the pilot's training record, medical history, the helicopter's maintenance history, and environmental factors such as weather," Diaz said.
According to Federal Aviation Administration records, Aviles was a certified helicopter flight instructor. He also had an instrument rating, a commercial pilot's license and a helicopter mechanic license.
Records for Desouza were unavailable because he is a student pilot.
Desouza's neighbor, Conroy Casella, 57, said several neighbors know Desouza through Desouza's business, "The Pressure King," a pressure cleaning service. "He does well at it," Casella said. "He's a great kid. God, I hope he pulls through."
Casella was surprised to learn his neighbor was on the helicopter. "I had no idea it was him," Casella said Tuesday.
At about 11:30 a.m. Tuesday, the helicopter was moved to an aircraft salvage facility in Fort Pierce, as the investigation continued.
Before that, representatives from the Federal Aviation Administration, the helicopter manufacturer and engine manufacturer met Tuesday morning at the crash site to gather information that would have otherwise been lost when the helicopter was relocated.
A preliminary report from the NTSB is expected in about 10 business days, but a more-detailed factual report is expected to be released in about 12 months. About 60 days after that, investigators should have a probable cause for the crash, Diaz said.
The NTSB said Palm Beach Helicopters owned the helicopter, according to WPEC-Ch. 12. Aviles is listed as an employee of the business, according to its website.
A photo from the Facebook page of Palm Beach Helicopters shows the exact helicopter that crashed and a man identified as Luis Aviles standing in front of it, Ch. 12 reported.
Palm Beach Helicopters' vice president could not be reached for comment despite phone calls.
An FAA spokeswoman told Ch. 12 the helicopter that crashed had no prior accidents or incidents.
According to FAA records, the helicopter is registered to LLB Enterprises Group Inc., out of Fort White, Fla. Robinson Helicopters said on its website the R-22 seats two, and is used for a number of operations, including flight training and livestock mustering. Robinson Helicopters couldn't be reached for comment despite a phone call, Ch. 12 said.
http://www.sun-sentinel.com
Witnesses say they heard a Robinson R22 helicopter "sputter" before crashing Monday near Lantana Airport.
The helicopter crashed about 100 yards from the airport in John Prince Park. One person onboard was killed, and another was in critical condition after the crash that happened just before 10:30 a.m. according to authorities.
"I saw the helicopter inverted and I knew something was wrong. It was sputtering," witness Charles Ketchel said. Ketchel, along with other witnesses, was staying at the John Prince Park campground.
"I knew what it was because I am familiar with helicopters...I used to fly in the Army and all I know is when I heard the noise and it hitting the trees, I knew something was not right," Jerry Campbell said.
The Federal Aviation Administration is on scene and the National Transportation Safety Board will have an investigator on the scene Tuesday morning. Staff at Palm Beach Helicopters confirm it was one of their helicopters that went down in the crash. They didn't say, though, who was involved in the incident.
The flight training school is known by aviation enthusiasts around the country. Those in the local aviation community say they're part of a close knit group, and are anxious to find out who was involved in the crash.
"The aviation community here at Lantana is a close-knit community of friends, family, colleagues, coworkers. You don't go a couple weeks without learning someone's name or knowing someone by their face," says Nikolas Markis.
Markis is training to be a pilot, and is familiar with Palm Beach Helicopters. He says students travel from around the country to get flight training at the school.
Markis says he's not afraid to fly again after this incident, but says there are always some concerns when you go in the air. "Just like having a friend or family member go for a drive and not come back, you do have that in the back of your mind every time you go up. That could be you," he says.
The Palm Beach County Sheriff's Office has not released the victims' names pending family notification.
Investigators are still at the scene of a fatal helicopter crash Monday morning just north of Lantana airport.
One person was killed and another critically injured after the crash that occurred in John Prince Park, less than 100 yards north of Palm Beach County Park Airport, just north of Lantana Road and west of Interstate 95.
By early afternoon, the body of the deceased remained covered in a yellow tarp in the helicopter, which was in pieces in an area of the park that appears to be a maintenance area with buildings, barrels, trucks and tractors.
The area is separated from the airport by a small creek.
The blade of the helicopter was bent and cracked but still attached.
Police tape surrounds the crash area.
It doesn’t appear that the helicopter was damaged by fire.
Authorities said the helicopter was carrying two people when it crashed about 10:30 a.m.
The injured person was flown by Trauma Hawk to an area hospital.
Story and Video: http://www.palmbeachpost.com NTSB Identification: ERA15FA085
14 CFR Part 91: General Aviation
Accident occurred Monday, December 29, 2014 in Lake Worth, FL
Probable Cause Approval Date: 03/06/2017
Aircraft: ROBINSON HELICOPTER R22 BETA, registration: N771MM
Injuries: 1 Fatal, 1 Serious.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The purpose of the instructional helicopter flight was to review advanced maneuvers in preparation for the student pilot’s upcoming stage check. The student stated that he and the flight instructor had conducted 3 approaches and landings before initiating a practice autorotation. He stated that as the helicopter descended through 100 ft in the autorotation, the instructor applied throttle in an attempt to recover, but the engine did not respond. A witness stated that, about halfway through the helicopter’s autorotative descent, it appeared to momentarily level off before abruptly entering a nose-down attitude and descending to ground contact. A surveillance video showed the helicopter descending rapidly at a steep angle in the last 2 seconds before impact. The helicopter impacted terrain about 700 ft north of the runway threshold, fatally injuring the instructor and seriously injuring the student. Postaccident examination of the helicopter and a test run of the engine revealed no mechanical anomalies that would have precluded normal operation.
The flight school’s published procedure for practice autorotations instructed the pilot to initiate the maneuver first by lowering the collective, then reducing the throttle to idle. The practice of reducing the throttle to idle was contrary to manufacturer guidance for this maneuver, which stated that the throttle should be adjusted only enough to allow for a small tachometer needle separation in order to reduce the chance of inadvertent engine stoppage during the maneuver. The practice of reducing throttle to idle introduced greater susceptibility to a loss of engine power, though it could not be determined whether a loss of power occurred before the accident.
Based on conflicting statements from the student, it could not be determined who was controlling the helicopter during the entry into and throughout the autorotation before about 100 ft. The helicopter’s trajectory described by a witness and as captured on surveillance video suggested a rapid, uncontrolled descent during the final portion of the autorotation, consistent with a main rotor stall; likely as a result of a premature application of collective pitch. This allowed the rotor rpm to decay below the normal operating range at an altitude that was insufficient for power recovery. In the event that the helicopter did experience a loss of power during the maneuver, the helicopter should have been able to attain a safe landing following a steady-state autorotation. The helicopter manufacturer published notices to pilots warning that main rotor stall due to low rotor rpm could occur rapidly, at any airspeed, and that if allowed to develop, recovery could become “virtually impossible.”
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
A main rotor stall due to low rotor rpm, which resulted in an uncontrolled descent into terrain. Contributing to the accident was the flight instructor’s delayed remedial action.
The NTSB traveled to the scene of this accident.
Docket And Docket Items: https://dms.ntsb.gov/pubdms
NTSB Identification: ERA15FA085
14 CFR Part 91: General Aviation
Accident occurred Monday, December 29, 2014 in Lake Worth, FL
Aircraft: ROBINSON HELICOPTER R22 BETA, registration: N771MM
Injuries: 1 Fatal, 1 Serious.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
***This report was modified on January 25, 2017. Please see the public docket for this accident to view the original report.***
HISTORY OF FLIGHT
On December 29, 2014, at 1025 eastern standard time, a Robinson R22 Beta, N771MM, was substantially damaged when it impacted terrain while performing an autorotation near Palm Beach County Park Airport (LNA), Lake Worth, Florida. The flight instructor (CFI) was fatally injured, and the student pilot sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which departed about 0940. The flight was operated by Palm Beach Helicopters, Inc., and was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.
A witness, who was a CFI, reported that he and a student were taxiing their airplane to runway 15 for takeoff when they heard the accident helicopter announce its position on a right base leg, with the intent to conduct an autorotation to taxiway Bravo. The CFI then offered to hold at the airplane's present position to allow the helicopter more room to conduct the maneuver. He stated that the helicopter pilot thanked him, and shortly thereafter, he observed the helicopter enter a "rapid descent typical of [autorotation]" from an altitude of between 800-1,000 feet above ground level (agl). About 500 feet agl, the helicopter appeared to level off, then pitched abruptly nose-down and descended to ground contact. Just prior to impact, he heard a panicked radio transmission from the helicopter that was mostly unintelligible. He also stated that, based on the accent he heard, he believed the CFI onboard the helicopter was conducting all radio transmissions.
Another CFI, who was taxiing a helicopter with a student on the south side of the airport, reported hearing the accident helicopter transmit, "we're going in the grass" over the airport's common traffic advisory frequency. Shortly thereafter, an airplane in the airport traffic pattern reported that there was a helicopter down, and the CFI in the helicopter flew to the accident site to render assistance.
In a statement to law enforcement two days after the accident, the student pilot recounted that he and the CFI were practicing autorotations following a simulated engine failure. The student stated that he could not recall whether he or the CFI initiated the autorotation. About 100 feet above ground level, the CFI said, "We're going down, we're going down," and at that time, the CFI was controlling the helicopter. The student stated that, until that point, the autorotation had "appeared pretty normal," and he added, "I don't know if the engine cut off, or the engine didn't turn back on."
In a subsequent interview, conducted about two weeks after the accident, the student stated that the flight was Lesson 2 in Stage 3 of the school's private pilot training course. He reported that he could not recall most of the accident flight, but recalled that prior to the accident, he and the CFI had been flying for approximately 40 minutes and had conducted 2 or 3 steep approaches as well as a maximum-performance takeoff. The accident autorotation was the first of the accident flight. He stated that he could not recall who initiated the autorotation or the rotor rpm indication during the maneuver. He remembered that the CFI was controlling the helicopter as it descended through about 100 feet above ground level, and as the CFI rolled on the throttle in an attempt to recover, there was no response from the engine. The CFI stated, "We're going down, we're going down." The student also stated that, on the downwind leg of the traffic pattern, he observed the CFI using his cell phone and stated that he appeared to be conducting a video call, as he briefly saw someone on the phone's screen. He stated that the CFI turned the phone to face outside of the helicopter as if he was showing the view out the helicopter's windscreen to the individual on the phone. He could not recall when the CFI discontinued the use of the phone.
In a written statement provided after the interview, the student recalled that the CFI "asked for the controls," on the downwind leg of the traffic pattern prior to entering the autorotation. The student stated that he "handed over the controls and looked south out my door enjoying the view." The student then recalled looking at the ground "in a nose down attitude" as the helicopter descended, and seeing the CFI "fighting with the cyclic and collective."
Surveillance video from a building near the accident site captured approximately the last 2 seconds of the flight before impact, and showed the helicopter descending rapidly at a steep angle.
PERSONNEL INFORMATION
The CFI held commercial pilot and flight instructor certificates, both with ratings for rotorcraft-helicopter and instrument helicopter; as well as an airframe and powerplant mechanic certificate. His most recent Federal Aviation Administration (FAA) first-class medical certificate was issued in March 2014. Review of operator records revealed the CFI had about 397 total hours of flight experience, of which about 280 hours were in the accident helicopter make and model. He had accumulated about 121 hours of flight instruction given.
The student held an FAA second-class medical and student pilot certificate, which was issued in December 2012. He reported about 37 total hours of flight time, all of which was in the accident helicopter make and model.
AIRCRAFT INFORMATION
The helicopter was manufactured in 1996 and was equipped with one Lycoming O-360 series, 145 hp reciprocating engine. Review of maintenance records provided by the operator indicated that the helicopter's most recent 100-hour inspection was completed on December 1, 2014. At that time, the airframe had accumulated a total time of 4,162.9 hours, and the engine had accumulated 1,978.7 hours since its most recent overhaul. The helicopter's 2,200-hour inspection was completed on February 13, 2013 at a total airframe time of 2,184.2 hours.
METEOROLOGICAL INFORMATION
The 0953 automated weather observation at PBI recorded wind from 180 degrees at 7 knots, 10 miles visibility, scattered clouds at 2,100 ft, temperature 26 degrees C, dew point 22 degrees C, and an altimeter setting of 30.13 inches of mercury. Review of a carburetor icing probability chart revealed the potential for serious carburetor icing at glide power.
WRECKAGE AND IMPACT INFORMATION
The helicopter came to rest on its left side in a grassy area about 700 feet northwest of the runway 15 threshold at LNA. The wreckage path was oriented approximately 140 degrees magnetic, and extended about 75 feet from the initial impact point to where the fuselage came to rest. The initial impact point was identified as a large metal stake, about 3 feet in height. The second point of impact was a small crater measuring about 4 feet long and 1 foot deep, located about 15 feet past the initial impact point. A portion of the forward skid crosstube was located in the crater. The vertical stabilizer, horizontal stabilizer, and portion of the tail rotor came to rest next to the crater. The tail boom was separated from the fuselage, and fractured into several pieces, some of which displayed signatures consistent with main rotor blade contact. The skids separated from the fuselage and were fractured into several sections, which were located along the wreckage path.
The fuselage exhibited downward crushing, and the cabin was fractured aft of the seat structures. Both the auxiliary and main fuel tanks were intact and contained fuel, and both fuel caps were secure. The fuel vent tubes were separated from the auxiliary tank by impact, which allowed fuel to drain from the tanks following the accident.
The main rotor remained attached to the fuselage. One blade was bent up and displayed several chordwise creases along its span. The second blade was bent up about 45 degrees near its root. Neither blade displayed significant leading edge damage. The tail rotor drive shaft separated from the helicopter during the accident sequence, and a 5-foot portion was located about 500 feet west of the main wreckage. The aft portion of the tail rotor drive shaft was not recovered.
The helicopter was removed from the accident site and transported to a secure facility for further examination. Flight control continuity was confirmed from the cockpit area to the main rotor system. Tail rotor control continuity was established from the cockpit to the intermediate flex coupling. The main rotor gearbox rotated smoothly by hand with no anomalies observed. Examination of the v-belts, sheaves, and overrunning clutch also revealed no anomalies. Tail rotor drive continuity was established from the upper drive sheave to the intermediate flex coupling. The tail rotor gearbox rotated smoothly, with no anomalies noted.
The engine remained attached to the airframe at its mount. The mixture control wire was impact-separated from the mixture control arm. The carburetor heat control was bent, and was in the off position. The carburetor air box was partially crushed, and the carburetor heat slider valve was in a mid-travel, partially open position. The carburetor remained attached to the engine, and the throttle control arm was observed about 1/8 inch from the full-throttle position. The exhaust system was partially crushed. The sparkplugs were removed and displayed normal wear characteristics. The engine was rotated by hand at the cooling fan, and thumb compression was obtained on all cylinders. Crankshaft continuity was established to the accessory gears. Oil was added to the engine to facilitate a test run, and when power was applied to the engine starter, the engine started, accelerated, and ran continuously for several minutes utilizing the fuel onboard. A magneto check was performed with no anomalies noted.
The engine was shut down, and the carburetor, oil filter, and oil suction screen were removed for examination. The carburetor float bowl contained blue liquid consistent with 100LL aviation fuel, and did not display any sign of contamination. There was no damage to the internal components of the carburetor, and the fuel inlet screen was absent of debris.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy was performed on the CFI by the Office of the District Medical Examiner, District 15, Palm Beach County, Florida. The cause of death was identified as blunt force injuries. Toxicological testing was performed by the FAA Bioaeronautical Sciences Research Laboratory in Oklahoma City, Oklahoma. Testing was negative for carbon monoxide, ethanol, and all tested-for drugs and their metabolites.
ADDITIONAL INFORMATION
Cell Phone Information
The CFI's cell phone was retained for examination in the NTSB vehicle recorders laboratory; however, the device was passcode-protected and could not be unlocked. Usage records obtained from the cellular service provider could not conclusively determine whether the phone was in use at the time of the accident.
Practice Autorotations
According to the pilot training syllabus provided by the flight school, the objective of Stage 3, Lesson 2 was for the student to practice advanced maneuvers and procedures, including normal and steep approach, normal and maximum performance takeoff, hovering, hover taxi, air taxi, ground reference maneuvers, emergency operations, autorotation to a power recovery, loss of tail rotor, stuck pedal, hovering out of ground effect, and confined area operation.
Review of the student's training record indicated that he completed Stage 2 of the syllabus on December 23, 2014. Instructor notes for the previous flight, dated December 22, 2014, indicated, "gap in training is evident in proficiency, basic straight [and] level unsatisfactory, [aeronautical decision making] needs work, approaches need work."
The flight school specified that all 180-degree and straight-in autorotations be terminated with a power recovery throughout the private pilot training course. School policy stated that all landings and practice autorotations were to be performed to a hard-surfaced runway or taxiway.
The flight school's written procedures for a straight-in autorotation with power recovery indicated that the maneuver should be initiated at an altitude of 700 feet agl after clearing the area for potential traffic conflicts and applying carburetor heat. Upon selecting a landing site, the autorotation was entered by lowering the collective to its full-down position, then rolling the throttle to the full idle position, where the procedure specified it should be held "firmly against the stop for the remainder of the autorotation." About 40 feet agl, the recovery was initiated by applying aft cyclic to bring the helicopter to a skids-level attitude, where it was held for 3 seconds prior to entering a flare. At that time, the throttle was "crack[ed] open" to allow the rpm governor to operate, forward cyclic applied, and the collective raised to bring the helicopter to a hover about 5 feet agl. The maneuver guide also stated, "Make an IMMEDIATE power recovery if the following conditions do not exist through 100' AGL: Aircraft aligned with touchdown point; Rotor RPM in the green; Airspeed within +/- 5 [knots] of 65 [knots]; Rate of descent <1,500 fpm".
The manufacturer's Pilots Operating Handbook outlined the following procedure for a practice autorotation with a power recovery: "1. Adjust carb heat as required. 2. Lower collective to down stop and adjust throttle as required for small tachometer needle separation. CAUTION: To avoid inadvertent engine stoppage, do not chop throttle to simulate a power failure. Always roll throttle off smoothly for a small visible needle split. 3. Adjust collective to keep rotor RPM in green arc and adjust throttle for small needle separation. 4. Keep airspeed 60 to 70 KIAS. 5. At about 40 feet AGL, begin cyclic flare to reduce rate of descent and forward speed. 6. At about 8 feet AGL, apply forward cyclic to level aircraft and raise collective to control descent. Add throttle if required to keep RPM in green arc."
Robinson Helicopter Company Safety Notice SN-38, "Practice Autorotations Cause Many Training Accidents," stated, "There have been instances when the engine has quit during practice autorotation. To avoid inadvertent engine stoppage, do not roll throttle to full idle. Reduce throttle smoothly for a small visible needle split, then hold throttle firmly to override governor. Recover immediately if engine is rough or engine RPM continues to drop."
Safety Notice SN-24, "Low RPM Rotor Stall Can Be Fatal," stated, "Rotor stall is very similar to the stall of an airplane wings at low airspeeds. As the airspeed of an airplane gets lower…the angle of attack of the wing must be higher for the wing to produce the lift required to support the weight of the airplane…The same thing happens during rotor stall with a helicopter except it occurs due to low rotor RPM instead of low airspeed. As the RPM of the rotor gets lower, the angle of attack of the rotor blades must be higher to generate the lift required to support the weight of the helicopter…Even if the collective is not raised by the pilot to provide the higher blade angle, the helicopter will start to descend until the upward movement of air to the rotor provides the necessary increase in blade angle of attack…The increased drag on the blades acts like a huge rotor brake causing the rotor RPM to rapidly decrease, further increasing the rotor stall. As the helicopter begins to fall, the upward rushing air continues to increase the angle of attack on the slowly-rotating blades, making recovery virtually impossible, even with full down collective."
FAA publication P-8740-71, "Planning Autorotations,"was intended to raise flight instructor awareness to the hazards of training students in autorotations and provide guidelines and parameters for conducting practice autorotations. The pamphlet concluded, "The number one error in practice autorotations is the failure of the flight instructor to take control of the aircraft and terminate the maneuver before it progresses to a point where the flight instructor is not capable of recovering the aircraft in time to prevent damage to the aircraft or injury to personnel. REMEMBER: As a flight instructor, you are the most knowledgeable and experienced person in that helicopter. Do not let your student fly the helicopter into some corner of its performance envelope where it is not recoverable."
Luis Aviles and Jonathan Desouza
~
FAA Flight Standards District Office: FAA Miami FSDO-19
NTSB Identification: ERA15FA085
14 CFR Part 91: General Aviation
Accident occurred Monday, December 29, 2014 in Lake Worth, FL
Aircraft: ROBINSON HELICOPTER R22 BETA, registration: N771MM
Injuries: 1 Fatal, 1 Serious.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
HISTORY OF FLIGHT
On December 29, 2014, at 1025 eastern standard time, a Robinson R22 Beta, N771MM, was substantially damaged when it impacted terrain while performing an autorotation near Palm Beach County Park Airport (LNA), Lake Worth, Florida. The flight instructor (CFI) was fatally injured, and the student pilot sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which departed about 0940. The flight was operated by Palm Beach Helicopters, Inc., and was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.
A witness, who was a CFI, reported that he and a student were taxiing their airplane to runway 15 for takeoff when they heard the accident helicopter announce its position on a right base leg, with the intent to conduct an autorotation to taxiway Bravo. The CFI then offered to hold at the airplane's present position to allow the helicopter more room to conduct the maneuver. He stated that the helicopter pilot thanked him, and shortly thereafter, he observed the helicopter enter a "rapid descent typical of [autorotation]" from an altitude of between 800-1,000 feet above ground level (agl). About 500 feet agl, the helicopter appeared to level off, then pitched abruptly nose-down and descended to ground contact. Just prior to impact, he heard a panicked radio transmission from the helicopter that was mostly unintelligible. He also stated that, based on the accent he heard, he believed the CFI onboard the helicopter was conducting all radio transmissions.
Another CFI, who was taxiing a helicopter with a student on the south side of the airport, reported hearing the accident helicopter transmit, "we're going in the grass" over the airport's common traffic advisory frequency. Shortly thereafter, an airplane in the airport traffic pattern reported that there was a helicopter down, and the CFI in the helicopter flew to the accident site to render assistance.
In a statement to law enforcement two days after the accident, the student pilot recounted that he and the CFI were practicing autorotations following a simulated engine failure. The student stated that he could not recall whether he or the CFI initiated the autorotation. About 100 feet above ground level, the CFI said, "We're going down, we're going down," and at that time, the CFI was controlling the helicopter. The student stated that, until that point, the autorotation had "appeared pretty normal," and he added, "I don't know if the engine cut off, or the engine didn't turn back on."
In a subsequent interview, conducted about two weeks after the accident, the student stated that the flight was Lesson 2 in Stage 3 of the school's private pilot training course. He reported that he could not recall most of the accident flight, but recalled that prior to the accident, he and the CFI had been flying for approximately 40 minutes and had conducted 2 or 3 steep approaches as well as a maximum-performance takeoff. The accident autorotation was the first of the accident flight. He stated that he could not recall who initiated the autorotation or the rotor rpm indication during the maneuver. He remembered that the CFI was controlling the helicopter as it descended through about 100 feet above ground level, and as the CFI rolled on the throttle in an attempt to recover, there was no response from the engine. The CFI stated, "We're going down, we're going down." The student also stated that, on the downwind leg of the traffic pattern, he observed the CFI using his cell phone and stated that he appeared to be conducting a video call, as he briefly saw someone on the phone's screen. He stated that the CFI turned the phone to face outside of the helicopter as if he was showing the view out the helicopter's windscreen to the individual on the phone. He could not recall when the CFI discontinued the use of the phone.
In a written statement provided after the interview, the student recalled that the CFI "asked for the controls," on the downwind leg of the traffic pattern prior to entering the autorotation. The student stated that he "handed over the controls and looked south out my door enjoying the view." The student then recalled looking at the ground "in a nose down attitude" as the helicopter descended, and seeing the CFI "fighting with the cyclic and collective."
Surveillance video from a building near the accident site captured approximately the last 2 seconds of the flight before impact, and showed the helicopter descending rapidly at a steep angle.
PERSONNEL INFORMATION
The CFI held commercial pilot and flight instructor certificates, both with ratings for rotorcraft-helicopter and instrument helicopter; as well as an airframe and powerplant mechanic certificate. His most recent Federal Aviation Administration (FAA) first-class medical certificate was issued in March 2014. Review of operator records revealed the CFI had about 397 total hours of flight experience, of which about 280 hours were in the accident helicopter make and model. He had accumulated about 121 hours of flight instruction given.
The student held an FAA second-class medical and student pilot certificate, which was issued in December 2012. He reported about 37 total hours of flight time, all of which was in the accident helicopter make and model.
AIRCRAFT INFORMATION
The helicopter was manufactured in 1996 and was equipped with one Lycoming O-360 series, 145 hp reciprocating engine. Review of maintenance records provided by the operator indicated that the helicopter's most recent 100-hour inspection was completed on December 1, 2014. At that time, the airframe had accumulated a total time of 4,162.9 hours, and the engine had accumulated 1,978.7 hours since its most recent overhaul. The helicopter's 2,200-hour inspection was completed on February 13, 2013 at a total airframe time of 2,184.2 hours.
METEOROLOGICAL INFORMATION
The 0953 automated weather observation at PBI recorded wind from 180 degrees at 7 knots, 10 miles visibility, scattered clouds at 2,100 ft, temperature 26 degrees C, dew point 22 degrees C, and an altimeter setting of 30.13 inches of mercury. Review of a carburetor icing probability chart revealed the potential for serious carburetor icing at glide power.
WRECKAGE AND IMPACT INFORMATION
The helicopter came to rest on its left side in a grassy area about 700 feet northwest of the runway 15 threshold at LNA. The wreckage path was oriented approximately 140 degrees magnetic, and extended about 75 feet from the initial impact point to where the fuselage came to rest. The initial impact point was identified as a large metal stake, about 3 feet in height. The second point of impact was a small crater measuring about 4 feet long and 1 foot deep, located about 15 feet past the initial impact point. A portion of the forward skid crosstube was located in the crater. The vertical stabilizer, horizontal stabilizer, and portion of the tail rotor came to rest next to the crater. The tail boom was separated from the fuselage, and fractured into several pieces, some of which displayed signatures consistent with main rotor blade contact. The skids separated from the fuselage and were fractured into several sections, which were located along the wreckage path.
The fuselage exhibited downward crushing, and the cabin was fractured aft of the seat structures. Both the auxiliary and main fuel tanks were intact and contained fuel, and both fuel caps were secure. The fuel vent tubes were separated from the auxiliary tank by impact, which allowed fuel to drain from the tanks following the accident.
The main rotor remained attached to the fuselage. One blade was bent up and displayed several chordwise creases along its span. The second blade was bent up about 45 degrees near its root. Neither blade displayed significant leading edge damage. The tail rotor drive shaft separated from the helicopter during the accident sequence, and a 5-foot portion was located about 500 feet west of the main wreckage. The aft portion of the tail rotor drive shaft was not recovered.
The helicopter was removed from the accident site and transported to a secure facility for further examination. Flight control continuity was confirmed from the cockpit area to the main rotor system. Tail rotor control continuity was established from the cockpit to the intermediate flex coupling. The main rotor gearbox rotated smoothly by hand with no anomalies observed. Examination of the v-belts, sheaves, and overrunning clutch also revealed no anomalies. Tail rotor drive continuity was established from the upper drive sheave to the intermediate flex coupling. The tail rotor gearbox rotated smoothly, with no anomalies noted.
The engine remained attached to the airframe at its mount. The mixture control wire was impact-separated from the mixture control arm. The carburetor heat control was bent, and was in the off position. The carburetor air box was partially crushed, and the carburetor heat slider valve was in a mid-travel, partially open position. The carburetor remained attached to the engine, and the throttle control arm was observed about 1/8 inch from the full-throttle position. The exhaust system was partially crushed. The sparkplugs were removed and displayed normal wear characteristics. The engine was rotated by hand at the cooling fan, and thumb compression was obtained on all cylinders. Crankshaft continuity was established to the accessory gears. Oil was added to the engine to facilitate a test run, and when power was applied to the engine starter, the engine started, accelerated, and ran continuously for several minutes utilizing the fuel onboard. A magneto check was performed with no anomalies noted.
The engine was shut down, and the carburetor, oil filter, and oil suction screen were removed for examination. The carburetor float bowl contained blue liquid consistent with 100LL aviation fuel, and did not display any sign of contamination. There was no damage to the internal components of the carburetor, and the fuel inlet screen was absent of debris.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy was performed on the CFI by the Office of the District Medical Examiner, District 15, Palm Beach County, Florida. The cause of death was identified as blunt force injuries. Toxicological testing was performed by the FAA Bioaeronautical Sciences Research Laboratory in Oklahoma City, Oklahoma. Testing was negative for carbon monoxide, ethanol, and all tested-for drugs and their metabolites.
ADDITIONAL INFORMATION
Cell Phone Information
The CFI's cell phone was retained for examination in the NTSB vehicle recorders laboratory; however, the device was passcode-protected and could not be unlocked. Usage records obtained from the cellular service provider could not conclusively determine whether the phone was in use at the time of the accident.
Practice Autorotations
According to the pilot training syllabus provided by the flight school, the objective of Stage 3, Lesson 2 was for the student to practice advanced maneuvers and procedures, including normal and steep approach, normal and maximum performance takeoff, hovering, hover taxi, air taxi, ground reference maneuvers, emergency operations, autorotation to a power recovery, loss of tail rotor, stuck pedal, hovering out of ground effect, and confined area operation.
Review of the student's training record indicated that he completed Stage 2 of the syllabus on December 23, 2014. Instructor notes for the previous flight, dated December 22, 2014, indicated, "gap in training is evident in proficiency, basic straight [and] level unsatisfactory, [aeronautical decision making] needs work, approaches need work."
The flight school specified that all 180-degree and straight-in autorotations be terminated with a power recovery throughout the private pilot training course. School policy also stated that landings and autorotations at LNA were performed to the runways or to the grassy areas next to runways 15/33 and 09/27.
The flight school's written procedures for a straight-in autorotation with power recovery indicated that the maneuver should be initiated at an altitude of 700 feet agl after clearing the area for potential traffic conflicts and applying carburetor heat. Upon selecting a landing site, the autorotation was entered by rolling the throttle to the full idle position, where the procedure specified it should be held "firmly against the stop for the remainder of the autorotation." About 40 feet agl, the recovery was initiated by applying aft cyclic to bring the helicopter to a skids-level attitude, where it was held for 3 seconds prior to entering a flare. At that time, the throttle was "crack[ed] open" to allow the rpm governor to operate, forward cyclic applied, and the collective raised to bring the helicopter to a hover about 5 feet agl. The maneuver guide also stated, "Make an IMMEDIATE power recovery if the following conditions do not exist through 100' AGL: Aircraft aligned with touchdown point; Rotor RPM in the green; Airspeed within +/- 5 [knots] of 65 [knots]; Rate of descent <1,500 fpm".
The manufacturer's Pilots Operating Handbook outlined the following procedure for a practice autorotation with a power recovery: "1. Adjust carb heat as required. 2. Lower collective to down stop and adjust throttle as required for small tachometer needle separation. CAUTION: To avoid inadvertent engine stoppage, do not chop throttle to simulate a power failure. Always roll throttle off smoothly for a small visible needle split. 3. Adjust collective to keep rotor RPM in green arc and adjust throttle for small needle separation. 4. Keep airspeed 60 to 70 KIAS. 5. At about 40 feet AGL, begin cyclic flare to reduce rate of descent and forward speed. 6. At about 8 feet AGL, apply forward cyclic to level aircraft and raise collective to control descent. Add throttle if required to keep RPM in green arc."
Robinson Helicopter Company Safety Notice SN-38, "Practice Autorotations Cause Many Training Accidents," stated, "There have been instances when the engine has quit during practice autorotation. To avoid inadvertent engine stoppage, do not roll throttle to full idle. Reduce throttle smoothly for a small visible needle split, then hold throttle firmly to override governor. Recover immediately if engine is rough or engine RPM continues to drop."
Safety Notice SN-24, "Low RPM Rotor Stall Can Be Fatal," stated, "Rotor stall is very similar to the stall of an airplane wings at low airspeeds. As the airspeed of an airplane gets lower…the angle of attack of the wing must be higher for the wing to produce the lift required to support the weight of the airplane…The same thing happens during rotor stall with a helicopter except it occurs due to low rotor RPM instead of low airspeed. As the RPM of the rotor gets lower, the angle of attack of the rotor blades must be higher to generate the lift required to support the weight of the helicopter…Even if the collective is not raised by the pilot to provide the higher blade angle, the helicopter will start to descend until the upward movement of air to the rotor provides the necessary increase in blade angle of attack…The increased drag on the blades acts like a huge rotor brake causing the rotor RPM to rapidly decrease, further increasing the rotor stall. As the helicopter begins to fall, the upward rushing air continues to increase the angle of attack on the slowly-rotating blades, making recovery virtually impossible, even with full down collective."
FAA publication P-8740-71, "Planning Autorotations,"was intended to raise flight instructor awareness to the hazards of training students in autorotations and provide guidelines and parameters for conducting practice autorotations. The pamphlet concluded, "The number one error in practice autorotations is the failure of the flight instructor to take control of the aircraft and terminate the maneuver before it progresses to a point where the flight instructor is not capable of recovering the aircraft in time to prevent damage to the aircraft or injury to personnel. REMEMBER: As a flight instructor, you are the most knowledgeable and experienced person in that helicopter. Do not let your student fly the helicopter into some corner of its performance envelope where it is not recoverable."
14 CFR Part 91: General Aviation
Accident occurred Monday, December 29, 2014 in Lake Worth, FL
Aircraft: ROBINSON HELICOPTER R22 BETA, registration: N771MM
Injuries: 1 Fatal, 1 Serious.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
On December 29, 2014, at 1025 eastern standard time, a Robinson R22 Beta, N771MM, was substantially damaged when it impacted terrain while maneuvering for landing at Palm Beach County Park Airport (LNA), Lake Worth, Florida. The certificated flight instructor (CFI) was fatally injured, and the student pilot sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which departed about 0940. The flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.
In a statement to law enforcement, the student pilot recounted that he and the CFI were practicing emergency procedures following a simulated engine failure. The student pilot said that he entered an autorotation after the throttle was reduced to idle, and the helicopter was in an autorotational descent when the accident occurred. He could not completely recall the sequence of events leading up to the accident, but stated that as the helicopter descended through 100 feet, he remembered the CFI saying, "we're going down."
Another CFI, who was taxiing a helicopter with a student on the south side of LNA, reported hearing the accident helicopter transmit, "we're going in the grass" over the airport's common traffic advisory frequency. Shortly thereafter, an airplane in the airport traffic pattern reported that there was a helicopter down, and the CFI flew to the accident site to render assistance.
The helicopter came to rest on its left side in a grassy area about 700 feet northwest of the runway 15 threshold at LNA. The wreckage path was oriented approximately 140 degrees magnetic, and extended about 75 feet from the initial impact point to where the fuselage came to rest. The initial impact point was identified as a large metal stake, about 3 feet in height. The second point of impact was a small crater measuring about 4 feet long and 1 foot deep, located about 15 feet past the initial impact point. A portion of the forward skid crosstube was located in the crater. The vertical stabilizer, horizontal stabilizer, and portion of the tail rotor came to rest next to the crater. The tail boom was separated from the fuselage, and fractured into several pieces, some of which displayed signatures consistent with main rotor blade contact. The skids separated from the fuselage and were fractured into several sections, which were located along the wreckage path.
The fuselage exhibited downward crushing, and the cabin was fractured aft of the seat structures. Both the auxiliary and main fuel tanks were intact and contained fuel, and both fuel caps were secure. The fuel vent tubes were separated from the auxiliary tank by impact, which allowed fuel to drain from the tanks following the accident.
The main rotor remained attached to the fuselage. One blade was bent up and displayed several chordwise creases along its span. The second blade was bent up about 45 degrees near its root. Neither blade displayed significant leading edge damage. The tail rotor drive shaft separated from the helicopter during the accident sequence, and a 5-foot portion was located about 500 feet west of the main wreckage. The aft portion of the tail rotor drive shaft was not recovered.
The helicopter was removed from the accident site and transported to a salvage facility for further examination. Flight control continuity was confirmed from the cockpit area to the main rotor system. Tail rotor control continuity was established from the cockpit to the intermediate flex coupling. The main rotor gearbox rotated smoothly by hand with no anomalies observed. Examination of the v-belts, sheaves, and overrunning clutch also revealed no anomalies.
Tail rotor drive continuity was established from the upper drive sheave to the intermediate flex coupling. The tail rotor gearbox rotated smoothly, with no anomalies noted. Power was applied to the engine starter, and utilizing the fuel onboard, the engine started, accelerated smoothly, and ran continuously for several minutes with no anomalies noted.
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