Friday, June 25, 2021

Loss of Engine Power (Partial): Cessna P337H Pressurized Skymaster, N337LJ; fatal accident occurred June 24, 2013 in San Luis Obispo, California

Scott Metzger, 44, of San Luis Obispo

Scott Metzger
~

"I am the friend in the report who is also a pilot that helped the NTSB fill in the gaps. NTSB showed up late that day, I helped them piece everything together, one guy, good person and listener. I had all the answers, I was his best friend, kitesurfing, travelling, consulting work together on a daily basis.  I thought some information could help others."

"The summary is close but not correct, so I added where things need to be corrected." 

Flight Path I made for the NTSB 

He traveled 1.07 miles to the first point of impact.  This is my interpretation from the accident photos, which is only an interpretation of the photos from the accident. In the news photos, the FedEx driver was missed getting killed and got out of the truck by 30 seconds turning the corner.  I was on the scene and asked to ID'd him - just a burnt torso - very hot fire. The engine pics were taken before by me.  I have a text saying the throttle issue is going to be fixed when he gets to PA - he was told they could not find a big enough anomalie as I was told the Friday before over a long discussion.  I was unaware of detailed mechanic instructions, but know of them and know they are all good mechanics. 

1 = Telephone Pole - broke 3 main electrical cables
2 = Struck pine tree, sheared 14" dia. trunk
= Block wall - nose first 
= Resting place

His plane flew along this path.  I calculated the following in the hour following his crash - not the 95+/- I speak to it later.

Topographic Height of Hills = 254' 

Estimated Aircraft Height = 254' x .65 = 165' AGL

Telephone/Power Pole Height 60' 

Safety  margin = 95' +/-

** Attached Pics & Video

NTSB Identification: WPR13FA289
14 CFR Part 91: General Aviation
Accident occurred Monday, June 24, 2013 in San Luis Obispo, CA
Probable Cause Approval Date: 12/10/2014
Aircraft: CESSNA P337H, registration: N337LJ
Injuries: 1 Fatal.

The NTSB 

The pilot/owner had recently purchased the multi-engine, high-performance, complex airplane. He had obtained his private pilot certificate 15 years before the accident and had limited flight experience, having amassed a total of about 118 hours of flight time. He had obtained his multi-engine rating 5 weeks before the accident, and his total flight experience in multi-engine airplanes was about 40 hours. Of that time, 18 hours were logged in the accident airplane of which 3 hours were while acting as pilot-in-command.

On previous flights, the airplane's rear engine had been "stuttering" as the throttle was advanced. The pilot was able to forestall the problem by advancing the throttle slowly; however, the symptoms had been getting worse. (Scott described the anomaly only during cruise - I was supposed to be on the plane when it crashed - I am his closest friend). A maintenance facility at the departure airport attempted to troubleshoot the engine problem but was not able to resolve the issue (We talked through many times the issue and he did cross talk to the mechanics, but they did not - I default all belief to the mechanics first what Scott told me second in any statement I make). Thus, the pilot intended to reposition the airplane to another airport where a different maintenance facility had agreed to continue the diagnosis.(Scott was dot com, worked in San Jose commuted weekly, he would be up north 3 days mechanics had it vice versa.  I believe the SLO mechanic 2x and PA 3x, first visit sure a talk not look, but not sure). 

(This is my statement to the NTSB what he and I planned to do the day before the crash.  I went through a detailed list of questions with him about potential issues and what mechanics said, again that conversation was 8 years ago, but clear - never heard anything about RPM drop like described.  BTW Scott was brilliant, you could take a stack of 1 100 non sequential bills he would read the serials once, pull any bill out he could remember the complete series, only bill numbers - lol but a brilliant businessman. His "uh" while typed is actually different like uhmmmmmmm, but I would type the same thing you did, when he does this he is working a problem, on the boat or car or home, so I know at that point he had an issue he was trying  (We)  He planned to fly the airplane in the traffic pattern (Sat before the crash at SBP), perform a touch-and-go landing. (I did not pick up the phone - I looked at the blue sky and said nah go tomorrow, going to waste time - I lived) we kitesurfed - live in the same town, traveled together, worked in parallel career goals, he was a brother to me and vice versa) and proceed to the other maintenance facility if the airplane performed correctly. He had also made plans to depart that night on an important and time-sensitive business trip to Europe from an airport close to the second maintenance facility.

The departure for the initial flight appeared uneventful; however, during the approach for the touch-and-go landing, the pilot seemed distracted, missing multiple landing clearances issued by an air traffic controller. (Good assessment - for Scott the smarts were his pitfall - overfocus) The airplane landed and used the full runway length for the ground roll, while making "popping" sounds similar to an engine backfiring, indicative of at least a partial loss of engine power. Having reached the end of the runway, the airplane lifted off and climbed to about 150 feet above ground level (I made my calculation within hours of the accident - I actually was on scene coming back from a business trip - helped ID the body with the detectives), and a short time later the pilot issued a mayday transmission. The airplane maintained the runway heading and the same altitude for about a mile and then began a descending right turn, striking a set of power distribution lines and a building. The length of the runway and its overrun area would have provided ample stopping distance for the airplane after the landing. Further, the area between the runway and accident site was comprised of level fields which would have been adequate for an emergency landing. (This area is actually a death trap - the worst - abandoned Chevron field oil saturated - they finally cleaned it up - our history is amazing if you look up Tank Farm Road, Avila Beach Clean-up, all from the 20s.  The fields were all planted and tilled for strawberries, I have a degree in Landscape Architecture - lol another great story for NWA.  The cuts are 2' deep and the fields were running perpendicular to the landing straight.  In the crash video you will see him bank right, he was trying to catch the street, straight ahead 30 second nowhere to land, last resort left (better choice to Madonna Plaza - than right, but that tells me he was working the problem not thinking solutions (lack of experience).

Another factor I discussed with his 337 instructor many times was about the landing gear, once during training. The 337 drops 100' to 150' depending on the plane and weather, my understanding from memory is the wheel swing creates the drag, and to keep the gear down until 2-300 feet, so Scott was acting under training - I discussed this with the NTSB, who was great.  The individual they sent had worked on another if I remember correctly, and we had many discussions about limitations.  I did discuss with a retired major, and my business partner a CMDR Naval partner agreed, while a great plane whey said it was a death trap for some because of the read engine issues of not seeing it. 

The majority of the airplane's structure was consumed by post-impact fire. The front engine's propeller displayed considerable rotational damage, consistent with it producing power at the time of the accident. The rear propeller exhibited less significant rotational damage signatures, consistent with it operating at a reduced power level. The rear engine sustained thermal damage, which precluded a determination of the reason for the loss of power.

Postaccident examination of the front engine revealed that the right magneto was set to an incorrect timing position. The left magneto had broken free during the impact sequence, so its timing position could not be ascertained. If the left magneto had been set to the correct timing position, the incorrect timing of the right magneto would have resulted in a minimal loss of engine power. Additionally, although no damage was noted to the right magneto, it is possible that it became misaligned during the impact sequence. Lastly, because the engine was producing power at the time of impact, it is unlikely that both magnetos were misaligned.

Performance charts indicated that at the airplane's takeoff weight, a total loss of engine power from the rear engine should have allowed for an adequate takeoff profile, assuming the emergency procedures detailed in the Pilot's Operating Handbook for the airplane had been followed. However, examination revealed that the procedures had not been followed because at the time of impact, the flaps were not completely retracted, and the rear engine's propeller was not feathered. Although the pilot had the minimum experience required to fly the multiengine airplane, he had only acted as pilot-in-command of this airplane for 3 hours; and when he was faced with an emergency, he likely did not have the proficiency and confidence to readily deal with it. The pilot was likely distracted during the landing (as supported by the missed radio calls), failed to abort the landing and continued with his original plan to takeoff despite the loss of engine power, and was unable to appropriately configure the airplane for flight with only one engine operable after the takeoff.



































Aviation Accident Final Report - National Transportation Safety Board

The National Transportation Safety Board traveled to the scene of this accident.

Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; San Jose, California 
Cessna Aircraft Company; Wichita, Kansas
Continental Motors Incorporated; Mobile, Alabama 

Investigation Docket - National Transportation Safety Board:

 
Location: San Luis Obispo, California 
Accident Number: WPR13FA289
Date & Time: June 24, 2013, 12:55 Local
Registration: N337LJ
Aircraft: Cessna P337H
Aircraft Damage: Destroyed
Defining Event: Loss of engine power (partial) 
Injuries: 1 Fatal
Flight Conducted Under: Part 91: General aviation - Personal

Analysis

The pilot/owner had recently purchased the multiengine, high-performance, complex airplane. He had obtained his private pilot certificate 15 years before the accident and had limited flight experience, having amassed a total of about 118 hours of flight time. He had obtained his multiengine rating 5 weeks before the accident, and his total flight experience in multiengine airplanes was about 40 hours. Of that time, 18 hours were logged in the accident airplane of which 3 hours were while acting as pilot-in-command.

On previous flights, the airplane's rear engine had been "stuttering" as the throttle was advanced. The pilot was able to forestall the problem by advancing the throttle slowly; however, the symptoms had been getting worse. A maintenance facility at the departure airport attempted to troubleshoot the engine problem but was not able to resolve the issue. Thus, the pilot intended to reposition the airplane to another airport where a different maintenance facility had agreed to continue the diagnosis. He planned to fly the airplane in the traffic pattern, perform a touch-and-go landing, and proceed to the other maintenance facility if the airplane performed correctly. He had also made plans to depart that night on an important and time-sensitive business trip to Europe from an airport close to the second maintenance facility.

The departure for the initial flight appeared uneventful; however, during the approach for the touch-and-go landing, the pilot seemed distracted, missing multiple landing clearances issued by an air traffic controller. The airplane landed and used the full runway length for the ground roll, while making "popping" sounds similar to an engine backfiring, indicative of at least a partial loss of engine power.

Having reached the end of the runway, the airplane lifted off and climbed to about 150 feet above ground level, and a short time later the pilot issued a mayday transmission. The airplane maintained the runway heading and the same altitude for about a mile and then began a descending right turn, striking a set of power distribution lines and a building. The length of the runway and its overrun area would have provided ample stopping distance for the airplane after the landing. Further, the area between the runway and accident site was comprised of level fields which would have been adequate for an emergency landing.

The majority of the airplane's structure was consumed by postimpact fire. The front engine's propeller displayed considerable rotational damage, consistent with it producing power at the time of the accident.

The rear propeller exhibited less significant rotational damage signatures, consistent with it operating at a reduced power level. The rear engine sustained thermal damage, which precluded a determination of the reason for the loss of power.

Postaccident examination of the front engine revealed that the right magneto was set to an incorrect timing position. The left magneto had broken free during the impact sequence, so its timing position could not be ascertained. If the left magneto had been set to the correct timing position, the incorrect timing of the right magneto would have resulted in a minimal loss of engine power. 

Additionally, although no damage was noted to the right magneto, it is possible that it became misaligned during the impact sequence. Lastly, because the engine was producing power at the time of impact, it is unlikely that both magnetos were misaligned.

Performance charts indicated that at the airplane's takeoff weight, a total loss of engine power from the rear engine should have allowed for an adequate takeoff profile, assuming the emergency procedures detailed in the Pilot's Operating Handbook for the airplane had been followed. However, examination revealed that the procedures had not been followed because at the time of impact, the flaps were not completely retracted, and the rear engine's propeller was not feathered. Although the pilot had the minimum experience required to fly the multiengine airplane, he had only acted as pilot-in-command of this airplane for 3 hours; and when he was faced with an emergency, he likely did not have the proficiency and confidence to readily deal with it. The pilot was likely distracted during the landing (as supported by the missed radio calls), failed to abort the landing and continued with his original plan to takeoff despite the loss of engine power, and was unable to appropriately configure the airplane for flight with only one engine operable after the takeoff.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
Loss of engine power from the rear engine for reasons that could not be determined because of the postimpact thermal damage to the engine. Contributing to the accident were the pilot's decision to continue flight with a known deficiency, his failure to abort the takeoff during the ground roll, his failure to follow the correct emergency procedures following the loss of power, and his lack of experience in multiengine airplanes and the specific airplane make and model.

Findings

Not determined (general) - Unknown/Not determined
Personnel issues Decision making/judgment - Pilot
Personnel issues Incorrect action selection - Pilot
Personnel issues Total experience w/ equipment - Pilot

Factual Information

HISTORY OF FLIGHT

On June 24, 2013, at 1255 Pacific daylight time, a Cessna P337H, N337LJ, collided with a power distribution line, building, and delivery truck following takeoff from San Luis Obispo County Regional Airport, San Luis Obispo, California. The airplane was registered to CSC Solutions LLC, and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91. The private pilot/owner sustained fatal injuries; the airplane was destroyed by impact forces and a post impact fire. The cross-country personal flight departed San Luis Obispo at 1254, with a planned destination of Palo Alto Airport of Santa Clara County, Palo Alto, California. Visual meteorological conditions prevailed and no flight plan had been filed.

According to a friend of the pilot, during the month leading up to the accident, the rear engine was "stuttering" as the throttle was advanced from idle to full power. The pilot reported that he was able to forestall the problem by advancing the throttle slowly. The friend had not experienced this problem, having flown with him on a number of occasions; however, the pilot stated to him that it had been getting worse during the 2-week period leading up to the accident.

PCF Aviation, at the pilot's home base of San Luis Obispo, began troubleshooting steps on the rear engine about 1 week prior to the accident. Although they could reproduce the problem, they could not definitively determine its cause, and the pilot asked them to discontinue the diagnosis.

Another mechanic at a maintenance facility (Advantage Aviation) located at Palo Alto Airport, stated that the airplane was brought to him about 2 weeks prior, and that he had attempted to diagnose the same problem. He briefed the pilot on the most likely cause, and was subsequently approached again by the pilot, who agreed to fly the airplane back to his facility on the day of the accident for further diagnosis.

The pilot had also made plans to depart on an international commercial flight from San Francisco International Airport (20 miles from Palo Alto by automobile) at 1925 later that evening. According to his wife, the reason for the flight was so that he could attend a time sensitive business meeting in Europe.

According to the pilot's friend, the pilot planned to fly the airplane in the traffic pattern, and if all was well, continue the flight to the maintenance facility in Palo Alto.

The airplane departed uneventfully and flew a single circuit in the traffic pattern. The pilot requested a touch-and-go landing, and while on the final approach leg for runway 29, an air traffic controller issued landing clearances to the pilot on three different transmissions. The pilot responded to the last transmission, accepting the clearance for the touch-and-go.

A series of security cameras were located at various positions along the length of runway 29. They captured video of various segments of the flight sequences. The recordings revealed that during the touch-and-go, the airplane appeared to utilize almost the full runway length for the ground roll. As it reached the runway overrun, it climbed to about 70 feet above ground level (agl) with the landing gear retracted. The climb progressed to about 150 feet agl and a short time later, the pilot transmitted, "Mayday Mayday". The tower controller responded, and a broken transmission of, "uh" was then received.

A camera located at a tire service center, about 1 mile west-northwest of the departure end of runway 29 recorded the airplane's departure path. The camera was facing northeast, and recorded the airplane flying on a northwest track at an altitude of about 150 feet agl. The airplane remained level and then began to descend out of view, and 4 seconds later, power to the camera was lost. About 20 seconds later power was restored, and a plume of smoke was seen in the vicinity of the airplane's descent path. The airplane collided with a power distribution line during the descent, temporarily shutting off power to multiple local businesses.

Multiple witnesses located at various locations within the airport perimeter recounted observations similar to the video recordings. They recalled that their attention was initially drawn to the airplane because it was producing an unusual sound during the departure roll of the touch-and-go. An air traffic controller reported that she heard the sound of a "bang," and looked below towards the airplane as it passed the control tower at midfield. Another witness described the airplane as making a "popping" sound, with another stating the sound was similar to a radial engine. A witness located at an FBO at midfield, stated that he looked up when he heard the sound of "propellers out of sync" and when he did so, he observed the airplane traveling northwest along the runway.

A witness who was in an airplane holding short of runway 29 was cleared to "line up and wait" by air traffic control personnel just after the accident airplane passed him on the runway after landing. The witness stated that as he looked up he perceived that the airplane was continuing on the runway for a long time. It finally rotated as it approached the runway end, and continued at a low altitude, flying in what he described as ground effect. It eventually transitioned to a shallow climb, with a steep angle of attack such that he could see the entire upper wing surface. The airplane then began to "mush" back down, remaining in the nose-high attitude, and rocking from side to side. It then began a rapid descent, followed a short time later by a flash.

PERSONNEL INFORMATION

The 44-year-old pilot was originally issued a private pilot certificate with ratings for airplane single-engine land in 1998. In May 2013, about a month before the accident, he was issued an additional rating for multiengine land. At that time he reported his total flight experience in airplanes was 82 hours, of which 23 hours he acted in the capacity of pilot-in-command, primarily in a Cessna 152. He also reported 29 hours of rotorcraft experience, with 1.1 hours as pilot-in-command.

The pilot's logbooks indicated his multiengine training utilized about 22 hours of flight time, and occurred in a Piper PA-44 during the period from April 6, 2013, through to his check ride on May 16, 2013. Over the following month he received about 14 hours of dual instruction in the accident airplane culminating in his high performance and complex-airplane endorsements. His last logbook entry was dated June 3, 2013, and indicated a total flight experience of 118 hours, of which 2.8 hours was logged as pilot-in-command time in the accident airplane.

A review of Federal Aviation Administration (FAA) airman records revealed that the pilot held a third-class medical certificate issued in March 2013 with no limitations.

AIRPLANE INFORMATION

The pressurized, high-wing, centerline-thrust multiengine airplane was manufactured in 1978, and purchased by the pilot 2 months prior to the accident. It was powered by two Continental Motors Incorporated TSIO-360 series turbocharged-engines and equipped with McCauley two-blade constant-speed propellers.

The last entry in the airplane's maintenance logbooks was a 100-hour/annual inspection, which was recorded as being completed on March 22, 2013. At that time, the airframe had accrued 2,096.2 total flight hours. The front and rear engines had accumulated 1,110 and 616 hours, respectively, since their factory rebuild.

A work order dated 1 week before the accident was provided by PCF Aviation, which documented the diagnosis of the rear engine. The order indicated that the engine stuttered at 2,000 rpm, and that maintenance personnel could duplicate the problem, but were unable to resolve the discrepancy. The "Action Taken" section of the order specifically stated:

"Adjusted aft idle mixture and check aft engine fuel pressures per Teledyne Continental SID97-3E. Fuel pressures satisfactory. Swapped fuel pump and flow divider from forward to aft engine. No change in aft engine. Returned fuel pumps to original configuration. Inspected aft engine for induction leaks, no discrepancies found. Stopped troubleshooting at owners request.... Found excessive play in prop governor assembly linkage. Notified owner that prop governor needed to be sent out for repair/overhaul."

The owner of PCF Aviation stated that he informed the owner that the airplane had not been repaired. The pilot stated that the problem was, "manageable" and that he would take it to another repair facility. The airplane then remained on the ramp, and was not flown again until the day of the accident.

In a post-accident interview, the mechanics at PCF Aviation who performed the diagnosis stated that the propeller blade pitch angle did not change while the engine was stuttering, and they therefore discounted a governor problem as the cause. They further stated that if the throttle was rapidly advanced the engine speed would reach 1,900 to 2,100 rpm, and then stutter and "oscillate" but not reach full speed.

A mechanic from Advantage Aviation in Palo Alto stated that he had performed troubleshooting steps about 2 weeks prior to the accident for the same problem, and that he recommended the governor control be sent to a repair facility for overhaul. Work orders for that visit indicated that the tachometer for the front engine was providing intermittent readings, and that this discrepancy was resolved by repairing the right-hand magneto ground. 

AIRPORT INFORMATION

Runway 29 at San Luis Obispo Airport was 6,100 feet long, by 150 feet wide, and comprised of asphalt. A 600-foot-long blast pad/stopway projected beyond the runway's departure end, and the area from the runway to the accident site was comprised of level open fields, transected by a two-lane road.

Following the accident, the runway was examined for remnants of foreign objects or recent propeller strike damage; none were found.

MEDICAL AND PATHOLOGICAL INFORMATION

An autopsy of the pilot was conducted by the San Luis County Sheriff-Coroner's Office. The cause of death was reported as the effect of multiple blunt force trauma injuries, with significant contributing conditions including smoke inhalation, and extensive thermal injuries.

Toxicological tests on specimens recovered from the pilot were performed by the FAA Civil Aerospace Medical Institute. The results were negative for all screened drug substances and ingested alcohol. With the following findings for carbon monoxide, and cyanide:

18 (%) CARBON MONOXIDE detected in Blood
0.41 (ug/ml) CYANIDE detected in Blood

Refer to the toxicology report included in the public docket for specific test parameters and results.

WRECKAGE AND IMPACT INFORMATION

The main wreckage came to rest adjacent to a building in a business park, 1 mile beyond, and directly in line with, the departure end of runway 29. The initial point of impact was characterized by damage to a series of three power-distribution lines located on the border of the street, which divided the building and a strawberry field. Two of the lines had become separated from their insulator supports on top of the 35-foot-tall wooden power pole. Two pine trees adjacent to the distribution lines were topped at the 35-foot level. A second tree, 50 feet to the northwest, exhibited a 40-foot-wide swath of cut branches at an angle 45 degrees relative to the ground. The debris field, consisting of tree branches and limbs, continued another 25 feet to the building. The building's east-facing wall was about 30 feet tall and constructed of cement blocks. The right wing was located on the roof of the building, just above a series of diagonal white, blue, and black paint transfer marks on the face of the wall. Additionally, the debris field, consisting of the rear engine's turbocharger inlet wheel and shroud, as well as cowling fragments, continued to the main wreckage, which had come to rest impinged against the front of a truck. The entire cabin area was consumed by fire and a fuel odor was present at the site.

The entire cabin structure and wing center section was consumed by fire, with burnt wire remnants, seating structure, and lower frame components remaining. The flap actuator jack screw displayed 2.9 inches of thread between the screw and actuator housing, which corresponded to 10-degree (1/3) flap deployment. The main and nose gear were in the stowed position. The engine controls within the cabin were in the full forward position, with the exception of the rear engine mixture control, which was about 10 degrees short of full forward.

The horizontal stabilizer had separated from the tailbooms and sustained crush damage along the entire length of its leading edge. The elevator and associated trim tab remained attached to the stabilizer; the elevator trim tab actuator position could not be determined accurately due to its cabling having been pulled through the structure during the impact sequence.

The propeller for the front engine remained attached to the crankshaft and exhibited leading edge gouges, chordwise scratches, and tip twist to both blades. The spinner along with the propeller hub dome sustained radial gouge marks.

The rear engine's propeller had separated at the crankshaft and was located behind the truck. Both blades remained attached to the hub; one blade exhibited 15 degrees bending along its entire length, the second blade had twisted about 60 degrees forward and exhibited chordwise scratches at the tip.

Both propeller domes contained markings consistent with the counter weights making contact with it during impact. The orientation and position of the markings were consistent with the propeller blades being at a flat pitch (power) setting.

TESTS AND RESEARCH

Engine Examinations


Both engines were removed from the airplane and transported to the facilities of Continental Motors Incorporated (CMI) for examination by the NTSB investigator-in-charge and representatives from the FAA, Cessna Aircraft Company, and CMI. A complete examination report is contained within the public docket.

Rear Engine

The rear engine sustained thermal discoloration and sooting throughout.

Both magnetos remained attached to the crankcase; the spark plug leads were thermally damaged and continuous to the spark plugs. The propeller governor remained attached to the forward crankcase, with its control linkages continuous through to the firewall. The propeller synchronization motor and gears remained attached. The governor unit was removed and the input shaft rotated smoothly by hand. A brown-colored oil flowed from the passages of the unit and the screen was noted to be free of debris. The control arm moved freely. Disassembly revealed the pump gears, fly weight, and drive gear to be intact.

The engine driven fuel pump remained attached to the forward crankcase. An external examination revealed that it appeared undamaged, was coated in black soot, and all fuel lines were firmly attached at their fittings on the pump. The mixture control arm was bent; its control cable and eyebolt remained attached and continuous through to the firewall.

All upper ancillary components, including the fuel manifold valve, induction manifold risers, and fuel metering unit exhibited black discoloration. All lines to the fuel injection nozzles were intact with their fittings tight. The fuel pump and metering unit exhibited thermal damage to all internal components consistent with post-impact fire.

Due to the thermal damage sustained, an engine test run could not be performed. As such, the engine core was disassembled and the turbocharger examined; no anomalies were found that would have precluded normal operation.

Front Engine

The front engine remained partially attached to its mounts and had sustained varying degrees of impact damage to the sump, left magneto (which had broken away from the pad), both magneto harnesses, starter motor, and the number one cylinder.

The right magneto remained attached to the engine case, and did not display any obvious indications of damage. Its timing to the engine was tested utilizing a magneto synchronizer. The test revealed that the magneto points opened at 1 degree after top dead center (TDC) instead of the nominal 20 degrees before TDC. According to representatives from CMI, a 20-degree change in crankshaft angle corresponds to a circumferential change of 0.5 inches at the magneto flange, which equals about 16 degrees of angular rotation to the magneto.

The engine was installed in a test cell and an engine run was performed with the right magneto remaining in its as-found position of one degree after TDC. A replacement left magneto was attached and set to the same 1 degree after TDC position in an effort to gauge engine performance with two incorrectly timed magnetos. The engine started after two attempts and was run at 1,000 rpm for 5 minutes at which point the oil reached its standard operating temperature. The throttle was then advanced to a fully open position and the engine speed increased. The maximum speed that could be attained was 1,850 rpm at an indicated manifold pressure of 38.5 inHg; with the throttle in the full open position, the engine should have been able to reach a speed of at least 2,400 rpm. A magneto check was then performed in accordance with the Cessna P337H Pilots Operating Handbook (POH), and the engine speed was observed to drop 200 rpm for each magneto. According to the POH, the rpm drop should not exceed 150 rpm on either magneto, or 50 rpm differential between magnetos.

The left magneto was then set to the correct ignition timing of 20 degrees before TDC and another engine run was performed. The engine started immediately and responded smoothly to throttle inputs. A magneto check was performed at 1,800 rpm, and a drop of 20 rpm was observed when the left magneto was selected, and a drop of 240 rpm with the selection of the right magneto. The engine appeared to run normally and was capable of reaching maximum rpm.

A final series of engine runs were performed with both magnetos set to 20 degrees BTDC. The engine operated smoothly throughout its rpm range, and was able to achieve its maximum speed at a corresponding nominal manifold pressure.

A post engine test cylinder leakage test was performed in accordance with the latest revision of CMI Service Bulletin SB03-3 and normal pressure readings were attained.

The right magneto was subsequently removed and examined; the internal timing was correct, and no anomalies were noted that would have precluded normal operation. The original left magneto was installed on a test stand and operated at speeds varying between 500 and 2,100 rpm. All leads produced a spark in proper firing order and the impulse coupling triggered appropriately.

ADDITIONAL INFORMATION

The airplane's POH documented the following emergency procedures for continuing a takeoff with an engine inoperative:

1. Throttles -- FULL FORWARD.
2. Propeller Controls -- FULL FORWARD.
3. Mixture Controls-- FULL FORWARD.
4. Inoperative Engine -- IDENTIFY from manifold pressure, RPM, fuel flow and EGT (if installed) indications....NOTE Verify inoperative engine by momentarily closing throttle and noting power response to throttle movement.
5. Windmilling Propeller-- FEATHER PROMPTLY.
6. Wing Flaps -- RETRACT slowly.
7. Airspeed-- 89 KIAS (80 KIAS with obstacles ahead).
8. Landing Gear -- RETRACT (after immediate obstacles are cleared).
9. Inoperative Engine -- SECURE.

Furthermore, a single engine rate of climb of 440 feet per minute would have been possible at sea level, with a temperature of 20 degrees C, under the following conditions:

-Weight 4,400 pounds
-Inoperative Propeller Feathered
-Flaps Up
-Gear Up
-2800 RPM
-37 Inches Hg
-Mixture Set at 140 PPH
-Cowl Flaps Open on Operating Engine
-Cowl Flaps Closed on Inoperative Engine

The sea level landing distance under similar conditions and utilizing the short field landing technique would have been about 810 feet.
































3 comments:

  1. "Better than most 337's he had flown." Kind of says it all. Another sky smashed. Lost a colleague in another one years ago. The "safe" light twin that isn't; but then fatal rates with light twins in general have always been much too high. They do not deliver the real world engine-out safety that they make pilots feel that they will, especially inexperienced ones.

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    Replies
    1. You just validated what you probably didn't intend to do: twins are no more dangerous than singles. One just has to be competent in flying one and practice engine out ops regularly. Even if one can do it by memory in practice with no checklist, an unexpected real emergency throws off instant memory recall.

      The vast majority if not all of twin crashes from pilot error are from improper procedures followed that are detailed in the engine out emergency checklist. That was clearly the case here. Further, this being a centerline twin with no engine out torque roll even more validates that it is a lack of following emergency procedures in the POH that kills twin operators.

      I've been flying piston twins for over 20 years and never had a failed engine emergency. But I still practice them a few times a year with an instructor and go over the procedure in the emergency checklist before every flight. Again, there is nothing more inherently dangerous about flying a twin than a single. However, a twin requires twice the amount of attention. Pretty simple concept. At least to me.

      Delete
  2. Twins are safer than singles. No doubt. But some twin pilots are double dangerous. See above.. Pilot errors all over.. CFI. 2 full feathered landings done. No accidents..

    ReplyDelete