Thursday, June 1, 2017

Cessna 180, N4696B: Accident occurred March 13, 2016 in Boulder, Garfield County, Utah

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

Aviation Accident Data Summary - National Transportation Safety Board: https://app.ntsb.gov/pdf

http://registry.faa.gov/N4696B 

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Salt Lake City, Utah

Continental Motor, Inc.; Mobile, Alabama

NTSB Identification: WPR16LA083 
14 CFR Part 91: General Aviation
Accident occurred Sunday, March 13, 2016 in Boulder, UT
Probable Cause Approval Date: 05/25/2017
Aircraft: CESSNA 180, registration: N4696B
Injuries: 3 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The private pilot reported that, during the takeoff run from the 2,100-ft-long soft, unimproved dirt airstrip, he observed that the propeller rpm was 2,600; he did not observe the manifold pressure reading. The pilot reported that the airplane seemed to accelerate slowly, which he thought was likely due to the soft runway surface or vegetation. About halfway to two-thirds down the runway, as the tail was coming off the ground, the pilot added a notch of flaps as the airplane continued to roll on its main landing gear. As the airplane approached the end of the runway, the pilot pulled back on the control yoke, which increased the angle of attack. The airplane then climbed about 2 ft above the ground before settling into sagebrush off the end of the runway. The airplane subsequently impacted a tree and came to rest upright about 50 yards from the tree. 

The pilot stated that he thought the engine might not have been producing full power and that he should have aborted the takeoff at that time. However, a postaccident examination of the airframe and engine, which included two engine test runs, did not reveal any anomalies that would have precluded normal operation. If the pilot had chosen to abort the takeoff when he noted that he airplane was accelerating slowly, the accident likely would have not occurred.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's failure to abort the takeoff from the soft runway surface, which precluded optimal acceleration during the takeoff sequence.

On March 13, 2016, about 0800 mountain daylight time, N4696B, a taiwheel equipped Cessna 180, was substantially damaged when the airplane failed to accelerate and overran the end of the runway surface while attempting to take off from a private airstrip about 2 nautical miles west of Boulder, Utah. The commercial pilot, who was the owner of the airplane, and his two passengers were not injured. Visual meteorological conditions prevailed for the planned local flight, which was being operated in accordance with 14 Code of Federal Regulations Part 91, and a flight plan was not filed. The flight was originating at the time of the accident.

In a report submitted to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that prior to departing, he allowed the engine to warm up for about 15 minutes. He also rechecked the magnetos, listened to the engine at higher power settings, and due to the airstrip being dirt, did not check the carburetor heat; normal oil pressure was observed. The pilot stated that after he applied full power and started the takeoff roll [to the west] on the 2,100 foot unimproved dirt airstrip, he observed the acceleration to be "ok", but felt a little slow. The pilot added that he thought the dirt might have been soft, or that the vegetation was slowing the airplane down, but when he glanced at the tachometer it was reading right at the redline, 2,600 rpm; he did not remember looking at the manifold pressure gauge, nor did he report the engine running rough or backfiring. The pilot opined that about one-half to two-thirds of the way down the runway the tail lifted off the runway's surface, at which point he added one notch of flaps as the airplane continued to roll on its main landing gear. The pilot reported that as the end of the airstrip approached he pulled back on the control yoke, which resulted in an increase in the angle-of-attack. The airplane subsequently lifted about two feet off the runway surface before settling into the sagebrush. The pilot stated that when he attempted to reduce power by retarding the throttle, the engine continued to run at the same high-output level. As the airplane continued to roll it was slowed by the vegetation, and subsequently impacted a 10-foot diameter tree before coming to rest upright about 50 yards from the tree stump. The pilot stated that he suspected that the engine was not generating full power, and that he could have aborted the takeoff at that time. The pilot reported that winds were from the northwest at 5 knots. A postaccident examination of the airplane revealed substantial damage to both wings and the elevator. The airplane was recovered to a secure location for further examination.

On April 27, 2016, under the supervision of the NTSB IIC, a Continental Motors Inc. field technician performed an examination of the engine at the facilities of Air Transport, Phoenix, Arizona. 

The engine remained attached to the airframe via the engine mount legs. No external damage was noted. The top spark plugs were removed and exhibited grey combustion deposits. The electrodes had normal, worn out signatures. The cylinder combustion chambers were examined with a lighted borescope, with no anomalies noted. The crankshaft was rotated by hand using the propeller, with thumb compression confirmed on all six cylinders. The magneto impulse couplings were audible, and spark was produced on all six top spark plug leads.

In preparation for a test run of the engine, an external fuel supply was plumbed into the right wing root fuel line. The fuel selector was placed in the right hand position for the first engine run.

After the engine was started and allowed to warm up, the throttle was advanced to 1,600 rpm and a magneto check performed; each magneto dropped about 75 rpm. When the throttle was advanced full forward, the engine obtained 2,600 rpm and 22 inches of manifold pressure. The throttle was then reduced to idle to allow the engine to cool down before it was secured using the mixture control. No binding of the throttle or mixture controls was noted during the engine run.

The fuel supply was then plumbed into the left wing root fuel line to verify proper operation of the fuel selector in the left hand position. The engine was then restarted and ran normally. When the selector was placed in the "both" position, the engine continued to run normally. The fuel selector was then moved to the "off" position, and after several seconds it began to run rough. The fuel selector was subsequently positioned to the left tank position, from which it ran smoothly. The engine was allowed to cool down at idle before a normal shut down was accomplished using the mixture control lever.

On April 27, 2017, at the facilities of Air Transport, Phoenix, Arizona, the NTSB IIC performed an examination of the airframe. No anomalies were noted during the examination.

The postaccident examination of the engine and airframe failed to reveal any anomalies that would have precluded normal operation.

NTSB Identification: WPR16LA083 
14 CFR Part 91: General Aviation
Accident occurred Sunday, March 13, 2016 in Boulder, UT
Aircraft: CESSNA 180, registration: N4696B
Injuries: 3 Uninjured.

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 may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

On March 13, 2016, about 0800 mountain daylight time, N4696B, a Cessna 180, was substantially damaged when the airplane failed to accelerate while attempting to take off from a private airstrip about 5 miles west of Boulder, Utah. The commercial pilot, who was the owner of the airplane, and his two passengers were not injured. Visual meteorological conditions prevailed for the planned local flight, which was being operated in accordance with 14 Code of Federal Regulations Part 91, and a flight plan was not filed. The flight was originating at the time of the accident.

In a telephone interview with the National Transportation Safety Board investigator-in-charge shortly after the accident, the pilot reported that on the takeoff roll from the 1,600 foot unimproved airstrip, the airplane did not accelerate as he would normally expect it to. The pilot further reported that he observed the rpm was near the redline, however, he did not recall the manifold pressure reading. The pilot stated that when he realized he was too far into the takeoff roll to stop the airplane on the runway remaining, he added a notch of flaps and pulled aft on the control column in an attempt to get the airplane airborne. However, the attempt to get the airplane off the ground was unsuccessful due to impact with a berm and scrub brush, which resulted in substantial damage to the airplane's fuselage and elevator.

The airplane was recovered to a secured facility for further examination.

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