BOISE, ID, USA
N9111Y
PIPER PA-31
After flying the airplane earlier in the day, the pilot-in-command (Chief Pilot} requested that the engines receive an adjustment for improved performance. The Director of Maintenance performed the adjustments by adjusting the fuel mixture control units on both engines. After the adjustment, the PIC and dual student departed for a Part 135 training flight. No problems were noted during the preflight inspection, engine start-up, taxi, engine run-up, and initial takeoff roll. During climbout, the airplane was unable to climb. The PIC stated that the right engine had a power problem due to the low manifold pressure and he feathered the right propeller to arrest the airplane's descent rate. The airplane continued to descend, and the dual student made the forced landing on rough terrain. Examination of the spark plugs revealed that the engines were operating with an excessively rich mixture. The density altitude was 5,560 feet. This was the dual student's first flight in a Piper PA-31.
HISTORY OF FLIGHT On August 6, 1995, at 1150 mountain daylight time, N9111Y, a Piper PA-31, operated by H & H Aviation, Inc., collided with terrain during an emergency landing after takeoff from Boise, Idaho, and was substantially damaged. The emergency landing was precipitated by a partial loss of engine power during initial climb. Both pilots, the sole occupants, were not injured. The instructional flight was conducted under 14 CFR 91. The flight was conducted so that the chief pilot, who was acting as the pilot-in-command (PIC), could provide instruction to the commercial pilot (dual student) so that the dual student could fulfill 14 CFR 135 training requirements in a specific type of airplane. According to the PIC in a written statement to the Safety Board dated August 7, 1995, no problems were noted with the preflight inspection, engine start-up, taxi, engine run-up, and initial takeoff run. During the initial climbout, the PIC noticed that the climb rate "went down to zero" about 500 feet above ground level (agl). The PIC "sensed something wrong" and elected to turn downwind, advising the control tower that they was returning for landing. The airplane was unable to maintain altitude and the PIC attempted to identify the problem. He stated that "the right engine had a power problem due to the low manifold pressure." He stated that he verified this by moving the right throttle back and forth. The PIC then feathered the right engine in order to arrest the airplane's descent rate, but to no avail. The PIC had the dual student perform a forced landing. The landing gear was retracted and the wing flaps were partially extended. According to the dual student, in a written statement to the Safety Board dated August 7, 1995, no problems were noted with the preflight inspection, engine start-up, taxi, engine run-up, and initial takeoff run. During climbout, the dual student noticed that the airspeed was five miles per hour below the minimum controllable airspeed and the airplane was not climbing. He told this to the PIC, and the PIC "edged" both throttles forward with no effect on aircraft performance. The dual student stated: While turning [back to land on the runway], I tried to identify the inoperative engine, but there was no adverse yaw. I then started looking for the manifold pressure gauge and tachometers in an attempt to identify the failed engine through engine instruments. I could not immediately find them and returned my scan to the airspeed.... I found the task of searching for engine instruments in [an airplane] that I was completely unfamiliar with to be [too] much of a distraction from airspeed and directional control. I then yelled [to the PIC]..."...figure out this engine problem. I can't find the engine instruments." then concentrated my efforts on maintaining aircraft control and turned toward an open field south of the airport which was free of obstructions. A few moments later, [the PIC] feathered the right engine. There was no yaw as a result of feathering the engine, only a slight reduction in thrust and further increase in the descent rate. The dual student also stated that he continued to fly the airplane, and called out for flaps to be extended for the forced landing. Ground witnesses (statements attached) observed black smoke coming from the right engine and heard unusual engine noises just prior to the forced landing. The dual student later contacted the Safety Board with additional information regarding the flight. He stated that the PIC had flown the accident airplane earlier in the day, and that the PIC reported that "it ran great," but needed "some adjustments" with the engines. Upon this request, the Director of Maintenance, went out to the airplane to perform the adjustments. The dual student observed the Director of Maintenance spend about 15 to 20 minutes at each engine. During that time, the Director of Maintenance spent about five minutes to uncowl the engine, 10 minutes to "make adjustments" on the engine, and another five minutes to put the engine cowl back on. It was the dual student's understanding at the time that the Director of Maintenance was attempting to "match up the fuel flows" on both engines. After observing the Director of Maintenance complete the engine adjustments, the dual student began to preflight the accident airplane, with the PIC "showing me the finer points" of the airplane. After the forced landing, the dual student heard the PIC say "[the Director of Maintenance] must be trying to kill me!" The dual student then observed the Director of Maintenance arrive at the accident site about 45 minutes after the accident. The dual student then left the accident site, and then returned. When he returned, he saw the Director of Maintenance bent over the right engine, and then put the cowling back on the right engine before FAA personnel arrived. The dual student stated that as he was about to prepare his statement of what happened in the accident, the PIC instructed him to answer questions related only to the accident flight, and to not elaborate on events which may have occurred prior to the flight. He further stated that most of the pilots and employees at H & H Aviation knew about the fuel mixture control unit adjustments prior to the accident flight, and that it was generally known throughout the airline that the adjustments caused the loss of power. When asked if he recalled if the engines were worked on prior to the accident flight, or if the fuel mixture control units were adjusted, the Director of Maintenance stated (statement attached) that he could not recall. He also stated that he did not know why both engines lost power, but the airplane "...always had engine related fuel problems." When the PIC was asked if he recalled if the engines were worked on prior to the accident flight, the PIC stated that he could not recall. He stated that the cause of the loss of engine power could have been fuel contamination. PERSONNEL INFORMATION The PIC, seated in the right front seat, age 35, held an airline transport pilot certificate and a certified flight instructor (CFI) certificate with ratings for single engine land, multiengine land, and instrument airplanes. He was the chief pilot of H & H Aviation. The PIC reported that he had logged a total of 3,925 flight hours, including 227 in type. The dual student, seated in the left front seat, age 32, held commercial pilot and CFI certificates, with ratings for single engine land, multiengine land, and instrument airplanes. He reported that he had logged a total of 1,550 hours, including 10 hours in type. The accident flight was his first flight in the Piper PA-31. AIRCRAFT INFORMATION An examination of the airplane's engine and airframe logbooks (excerpts attached), and the airplane's "squawk record", did not reveal any unresolved discrepancies prior to departure the day of the accident. The last entry in the right engine log book, dated July 24, 1995, read: "installed #2 position 9111Y replaced controllers and fuel servo with recertified units. Run up ops [checked] normal. Returned to service." METEOROLOGICAL INFORMATION The recorded temperature at the departure airport about the time of the accident was 87 degrees F. The field elevation is 2,858 feet above mean sea level. Calculations performed by the Safety Board yielded a density altitude of about 5,560 feet msl at field elevation. WRECKAGE AND IMPACT INFORMATION The airplane wreckage was examined at the accident site on the day of the accident by an FAA aviation safety inspector from Boise, Idaho. An additional examination occurred on August 11, 1995, after the wreckage had been moved to a hangar. According to the FAA inspector, the underside of the fuselage was deformed and punctured. Usable fuel was found on board the airplane, and no evidence of fuel contamination was found. Sparkplugs from both engines were removed and examined. According to the inspector (statement attached), the examination revealed "...evidence of a rich running engine; indicated by heavy soot and fuel/oil deposits on electrodes...." An examination of the airframe, systems and engines by the inspector did not reveal evidence of preimpact mechanical malfunctions.
improper adjustment of the engine fuel control units by company maintenance personnel which led to excessive fuel flow and subsequent partial loss of engine power. Factors contributing to the accident were the rough terrain and high density altitude.
Source: NTSB Aviation Accident Database
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