Wendover, UT, USA
N4837T
PIPER PA28R
The pilot said that after takeoff he was unable to retract the landing gear, and at about the same time perceived a loss of engine power output. The pilot then set the mixture control to full rich and leveled the airplane. When attempts to retract the landing gear were unsuccessful, the pilot elected to make an emergency landing on an interstate highway. During the landing the airplane’s left wing impacted the left side of a tractor-trailer truck, which resulted in substantial damage to the airplane. The engine was test run 3 separate times during a post accident examination and no anomalies were noted that would have precluded normal operation. The airplane was equipped with a landing gear back-up actuator override mechanism, which prevents landing gear retraction at airspeeds below approximately 85 miles per hour (mph); this airspeed increases with power reduction and/or altitude increase. Density altitude at the time of the accident was calculated to be 6,946 feet, which according to Piper Aircraft, would have required an additional 6 miles per hour to be added to the 85 mph to affect a normal gear retraction. The system incorporates a manual override emergency gear lever that in the raised position allows the landing gear position to be controlled by the landing gear selector switch regardless of airspeed and power combinations. A post accident examination of the override system revealed no anomalies that would have precluded normal operation. When asked if he had used the system prior to the emergency landing, the pilot said he had not. The pilot’s failure to attain and maintain an airspeed sufficient to affect a normal landing gear retraction, as well as his failure to utilize the airplane’s emergency landing gear override system, collectively contributed to his decision to make an emergency landing. The pilot’s perceived loss of engine power was most probably due to the degraded engine performance as a direct result of positioning the mixture control from an optimal lean position to the full rich position in a high density altitude environment. The pilot could have mitigated the event had he elected to initially use the manual override system, which would have resulted in a normal gear retraction regardless of airspeed and altitude.
On August 26, 2009, about 1835 mountain daylight time, a Piper PA-28R-200, N4837T, was substantially damaged following a forced landing and subsequent impact with a tractor-trailer near Wendover, Utah. The private pilot, his two passengers and the tractor-trailer driver were not injured. Visual meteorological conditions prevailed for the planned cross-country flight, which was being conducted in accordance with 14 Code of Federal Regulations (CFR) Part 91, and a flight plan was not filed. The flight departed the Wendover Airport (ENV), about 1830, and was destined for the Salt Lake City International Airport (SLC), Salt Lake City, Utah. In a statement submitted to the NTSB investigator-in-charge (IIC), the pilot reported that after taking off and accelerating to 95 miles per hour (mph), he selected the landing gear up but noticed that the landing gear did not retract. The pilot stated “…then I noticed that the engine was not producing enough power. I knew we had a power plant failure.” The pilot reported that the aircraft’s performance “was not the same” and he immediately pushed the mixture in to full rich and leveled the airplane. The pilot further reported that he then started to troubleshoot the landing gear problem by putting the gear lever down, then attempting to retract the gear again, but with no luck. The pilot stated that he then checked the [circuit] breakers on the right side of the panel and noticed that two had popped out after cycling the gear [selector handle] a second time. The pilot stated, “I pushed the breakers in and gave enough time to see if they [would] pop out again. Then at the same time I started to look for an emergency landing place. I knew it was just a matter of time [until] we would completely lose power. I put the gear up again and watch[ed] the light. [They were the] same. I then looked outside with the gear lever being up and saw the shadow of the airplane. The main wheels were still out and the yellow and red warning light[s] still on.” The pilot reported that thinking he had an engine problem, he would make and emergency landing on the eastbound lanes of an interstate highway he was close to. The pilot stated that during the landing attempt the airplane’s left wing impacted the top of a tractor-trailer truck, which caused the airplane to yaw to the left before falling to the pavement. The airplane came to rest upright facing west in the right hand lane of the two-lane eastbound interstate highway. The airplane sustained substantial damage to its left wing. The left main landing gear had collapsed, while the nose gear and right main landing gear remained extended and not damaged. A review of the airplane’s Pilot’s Operating Manual (POM), Description-Airplane and Systems, Landing Gear, revised January 31, 1987, revealed that the airplane was equipped with a pressure sensing device to automatically lower the gear, regardless of gear selector position and at airspeeds varying from approximately 85 mph to 105 mph, depending upon propeller setting and altitude. The devise also prevents gear retraction, regardless of the gear selector position, at airspeeds below approximately 85 mph with full power; this airspeed increases with power reduction and/or altitude increase. A manual override of the device is provided by an emergency gear lever located between the front seats and to the left of the flap handle. The emergency gear lever, when held in the raised position, can be used to override the system, and gear position is then controlled by the selector switch, regardless of airspeed and/or power combinations. The emergency gear lever is provided with a latching device, which may be used to lock the override lever in the UP position. On March 4, 1988, Piper Aircraft issued Service Bulletin No. 866A, which allows operators of aircraft equipped with Emergency Gear Lever Override System to either remove the system or review and understand all of the information contained in the applicable airplane Flight Manual/Pilot's Operating Handbook pertaining to the normal and emergency operation of the system. Piper Aircraft considers compliance with Service Bulletin No. 866A mandatory. When asked by the IIC if he was familiar with the Emergency Gear Lever Override System, the pilot said that he was. The pilot revealed to the IIC that he did not attempt to use the Emergency Gear Override System to retract the landing gear. At 1835, the ENV weather reporting facility, located about 4 nautical miles west of the accident site, reported wind 130 degrees at 7 knots, visibility 10 miles, sky clear, temperature 32 degrees Celsius, dew point 0 degrees Celsius, and an altimeter setting of 30.14 inches of Mercury. The density altitude (DA) at the time of the accident was computed to be 6,946 feet. In a conversation with the IIC relative to the effect density altitude would have on airspeed required to retract the landing gear in normal operations, a Piper Aircraft air safety investigator stated that if the emergency override system was not being used, the speed at which the gear would retract would increase 1 kt/mph per 1,000 feet of altitude above the base altitude of 1,000 feet msl. The investigator added, “I did not locate any graphs [or] charts.” When asked by the IIC, relative to the accident in question, if this would mean that 6 mph would be added for the computed density altitude of 7,000 feet, the investigator responded “Correct.” On September 15, 2009, under the supervision of a Federal Aviation Administration aviation safety inspector, two engine runs were performed. The inspector reported that the results of the first engine run revealed that the engine started easily and that the mixture was sensitive. The RPM was set at 2,400, with power increased to 20 inches of manifold pressure (MP), then increased to 25 inches of MP, with mixture adjusted to best performance. When the mixture was advanced the engine began to lose power, and when retarded toward idle cutoff the engine ran smooth. The inspector stated that the second engine run revealed that after the idle mixture was adjusted and the engine was started it ran smooth, but only after excessive leaning near idle cutoff position. The inspector reported that the engine was then run at 2,400 RPM and 20 inches of MP, then increased to 25 inches of MP, with the power holding. When the mixture was advanced to full rich the RPM began to drop from full power. The inspector stated that the accident scenario was then set up as a possible engine failure as described by the pilot, with the power full forward (25 inches MP), the propeller full forward (2,400 RPM), and the mixture full rich. The inspector stated then the engine began to lose RPM as soon as the mixture was advanced. On April 6, 2010, under the supervision of a FAA aviation safety inspector, the airplane’s Landing Gear Back-Up Actuator Override mechanism was examined. The inspector reported that as a result of his examination no anomalies were noted with the system that would have precluded normal operation. On May 6, 2010, under the supervision of the Safety Board IIC, the airplane’s fuel servo, model RSA-5AD1, serial number 39040, was flow tested at the facilities of Precision Airmotive LLC, Marysville, Washington. The results of the flow test revealed that no anomalies were noted with the servo component that would have precluded normal operation.
The failure of the pilot to attain and maintain an airspeed sufficient for normal landing gear retraction during initial climb. Contributing to the accident was the pilot's failure to use the airplane's manual override landing gear system, misidentifying that a total loss of engine power was imminent, positioning the mixture control to the full rich position, and the density altitude condition.
Source: NTSB Aviation Accident Database
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