ERA24FA157

The flight instructor’s failure to maintain control of the multiengine airplane after a partial loss of engine power on one engine during a go-around, which resulted in an aerodynamic stall. Contributing to the accident was the mechanic’s failure to check the condition/security of the right engine’s carburetor throttle arm linkage during the annual inspection, which resulted in a partial loss of engine power.

The flight instructor and the pilot receiving instruction were practicing a simulated engine-out instrument approach with the left engine operating and the right engine at a reduced power setting. The approach terminated in a missed approach/go-around. According to the pilot receiving instruction, when he added power to go around, the airplane did not respond with the engine power commanded. He turned the airplane to the missed approach heading provided by air traffic control (ATC), and the flight instructor took control of the airplane, declared an emergency, and told ATC they were “single engine.” The flight instructor continued to turn the airplane to the right in an attempt to return to the runway; however, the airplane continued to lose altitude, stalled, and impacted the ground on airport property. Although the pilot receiving instruction perceived that there was no thrust on either engine, data recovered from the airplane’s Avidyne multifunction display (MFD) and primary flight display (PFD) revealed that the left engine was producing full power and the right engine was producing partial power from the time the go-around was initiated to the time of impact. Examination of the right engine revealed that the interlocking teeth of the serrated mating surfaces between the carburetor’s throttle arm and throttle control lever were not securely mated, such that the throttle control lever was loose and could be fully rotated without moving the throttle arm. The teeth on the throttle control lever side were rounded and worn down, consistent with the damage having occurred over a period of time. As such, when the right engine’s throttle was advanced to go around, the worn mating surface of throttle control lever likely did not engage with the mating surface on the carburetor throttle arm (to actuate the valve assembly in the carburetor), which prevented the right engine from obtaining full power. The right engine had undergone an annual inspection the day before the accident, as required by 14 Code of Federal Regulations (CFR) Part 91.409. Per the regulation, such inspections must be performed in accordance with 14 CFR Part 43 and the aircraft approved for return to service by an authorized certificated mechanic. Part 43, Appendix D, paragraph (d)(6) explicitly mandates the inspection of the engine controls for “defects, improper travel, and improper safetying.” The mechanic who endorsed the engine logbook for the inspection said that he thought he checked the security of the throttle arm during his inspection. He also said he understood that a loose and damaged throttle control component could result in a partial loss of engine power and that he was unsure how he missed it in his inspection. Therefore, due to the fact that the throttle control lever was loose and its serrated mating surface exhibited pre-existing damage, it is likely that the mechanic failed to properly check the security of the throttle control lever to the throttle arm when he inspected the engine. The flight instructor was teaching single-engine emergency procedures; however, her actions were inconsistent with her being prepared to handle the partial loss of engine power on one engine after the initiation of the go-around. Per the pilot receiving instruction, the emergency checklist was never used, and the airplane was not configured to maintain flight. As a result, during the flight instructor’s attempted continuation of the go-around, the airplane’s airspeed decayed, and it stalled at a critically low altitude from which it was not possible to recover before ground impact.

HISTORY OF FLIGHT On March 30, 2024, at 1320 eastern daylight time, a twin-engine Piper PA-44-180 airplane, N595ND, sustained substantial damage when it was involved in an accident at the Treasure Coast International Airport (FPR), Fort Pierce, Florida. The flight instructor was fatally injured, and the pilot receiving instruction was seriously injured. The airplane was operated as a 14 CFR Part 91 instructional flight. Flight and engine performance data recovered from the airplane’s PFD and MFD showed that the airplane departed from FPR at 1239:30. According to the pilot receiving instruction, he and the flight instructor climbed the airplane to 5,000 ft mean sea level (msl), where they practiced single-engine emergency procedures. These procedures included shutting down and feathering the right engine. Recovered PFD and MFD data showed that, between 1247 and 1251, the recorded parameters for the right engine were consistent with it having been shut down. The pilot receiving instruction stated that they subsequently returned to FPR to practice a single-engine instrument approach, and ATC cleared them for the ILS or LOC RWY 10 approach. He said that, to simulate the engine failure, thrust on the right engine was reduced, and the left engine was operated normally. Recovered PFD and MFD data showed that the airplane began descending at 1256:47. At 1308:39, the airplane was at 2,824 ft pressure altitude, both engines were operating at 2,380 rpm, and the fuel flow for the left and right engines was 9 and 10.7 gallons per hour (gph), respectively. (Maximum speed for the engine model is normally about 2,700 rpm, and target idle speed is about 700 rpm.) The data showed that, as the airplane continued to descend on a long approach toward runway 10R, the right engine’s rpm continued to decrease, and the left engine’s speed was increased to and maintained about 2,700 rpm for the remainder of the flight. The pilot receiving instruction said that, when the airplane was at 1,000 ft msl, he extended the landing gear and brought the mixture and propeller levers for both engines full forward. When the airplane reached the decision height for the approach (250 ft above ground level), he initiated a missed approach. He brought both throttles full forward to go-around, but there was “no thrust on either engine.” He then turned right to the missed approach heading provided by ATC. He said that the instructor “realized there was no engine power” and took control of the airplane, declared an emergency, and continued to turn the airplane to the right to try to land on runway 14. Recovered PFD and MFD data showed that, at 1318:09, the right engine was operating at 1,220 rpm with a fuel flow 3.1 gph, and the left engine was at 2,670 rpm and 15.8 gph. About 12 seconds later (when the airplane was on short final approach to runway 10R), the right engine speed and fuel flow increased briefly to 1,280 rpm and 11 gph, respectively, and the left engine was operating at 2,670 rpm and 16.5 gph, before the data ended at 1319:33 (MFD), and 1319:52 (PFD), about 500 ft from where the airplane impacted the ground and came to rest. A review of ATC communications revealed that at 1319, the flight instructor contacted the FPR ATC tower and stated that they wanted to return to the traffic pattern. She said they were “single engine” with two souls on board. A controller asked the instructor if she was declaring an emergency, and she said yes. The controller then cleared the airplane to land on runway 10R followed by a clearance to land on any runway. There were no further communications with the airplane. According to the pilot receiving instruction, neither he nor the flight instructor had time to use the emergency checklist or feather the engine. He said that he was focused on the emergency and that the flight instructor was hoping to get engine power restored. He did not look at the engine gauges and could not recall the flap setting. ATC tower personnel reported they saw the airplane make a low-level “tight right downwind” back to runway 14. As the airplane approached the modified midfield right downwind for runway 14, the airplane attempted to turn toward the runway but continued to lose altitude and went nose-down into the ramp west of runway 14. ADS-B data for the last minute of the flight showed a flight track consistent with the ATC tower personnel’s description (see figure 1). Figure 1. ADS-B flight track data for the last minute of the flight. (Inset shows time, altitude, and ground speed for each numbered data point.) A witness sitting in a parked airplane near taxiway echo observed the accident airplane in a “moderate” right bank turn at a “slow speed heading in our direction.” The airplane appeared to stall, then rolled right inverted and impacted the ground. The witness said the engine power “sounded normal for this aircraft type at the time of [the] stall.” Another witness said the airplane was in a steep right bank and losing altitude before it impacted the ground. PILOT INFORMATION The flight instructor held a commercial pilot certificate with ratings for single-engine land, multi-engine land, and instrument airplanes. She also held a flight instructor certificate with ratings for single- and multi-engine land airplanes. The flight instructor held a current first-class FAA medical certificate with no limitations. A review of her pilot logbook revealed she had about 1,395 total flight hours, of which about 180 hours were in the same make/model as the accident airplane. The pilot receiving instruction held a private pilot certificate with ratings for airplane single-engine land and instrument airplanes. He held a current first-class FAA medical certificate with no limitations. A review of his pilot logbook revealed he had about 224 total flight hours, of which about 2.8 hours were in the same make/model as the accident airplane. AIRPLANE INFORMATION The Piper PA-44-180 is a four-seat, multi-engine airplane widely used for pilot training. The airplane was powered by two 180-horsepower Lycoming engines that were adapted to rotate in opposite directions. The left engine (O-360-A1H6) had a right rotation and the right engine (LO-360-A1H6) had a left rotation. This adaptation, which results in counter-rotating propellers, is designed to improve single-engine handling performance in the event of an engine failure. The airplane’s pilot operating handbook (POH) contained a warning that a one-engine inoperative GO-AROUND “should be avoided if at all possible.” The emergency checklist for a one-engine inoperative go-around and a summary of factors that would reduce climb performance stated, “WARNING – The propeller on the inoperative engine must be feathered, the landing gear retracted, and the wing flaps retracted for continued flight.” A review of the airplane’s maintenance records revealed that the last annual inspection was completed the day before the accident on March 29, 2024. At that time, the total airframe time in service was 6,980 hours. Total time since overhaul for both engines was 196 hours. The annual inspection was performed by two mechanics employed by the flight school, and the inspection was endorsed by the flight school’s director of maintenance (DOM). According to the DOM, he was the only person authorized to endorse annual inspections at the flight school. WRECKAGE AND IMPACT INFORMATION The airplane came to rest inverted on the airport’s tarmac. There was no postimpact fire. All major components of the airplane were located at the accident scene. The flaps were retracted, and the landing gear were fully extended. Flight control continuity was established for all major flight controls to the cockpit area. Both wing fuel tanks were breached from impact. Continuity of the fuel system was confirmed to both engines. Left Engine and Accessories The left engine remained attached to the a