N155TPAermacchi IMPALA MB-326M · 1967

On March 5, 2021, about 1010 Pacific standard time, an Aermacchi Impala MB-326M, N155TP, was destroyed when it was involved in an accident near Edwards, California. The flight instructor sustained serious injuries, and the pilot receiving instruction sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.

According to the operator, the National Test Pilot School (NTPS), the purpose of the flight in the light military jet trainer was spin data collection. The flight instructor reported that several maneuvers, including an inverted left spin, were conducted before the accident invertedleftspin maneuver. Upon entry into the spin, the airplane behaved normally through three revolutions. He noticed a steepening spin attitude and an increasing spin rate and directed the pilot receiving instruction to recover from the spin by stating, “recover, recover.” The pilot replied, “I’m trying.” The instructor looked down at the flight controls, and it appeared that the flight control stick was in the aft position, and the right rudder pedal was depressed. The spin rate started to incapacitate him, and it became clear that the pilot could not recover.

The flight instructor assumed control of the airplane and attempted a recovery input. However, the spin rate was increasing with a corresponding increase in negative G forces, which pushed him out of his seat. He was able to touch the right rudder with his toes but was not able to apply sufficient right rudder control input to recover from the spin. Unable to recover and reaching the ejection decision altitude, he directed ejection by saying, “eject, eject, eject.” The pilot departed the airplane after the second ‘eject’ call. The spin rate continued to increase along with the negative G forces. Verifying that the pilot was clear of the airplane, the flight instructor pulled his ejection handle. As he was being partially thrown out of the seat by the negative G forces, the seat impacted into his buttocks when the rocket catapult fired, resulting in a significant spinal fracture. The flight instructor’s subsequent descent and landing under the parachute occurred normally.

The pilot receiving instruction reported that before the accident maneuver, 12 uneventful flight maneuvers were performed. While preparing to conduct the accident maneuver, they climbed to an altitude of about 22,000 ft mean sea level (msl). The power was set to idle, and a pitch-up motion was initiated. As the airplane entered the stall, he applied full left rudder and moved the flight control stick full forward and to the right. The airplane entered a left inverted spin. While looking forward at the horizon, he maintained the flight control positions during three spin revolutions then applied right rudder and moved the stick to the center and full aft to recover. After two more spin rotations, the airplane was not showing any sign of recovery, and he repositioned the stick to the neutral position. The flight instructor then took control of the airplane and attempted to recover. He heard a call from the telemetry room of “15,000 ft.” He then looked at the altimeter and called out “13,000 ft” and “12,000 ft.” The flight instructor then ordered an ejection. At the second ‘eject’ call, he pulled the lower ejection handle. His subsequent descent and landing under the parachute occurred normally. The airplane descended to ground impact, and a postimpact fire erupted.

The pilot receiving instruction reviewed the events of the accident flight with the NTPS chief pilot on a subsequent date. While seated in the same type of airplane, he realized that the clearance between his shins and the instrument panel was rather small. While seated normally, he was able to move the rudder pedals to the full left and right deflection. However, when he placed a cushion between himself and the seat (which simulated a negative G scenario), the distance between his shins and the instrument panel was reduced. The reduction of space allowed his shins to contact the instrument panel, which restricted his movement of the rudder pedals. Contact between his feet and the rudder pedals was accomplished only with his toes.

Motion of the rudder was tested in that configuration, and the rudder moved only a few centimeters in either direction. When the rudder was depressed to the left, he was unable to move it right to more than the neutral position. This test was performed with the same type of equipment as the accident flight, but the pilot was not wearing a G-suit and ejection seat leg restraining straps. While seated in the airplane, the pilot receiving instruction recalled that he had difficulties applying full rudder deflection during the recovery of both inverted spins on the day of the accident. Due to his shins contacting the instrument panel, he was only able to use his toes to move the rudder pedals while recovering the airplane.

The pilot receiving instruction further reported that his left leg (tibia and left foot) was injured during the accident. His flight suit’s lower left leg was torn, and there was scuffing on his left boot. He stated that he did not know how the injury was sustained but speculated that he was too tall for the airplane and that his left leg impacted the instrument panel during the ejection sequence.

Postaccident examination of the airplane by a Federal Aviation Administration inspector revealed that all flight control surfaces were present. The flight control system sustained extensive impact and thermal damage. The examination did not reveal evidence of any mechanical anomalies that would have precluded normal operation.

The airplane was equipped with Quasonix, a multimode telemetry transmitter. The transmitted data were recorded at the NTPS flight operations center and provided to the National Transportation Safety Board. The data for the accident maneuver showed the entry to a spin maneuver at 1005:00. The rudder position peaked at nearly 100% right near the entry to the maneuver, and heading change showed the airplane was established in a developed spin. The rudder deflection throughout the spin varied showing movement in both directions but in general was recorded as lesser values than in previous spins during the accident flight. At 1005:46, about 10,730 ft msl, the value for vertical stabilizer strain gauge force aligned with values for rudder deflection. Due to data dropouts, it was not possible to determine the flight condition of the airplane after the time of likely ejection.