WHAT WE KNOW

The accident happened approximately 20 miles west of the Nampa airport in the foothills of the Owhyee Mountain Range, early in the afternoon of May 30th. The clouds were starting to break up and it was going to be a routine pleasure and demonstration flight. The aircraft hit the ground at a relatively high rate of speed at about a 45 degree angle and right wing low. The flaps and gear were up and trim was set for cruise. The wreckage was confined to an area about 175 feet long from the point of impact.

N151TM had accumulated over 450 hours of flight time prior to the accident. Pilot Dale Clark, 54, was a highly experienced warbird pilot with over 200 hours in the Thunder Mustang. He held a low-level aerobatic waiver and a Commercial license and had flown the Thunder Mustang at several recent airshows. Passenger John Whitney, 69, was also an experienced pilot and held a Private license.

Because the Electronic Control Units (ECU's), which are small computers that manage the engine, we know that the engine was running and the parameters of its performance prior to impact. These ECU's, one for each bank of 6 cylinders, are also designed to retain data. This data is recorded in one second intervals and records such things as rpm, manifold pressure, voltage, temperature, throttle position and fuel flow. When the NTSB had this data down loaded and graphed from these ECU's, each unit verified the other and the engine's performance. In addition, the data at impact from the recovered Vision Micro Systems engine monitoring system verified the ECU data.

NTSB investigators completely disassembled the engine, gearbox, accessories and related components finding no signs of pre-impact malfunction or failure. Also, the ECU's indicated the engine was operating at near idle for one minute and 40 seconds prior to going to full throttle 9 seconds before before impact. Power was then reduced to idle 4 seconds before impact. This ECU data corroborates eyewitness reports of backfiring noises followed by the engine revving up prior to the accident. The engine's short exhaust stacks and slightly rich idle mixture produce a characteristic popping sound for several seconds whenever power is reduced to idle (just like the North American version). Contrary to initial speculation, the engine was operating normally at the time of the accident.

Investigators also performed a reconstructive mock-up of the airframe. The aircraft structure and associated systems were inspected for any signs of pre-impact anomaly, malfunction, interference or failure. None were found.

Papa-51 will continue to press forward with the Thunder Mustang program. It is a well designed, well engineered aircraft that has a place in today's aviation industry. The Falconer V12 is a significant powerplant that embodies the technology that has given birth to this airplane. The company's goal is to get the #2 Thunder Mustang, which is the first production kit, flying next month and continue with the program as planned.

We will have a substantial Thunder Mustang display at Oshkosh, but not a flying model. PaPa-51 has decided to make sure that this first production kit is finished and flying for the Reno Air Races. It is being set up in the stock configuration, naturally aspirated, with no supercharger.

Papa-51 continues to sell, produce, and deliver Thunder Mustang kits. Investor loyalty in the company and customer confidence remain strong.

Previous Reports

• 06/02/98

• 06/10/98

• 06/24/98

AAFO will update this story as more facts become available.

Special thanks to Tom Giertz for providing this update.

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