Double-fatal crash of IAI Westwind 1124

YUKON, OKLAHOMA — On March 18, 2019, at 1531 central daylight time, an Israel Aircraft Industries Westwind 1124, registration N4MH, impacted terrain near the east side of runway 18 at Sundance Airport (HSD), Yukon, Oklahoma. As the airplane approached the approach-end of runway 18, it began to climb, rolled left, and became inverted before impacting terrain. The airplane was destroyed. Both pilots sustained fatal injuries.

The airplane was registered to and operated by Sundance Airport FBO LLC under Title 14 Code of Federal Regulations Part 91. The flight was operating on an instrument rules flight plan. Visual meteorological conditions prevailed at the time of the accident. The flight departed from Northwest Florida Beaches International Airport (ECP), Panama City, Florida and was destined to HSD.

The airplane was located about 1,472 feet down and 209 feet east of runway 18. The landing gear and wing flaps were extended. The left thrust reverser was unlatched and open and the right thrust reverser was closed and latched. The thrust reverser controls were in the stowed position; the aircraft was not equipped with a nose landing gear ground contact switch to preclude in-flight operation of the thrust reversers. A 1977 IAI Service Letter provided instructions for the removal of the nose gear contact switch, at the aircraft owner's discretion.

Electrical testing of the thrust reverser left and right stow micro-switches within the cockpit throttle quadrant revealed the left stow switch did not operate within design specifications. Disassembly of the left and right stow switch revealed evidence of arc wear due to aging.

The chief pilot for N4MH had reported a thrust reverser problem several weeks prior to the accident of N4MH to a fellow mechanic who held an inspection authorization, was a mechanic at Tinker Air Force Base, and worked as a mechanic at a warbird museum in Oklahoma City.

It was also reported that there had been an uncommanded thrust reverser deployment in N4MH during a night taxi in Florida. Mark Jernigan, who served as second-in-command in N4MH, had reportedly witnessed "issues" with the thrust reversers.

The left seat pilot was unbuckled except for one strap that was connected to the unguarded rotary buckle. The unbuckled straps were not torn, and the unbuckled strap metal latches were not deformed or torn through. Testing of the buckle was performed by holding two straps inserted into the buckle and striking the buckle's backside against a concrete floor. After several strikes, one of the belts became unlatched from the buckle.

The airplane was equipped with a cockpit voice recorder (CVR); however, the accident flight was not recorded. The audio on the CVR indicated the last events recorded were from 2007.

Investigatory material from this accident and related material from another Westwind accident can be found at https://rwp.yt/iai.