What happened
On August 21, 2023, an Israel Aircraft Industries 1125 Westwind Astra, registration N39TT, was involved in an accident near Wheeling, Illinois. The aircraft was operating as a positioning flight under Part 91 regulations.
During the landing at Chicago Executive Airport, the flight crew reported that the aircraft touched down within the touchdown zone on runway 1s. The pilot attempted to apply the brakes and deploy the thrust reversers, but reported that the brakes "were not grabbing." After both the pilot and co-pilot were unable to achieve effective braking through the standard pedals, the pilot applied the emergency brake handle.
In an attempt to increase stopping distance, the pilot used the nose wheel tiller to steer the aircraft onto taxiway D. However, due to the aircraft's momentum, the plane slid off the taxiway and into the adjacent grass. The impact caused the right main landing gear to collapse and resulted in substantial damage to the right wing spar. The crew was not injured.
The investigation
Investigators examined several components, including the anti-skid control box, anti-skid control valves, wheel speed transducers, and the brake power valve. These tests revealed no anomalies that would have caused a loss of braking performance. Maintenance tests performed on the airbrake system also showed no malfunctions in either air or ground modes.
Data from the Honeywell N1 Digital Electronic Engine Control (DEEC) indicated that the engines were operating normally and did not show evidence of thrust reverser deployment during the landing sequence. While landing simulations confirmed reduced deceleration during the roll, they could not determine if the ground airbrakes were stowed or deployed, nor could they identify the specific cause of the reduced friction. Tire skid marks on the runway and taxiway confirmed that heavy braking had been applied.
Findings
- The aircraft experienced a loss of braking effectiveness during the landing roll.
- The aircraft's right main landing gear collapsed during the excursion.
- The cause of the reduced braking effectiveness could not be determined from the available mechanical evidence or flight data.