Air Tractor AT-502 agricultural aircraft must be inspected for wing cracks under an emergency airworthiness directive (AD) issued by the US Federal Aviation Administration.
The AD follows an accident involving an AT-502A in which the wing separated in flight because of fatigue cracking of the wing lower spar cap. A survey of AT-501, -502 and -502A models revealed similar cracking in two other aircraft, says the FAA.
The AD requires visual inspection of the lower spar cap at the wing centre splice within 10h if aircraft have accumulated 3,000h or 4,000h in service, depending on the model. More than 400 AT-500- series Air Tractors have been delivered since 1987. The FAA believes many of the aircraft affected by the AD are over the 3,000/4,000h service mark.
Repetitive inspections are required until operators incorporate a spar cap modification developed by Snow Engineering.
Source: Flight International
