GRAHAM WARWICK / WASHINGTON DC
Chowdry crash prompts tighter pilot and maintenance requirements for private operation of the military aircraft
The US Federal Aviation Administration is close to establishing tighter pilot and maintenance requirements for private operation of the Aero Vodochody L-39 jet trainer as investigators conclude that the January 2001 crash which killed Atlas Air chairman Michael Chowdry was the result of pilot error following the failure of the rear canopy.
With the number of L-39s in the USA expected to increase from 114 to over 200 as more aircraft are restored, the Czech-built trainer is the first of the jet "warbirds" to come under scrutiny as the FAA moves to standardise the maintenance of ex-military aircraft used in airshow displays. The FAA has issued a circular recommending an inspection programme for the L-39, and recently agreed to extend the comment period to 22 November after the L-39 community undertook to form a safety committee to act as a "single voice".
The L-39 is approved as an experimental exhibition aircraft, restricting its use primarily to air displays, associated cross-country flying and necessary proficiency flying. Without any product support from the original manufacturers of either the L-39 or its Ivchenko AI-25TL engine, the FAA wants maintenance standardised. Operators want relief from the original calendar-based life limits imposed by the manufacturer as the aircraft are relatively young for warbirds. "None would be flying if life limits were enforced," says Dave Clinton of the Experimental Aircraft Association's Warbirds division.
The Chowdry crash, in which rear-seat passenger Wall Street Journal journalist Jeff Cole was also killed, focused attention on the L-39. The aircraft stalled and crashed soon after take-off from Front Range Airport in Colorado on 24 January 2001. The US National Transportation Safety Board's final report says the probable cause was that Chowdry was distracted by the rear canopy's failure. Contributing factors were pilot fatigue, lack of recent experience in the L-39 and a centre of gravity that was further aft than recommended, making the aircraft more sensitive.
The NTSB says the rear transparency failed because of acrylic embrittlement, while damage indicated that the front and rear canopies were not properly latched. Canopy and ejection seat inspection is a particular focus of the FAA's advisory circular. Most L-39s on the US register are flown with the ejection seats deactivated because of the FAA's strict safety requirements, Clinton says.
Source: Flight International
