The US Federal Aviation Administration has issued two near-term airworthiness directives for three types of Cessna Citation aircraft to correct workmanship or design issues that could cause safety hazards.
The regulator is mandating that operators of hundreds of Citation Ultras and Citation V aircraft install new minimum airspeed placards in the aircraft by 30 November and make changes to the flight manual, including procedures for recognising and recovering from an inadvertent stall.
The action comes after the FAA analysed the stall warning systems of five in-service Citation Model 560s in the wake of a fatal February 2005 loss-of-control crash of a Cessna Citation V in icing conditions on the approach to Pueblo, Colorado.
The National Transportation Safety Board places primary responsibility for the crash on the pilots for allowing the airspeed to decrease far below target levels and not activating the aircraft´s de-icing equipment on final approach.
The NTSB also calls on the FAA to require modifications to the Cessna 560´s stall warning system to provide more pre-stall warning in a wider range of icing conditions.
The FAA in its investigation found that all five of the Citation Vs it examined "exhibited an out-of-tolerance condition with respect to the margin between the stall warning and pre-stall roll-off," according to the AD.
Further, the regulator says the stall warning system on two of the aircraft did not provide adequate airspeed margin between the stall warning and stall.
The FAA also says it may later require a functional test of the aircraft´s angle-of-attack system to adjust calibration settings. Cessna has not yet responded to a request from Flight International for more information.
Operators of the first 13 Cessna CJ3s will have until 19 December to modify their aircraft with electrical power relay circuit protection, in part to correct faults in the original design of the electrical system, but also to mend a 10 January Cessna service bulletin aimed at fixing the problem.
According to the FAA, the original service bulletin had "incorrect alteration instructions" that caused a CJ3 to experience an in-flight "loss of numerous systems, lose numerous systems, tripped circuit breakers, and burned wiring adjacent to the power distribution panel".
The AD calls for operators to incorporate fixes called out in Cessna´s revised service bulletin within 30 days or 10h in service from 19 December.