The US Federal Aviation Administration is giving operators of Bombardier CRJ100/200 regional jets until early October to update flight manuals and operations and training procedures to deal with potential flap failures. Carriers will have until early January to carry out associated preventative maintenance actions.
The airworthiness directive (AD), issued last week, is an interim measure aimed at stemming a large number of stuck flap incidents that have been linked to cold weather operations with the Canadian-made twinjets.
"The [CRJ] airplanes have had a history of flap failures at various positions for several years," says the FAA. "Flap failure may result in a significant increase in required landing distances [if stuck in the stowed position] and higher fuel consumption than planned during a diversion [if deployed]."
In the most noteworthy case, an Air Canada Jazz CRJ200ER on approach to Prince George, British Columbia on 21 November aborted its landing because of the weather.
The flaps, set at 45° for landing, would not retract despite the crew's attempts to recycle the flap circuit breakers. The pilots ultimately diverted to Fort St John, British Columbia, where they landed with 232kg (512lb) of fuel remaining due to the additional drag from the lowered flaps. The CRJ burns about 1,360kg an hour at cruise.
Before that incident, air safety investigators in Canada who had been researching the CRJ flap problems for a decade had convinced themselves the problems were more of a nuisance than a safety concern.
Real Levasseur, chief of operations for air investigation for the Transportation Safety Board, says that the board sent a letter to Transport Canada "indicating our concerns" over the flap problems.
Levasseur says the rate of occurrences has been increasing year over year, with two to three incidents a day in the worldwide fleet last winter, although concerns for safety did not arise until the Jazz incident.
An incident typically involves a "disagree" between matching sets of the four individually controlled flap panels, a situation that causes the aircraft's safety logic to lock the flaps in their current position to avoid roll control problems for the pilots. Levasseur says unlocking the flaps can only occur after the aircraft has landed.
Under the FAA's directive, which was derived from a Transport Canada AD, US operators of the aircraft must modify the flight manual to discuss possible fuel exhaustion if the flaps fail "at other than 0e_SDgr" in combination with a diversion to another airport.
Operational procedures must be modified to cover three failure scenarios - flap extended diversion, flap failure after take-off, flap zero landing, and training must include the three failure scenarios, plus landing, with less than full flaps settings.
Maintenance actions, to be performed within 120 days of the 5 September effective date of the AD, include cleaning and lubricating the flexible shafts that drive the flaps and performing a detailed inspection of the actuator connector sealant bead for signs of damage or delamination, among other tasks.
The FAA in the AD says the actions are necessary "to improve overall flaps system reliability and bring the failure rate to an acceptable level, until permanent solutions are implemented".
Source: Flight International
