The FAA today issued an immediate airworthiness directive (AD) that will bar Cirrus SR22s from flight into known icing from 19 December, pending an inspection and potential rework of portions of the aircraft's TKS anti-icing system.
The agency approved the four-seat low-wing plane for flight into known icing (FIKI) in January, after which.approximately 75 FIKI-equipped aircraft have been delivered. EASA approved the feature for European-registered SR22s earlier this month.
Cirrus says it discovered the issue during a recent quality assurance inspection at its Duluth manufacturing plant, finding that some compression fittings on the anti-ice fluid distribution lines may have been improperly installed. Changes have already been made to the production line as of early November.
Schematic of SR22 anti-icing system plumbing (courtesy of Cirrus)
The airframer offers FIKI as a $24,500 upgrade to the basic SR22.
If the lines separate in flight, the system could leak its glycol-based TKS fluid, leaving the aircraft with potentially no anti-icing protection on wing, windshield, propeller and horizontal and vertical stabilizer leading edges. With no ice protection, the FAA says ice could build on the airplane "and degrade the handling qualities and performance".
The FIKI option includes a second 15-litre TKS reservoir in the right wing, longer titanium leading edge cuffs chord-wise with more holes, a cuff for the vertical stab, backup pump and additional stall protection monitoring.
Cirrus on 9 November issued a mandatory service bulletin to owners detailing the problem as well as instructions for inspecting and correcting improperly crimped connections. The company asked owners to perform the inspection, which takes about 10h, at the next schedule maintenance event or annual inspection event for the aircraft, or within 100 flight hours of the 9 November notification, whichever occurs first.
"Until the Service Bulletin is complied with, the operator is advised that Flight Into Known Icing (FIKI) conditions is prohibited," says Cirrus in the SB, a recommendation the FAA repeated in the immediate airworthiness directive (AD) issued today. "If the airplane encounters icing conditions, immediately exit conditions by changing altitude, turning back, or if clear air is known to be immediately ahead, continue on course," says Cirrus.The FAA mirrored Cirrus' compliance dates in its AD.