The FAA revised some elements of an airworthiness directive first proposed in 2018 and applicable to Daher (formerly Quest) Kodiak 100s with a particular nose landing gear fork that has been known to crack.
The AD published July 13 as a final rule extended the repetitive inspection interval to 200 hours for aircraft that continue to fly with a “type A” nose landing gear (NLG) fork, part number 100-410-7001. Aircraft that have a “type B” NLG fork, part number 100-410-7013, installed do not require additional inspections.
Fatigue cracks known to have developed in the type A NLG fork can cause the nosewheel to separate, particularly when operating on unimproved runways, as Kodiaks often do, and that can cause the aircraft to overturn, the FAA noted in the final rule.
Replacing the NLG fork is estimated to cost $7,342 per affected aircraft. Inspecting the assembly for fatigue cracks using approved methods is estimated to cost $340 per inspection, with additional costs to inspect related equipment including the shimmy damper system. The FAA estimates that the AD affects 116 airplanes in the U.S. registry.
Operators and Quest Aircraft, the original owner of the type certificate (Daher purchased Quest, and the type certificate, in 2019), requested several changes to reduce the cost of compliance. The FAA agreed to extend the interval to 200 hours time-in-service, but found there is insufficient evidence to support a longer interval. The FAA also acknowledged concerns expressed by two operators about the cost of inspecting the assembly for fatigue cracks using fluorescent penetrant, dye penetrant, or eddy current inspection; however, the agency determined that the prescribed methods are the most cost-effective means of achieving safety.
“The dye penetrant kits are available from several sources,” the FAA noted. “Under the provisions of paragraph (l) of this AD, operators may request approval of an AMOC for a different inspection method if that method provides the same or higher level of crack detection.”