Air Filters

Receiving inspection of new air filters (p/n P107336) revealed three out of four had a defective sealing surface, causing the sealing/mating surface to crack and crumble. This defective sealing surface could potentially enter the engine. The defective filters sealing surface has a light-gray color while the replacement filters we received, inspected and found to be in serviceable condition had a dark gray, almost black sealing surface. Suspect that the defective filters had improper material on the sealing surface or were improperly cured.

Editorial Staff

Sunday, June 02, 2019 at 12:00 AM ET

Verified

Key Takeaways:

Multiple incidents detail various air filter failures across different aircraft, including loose gaskets, defective sealing surfaces, debonded felt seals, and split seams.
These failures can lead to severe engine problems such as unfiltered air ingestion, premature wear, particles in the induction system, and critical in-flight engine shutdowns.
Issues were found in both OEM and aftermarket filters, with some defects, like poor bonding or material flaws, being present even in new parts.

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Beechcraft V35B Bonanza

Loose Gasket

The gasket on the back side of a K&N induction air filter (p/n CP0711) came loose and was sucked into the engine, causing it to stop running. This air filter is not an OEM product and was installed with an STC and logbook entry. A different company had the same problem, which resulted in AD 96-09-06. Called company, which said they had no problems.

Part total time: Unknown

Cessna 337H Skymaster

Defective Sealing Surface

Receiving inspection of new air filters (p/n P107336) revealed three out of four had a defective sealing surface, causing the sealing/mating surface to crack and crumble. This defective sealing surface could potentially enter the engine. The defective filters’ sealing surface has a light-gray color while the replacement filters we received, inspected and found to be in serviceable condition had a dark gray, almost black sealing surface. Suspect that the defective filters had improper material on the sealing surface or were improperly cured.

Part total time: 0.0 hours

Cessna 421C Golden Eagle

Debonded Felt Seal

Customer reported uneven idle and erratic EGTs on all cylinders and an in-flight engine shutdown. Troubleshooting revealed a filter (Donaldson p/n P108421) we replaced at annual had lost its inboard felt seal. Particles were found throughout the induction system and fuel injectors as well as the intercooler. Components were removed for cleaning. The seal on the filter must have had only low/partial adhesion, as remaining seal was found to also be partially bonded. New filters purchased for other aircraft showed less than 50 percent bonding of the felt seal.

Part total time: 18.0 hours

Cirrus SR22

Split At Seam I

During a scheduled inspection, the air filter was discovered to be split open at the seam. This same condition has been found on several other air filters of the same p/n (Brackett BA24). While not an immediate safety of flight issue, this condition allows unfiltered air to enter the induction system. If allowed to continue for any length of time, this can cause premature wear and possible early failure of the engine.

Part total time: 38.0 hours

Cirrus SR22

Split At Seam II

Air filter found split open at glued seam during annual inspection. Split area comprises 4-6 sq. in. of unfiltered air path to engine induction system. This is the second filter element (p/n BA24) this inspector has found on this type of filter element.

Part total time: 112.0 hours