According to an FAA Safety Team bulletin issued Dec. 30, there is new concern about the use of oversize tires on all aircraft, but especially Tundra Tires. It seems that the FAA's Werner Koch, an aerospace engineer, has new concerns after a recent rim failure that sent a Lower 48 Allied AG Cat with oversized tires into a ditch on takeoff.
Alaskan aircraft owners use the oversize tires to land on gravel and many surfaces where normal tires would cause the aircraft to bog down in sand, sink in mud, or even flip over on soft spongy tundra.
The AG Cat incident has FAA's Koch once again questioning the use of oversized tires that triggered an airworthiness bulletin about the tires.
Tundra Tires have been previously tested by the FAA and according to Alaska experts tests at that time did not reveal any concerns about the oversized tires, tubes or rims on Alaska-flown-and-tested 30 or 35-inch Tundra Tires.
"Any tests that were done on Tundra Tires in the last go around with the FAA would have brought forward any potential for failures," said Dan Hollingsworth of Dan's Aircraft Repair at Merrill Field. "If the FAA is once again going to revisit the use of these tried and true tires, I will work with them to alleviate their concerns. If that doesn't work then we will get the Alaska Airmen's Association involved."
The FAA issued a Special Airworthiness Bulletin (SAIB) CE: 11-06 on Dec. 16, 2010 with recommendations for aircraft owners using oversized tires.
They are as follows:
Before installation of larger tires operators should do the following as a minimum:
-- Initially inspect wheels for cracks using an industry standard fluorescent penetrant process with annual inspections thereafter.
-- Install only approved vendor supplied tires.
-- Install new tubes.
-- Determine the appropriate tire pressure for your specific tire, aircraft, and aircraft operations in consultation with the approved tire manufacturer and FAA Advisory Circular, AC 23-17B.
-- Check for clearance between the tire and brake components.
-- Check the tire pressure and abnormal wear at 2 week intervals or less.
Hollingsworth, who rebuilds Piper Super Cubs, and has provided rebuilt Cubs for the Alaska Airmen's Association's yearly raffle for the last two years, is working on yet another for the 2011 raffle.
"Most pilots prefer the 30 inch tires, and for the really tough areas the 35s," said Hollingsworth. "This looks to me like the AG Cat owners were using the tires and an extended rim combination with bigger tires to create more clearance for a big prop that caused that problem. Here in Alaska we use a well-tested combination of rims, brakes and tires that are not a problem."
For more information contact: Werner Koch, Aerospace Engineer, FAA, Airplane Certification Office, ASW-150, 2601 Meacham Blvd, Fort Worth, TX 76137; phone: (817) 222-5133; fax: (817) 222-5960; e-mail: werner.g.koch(at)faa.gov.
See the full FAA bulletin and recommendations here.
Contact Rob Stapleton at robstapleton(at)alaska.net.