The International Cessna^® 170 Association

I spoke to fellow today flying a Piper PA-16 Clipper with large Gooodyear tundra tires. I asked how he had them approved. He said that they where approved under CAR-3 which is what the PA-16 was certified with and he used that as the bases of his 337.

Anyone have any thoughts on how that would work? Think it would for our 170s which were also certified under CAR-3

Here is what CAR 3 has to say about tires:

§ 3.362 Tires. A landing gear wheel may be
equipped with any make or type of tire, provided
that the approved tire rating is not exceeded
under the following conditions:
(a) Load on main wheel tires equal to the
airplane weight divided by the number of wheels,
(b) Load on nose wheel tires (to be
compared with the dynamic rating established for
such tires) equal to the reaction obtained at the
nose wheel, assuming the mass of the airplane
concentrated at the center of gravity and exerting
a force of 1.0g downward and 0.31g forward, the
reactions being distributed to the nose and main
wheels by the principle of statics with the drag
reaction at the ground applied only at those
wheels having brakes. When specially
constructed tires are used to support an airplane,
the wheels shall be plainly and conspicuously
marked to that effect. Such marking shall include
the make, size, number of plies, and identification
marking of the proper tire.
Note: Approved ratings are those assigned
by the Tire and Rim Association or by the
Administrator.

Sounds pretty good to me. Gonna have to do some reading and see if there are any other applicable bits.

Tye

There is a difference between "basis of certification" and "basis of approval". CAR 3 provided design guidance (basis of certification) to mfr's for the purpose of developing approved aircraft types. After the designs were approved they were issued a type design certificate, and the mfr met other quality-control requirements and was issued a production certificate, after which each serial exited the production line and inspected to conform to it's type certificate and was issued an airworthiness certificate. Each serial still must have the approved equipment installed and no unapproved equipment.
In other words, in my opinion, your friend is not correct as to the correct interpretation and useage of CAR 3. IMHO He may not substitute unapproved tires on the aircraft based upon CAR 3. He must obtain another basis of approval.

This was a fellow I meet briefly and may not run into again, who knows. He said the tundra tires were approved and he said because CAR-3 didn't restrict the size of the tire.

Whether he just mounted the tires with no futher paperwork or he used CAR-3 as a bases to gain approval I don't know and never will. Just thought it was an interesting approach he took either way.

George, wouldn't the 337 (Major Alteration) be the basis for approval? CAR3 provides criteria for the design. This "basis" stuff is confusing as all get out.

tye

I fly a 170B with 26" "BushWheels" on it.

I wanted to put them on a legally as I could since I have found that the insurance business is really the final law in most of these things.

Chased down all rumors I could dig up and found that I could not find a DIRECT way to do this, but:

There is an STC available from Quebec that allows for the installation of heavier, 180 / 185 gear on 100 series Cessnas.

Then, of,course, Alaska Bushweels sells an STC for putting thier tires on 180 / 185 gear legs. Oh, and yes, they they are more than willing to also sell ya the double piston brake assemblies that are also needed.

Love-em so far with only a minor / slight "de-coupling" of events / processes and results

Chris

thammer wrote:George, wouldn't the 337 (Major Alteration) be the basis for approval? CAR3 provides criteria for the design. This "basis" stuff is confusing as all get out.

tye

Yes, if unapproved equipment is installed on an airplane in a major alteration or repair, the Form 337 must be submitted. If the equipment has been installed with no other basis of approval (i.e. STC) then the Form 337 must have Block 3 signed/approved by the FAA. This is known as a field approval, and a copy of that Form 337 with Block 3 approved must be kept with the aircraft records.
(Submitting a Form 337 can be for the purpose of a major repair...such as when the aircraft is repaired from an accident, in which case approved parts and methods are used, and no approval other than the certificated repairman (A&P) is required, and no response is expected/required from FAA.... but in the case of substitution of unapproved equipment such as tires...it can be submitted for Block 3 approval of that major alteration. And unless the alteration is accepted/approved by the FAA and so noted in Block 3, and a copy returned to the owner, then it is not approved.)