This topic comes about as a Canadian is trying to import a US aircraft (AA1A) into Canada. It is much easier to bring a Canadian plane into the US since Canada Transport requires that Service Bulletins and Service Letters be treated like ADs.

This concerns the propeller and what the different numbers mean. Let us see what the TCDS has to say about propeller that are legal:

1. McCauley Model 1A105/SCM-7157 fixed pitch propeller. Static r.p.m. at maximum permissible throttle setting; not over 2300; not under 215C. Diameter: not over 71 inches, not under 69.5 inches.

2. McCauley Model 1A105/SCM-7153 and 1A105/SCM-7154 fixed pitch propellers. Static r.p.m. at maximum permissible throttle setting; not over 2400; not under 2250. Diameter: not over 71 inches, not under 69.5 inches.

3. McCauley Model 1A106/NCM-7157 fixed pitch propellers. Static r.p.m. at maximum permissible throttle setting; not over 2400; not under 2300. Diameter: not over 71 inches, not under 69.5 inches.

4. McCauley Model 1A106/NCM-7153 hub and fixed pitch propellers. Static r.p.m. at maximum permissible throttle setting; not over 2475; not under 2375. Diameter: not over 71 inches, not under 69.5 inches.

Now the propeller (McCauley) currently on the plane is an SCM 7054. This mean that the diameter is 70 inches (having been taken down enough at overhaul to reduce the diameter to the nearest inch, in this case, ’70.’ The 54 is the propeller blade pitch at the 75% radial location. Notice there is no propeller like that with that pitch.

Whereas propeller pitch will be called out for each legal pitch, it is not a range. Even in the AG5B it lists, 60, 61, 62, 63, 64, 65.

The diameter is a range, in this case 71 down to 69.5. So 70 is a legal diameter, but the pitch of 54 is not.

The propeller will have to be repitched to 53 which will give the plane a bit more climb performance and maybe a knot or 2 slower at cruise.

What do your log books have to save about your plane?

BTW, this plane was annualled by several different shops in the US and no IA caught this error in the propeller.

Cheers

Roscoe