Prop Bolt Length

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8360
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Joined: Fri Nov 30, 2018 11:08 pm
Name: Mark Uhlman
Location: Perry, Oklahoma
Aircraft Type: 1947 C120
Occupation-Interests: Chief Flight Instructor/DPE
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Prop Bolt Length

Post by 8360 »

My IA just squawked the prop (McCauley) bolts on new-to-me 120. They appear to be too short; unused threads visible in nuts on back of prop. Is this normal? Logs show sign-off on installation and other IA's signed subsequent annuals. Thoughts? Thanks for help.
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8342
Posts: 293
Joined: Sun Oct 14, 2018 11:55 pm
Name: Rick F
Location: KUSE Wauseon OH
Aircraft Type: C-140 (sold)
Occupation-Interests: Captain B-777 (Retired)
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Re: Prop Bolt Length

Post by 8342 »

It depends on if it has a tapered or flanged crankshaft.

The IPC shows:

Flanged-AN6H-31

Tapered-AN6-34A

You can download a 120/140 Illustrated Parts Catalog (IPC) from the members section of Association website.

Rick
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6643
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Name: John C
Location: KLCI, NH
Aircraft Type: 1946 C140/C90
Occupation-Interests: A&P, semi-retired
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Re: Prop Bolt Length

Post by 6643 »

It also depends on whether you have a metal prop or a wooden one. Since you refer to the "nuts" on the back of the prop (I assume this means the side facing the pilot) you must have the flanged crankshaft, and the correct bolts are the -31's for the McCauley metal prop. Length, measured from the underside of the head to the end of the threads should be 3-13/64" +1/32, - 1/64. There should be one AN960-616 washer between each bolt head and the prop, no gasket or front ring.
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