Engine mount to fuselage bolts

How to keep the Cessna 170 flying and airworthy.

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1moretw
Posts: 38
Joined: Sat May 28, 2022 11:29 am

Engine mount to fuselage bolts

Post by 1moretw »

The bolts holding my engine mount to the fuselage are not all the same. Some have castellated nuts and some don't. Additionally, the nuts are all on the inside of the fuselage. Is there a standard for direction of the bolt and the type of nut (metal locking, fiber locking or castellated)? One of the bolts is even too short so no threads protrude.
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c170b53
Posts: 2527
Joined: Mon Apr 22, 2002 8:01 pm

Re: Engine mount to fuselage bolts

Post by c170b53 »

4629CE81-E2E1-45BE-80E6-ED389D4863B5.jpeg
TW, welcome to the association and the forums. Please let us know what model, year you’re flying one more time! Do you have the IPC ?
Above the bolts on a “B”. General rule, nuts to the pilot but not always. Having the right bolts generally works best :D
Thks for joininh
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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Bruce Fenstermacher
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Re: Engine mount to fuselage bolts

Post by Bruce Fenstermacher »

You have a lot of questions to answer.

Direction of the bolt. As specified, as depicted or head towards direction of flight or direction of rotation are the rules that come to mind. So first a maintenance manual may specify the direction. Next a IPC or maintenance manual may depict the bolt in a direction though be careful IPCs are seldom approved sources. Last head in the direction of travel or rotation so in theory if the nut came of or the bolt sheared, the bolt or parts left of it may stay in place holding parts together.

More later as I have time.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
1moretw
Posts: 38
Joined: Sat May 28, 2022 11:29 am

Re: Engine mount to fuselage bolts

Post by 1moretw »

Thank you, thank you for the picture from the parts manual. Never gave it a thought re looking at the manual.
By the way, my 170 is a 1952 170B N2674D
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Bruce Fenstermacher
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Re: Engine mount to fuselage bolts

Post by Bruce Fenstermacher »

More. There is no difference in strength of a standard AN bolt whether it is drilled for a cotter pin or not. It is improper however to us a drilled bolt with a mechanical locking nut and it would be weaker if you did and the mechanical locking nut was over or outside the drilled hole. The castellated nut, there are several kinds, and cotter is just a method of locking the nut in place.

Mechanical locking nuts come in all steel pinching and fiber insert type. General rule is the all steel versions would be used anyplace the fiber type might be destroyed by heat. Generally you don't find fiber nuts firewall forward. The exception is of course if a fiber nut is specified forward of the firewall by an IPC Our C-145/0-300 have a few fiber nuts specified on the engine by the manufacturer and so while contrary to the general rule, could not be questions as being correct. Few would find it a problem replacing fiber locking nuts with metal type but not necessarily the other way around.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
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