Clearance between spinner and cowl

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Clearance between spinner and cowl

Unread post by clivem » Sun Feb 26, 2017 9:39 pm

Can anyone tell me what the distance between the spinner backplate and the cowl is on an aerobatic plane like an extra / sBach / slick etc is?
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Re: Clearance between spinner and cowl

Unread post by StressMerchant » Tue Feb 28, 2017 11:13 am

Not all the aerobatic aircraft are type certified, but the ones that are will have to conform to this as a minimum:
Sec. 23.925

Propeller clearance.

Unless smaller clearances are substantiated, propeller clearances with the airplane at maximum weight, with the most adverse center of gravity, and with the propeller in the most adverse pitch position, may not be less than the following:
(a) ........
(b) ........
(b) ........
(d) Structural clearance. There must be--
(1) At least one inch radial clearance between the blade tips and the airplane structure, plus any additional radial clearance necessary to prevent harmful vibration;
(2) At least one-half inch longitudinal clearance between the propeller blades or cuffs and stationary parts of the airplane; and
(3) Positive clearance between other rotating parts of the propeller or spinner and stationary parts of the airplane.
In practice the "positive clearance" distance is probably 1/4" to 1/2" to allow for vibration and for isolator wear.

Hope this helps
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