Re: clearance


Robert Cringely
 

It's experimental so do whatever you can get away with, but for Part 23 certification, the FAA requires nine inches for taildraggers with flat tires:

Sec. 23.925 — Propeller clearance.

Unless smaller clearances are substantiated, propeller clearances, with the airplane at the most adverse combination of weight and center of gravity, and with the propeller in the most adverse pitch position, may not be less than the following:

(a) Ground clearance. There must be a clearance of at least seven inches (for each airplane with nose wheel landing gear) or nine inches (for each airplane with tail wheel landing gear) between each propeller and the ground with the landing gear statically deflected and in the level, normal takeoff, or taxing attitude, whichever is most critical. In addition, for each airplane with conventional landing gear struts using fluid or mechanical means for absorbing landing shocks, there must be positive clearance between the propeller and the ground in the level takeoff attitude with the critical tire completely deflated and the corresponding landing gear strut bottomed. Positive clearance for airplanes using leaf spring struts is shown with a deflection corresponding to 1.5 g.

(b) Aft-mounted propellers. In addition to the clearances specified in paragraph (a) of this section, an airplane with an aft mounted propeller must be designed such that the propeller will not contact the runway surface when the airplane is in the maximum pitch attitude attainable during normal takeoffs and landings.

(c) Water clearance. There must be a clearance of at least 18 inches between each propeller and the water, unless compliance with §23.239 can be shown with a lesser clearance.

(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.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23–43, 58 FR 18971, Apr. 9, 1993; Amdt. 23–51, 61 FR 5136, Feb. 9, 1996; Amdt. 23–48, 61 FR 5148, Feb. 9, 1996]



On Thu, Feb 18, 2021 at 5:08 PM Richard Kaczmarek 3RD <fastlittleairplanes@...> wrote:
Actually depending on who you use for the AW certification prop clearance does matter. The FAA here would not sign off on AW for a tri gear Sonex due to the prop only having a light 5" of clearance. To show us why he had us let the air out on the nose wheel at which point the tips would just miss the ground. Then said "a flat tire just got you a prop strike".

Richard

On Thu, Feb 18, 2021, 7:52 PM Jim Patillo <Logistics_engineering@...> wrote:
ZZzzzzzzzzzz....... I run a 60/72 Catto Prop.
Tailwheel first landing from the beginning, hopefully mains after that. Same prop since 2001. No issues. 
zzzzzzzzzzZZ.

Jim
N46JP Q200



Sent from Outer Space

From: main@Q-List.groups.io <main@Q-List.groups.io> on behalf of gbrighton@... <gbrighton@...>
Sent: Thursday, February 18, 2021 3:02:55 PM
To: main@Q-List.groups.io <main@Q-List.groups.io>
Subject: Re: [Q-List] clearance
 
Chris,
            Im not qualified to answer but 3 inch Prop /Gnd clearance
Doesn't sound  enough ! .. The Flying Q guys are asleep on this one !? ..
Seeing the Exhaust coming out of the Cowling is looking like things are
getting Serious ; )
You let me know on another List that you were intending the use SDS for
Engine management . I was hoping to use the OEM Soob ecu .. anyway long
story short i have 'left' that effort ... !!  ... and have now installed a
SDS ecu .. Gnd running seems good  .. and if weather is ok will be test
Flying it this wkend  .
Graham

.
To: <main@Q-List.groups.io>
Subject: [Q-List] clearance

>
>  What are we looking for in prop to ground clearance?.  Does the Q do a
> flair on landing or does it stay relativley flat?
>
>  With the water line level I have three inch clearance with a 58 inch
> prop. I can cut it down no problem if need be.
>
> thanks -----------  Chris
>
>
>
>


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