RV-6 prop length

[sailvi767]

I have been looking at a new prop for a RV6. It would be a 74 inch prop. I a getting conflicting advice on if that length is acceptable. I have spoken with vans and they say its to long. Others who I respect tell me it's not a problem. Anyone running 74 inch props on a six who might have some input.

George

[miyu1975]

not sure how the 6 compares to the 7, but I have been using a 74 inch hartzell for 150 hrs. no problems.

[Kahuna]

George,
Vans position not withstanding, we have a 76" Hartzell composite prop on our RV-6.

[Neal@F14]

Only if you've got the early year short gear legs could I see a problem.
With the later tall gear, losing 1" of prop tip ground clearance isn't going to matter much.

I know someone who's running the 74" Hartzell on an RV-4 with no problems.

This past summer I installed a 72" Sensenich GA composite on my RV-6 (tall gear) and set the prop vertical and picked up the tail to see how much clearance there was. If I'm ever nosed over that far on a landing, then something is so badly wrong that a prop strike is gonna be the least of my worries.

[Andy Hill]

I have been looking at a new prop for a RV6. It would be a 74 inch prop. I a getting conflicting advice on if that length is acceptable

The answer to the question is determined by who it must be acceptable to? You? The FAA? Your Insurance Company? Or as per certified aircraft rules?

I am not (for obvious reasons ) familiar with the USA rules, but get the impression you can largely do as you wish?

If of interest (but not of relevance to you) the UK guidelines we have to work to are (my highlights):

CS-VLA 925 Propeller clearance
Unless smaller clearances are substantiated, propeller clearances with the aeroplane at maximum weight, with the most adverse centre 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 180 mm (for each aeroplane with nose wheel landing gear) or 230 mm (for each aeroplane with tail wheel landing gear) between each propeller and the ground with the landing gear statically deflected and in the level, normal take-off, or taxying attitude, whichever is most critical. In addition, for each aeroplane 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 take-off attitude with the critical tyre completely deflated and the corresponding landing gear strut bottomed. Positive clearance for aeroplanes using leaf spring struts is shown with a deflection corresponding to 1?5 g.
(b) Water clearance. There must be a clearance of at least 46 mm between each propeller and the water, unless compliance with CS-VLA 239 can be shown with a lesser clearance.
(c) Structural clearance. There must be ?

(1) At least 26 mm radial clearance between the blade tips and the aeroplane structure, plus any additional radial Clearance necessary to prevent harmful vibration;
(2) At least 13 mm longitudinal clearance between the propeller blades or cuffs and stationary parts of the aeroplane;
and
(3) Positive clearance between other rotating parts of the propeller or spinner and stationary parts of the aeroplane

.(d) Clearance from occupant(s). There must be adequate clearance between the occupant(s) and the propeller such that it is not possible for the occupant(s), when seated and strapped in, to contact the propeller inadvertently.

Summary: In English (!) Test 1 needs 230mm (~9") clearance with canopy rails level, at MTOW. Test 2 needs clearance at 1.5g with 1 tyre flat - this is unlikely to an issue and can be illustrated via extrapolation.

There are plenty of UK types flying that do not meet the above, but a new proposal would need some "discussion". There might be similar FAA design rules, but for you are presumably of "interest" only

[mike647m]

I was not aware there are different gear lengths on RV-6 aircraft. How do you tell which one you have?

[6 Gun]

Im running 74 on RV6 I have 8" when level. The BA is a good looking prop on the 6 I have the 7497 blades.Also I have small tail on my 6 .
Bob

[Snowflake]

Originally Posted by mike647m

I was not aware there are different gear lengths on RV-6 aircraft. How do you tell which one you have?

I believe that only applies to the RV-4, not the -6.

[Neal@F14]

Originally Posted by Snowflake

I believe that only applies to the RV-4, not the -6.

When shopping for an RV a couple years ago, I once looked at a1990 RV-6 that had short gear on it. It's possible they built it with short RV-4 main legs, but it was definitely sitting on short gear.