wtcef(at)arn.net
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 Posted: Mon Dec 26, 2011 8:07 pm Post subject: Europa-List: |
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On Mon, Dec 26, 2011 at 4:18 PM, Bud Yerly <budyerly(at)msn.com> wrote:
[quote]
Will,
Max prop diameter is still 64 inches recommended. This is based on the prop
clearance of course. In the tri gear clearances are based on spring or
bungee with the by the book cable stop dimensions per the build
manual. This leaves nominally 10-11 inches from the prop tip to the ground
(aircraft unloaded, nose tire inflated at 35 psi. and the CG at 60
inches) in most of my aircraft. At full deflection of the gear at full
gross weight, this gives 7-8 inches of clearance. (Yours may be different
due to main gear installation.)
FAA requirements for minimum propeller clearance:
Sec. 25.925
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) 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 landing gear statically deflected and in the level takeoff, or taxiing
attitude,
whichever is most critical. In addition, there must be positive clearance
between the propeller and the ground when in the level takeoff attitude
with the critical [tire(s)] completely deflated and the corresponding
landing
gear strut bottomed.
Europa nominal clearances:
If installed by the book at 2 inches (full cable extension), crossed
properly so the cable cannot slip off, with a deflated nose gear tire, there
is at least 4 inches of clearance on my new builds putting a full 300 pounds
on the front of the engine. That will keep you from mowing the grass and or
plowing a furrow with your 64 inch propeller if the nose gear tire fails on
a rough landing or rough strip.
12 AY flew with the gear leg bolted solid in an attempt to install a longer
prop. I don't recommend it. It's a bit harsh on a rough strip so to
prevent fatigue I installed the springs shortly thereafter and shortened my
cable stop to allow a total of 1 inch of movement until contact and a bit
more on full extension.
Longer answer on install and extended life operations notes:
On installation, Chapter 29T says to pull the gear leg up (without springs
or bungee) and swag the cable at two inches from the stop to the leg. I
clamp (using a bolt type cable clamp) the cable at that distance with the
gear leg pulled to check full tension on the cable. When satisfied,
I then swag the cable. This gives 8 inches clearance as stated above.
In the field, because the spring or bungee is attached normally, I use the
one inch (two fingers) method to check if I need to re-swag the cable
because of poor installation or cable stretch. I find the cable easy to
pull down firmly from under the aircraft and check the distance. To check
the springs I place my full body weight (180 lbs.) at the hub to deflect the
springs the full amount for a quick check. When doing maintenance on other
aircraft I have found that the cable will stretch a bit more than new which
puts more strain on the springs. Occasionally I have seen on trigears which
have operated extensively on grass, and the cable stop either was installed
improperly or it had loosened and had not worked as advertised (it slipped
off the lower leg) and this caused the springs to become weaker under severe
grass strip operations. (Thirty pounds at the hub caused the springs to
deflect which is unacceptable.) It is not fun to cut those springs off and
replace them because they no longer hold the nose gear firmly on the stop.
So it was a personal decision to go tighter than looser on the cable stop to
prevent this from happening.
Regards,
Bud Yerly
Europa Tech Support
813 244-8354
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