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
----- Original Message -----
From: William Daniell<mailto:wdaniell@etb.net.co>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Tuesday, December 20, 2011 8:34 AM
Subject: Europa-List:
I am sure that this has been posted many time but to avoid having to
hunt through the archives - what is the max prop diameter for a Trigear?
Will
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