Beta Prop

Gig 601XL Builder wrote:
I well could be plus in my head Beta means reversing. The reason
for this is
when I was getting my helicopter rating the instructor used the term for
negative rotor pitch and it stuck in my head.

What would the point of this in a small plane be if not reversing?

For a given beta pitch, the prop makes much more reverse thrust with
forward airspeed than when there is very little airspeed. This is
because of the angle of attack on the prop blades (aerodynamic
explanation using vectors).

The point is your landing rollout is greatly reduced, because the
prop provides a lot of deceleration immediately after touchdown when
the brakes are least effective (think, jam on the brakes too hard
when the wing is still making some lift, they lock up).

It's handy during taxiing when you can get no or slight reverse
thrust, that saves your brakes and is less workload when you get the
hang of it. It's usually a bad idea to reverse taxi- kick up fod
then roll through it as the engine ingests it, hard to see where
you're going, the nose (or tail) wheel may not castor 360 degrees...
to name a few reasons.

"Jim Carriere" wrote

It's handy (beta) during taxiing when you can get no or slight reverse
thrust, that saves your brakes and is less workload when you get the
hang of it. It's usually a bad idea to reverse taxi- kick up fod
then roll through it as the engine ingests it, hard to see where
you're going, the nose (or tail) wheel may not castor 360 degrees...
to name a few reasons.

It is also -really- handy for seaplanes, who have *no* brakes. ;-))
--
Jim in NC

On Wed, 10 Aug 2005 00:57:18 -0400, Morgans wrote:


"Jim Carriere" wrote

It's handy (beta) during taxiing when you can get no or slight reverse
thrust, that saves your brakes and is less workload when you get the
hang of it. It's usually a bad idea to reverse taxi- kick up fod then
roll through it as the engine ingests it, hard to see where you're
going, the nose (or tail) wheel may not castor 360 degrees... to name a
few reasons.

It is also -really- handy for seaplanes, who have *no* brakes. ;-))


But, having a prop with a beta or reverse capability adds new very nasty
failure modes. Type certificated aircraft with props that have a beta or
reverse functionality have additional complicated monitors to prevent the
prop from going into uncommanded beta or reverse in flight. I would want
a prop with the low pitch stop set to a position that is safe for
in-flight operation. If the prop goes into beta or reverse in the air it
can kill you.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com