Received-SPF: none
 receiver=logan.com; client-ip=66.37.197.101; envelope-from=bbradburry@allvantage.com
Message-ID: <009f01c5ff34$820b7b60$6f21eb04@h2m6k0>
Reply-To: <bbradburry@allvantage.com>
From: <bbradburry@allvantage.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-872173@logan.com>
Subject: Static RPM
Date: Mon, 12 Dec 2005 10:55:41 -0500
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

So, If what you say is true, pusher planes will have no P-factor???

Bill Bradburry

Ed, Charlie England is going to get us for posting new at top, but seems
like this post is going that direction so I didn't reverse the flight
pattern

I think you are correct on both counts that P factor is actually the torque
generated when the prop runs a non-zero angle of attack and what you are
feeling may be the swirl effect on the flying surfaces. You have demo'd the
swirl effect from a plane taking off in front of you (remembering your
harry T/O behind Finn there)But I do think that when the thrust line does
not line up with the CG of the airplane there is also a steering effect
right or left depending on the angle of the engine mount and yours
aggrevates the swirling force.

Bernie, no prop to fly with til after Christmas

Hi Georges,

The "P" direction  factor only changed when I changed from the 2.17 to the
2.85 (with the opposite propeller rotation) .  The shortening of the prop
slight reduced the "P" factor but did not change its direction.

One thing I think I should mention.  I used to think the force was caused by
the "P" factor, but after reading an article about the effects of Torque,
"P" factor and Airstream whirl, I came away with a different understanding.
Apparently "P" factor is a factor primarily with tail draggers as it is
caused by the effect of the  relative wind and the prop blades  not being
perpendicular to the relative wind (until the tail comes up).  With a nose
gear, the blades are perpendicular (at least until lift off) and therefore
the "P" factor is minimal.

Apparently the real cause of the rather powerful force that wants to push
the nose to the left or right is the swirling air caused by the spinning
prop.  Think of a cork screw.   With my prop now spinning CCW (from pilot's
perspective) the corkscrew of air is swirling CCW as well.  It appears the
distance from prop to vertical stabilizer is such that the air corkscrews
around so that more of it hits the left side of the fuselage and vertical
stab than the right.  This air forces the tail toward the right and the nose
to the left, thereby requiring right rudder to counteract the force.

Sounded reasonable to me.  Not to say there is not torque or "P" factor but
given the magnitude of the turning force I would say the air swirl probably
is the major factor.

Ed A


Ed A
----- Original Message ----- 
From: Echo Lake Fishing Resort (Georges Boucher)
To: Rotary motors in aircraft
Sent: Sunday, December 11, 2005 8:53 PM
Subject: [FlyRotary] Re: Static Engine RPM


Hi! Ed
I guess I missed something, how can the P-factor be in the"opposite"
direction after shortening the prop 2"?
Georges B.

-------Original Message-------

From: Ed Anderson
Date: 12/10/05 14:54:00
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Static Engine RPM

 Hi Bernie,

Good point, Yes, you are correct the engine mount is still the same.
However, since it only causes 1/2 ball deflection in cruise, I not certain
that the mount is that far offset in the wrong direction.  Guess I should
add a few washers and find out - just kidding.  One of my numerous projects
is to fabricate some new engine mounting brackets (keeping the same mounting
frame) with the offset to the opposite side.

Besides, its really the increased ROC that really tells the story.  I
consistently get over 1500 fpm and even get up into the 1700 fpm range on
cold days lightly loaded.  Previously it was in the 1000-1200 fpm range.

Ok on the prop, Bernie.

I'm planning at this time to fly out to Bill Eslick flyin in Feb weather
permitting - make a nice long flight for your 9.

Ed A


===========================================
Hi Ed,

Don't forget to add that the P-factor is now in the opposite direction and I
believe you did not change angle of engine mount to offset this. I'm not
questioning that you get more thrust with this set up, just questioning if
your criteria of lack of rudder is a good indicator.

Took your prop and the sensenich to plant city and left both with them. Will
probably be able to pick them up on the way home from Memphis after
Christmas.

Cheers and Merry Christmas in NC,
Bernie