X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-d03.mx.aol.com ([205.188.157.35] verified) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 872383 for flyrotary@lancaironline.net; Mon, 12 Dec 2005 11:06:09 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.157.35; envelope-from=Lehanover@aol.com Received: from Lehanover@aol.com by imo-d03.mx.aol.com (mail_out_v38_r6.3.) id q.1c5.365e4f20 (58435) for ; Mon, 12 Dec 2005 11:05:08 -0500 (EST) From: Lehanover@aol.com Message-ID: <1c5.365e4f20.30cef9b3@aol.com> Date: Mon, 12 Dec 2005 11:05:07 EST Subject: Re: [FlyRotary] Re: "P" factor? Re: Static Engine RPM To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1134403507" X-Mailer: 9.0 SE for Windows sub 5022 X-Spam-Flag: NO -------------------------------1134403507 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In the one case, the whole of the rotating mass of the engine and propeller are turning in the same direction, while in the other case, they turn in opposing directions, and to some extent, precession is canceled. The argument that an affect caused by misaligned relative wind through the prop makes for more thrust on the right side vice the left side rings hollow, because the big gyroscope in the front moves that force to the bottom of the disc and makes it a nose up moment in right hand rotation, and nose down in left hand rotation. Same thing when the tail comes up on the Super Cub. Close to no rudder authority, spiraling flow pushing the tail to the right, and the precession (just during the attitude change) helping push the nose to the left. But once the nose is up, there is no further precession, the situation is close to that of the trigear plane, and still you have rudder dialed in. So why has the "P" factor not vanished? Because it's 98% spiraling flow pushing on the fin and rudder. Note that the rudder is mounted so as to be active all of the time in countering the spiraling flow. The amount of offset is adjusted to be ideal at cruise speeds (so there is no trim drag). Years ago, over New Jersey the 19 year old trainee was doing (trying to do) stalls in climbing turns to the right in the super cub. The aerobatic rated instructor let me try for a while with no success, it just fly's around in a nose high spiral and won't stall. He told me to rock it a little, let the back pressure off for a second or so, and that snap it back again. That did work. The nose and high wing fall through smartly and recovery is straightforward. Then he said do some to the left. Nose high turning left is easy at full throttle, the nose and high wing not only went through first, they kept right on going, into an inverted spin. As was his usual command, he yells "what are you going to do now?" With the door and window open, I notice that my pencil is dancing on it's point about three feet out on the wing. I have no idea, I yell back. So while we get closer to New Jersey he explains it at length, and then recovers crisply. So why does it turn left so nicely when at full throttle and zero airspeed, and so poorly to the right? Because of the "P" factor, spiral flow pushing the tail to the right. Lynn E. Hanover In a message dated 12/11/2005 10:19:27 PM Eastern Standard Time, lendich@optusnet.com.au writes: Ed, What you are saying reflects what I've read also - however Tracy's experience with the difference between the 2.17 and the 2.85 suggests that there is also the centrifugal forces of prop + rotor direction to contend with, as Tracy required full R rudder to maintain directional control with the 2.85, whereas with the 2.17, it wasn't anywhere near as difficult - so I'm led to believe. If it were just the wind from the prop corkscrewing around the fuselage until it hit the rudder, the L and R turning props would give a similar response in intensity. This wasn't the case, it would seem. George ( down under) -------------------------------1134403507 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In the one case, the whole of the rotating mass of the engine and prope= ller=20 are turning in the same direction, while in the other case, they turn in=20 opposing directions, and to some extent, precession is canceled.
 
 The argument that an affect caused by misaligned  relative w= ind=20 through the prop
makes for more thrust on the right side vice the left side rings hollow= ,=20 because the big gyroscope in the front moves that force to the bottom of the= =20 disc and makes it a nose up moment in right hand rotation, and nose down in=20= left=20 hand rotation.
 
Same thing when the tail comes up on the Super Cub. Close to no rudder=20 authority, spiraling flow pushing the tail to the right, and the precession=20 (just during the attitude change) helping push the nose to the left.
 
But once the nose is up, there is no further precession, the situation=20= is=20 close to that of the trigear plane, and still you have rudder dialed in. So=20= why=20 has the "P" factor not vanished?
 
Because it's 98% spiraling flow pushing on the fin and rudder. Note tha= t=20 the rudder is mounted so as to be active all of the time in countering the=20 spiraling flow. The amount of offset is adjusted to be ideal at cruise speed= s=20 (so there is no trim drag).  
 
Years ago, over New Jersey the 19 year old trainee was doing (trying to= do)=20 stalls in climbing turns to the right in the super cub. The aerobatic rated=20 instructor let me try for a while with no success, it just fly's around in a= =20 nose high spiral and won't stall. He told me to rock it a little, let the ba= ck=20 pressure off for a second or so, and that snap it back again.
 
That did work. The nose and high wing fall through smartly and recovery= is=20 straightforward.
 
Then he said do some to the left.
 
Nose high turning left is easy at full throttle, the nose and high wing= not=20 only went through first, they kept right on going, into an inverted spin. As= was=20 his usual command, he yells "what are you going to do now?"
 
With the door and window open, I notice that my pencil is dancing on it= 's=20 point about three feet out on the wing. I have no idea, I yell back. So whil= e we=20 get closer to New Jersey he explains it at length, and then recovers=20 crisply.
 
So why does it turn left so nicely when at full throttle and zero airsp= eed,=20 and so poorly to the right? Because of the "P" factor, spiral flow pushing t= he=20 tail to the right.
 
Lynn E. Hanover
 
 
 
In a message dated 12/11/2005 10:19:27 PM Eastern Standard Time,=20 lendich@optusnet.com.au writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
Ed,
What you are saying reflects what I've read also - how= ever=20 Tracy's experience with the difference between the 2.17 and the 2.85 sugge= sts=20 that there is also the centrifugal forces of prop + rotor direction to con= tend=20 with, as Tracy required full R rudder to maintain directional control= =20 with the 2.85, whereas with the 2.17, it wasn't anywhere near as difficult= -=20 so I'm led to believe.
If it were just the wind from the prop corkscrewing ar= ound=20 the fuselage until it hit the rudder, the  L and R turning props=20 would give a similar response in intensity. This wasn't the case, it=20 would seem.
George ( down under)
<= /DIV>
 
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