Return-Path: Sender: (Marvin Kaye) To: lml Date: Wed, 06 Nov 2002 12:56:47 -0500 Message-ID: X-Original-Return-Path: Received: from JSC-EMS-VWS04.jsc.nasa.gov ([139.169.39.51] verified) by logan.com (CommuniGate Pro SMTP 4.0) with SMTP id 1854532 for lml@lancaironline.net; Wed, 06 Nov 2002 12:45:15 -0500 Received: from 139.169.16.59 by JSC-EMS-VWS04.jsc.nasa.gov (InterScan E-Mail VirusWall NT); Wed, 06 Nov 2002 11:01:18 -0600 Received: by jsc-smtp01.jsc.nasa.gov with Internet Mail Service (5.5.2653.19) id ; Wed, 6 Nov 2002 11:01:18 -0600 X-Original-Message-ID: <1848CABD3587A84DAC6B3F82FE01D9FC01F1FC04@jsc-mail08.jsc.nasa.gov> From: "THORN, VALIN B. (JSC-OM) (NASA)" X-Original-To: "'lml@lancaironline.net'" Subject: RE: [LML] Legacy Horiz Stab Angle Of Incidence X-Original-Date: Wed, 6 Nov 2002 11:01:13 -0600 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: text/plain Re: [...I thought that the angle of incidence was set by the airframe being level with the waterline. In my mind that has nothing to do with the center of gravity and the size of the engine, but rather the front to back leveling of the aircraft... Curtis Krouse] ----------------------------------- Hi Curtis, Yes, I agree that the angle of incidence is set and measured relative to the airframe -- for both the wing and horizontal stabilizer (HS). What I'm trying to do is optimize our HS angle of incidence for our airplane/engine combination. I'll try to explain the rationale... The Legacy, as I understand it, was originally designed for an IO-360 engine with the IO-550 a follow-on development. The IO-550 weighs about 100 lbs more -- so with no other changes the c.g. is farther forward. This requires a larger balancing tail load/force to maintain balance in the pitch axis. If no change is made to the horizontal stabilizer's (HS) angle of incidence (AOI) then the elevator will have to fly more nose up to provide this increased downward force. This increases the drag a little bit compared to having the elevator fly in the neutral/zero degree position. I'd like to save any slight drag penalty by increasing the HS AOI (in the negative direction) to get the elevator to fly at zero degrees while in cruise. I'm guessing that the -0.6 degrees end of the factory's HS AOI range is for the heavier engines... Thinking about how I wrote my question, I should not have said "for the middle of the c.g. range" -- but "for the typical c.g. for your airplane..." Now, all that being said, a few degrees of cruise trim elevator deflection isn't going to change the drag/cruise speed significantly. But, the more I read the LML the more I'm becoming (as I think Larry Henning once said) a "Quarter-Knot Freak"... Valin -- New QKF :) Legacy 173