X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 16 Apr 2012 08:13:56 -0400 Message-ID: X-Original-Return-Path: Received: from imr-ma05.mx.aol.com ([64.12.100.31] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTP id 5481245 for lml@lancaironline.net; Sat, 14 Apr 2012 08:43:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.100.31; envelope-from=Sky2high@aol.com Received: from mtaomg-mb06.r1000.mx.aol.com (mtaomg-mb06.r1000.mx.aol.com [172.29.41.77]) by imr-ma05.mx.aol.com (8.14.1/8.14.1) with ESMTP id q3ECgae7012221 for ; Sat, 14 Apr 2012 08:42:36 -0400 Received: from core-mtb005a.r1000.mail.aol.com (core-mtb005.r1000.mail.aol.com [172.29.234.209]) by mtaomg-mb06.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 0FFFCE000085 for ; Sat, 14 Apr 2012 08:42:36 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <3aa3a.40587059.3cbacabb@aol.com> X-Original-Date: Sat, 14 Apr 2012 08:42:35 -0400 (EDT) Subject: Re: [LML] L320 flap setting X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_3aa3a.40587059.3cbacabb_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [67.175.156.123] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:426131488:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d294d4f8970bc0623 --part1_3aa3a.40587059.3cbacabb_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Ed, Rob, et al, =20 The purpose of reflexed flaps (wing TE) is for reduction of drag at cruise= =20 speeds. After certain minimum speeds, induced drag is lessened by=20 reducing lift through a reflexed TE (also reducing anti lift at the horiz = stab). =20 Parasitic drag in a laminar flow environment may also be reduced by=20 reattaching the airflow at the reflexed flap. The basic fat wing design h= elps=20 when the leading edge gets dirty (disrupts laminar flow) because lift is o= nly=20 slightly reduced but draq increases (ice, rain, bugs - see note 1). This= =20 is as opposed to a thin laminar wing which may lose lift when dirty. The= =20 fat wings allows our grocery cart wheels to be stowed within. =20 =20 When the flap is reflexed, the point of lift moves forward where higher =20 speeds require more nose down trim (less negative AOA at the horiz stab) a= nd=20 lower speeds require a higher angle of attack to achieve adequate lift. I= n=20 general, below a max Vf (160 to 140 KIAS), the flaps may be taken out of= =20 reflex (to 0 degrees) where the attitude of the airplane can be changed by= =20 up to 6 degrees nose down (as measured digitally at the longeron) and this= =20 will require substantial nose up trim for level flight while the speed dro= ps=20 (about 15 KIAS) from increased drag. For this wing, further reflexing=20 beyond -7 has little effect on speed in cruise (Note 2). =20 This form of wing is not unique - reflexed trailing edges are used in all = =20 tailless (and non-canard) aircraft. In such aircraft, changes in CG are = =20 compensated for by changing the angle of reflex (changes fwd/aft point of = =20 lift). Remember that the same is true with the 200/300 series wings. (hin= t:=20 aft CG wallow may be reduced by taking a bit of reflex out of the wing). = =20 Remember also that slow speed operation with flaps fully reflexed requires= a=20 high AOA to compensate for the reduction in lift from the reflex. Be=20 careful out there. =20 Max lift, min drag at 70-100 KIAS is with the flaps at TO position (about = =20 +10 degrees down from full reflex). After about +17 degrees down from ful= l=20 reflex, the flaps seem to merely add drag that is useful in higher than 3 = =20 degree descent angles (preservation of kinetic energy) - keeping the speed = =20 controlled (below 100 KIAS) at low power settings and also keeping the nos= e=20 low. =20 Maybe next time I will record AOA digital display data in some of these =20 configurations. =20 Scott Krueger N92EX =20 Note 1: In an Air Venture x-ctry race, KARR was a turning checkpoint that = =20 required I descend over the monitor. In that descent I ran through a mass= =20 of little black bugs (so did others) and my return to level flight as the = =20 same race power resulted in speeds 6-7 KIAS less than before the encounter= . =20 Later, I noted that the splattered bugs were very close together (less=20 than a 1/4") and had completely messed up the laminar flow at the leading = edge=20 of the wings. Slow downs have also occurred in flight through rain. =20 Note 2: Certain 320/360 racers experimented with more reflex with the =20 conclusion that there was no significant improvement in speed. =20 =20 =20 =20 In a message dated 4/13/2012 11:02:14 P.M. Central Daylight Time, =20 egraylaw@swbell.net writes: =20 I have the exact concerns reported by Rob Stevens in Australia. Since the= =20 manual is vague on cruise flap settings, can some experienced L320-360=20 fliers help us with what is the best cruise settings? Is it -7deg. , -10d= eg.,=20 or somewhere else. Since construction variances can create different =E2= =80=9C faired-in positions=E2=80=9D, is there an angle which can be measured from= the top or=20 bottom wing surface? Can anyone explain the aerodynamic reasons for=20 reflexed flaps? Rob and I need help!=20 Ed Gray Dallas L360 N77ZG XP360 Silver Hawk injection MT 3 blade prop=20 Dual Dynon Skyview SL30 --part1_3aa3a.40587059.3cbacabb_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
Ed, Rob, et al,
 
The purpose of reflexed flaps (wing TE) is for reduction of = drag=20 at cruise speeds.  After certain minimum speeds, induced drag is lesse= ned=20 by reducing lift through a reflexed TE (also reducing anti=20 lift at the horiz stab).  Parasitic drag in a laminar flow= =20 environment may also be reduced by reattaching the airflow at the=20 reflexed flap.  The basic fat wing design helps when the leading = edge=20 gets dirty (disrupts laminar flow) because lift is only slightly reduced bu= t=20 draq increases (ice, rain, bugs - see note 1).  This is as opposed to = a=20 thin laminar wing which may lose lift when dirty.  The fat wings allow= s our=20 grocery cart wheels to be stowed within. 
 
When the flap is reflexed, the point of lift moves forward where highe= r=20 speeds require more nose down trim (less negative AOA at the horiz=20 stab) and lower speeds require a higher angle of attack to achieve ade= quate=20 lift.  In general, below a max Vf (160 to 140 KIAS), the flaps ma= y be=20 taken out of reflex (to 0 degrees) where the attitude of the airplane = can=20 be changed by up to 6 degrees nose down (as measured digital= ly at=20 the longeron) and this will require substantial nose up trim for level flig= ht=20 while the speed drops (about 15 KIAS) from increased drag.  For this w= ing,=20 further reflexing beyond -7 has little effect on speed in cruise = (Note=20 2).
 
This form of wing is not unique - reflexed trailing edges are used in = all=20 tailless (and non-canard) aircraft.  In such aircraft, changes in CG a= re=20 compensated for by changing the angle of reflex (changes fwd/aft point of= =20 lift).  Remember that the same is true with the 200/300 series wings.= =20 (hint: aft CG wallow may be reduced by taking a bit of reflex out of t= he=20 wing).  Remember also that slow speed operation with flaps=20 fully reflexed requires a high AOA to compensate for the reduction in = lift=20 from the reflex.  Be careful out there.
 
Max lift, min drag at 70-100 KIAS is with the flaps at TO position (ab= out=20 +10 degrees down from full reflex).  After about +17 degrees down= from=20 full reflex, the flaps seem to merely add drag that is useful in higher tha= n 3=20 degree descent angles (preservation of kinetic energy) - keeping the s= peed=20 controlled (below 100 KIAS) at low power settings and also keeping&nbs= p;the=20 nose low.
 
Maybe next time I will record AOA digital display data in some of thes= e=20 configurations.
 
Scott Krueger
N92EX
 
Note 1: In an Air Venture x-ctry race, KARR was a turning checkpoint t= hat=20 required I descend over the monitor.  In that descent I ran throu= gh a=20 mass of little black bugs (so did others) and my return to level flight as = the=20 same race power resulted in speeds 6-7 KIAS less than before the=20 encounter.  Later, I noted that the splattered bugs were very close=20 together (less than a 1/4") and had completely messed up the laminar flow a= t the=20 leading edge of the wings.  Slow downs have also occurred in=20 flight through rain.
 
Note 2: Certain 320/360 racers experimented with more reflex with the= =20 conclusion that there was no significant improvement in speed.
 
 
 
In a message dated 4/13/2012 11:02:14 P.M. Central Daylight Time,=20 egraylaw@swbell.net writes:
=

I have the exact con= cerns=20 reported by Rob Stevens in Australia.  Since the manual is vague on= =20 cruise flap settings, can some experienced L320-360 fliers help us with w= hat=20 is the best cruise settings?  Is it -7deg. , -10deg., or somewhere= =20 else.  Since construction variances can create different =E2=80=9Cfa= ired-in=20 positions=E2=80=9D, is there an angle which can be measured from the top = or bottom=20 wing surface?  Can anyone explain the aerodynamic reasons for reflex= ed=20 flaps?  Rob and I need help!

Ed Gray Dallas = L360=20 N77ZG XP360 Silver Hawk injection MT 3 blade prop Dual Dynon Skyview=20 SL30

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