X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 16 Apr 2012 20:55:46 -0400 Message-ID: X-Original-Return-Path: Received: from eu1sys200aog119.obsmtp.com ([207.126.144.147] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with SMTPS id 5484154 for lml@lancaironline.net; Mon, 16 Apr 2012 19:36:30 -0400 Received-SPF: none receiver=logan.com; client-ip=207.126.144.147; envelope-from=lancair@meier.cc Received: from kdn6.futureweb.at ([85.125.90.138]) (using TLSv1) by eu1sys200aob119.postini.com ([207.126.147.11]) with SMTP ID DSNKT4ys2LAjBKuWMunNXabVKPtJAhN57X50@postini.com; Mon, 16 Apr 2012 23:36:29 UTC Received: from [192.168.168.8] (sjon195149219169.surfer.sjon.at [195.149.219.169]) (authenticated bits=0) by kdn6.futureweb.at (8.14.4/8.14.4) with ESMTP id q3GNZoVU032232 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO) for ; Tue, 17 Apr 2012 01:35:51 +0200 From: Christian Meier Mime-Version: 1.0 (Apple Message framework v1257) Content-Type: multipart/alternative; boundary="Apple-Mail=_BC79840B-0B3A-4AAF-BA54-7B1B393D007F" Subject: Re: [LML] L320 flap setting X-Original-Date: Tue, 17 Apr 2012 01:35:50 +0200 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1257) --Apple-Mail=_BC79840B-0B3A-4AAF-BA54-7B1B393D007F Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Scott, this is very interesting! Could you write down some more flap positions which you use for take off = and landing in different take-off weight configurations. And also when you arrive in the landing-circuit in cruise speed. How = best to slow down to flap speed in the downwind. Actually when I arrive from cruise, I put the engine to idle pull nose = up to reach 120kt drop gear, set flaps to +10 (17 from full reflex)=20 and drop nose and put back low power setting. After all this I get my = 100kt and turn to base leg. In final I use +20 / +25 and will also land in this setting. My runway is 700m long and has a 1% down slope and is = located in 2200ft alt. If I use more flaps to land the plane won't sit = down. Speed over the fence is 90-85kts because of shear winds just before the = runway... What speeds do you use in short final? Does it help to stick some gap seals over the hinges of flap and aileron = like all the gliders do? Christian OE-CCM Am 16.04.2012 um 14:13 schrieb Sky2high@aol.com: > Ed, Rob, et al, > =20 > The purpose of reflexed flaps (wing TE) is for reduction of drag at = cruise speeds. After certain minimum speeds, induced drag is lessened = by reducing lift through a reflexed TE (also reducing anti lift at the = horiz stab). Parasitic drag in a laminar flow environment may also be = reduced by reattaching the airflow at the reflexed flap. The basic fat = wing design helps when the leading edge gets dirty (disrupts laminar = flow) because lift is only slightly reduced but draq increases (ice, = rain, bugs - see note 1). This is as opposed to a thin laminar wing = which may lose lift when dirty. The 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 speeds require more nose down trim (less negative AOA at the = horiz stab) and lower speeds require a higher angle of attack to achieve = adequate lift. In general, below a max Vf (160 to 140 KIAS), the flaps = may be taken out of reflex (to 0 degrees) where the attitude of the = airplane can be changed by up to 6 degrees nose down (as measured = digitally at the longeron) and this will require substantial nose up = trim for level flight while the speed drops (about 15 KIAS) from = increased drag. For this wing, further reflexing 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 tailless (and non-canard) aircraft. In such aircraft, changes in CG = are compensated for by changing the angle of reflex (changes fwd/aft = point of lift). Remember that the same is true with the 200/300 series = wings. (hint: aft CG wallow may be reduced by taking a bit of reflex out = of the wing). Remember also that slow speed operation with flaps fully = reflexed requires a high AOA to compensate for the reduction in lift = from the reflex. Be careful out there. > =20 > Max lift, min drag at 70-100 KIAS is with the flaps at TO position = (about +10 degrees down from full reflex). After about +17 degrees down = from full reflex, the flaps seem to merely add drag that is useful in = higher than 3 degree descent angles (preservation of kinetic energy) - = keeping the speed controlled (below 100 KIAS) at low power settings and = also keeping the nose low. > =20 > Maybe next time I will record AOA digital display data in some of = these configurations. > =20 > Scott Krueger > N92EX > =20 > Note 1: In an Air Venture x-ctry race, KARR was a turning checkpoint = that required I descend over the monitor. In that descent I ran through = a mass of little black bugs (so did others) and my return to level = flight as the same race power resulted in speeds 6-7 KIAS less than = before the encounter. Later, I noted that the splattered bugs were very = close together (less than a 1/4") and had completely messed up the = laminar flow at the leading edge 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 = conclusion that there was no significant improvement in speed. > =20 > =20 --Apple-Mail=_BC79840B-0B3A-4AAF-BA54-7B1B393D007F Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii Sky2high@aol.com:
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 = lessened=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 = but=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 = allows our=20 grocery cart wheels to be stowed within. 
 
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=20 stab) and lower speeds require a higher angle of attack to achieve = adequate=20 lift.  In general, below a max Vf (160 to 140 KIAS), the flaps = may 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 = digitally at=20 the longeron) and this will require substantial nose up trim for level = flight=20 while the speed drops (about 15 KIAS) from increased drag.  For = this wing,=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 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.=20 (hint: aft CG wallow may be reduced by taking a bit of reflex out = of the=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 = (about=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 = 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=20 nose low.
 
Maybe next time I will record AOA digital display data in some of = these=20 configurations.
 
Scott Krueger
N92EX
 
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=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 at 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.
 
 

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