X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 22 Aug 2013 07:58:41 -0400 Message-ID: X-Original-Return-Path: Received: from mail-pd0-f174.google.com ([209.85.192.174] verified) by logan.com (CommuniGate Pro SMTP 6.0.6) with ESMTPS id 6436444 for lml@lancaironline.net; Wed, 21 Aug 2013 16:03:10 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.192.174; envelope-from=legacyl2k@gmail.com Received: by mail-pd0-f174.google.com with SMTP id y13so877574pdi.33 for ; Wed, 21 Aug 2013 13:02:34 -0700 (PDT) X-Received: by 10.68.36.132 with SMTP id q4mr1467747pbj.118.1377115353863; Wed, 21 Aug 2013 13:02:33 -0700 (PDT) X-Original-Return-Path: Received: from [192.168.0.3] (174-26-153-238.phnx.qwest.net. [174.26.153.238]) by mx.google.com with ESMTPSA id pq1sm10116353pbb.26.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 21 Aug 2013 13:02:33 -0700 (PDT) Subject: Re: [LML] Re: Flaps on take-off? References: From: Mike Content-Type: multipart/alternative; boundary=Apple-Mail-A890F5C4-26A5-4AC2-A54A-9946DF3C129A X-Mailer: iPad Mail (9B206) In-Reply-To: X-Original-Message-Id: <5EA4619D-50FD-4FA0-9106-D6D5CFAA1F14@gmail.com> X-Original-Date: Wed, 21 Aug 2013 13:02:30 -0700 X-Original-To: Lancair Mailing List Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) --Apple-Mail-A890F5C4-26A5-4AC2-A54A-9946DF3C129A Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Gary, As for the basic question; to use or not use flaps on takeoff, every airplan= e is different. I have found that with the Lancair Legacy takeoff with flap= s is IMO the better way of doing a normal takeoff. At flaps 10 (10 degrees)= the parasitic drag at takeoff speed is very small, the induced drag is less= , and flaps 10 also lowers your stall speed aprox 10 knots IAS. Adding more= flaps beyond 10 to the Legacy only adds more drag and shifts the center of l= ift aft. So flaps 10 yields a better climb rate at slower speed then taking= the time to accelerate 10 knots more during this critical part of the climb= out. Once you reach 1000ft AGL accelerate and retract flap on speed. If y= ou loose the engine you are at the best flap selection for the best stall s= peed and sink. As for your second question I think your mostly on the mark. Some thoughts,= first the reason prop control use during an engine out hasn't be taught, is= mostly do to low wing loaded airplanes (Cessna and Piper) do not gain as mu= ch by doing this. Another thought is if you loose oil pressure you can not c= ontrol the prop. Another thought is If the prop slows and stops turning tha= t will improve your glide even more but on a Lancair with its high glide sp= eed is not likely. Other choices are full feather or counterweighted props.= Which do this for you automatically. The downside is you get course pitch= or feather in the event of loss of oil pressure to the prop.=20 Mike Larkin Sent from my iPad On Aug 21, 2013, at 9:46 AM, Gary Casey wrote: > I guess I'll jump in here, but my comments might not be worth 2 cents :-) >=20 > The original question was about whether to use flaps on takeoff, and like m= ost things, it is a compromise. A logical objective might be to get to Vy a= s soon as possible, and that would probably be without flaps. But the altit= ude at that point would probably be less than if you used flaps. Yes, the w= orkload is less without flaps, and that is a good thing. The time spent at l= ow altitude would be more and that's a bad thing. And the on-runway speed w= ould be higher. You pays your money and you takes your choice. >=20 > The second question was about whether prop control is an effective way to r= educe engine-out drag. Bob and Steve are correct, but the actual ability to= control pitch depends on at least 4 things. First, the airspeed has to be h= igh enough to be able to input enough power to the prop to spin the engine (= almost always the case). Next, the prop pitch stops have allow enough range= to make a difference (almost always the case). Then the leakage between th= e governor and the prop has to be low enough to allow the governor pump, boo= sted by the engine oil pump, to be able to move the prop toward the coarse p= osition (in my experience this is also possible). Finally, the governor low= -speed stop must be set low enough for it to take action. In every plane I'= ve tried this on, it works. Granted, with the prop control in the full out p= osition, the engine speed will not drop to idle, and that's probably limited= by the low-rpm stop on the governor and/or the high pitch stop on the prop.= It might also be limited by the drop in oil pressure as the engine slows d= own. Regardless, it works and it is significant. Why going to low rpm hasn= 't been taught in most curricula, I have no idea. It should. >=20 > Gary=20 >=20 >=20 >=20 >=20 > I'm not so sure at idle power in flight one can pull the prop back(coarse)= =3D > that much. Just try changing rpm's at low rpm's during run-up . I have t= o=3D > be at around 16-1800 to get the prop to cycle at run-up. Oil pressure play= =3D > 's a big part of the governor's ability to move the prop. While at idle po= w=3D > er one may have high enough oil pressure but surly not enough volume as 1= 8=3D > 00 + RPM. There will be oil leakage around the front main bearing going to= =3D > the prop. Off field landings or a return to airport is most likely loss o= f=3D > power of some sort ( low rpm) wind milling prop. >=20 > Most single engine controllable props are pressure to increase pitch, feat= h=3D > ering props are pressure to decrease pitch, unless they are electric. >=20 > I may be wrong but that's the way I understand it. >=20 >=20 > Steve Alderman N25SA 360 >=20 >=20 >=20 > Wolfgang, > My MT prop/governor does not work as you describe below. Specifically, if t= =3D > he engine is turning (with oil pressure), I can control RPM within the mec= h=3D > anical stop limits built into the prop hub, and total power/drag. Idle pow= e=3D > r/min RPM/120 KIAS glide gives me 600-650 RPM; Max RPM in that configurati= o=3D > n gives about 2600 RPM, and the drag increase is significant. At a bit abo= v=3D > e idle power, max RPM is limited to 2700 by the governor, all the way up t= o=3D > max power. Min RPM is maintained as power is added=3DE2=3D80=3DA6for a whi= le=3DE2=3D > =3D80=3DA6but I=3DE2=3D80=3D99ve never gone much above idle power. with th= e prop at m=3D > in RPM=3DE2=3D80=3DA6hard on the engine=3DE2=3D80=3DA6and it=3DE2=3D80=3D9= 9s not a useful dat=3D > apoint, but I suspect it will maintain 650 RPM through full power?? >=20 > Bob --Apple-Mail-A890F5C4-26A5-4AC2-A54A-9946DF3C129A Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=utf-8
Gary,

=
As for the basic question; to use or not use flaps on takeoff, every ai= rplane is different.  I have found that with the Lancair Legacy takeoff= with flaps is IMO the better way of doing a normal takeoff.  At flaps 1= 0 (10 degrees) the parasitic drag at takeoff speed is very small, the induce= d drag is less, and flaps 10 also lowers your stall speed aprox 10 knots IAS= .  Adding more flaps beyond 10 to the Legacy only adds more drag and sh= ifts the center of lift aft.  So flaps 10 yields a better climb rate at= slower speed then taking the time to accelerate 10 knots more during this c= ritical part of the climb out.  Once you reach 1000ft AGL accelerate an= d retract flap on speed.  If you loose the engine you are at the best f= lap selection  for the best stall speed and sink.

<= div>As for your second question I think your mostly on the mark.  Some t= houghts, first the reason prop control use during an engine out hasn't be ta= ught, is mostly do to low wing loaded airplanes (Cessna and Piper) do not ga= in as much by doing this.  Another thought is if you loose oil pressure= you can not control the prop.  Another thought is If the prop slows an= d stops turning that  will improve your glide even more but on a Lancai= r with its high glide speed is not likely.  Other choices are full feat= her or counterweighted props. Which do this for you automatically.  The= downside is  you get course pitch  or feather in the event of los= s of oil pressure to the prop. 

Mike Larkin
Sent from my iPad

On Aug 21, 2013, at 9:46 AM, Gary Casey= <casey.gary@yahoo.com> wr= ote:

I guess I'll jump in here, but my comments m= ight not be worth 2 cents :-)

The original q= uestion was about whether to use flaps on takeoff, and like most things, it i= s a compromise.  A logical objective might be to get to Vy as soon as p= ossible, and that would probably be without flaps.  But the altitude at= that point would probably be less than if you used flaps.  Yes, the wo= rkload is less without flaps, and that is a good thing.  The time spent= at low altitude would be more and that's a bad thing.  And the on-runw= ay speed would be higher.  You pays your money and you takes your choic= e.

The second question was about whether prop control is an effect= ive way to reduce engine-out drag.  Bob and Steve are correct, but the a= ctual ability to control pitch depends on at least 4 things.  First, th= e airspeed has to be high enough to be able to input enough power to the pro= p to spin the engine (almost always the case).  Next, the prop pitch st= ops have allow enough range to make a difference (almost always the case). &= nbsp;Then the leakage between the governor and the prop has to be low enough= to allow the governor pump, boosted by the engine oil pump, to be able to m= ove the prop toward the coarse position (in my experience this is also possible).  Finally, the governor low-speed st= op must be set low enough for it to take action.  In every plane I've t= ried this on, it works.  Granted, with the prop control in the full out= position, the engine speed will not drop to idle, and that's probably limit= ed by the low-rpm stop on the governor and/or the high pitch stop on the pro= p.  It might also be limited by the drop in oil pressure as the engine s= lows down.  Regardless, it works and it is significant.  Why going= to low rpm hasn't been taught in most curricula, I have no idea.  It s= hould.

Gary 




I'm n= ot so sure at idle power in flight one can pull the prop back(coarse) =3D
that much.&nbs= p; Just try changing rpm's at low rpm's during run-up .  I have to=3D
be at around 16-1800 to g= et the prop to cycle at run-up. Oil pressure play=3D
's a big part of the governor's ability to move= the prop. While at idle pow=3D
er one may have high enough oil pressure but surly not enough volume as  18=3D
0= 0 + RPM. There will be oil leakage around the front main bearing going to =3D=
the prop. Off field lan= dings or a return to airport  is most likely loss of=3D
power of some sort ( low  rpm) win= d milling prop.

Most single engine controllable props are pressure to increas= e pitch, feath=3D
ering p= rops are pressure to decrease pitch, unless they are electric.

I may be wrong b= ut that's the way I understand it.


Steve Alderman  N= 25SA    360


=
Wolfgang,
My MT prop/governor does not work as you describe below. Specifically, if t=3D
he engine is turning (with oil pressure), I can c= ontrol RPM within the mech=3D
anical stop limits built into the prop hub, and total power/drag. Idle= powe=3D
r/min RPM/120 KI= AS glide gives me 600-650 RPM; Max RPM in that configuratio=3D
n gives about 2600 RPM, and the d= rag increase is significant. At a bit abov=3D
e idle power, max RPM is limited to 2700 by the govern= or, all the way up to=3D
max power. Min RPM is maintained as power is added=3DE2=3D80=3DA6for a whil= e=3DE2=3D
=3D80=3DA6but I= =3DE2=3D80=3D99ve never gone much above idle power. with the prop at m=3D
in RPM=3DE2=3D80=3DA6hard on the engine=3DE= 2=3D80=3DA6and it=3DE2=3D80=3D99s not a useful dat=3D
apoint, but I suspect it will maintain 650 RPM t= hrough full power??

Bob
= --Apple-Mail-A890F5C4-26A5-4AC2-A54A-9946DF3C129A--