X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 19 Jun 2011 11:30:41 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-dupuy.atl.sa.earthlink.net ([209.86.89.62] verified) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTP id 5024953 for lml@lancaironline.net; Sat, 18 Jun 2011 22:45:04 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.62; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=uD6KFsT883IxRz5SzRNc+/xFYfx+NrtWjbq0JTAeFEOGv7c74k1GcR+ALJKJS2P9; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [66.201.52.88] (helo=[10.71.1.21]) by elasmtp-dupuy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1QY7zy-0004DZ-Fk for lml@lancaironline.net; Sat, 18 Jun 2011 22:44:30 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: multipart/alternative; boundary=Apple-Mail-667--568211747 Subject: Re: [LML] Re: And how about a full feathering prop? X-Original-Date: Sat, 18 Jun 2011 19:44:29 -0700 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1082) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9400cd1bc3d3788bc4ebade4cbb08504f2b350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 66.201.52.88 --Apple-Mail-667--568211747 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Those are very interesting numbers. I think Scotty's got a chart that shows that the advantage of a full = feathering prop over constant speed is pretty marginal. After I wrote my last post I realized that the 120 knots/600 fpm number = I had in my head was from a IV-PT which has less drag in the nose than a IVP. Keeping that in mind, Bob's numbers are quite = impressive. Bob points out that the prop is a nice adjustable speed brake when = windmilling. I have not tried it but I suppose a fully featherable prop could do the = same thing IF you don't just yank it all the way back all at once. Once you lose oil pressure you can't do anything with the fully = featherable prop unless you get one with an unfeathering accumulator (I = don't know of an approved one for the IVP - maybe someone else does). Keeping the prop windmilling will keep you in oil pressure if you don't = have an oil leak. Colyn On Jun 18, 2011, at 5:32 PM, Robert R Pastusek wrote: > Ronald wrote: > =20 > For what I have gathered so far the lancair 4p has a glide ratio = similar like a piano LOL In other words if the engine quits then open = the door, throw out your keys because there is where you land LOL > =20 > Well, this might not be true, or is it?=20 > =20 > So how about the full feathering prop ? Does anyone have experience = with the before and after installation? How much they cost and data? > =20 > And I needed to respond to this=85 > =20 > My IV-P has a glide ratio (at 120 KIAS) of between 5:1 and 20:1, = depending on configuration. The difference is truly = amazing/impressive/sobering=85 depending on your situation and mind set. = With the gear and flaps down and the RPM at max (prop all the way in), = the glide ratio approximates that of a brick=85not really, but you=92re = coming down so fast relative to forward progress that it=92s difficult = to plan and execute a planned touchdown (at least for me). With the gear = and flaps up, AND THE PROP CONTROL ALL THE WAY OUT, my glide ratio at = gross weight is approximately 18:1, increasing to a bit better than 20:1 = at 800# under gross. At this glide ratio, the performance and =93sight = picture=94 approximates that of some gliders. It=92s easy to plan and = execute an approach and landing to a pre-planned spot=85ideally a = runway. I have practiced this many times from various = altitudes/distances from the airport to a full stop on the runway, using = the gear to increase my descent rate, and then the flaps and/or the prop = control to adjust the touchdown point. Using the prop control is ideal = because the drag effect/descent rate increase almost immediately = reversible by pushing it back in. Not so with the flaps. One feature of = my Chelton EFIS is a wind-adjusted glide range predictor. I have tested = this many times starting at altitudes up to 17,500=92 and (set at 18:1) = gives me a very accurate and immediate sight picture of airfields within = glide range. If it=92s within the green circle, I can turn toward an = airfield and execute a safe landing there. My MT 4-blade is not full = feathering, but allows the engine to run at approximately 700 RPM when = at idle and the RPM set to min. I believe this is pretty close to 0 = thrust, as the engine idles at approximately 600 RPM on the ground.=20 > =20 > So, in summary, the throw out the keys and follow them down scenario = can be executed if you really want to go down, but a planned glide at = 120 KIAS (very close to best glide for my airplane) in clean = configuration yields approximately the performance of a 2-place sail = plane=97and you have the ability to transition easily between these = limits as needed. Try it; you=92ll be impressed. > =20 > Bob > =20 > PS: I considered and rejected a full feathering prop for what I have. = Wouldn=92t trade for any amount of money=85 --Apple-Mail-667--568211747 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Those are very interesting numbers.
I think = Scotty's got a chart that shows that the advantage of a full feathering = prop over constant speed is pretty = marginal.

After I wrote my last post I realized = that the 120 knots/600 fpm number I had in my head was from a IV-PT = which has less drag in the
nose than a IVP.  Keeping that = in mind, Bob's numbers are quite = impressive.

Bob points out that the prop is a = nice adjustable speed brake when windmilling.
I have not tried = it but I suppose a fully featherable prop could do the same thing IF you = don't just yank it all the way back all at once.
Once you lose = oil pressure you can't do anything with the fully featherable prop = unless you get one with an unfeathering accumulator (I don't know of an = approved one for the IVP - maybe someone else does).
Keeping = the prop windmilling will keep you in oil pressure if you don't have an = oil = leak.

Colyn


On Jun 18, 2011, at 5:32 PM, Robert R Pastusek wrote:

Ronald = wrote:
For what I have gathered so far the lancair 4p has a glide = ratio similar like a piano LOL In other words if the engine quits then = open the door, throw out your keys because there is where you land = LOL
Well, this might not be true, or is = it? 
 
So how about the full feathering prop ? Does = anyone have experience with the before and after installation?  How = much they cost and data?
And I needed to respond to = this=85
My = IV-P has a glide ratio (at 120 KIAS) of between 5:1 and 20:1, depending = on configuration. The difference is truly amazing/impressive/sobering=85 = depending on your situation and mind set. With the gear and flaps down = and the RPM at max (prop all the way in), the glide ratio approximates = that of a brick=85not really, but you=92re coming down so fast relative = to forward progress that it=92s difficult to plan and execute a planned = touchdown (at least for me). With the gear and flaps up, AND THE PROP = CONTROL ALL THE WAY OUT, my glide ratio at gross weight is approximately = 18:1, increasing to a bit better than 20:1 at 800# under gross. At this = glide ratio, the performance and =93sight picture=94 approximates that = of some gliders. It=92s easy to plan and execute an approach and landing = to a pre-planned spot=85ideally a runway. I have practiced this many = times from various altitudes/distances from the airport to a full stop = on the runway, using the gear to increase my descent rate, and then the = flaps and/or the prop control to adjust the touchdown point. Using the = prop control is ideal because the drag effect/descent rate increase = almost immediately reversible by pushing it back in. Not so with the = flaps.  One feature of my = Chelton EFIS is a wind-adjusted glide range predictor. I have tested = this many times starting at altitudes up to 17,500=92 and  (set at = 18:1) gives me a very accurate and immediate sight picture of airfields = within glide range. If it=92s within the green circle, I can turn toward = an airfield and execute a safe landing there. My MT 4-blade is not full = feathering, but allows the engine to run at approximately 700 RPM when = at idle and the RPM set to min. I believe this is pretty close to 0 = thrust, as the engine idles at approximately 600 RPM on the ground. 
So, = in summary, the throw out the keys and follow them down scenario can be = executed if you really want to go down, but a planned glide at 120 KIAS = (very close to best glide for my airplane) in clean configuration yields = approximately the performance of a 2-place sail plane=97and you have the = ability to transition easily between these limits as needed. Try it; = you=92ll be  impressed.<= /span>
PS: I = considered and rejected a full feathering prop for what I have. = Wouldn=92t  trade for any amount = of = money=85

= --Apple-Mail-667--568211747--