X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 19 Jun 2011 19:56:11 -0400 Message-ID: X-Original-Return-Path: Received: from imr-db03.mx.aol.com ([205.188.91.97] verified) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTP id 5025318 for lml@lancaironline.net; Sun, 19 Jun 2011 12:09:38 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.91.97; envelope-from=Sky2high@aol.com Received: from imo-ma04.mx.aol.com (imo-ma04.mx.aol.com [64.12.78.139]) by imr-db03.mx.aol.com (8.14.1/8.14.1) with ESMTP id p5JG90H5005017 for ; Sun, 19 Jun 2011 12:09:00 -0400 Received: from Sky2high@aol.com by imo-ma04.mx.aol.com (mail_out_v42.9.) id q.11c1.491ef4 (55741) for ; Sun, 19 Jun 2011 12:08:59 -0400 (EDT) Received: from magic-m27.mail.aol.com (magic-m27.mail.aol.com [172.20.22.200]) by cia-md04.mx.aol.com (v129.10) with ESMTP id MAILCIAMD048-d9bd4dfe1f1a197; Sun, 19 Jun 2011 12:08:58 -0400 From: Sky2high@aol.com X-Original-Message-ID: <19397.418179ba.3b2f791a@aol.com> X-Original-Date: Sun, 19 Jun 2011 12:08:58 EDT Subject: Re: [LML] Re: And how about a full feathering prop? X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="part1_19397.418179ba.3b2f791a_boundary" X-Mailer: AOL 9.6 sub 5004 X-AOL-IP: 24.15.17.119 X-Spam-Flag:NO X-AOL-SENDER: Sky2high@aol.com --part1_19397.418179ba.3b2f791a_boundary Content-Type: multipart/related; boundary="part1_19397.418179ba.3b2f791a_rel_boundary" --part1_19397.418179ba.3b2f791a_rel_boundary Content-Type: multipart/alternative; boundary="19397.418179ba_alt_bound" --19397.418179ba_alt_bound Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Colyn, =20 Maybe you are referring to the included chart from "Aerodynamics for Nava= l=20 Aviators". The Hartzell prop for the 320 engine has a pitch range of 12= =20 to 40 degrees. If the engine has not seized (stationary prop), pulling= back=20 to coarse pitch results in almost the same drag reduction as a feathered= =20 prop. Slick Lancairs are affected greatly by such drag as there are no= =20 struts, rivets or fat wings to moderate the effect. =20 In my 320, zero thrust, cruise pitch resulted in a 1500 fpm descent at =20 best glide (about 107 KIAS via AOA) and pulling back to coarse pitch the= =20 descent rate decreased to about 400-500 fpm. It was an eye opener. =20 =20 Grayhawk =20 =20 In a message dated 6/19/2011 10:31:36 A.M. Central Daylight Time, =20 colyncase@earthlink.net writes: Those are very interesting numbers. =20 I think Scotty's got a chart that shows that the advantage of a full =20 feathering prop over constant speed is pretty marginal. After I wrote my last post I realized that the 120 knots/600 fpm number I= =20 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 impressiv= e. Bob points out that the prop is a nice adjustable speed brake when =20 windmilling. I have not tried it but I suppose a fully featherable prop could do the = =20 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 =20 featherable prop unless you get one with an unfeathering accumulator (I do= n't know of=20 an approved one for the IVP - maybe someone else does). Keeping the prop windmilling will keep you in oil pressure if you don't = =20 have an oil leak. Colyn On Jun 18, 2011, at 5:32 PM, Robert R Pastusek wrote: =20 =20 Ronald wrote: =20 =20 For what I have gathered so far the lancair 4p has a glide ratio similar= =20 like a piano LOL In other words if the engine quits then open the door,= =20 throw out your keys because there is where you land LOL =20 =20 Well, this might not be true, or is it?=20 =20 =20 So how about the full feathering prop ? Does anyone have experience with= =20 the before and after installation? How much they cost and data? =20 =20 And I needed to respond to this=E2=80=A6 =20 My IV-P has a glide ratio (at 120 KIAS) of between 5:1 and 20:1, dependin= g=20 on configuration. The difference is truly amazing/impressive/sobering=E2= =80=A6 =20 depending on your situation and mind set. With the gear and flaps down and= =20 the RPM at max (prop all the way in), the glide ratio approximates that of= a =20 brick=E2=80=A6not really, but you=E2=80=99re coming down so fast relative= to forward =20 progress that it=E2=80=99s difficult to plan and execute a planned touchdo= wn (at least=20 for me). With the gear and flaps up, AND THE PROP CONTROL ALL THE WAY OUT= ,=20 my glide ratio at gross weight is approximately 18:1, increasing to a bit= =20 better than 20:1 at 800# under gross. At this glide ratio, the performanc= e=20 and =E2=80=9Csight picture=E2=80=9D approximates that of some gliders. It= =E2=80=99s easy to plan and=20 execute an approach and landing to a pre-planned spot=E2=80=A6ideally a = runway. I=20 have practiced this many times from various altitudes/distances from the= =20 airport to a full stop on the runway, using the gear to increase my desce= nt=20 rate, and then the flaps and/or the prop control to adjust the touchdown= =20 point. Using the prop control is ideal because the drag effect/descent ra= te=20 increase almost immediately reversible by pushing it back in. Not so with= the=20 flaps. One feature of my Chelton EFIS is a wind-adjusted glide range=20 predictor. I have tested this many times starting at altitudes up to 17,5= 00=E2=80=99=20 and (set at 18:1) gives me a very accurate and immediate sight picture= of=20 airfields within glide range. If it=E2=80=99s within the green circle, I= can turn=20 toward an airfield and execute a safe landing there. My MT 4-blade is not= full=20 feathering, but allows the engine to run at approximately 700 RPM when at= =20 idle and the RPM set to min. I believe this is pretty close to 0 thrust,= as=20 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= =20 be executed if you really want to go down, but a planned glide at 120 KIA= S =20 (very close to best glide for my airplane) in clean configuration yields= =20 approximately the performance of a 2-place sail plane=E2=80=94and you have= the =20 ability to transition easily between these limits as needed. Try it; you= =E2=80=99ll be =20 impressed. =20 Bob =20 PS: I considered and rejected a full feathering prop for what I have. =20 Wouldn=E2=80=99t trade for any amount of money=E2=80=A6 =3D --19397.418179ba_alt_bound Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en <= FONT id=3Drole_document color=3D#000000 size=3D2 face=3DArial>
Colyn,
 
Maybe you are referring to the included chart from "Aerodyn= amics=20 for Naval Aviators".  The Hartzell prop for the 320 engine has a pitc= h=20 range of 12 to 40 degrees.  If the engine has not seized (stationary= prop),=20 pulling back to coarse pitch results in almost the same drag reduction as= a=20 feathered prop.  Slick Lancairs are affected greatly by such drag as= there=20 are no struts, rivets or fat wings to moderate the effect.
 
In my 320, zero thrust, cruise pitch resulted in a 1500 fpm desc= ent at=20 best glide (about 107 KIAS via AOA) and pulling back to coarse pitch the= descent=20 rate decreased to about 400-500 fpm.  It was an eye opener.
 
 
Grayhawk
 
In a message dated 6/19/2011 10:31:36 A.M. Central Daylight Time,=20 colyncase@earthlink.net writes:
Those=20 are very interesting numbers.=20
I think Scotty's got a chart that shows that the advantage of a ful= l=20 feathering prop over constant speed is pretty marginal.

After I wrote my last post I realized that the 120 knots/600 fpm nu= mber I=20 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 quit= e=20 impressive.

Bob points out that the prop is a nice adjustable speed brake when= =20 windmilling.
I have not tried it but I suppose a fully featherable prop could do= the=20 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=20 featherable prop unless you get one with an unfeathering accumulator (I= don't=20 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=20 have an oil leak.

Colyn


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