X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 16 Jul 2012 08:12:34 -0400 Message-ID: X-Original-Return-Path: Received: from blu0-omc3-s2.blu0.hotmail.com ([65.55.116.77] verified) by logan.com (CommuniGate Pro SMTP 5.4.6) with ESMTP id 5651243 for lml@lancaironline.net; Fri, 13 Jul 2012 22:37:08 -0400 Received-SPF: neutral receiver=logan.com; client-ip=65.55.116.77; envelope-from=frederickmoreno@bigpond.com Received: from BLU0-SMTP422 ([65.55.116.73]) by blu0-omc3-s2.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675); Fri, 13 Jul 2012 19:36:32 -0700 X-Originating-IP: [58.165.97.56] X-Originating-Email: [frederickmoreno@bigpond.com] X-Original-Message-ID: X-Original-Return-Path: frederickmoreno@bigpond.com Received: from Razzle ([58.165.97.56]) by BLU0-SMTP422.phx.gbl over TLS secured channel with Microsoft SMTPSVC(6.0.3790.4675); Fri, 13 Jul 2012 19:36:30 -0700 MIME-Version: 1.0 X-Original-Date: Sat, 14 Jul 2012 10:36:18 +0800 Content-Type: multipart/alternative; charset="ISO-8859-1"; boundary="------------Boundary-00=_IWP4M5C5BHK000000000" X-Mailer: IncrediMail (6295203) From: Frederick Moreno References: X-FID: FLAVOR00-NONE-0000-0000-000000000000 X-Priority: 3 X-Original-To: "Lancair Mail (lml@lancaironline.net)" Subject: Re: [LML] Flutter/VNE X-OriginalArrivalTime: 14 Jul 2012 02:36:30.0974 (UTC) FILETIME=[79FDA9E0:01CD6169] --------------Boundary-00=_IWP4M5C5BHK000000000 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable When preparing Brent Regan's IVP for the Aircraft Spruce race from Colora= do to OSH in 1996, we did a lot of flight testing, drag reduction work, and research including discussions with Lancair and the structural analyst fo= r the LIV, Martin Hollman. =0D =0D In the early days fuel tanks were enlarged to 92 gallons by adding additional tank volume near the wing tips. Prior to the tank enlargement= , Vne was 274 knots indicated up to 25,000 based on his flutter analysis, b= ut the effect of the tank volume increase was unknown. =0D =0D A group of builders chipped in to do the revised analysis which showed th= at the added fuel was detrimental, but burning fuel off during climb was adequate to maintain required margins as long as the fuel came out of bot= h tanks. =0D =0D The Mach limit was not explored, but dive testing to Mach =3D 0.6 had bee= n completed. =0D =0D In preparation for the race, I computed a series of tables that would provide Mach numbers from OAT, corrected for compressibility and friction= al heating, these being the days pre-Chelton. We established hard limits of 274 knots IAS and Mach =3D 0.58 for the descent. =0D =0D Brent's plane uses a modified Lycoming 540 with 8.5:1 pistons (if memory = is correct) and specially selected turbos that allowed us to race at 90+% po= wer 30 GPH, 320 knots TAS at 27,000 feet, Mach 0.52 when racing in temperatures well above standard. As I recall, Brent said his engine produced about 375 HP at 100%, corrected to standard conditions.=0D =0D Mixture management was crucial in our attempt to break the San Francisco = to Denver record (set by the original Lancair IV) as we had barely enough fu= el for the planned trip after the long climb to 27,000 with way above standa= rd summer air temperatures before passing over San Francisco. We constantly diddled mixture, temperature and speed and the engine situation was never stable. Flying through cirrus clouds we got a big static discharge that whacked everything and even reset the digital clock. But when it became clear we would be two minutes late, we canceled, reduced power, and descended in a civil fashion to Jeffco Airport. We did not have the required tailwinds to break the record which was set with a better boost from the winds aloft.=0D =0D The NExt day was the race to OSH. It was a shorter leg, so we could pour= on the fuel, keep things cooler, the OAT was also a bit lower, so we could nudge up the power a bit. The descent was very flat at first to stay bel= ow Mach 0.58, steepening as the air got thicker and warmer which allowed st= ill higher power setting and higher IAS yielding better cooling. The speed wa= s adjusted by controlling pitch to yield Mach 0.58 at 100% power until the = IAS reached 274 knots, and that was held the rest of the way down. =0D =0D A Lancair IV going down hill at full power and 274 knots (in and out of I= MC) sounds very different than it does in cruise. It made the hair on the b= ack of my neck stand on end. We won the race that year at just a hair under = 300 knots from brake release to destination.=0D =0D =0D Fred Moreno =0D =0D =0D -------Original Message-------=0D =0D From: Dennis Ramsey=0D Date: 14/07/2012 8:02:55 AM=0D To: lml@lancaironline.net=0D Subject: [LML] Flutter/VNE=0D =0D So if VNE is an indicated airspeed (which it clearly is), then is it safe= to assume that one would have flutter margins if a IV was in a descent from = FL 290 and was indicating 276 knots as it passed through FL250. I think everyone agrees that flutter is a function of TAS. So what we really nee= d to know is what TAS that flutter should be expected on the various Lancai= r airframes. If you cannot get into a flutter situation all on the models = if you stay below VNE at the service ceiling, then its a moot point and all = we need to know is VNE. But if trouble can begin at speeds below VNE at hi= gh altitudes, then we really need to know the flutter TAS for the models.=0D =0D Dennis Ramsey=0D Lancair IV =0D 65 hours=0D =20 --------------Boundary-00=_IWP4M5C5BHK000000000 Content-Type: text/html; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable
When preparing Brent Regan's IVP for the Aircraft Spr= uce race from Colorado to OSH in 1996, we did a lot of flight t= esting, drag reduction work, and research including discussions= with Lancair and the structural analyst for the LIV, Martin Hollman= =2E 
 
In the early days fuel tanks were enlarged to 92 gallons by adding a= dditional tank volume near the wing tips.  Prior to t= he tank enlargement, Vne was 274 knots indicated up to 25,000 based on hi= s flutter analysis, but the effect of the tank volume increase was u= nknown. 
 
A group of builders chipped in to do the revised anal= ysis which showed that the added fuel was detrimental, but burning fuel o= ff during climb was adequate to maintain required margins as lo= ng as the fuel came out of both tanks.
 
The Mach limit was not explored, but dive testing to Mach =3D 0= =2E6 had been completed.
 
In preparation for the race, I computed a series of tables that woul= d provide Mach numbers from OAT, corrected for compressibility = and frictional heating, these being the days pre-Chelton.  We establ= ished hard limits of 274 knots IAS and Mach =3D 0.58 for the  descen= t.
 
Brent's plane uses a modified Lycoming 540 with 8.5:1 pistons (= if memory is correct) and specially selected turbos that allowed us to&nb= sp;race at 90+% power, 30 GPH,  320 knots TAS at 27,000 feet, Mach 0= =2E52 when racing in temperatures well above standard.   A= s I recall, Brent said his engine produced about 375 HP at 100%, correcte= d to standard conditions.
 
Mixture management was crucial in our attempt to break the San Franc= isco to Denver record (set by the original Lancair IV) as we had barely e= nough fuel for the planned trip after the long climb to 27= ,000 with way above standard summer air temperatures before passing&= nbsp;over San Francisco.  We constantly diddled mixture, temperature= and speed and the engine situation was never stable.  Flying throug= h  cirrus clouds we got a big static discharge that whacked everythi= ng and even reset the digital clock.  But when it became clear = we would be two minutes late, we canceled, reduced power, and descended i= n a civil fashion to Jeffco Airport.   We did not have the requ= ired tailwinds to break the record which was set with a better boost from= the winds aloft.
 
The NExt day was the race to OSH.  It was a shorter leg, s= o we could pour on the fuel, keep things cooler, the OAT was al= so a bit lower, so we could nudge up the power a bit.  The descent w= as very flat at first to stay below Mach 0.58,  steepening as t= he air got thicker and warmer which allowed still higher power setti= ng and higher IAS yielding better cooling. The speed was a= djusted by controlling pitch to yield Mach 0.58 at 100% power u= ntil the IAS reached 274 knots, and that was held the rest of the way dow= n. 
 
A Lancair IV going down hill at full power and 274 knots (in and out= of IMC) sounds very different than it does in = cruise.  It  made the hair on the back of my neck stand on=  end.  We won the race that year at just a hair under= 300 knots from brake release to destination.
 
 
Fred Moreno   
 
 
-= ------Original Message-------
 
Date: 14/07/2012 8= :02:55 AM
Subject: [LML] Flu= tter/VNE
 
So if VNE is an indicated airspeed (which it clearly is), then is it= safe to assume that one would have flutter margins if a IV was in a desc= ent from  FL 290 and was indicating 276 knots as it passed through F= L250.  I think everyone agrees that flutter is a function of TA= S.  So what we really need to know is what TAS that flutter should b= e expected on the various Lancair airframes.  If you cannot get= into a flutter situation all on the models if you stay below VNE at the = service ceiling, then its a moot point and all we need to know is VNE.&nb= sp;  But if trouble can begin at speeds below VNE at high altitudes,= then we really need to know the flutter TAS for the models.
 
Dennis Ramsey
Lancair IV 
65 hours
 
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