X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from zproxy.gmail.com ([64.233.162.196] verified) by logan.com (CommuniGate Pro SMTP 4.3.6) with ESMTP id 625697 for flyrotary@lancaironline.net; Fri, 05 Aug 2005 09:35:06 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.233.162.196; envelope-from=wdleonard@gmail.com Received: by zproxy.gmail.com with SMTP id z3so343256nzf for ; Fri, 05 Aug 2005 06:34:20 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:in-reply-to:mime-version:content-type:references; b=a5NBXVrkc7LtwU/T2eJKIMImj+1fLMTlujri02iwtKSwrdOae2SAUMiev+jZCd+MHUoUgbISupS07pZYVPTbMtwm/y6OByMxuH+ulny4avhrkBLs0TaGTd4DTto4Jso4Hgykj6tX0YrGT4J4WAzV6bZvDfgkXMPErfKmdDfPVlE= Received: by 10.37.20.51 with SMTP id x51mr1188815nzi; Fri, 05 Aug 2005 06:34:20 -0700 (PDT) Received: by 10.36.9.4 with HTTP; Fri, 5 Aug 2005 06:34:20 -0700 (PDT) Message-ID: <1c23473f0508050634f9edeed@mail.gmail.com> Date: Fri, 5 Aug 2005 06:34:20 -0700 From: David Leonard Reply-To: David Leonard To: Rotary motors in aircraft Subject: Re: [FlyRotary] Vapor lock last weekend In-Reply-To: Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_5779_4645424.1123248860309" References: ------=_Part_5779_4645424.1123248860309 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On 8/4/05, Michael McGee wrote:=20 >=20 > Thought I would share this with everyone since just about everyone is=20 > getting some of this heat wave and most of us aren't used to it. Also, it= =20 > sounds very similar to what Kevin is putting up with in his RV-6A. >=20 > Interesting experience this last Saturday in my RV-4. Interesting because= =20 > it didn't happen at 800 feet where it would have probably made the news b= ut=20 > while I was just starting my takeoff roll. >=20 > Conditions: > 90 deg F, about noon on Saturday > 150 HP Lyc O-320 with carb, gascolator, mechanical and Facet electric=20 > pumps. > Running last winter's last few gallons of auto-gas from my storage tanks. >=20 > Engine was all warmed up from three laps around the pattern shooting=20 > landings at Hillsboro. I had taxied back to the hanger to check for anyth= ing=20 > out of the ordinary since I had recently been working on my carb. Everyth= ing=20 > was okay so I headed back out. >=20 > While setting at an intersection for about 5 minutes waiting to be cleare= d=20 > for takeoff my CHTs were heading for hotter than I like. The wind was at = my=20 > tail so the engine was not getting any cooling. CHT was passing 335 on th= e=20 > Electronics International UBG-16 engine monitor and I was about to call t= he=20 > tower and tell them I was heading back. The controller beat me to it and= =20 > cleared me for takeoff. This airplane normally runs about 325 at power an= d I=20 > have to have a hot day to get it to 350 but I never see it that hot prior= to=20 > takeoff. >=20 > Okay, I thought, a little air through the cowl and we'll be back to=20 > normal. So I answered the controller "6RV cleared for TO", lined up and= =20 > pushed in the throttle. I got almost 2000 rpm and just enough of a push t= o=20 > make it to the next intersection and coast off the runway. It was as if I= =20 > had pulled the mixture. The prop had stopped before I stopped rolling, I = was=20 > looking at everything thinking I had missed something like the fuel valve= =20 > half cocked or left the mixture mostly out (I taxi that way). Feeling stu= pid=20 > I called the tower and said 6RV was NOT taking off.=20 >=20 > After pushing it across the runway threshold I turned the electric pump o= n=20 > and it was obviously empty from the noise it was making. I was on the tan= k=20 > that was 95% full so I switched to the other tank and viola. I recognized= =20 > the sounds of the pump filling the apparently empty fuel system and carb.= =20 > Hopped in and after about 6 blades it lit and ran fine. I called the towe= r=20 > and taxied back to the hanger. Thankful this had not happened at about 80= 0=20 > feet leaving the 5 o'clock news empty handed. >=20 > Pulling the cowling, the carb and fuel pump were so hot you couldn't hold= =20 > your hand on them. The gas had boiled enough that it pushed it back throu= gh=20 > the mechanical pump, gascolator, Facet pump, and tank selector valve. Whe= n I=20 > switched to the "cold" tank out on the intersection the Facet could get h= old=20 > of enough at that point to push fuel back to the engine. From this tank t= he=20 > fuel was cold enough I could get it started and taxi back to the hanger. >=20 > -->KEVIN: > I know you run 100LL but at the temps you are describing, upwards of 400= =20 > degrees, you can vapor lock 100LL, too. I think Dave's right, it could be= =20 > that you are getting some vapor generation on the ground when you're tryi= ng=20 > to run at full power. You mentioned the problem only happens when the eng= ine=20 > is warmed up. >=20 > I'm going to try and duplicate last Saturday's scenario this weekend=20 > (except the takeoff attempt) if the OAT is up enough. >=20 > Bear in mind that since I have never had any problems like this I never= =20 > saw any need for blast tubes on the fuel pump and carb like some people h= ave=20 > done. The cowling on the RV is pretty tight and I have four exhaust pipes= =20 > down there next to the carb, pump, and gascolator. And since I have=20 > thousands of hours running auto gas in various planes, while the extra=20 > volatility certainly contributed I don't believe it's bad stuff and will= =20 > continue to use it. I may keep one tank with mostly 100LL in it for groun= d=20 > ops on the very hot days for extra margin but there were more things than= =20 > fuel type that contributed to what happened.=20 >=20 > Obviously a fuel return line that would allow purging the hot fuel would= =20 > be another fix. We have another RV-4 on the field that has a vapor bleed= =20 > return line for just this reason. >=20 > Well, sorry for the epistle but I thought it was something for people to= =20 > keep in mind while your waiting in a long taxi line at a busy airport.=20 > Especially those of us who rarely see 90 degree ramp temps. It was a real= =20 > eye opener (and I've only got one eye..) P-)=20 >=20 > Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR > 13B in gestation mode, RD-1C, EC-2 Thanks for the report Mike. That is one thing I really like about our=20 rotary set-up: high pressure/high flow fuel systems with a return line. The= =20 chance of vapor lock is essentially zero even with winter blend auto fuel a= t=20 altitude on the hottest day of summer. That and carb ice are two of the=20 biggest issues that cause GA accidents - and we don't have to worry about= =20 them. Loss of control on landing and plain old running out of gas still top= =20 the list however. --=20 Dave Leonard Turbo Rotary RV-6 N4VY http://members.aol.com/_ht_a/rotaryroster/index.html http://members.aol.com/vp4skydoc/index.html ------=_Part_5779_4645424.1123248860309 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline

On 8/4/05, M= ichael McGee <jmpcrftr@tele= port.com> wrote:
Thought I would share this with = everyone since just about everyone is getting some of this heat wave and mo= st of us aren't used to it.  Also, it sounds very similar to what Kevi= n is putting up with in his RV-6A.

Interesting experience this last Saturday in my RV-4.  Interes= ting because it didn't happen at 800 feet where it would have probably made= the news but while I was just starting my takeoff roll.

Conditions:=
90 deg F, about noon on Saturday
150 HP Lyc O-320 with carb, gascolator,= mechanical and Facet electric pumps.
Running last winter's last few gal= lons of auto-gas from my storage tanks.

Engine was all warmed up fro= m three laps around the pattern shooting landings at Hillsboro.  I had= taxied back to the hanger to check for anything out of the ordinary since = I had recently been working on my carb.  Everything was okay so I head= ed back out.

While setting at an intersection for about 5 minutes waiting to be = cleared for takeoff my CHTs were heading for hotter than I like.  The = wind was at my tail so the engine was not getting any cooling.  CHT wa= s passing 335 on the Electronics International UBG-16 engine monitor and I = was about to call the tower and tell them I was heading back.  The con= troller beat me to it and cleared me for takeoff.  This airplane norma= lly runs about 325 at power and I have to have a hot day to get it to 350 b= ut I never see it that hot prior to takeoff.

Okay, I thought, a little air through the cowl and we'll be back to= normal.  So I answered the controller "6RV cleared for TO",= lined up and pushed in the throttle.  I got almost 2000 rpm and just = enough of a push to make it to the next intersection and coast off the runw= ay.  It was as if I had pulled the mixture.  The prop had stopped= before I stopped rolling, I was looking at everything thinking I had misse= d something like the fuel valve half cocked or left the mixture mostly out = (I taxi that way).  Feeling stupid I called the tower and said 6RV was= NOT taking off. =20

After pushing it across the runway threshold I turned the electric = pump on and it was obviously empty from the noise it was making.  I wa= s on the tank that was 95% full so I switched to the other tank and viola.&= nbsp; I recognized the sounds of the pump filling the apparently empty fuel= system and carb.  Hopped in and after about 6 blades it lit and ran f= ine.  I called the tower and taxied back to the hanger.  Thankful= this had not happened at about 800 feet leaving the 5 o'clock news empty h= anded.

Pulling the cowling, the carb and fuel pump were so hot you couldn'= t hold your hand on them.  The gas had boiled enough that it pushed it= back through the mechanical pump, gascolator, Facet pump, and tank selecto= r valve.  When I switched to the "cold" tank out on the inte= rsection the Facet could get hold of enough at that point to push fuel back= to the engine.  From this tank the fuel was cold enough I could get i= t started and taxi back to the hanger.

-->KEVIN:
I know you run 100LL but at the temps you are descr= ibing, upwards of 400 degrees, you can vapor lock 100LL, too.  I think= Dave's right, it could be that you are getting some vapor generation on th= e ground when you're trying to run at full power.  You mentioned the p= roblem only happens when the engine is warmed up.

I'm going to try and duplicate last Saturday's scenario this weeken= d (except the takeoff attempt) if the OAT is up enough.

Bear in mind= that since I have never had any problems like this I never saw any need fo= r blast tubes on the fuel pump and carb like some people have done.  T= he cowling on the RV is pretty tight and I have four exhaust pipes down the= re next to the carb, pump, and gascolator.  And since I have thousands= of hours running auto gas in various planes, while the extra volatility ce= rtainly contributed I don't believe it's bad stuff and will continue to use= it.  I may keep one tank with mostly 100LL in it for ground ops on th= e very hot days for extra margin but there were more things than fuel type = that contributed to what happened. =20

Obviously a fuel return line that would allow purging the hot fuel = would be another fix.  We have another RV-4 on the field that has a va= por bleed return line for just this reason.

Well, sorry for the epis= tle but I thought it was something for people to keep in mind while your wa= iting in a long taxi line at a busy airport.  Especially those of us w= ho rarely see 90 degree ramp temps.  It was a real eye opener (and I'v= e only got one eye..)   P-) =20

Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR
13B in gestatio= n mode, RD-1C, EC-2
 
Thanks for the report Mike.  That is one thing I really like abou= t our rotary set-up: high pressure/high flow fuel systems with a return lin= e.  The chance of vapor lock is essentially zero even with winter blen= d auto fuel at altitude on the hottest day of summer.  That and carb i= ce are two of the biggest issues that cause GA accidents - and we don'= t have to worry about them.  Loss of control on landing and plain old = running out of gas still top the list however.
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