X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from m12.lax.untd.com ([64.136.30.75] verified) by logan.com (CommuniGate Pro SMTP 4.3.7) with SMTP id 640123 for flyrotary@lancaironline.net; Sun, 07 Aug 2005 11:06:50 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.136.30.75; envelope-from=alwick@juno.com Received: from m12.lax.untd.com (localhost [127.0.0.1]) by m12.lax.untd.com with SMTP id AABBRNJ42AVB5NGA for (sender ); Sun, 7 Aug 2005 08:06:00 -0700 (PDT) X-UNTD-OriginStamp: L941HVjjYzDhN3itp//mkEPNtw7JyWMyWvSgSdnplFbObZO4a6nr2g== Received: (from alwick@juno.com) by m12.lax.untd.com (jqueuemail) id KZTEM3CY; Sun, 07 Aug 2005 08:05:13 PDT To: flyrotary@lancaironline.net Date: Sun, 7 Aug 2005 08:04:47 -0700 Subject: Re: [FlyRotary] Vapor lock last weekend Message-ID: <20050807.080457.3852.8.alwick@juno.com> X-Mailer: Juno 5.0.33 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary=--__JNP_000_04b9.62a7.08c7 X-Juno-Line-Breaks: 8-6,8-9,15-16,21-22,24-33,35,38-39,42-45,47-49,53-54,62-63,72-73,80-81,88-90,95-96,98-99,108-109,112-113,117-124,127-128,133-134,136-141,142-32767 From: al p wick X-ContentStamp: 40:20:3129925720 X-MAIL-INFO:42f0f069bd046149750c81690d81b1f40129608151554165bd51602951ed5174e55480adf0a0695969e0bde9b1b025e94904305414993499d584c5d56d447df48455cd0031ed39208db024fd8d1d91e43950f905392434797029f43484a184fdb9845564d06490616925690c4d300c0040a9814d20f5cd801901e451d9bdb451e974890171153d256124254945f02515f92100692d9599818da9a90959010ded95c14579359170292454b5312424a499c93ddda4 X-UNTD-Peer-Info: 127.0.0.1|localhost|m12.lax.untd.com|alwick@juno.com This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ----__JNP_000_04b9.62a7.08c7 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Thanks so much for sharing your experience. You've described the conditions well. Couple comments if I may. Head on down to local hobby shop. Purchase one of those little $25 infra red temperature sensors. You just point it at object and it tells you how hot it is. They are pretty accurate, great way to gather facts. We know that fuel pump temp is highly significant cause for vapor lock, so great value in finding it's temp. Use hair dryer on it to measure your safety margin. Assume you crashed, assume you have misidentified the cause(s). Seek ways to prove your causes. A fundamental problem with vapor lock risk is we never know how close we are to that condition, so we tend to make assumptions. By gathering the facts we can get closer to measuring our vapor lock safety margin. It is measurable. I strongly suspect the fuel pressure bypass idea would have no positive effect on your vapor lock risk. -al wick Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5 N9032U 200+ hours on engine/airframe from Portland, Oregon Prop construct, Subaru install, Risk assessment, Glass panel design info: http://www.maddyhome.com/canardpages/pages/alwick/index.html On Thu, 04 Aug 2005 22:08:00 -0700 Michael McGee writes: Thought I would share this with everyone since just about everyone is getting some of this heat wave and most of us aren't used to it. Also, it sounds very similar to what Kevin is putting up with in his RV-6A. Interesting experience this last Saturday in my RV-4. Interesting 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 gallons of auto-gas from my storage tanks. Engine was all warmed up from 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 headed 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 was 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 controller beat me to it and cleared me for takeoff. This airplane normally runs about 325 at power and I have to have a hot day to get it to 350 but 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 runway. 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 missed 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. 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 was on the tank that was 95% full so I switched to the other tank and viola. 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 fine. 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 handed. 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 selector valve. When I switched to the "cold" tank out on the intersection 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 it started and taxi back to the hanger. -->KEVIN: I know you run 100LL but at the temps you are describing, 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 the ground when you're trying to run at full power. You mentioned the problem only happens when the engine is warmed up. I'm going to try and duplicate last Saturday's scenario this weekend (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 for blast tubes on the fuel pump and carb like some people have done. The cowling on the RV is pretty tight and I have four exhaust pipes down there next to the carb, pump, and gascolator. And since I have thousands of hours running auto gas in various planes, while the extra volatility certainly 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 the very hot days for extra margin but there were more things than fuel type that contributed to what happened. 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 vapor bleed return line for just this reason. Well, sorry for the epistle but I thought it was something for people to keep in mind while your waiting in a long taxi line at a busy airport. Especially those of us who rarely see 90 degree ramp temps. It was a real eye opener (and I've only got one eye..) P-) Mike McGee, RV-4 N996RV, O320-E2G, Hillsboro, OR 13B in gestation mode, RD-1C, EC-2 At 20:50 2005-08-03, you wrote: Kevin, I agree with Ken Powell that it still sounds mostly like fuel starvation, probably in the carb. So I won't beat that horse... However, if following those suggestions doesn't fix it, then consider: Since you have definitely identified temperature as a culprit, that points at 2 possible causes: fuel vaporization and detonation. Vaporized fuel going to the carb could cause a scenario where the bowl cant fill. Also, detonation could behave like what you describe. Maybe you cooling flow is no sufficient. Doubtful, but a bad could maybe act that way. It's easy enough to test that as a possibility. -- Dave Leonard Turbo Rotary RV-6 N4VY http://members.aol.com/_ht_a/rotaryroster/index.html http://members.aol.com/vp4skydoc/index.html ----__JNP_000_04b9.62a7.08c7 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: quoted-printable
Thanks so much for sharing your experience. You've described the = conditions=20 well.
Couple comments if I may.
Head on down to local hobby shop. Purchase one of those little $25 = infra=20 red temperature sensors. You just point it at object and it tells you how = hot it=20 is. They are pretty accurate, great way to gather facts. We know that fuel = pump=20 temp is highly significant cause for vapor lock, so great value in finding = it's=20 temp. Use hair dryer on it to measure your safety margin.
 
Assume you crashed, assume you have misidentified the cause(s). Seek = ways=20 to prove your causes. A fundamental problem with vapor lock risk is we = never=20 know how close we are to that condition, so we tend to make = assumptions. By=20 gathering the facts we can get closer to measuring our vapor lock safety = margin.=20 It is measurable.
 
I strongly suspect the fuel pressure bypass idea would have no = positive=20 effect on your vapor lock risk.
 
-al wick
Artificial intelligence in cockpit, Cozy IV powered by = stock=20 Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, OregonProp=20 construct, Subaru install, Risk assessment, Glass panel design=20 info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
 
 
On Thu, 04 Aug 2005 22:08:00 -0700 Michael McGee <jmpcrftr@teleport.com> writes:=
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,=20 it sounds very similar to what Kevin is putting up with in his=20 RV-6A.

Interesting experience this last Saturday in my RV-4. = =20 Interesting because it didn't happen at 800 feet where it would have = probably=20 made the news but while I was just starting my takeoff=20 roll.

Conditions:
90 deg F, about noon on Saturday
150 HP = Lyc=20 O-320 with carb, gascolator, mechanical and Facet electric pumps.
= Running=20 last winter's last few gallons of auto-gas from my storage=20 tanks.

Engine was all warmed up from three laps around the pattern= =20 shooting landings at Hillsboro.  I had taxied back to the hanger to = check=20 for anything out of the ordinary since I had recently been working on my= =20 carb.  Everything was okay so I headed back out.

While = setting at=20 an intersection for about 5 minutes waiting to be cleared for takeoff my = CHTs=20 were heading for hotter than I like.  The wind was at my tail so the= =20 engine was not getting any cooling.  CHT was passing 335 on the=20 Electronics International UBG-16 engine monitor and I was about to call = the=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=20 and I have to have a hot day to get it to 350 but I never see it that hot= =20 prior to takeoff.

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

After pushing it across the runway = threshold=20 I turned the electric pump on and it was obviously empty from the noise = it was=20 making.  I was on the tank that was 95% full so I switched to the = other=20 tank and viola.  I recognized the sounds of the pump filling the=20 apparently empty fuel system and carb.  Hopped in and after about 6= =20 blades it lit and ran fine.  I called the tower and taxied back to = the=20 hanger.  Thankful this had not happened at about 800 feet leaving = the 5=20 o'clock news empty handed.

Pulling the cowling, the carb and fuel = pump=20 were so hot you couldn't hold your hand on them.  The gas had boiled= =20 enough that it pushed it back through the mechanical pump, gascolator, = Facet=20 pump, and tank selector valve.  When I switched to the "cold" tank = out on=20 the intersection the Facet could get hold of enough at that point to push= fuel=20 back to the engine.  From this tank the fuel was cold enough I could= get=20 it started and taxi back to the hanger.

-->KEVIN:
I know you= run=20 100LL but at the temps you are describing, upwards of 400 degrees, you = can=20 vapor lock 100LL, too.  I think Dave's right, it could be that you = are=20 getting some vapor generation on the ground when you're trying to run at = full=20 power.  You mentioned the problem only happens when the engine is = warmed=20 up.

I'm going to try and duplicate last Saturday's scenario this=20 weekend (except the takeoff attempt) if the OAT is up enough.

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

Obviously a fuel return line = that=20 would allow purging the hot fuel would be another fix.  We have = another=20 RV-4 on the field that has a vapor bleed return line for just this=20 reason.

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

Mike McGee, RV-4 N996RV, O320-E2G,=20 Hillsboro, OR
13B in gestation mode, RD-1C, EC-2


At 20:50=20 2005-08-03, you wrote:
Kevin, I agree with Ken = Powell=20 that it still sounds mostly like fuel starvation, probably in the=20 carb.  So I won't beat that horse...  However, if following = those=20 suggestions doesn't fix it, then consider:
 
Since you have= =20 definitely identified temperature as a culprit, that points at 2 = possible=20 causes: fuel vaporization and detonation.  Vaporized fuel going to= the=20 carb could cause a scenario where the bowl cant fill.  Also, = detonation=20 could behave like what you describe.  Maybe you cooling flow is no= =20 sufficient. 
 
Doubtful, but a bad could maybe act = that=20 way.  It's easy enough to test that as a possibility.

--=20
Dave Leonard
Turbo Rotary RV-6 N4VY
http://= members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/vp4skydoc/index.html
 

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