X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [64.4.51.83] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.3.7) with ESMTP id 640159 for flyrotary@lancaironline.net; Sun, 07 Aug 2005 11:38:46 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.4.51.83; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Sun, 7 Aug 2005 08:38:02 -0700 Message-ID: Received: from 64.4.51.220 by BAY107-DAV11.phx.gbl with DAV; Sun, 07 Aug 2005 15:38:01 +0000 X-Originating-IP: [64.4.51.220] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Vapor lock last weekend Date: Sun, 7 Aug 2005 11:37:54 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_01A1_01C59B44.736AFD00" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.10.0011.1703 Seal-Send-Time: Sun, 7 Aug 2005 11:37:54 -0400 X-OriginalArrivalTime: 07 Aug 2005 15:38:02.0177 (UTC) FILETIME=[FEFAAB10:01C59B65] This is a multi-part message in MIME format. ------=_NextPart_000_01A1_01C59B44.736AFD00 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Those IR temp sensors are a great idea and very useful for this type of = testing and for calibrating the EM2 if need be. Al G. tipped me off on = one thing about them however. If the object being measured is shiny, = aluminum, painted white, etc, you can get a false reading (lower than = actual). Put a small spot of flat black paint on whatever you want to = measure and they are spot on accurate. The red paint on my engine = housings works well too. Tracy ----- Original Message -----=20 From: al p wick=20 To: Rotary motors in aircraft=20 Sent: Sunday, August 07, 2005 11:04 AM Subject: [FlyRotary] Re: Vapor lock last weekend Thanks so much for sharing your experience. You've described the = conditions well.=20 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. =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 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. = =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 = 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-) =20 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: =20 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. =20 =20 Doubtful, but a bad could maybe act that 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=20 ------=_NextPart_000_01A1_01C59B44.736AFD00 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Those IR temp sensors are a great idea and very useful for this = type of=20 testing and for calibrating the EM2 if need be.  Al G. tipped me = off on one=20 thing about them however.  If the object being measured is shiny, = aluminum,=20 painted white, etc, you can get a false reading (lower than = actual). =20 Put a small spot of flat black paint on whatever you want to = measure and=20 they are spot on accurate.  The red paint on my engine housings = works well=20 too.
 
Tracy
----- Original Message -----
From: al p wick
To: Rotary motors in = aircraft
Sent: Sunday, August 07, 2005 = 11:04=20 AM
Subject: [FlyRotary] Re: Vapor = lock last=20 weekend

Thanks so much for sharing your experience. You've described the=20 conditions 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=20 it is. They are pretty accurate, great way to gather facts. We know = that fuel=20 pump temp is highly significant cause for vapor lock, so great value = in=20 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=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.=20 By gathering the facts we can get closer to measuring our vapor lock = safety=20 margin. 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,=20 Oregon
Prop 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>=20 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 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=20 check for anything out of the ordinary since I had recently been = working on=20 my carb.  Everything was okay so I headed back = out.

While=20 setting at an intersection for about 5 minutes waiting to be cleared = for=20 takeoff my CHTs were heading for hotter than I like.  The wind = was at=20 my tail so the engine was not getting any cooling.  CHT was = passing 335=20 on the Electronics International UBG-16 engine monitor and I was = about to=20 call the tower and tell them I was heading back.  The = controller beat=20 me to it and cleared me for takeoff.  This airplane normally = runs about=20 325 at power and I have to have a hot day to get it to 350 but I = never see=20 it that hot prior to takeoff.

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

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

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

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

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

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

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

Well,=20 sorry for the epistle but I thought it was something for people to = keep in=20 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=20 real eye opener (and I've only got one eye..)   P-) =20

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


At 20:50 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=20 those suggestions doesn't fix it, then = consider:
 
Since you=20 have definitely identified temperature as a culprit, that points = at 2=20 possible causes: fuel vaporization and detonation.  Vaporized = fuel=20 going to the carb could cause a scenario where the bowl cant = fill. =20 Also, detonation could behave like what you describe.  Maybe = you=20 cooling flow is no sufficient. 
 
Doubtful, but a = bad=20 could maybe act that way.  It's easy enough to test that as a = possibility.

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

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