Return-Path: Received: from [65.54.168.121] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.3c1) with ESMTP id 726545 for flyrotary@lancaironline.net; Sat, 12 Feb 2005 15:49:47 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.54.168.121; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Sat, 12 Feb 2005 12:49:01 -0800 Message-ID: Received: from 4.174.4.81 by BAY3-DAV17.phx.gbl with DAV; Sat, 12 Feb 2005 20:48:01 +0000 X-Originating-IP: [4.174.4.81] 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 Date: Sat, 12 Feb 2005 15:05:57 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00B3_01C51114.5B1DB9A0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.10.0009.2900 Seal-Send-Time: Sat, 12 Feb 2005 15:05:57 -0500 X-OriginalArrivalTime: 12 Feb 2005 20:49:01.0141 (UTC) FILETIME=[47E2A050:01C51144] This is a multi-part message in MIME format. ------=_NextPart_000_00B3_01C51114.5B1DB9A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable This thread just reinforces my dislike of sump tanks, vented or not. = Why complicate life like this? A return line to the tank is not that = hard to do and creates lots of possible problem scenarios. Tracy=20 I am a lot more skeptical about venting a sump tank. If the sump is = vented and for any reason the mains don't gravity feed just right (it = can and does happen - ask me how I know this :-) you can consume the = fuel in the sump faster than it is gravity feeding from the main tank. = If the sump is vented, you will run it dry with lots and lots of fuel in = the mains. If you close the sump vent OTOH the sump level CAN'T go = lower and the engine will "suck" fuel out of the mains to the sump (at = least until one main empties and provides the sump with a "vent path" - = you can ask me how I know this bit too :-). I used to have my sump vent = plumbed to the top of the cabin like Perry, and kept a dowel stuck in it = to close it because I didn't want the sump to be able to empty before = the mains. One time I was driving along and smelled something and my = wife looked over her shoulder and there was a fountain of fuel pouring = out of the sump vent that had blown the dowel out. She crawled into the = back seat and stopped the leak with her fingers while I landed. We = drained a couple of gallons of gas out of the bilges. =20 Now I have a schrader valve on my sump vent. I take it off to allow = the sump to fill all the way up and then cap it off again. I know I'll = NEVER fly with my sump vented, but like Perry I make sure the sump is = full on preflight and if it isn't, vent it until it's full (and then cap = it off). Sump must be full and unvented to fly right ... Jim S. Perry Mick wrote: One final thought.....my aluminum sump tank in not vented. Seems = we discussed this at length when I was building this thing, and since = the overflow is pumped into the sump tank, the fuel might just be pumped = right out of the vent. Take care. Paul Conner Paul, I think this is your problem. I brought this up on this list = once before. I nearly had the makings of a fatal accident a year ago = when I temporarily had my sump tank unvented. I had been flying for over = four years with a vented sump tank and never had a problem.=20 I flew to Puyallup WA for the airfaire early in the morning. The = plane sat out in the sun all day, with temperatures rising. When I went = out early afternoon to depart, I lifted the nose, hopped in, started the = engine, taxied to active runway. Very fortunately there were several = planes in the pattern and I had to wait for takeoff. Finally, I took the = active, pushed in full throttle - and the engine died. This had never = happened before. I got out and pushed it off the runway, somewhat = stumped. Finally I remembered the rubber cap I had put on the sump tank = vent. I popped it off and heard a "poof" sound, and then the sound of = fuel flowing into the sump tank. My sump tank is mounted low, fed from = the main tank by gravity. Apparently being parked nose down for several = hours out in the sun allowed vapor lock to form in the lines between the = main tank and the sump tank. If those planes had not been in the = pattern, I would have taken off from a relatively short field in a = congested area and the engine would have quit right after takeoff with = no place to land safely. My sump tank vent is up at the top of the fuselage with the main = tank vents, I never have problems with fuel being pumped out the vent. I = now maintain that the sump tank must be vented - to do anything else may = be fatal. I've brought this up before on this list and more recently on = Canard Aviators. Perry ------=_NextPart_000_00B3_01C51114.5B1DB9A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
This thread just reinforces my dislike of sump tanks, vented or = not. =20 Why complicate life like this?  A return line to the tank is not = that hard=20 to do and creates lots of possible problem scenarios.
 
Tracy
I=20 am a lot more skeptical about venting a sump tank.  If the sump = is vented=20 and for any reason the mains don't gravity feed just right (it can and = does=20 happen - ask me how I know this :-) you can consume the fuel in the = sump=20 faster than it is gravity feeding from the main tank.  If the = sump is=20 vented, you will run it dry with lots and lots of fuel in the = mains.  If=20 you close the sump vent OTOH the sump level CAN'T go lower and the = engine will=20 "suck" fuel out of the mains to the sump (at least until one main = empties and=20 provides the sump with a "vent path" - you can ask me how I know this = bit too=20 :-).  I used to have my sump vent plumbed to the top of the cabin = like=20 Perry, and kept a dowel stuck in it to close it because I didn't want = the sump=20 to be able to empty before the mains.  One time I was driving = along and=20 smelled something and my wife looked over her shoulder and there was a = fountain of fuel pouring out of the sump vent that had blown the dowel = out.  She crawled into the back seat and stopped the leak with = her=20 fingers while I landed.  We drained a couple of gallons of gas = out of the=20 bilges. 

Now I have a schrader valve on my sump = vent.  I=20 take it off to allow the sump to fill all the way up and then cap it = off=20 again.  I know I'll NEVER fly with my sump vented, but like Perry = I make=20 sure the sump is full on preflight and if it isn't, vent it until it's = full=20 (and then cap it off).

Sump must be full and unvented to fly = right ...=20 Jim S.

Perry Mick wrote:
  One final thought.....my aluminum sump tank = in not=20 vented. Seems we discussed this at length when I was building this = thing,=20 and since the overflow is pumped into the sump tank, the fuel might = just be=20 pumped right out of the vent. Take care. Paul Conner

Paul, I = think=20 this is your problem. I brought this up on this list once before. I = nearly=20 had the makings of a fatal accident a year ago when I temporarily = had my=20 sump tank unvented. I had been flying for over four years with a = vented sump=20 tank and never had a problem.
I flew to Puyallup WA for the = airfaire=20 early in the morning. The plane sat out in the sun all day, with=20 temperatures rising. When I went out early afternoon to depart, I = lifted the=20 nose, hopped in, started the engine, taxied to active runway. Very=20 fortunately there were several planes in the pattern and I had to = wait for=20 takeoff. Finally, I took the active, pushed in full throttle - and = the=20 engine died. This had never happened before. I got out and pushed it = off the=20 runway, somewhat stumped. Finally I remembered the rubber cap I had = put on=20 the sump tank vent. I popped it off and heard a "poof" sound, and = then the=20 sound of fuel flowing into the sump tank. My sump tank is mounted = low, fed=20 from the main tank by gravity. Apparently being parked nose down for = several=20 hours out in the sun allowed vapor lock to form in the lines between = the=20 main tank and the sump tank.  If those planes had not been in = the=20 pattern, I would have taken off from a relatively short field in a = congested=20 area and the engine would have quit right after takeoff with no = place to=20 land safely.

My sump tank vent is up at the top of the = fuselage with=20 the main tank vents, I never have problems with fuel being pumped = out the=20 vent. I now maintain that the sump tank must be vented - to do = anything else=20 may be fatal. I've brought this up before on this list and more = recently on=20 Canard=20 Aviators.

Perry

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