REFLECTOR: Engine failure causes

Lou Stedman stedmanlou at roadrunner.com
Tue Apr 7 15:23:44 CDT 2009


I have my shutoff valve in the hose line coming out of the sump tank, there 
is a metal arm attached to the valve approximately1.5 inches long which my 
cable attaches to. The cable runs up along the pilot side and my push pull 
lever is just below the throttle quadrant. It works fine in both positions 
without any binding.

Lou Stedman
Velocity N7044Q
Olean, NY
----- Original Message ----- 
From: "Brian Michalk" <michalk at awpi.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Tuesday, April 07, 2009 11:41 AM
Subject: Re: REFLECTOR: Engine failure causes


>I am pretty sure it's not an ignition problem, because I have one magneto.
> To answer a previous post, my runup test showed less than 50 RPM drop
> with mag off, and about 200 RPM drop with electronic off.
> I was also able to briefly regain some power when I pulled back on the
> throttle, suggesting a lean condition.
>
> I've heard several people talking about the remote shutoff valves being
> difficult to set to the open position with a cable attachment.  Is this
> because the torque is too high causing the cable core to bend?
>
> David Bertram wrote:
>> The fuel shutoff sounds suspicious.  I ran a cable from the pilots
>> side by the seat back to the outlet of the sump tank.  I can shut the
>> fuel off but it does not open very well, but this is only used in
>> emergency or maintenance.  I also looked at foaming but found it as
>> unlikely due to the sump fuel outlet being at the bottom of the tank
>> and I have a good vent system.  When I had my engine fail everything
>> and "everyone" thought it was a fuel problem.  It was a ignition
>> failure caused by my distributor gear.
>> Dave Bertram
>> N350TX
>> /-------Original Message-------/
>>
>> /*From:*/ Brian Michalk <mailto:michalk at awpi.com>
>> /*Date:*/ 4/6/2009 11:15:11 AM
>> /*To:*/ Velocity Aircraft Owners and Builders list
>> <mailto:reflector at tvbf.org>
>> /*Subject:*/ REFLECTOR: Engine failure causes
>>
>> I've been going through the possible theories as to why my engine
>> failure occurred.  I didn't want to post rampant speculation, but a
>> week has passed, and I need to bounce some ideas off the collective.
>>
>> I am looking at fuel starvation as the reason for engine  failure.  I
>> have other ideas that excessively rich mixture might be a culprit, and
>> a few other oddball ideas, which I will explore as well.
>>
>> Prime suspect #1: Fuel starvation due to fuel shutoff valve arrangement.
>> I placed a shutoff valve in the keel at the copilot's knee position.
>> This is fed from the sump tank, and returns to an electric pump
>> between the firewall and gear bulkhead (fixed gear).  I still need to
>> inspect the hose for evidence of kinking.  The fuel return hose from
>> the pressure regulator did not have fuel in it during post crash
>> inspection.  My theory is that my aggressive climb at 90 kts resulted
>> in the shutoff valve being higher than the level of fuel in the
>> strakes.  This could be a combination problem coupled to other
>> theories I have.  A vapor bubble might have gotten to the fuel pump,
>> and caused it to lose prime, and then cavitate when I lowered the nose.
>>
>> Theory #2: Foaming fuel in sump tank
>> The theory here is that never before had I run fuel flows as high as
>> during the first flight.  The electric pump, plus the mechanical pump
>> at the redline RPM caused a large volume of fuel to be bypassed back
>> to the sump tank.  I built the tank before I planned on fuel
>> injection, and added a port for fuel return very close to fuel inlet
>> ports.  I need to go back and take sump pictures to see the
>> arrangement of the connectors, and also base that in the context of
>> high flows and takeoff angle.  It might be possible, but unlikely that
>> the sump tank became full of foaming gasoline.  diesel is much worse,
>> and avgas not so much, but it is a possibility.  I need to see if
>> foaming fuel could have been injested into the intake port and caused
>> "prime suspect #1" to happen.
>>
>> Unlikely theory #3: Debris in the tanks clogging filters
>> I pulled the filters and inspected several weeks before flight.  They
>> were clean, and this is the first time since building the plane and
>> doing all taxi testing and ground runs that I had inspected the
>> filters.  The tanks were found to be very clean after the building
>> process.
>>
>> More unlikely theory #4: Water in fuel
>> Even though I did not check the sump before first flight, the tanks
>> with caps on are very tight, and the plane kept in a hangar.  Again,
>> the high angle from takeoff might have injested the water.  There
>> should be evidence of water in the main tanks if this theory is
>> correct.  The dry fuel return hose begins to rule this scenario out as
>> a candidate.
>>
>> More unlikely theory #5: excessive vacuum on vent line
>> It might be possible that the vent line exiting the plane is in a high
>> vacuum area.  I'll try to simulate with a leaf blower.
>>
>> Discarded theories:
>> Clogged vent line
>>
>> If anyone else has any theories, throw them out and I will entertain
>> them.  Please see my fuel diagram.
>> //
>>
>>
>>
>>
>>
>>
>> FREE Animations for your email - by IncrediMail! Click Here!
>> <http://www.incredimail.com/index.asp?id=109095&rui=106124652>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> To change your email address, visit 
>> http://www.tvbf.org/mailman/listinfo/reflector
>>
>> Visit the gallery!  www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>
> _______________________________________________
> To change your email address, visit 
> http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html


--------------------------------------------------------------------------------



No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.0.238 / Virus Database: 270.11.45/2045 - Release Date: 04/07/09 
06:41:00



More information about the Reflector mailing list