REFLECTOR: Engine failure causes

Tue Apr 7 22:21:18 CDT 2009

Brian,

I just finish my emergency fuel shut off valve setup a few weeks ago, since your valve setup is in question, using a push pull cable I purchased from AS. It works great. I can open or close it very easily. The  first attached photo shows the valve installed before I got all the parts in to add the cable. The control cable has a red knob with a center locking push button. I am traveling for business and won't be home till after the 16th. I will post the last picture of the cable connection to the valve, when I get home if anyone is still interested. I haven't taken the photo yet. I hope the photo's aren't too large to make it on the reflector. They are as small as I could get them.

Andy Ellzey
XLRG 

----- Original Message ----
From: Brian Michalk <michalk at awpi.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Tuesday, April 7, 2009 10:41:36 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
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 100_4792-1.jpg
Type: image/pjpeg
Size: 68062 bytes
Desc: not available
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20090407/26aa920b/attachment-0002.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 100_6249-1.jpg
Type: image/pjpeg
Size: 75276 bytes
Desc: not available
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20090407/26aa920b/attachment-0003.bin>