REFLECTOR: First taxi test, a bit too exciting

[Scott Derrick]

I was going to take some yesterday and thought, naw, nobody would be
interested.  I'll take some today or tomorrow.

I've checked the system, and no damage except for a scorched K&N filter,
I think its still usable until the new replacement gets here.  Lots of
smoke residue in the induction system.  Anybody think that may be a
problem?  I cleaned the inside of the air servo and the scoop, but not
further into the system.

Scott

Bachman, Jonathan wrote:
> Sorry for the excitement.  Glad you arrested the fire.  Do you have any
> pictures of your induction system?
>
> Jon Bachman
> N956DR Std RG
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Scott Derrick
> Sent: Sunday, September 13, 2009 9:36 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: REFLECTOR: First taxi test, a bit too exciting
>
> Got everything buttoned up today!  Well, everything thats needed to fly
> anyway.  All paper work is signed off also.
>
> Decided a taxi up to the wash stand for a badly needed airplane washing,
> was a great way to start taxi testing.  This would be the 4th time I
> have run the engine cowled up with the ram scoop on. If the taxi back
> and forth was fine I was going to do a few mid speed taxi's down the
> runway.
>
> Started fine, let her run for a couple minutes and then time for big
> wind! I can't believe I've already forgotten how to taxi a Velocity? 
> Just getting it going straight was more than frustrating!  After weaving
> to and fro I finally remembered  the gentle taps and made my way to the
> other side of the ramp in a semi stabilized manner.  Pulled up to the
> hose rack and shut down.
>
> Washing went as predicted, shammied her off and man did she look good! 
> An airplane again!  Finally!
>
> Got back in and did my normal hot start procedure, but all I got was a
> short stutter and a  muffled back fire.  Tried  a flooded start, no
> joy.  Tried a normal start,  another stutter and died.  This was weird! 
> It had never done this before.  I tried another hot start, nada.. 
>
> Hmmm....  Got out and looked and saw what looked like mist in front of
> the induction scoop?   What the heck is that.  Got down and smelled, and
> it smelled like smoke!!  felt the scoop and it has hot hot hot!  DAMN,
> induction fire!!! And going on as I sat there! 
>
> I ran back to the cockpit door, full throttle, idle cut off and held the
> starter switch on for 30 seconds, seemed like minutes! 
>
> Crawled back under the cowling with my flight bag fire extinguisher in
> my hand, no smoke now in the scoop, and the scoop was cooler though
> still really hot!  Looked into the engine cowling next to the prop and
> saw no flames or light of any kind in the area of the induction system. 
>
> Grabbed my screwdriver and tried to quickly take the back side of the
> scoop(its in two pieces)  off. Finally got it off and  everything in
> side the scoop was covered with black soot!  The back side of the filter
> was browned and the rubber was melted.  Black soot going up into the air
> servo...
>
> Man, I almost burned up my airplane with an induction fire!  And I was
> probably throwing on more and more fuel with every start I attempted!
>
> After thinking things over there are two problems I built into the  new
> cowl/scoop. 
>
> 1.) no drain hole in the scoop for excess fuel.  The scoop is so tight
> it just pools up in the scoop next to the filter if i get too much fuel
> when priming.  Gonna have to have to drill a couple bleed holes for
> that. It will suck  a minuscule amount air through the holes at slow
> speeds. The scoop is pressurized at cruise speeds though.
>
> 2.) The air servo inlet is about an inch below the level of the lower
> cowling.  I had to make a small box like structure in the lower cowl
> that protrudes an inch below the cowl that the servo inlet bolts to. 
> The scoop then fits over this box on the outside of the cowl. When
> washing the airplane(or flying through rain for that matter) the water
> that entered the upper NACA's dripped through the engine and found the
> low spot, the servo box at the lowest level.  This channeled some/most?
> of water into the induction scoop which pooled inside already for that
> first start to suck some of it into the engine for my first aborted
> start attempt.  I need to make a  small  1/4 inch  raised lip  around
> the  box inside the  cowl  with  drain holes  so most of the water can 
> drain  out of the  cowl without  flowing into  induction scoop.  The
> small drain hole in the scoop mentioned above can allow any water that
> makes it into the scoop to drain away.
>
> Well, I guess thats why we call them experimentals.
>
> Scott
>
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