Yeah; what Lynn said regarding the
cold start switch. What is the plumbing arrangement of primary and secondary
rail to pressure regulator? That may help explain the effect of turning off the
secondary injectors.
Always good to check the condition of
tank cap seals, and occasionally add a bit of fuel-proof o-ring grease. And;
well, of course – check the damn sump drain! J
Al G
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Monday, October 20, 2008
6:31 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Water in Fuel??
(or another adventure in the aviation events of Ed Anderson)
I always like to share happy little
“incidents” with others on the list in hopes we all might benefit
– not just me {:>). I landed at Shady Bend none-stop from NC
with the left tank empty and 14.7 gallons in the right tank.
On the way returning from the Rotary
Round up at Shady bend; I stopped to refuel at WayCross, GA as I normally
do. Everything thing has been work outstandingly on the trip thus far.
I took off and got up to my intended
cruise of 5500 MSL (30 kt headwind there, but bumpy as heck any lower).
With such a headwind, I knew the flight would be uneventful (the
incidents happen when I have a tail wind). After about 30
minutes I decided to switch from my right wing tank to my left. So I
turned on the boost pump and both high pressure pumps and turned the fuel
selector switch to the left tank.
Normally there is a non-event, there
is no hiccup or hesitation – normally! Well this time things
were different, the engine started to surge - big time – as did my
heart. The fuel pressure is wiggling a small amount but clearly with
pressure above 35 psi it is adequate.
My mind races back to that
incident a long time ago where I glided 12 miles engine out – and I
decided there was no benefit to be gained by repeating that experience.
So as I rapidly raced cause and solution hypothesis through my head, I reached
over and turned on the cold start switch. The engine began to run almost
normally, I switched cold start off and the surge returned. I hit
“nearest” on my Garmin and turned toward the nearest airport (17
miles). Then back to the engine. It is still surging although not
quite as badly as it had been – but still way too much to be comfortable
with – and that fuel pressure is still nominally around 40 psi.
What goes?
I then turned off my secondary
injectors - the engine began to run smoothly (although I don’t know if
this was more than a coincident of timing). So recalling my lesson
learned from that earlier incident (switch tanks, dummy!), I switched back to
the right tank – happily every thing settled down (including my heart)
and the engine ran normally.
After getting a bit closer to the
target airport, I gathered my nerves (what remained of them) and switched back
to the left tank – there was a momentary burble, but then the engine
started running normally and did so for the rest of the flight burning 10
gallons out of that tank.
Naturally, I am trying to figure out
what could possibility have cause this momentary hiccup. Here is the best
I can come up with.
I landed at Shady bend with the left
tank with approx ¾ gallon in it. It so happens the gas cap on that tank
is in need of an O ring replacement as I noticed a small amount of fuel
streaming from the cap area. Well, the aircraft set outside through a few
light rain showers while at Shady Bend. I believe that water may have
seeped through the cap and collected in the tank. (No, I did not do a
drain of my tanks checking for water as I should have). I used to do it
religiously, but after 8 years of so of never finding a single drop of water, I
had lapsed in that check. No excuses – just the facts.
So if a ½ cup or water or so had
gotten into that empty tank, it would naturally have settled at the bottom
– right next to the fuel pick up. I refueled at WayCross putting
fuel into both tanks – no problem with the right tank (with a non-leaking
cap). So I believe that I took off with some amount of water in the left
tank. When I switched fuel tanks that slug of water was sitting right
there waiting to be sucked into the system. This is why (I believe) the
fuel pressure did not go down as it would have if there had been no liquid
being pumped through the system. So it basically took a few hair
raising moments to suck all the water through the system and into the engine
– then all was well.
I am not certain why hitting the
“cold Start” switch would have made any difference, but I did turn
it on twice and each time the engine settled down. Also when the
secondary injectors were momentarily turned off the engine smoothed out.
It may have to do with injecting water into the secondaries (which are
positioned further away from the engine) and perhaps the evaporative effect was
sufficient to freeze the water vapor??? Don’t know, but I am
convinced that water in the fuel was the most likely cause.
I think the principal point is that
had I done the fuel drain according to Hoyle I would have likely discovered the
water and drained it. So once again, a bit red-faced to admit to failing
to follow long established check-list procedures (I know none of the rest of
you do that), I found an interesting “incident” to relate to the
list.
Fly Safely out there –
Ya’ hear!
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda/index.html