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