flyrotary@lancaironline.net Mailing List Archive

Completely agree with your points, Al. Particularly about paying attention to keeping water out of the fuel system. I mean water injection may work for jet aircraft and some turbo arrangements but not desirable (at least in uncontrolled quantities) in N/A engine.

I think the cold start and secondary effects were one and the same. The cold start is grounded (and therefore ON) anytime the injector disable switches switch off an injector pair. So turning on the cold start or turning OFF the secondary were both turning on the cold start function. It appears when you are on the ragged edge of the lean curve (due to water displacing fuel) the additional volume of liquid provided by cold start apparently provided sufficient fuel to keep it running.

I was also wondering whether the specific gravity of each liquid could be a factor. Would the fuel turn the curve from main injector rail into the injector easier than molecules of water? Or would it have any effect at all.

As I always say “You Live and Learn - provided you live”.

Appreciate all the inputs and “helpful” comments from everyone responding {:>)

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

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen
Sent: Monday, October 20, 2008 2:03 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Water in Fuel?? (or another adventure in the aviation events of Ed Anderson)

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!