Ron Lee

Ron Lee

Well Known Member
Coming back from Seattle via Independence OR, I made a fuel stop in Wells Nevada (LWL). I made that choice mainly based upon price. The flight day started four hours later than desired due to a marine layer over Renton, WA (RNT).

I finally land in Wells around 430 PM so it was hot. Surprise. After fueling, using the facilities and looking for people I walk back to the plane and think that the conditions are ripe for vapor lock. What if I can't start the engine and I have to overnight here? Is there a hotel? How would I get there? This is a remote location.

The engine started on the third attempt and ran a bit rough for a while so vapor lock may have been a factor.

Based upon this event I plan on landing at larger airports while crossing remote regions. Saving a few dollars on gas would be chump change if a mechanical/engine issue developed.

Edit: Carbureted engine.
 
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Ron,

Or, you can learn how to start a hot engine, maybe install a purge valve to bring cool fuel to the engine and pump the hot vapor locked fuel back to your other tank.

Buying cheap fuel is good for the aviation economy, we need to promote the less greedy fuel suppliers!
 
Hate to be picky

But us engineering types can't help it.

A hot start problem is highly unlikely to be vapour lock!..VL describes localised boiling at it occurs at the inlet to the machanical fuel pump.

What you are describing is vapourisation in the injector lines. This causes the hot start issues.

As mentioned above a purge valve takes care of this issue completely.

As for me with no mechanical pumps I can burn highly volatile fuel (mogas with ethanol) on the hottest of days at high altitude and take off without a second thought to a real VL issue.

Frank
 
Purge valve location

Exactly where in the line would this valve go? Is this more or less just a by-pass to circulate fuel back to the tanks. And would that necessarily be a solenoid valve at the engine mounted fuel pump or a manual valve in the cockpit. Any links to a diagram of a system like this? Sounds like a good idea.
 
Hi Tom...

A purge valve is usually operated by pulling a cable. This reroutes the fuel back to a tank or the fuel selector, depending on how it is plumbed. You bring cooler fuel to the engine and the warm/hot fuel is gone.

The downside to having a purge valve is that if it is inadvertantly activated, your engine stops, since the fuel is now returned instead of going to the engine.

I bid on a -4 in that was totalled during the forced landing when this happened.

Regards,
 
Proper installations

When the parts are installed correctly with aircraft quality cables and components and approved methods for doing the install there?s no problem. If you pull the mixture control in flight the engine quits also.

Bottom line is, most all parts on an aircraft are critical to its safe and proper operation in flight. Pay attention to the details, instructions, and people with knowledge and experience based on facts. There?s lots of ?expert opinions? out there.

Just for the record, the purge return line can be teed into one of the fuel tank feed lines before the selector valve. You do not need a dedicated return line to the tank.


Don
 
Ron, what proceedure are you using for starting your hot engine? Maybe there is a better technique we can help you with. A carb engine should be pretty easy starting, even hot. That has been my experience anyway.
 
The original point

Hot start techniques notwithstanding, Ron's original point is worth considering...

What happens in a remote area or an airport with no one around if ANY problem arises that would prevent you from leaving or require serious maintenance? Even simple maintenance is difficult without tools and parts.

Are we more willing to ignore pre-flight no-go items if the alternative to going is sleeping on the ground in the Nevada desert? Bush pilots deal with this risk all the time.

If you plan to stop at remote locations - or even fly over them - be prepared, Boy Scout! Tools, maintenance know-how, survival kits, etc. are required equipment. Thanks for the reminder, Ron!
 
NYTOM said:
Exactly where in the line would this valve go? Is this more or less just a by-pass to circulate fuel back to the tanks. And would that necessarily be a solenoid valve at the engine mounted fuel pump or a manual valve in the cockpit. Any links to a diagram of a system like this? Sounds like a good idea.
Click to expand...

The purge valve allows one to send fresh fuel up to but not through the flow divider. The path the fuel takes is past the flow divider and back to a tank. This does make starting a hot engine easy but it does not prevent fuel from vaporizing after it passes the flow divider and is in the distribution (spider) lines. Fresh relatively cool fuel does lessen vaporization but not eliminate it completely. The valve is mechanical and attached to the inlet side of the flow divider on top of the engine.

I have found that opening the oil cooler door immediately after landing, say for a fuel stop, does cool the top of the engine quick. Even 30 minutes helps a lot. When the door is opened, much hot air can be felt moving out.

As Don at AFP reminded me on this issue, 100LL vaporizes at 130F. Fuel pressure up to and through the flow divider after the FM200 controller is under relatively low pressure, I believe 1-3 psi. If the lines are heat soaked and fuel is not moving much, some vaporization does occur. I have no problem getting the engine started, but keeping it running under these circumstances requires 1000-1200 rpm to provide enough fuel flow to prevent vaporization. Once up to take off power, vaporization after the flow divider is a non event. It does not happen. Fuel is moving and incoming fresh air across the area cools things down considerably. I never have a vaporization problem after landing even on the hottest days. The engine will idle very smoothly at 670 rpm for quite some time.

With regard to the engine driven pump inlet, the weakest link in the system with regard to vaporization, an electric pump providing fuel under pressure from aft of the firewall eliminates that threat completely. I run my electric pump constantly on hot days. It is no big deal, the pumps are designed for continuos operation. But it is a good idea to have pressure regulator by-pass fuel going back to a tank instead of running it in a loop. Fuel in the loop will warm up on a hot day due to internal electric pump temperatures. I use the same purge by-pass line back to a tank for this purpose. The purge by-pass line has a check valve to prevent fuel from flowing forward but it probably is not necessary.
 
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Larry, first attempt was normal. Start cranking the engine with mixture control normal and a short throttle pump. I may have tried the same method a second time. Then mixture full lean, partial throttle and crank while pushing in the mixture. That worked but it still ran rough a while.

Obviously re-education on hot starts may be productive but other mechanical problems (flat tire, etc) would also have been problematic. Personally, I would not make the same fuel stop decision under similar conditions.

On trips like this I carry a lot of stuff to deal with likely problems. I have spare tires, tubes, tools, hardware, etc. But I may not be able to change a tire without a jack or similar to raise the wheel. There are limits on what I can carry so I assume that a mechanic will be available to supply things I don't carry. No mechanic seemed to be around at this airport.
 
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Try KLOL for desolate

For years I have been stopping at KLOL in Lovelock Nevada for cheap fuel. That place kind of spooks me out, I feel like mutants are going to come out of the hills at any moment. :eek:
Some of the planes look abandoned, it makes you wonder if their owners were lured in by cheap fuel too...
LovelockNV.jpg

Here is a shot my son took.
Gas is $3.40...


Hans
 
High altitude

Wells is 5772' msl

Open oil door --- as suggested

When (hot) starting, don't pump throttle and no priming. 1/8 to 1/4 throttle.

Important! ***Because of airport altitude --- 5700+, start with full rich, but immediately pull mixture out a 1/2 to 3/4". Otherwise, it will run rough.***

If flooded, mixture full lean, throttle 1/2 & then push mixture in --- and throttle back --- as it catches.

When I land at high altitude airports such as this one, I'll never be full rich on landing.

Wells has a number of motels ---- 2 miles away.

Out here in the remote "wild west" ------------ lot's of airports are this way! :)

P.S. ---- If mag check shows fouled plugs from running too rich, then throttle up to 2000 rpm or so, and pull mixture until engine gets rough. Then mixture back to normal. This will clear the plugs.

L.Adamson --- RV6A 0360-carb
 
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Come on guys & gals, where is your sense of adventure? Where is the RV spirit? I LOVE landing at rural airports, I've spent many nights sleeping on a couch in a modest pilot lounge, eating dinner out of a vending machine cause the crew car is broke (or MIA), calling the local police to have them come and unlock the fuel pumps, etc. All good stuff and part of the romance of flying!

Story Time #1 One FBO I landed at used the honor system for fuel purchases. They had the cash box sitting on the counter with $200 cash in it so you could make change after refueling! I'm not kidding. To get into the office you used the CTAF code and got the keys to unlock the fuel pump. Needless to say I won't identify the airport here!...no offense.

Story time #2 I was flying into a good head wind coming back from SnF about 10 years ago. Getting low on fuel I diverted to the closest airport. It was deserted except for a phone number of the local police. I called them and they said there was no fuel at the airport, but I could call this local guy and he might help. He came right out with 5 gallons of fuel so I could make it to the next fuel stop. Turns out he was the local new paper reporter and I made the front page of the local paper! "Pilot Makes Precautionary Landing Due To Low Fuel". He did not even want $$ for the fuel!

This is the stuff memories are made of!
 
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Return to the tank!

I had my engine builder (Dachsel Flugmotoren GmbH, M?nich) install a return line on my Precision Fuel Injection (in the pressure port at the top of the servo), that goes back to the double stack Andair Fuel valve and back to the tank. Due to a very small restrictor, it returns about 6 lt. (2 Gal.)/hr. to the tank, during normal operation, making sure there is always enough fuel pressure remaining. In case of a hot start, it will only take a few seconds with the boost pump on, to clear out the hot fuel and vapors.

I am not flying yet, but I am very confident this is going to help out a lot with ?VL?-issues.

Regards, Tonny.
 
What if?

So what if Ron could not have got his engine started? Sort of sucks when your in the middle of nowhere and your ride won't run. Cranking for very long and the battery could run down and now your in a real pickle. I have to agree with Ron that a few bucks saved may not be worth it.

My really hot start procedures go like this. I use an electric fuel pressure gauge and it is wired to the master buss so when I power up the craft for starting the fuel pressure registers. If it's over 5 psi (upwards of 10 psi) after fueling I know pressure is building because of vaporizing fuel in the line/carburetor. Mixture goes to idle cut-off, throttle to 3/8" and boost pump OFF. I keep my hand on the mixture and not the throttle and start cranking the engine over. She usually fires after 3 or four revolutions of the prop and starts running. When the engine wants to die I push the mixture in to catch it. It starts running again but then wants to die because it's flooding so I keep it running until it smoothes out by using the mixture control only. Works every time. Using the mixture knob will also help on the long hot taxis when VP is trying to ruin your day. Keep in running with the mixture control, leaving the throttle alone. Watch the fuel pressure and it will tell you a lot. Once it drops to normal you can leave the mixture at a lean taxi setting and resume normal throttle control. Boost pump on at this point. It takes some practice but once learned the procedure works real well.

The theory is that the fuel is boiling in the lines and pump with nowhere for the fluid to go except past the needle/seat. The fuel could also be perkolating in the carb. This excess full dumps into the airbox and also evaporates creating a to-rich-mixture to run. A few turns of the blades clears out the rich mixture and there is plenty of fuel left bubbling out of the carb to keep it running once it starts with the mixture lean. It will start.
 
Interesting procedure Gary. I kept the engine start attempts short. If it did not start soon it was not going too with that throttle/mixture setting. A few more attempts and I probably would have stopped for a while to let things cool.

As it was, with a four hour delay in starting the day, I got to Page at sunset. A 30-60 minute delay would have meant staying there or another location if I got it started.

I never considered checking fuel pressure prior to starting the engine.
 
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