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Notorious Lycoming Hot Start

togaflyer

Well Known Member
So I was looking at a solar powered fan for camping. And I thought, just what if.
What if after landing this was rigged to blow fresh air into the cowling through the oil door on top of the cowling. Land open the oil door, fan goes on with suction cups, starts blowing cooler air down to the top of the engine.

Is this a concept or just an attempt to avoid the unavoidable.
 
I think you'd want the fan to suck air out, not blow air in. With that said, I do typically open my oil door to let the heat out. It's hot where I live and I try to avoid vapor lock. Luckily haven't had any issues yet.
 
Ive been flying out of the pit of h€ll for 25 years now - almost exclusively with Bendix FI. I can probably count on one hand the times I could not get it to start on the first try. Just last weekend I landed for gas at MHV and there was a Slingsby sitting in the pit, grinding away at the starter trying to get the fire lit. (This is the same model (T-3 Firefly) that the Air Force cut up and scrapped because of starting and engine stoppage issues.) After several attempts, he gave up and pushed out of the way so I could fuel. I watched many more unsucessful attempts to start as I fueled the Rocket, and by the time I hung up the hose and ground clamp, he was on the phone begging for help. I walked over and asked what his POH hot start technique was (I already knew it was to flood the engine and pray, because I could see the fuel vapors pouring out of the pipes as he was cranking), he confirmed my suspicion and I offered my standard hot start technique - essentially the "clear engine" procedure.

I told him:

No boost
Idle cutoff
Crank
Advance throttle slowly
As it comes alive, bring in mixture and retard throttle.

He was skeptical and had been flying the airplane for a long time, but when it fired almost immediately and I got the thumbs up I knew I made a believer.

Bottom line is that a quick turn hotstart should always be treated as a flooded engine, because thats what it is. Perform the clear engine proceedure and it will fire 99.9% of the time on the first try. If not, the fuel is "cleared", and you can try the more typical cool start where you add fuel to prime.
 
Lycoming’s hot start procedure

Here’s Lycoming’s unofficial hot start procedure. Works great for me. Watch your fuel pressure drop during step 5.
9060DDDF-2BD3-4DC5-9604-4F271F78D7D0.jpg
 
For hot starts on an IO-320, I have really good luck with a 1-sec. prime with mixture set at full rich, just to get any vaporization bubbles out of the lines. Then ICO and throttle cracked; smoothly push mixture in when she fires.

For the typical 10-minute refueling hot start, same procedure except no boost pump at all.

I had an induction leak a while back (crusty rubber couplers) and hot starts were far easier after this was fixed!!
 
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Re the Lycoming unofficial procedure:

What does the brief rich mixture setting (step 5) with the boost off and the engine not being cranked accomplish?

Just to add fuel to the discussion, my engine builder taught me to hot start by setting throttle full open, mixture at ICO, advance mixture while cranking and pull throttle back as soon as it catches. It's a finessed hand-twisting move with the throttle lever going backward by thumb pressure while my fingers slide the mixture level forward - and no, it doesn't always work, but mostly it does. I always have the boost on for this, and should try it sometime with boost off.

ETA: I paid Ross Farnham dearly for his countermeasures to assure I'm never plagued with induction leaks in my lifetime. Recommended.
 
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Re the Lycoming unofficial procedure:

What does the brief rich mixture setting (step 5) with the boost off and the engine not being cranked accomplish?

Just to add fuel to the discussion, my engine builder taught me to hot start by setting throttle full open, mixture at ICO, advance mixture while cranking and pull throttle back as soon as it catches. It's a finessed hand-twisting move with the throttle lever going backward by thumb pressure while my fingers slide the mixture level forward - and no, it doesn't always work, but mostly it does. I always have the boost on for this, and should try it sometime with boost off.

ETA: I paid Ross Farnham dearly for his countermeasures to assure I'm never plagued with induction leaks in my lifetime. Recommended.

If it's on a FI engine, my guess is that it could be relieving vapor pressure between the mechanical pump and the servo. I'm not sure why someone would want to do this unless it helps prevent the the occasional "stumble-quit" when the mixture is advance from ICO after the engine fires...

Skylor
 
Re the Lycoming unofficial procedure:

What does the brief rich mixture setting (step 5) with the boost off and the engine not being cranked accomplish?

On my engine (IO-540), fuel pressure drops toward zero when slowly moving mixture to full rich and back to ICO prior to cranking. Not trying to change minds. Just sharing that Lycoming’s hot start procedure has worked extremely well for me.
 
So I was looking at a solar powered fan for camping. And I thought, just what if.
What if after landing this was rigged to blow fresh air into the cowling through the oil door on top of the cowling. Land open the oil door, fan goes on with suction cups, starts blowing cooler air down to the top of the engine.

Is this a concept or just an attempt to avoid the unavoidable.

a minute or two after shutdown, the fuel in the spider lines boils and dumps the fuel in the cylinders; This is why it needs a special procedure. Quite unikely you can get a large enough fan in there quick enough to prevent this. I get out of the plane after shut down and can already hear the fuel boiling and spitting out the injectors.
 
understand how to start an aircraft piston engine

All due respect Mickey, but u probably mean injected aircraft piston engine, wild guess, still well below 1/2 of the aircraft piston engine population ;)
 
Fortunately never been stranded. It’s an IO 540. I try the basics and get the start, then a few seconds later the stall. Usually the third attempt is dump fuel then flood start it, which gets me over the hump. It’s that typical 15 minutes sitting while fueling got ya. I had better starts when I had the Earth X. Definitely moved the prop quicker. Got scared away from EarthX after an issue and had to default to an odyssey 925 to get home. Prop definitely swings slower with the standard battery. The fan was just a bubble idea.

Oh and thanks for the post on Dan H. Posting. I went over Dan’s start up recommendation. Makes sense. I will try that out.
 
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Hot starts

Look into Airflow Performance Fuel Injection with a Purge Valve, hot starts are a non event
 
All due respect Mickey, but u probably mean injected aircraft piston engine, wild guess, still well below 1/2 of the aircraft piston engine population ;)
True - can't recall too many hot start problems with a carb.
 
True - can't recall too many hot start problems with a carb.

On occasion I have had a hot start problem with a carb. my solution is to pull the mixture half way out and then it will start almost immediately.
 
Keep at ICO until running.

Re the Lycoming unofficial procedure:

What does the brief rich mixture setting (step 5) with the boost off and the engine not being cranked accomplish?

For my M1B, it floods it more and won't start.

If it is hot and I stop at the pumps.

To start , remain at ICO, boost maybe but start at ICO and then open the mixture. it is a multi handed procedure with some feathering of the mix as initially it is full of vapor, then at full rich it will flood and kill the engine if not at 1200+ rpm blasting everyone around.

I my head, its like this . .

The lines have vaporized all the fuel and it is in the bottom of the cylinder or down in the intake tubes, all vapor.

Throttle open 2"ish, mix untouched at ICO, the engine begins to rotate, the rich vapors don't fire and rapidly the A/F drops passes into happy zone, suddenly the engine roars, (tiny throttle techniques have failed me) Drop the throttle to a lower roar while opening mixture. a rapid movement about 1/3 then as needed, but no more than 1" out. ( I am set rich at idle anyway another story) If the engine is dying, massage mix and throttle and as last resort - tick the boost to catch but that is rare, mostly just pump the mixture to full then back to clear the vapor. I leave at 1000-1100 rpm a few seconds (10?) to clear and then drop to normal idle with about 3/4" out. YMMV for sure.

In very cold temps with negative density altitudes this engine will run lean, then when advancing throttle for TO it will stumble and then after passing the idle circuit will blast to full power like an old 2 stroke on the pipe. So the idle mix was set when quite cold leaveing the remainder of the temperatures too rich . . meaning I keep a rich-minus-3/4" setting when dropping throttle in flight unless at TO. This way I don't get so much spitting on the belly from the sniffle valve on hot days. Warm engine taxi is always with mix out 3/4" (or a little more).

Maybe after having to learn each (non-EFI) engines quirks and doing them for 60 yrs it has become a natural (and acceptable) habit. But . . .

. . . that SDS sure is sounding nice by this comparison. :D

Oly, that purge valve has been considered but there we are, another knob to fiddle with.

Larry, my friends IO540 starts with that procedure just fine too. But one day he was with and offered the technique. Did not work for my install, so no perfect procedure, experiment and listen to the engine and respond, accepting that actions can have a delay.
 
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