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  #1  
Old 04-10-2021, 09:04 AM
togaflyer togaflyer is offline
 
Join Date: Apr 2013
Location: Fl/Ga
Posts: 704
Default Notorious Lycoming Hot Start

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.
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  #2  
Old 04-10-2021, 09:33 AM
Robin8er Robin8er is offline
 
Join Date: Sep 2015
Location: Socal
Posts: 497
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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.
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  #3  
Old 04-10-2021, 10:00 AM
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Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
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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.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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  #4  
Old 04-10-2021, 10:58 AM
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larrynew larrynew is offline
 
Join Date: Oct 2007
Location: In New Braunfels, ist das Leben schön!
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Default 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.
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  #5  
Old 04-10-2021, 11:10 AM
rightrudder rightrudder is offline
 
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Location: Laguna Hills, CA
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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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Last edited by rightrudder : 04-10-2021 at 11:23 AM.
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  #6  
Old 04-10-2021, 11:55 AM
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Bill Boyd Bill Boyd is offline
 
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Location: Landing field "12VA"
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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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Last edited by Bill Boyd : 04-10-2021 at 11:58 AM.
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  #7  
Old 04-10-2021, 12:06 PM
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skylor skylor is offline
 
Join Date: Aug 2009
Location: Southern California
Posts: 964
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Quote:
Originally Posted by Bill Boyd View Post
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
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  #8  
Old 04-10-2021, 12:07 PM
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larrynew larrynew is offline
 
Join Date: Oct 2007
Location: In New Braunfels, ist das Leben schön!
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Quote:
Originally Posted by Bill Boyd View Post
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.
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  #9  
Old 04-10-2021, 12:09 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by togaflyer View Post
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.
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  #10  
Old 04-10-2021, 01:56 PM
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rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGY
Posts: 3,724
Default Sweep

DanH's "sweep" post was very helpful to me to understand how to start an aircraft piston engine. After reading this, I've never had a problem.

http://www.vansairforce.com/communit...eep#post905368
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