Storing airplane with throttle wide open

RyanB

RyanB

Super Administrator
Management Council Member
PoA Supporter
Joined
Jul 21, 2010
Messages
16,524
Location
Chattanooga, TN
Display Name
Display name:
Ryan
what’s the science behind this? I’ve seen several photos of folks who store their airplane with the throttle wide open. I probably should know this, but I admittedly don’t.

:)
 
It’s not so much storing it as shutting it down...in older airplanes without an idle cut off mixture, you’d shut the engine down by turning the mags off, and then wide open throttle would reduce the amount of fuel that got pulled into the cylinders until the prop stopped.

Some people still do that, even though they don’t know why other than “That’s what my instructor taught me.”

And there may be other reasons, but I can’t think of them. ;)
 
It is done as a public service and a warning to others about the dangers of hand propping. This way, if the mags are hot, and someone flips the prop for some reason or another, the throttle is wide open and they get chopped into little bits as the airplane runs them down.
 
Hmmm... I leave throttle at 1000RPM and then mixture to idle cut-off. Engine shuts off.

When starting, I use boost pump and prime, NOT touching the throttle, and it starts really close to 1000RPM.
 
Maule ,with a aircraft that has no mixture control I am interested in how full throttle would actually result in lower full pull than idle. I am not disbelieving you but in 40 years of owning such aircraft this is news to me . was I just rickroled or onioned?;)
 
hotprops said:
Maule ,with a aircraft that has no mixture control I am interested in how full throttle would actually result in lower full pull than idle. I am not disbelieving you but in 40 years of owning such aircraft this is news to me . was I just rickroled or onioned?;)
Click to expand...
There’s a separate idle jet in the carb, placed right at the butterfly valve when the butterfly valve is closed. Even at the low rate that the pistons pull air through the carb, it generates a significant venturi to pull fuel into the carb. Wide open throttle gets the butterfly valve away from the idle jet.
 
SixPapaCharlie said:
I've always just gone full rich and then turn the mags off. If a cylinders are full of fuel than there's no room for water to condensate. Duh
Click to expand...

Thread title is asking about throttle position, not mixture position.
Trying to deliberately hijack the thread are we?

Reported :p
 
Ravioli said:
Hmmm... I leave throttle at 1000RPM and then mixture to idle cut-off. Engine shuts off.
Click to expand...
That’s what I do too, but the throttle remains closed once the prop stops. In fact, I was out at the airport just a few nights ago and a transient C150 was on the ramp and they left it with the throttle wide open. I’ve seen it more and more...
 
All the knobs fully in gives you more knee room. Also, less likely to catch on something when crawling across a one-door low wing.
 
Maybe a poll is needed for this. I have never heard of it.
 
Actually, my manual does in fact say to go to full throttle and then shut down.

My manual for my John Deere mower.
 
Full throttle and mixture dumps the fuel out of the lines on a Lycoming IO360. I sometimes do this in preparation for a hot start, allows fresh avgas to cool the lines enough not to start vaporizing.


Tom
 
MooneyDriver78 said:
Full throttle and mixture dumps the fuel out of the lines on a Lycoming IO360. I sometimes do this in preparation for a hot start, allows fresh avgas to cool the lines enough not to start vaporizing.


Tom
Click to expand...
There’s an answer!
 
asicer said:
All the knobs fully in gives you more knee room. Also, less likely to catch on something when crawling across a one-door low wing.
Click to expand...

Sounds like an obsessive-compulsive making sure all the knobs line up. :goofy:

Dean V said:
Maybe a poll is needed for this. I have never heard of it.
Click to expand...

Me neither.

I wonder if these people also put all the switches in the same position on shut-down. :idea:
 
hotprops said:
Maule ,with a aircraft that has no mixture control I am interested in how full throttle would actually result in lower full pull than idle. I am not disbelieving you but in 40 years of owning such aircraft this is news to me . was I just rickroled or onioned?;)
Click to expand...
WOT at low RPM will not create any vacuum to pull fuel out of float bowl.
 
MooneyDriver78 said:
Full throttle and mixture dumps the fuel out of the lines on a Lycoming IO360. I sometimes do this in preparation for a hot start, allows fresh avgas to cool the lines enough not to start vaporizing.


Tom
Click to expand...
Can you please explain this further? I have the same engine and hot start it the same way. I don't think I ever knew the reason why I should start it this way other than what my engine mechanic told me. I've forgotten, or just didn't listen to him on why.
 
Eric Stoltz said:
Can you please explain this further? I have the same engine and hot start it the same way. I don't think I ever knew the reason why I should start it this way other than what my engine mechanic told me. I've forgotten, or just didn't listen to him on why.
Click to expand...

I’m not a mechanic so...I’m just regurgitating what my mechanic told me. It seems like if the stop is just 5 minutes, standard hot start procedure works, but if 10 minutes or more...then the avgas vaporizes in the lines, and it just coughs and sputters. So firewalling controls dumps all the vapors...you will see fuel pressure drop when you do this.


Tom
 
Ryanb said:
what’s the science behind this? I’ve seen several photos of folks who store their airplane with the throttle wide open. I probably should know this, but I admittedly don’t.

:)
Click to expand...

Old wives tale? Stupidity? Complacency? Wanting to make a nicer home for a mouse?

If you want to open the throttle after mixture cut-off / mags off, as the engine is winding down, whatever. But don't leave it that way. That is a link in the chain of events of an incident down the road.
 
Capt. Geoffrey Thorpe said:
It is done as a public service and a warning to others about the dangers of hand propping. This way, if the mags are hot, and someone flips the prop for some reason or another, the throttle is wide open and they get chopped into little bits as the airplane runs them down.
Click to expand...

This started out sounding so serious that I actually paid attention....:lol::lol:
 
SixPapaCharlie said:
I've always just gone full rich and then turn the mags off. If a cylinders are full of fuel than there's no room for water to condensate. Duh
Click to expand...

Yes.... It's like having a few drinks before lunch.
Because it's just not good to eat on an empty stomach.
 
Moving the throttle frightens me, I do it as little as possible.
 
so I always thought having cylinder's coated with oil rather than raw avfuel would be better for storage/sitting, whether it be short or long.
 
How about this: it is of no consequence one way or the other. The engine is not running therefore the position of the throttle is meaningless.
 
Silvaire said:
How about this: it is of no consequence one way or the other. The engine is not running therefore the position of the throttle is meaningless.
Click to expand...
You must not understand how a carbureted engine works.

If you move the throttle while the engine is not running (Ie., trying to pump the throttle to get the engine to start), fuel drips downward out of the "bottom" or inlet side of the carburetor. Too much (easy to do) will drip out, and load the inlet box, and can also drip to the ground. If the engine has even a small backfire, it may ignite the additional fuel there, which will rapidly heat up the carb which has an ample supply of more fuel, ultimately leading to an engine fire.

So moving the throttle while the engine isn’t running is NOT meaningless.
 
Silvaire said:
How about this: it is of no consequence one way or the other. The engine is not running therefore the position of the throttle is meaningless.
Click to expand...
Unless you also select alternate air source. Then the bugs have a pathway into your engine. Still, I always left my throttle where it was at idle, and yanked the mixture.
 
You must log in or register to reply here.
Back
Top