mtsu_av8er
Well-Known Member
LMAO . . . close the banks and cancel the mail!!!:rotfl:
NOT an option once you leave flight instruction and fish spotting.
Cold weather engine starting tips
- Thread starter jrh
- Start date
LMAO . . . close the banks and cancel the mail!!!:rotfl:
NOT an option once you leave flight instruction and fish spotting.
jrh
Well-Known Member
Why will pumping the throttle increase the risk of a fire? Because of extra fuel being injected? How about in aircraft without a fuel pump connected to the throttle? How is this different than pumping the primer when the engine catches?
Just curious...I've never heard of this being risky.
tgrayson
New Member
I believe it's a matter of where the fuel is going when you pump the throttle. It's going into the carburetor, where it can pool if the air is not flowing steadily into the engine. A backfire could cause it to ignite. When you prime the engine with a primer, the fuel is going directly to the cylinders. If you did not have an accelerator pump attached to the throttle, there is no risk, but no benefit either, since pumping the throttle would do nothing.
Our chief mechanic used to lecture us on not to pump the throttle at flight instructor meetings and, after he was done, our Chief Flight Instructor would tell us how to do it properly.
If you pump as you crank, there is probably little risk, since the atomized fuel will be sucked into the cylinders. It's when you pump for a while and then try to start that the larger danger occurs, so they say.
Since the flight instructor turnover has been so quick in the past decade, this issue might be less well known than it used to be. The prevalence of fuel injected engines also makes it less relevant.
jrh
Well-Known Member
Good to know!
I always pumped as I cranked, and never saw a reason to pump before cranking, so I guess I've been safe without knowing it.
And don't worry, I never pump the throttle on planes without accelerator pump
I just wanted to make sure there was nothing risky about moving the throttle while cranking.
I always pumped as I cranked, and never saw a reason to pump before cranking, so I guess I've been safe without knowing it.
And don't worry, I never pump the throttle on planes without accelerator pump
I just wanted to make sure there was nothing risky about moving the throttle while cranking.
sopdan
Well-Known Member
Here's my experience in cold wx:
C172R: never have any trouble getting it started if you: turn on pump, push mixture full rich until FF gauge spikes, then idle cutoff, pump off... crank it and it will almost always start up within 3-4 turns of the prop... though my employer much prefers preheating, so I do it to avoid getting a talking to. (I actually use this procedure year 'round with excellent results)
Motorglider (Grob): if it's not preheated, don't expect the prop to turn more than half way... after a few seconds it might do another half turn, and if you get anything else out of it, you have just witnessed an act of God. On the plus side, it's got a real small engine (along the lines of maybe a half cylinder), so it only takes a couple minutes to preheat.
C172R: never have any trouble getting it started if you: turn on pump, push mixture full rich until FF gauge spikes, then idle cutoff, pump off... crank it and it will almost always start up within 3-4 turns of the prop... though my employer much prefers preheating, so I do it to avoid getting a talking to. (I actually use this procedure year 'round with excellent results)
Motorglider (Grob): if it's not preheated, don't expect the prop to turn more than half way... after a few seconds it might do another half turn, and if you get anything else out of it, you have just witnessed an act of God. On the plus side, it's got a real small engine (along the lines of maybe a half cylinder
), so it only takes a couple minutes to preheat.
I believe it's a matter of where the fuel is going when you pump the throttle. It's going into the carburetor, where it can pool if the air is not flowing steadily into the engine. A backfire could cause it to ignite. When you prime the engine with a primer, the fuel is going directly to the cylinders. If you did not have an accelerator pump attached to the throttle, there is no risk, but no benefit either, since pumping the throttle would do nothing.
Our chief mechanic used to lecture us on not to pump the throttle at flight instructor meetings and, after he was done, our Chief Flight Instructor would tell us how to do it properly.
If you pump as you crank, there is probably little risk, since the atomized fuel will be sucked into the cylinders. It's when you pump for a while and then try to start that the larger danger occurs, so they say.
Since the flight instructor turnover has been so quick in the past decade, this issue might be less well known than it used to be. The prevalence of fuel injected engines also makes it less relevant.
All true.
And to add: When you prime Continentals, the fuel is being injected into the carb mounted on the bottom of the engine, not the cylinders. So priming before cranking is a bit of a wasted effort. In lycomings, yeah, right into the cylinders.
Pumping the throttle before cranking spits fuel out of the carb, only to fall and pool increasing the risk of a fire. Pumping the throttle about a third of the way during cranking does as TGrayson said above, and is good technique.
Source: Chief A&P and owner of an aviation maintenance facility.
surreal1221
Well-Known Member
tgrayson
New Member
But yes, only pump when cranking. . .no other point for me to pump the throttle just for the hell of it.
People do, in fact, do that. It DOES work, even when you're not cranking. I've seen patterns like 1 shot of primer, three pumps on the throttle, and then start turning the engine over. If it doesn't start, a few more pumps on the throttle, then start cranking again.
Also, I believe that there are a few older airplanes that have no priming mechanism other than throttle pumping.
People can get addicted to this method of starting; I've rarely found it necessary. At most, as the engine is coughing to life, a brief thrust of the throttle is often all it takes to spring the engine to life.
surreal1221
Well-Known Member
I've only done it once personally. And that was yesterday morning at 9am. I usually fly in the afternoon, after the plane has been flown a couple times already that day so no real need for me to stress over a start.