suddenly running out of fuel: harmful for the engine?

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Zacke
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Posts: 339
Joined: 27 Sep 2018
Location: EDNY

suddenly running out of fuel: harmful for the engine?

Post Zacke »

Hey guys,

because the P-40 has no gauges for the reserve and the aux tank we're prone to run out fuel temporary. I know it's a question of timing and managing the fuel tank system to avoid that. Anyway: Does it harm the engine if you run out of fuel and the propeller drives the engine until you switch to an other fuel tank. I think it's like pulling back the throttle out of high power to low idle extreme rapidly while flying fast and that can't be good for the system.

Thanks in advance,
Zacke

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Jacques
Senior Master Sergeant
Posts: 2255
Joined: 26 Jun 2011
Location: West Coast, USA

Re: suddenly running out of fuel: harmful for the engine?

Post Jacques »

I wouldn’t think so, Zacke. Its such a momentary occurrence, normally. The oil pump is engine driven, the propeller is still turning the engine over so oil pressure should still be present. Its a good question, though, so maybe a resident expert will weigh in.

Meanwhile, an interesting and accessible explanation of the “prop driving the engine”:

https://www.avweb.com/features/pelicans ... g-engines/

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DHenriquesA2A
A2A Chief Pilot
Posts: 5172
Joined: 27 Mar 2009
Location: East Coast United States

Re: suddenly running out of fuel: harmful for the engine?

Post DHenriquesA2A »

Zacke wrote:
04 Jan 2021, 04:11
Hey guys,

because the P-40 has no gauges for the reserve and the aux tank we're prone to run out fuel temporary. I know it's a question of timing and managing the fuel tank system to avoid that. Anyway: Does it harm the engine if you run out of fuel and the propeller drives the engine until you switch to an other fuel tank. I think it's like pulling back the throttle out of high power to low idle extreme rapidly while flying fast and that can't be good for the system.

Thanks in advance,
Zacke
The answer really lies in engine "management" and how you treat your engine generally. Basically it boils down to this. ANY sudden change in temperature and/or pressure inside an engine, especially an aircraft engine where the internals are closely matched, CAN be harmful.
There are always proponents who cross the T's and dot the I's but the general rule is that it's never a good idea to allow sudden changes in how the engine is operating such as a high RPM accidental OFF selection with the mag switch; sudden power changes; or sudden temperature change.
The bottom line is that anytime you can avoid these factors you are doing your engine a huge favor. Allowing these things might not immediately cause a major issue for the engine but over time, every flight you make and every time you run your engine, the engine "remembers" how it was treated.
So on your fuel tank question, if you have a choice, try and manage your fuel schedule so that you don't allow the engine to quit before switching tanks. Factor in some room in your fuel calculation designed to prevent an engine cutoff. If you aren't doing that you might be pushing your fuel vs flight time a bit too much.
In all the years I flew I never allowed a tank to drain completely dry. I always gave myself a little "room" with fuel.
Dudley Henriques

Zacke
Staff Sergeant
Posts: 339
Joined: 27 Sep 2018
Location: EDNY

Re: suddenly running out of fuel: harmful for the engine?

Post Zacke »

Thanks a lot for your input, guys!

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