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Engine sputtering when fuel low


Nealius
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All manuals, guides, and tutorials on fuel management talk about switching fuel tanks when the engine starts to sputter. 

 

Problem is, we get no sputter. The engine suddenly dies and the prop windmills, inducing a mild panic attack while scrambling to switch to a full tank. 

 

Could we get some kind of sputter effect before the engine actually dies? 

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Yes I don’t see why we could have a bit more warning as the tank gets low. Your car engine typically doesn’t just quit as your fuel runs out, rpm will start to drop and return as the remaining fuel sloshes around and pickup becomes sporadic.

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Only indication  of fuel tank being emptied  is fuel pressure dropping down. 

Main danger is engine wind milling, since it will kill master bearing, heaving no warning that tank will dry out soon is very dangerous.

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5 hours ago, grafspee said:

Only indication  of fuel tank being emptied  is fuel pressure dropping down. 

Main danger is engine wind milling, since it will kill master bearing, heaving no warning that tank will dry out soon is very dangerous.

 

I can hawk the gauge this time but I don't recall seeing a drop in fuel pressure. There are also situations (thinking of the Mustang) where external tank pressure drops at altitude. 

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Posted (edited)
41 minutes ago, Nealius said:

 

I can hawk the gauge this time but I don't recall seeing a drop in fuel pressure. There are also situations (thinking of the Mustang) where external tank pressure drops at altitude. 

First fuel pressure drops to 0 after short time engine quits.

External fuel tanks in P-51 are pressurized via engine's supercharger.

Fuel pressure drops because fuel pump draws from lower pressure level, and fuel gauge shows absolute fuel pressure not delta pressure made by fuel pumps. 

If fuel pump pumps 15lbs square inch at SL which is about 1 atm you cant expect that at high alt gauge will remain at 15lbs


Edited by grafspee

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On 6/1/2021 at 12:02 AM, grafspee said:

First fuel pressure drops to 0 after short time engine quits.

 

 

 

I find this not to be the case in the Jug. The engine suddenly quits, and the fuel pressure drops from the blue range to 0 simultaneously. There is absolutely zero warning. The only way to switch tanks without the engine dying is to leave some fuel sloshing around in the aux tank.

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It's been ages since I last tried running the tank dry in the Mustang. How does it work there for comparison?

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11 minutes ago, Art-J said:

It's been ages since I last tried running the tank dry in the Mustang. How does it work there for comparison?

As i remember pretty much same thing, first fuel pressure drop then after short time engine quits.

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Except in the Jug fuel pressure doesn't drop first. The engine quits and the fuel pressure needle instantaneously goes from 23 to 0 like a binary switch.

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2 hours ago, Nealius said:

Except in the Jug fuel pressure doesn't drop first. The engine quits and the fuel pressure needle instantaneously goes from 23 to 0 like a binary switch.

That is interesting, last time i played with fuel selector switch i notice small delay. I just realized that in P-47 we are not using any electric fuel pump, only engine driven pump. So system is a bit different than in P-51

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An electric-driven booster pump is mounted in each fuel tank in the P-47...

 

Only difference between the P-47 and the P-51 is that the booster pumps in the P-47 are variable-speed pumps and pilot could set pump speed via the Fuel Booster Pump Rheostat placed on the Main switch box.

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Posted (edited)
30 minutes ago, saburo_cz said:

An electric-driven booster pump is mounted in each fuel tank in the P-47...

 

Only difference between the P-47 and the P-51 is that the booster pumps in the P-47 are variable-speed pumps and pilot could set pump speed via the Fuel Booster Pump Rheostat placed on the Main switch box.

I know but, in manual fuel pumps are always off. It is not like in P-51 where you have to turn fuel pump to start up engine.


Edited by grafspee

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No, it is exactly the same like in the P-51.

 

When the selector control valve is in position for any fuel tank (main or auxiliary), the booster pump in that fuel tank is automatically switch ON by rotary switch mounted on the selector valve control shaft...

F-14A/B

P-51D | P-47D | Spitfire | Fw 190D | Fw 190A | Bf 109K | WWII Assets Pack

Normandy | The Channel

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Posted (edited)
57 minutes ago, saburo_cz said:

No, it is exactly the same like in the P-51.

 

When the selector control valve is in position for any fuel tank (main or auxiliary), the booster pump in that fuel tank is automatically switch ON by rotary switch mounted on the selector valve control shaft...

But in P-47 fuel pressure remain 0 until engine is running, so for start up all fuel pumps are off, it would show fuel pressure after battery being switch on but its not.

04uV1ZT.png

fuel rethostat in off position for start and flight.


Edited by grafspee

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45 minutes ago, grafspee said:

fuel rethostat in off position for start and flight.

 

If you think that the Rheostat "Start and Altitude" position means Off.

 

but, i don`t think so...

F-14A/B

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Normandy | The Channel

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26 minutes ago, saburo_cz said:

If you think that the Rheostat "Start and Altitude" position means Off.

 

but, i don`t think so...

Just try it, if you move it a little bit you can hear fuel pump starting up, very noticeable sound, and fuel pressure rises up.

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booster pump.JPG

F-14A/B

P-51D | P-47D | Spitfire | Fw 190D | Fw 190A | Bf 109K | WWII Assets Pack

Normandy | The Channel

F-86 | F-16C | A-10C | FC-3 | Syria | PG | NTTR | CA | SC |

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Posted (edited)

So this is modeled wrong in DCS. I can hear fuel pump starting up while moving from start position.


Edited by grafspee

I9 9900KF Stock, Gigabyte Z390 Aorus PRO, Ram 32 GB G.skill, Palit Gamerock OC 3090, Hotas Warthog, T.Flight Rudder Pedals, 4K 49" screen.

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Yes, it seems to modeled incorrectly for DCS P-47.

 

Video in link below shows engine start, after cold propeller rotation (2:20), pilot switch something ON (i am pretty sure that it is fuel selector valve switched to MAIN, but it is not visible) low next to his left leg and noise like from electric pump starts and fuel pressure indicator needle rises from zero value.

After the engine started, the fuel pressure indicator needle rises again to operating range.

 

https://www.youtube.com/watch?v=ppqOMtQtqno

F-14A/B

P-51D | P-47D | Spitfire | Fw 190D | Fw 190A | Bf 109K | WWII Assets Pack

Normandy | The Channel

F-86 | F-16C | A-10C | FC-3 | Syria | PG | NTTR | CA | SC |

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So there seem to be two issues - something's fishy with the pump operation itself, plus, animation of pressure gauge needle not being properly finished yet (like with hydro pressure needle). I think a new thread in the bug section should be started, either summing up what we've discovered so far, or pointing to this thread.

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Fuel gauge animation looks fine for me

 

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^ I was talking about what Nealius noticed above - the animation of needle switching from something to zero in a "digital" matter when the tank runs dry.

 

Just checked in latest version and looks like that's not the case anymore. The needle moves smoothly. Whether it should drop before or after the engine quits is still another matter.

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