[NO BUG]Engine Feed knob not working

No effect noted, can start and run engine with switch in off. No change in fuel feeding on Aft or Fwd Setting.

Viper ground crew fuel feed switch flight.trk

[NO BUG]Engine Feed knob not working

That’s right, feed knob only affects which tanks are used for fuel supply which affects balancing. Off, I think, puts the jet into gravity feed? I’ll check.

No, it just turns off the feed pumps.

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Well it doesn’t work for selecting fuel feed either. I ran it the entire flight in forward and another in aft and didn’t cause any change to the relative position of the fed/aft fuel needles.

Well it doesn’t work for selecting fuel feed either. I ran it the entire flight in forward and another in aft and didn’t cause any change to the relative position of the fed/aft fuel needles.

Well that right there is a bug as running a full flight in FWD or AFT *will* cause a fuel imbalance. However leaving it in off should only be a problem in flight when you push over for negative G. In that situation you should start to lose the engine from fuel starvation if it is in off. On the ground you'd never notice the difference between off and norm.

Hi

 

As far as I am aware this is not a bug, fuel is still supplied by fuel proportioner

 

Only master fuel switch will cut fuel supply.

Well yes and no. On the ground gravity feed will still feed the FFP to feed the engine so off or norm doesn't matter. In the air if you have the switch in off so the electric fuel pumps are off and push negative G or are inverted you will starve the engine of gas since the gravity pumps are on the bottom and the fuel would now be on the top of the feed tanks.

Ok, interesting. Most jets won't gravity feed for start, and it's rare that the engine can stay running at anything but low altitude with the fuel pumps off. I will have to take off with the fuel feed (fuel pumps) off, climb and push over and see if engine starves.

Edit -

So I did just that. Fuel feed switch off, massive pushovers, neg g, inverted flight. Engine ran entire time.

Shut off fuel master, engine quickly flamed out, did a neg pushover and then turned fuel master back on, engine immediately relit with no fuel pumps on. So I'm pretty sure the fuel feed switch and fuel pumps are not yet working as they do in the real jet.

It was interesting to see in extended inverted flight the oil pressure does fall off, indicates zero, Hyd/Oil Pressure warning light comes on, But as long as I could maintain the neg G the engine never flamed out. Maybe I just didn't do it long enough. Was fun to try.

Made a ok flameout landing at the end, just for fun. Entire flight was with fuel feed switch off.

Viper neg g with fuel fee off.trk

Ok, interesting. Most jets won't gravity feed for start, and it's rare that the engine can stay running at anything but low altitude with the fuel pumps off. I will have to take off with the fuel feed (fuel pumps) off, climb and push over and see if engine starves.

Remember the engine feed switch only controls the electrical fuel pumps in the feed tanks. The gravity/siphon feed via the FFP is always working hence why you didn't see a problem in the first place.

Edit -

So I did just that. Fuel feed switch off, massive pushovers, neg g, inverted flight. Engine ran entire time.

 

 

 

Shut off fuel master, engine quickly flamed out, did a neg pushover and then turned fuel master back on, engine immediately relit with no fuel pumps on. So I'm pretty sure the fuel feed switch and fuel pumps are not yet working as they do in the real jet.

 

 

It was interesting to see in extended inverted flight the oil pressure does fall off, indicates zero, Hyd/Oil Pressure warning light comes on, But as long as I could maintain the neg G the engine never flamed out. Maybe I just didn't do it long enough. Was fun to try.

Yup that is a bug. Real aircraft won't do that for fuel feed.

Remember the engine feed switch only controls the electrical fuel pumps in the feed tanks. The gravity pumps are always working hence why you didn't see a problem in the first place.

Engine feed knob controls all of the fuel pumps (5ea total electrical pumps) in the jet.

Engine feed knob controls all of the fuel pumps (5ea total electrical pumps) in the jet.

Yes and that has nothing to do with completely stopping fuel flow to the engine when on the ground under normal G. The FFP will keep it going at that point and that isn't electrically driven but hydraulically driven.

Yes and that has nothing to do with completely stopping fuel flow to the engine when on the ground under normal G. The FFP will keep it going at that point and that isn't electrically driven but hydraulically driven.

The FFP doesn’t feed the engine, it just keeps the jet balance between forward and aft systems. The aircraft will siphon the fuel to feed the motor.

The FFP doesn’t feed the engine, it just keeps the jet balance between forward and aft systems.

By controlling what is sent to the engine itself. It doesn't maintain CG by transferring between A/L and F/R but by changing how much is taken from each system to feed the engine.

The aircraft will siphon the fuel to feed the motor.

Documentation I'm reading specifically states that in engine feed off the FFP is feeding the motor.

So with engine feed off, and the FFP handle down, what feeds the motor? What feeds the motor when the FFP shaft shears in flight? What feeds the motor when the A system hydraulic goes offline?

Documentation I'm reading specifically states that in engine feed off the FFP is feeding the motor.

Okay so with access to the docs, open the 28GS and read the chapter on engine feed, clearly states "The primary method is by siphoning action". You don't need the FFP or the electric fuel pumps to supply fuel to the motor.

Curious how many years have you worked the Viper fuel systems?