[CANNOT REPRODUCE] Emergency EPU doesn't work

[Papa Saubär]

Hello gentlemen,

 

today I tested official "Diversion Decision". After a 52 NM (400 LBS) and 113 NM (800 LBS) flight I lost my engine and the electric, so the EPU should give me my electric back, but it doesn't.

 

Although the EPU switch is set to NORM (or later to ON), the EPU is not (auto or manual) started up.

 

 

EPU Control Panel

The EPU is a hydrazine-powered, self-contained unit that can provide emergency hydraulic and electrical power for about 10 to 15 minutes. You would most often use this if you lose your engine, and the EPU would provide power to the hydraulic and electrical systems.

(from the Manual, Page 31)

 

 

For example:

 

Fuel State 0, Engine Shutdown, EPU should go on, but it doesn't. EPU Fuel State 100%, EPU Switch NORM/ON.

 

 

 

 

Trackfiles

 

Downloadlink: https://1drv.ms/u/s!Attcq6zW0_Fbi89iWFj-g6G_GUeo4A?e=CWbIUN

 

...Test2, 52 NM Flight, EPU Mode NORM

...Test3, 113 NM Flight, EPU Mode NORM and after shutdown to ON

 

 

Thanks! :thumbup:

[mvsgas]

In the air DCS F-16 EPU works fine, on the ground tho, it turn off which has been reported.

https://forums.eagle.ru/showthread.php?t=254829

https://forums.eagle.ru/showthread.php?t=251544

 

Remember, IIRC, EPU power only emergency AC power buses, it should take a few seconds to start and get to operational speed, the more you use the flight controls, the shorter the operational time (meaning it will use more fuel).

[Frederf]

I watched the track. The engine turned off about 5 seconds before touchdown and the EPU did come on very briefly. I don't know what you experienced or were expecting but it looks normal to me.

 

The one thing I don't know is how the EPU changes with WOW. I noticed in DCS it flickers on and off when you touched down. I think it would be not the case in the real airplane that EPU would shut off the instant the wheels touched the ground because ground control during landing roll may benefit from flight control hydraulics.

Edited April 12, 2020 by Frederf

[QuiGon]

I just performed an Emergency Landing last week when I ran out of fuel during the initial landing approach. The EPU came online automatically just fine. It powered off on touchdown though.

 

 

Edit: The flight started on a Cold Start.

[Papa Saubär]

Thanks for your answers guys!

 

I didn't know the reported bug, which mvsgas posted. I used the search function.

 

 

I watched the track. The engine turned off about 5 seconds before touchdown and the EPU did come on very briefly. I don't know what you experienced or were expecting but it looks normal to me.

 

The EPU should stay alive, especially when the switch is ON (not NORM).

[Talvid]

Does the EPU switch have to be in an (armed) position for it to auto activate on engine flameout?

[=Panther=]

Does the EPU switch have to be in an (armed) position for it to auto activate on engine flameout?

 

The default position (middle) is an armed state. If the jet needs it, it will fire from there. If the pilot wants to fire it manually, he/she would raise the forward guard and place the switch forward to fire the EPU.

[randomTOTEN]

Can anybody else get OP's tracks to play? Frederf states he did.

Turned out I had some sort of problem with track saving/playing. It appears I fixed that now.. but these tracks refuse to play. Redownloaded them too.... hmmm...

 

 

EDIT: Tested myself. At 0 lbs fuel EPU comes on, comes one while airborne if I move the EPU switch to ON with running engine. All cases it turns off on WOW.

 

 

Also my JFS seems to run quite happily with 0 lbs jet fuel. Does it use unusable fuel?

Edited April 12, 2020 by randomTOTEN

[Frederf]

If you takeoff with EPU switch NORM and then turn it OFF and then shut down the engine then EPU will operate even with switch OFF provided the trigger condition is main and standby generator failure (both) which it will be since the engine is off. However if you takeoff with switch OFF and keep it there it won't operate under any condition.

 

NORM triggering conditions are as above plus A & B hydraulic <1000 psi. It says it's designed for "gen failures, dual hydraulic failures, PTO shaft failure, and DG failure but I think those latter ones involve gen and hydraulic failures as initial failures with the last of the list being consequences thereof. The exception is normal shutdown or main pwr to off without delay in batt position.

 

ON runs the thing manually.

 

Hydrazine augments bleed air if necessary which is always when initially starting except for ground testing.

 

In summary the EPU should run in NORM or ON throughout a flameout approach, landing, and ground rollout.

[randomTOTEN]

It's also (currently) not possible to start the EPU with WOW from a cold start. Might be related to the shutdown on landing, but I cannot get it to run on the ground by any means other than the EPU test.

 

 

If I enter a cold aircraft, set the power switch to MAIN PWR, then immediately go EPU ON, the EPU should start...correct?

Edited April 13, 2020 by randomTOTEN

[Frederf]

Shouldn't even need main pwr switch to main pwr. Batt should be enough. I don't see any reason why MAIN PWR -> BATT and EPU to ON shouldn't fire the EPU.

 

Maybe they're modeling the EPU safety pin? I don't know.

[randomTOTEN]

Yeah I tried BATT first, then tried again at MAIN PWR

 

this stuff is no joke, wow!

 

 

Maybe they're modeling the EPU safety pin? I don't know.

I'm torn. On one hand, it would be neat to have a ground crew command to place/remove EPU safety pin. But if that was true a large majority of users would go flying with the pin in place! :joystick:

[mvsgas]

Also my JFS seems to run quite happily with 0 lbs jet fuel. Does it use unusable fuel?

It should not, JFS uses aircraft fuel. But, it is possible for there to be enough fuel on the line to run the JFS for minutes. There might be not enough fuel for the main engine, but there could be enough for the JFS.

 

It's also (currently) not possible to start the EPU with WOW from a cold start. Might be related to the shutdown on landing, but I cannot get it to run on the ground by any means other than the EPU test.

 

 

If I enter a cold aircraft, set the power switch to MAIN PWR, then immediately go EPU ON, the EPU should start...correct?

 

That is correct behavior for the EPU. With weight on wheels (WOW), it should not start, even when with the switch to on. But, if it turns on in the air, it should not turn off until it has WOW and pilot turn it off.

[Papa Saubär]

Hello there,

 

I checked the tag [CANNOT REPRODUCE]. I think it's a real shame that you don't even get an answer, even though you really tried to write and test this behavior.

 

So I decided to build a short "Flameout Mission" and make new trackfiles and short youtube clips. With these material everyone could see the wrong behauvior that mvsgas also described.

 

EPU NORM, after WoW goes off.

 

EPU ON, after WoW goes also off.

 

Please review and reconsider.

Flameout_F-16C.miz

Flameout_F16C_Track.trk

Flameout_F16C_Track2.trk

[=Panther=]

It should not, JFS uses aircraft fuel. But, it is possible for there to be enough fuel on the line to run the JFS for minutes. There might be not enough fuel for the main engine, but there could be enough for the JFS.

 

 

 

That is correct behavior for the EPU. With weight on wheels (WOW), it should not start, even when with the switch to on. But, if it turns on in the air, it should not turn off until it has WOW and pilot turn it off.

 

Umm no, WOW has no affect on EPU running. EPU system isn't tied to the WOW circuit that would prevent the system from running if the switch is in ON or NORM (if a system failed tripping the EPU granted the safety pin is out).

Edited April 13, 2020 by =Panther=
Edited for clarity

[Bouli306]

It should not, JFS uses aircraft fuel. But, it is possible for there to be enough fuel on the line to run the JFS for minutes. There might be not enough fuel for the main engine, but there could be enough for the JFS.

 

 

 

That is correct behavior for the EPU. With weight on wheels (WOW), it should not start, even when with the switch to on. But, if it turns on in the air, it should not turn off until it has WOW and pilot turn it off.

 

That last statement is not true. On the ground with the EPU safetypin removed..placing the EPU switch to ON WILL fire the EPU. Also when ground ops done with the switch in NORM when the Main and STBY gen fail or both hydraulics drop below 1000PSI the EPU will also fire.

Edited April 13, 2020 by Bouli306

[Bouli306]

Umm no, WOW has no affect on EPU running. EPU system isn't tied to the WOW circuit at all, system should run if the switch is in ON or NORM if a system failed to trigger an EPU firing.

 

Your statement is not completely correct: with WOW and throttle below idle the EPU will also not fire. SO in case of engine shutdown without the EPU safety pin installed the EPU will not fire when the throttle is below idle and WOW is triggered

[mvsgas]

So to sum it up and correct mistakes:

The switch on and no ground safety pin installed

EPU should fire no matter what. If engine bleed air is available, it will use bleed air but will use Hydrazine initially and it will use hydrazine to maintain operational RPM if the engine is not providing enough bleed air.

 

Switch in norm,

EPU should not fire on the ground, will fire in the air if both generator fail and A system pressure below 1000 psi.

 

Switch to off

Will not fire on the ground, if the switch is left off since WOW, it will not fire in the air. If the switch is cycled to norm and back to off, the EPU will fire if both generator fall offline or A system pressure below 1000psi. It will not turn EPU off in the air if previous conditions exists.

It will turn the EPU off if WOW or if the previews conditions do not exist.

 

Panther, Bouli306

What did I miss?

 

And we all agree it should remain on after landing, correct?

Edited April 13, 2020 by mvsgas
spelling

[=Panther=]

Your statement is not completely correct: with WOW and throttle below idle the EPU will also not fire. SO in case of engine shutdown without the EPU safety pin installed the EPU will not fire when the throttle is below idle and WOW is triggered

 

Since the topic was about a bug report I was focusing on the scenarios played out in the thread. So I rushed through what I was trying to say, but I edited it for clarity. I think we are all on the same page now. I’ve spent far too many hours in hazmat suits cleaning up EPU activations, the fumes are great!

[randomTOTEN]

Please review and reconsider.

Papa,

 

I just watched your Flameout_F16C_Track.trk.

 

At the point of engine failure, while you are still airborne, your EPU starts, and runs until WOW when it incorrectly shuts down.

Your EPU switch is guarded in NORM, the EPU green light is ON, and so are both AIR and HYDARZ (however it's spelled) yellow lights.

 

Your OP is titled "EPU doesn't work", but that's the indications that the EPU is indeed running. There are indications that the EPU is running in both your videos too.

 

It sounds like maybe a misunderstanding of why the EPU is there, and what it does. You state,

I lost my engine and the electric, so the EPU should give me my electric back, but it doesn't.

The manuals states provide emergency hydraulic and electrical power... that's not power to everything. Only those systems you must absolutely have to safely land the airplane following an engine failure. FLCS has no mechanical link to the stick. You need electrics to give commands, and the controls need hydraulic pressure to move. You need backup instruments to maintain control and find a runway.

 

You don't need MFD's, DED, FCR, TGP, RWR, JMR, GPS, Weapons, and a bunch of other useless stuff that takes away electricity from the systems that keep you alive. Don't expect it while you're seconds of a runway with a failed engine.

[Bouli306]

So to sum it up and correct mistakes:

The switch on and no ground safety pin installed

EPU should fire no matter what. If engine bleed air is available, it will use bleed air but will use Hydrazine initially and it will use hydrazine to maintain operational RPM if the engine is not providing enough bleed air.

 

Switch in norm,

EPU should not fire on the ground, will fire in the air if both generator fail and A system pressure below 1000 psi.

 

Switch to off

Will not fire on the ground, if the switch is left off since WOW, it will not fire in the air. If the switch is cycled to norm and back to off, the EPU will fire if both generator fall offline or A system pressure below 1000psi. It will not turn EPU off in the air if previous conditions exists.

It will turn the EPU off if WOW or if the previews conditions do not exist.

 

Panther, Bouli306

What did I miss?

 

And we all agree it should remain on after landing, correct?

 

Switch in norm,

EPU should not fire on the ground if everything is okay. But when both generators fail or bith hydraulic A and B are below zero, will fire in the air if both generator fail and A and B system pressure below 1000 psi.

 

Switch to off,

In air will turn the EPU off in all cases except both generators still offline. When they are reset you can shut it down.

 

When going airborne with switch in off the EPU will not fire automatically even when going to NORM. Switching the switch norm to off will not fire the epu..only on will do that. It is A & B system.

 

End yes it should remain on after landing

Edited April 13, 2020 by Bouli306

[mkiii]

If it turned off the instant your wheels touched down, it would make stopping the aircraft very interesting - and involve the barrier - not really a good idea in something with no canopy frame to hede behind ;)

 

 

Also it would have meant all the Hydrazine emergency drills we did in Germany in the 80s with full NBC gear were a waste of time.

[Bouli306]

If it turned off the instant your wheels touched down, it would make stopping the aircraft very interesting - and involve the barrier - not really a good idea in something with no canopy frame to hede behind ;)

 

 

Also it would have meant all the Hydrazine emergency drills we did in Germany in the 80s with full NBC gear were a waste of time.

 

You still have 75 seconds of braking action.

[Papa Saubär]

Hello there,

 

I checked the tag [CANNOT REPRODUCE]. I think it's a real shame that you don't even get an answer, even though you really tried to write and test this behavior.

 

So I decided to build a short "Flameout Mission" and make new trackfiles and short youtube clips. With these material everyone could see the wrong behauvior that mvsgas also described.

 

EPU NORM, after WoW goes off.

 

EPU ON, after WoW goes also off.

 

Please review and reconsider.

 

No answer from a ED employee? :(