Tech reason for engines shudown after being upside-down?

[eFirehawk]

Hello everyone,

 

Just a quick curiosity here, I was playing around with the A-10C and decided to go upside-down for a while but a few seconds afterwards both my engines shut down because of my silly idea, so I had to switch on the APU, turn off the Bleed Air and restart them, then do a long In-Flight NAV Alignment. :doh:

 

I am well aware that we are not supposed to do anything like that in the A-10 but I'm still curious about what is the technical reason why it happens to the aircraft. Does anybody know why the engines shut down after being upside down for a few seconds? :smartass:

 

Also, did anybody have the A-10 ownship symbol missing from the TAD after a CDU shudown and restart? Happened to me and I couldn't get the ownship symbol back after the Alignment. :noexpression:

 

Thanks

[Tizid]

Maybe the engines don't get fuel while flying upside-down?

 

After restarting, did you wait for the T=4.0.0.8? Did you also reLOAD data?

[eFirehawk]

Maybe the engines don't get fuel while flying upside-down?

 

After restarting, did you wait for the T=4.0.0.8? Did you also reLOAD data?

 

Actually I've waited for 5.0.0.8 if I recall, which is when in the In-Flight Alignment is finished and allows me to insert the navigation data. And yes I've reloaded all again. :)

[Harzach]

Actually I've waited for 5.0.0.8 I believe, which is when in the In-Flight Alignment is finished and allows me to insert the navigation data. And yes I've reloaded all again. :)

 

It's definitely 4.0.0.8. And IIRC, you can't sustain inverted/neg-G flight for more than 10 seconds or so before fuel starvation. Haven't stuck my nose in the manual for a while, though.

[GGTharos]

I am well aware that we are not supposed to do anything like that in the A-10 but I'm still curious about what is the technical reason why it happens to the aircraft. Does anybody know why the engines shut down after being upside down for a few seconds? :smartass:

 

 

The reservoirs for the engines are gravity-fed from the tanks. Those reservoirs hold enough fuel for about 10 sec of operation (obviously depending on fuel flow) in non-gravity feed (ie. less than some fraction of 1g) situation. You can continue flying upside down and feed the engines if you maintain 1g, but obviously you will fly a split-S or loop doing so.

 

 

Also, did anybody have the A-10 ownship symbol missing from the TAD after a CDU shudown and restart? Happened to me and I couldn't get the ownship symbol back after the Alignment. :noexpression:

 

Thanks

 

Alignment or data loading was not complete, or you've run into a fairly obscure bug.

[Dejjvid]

It's definitely 4.0.0.8. And IIRC, you can't sustain inverted/neg-G flight for more than 10 seconds or so before fuel starvation. Haven't stuck my nose in the manual for a while, though.

 

It's definitely not always 4.0 0.8, when you do an in flight alignment it's actually ~5.5 0.8.

[Kaiza]

Alignment or data loading was not complete, or you've run into a fairly obscure bug.

 

You mean you testers don't do an "inverted flight fuel starvation, double engine failure, flight essential bus power only, emergency APU and engine restart, inflight EGI alignment" test prior to each build being released? Sheesh. :noexpression:

[Skitter]

Any idea what is the maximum angle you can sustain before the engines start to run out of fuel ?

[MeerCaT]

Not wishing to hijack here, but it's quite closely related...

 

I've done my fair share of 'playing around' with the hog and, only yesterday in fact, I deliberately did the same thing at 13,000ft in the "Weapons Training" standard mission.

 

(Oh I've just remembered, this is a total tangent but I'll mention it anyway: I did this after attempting air-to-air refuelling, which kept failing because the tanker would connect and then disconnect with the 'complete' message all in an instant the very moment contact was made, without transferring any fuel, and would veer off to the left as if to get out of my way. I'm reasonably ok at refuelling and I know the usual procedures and nose-wheel steering button thing so I don't think I was doing anything wrong?)

 

...Anyway...

 

After starving the engines of fuel due to being upside down they cut out, I dropped and switched off both throttles, started APU, turned off left and right generators, turned on APU generator, spooled up left engine, spooled up right engine....wait a minute, what's this? Right engine never reaches idle speed!?

'Motor' the right engine for a while, then try normal start-up again but no difference.

 

Ok so I limp home on one engine, but even that seems a little under powered compared to usual (yes I do often limp around on one engine - a testament to my SAM dodging skills...or lack thereof!).

 

So engine restart problems (but only for one engine) after a fuel-starvation cut-out; any ideas what was happening here?

[Harzach]

It's definitely not always 4.0 0.8, when you do an in flight alignment it's actually ~5.5 0.8.

 

AH!

 

I'm never in that big of a hurry, so I did not know this. Thanks!

[Flamin_Squirrel]

Any idea what is the maximum angle you can sustain before the engines start to run out of fuel ?

 

It's not the angle you fly at, it's the G. Maintain positive G and you'll be fine.

[Britchot]

(Oh I've just remembered, this is a total tangent but I'll mention it anyway: I did this after attempting air-to-air refuelling, which kept failing because the tanker would connect and then disconnect with the 'complete' message all in an instant the very moment contact was made, without transferring any fuel, and would veer off to the left as if to get out of my way. I'm reasonably ok at refuelling and I know the usual procedures and nose-wheel steering button thing so I don't think I was doing anything wrong?)

 

I had this happen to me when I did a quick run to the tanker for the sole purpose of practicing AAR on Dragon's JTAC Day Training. I thought it was because I had too much fuel at the time, since I just took off. Either I did have too much fuel and this could be your case as well or I had a similarly inexplicable error.

[Maachine]

i found this out as well the hard way too, except i was only at 5000 ft. i made a crash landing and survived though. that was cool.

 

i thought "you know i could turn upside down and am able to keep my eyes on these tanks here . then i could just dive in for a gun run". yep, 10 seconds later, i had to crash land

[eFirehawk]

Alignment or data loading was not complete, or you've run into a fairly obscure bug.

 

Indeed it was a bug, I tried to do it again 3 times to take a screenshot and post the track... :joystick: But the ownship symbol didn't go missing anymore :P

[Gunny Huntarr]

Thanks for this tread. I did not realize why I was getting a flameout, I kept thinking it was a bird strike or some random malfunction.