[RESOLVED] Engine fires again

[Reflected]

I'm getting engine fires again when flying straight and level, approaching Mach 1

 

Edited January 28, 2021 by IronMike

[fat creason]

I tested this extensively and never got engine fires in level flight at any speed. Is there a consistent way to reproduce this? F-14A only, right? What's your loadout?

[Reflected]

I was at 30k feet in a level flight at Mach 1ish, 1 phoenix (already fired), 2 Sparrows, 3 Aim-9s, and 2 bags (jettisoned). F-14A. I had refueled during the mission.

[IronMike]

this is so weird. thanks for reporting.

[Flash_111]

34 minutes ago, IronMike said:

this is so weird. thanks for reporting.

I am also experiencing this- 2 external tanks, 2 sidewinders and 2 sparrows on the glove, 2 phoenix and 1 sparrow in the tunnel. 30-40k feet altitude block, level flight. Attempting to accelerate through mach 1.1, TIT will spike and the engines catch fire and fail after about 20 seconds. In an unloaded dive I still get the temp spike, but its short enough the engine does not appear to take damage. Clean jet will also get the mach 1.1 temperature spike in level flight but I assume the drag is low enough that it ends up passing through the spike quick enough that damage does not result.

[IronMike]

17 minutes ago, Flash_111 said:

I am also experiencing this- 2 external tanks, 2 sidewinders and 2 sparrows on the glove, 2 phoenix and 1 sparrow in the tunnel. 30-40k feet altitude block, level flight. Attempting to accelerate through mach 1.1, TIT will spike and the engines catch fire and fail after about 20 seconds. In an unloaded dive I still get the temp spike, but its short enough the engine does not appear to take damage. Clean jet will also get the mach 1.1 temperature spike in level flight but I assume the drag is low enough that it ends up passing through the spike quick enough that damage does not result.

 

Thank you, I hope this points us to the core of the issue, it sounds like it.

[Calinho]

I have the exact same problem

 

Reported at Patch Dec 17th Feedback Thread

 

 

[FoxTwo]

Yup. Just happened to me. Climbed up to around 40,000ft in full AB, just above mach 1.0, leveled off, engines caught fire.

 

Engine temps weren't excessive.

[gulredrel]

DCS/2.5.6.59625 Caucasus map

Similar for me. Clean aircraft, only phoenix pylons in the tunnel. Was level at 36000ft, engaged slowly until zone 5 afterburner. Plane accelerated from 0.85 Mach to around 1.0 Mach. slowly going supersonic, left engine stall warning and than engine fire on both engines.

 

edit: posted a track here, as there is more to this topic: 

 

Edited December 31, 2020 by gulredrel

[captain_dalan]

Happened to me on two separate occasions. Two weeks ago, on MP session, with an F-15 buddy. We climb to 30000ft, doing around mach 0.9 i detect some bombers over the horizon and we throttle up to intercept. I carry 4x2x2 plus two tanks. I drop the tanks to lose drag. Plane won't go past the mach number. Then i get stall in left engine warning then stall in right engine warning, then fire alert in each engine.

The other time was today on a speed run. I dope all ordnance, climb to 35000ft, full burner, the plane accelerates up to mach 1.2 then suddenly stall warnings. I throttle down, wait for the alert to extinguish. Then power up again and the problem is gone. Also during the same run i notice the plane is subsonic with ordnance on wing glove pylons and barely supersonic with Sparrows in the funnel. But i'm going to make another report on that one.

[Sideburns]

I've also had this issue a few times tonight, around mach 1.0-1.15, 30,000-35,000ft. Worse in level flight (as stated earlier a dive through this speed region seems to get through the dangerpoint before it is an issue. If I was to guess the problem speed range it would be M1.05-M1.13). At some point the engine can enter a dangerous state with fuel flow and temperature for both engines oscillating rapidly. Stall light flash. Sometimes if you are quick enough and throttle to idle it avoids the dual engine fire, temperatures settle and stall lights go out. Sometimes you get two stall light flashes and it is over.

 

Edit: To be clear fairly sure I can reproduce this if you want a track or video.

Edited January 19, 2021 by Sideburns

[Golo]

I tried but I can not induce the stall/fire at all. I was thinking, could it be something with AICS system? Maybe the inlet ramps hydr/scheduling failure? AICS operation in NATOPS is very interesting and deserves to be looked at.

 

Here is a short snippet from 14B - 2.1.3.2 Fail-Safe: ...If the hydraulic shutoff valve closes above Mach 0.9, the ramps are normally in an unsafe configuration and the appropriate RAMPS caution light will accompany the INLET caution light (Figure 2-5). Above Mach 0.9, the No. 3 ramp normally begins programming below the actuator stow lock. When the fail-safe mode is entered above Mach 0.9, the unpowered No. 3 ramp will eventually move and may cause compressor stalls at higher power settings. The aircraft shall be decelerated below 1.2 IMN, and the appropriate INLET RAMPS switch shall be selected to STOW.

 

Anyone looked if RAMPS/INLET caution light or some other warnings are lit during your described events? Maybe for HB too to check the AICS function/scheduling, just and idea.

Edited January 20, 2021 by Golo

[Sideburns]

I was having multiple compressor stall events trying to get through M1.1 last night and I did think it could be a inlet/ramps issues, also read an article last night saying that ramp issues were not uncommon but I thought it would be incredible, perhaps too incredible, for HB to model this.

 

https://www.thedrive.com/the-war-zone/9599/a-tomcat-pilots-early-struggles-to-tame-the-mighty-f-14

"The F-14 had ramps in each engine intake that were hydraulically driven down at high mach numbers to reduce the area of the intake. It turned out that the left ramp intake had incorrectly deployed as we were on our takeoff roll, causing the left engine to enter into a compressor stall and lose thrust. Sucking a ramp down was not a common occurrence with the F-14, and with over 1100 hours in the Tomcat, it only happened to me one time…on my first takeoff roll!"

 

I didn't feel like playing around with ramp switches last night (MP with RIO, didn't want to self destruct) but will give it a try tonight.

[captain_dalan]

We are still talking about the F-14A, right? Shouldn't the inlet ramp really have only two settings on the switch, stow and auto?

[Sideburns]

A quick test of this issue over lunch break indicates to me it may be linked to the ramp scheduling under certain conditions.

 

On a flight to angels 30-35k, going supersonic there were no unsolicited compressor stalls this time but stowing one engine's ramp created issues starting at M1.1, a very similar speed to where most are having issues. I will keep testing tonight to see if I can get a unsolicited compressor stall and observe for ramp issues / activity.

 

Edit: To be clear, prior to M1.1 the ramps don't seem to move much (full open / stow doesn't cause an issue), inlet ramp activity appears to start at M1.0+ in a minor inlet ramp adjustment and begins to be significant at about M1.1. Perhaps the inlet ramps are not opening enough?

Edited January 20, 2021 by Sideburns

[Sideburns]

So holding M1.1 in a slow climb, zone 5 AB, from 32kft to 37kft will result in TIT overtemp and twin engine fire fairly reliably for me, issues becoming evident around 34/35kft as the TIT rises rapidly. Speed has to be M.1.10-M1.12 Sometimes happens with compressor stall warnings, sometimes not.

 

In tests I did this with an unloaded / naked F14a, but I imagine as per prior comments having a loadout may more easily hold the plane at the "magic" M1.10-M1.12 speed as you pass through 34/35kft.

 

Edit: Caucasus map, default weather / pressure conditions. Suspect the variation in this issue might be down to "engine condition variation" between spawns.

Edited January 20, 2021 by Sideburns

[fat creason]

This was a strange one, but it should be fixed in the next patch.

[Skysurfer]

6 minutes ago, fat creason said:

This was a strange one, but it should be fixed in the next patch.

 

Fingers (and toes) crossed. 

[captain_dalan]

3 hours ago, fat creason said:

This was a strange one, but it should be fixed in the next patch.

Good stuff! Hoping for the best!

[Sideburns]

10 hours ago, fat creason said:

This was a strange one, but it should be fixed in the next patch.

 

It is quite gratifying assisting with bug hunting for HB as you are very attentive to issues. Thank you for looking into it. You can bet your last $national_currency that I will be checking this on patch release

[captain_dalan]

I think this should be marked as solved at least for now. The engines didn't blow up for me above angels 35 and i really tried. True, the plane still wouldn't accelerate past mach 1.2 but at least no more fires! YEY!

[IronMike]

Yes, resolved. Thank god.

[Sideburns]

I will keep testing but based on one test flight last night and then some MP sessions looks to be resolved.

[Skysurfer]

Yep, haven't had any obvious issues.