Jump to content

[MIND THE NEGATIVE G] A-10C II engines shut down during a dive in sharp angle.


Adamastor
 Share

Recommended Posts

During a dive attack at a very sharp angle (50/60), the aircraft shut down completely. I still managed to get an engine running, but in the middle of the Caucasus mountains it was impossible to recover.
Does anyone know what can it be?
I recognize that what I did is not supposed to happen in RL, but as I had altitude and a good position for a target, I decided to go ahead.

My initial altitude was 20000 feet and the target was around 5000 feet.
Could it be due to being at high altitude, the rarefied air causing the engines to collapse?

Link to comment
Share on other sites

2 hours ago, Yurgon said:

What was your throttle setting?

 

In a deep dive (or rather: at high airspeed) with the throttles near idle power, the engines can flame out.

 

Add more power and you should be good.


they absolutely should not, for a dive bomb of 45 degrees or higher you pull the throttles back to idle.  That’s per real world TTPs.

 

I have never experienced this issue in DCS though.

  • Like 1
Link to comment
Share on other sites

1 hour ago, Snoopy said:

I have never experienced this issue in DCS though.

 

Good to know!

 

I had this happen to me once, and it was maybe two years ago. There were some reports here on the forum of people who had the same experience, but it doesn't seem to happen very often. I never took the time to figure out the exact limits in DCS.

  • Like 1
Link to comment
Share on other sites

52 minutes ago, Mike Busutil said:

Pushing negative G's to get into the dive?

 

Negative G for long enough would snuff out both engines. IIRC 10 seconds at max power is the limit before the collector tanks at the engines go dry.

  • Like 1

Aircraft: A-10A, F-15C, A-10C, A-10C II, F-14, F-16C, F/A-18C, AH-64, UH-1H, P-47, P-51D, Bf-109, DH Mosquito

Modules: Super Carrier, NTTR, Persian Gulf, WWII Assets

PC: MSI 990FXA Gaming, FX-8120 3.1 GHz, 32GB Patriot Viper RAM, GTX980 4GB, 27" 1080p curved Samsung monitor, TM Warthog HOTAS, Saitek Pro Flight pedals, Opentrack

 

Link to comment
Share on other sites

I was one who experienced this in the Hog-1.

 

Aggressive maneuvering into a dive to spoof an SA-8 shut down one engine and knocked several other systems offline including making my INS go stupid.  Had this happen on two separate occasions.

 

At no time did I put negative Gs on the jet.  
ie, I did not “push” into the dive.  Now rolling hard into the dive may have put negative Gs on one engine, but I do not recall if the engine that quit on me was on the outside of the maneuver or the inside.  I’m positive it would not have been of a sufficient duration to snuff an engine.

 

Just one of those things I guess.  I’ve never been able to reproduce it intentionally.


Edited by Emmy
  • Like 1

[sIGPIC][/sIGPIC]

http://www.476vfightergroup.com/content.php

High Quality Aviation Photography For Personal Enjoyment And Editorial Use.

www.crosswindimages.com

Link to comment
Share on other sites

4 hours ago, Mike Busutil said:

Pushing negative G's to get into the dive?

 

That would be my suspicion too, althoguh that must have been one incredible weird parabolic flight pattern to push the aircraft into the dive.

I fly the DCS Warthog for almost 10 years now and have never experienced that. The only engine flameouts I experienced came from flying inverted or battle damage.


Edited by QuiGon
  • Like 1

Intel i7-4790K @ 4x4GHz + 16 GB DDR3 RAM + Nvidia Geforce RTX 2080 (8 GB VRAM) + M.2 SSD + Windows 10 64Bit

 

DCS Panavia Tornado (IDS) really needs to be a thing!

 

Tornado3 small.jpg

Link to comment
Share on other sites

If I make online this week @Adamastor will try to see if I can replicate, during training if you wish.

  • Like 1

Pointy end hurt! Fire burn!!
JTF-191 25th Draggins - Hawg Main. Black Shark 2, A10C, A10CII, F-16, F/A-18, F-86, Mig-15, Mig-19, Mig-21, P-51, F-15, Su-27, Su-33, Mig-29, FW-190 Dora, Anton, BF 109, Mossie, Normandy, Caucasus, NTTR, Persian Gulf, Channel, Syria, Marianas, WWII Assets, CA. (WWII backer picked aircraft ME-262, P-47D).

Link to comment
Share on other sites

I've had this happen 4 times recently (within the last update and hotfix).  Couldn't tell you the exact parameters on the scenario - but a high nose down dive was being performed.  Resulted in both engines but they were able to restart with procedure.

 

 

Cheers,

 

Ziptie 

  • Like 1

i7 6700 @4ghz, 32GB HyperX Fury ddr4-2133 ram, GTX980, Oculus Rift CV1, 2x1TB SSD drives (one solely for DCS OpenBeta standalone) Thrustmaster Warthog HOTAS, Thrustmaster Cougar MFDs

 

Airframes: A10C, A10CII, F/A-18C, F-14B, F-16C, UH=1H, FC3. Modules: Combined Arms, Supercarrier. Terrains: Persian Gulf, Nevada NTTR, Syria

Link to comment
Share on other sites

Gentleman, thanks a lot for your thoughts. I see here some good experienced pilots.

I go for the negative G's probability.

Yesterday I tried to replicate the situation over, and over, and no joy, my A10 was still strong as a Hog and no engine shut down.

As I say above, I could restart them, but as consequence of the dive i was low and surrounded by mountains, so I had to eject.

I thing I got in Tackview the exact moment the engines shut down, and in telemetry it says -0 G ... in movement is compreensible I did some wing shake (was my 1st reaction). Also noted the angle wasn't that sharp after all.

I confess i'm not a expert interpreting telemetry, so, if someone see something that expain the issue, please step forward.

Thank you1701793138_Shuttelemetry.thumb.png.d63583929d8ab418b5b28c7663de2887.png


Edited by Adamastor
error
  • Like 1
Link to comment
Share on other sites

51 minutes ago, Adamastor said:

I go for the negative G's probability.

 

The flight path looks like an initial push, followed by a lengthy and steep dive. We'd have to see the full TacView, but it doesn't look like you've been at or below 0 g for a prolonged time.

 

Checking the airspeed, you're at 389 KIAS near 9000 feet. I'd still guess it's a dual engine flame-out due to high airspeed with throttles near idle.

 

If I find the time, I'll do some tests and report a bug if it turns out to be reproducible.

  • Like 1
Link to comment
Share on other sites

I had this happen to me a decade ago, when I started with the A-10C. Very similar setup, long dive, trying to keep the nose on target and inadvertently dried out the feed tanks... 0G means no gravity pulling the fuel down. If this happens for over 10 sec. Your engines can run dry.

A gentle push on the stick to keep the nose from rising produces enough constant G forces below .5 G to give you trouble.

I learned to trim before I roll into the dive and keep the TVV below the target and keep a constant slight pull on the stick.

  • Like 1

Shagrat

 

- Flying Sims since 1984 -:pilotfly:

Win 10 | i5 10600K@4.1GHz | 32GB | GeForce RTX 2080S - Acer XB280HK 28" 4k | TrackIR5 | Simshaker & Jetseat | VIRPIL CM 50 Stick & Throttle | MFG Crosswind Rudder Pedals | TM Cougar MFDs | a hand made UFC | AHCP | 2x Elgato StreamDeck (Buttons galore)

Link to comment
Share on other sites

3 hours ago, Yurgon said:

 

The flight path looks like an initial push, followed by a lengthy and steep dive. We'd have to see the full TacView, but it doesn't look like you've been at or below 0 g for a prolonged time.

 

Checking the airspeed, you're at 389 KIAS near 9000 feet. I'd still guess it's a dual engine flame-out due to high airspeed with throttles near idle.

 

If I find the time, I'll do some tests and report a bug if it turns out to be reproducible.

Thanks. I can send you the Tackview file if it help's.

Honestly, I'm temped to believe it was something wrong I did. When I realise I was almost depassing the target I pulled hard the stick and had that feeling ... "I shouln't be doing this" ... 😅

Just had a look again in Tackview, and realise that in the beginning of the dive I was in negative G's for a few seconds (around 5).704967225_Shuttelemetryinit.thumb.png.b53344998fc6683904fdc828276354b9.png

Link to comment
Share on other sites

On 12/2/2020 at 7:21 PM, Adamastor said:

Gentleman, thanks a lot for your thoughts. I see here some good experienced pilots.

I go for the negative G's probability.

Yesterday I tried to replicate the situation over, and over, and no joy, my A10 was still strong as a Hog and no engine shut down.

As I say above, I could restart them, but as consequence of the dive i was low and surrounded by mountains, so I had to eject.

I thing I got in Tackview the exact moment the engines shut down, and in telemetry it says -0 G ... in movement is compreensible I did some wing shake (was my 1st reaction). Also noted the angle wasn't that sharp after all.

I confess i'm not a expert interpreting telemetry, so, if someone see something that expain the issue, please step forward.

Thank you1701793138_Shuttelemetry.thumb.png.d63583929d8ab418b5b28c7663de2887.png

 

Yeah, that looks like a 0 or even negative G maneuver, that might have drained the feed tanks. That's why you should always avoid pushing the nose down and instead roll over and pull on the stick in order to get the nose down with positive Gs. I guess you're not flying the MiG-21bis, because this thing will definitely teach you that, as it is absolutly unforgiving if you put <=0G on it!


Edited by QuiGon
  • Like 1

Intel i7-4790K @ 4x4GHz + 16 GB DDR3 RAM + Nvidia Geforce RTX 2080 (8 GB VRAM) + M.2 SSD + Windows 10 64Bit

 

DCS Panavia Tornado (IDS) really needs to be a thing!

 

Tornado3 small.jpg

Link to comment
Share on other sites

3 hours ago, QuiGon said:

 

Yeah, that looks like a 0 or even negative G maneuver, that might have drained the feed tanks. That's why you should always avoid pushing the nose down and instead roll over and pull on the stick in order to get the nose down with positive Gs. I guess you're not flying the MiG-21bis, because this thing will definitely teach you that, as it is absolutly unforgiving if you put <1G on it!

That is good learning. Thanks a lot. I fly exclusively A10 for 3 years and never had the "pain" of flying russian aircrafts. 

That's why I stay on only 1, always learning something. Cheers.

  • Like 1
Link to comment
Share on other sites

21 hours ago, Adamastor said:

Here it is a link for the file in one drive (it is bigger than 5MB). If possible i would like to have the feedback. Thanks

 

Hey, thanks for the TacView.

 

What on earth were those F-117 doing right after take-off?! Anyone up for some hilarity, have a look at the AI at mission start. 🤣

 

Now, back to the topic at hand:

 

Capture-2020-12-04-001.thumb.jpg.7f2ee2a5712661e8f137480af9b1fea2.jpg

 

The initial dive took several seconds of zero g. I count exactly 10 seconds from 0.5 g, with a lowest g of -0.3, until 0.5 g again.

 

But then it took almost 25 seconds of 1 g flight, while shooting APKWS and the gun, until the problem appeared; when the engines flame out, the generators go down with them, so unless you had the APU on during the entire battle, I'm pretty sure the engines didn't flame out from the initial dive, even though it might have taken you fairly close to the limit of a maximum of 10 seconds with negative g loads.

 

Capture-2020-12-04-002.thumb.jpg.416e1f381793786fab65276e50c9635c.jpg

 

Considering all that, it still seems like a flame-out from high airspeed with a low throttle setting.

 

In a quick test yesterday I was also able to get an engine to flame out in an idle-throttle dive at an airspeed above 400 KIAS (but I was actually above Vne during the dive).

 

Looks like DCS just doesn't like this type of dive.

 

In any case, like others said before, you should really roll inverted before going into such a dive to avoid negative g. For an actual pilot, positive g loads are also more comfortable than negative ones. But I don't see an obvious connection between the 0 g initial dive and the engine flame-out in the TacView.


Edited by Yurgon
  • Thanks 1
Link to comment
Share on other sites

18 hours ago, Yurgon said:

 

Hey, thanks for the TacView.

 

What on earth were those F-117 doing right after take-off?! Anyone up for some hilarity, have a look at the AI at mission start. 🤣

 

Now, back to the topic at hand:

 

Capture-2020-12-04-001.thumb.jpg.7f2ee2a5712661e8f137480af9b1fea2.jpg

 

The initial dive took several seconds of zero g. I count exactly 10 seconds from 0.5 g, with a lowest g of -0.3, until 0.5 g again.

 

But then it took almost 25 seconds of 1 g flight, while shooting APKWS and the gun, until the problem appeared; when the engines flame out, the generators go down with them, so unless you had the APU on during the entire battle, I'm pretty sure the engines didn't flame out from the initial dive, even though it might have taken you fairly close to the limit of a maximum of 10 seconds with negative g loads.

 

Capture-2020-12-04-002.thumb.jpg.416e1f381793786fab65276e50c9635c.jpg

 

Considering all that, it still seems like a flame-out from high airspeed with a low throttle setting.

 

In a quick test yesterday I was also able to get an engine to flame out in an idle-throttle dive at an airspeed above 400 KIAS (but I was actually above Vne during the dive).

 

Looks like DCS just doesn't like this type of dive.

 

In any case, like others said before, you should really roll inverted before going into such a dive to avoid negative g. For an actual pilot, positive g loads are also more comfortable than negative ones. But I don't see an obvious connection between the 0 g initial dive and the engine flame-out in the TacView.

I saw the F117 "dance" from the cockpit ... is so cool I will let them stay for entretaining purposes 🤣

Well, I always do cold start .... I like the sound from the APU .... I wonder if ..... 

Any way, thanks a lot for all your interest and help. Like I say above. Have learned something new with this situation, I always roll inverted now and understand a bit more about A10 procedures in flight.

Cheers

 

Link to comment
Share on other sites

May I bring up 2 more ideas:

 

 

1:

It is possible at high speeds and high thrust settings that the local speed of sound is reached at the engines, eventhough the aircraft itself is well below sonic speed. This could cause a disruption of airflow, that might cause a compressor stall.

A drop in local speed of sound could be caused by a drop in temperature due to venturi in front of the compressor stage / intake. This drop in temperature causes a rise of the local mach number. If the air in front of the engine now reaches sonic speed, a shockwave is formed that might disrupt the airflow and could cause flameout or damage to the engine.

 

2:

Another idea would be that the critical mach number at the tips of the fan blades was reached. This could also cause a compressor stall and/or critical damage to the fan blades, and the entire engine.

 

 

These are just my 2ct - I do not have any real-life manuals of the A-10C available that could support my theory.

 

Also note that you are quite close to the max mach number for the A-10. You are (according to the TACVIEW pictures) doing M0.72 while the maximum is M0.75.

 

 


Edited by atomtomgo
Link to comment
Share on other sites

You know, I've had this happen to me once or twice years ago. Steep high altitude dive with idle throttles, didn't go negative G, engines flamed out.

Intel 9600K@4.9GHz, Asus Z390, 32GB DDR4 2400MHz, EVGA GTX 1070, Custom Water Cooling, 970 EVO 500GB NVMe, 2TB of Mechanical Storage

 

34" UltraWide 3440x1440 Curved Monitor, 21" MFD monitor, TIR5

 

My Pit Build, VKB Gunfighter Pro w/WH Grip, TMWH Throttle, MFG Crosswinds W/Combat Pedals, Cougar MFDs, Custom A-10C panels, Custom Helo Collective, SimShaker with Transducer

Link to comment
Share on other sites

  • Wags changed the title to [MIND THE NEGATIVE G] A-10C II engines shut down during a dive in sharp angle.
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...