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jgoggi

Engine inflight restart not simulated?

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Kevin, with all due respect, lets break this down logically?  Why would the auto relight fail?  We would need to be missing any of the following or a combination of them - air, fuel, spark.  The most common reason that an engine would not relight would be air.  Air can do a few things to a jet engine at high altitudes which I will explain.  The most obvious and one that Kyle has pointed out to you is the lack of oxygen up in the wild blue yonder.  Secondly, air; in this case speed, can hamper your attempts to do a "windmill" restart if you do not have supplementary air (APU) available.  Thirdly - core lock.  Core lock is a situation in which an engine is shut down for too long a period and the internal components actually shrink because the air is not circulating thought the engine correctly.  The end result is bad and it seizes the engine - locking its core so it will not turn - hence the term core lock.  This is not something I am making up and I do believe that I read in an NTSB report that this was a cause of a crash in the US - I believe on an RJ?

 

I do wonder if the condition you are experiencing (or lack there of) is actually a cross bleed start that is relighting your engines.  When the N2 drops below idle RPM while airborne.  The next time you do this shutdown, see if you get the secondary engine indications and a crossbleed start indication.

 

Were you aware that auto-relight actually provides flameout protection by turning on both engines ignitors?    

 

Another point that I would like to point out is that we are talking about a desktop simulation and a Level D full motion simulator.  HUGE difference - TRUST ME.  The desktop simulator is just that - a great representation of a 777 or 737 (or whatever) with some very accurate modeling of systems and functions contained within built to give you a sense of what it is like to fly a 777.  This is not a multi million dollar piece of training equipment that you are going to be able to throw every failure known to man at.

 

While I have never sat at the console and controlled the simulator (Level D), I can tell you that being on the receiving end of some of he failures I have had thrown at me is not fun (that's a lie, it is fun - just not at that moment).

 

Kevin, I will close by offering a suggestion to you sir.  Rather that spin up two posts in two separate PMDG product forums, perhaps submit a support ticked and mark it as a feature request.  The people at PMDG are good people and respond kindly to these things.  There really is no need to spin up two topics in two forums now is there?

 

DR

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Kevin, your thought is 100% aligned with mine  :wink:

 

Dave, I know that a desktop simulator can't be compared to a Level D, but I think that, after all the failures that have been included in the PMDG airplanes, the failure that includes the possibility to do an inlight restart is not at a much higher level than the other failures, and as such it's a 'feature' that is missing.

 

If you have the 737 NGX and FS2Crew and look at FS2Crew Emergency documentation, the last lines of the engine failure procedure are:

"3. PF Consider running the ENGINE IN FLIGHT START checklist.

4. PF If the engine cannot be restarted: run the ONE ENGINE INOPERATIVE LANDING CHECKLIST FLAPS 15 or ONE ENGINE INOPERATIVE CHECKLIST FLAPS 30",
therefore Bryan York, when programming it, supposed that there was a chance that the engine could be restarted and did not imagine that this can't be accomplished in the NGX.

James Goggi

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Guess we need one of  the Devs  from pmdg to step in and confirm one way or  the other, if  this is possible or  not or  can it be added  in the next update.


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Peter kelberg

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Kevin, with all due respect, lets break this down logically? Why would the auto relight fail? We would need to be missing any of the following or a combination of them - air, fuel, spark. The most common reason that an engine would not relight would be air. Air can do a few things to a jet engine at high altitudes which I will explain. The most obvious and one that Kyle has pointed out to you is the lack of oxygen up in the wild blue yonder. Secondly, air; in this case speed, can hamper your attempts to do a "windmill" restart if you do not have supplementary air (APU) available. Thirdly - core lock. Core lock is a situation in which an engine is shut down for too long a period and the internal components actually shrink because the air is not circulating thought the engine correctly. The end result is bad and it seizes the engine - locking its core so it will not turn - hence the term core lock. This is not something I am making up and I do believe that I read in an NTSB report that this was a cause of a crash in the US - I believe on an RJ?

You mentioned three things: air, fuel and spark. All are required for a relight. Spark we assume to be available for relight. You discussed air but not fuel. However the important thing is what causes the flameout in the first place and whether that condition lasts long enough to prevent auto ignition from relighting the engine until N2 falls too low for it to work.

 

The current flameout failure doesn't define the cause it just momentarily kills the combustion process. That means auto relight always works. A second flameout type could be defined that prevents an immediate relight. Everyone would be happy.

 

Core lock isn't particularly relevant to this discussion. PMDG don't appear to model it and it would only apply if the engine was windmilling for a long period.

 

I do wonder if the condition you are experiencing (or lack there of) is actually a cross bleed start that is relighting your engines. When the N2 drops below idle RPM while airborne. The next time you do this shutdown, see if you get the secondary engine indications and a crossbleed start indication.

I do know the difference between a crossbleed and a windmilling start thanks. Also why they are used. But at very high altitudes with the thin air you were talking about, neither method ought to work.

 

I was at 40,000 ft. I tried both the flameout malfunction and a manual shutdown. The flameout auto relit and the manual restart succeeded (when manually shutdown it indicated a crossbleed start would be necessary). If 40,000 ft is within the relight envelope that's fine, but if it isn't you should have to descend to get the engine started.

 

Were you aware that auto-relight actually provides flameout protection by turning on both engines ignitors?

Yes I was aware thank you. As I was aware of all the other things you've informed us about in this thread too.

 

Another point that I would like to point out is that we are talking about a desktop simulation and a Level D full motion simulator. HUGE difference - TRUST ME. The desktop simulator is just that - a great representation of a 777 or 737 (or whatever) with some very accurate modeling of systems and functions contained within built to give you a sense of what it is like to fly a 777. This is not a multi million dollar piece of training equipment that you are going to be able to throw every failure known to man at.

 

While I have never sat at the console and controlled the simulator (Level D), I can tell you that being on the receiving end of some of he failures I have had thrown at me is not fun (that's a lie, it is fun - just not at that moment).

I've spent my entire professional career designing, integrating, testing and updating Full Flight Simulator software, including many engines simulations. I've probably been in more Level D sims than you have and I certainly know more about how they work than you do. Adding another flameout failure mode to the PMDG 777 would not be a big deal. It could use a time delay or simply inhibit relight until cancelled. It might not be high on the priority list of course.

 

BTW, I have controlled a FFS from the instructor station, as well as designing malfunction logic in the simulation so I know the options available.

 

Kevin, I will close by offering a suggestion to you sir. Rather that spin up two posts in two separate PMDG product forums, perhaps submit a support ticked and mark it as a feature request. The people at PMDG are good people and respond kindly to these things. There really is no need to spin up two topics in two forums now is there?

 

DR

I will offer a suggestion to you, sir. Check who opened these threads before throwing advice at me. I've only contributed to this thread. I didn't start either of them.

 

You might want to read the comments by two 737 pilots in the equivalent NGX thread. Their input is less condescending.


ki9cAAb.jpg

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Sorry you felt that was condescending Kevin. Wasn't the intent. Valid point you raise. One really isn't sure the level of experience of the poster so sorry again. We have such a mix of ages in here one never knows

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Core lock is a situation in which an engine is shut down for too long a period and the internal components actually shrink because the air is not circulating thought the engine correctly.  The end result is bad and it seizes the engine - locking its core so it will not turn - hence the term core lock.  This is not something I am making up and I do believe that I read in an NTSB report that this was a cause of a crash in the US - I believe on an RJ?

 

Got it a little backwards there. Core lock happens because the internal components stay hot - without the air passing through the engine, and the engine core still being very hot from running - while the external (or closer to external) components change in size at different rates. Regardless, you're correct that locking the core is going to be unrecoverable.

 

The crash you're referring to is FLG3701.


Kyle Rodgers

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Just to confirm, during our real world sim sessions we often have an engine failure with no apparant damage (engine just spools down).

Thinking about it......I think there is an exercise like that in every sim check.

 

We then go through the Engine Fail L/R checklist including the restart part.

 

They probably make us do this exercise in the sim so often so that we get into the habit of trying to restart an engine rather then automatically saying "oh that is gone see ya later bye" and not even try.

 

Autorelight only lights up the igniters if the system dected an unexpected engine spool down. This is not the same as an EEC reset which is done by fuel control switches off, then on.

Fuel flow for example might have been interupted which maybe is restored after fuel control switch off, then on.....but not by lighting the ignitors (autostart).

 

So the only thing to simulate a flameout condition in the PMDG at the moment is by simply putting the fuel control switch off (I have linked key presses to this action via the CDU).


Rob Robson

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By the way......the system that "Autostarts" the engine inflight is the AUTO RELIGHT system.

It only turns on the ignitors (and in case of a subidle stall interupts fuel flow for one second.)

 

This is not the Autostart system!

 

The AUtOSTART system can only be activated by:

on gnd - start selector START + fuel control switch to RUN.

in flight - fuel control switch to RUN.


Rob Robson

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If what the OP says is true, that with the AUTOSTART switches off the engines do not automatically restart inflight, then I think PMDG has simulated the AUTOSTART system and the AUTORELIGHT system to be one and the same.

 

Which it is not, as far as I understand things.

 

(I have not yet gone through maintenence manuals, but the MEL says nothing of AUTORELIGHT not working if the AUTOSTART system is dispatched inop.)

 

So all that need be done then is program things so that an inflight engine failure is simulated by a fuel interruption plus the AUTOSTART system not kicking in automatically.

 

The AUTSTART system should then still work for an inflight engine start when the fuel control switch is turned off/on........meaning it will monitor the start and adjust things (or abort the start on gnd) as required for a succesfull start (that is really all AUTOSTART is)


Rob Robson

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Look at this video featuring FSiPanel: here they manage to get an engine failure where N1 does not go to zero and there is no auto relight! The video description on Youtube says that the failure is "V1 CUT", but when I select V1 CUT on the CDU it always triggers a severe engine failure, with all parameters going to zero! This one is set from the FSiPanel window, not from the CDU, but what's the difference??

 


James Goggi

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This one is set from the FSiPanel window, not from the CDU, but what's the difference

 

 

Most likely he  didn't  show  you setting  the failure  in the cdu    since he  does mentions it  at   5.07  min mark, anyways  I tried it myself  and got the same results as you  n1   goes  straight  to zero unlike  the video   in your link


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Peter kelberg

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I tried it myself  and got the same results as you  n1   goes  straight  to zero unlike  the video   in your link

 

Thank you! It's also strange that, through FSiPanel, you can make the engine fail at any speed you want. Any developer can shed some light on this? Thanks!


James Goggi

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Thank you! It's also strange that, through FSiPanel, you can make the engine fail at any speed you want. Any developer can shed some light on this? Thanks!

Making it fail at a specific speed shouldn't be that difficult. (One could read the current airspeed via Simconnect or FSUIPC for example.) Have you tried failing the engine in the FSX menu (Aircraft -> failures, engine tab -> Complete failure)? I just tried it and from what I can see that replicates the behavior from the FSiPanel video. (N1 rotation, but no Auto-relight).

Hope this helps,

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Making it fail at a specific speed shouldn't be that difficult. (One could read the current airspeed via Simconnect or FSUIPC for example.) Have you tried failing the engine in the FSX menu (Aircraft -> failures, engine tab -> Complete failure)? I just tried it and from what I can see that replicates the behavior from the FSiPanel video. (N1 rotation, but no Auto-relight).

Hope this helps,

That's a great spot. It does fail the engine as you describe. This could mean everyone is happy without any updates needed.


ki9cAAb.jpg

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That's a great spot. It does fail the engine as you describe. This could mean everyone is happy without any updates needed.

I quickly wrote a little program in C# where you can specify a speed that you want an engine to fail at (communicates via FSUIPC) and it actually works great. :)

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