Engine Lockout

[kgillers3]

3 hours ago, gnomechild said:

Sounds like the true purpose of the lockout is for maintaining control when the auto control becomes too self aware. Real Apache pilots won't say it because it's classified but there's actually nobody in the front seat. It's always been George9000 

Damnit! Someone lied to me. 

[heloguy]

Well, despite theories of why you would go to lockout, lightspeed included, I'm only curious if it will be modeled.  By no means was I talking about using it on a regular basis.  Only in the emergencies it's prescribed for.

[heloguy]

13 hours ago, kgillers3 said:

I enjoy these speculations on what lockout does and how it helps 

Mechanically bypass the torque motor inputs and control the engine manually?

[shagrat]

vor 13 Stunden schrieb kgillers3:

Lol, That’s what peeps are going to think about their np section before it shuts down the first time they do lockout

 

Yeah, just read the section... so Lockout gives you manual control over the engine in case the ECU/DEC has problems, but overspeed protection will then kill the engine for you, if you exceed max Np, right?

So, in Lockout you need to carefully monitor the TGT and Np while in normal ops the ECU/DEC adapt the engine performance to give you everything you need, based on collective settings, as long as you're not getting close to tripping the overspeed protection?

[Raptor9]

1 hour ago, shagrat said:

Yeah, just read the section... so Lockout gives you manual control over the engine in case the ECU/DEC has problems, but overspeed protection will then kill the engine for you, if you exceed max Np, right?

So, in Lockout you need to carefully monitor the TGT and Np while in normal ops the ECU/DEC adapt the engine performance to give you everything you need, based on collective settings, as long as you're not getting close to tripping the overspeed protection?

Np/Power Turbine overspeed protection is performed electronically by the ECU/DECU, so when in Lockout this function is unavailable. However, the HMU (fuel control) has a mechanical overspeed protection for when the Ng/Gas Producer section accelerates. This is what will kill the engine, permanently, until the fuel control is replaced.

To sort of summarize the discussions that have taken place in the thread...(not directed at Shagrat, but everyone)

When a helo's rotor RPMs decay (also called "drooping"), this is from the engine thrust into transmission becoming unable to overcome the drag on the rotor system. This could be from a loss in engine power or from the pilot pulling up on the collective to an extent the blade pitch produces too much drag. When this occurs, the corrective action is to reduce the collective until the rotor RPMs are back within their intended operating range for flight. For every RPM you lose from the rotor system, you lose exponentially more lift. Airflow over the blades is more important, and will have a much greater negative impact on flying than any positive effects from increased blade pitch. Essentially what is happening is like a fixed wing plane going into a steep climb, with inadequate engine power to maintain forward airspeed, and begins to stall; the corrective action is to push the nose down to regain airspeed, not keep pulling back on the controls to attempt to maintain altitude.

If you have put yourself into a situation where you need more power than what you engine is intended to provide in order to prevent rotor RPM decay, the last thing you want to do in that situation is switch to a manual engine control. Whether you attempt to do this while controlling the collective and the power levers at the same time, or have the other crewmember do it, the most likely outcome is the engine (or both if locking out both engines) will overspeed within seconds and shut down, or if the crewmember catches it and attempts to control it manually, he will exacerbate the rotor RPM decay condition by unintentionally retarding the power lever a little too much.

Lockout is a last ditch effort to control an engine due to ECU/DECU malfunctioning and causing abnormal underspeeding outside normal engine parameters. When it's used for purposes other than that, such as to compensate for poor piloting technique, the crew is needlessly compounding the problems they are experiencing. (In fact, if the aircraft is capable of flying under single-engine power, it may be prudent to return to base under the reduced power available than attempting Lockout. But that is a call to made by the crew based on all applicable factors.) On the surface, using Lockout to gain more power by removing the computer managing the engine seems like a solid concept, but in reality it is a fool's attempt that will most assuredly bring about the same fate one is trying to avoid.

Edited November 5, 2021 by Raptor9

[shagrat]

vor 57 Minuten schrieb Raptor9:

Np/Power Turbine overspeed protection is performed electronically by the ECU/DECU, so when in Lockout this function is unavailable. However, the HMU (fuel control) has a mechanical overspeed protection for when the Ng/Gas Producer section accelerates. This is what will kill the engine, permanently, until the fuel control is replaced.

To sort of summarize the discussions that have taken place in the thread...(not directed at Shagrat, but everyone)

When a helo's rotor RPMs decay (also called "drooping"), this is from the engine thrust into transmission becoming unable to overcome the drag on the rotor system. This could be from a loss in engine power or from the pilot pulling up on the collective to an extent the blade pitch produces too much drag. When this occurs, the corrective action is to reduce the collective until the rotor RPMs are back within their intended operating range for flight. For every RPM you lose from the rotor system, you lose exponentially more lift. Airflow over the blades is more important, and will have a much greater negative impact on flying than any positive effects from increased blade pitch. Essentially what is happening is like a fixed wing plane going into a steep climb, with inadequate engine power to maintain forward airspeed, and begins to stall; the corrective action is to push the nose down to regain airspeed, not keep pulling back on the controls to attempt to maintain altitude.

If you have put yourself into a situation where you need more power than what you engine is intended to provide in order to prevent rotor RPM decay, the last thing you want to do in that situation is switch to a manual engine control. Whether you attempt to do this while controlling the collective and the power levers at the same time, or have the other crewmember do it, the most likely outcome is the engine (or both if locking out both engines) will overspeed within seconds and shut down, or if the crewmember catches it and attempts to control it manually, he will exacerbate the rotor RPM decay condition by unintentionally retarding the power lever a little too much.

Lockout is a last ditch effort to control an engine due to ECU/DECU malfunctioning and causing abnormal underspeeding outside normal engine parameters. When it's used for purposes other than that, such as to compensate for poor piloting technique, the crew is needlessly compounding the problems they are experiencing. (In fact, if the aircraft is capable of flying under single-engine power, it may be prudent to return to base under the reduced power available than attempting Lockout. But that is a call to made by the crew based on all applicable factors.) On the surface, using Lockout to gain more power by removing the computer managing the engine seems like a solid concept, but in reality it is a fool's attempt that will most assuredly bring about the same fate one is trying to avoid.

 

Very good and in depth explanation. Thanks for taking the time to post this.

[kgillers3]

13 hours ago, heloguy said:

Mechanically bypass the torque motor inputs and control the engine manually?

No. Basically @Raptor9 explained it better. It’s electronic. But it disables the electronic governor. But they way it’s designed is to provide the most power the engine has anyways so if you’re trying to manually do it you might be able to get a little out of the top end but your margin is super narrow. You’re well in the tgt area where the engine could potentially die out on you mechanically and if you don’t check it the rotor and engine will runaway to a overspeed protection. It’s purpose is if the electronic governor failed low. Setting the engine at a low power setting. I’m going to give two examples. Your oge limited and your at max power input or the engine as designed hovering and keep pulling collective the rotor will droop. So you go to lock out yes you can get some out of it there.  Second scenario your drooping because your trying to avoid a crash. You go to lock out. You get nothing. Also this is only if your tgt limited. If your limited cold section it doesn’t matter. Sorry for poor grammar. 
 

I highly encourage people to play with it. And I want to click it on while someone’s flying to see what they do. But it’s not a recovery technique trying to arrest a crash. The engines give you what they got anyways. Combining it with tq, you can easily over tq without going lockout. 

[Raptor9]

What I think he meant was the torque motor on the HMU. The HMU torque motor is how the ECU/DECU applies electronic fuel flow adjustments to the HMU which is a mechanical device. Therefore if you "Lock out" the ECU/DECU from affecting the fuel flow from the HMU, you are mechanically bypassing those electronic signals from adjusting fuel flow.

[Sarge55]

So... after reading all this my "take away" is I'm not wasting a HOTAS switch for this and don't fly like you stole it. 

Thanks for the explanation guys.

[heloguy]

2 hours ago, kgillers3 said:

No. Basically @Raptor9 explained it better. It’s electronic. But it disables the electronic governor. But they way it’s designed is to provide the most power the engine has anyways so if you’re trying to manually do it you might be able to get a little out of the top end but your margin is super narrow. You’re well in the tgt area where the engine could potentially die out on you mechanically and if you don’t check it the rotor and engine will runaway to a overspeed protection. It’s purpose is if the electronic governor failed low. Setting the engine at a low power setting. I’m going to give two examples. Your oge limited and your at max power input or the engine as designed hovering and keep pulling collective the rotor will droop. So you go to lock out yes you can get some out of it there.  Second scenario your drooping because your trying to avoid a crash. You go to lock out. You get nothing. Also this is only if your tgt limited. If your limited cold section it doesn’t matter. Sorry for poor grammar. 
 

I highly encourage people to play with it. And I want to click it on while someone’s flying to see what they do. But it’s not a recovery technique trying to arrest a crash. The engines give you what they got anyways. Combining it with tq, you can easily over tq without going lockout. 

Actually, yeah, it does.   Unless something has changed with 701s.   Lockout is a mechanical bypass as Raptor explained.

[kgillers3]

1 hour ago, heloguy said:

Actually, yeah, it does.   Unless something has changed with 701s.   Lockout is a mechanical bypass as Raptor explained.

*sigh* however you want to look at it. You still have mechanical control even before you go into lock out, but lockout is disabling the decus load sharing and tq matching and tgt limiting (governing) electrically. But yea. You’re right everything does end up being mechanical because. Well it’s a mechanical peace of equipment. 

[kgillers3]

Actually thinking about it I think load sharing and tq matching is still going which is why the other engine dumps tq. Could be wrong idk. But either way. PL to lock out from the spindle the decu gets a signal to stop controlling and all fuel flow into the engine is manually controlled. Minutiae. 

Edited November 5, 2021 by kgillers3

[FalcoGer]

So lockout when DECU fails, otherwise don't touch because bad things will happen, which may include but are not limited to: equipment damage, injury, death, humiliation, being yelled at, soiling your underwear, collateral damage as you land on a cow (apparently the USAF accidentally dropped a nuke on a cow once during transport for maintenance), engine failure, power train failure and/or generating a $20 million heap of scrap which may or may not contain hazardous materials.

Edited November 6, 2021 by FalcoGer

[barundus]

A bit of a departure in the Apache forum, but perhaps a good place to talk about the design philosophy differences between the GE engines that went into the Blackhawk and Apache, and the Rolls Royce/Allison engine that powered the KW.  

I've always had real heartburn about the "save the engine" design philosophy in the GE.  Limiting RPMs when TGTs are approaching limits (acknowledged mostly due to pilot error to end up in the situations in the first-place), or limiting performance in truly life-threating dynamic situations, is such an "engineer-centric" versus "pilot-centric" design approach.  

Contrasted with this, the FADEC in the Rolls Royce/Allison in the 58D featured "limit override logic", which, when triggered, opened the flood-gates and removed all the normal nannies and performance-limiting algorithms and replaced them with absolute engine-limit gates that torched the engine, but the pilot got everything those little gerbils in the hot-section could crank out. 

In normal operation, FADEC provides all the same goodies the DECU/EDECU does on the GE 701s.  But when that "oh shit" moment comes, the designers provided a life-saving mechanism I appreciated from the pilot standpoint.  

Limit override required a number of criteria to be matched to trigger (Nr drooped below 93% or even *approaching* 93% at a certain rate, collective moving at a certain rate, etc),  which then removed the normal inhibitors and allowed the pilot to tap-into more juice to get out of that sticky situation.  

Limit-override was only available in the AUTO mode, so if the FADEC failed, the pilot still had to go to MANUAL mode, which is essentially the same as placing the 701s in LOCKOUT.  

Anyhoo, interesting discussion.

Edited November 6, 2021 by barundus

[heloguy]

3 hours ago, barundus said:

A bit of a departure in the Apache forum, but perhaps a good place to talk about the design philosophy differences between the GE engines that went into the Blackhawk and Apache, and the Rolls Royce/Allison engine that powered the KW.  

I've always had real heartburn about the "save the engine" design philosophy in the GE.  Limiting RPMs when TGTs are approaching limits (acknowledged mostly due to pilot error to end up in the situations in the first-place), or limiting performance in truly life-threating dynamic situations, is such an "engineer-centric" versus "pilot-centric" design approach.  

Contrasted with this, the Rolls Royce/Allison in the 58D FADEC featured "limit override logic", which, when triggered, opened the flood-gates and removed all the normal nannies and performance-limiting algorithms and replaced them with absolute engine-limit gates that torched the engine, but the pilot got everything those little gerbils in the hot-section could crank out. 

In normal operation, FADEC provides all the same goodies the DECU/EDECU does on the GE 701s.  But when that "oh shit" moment comes, the designers provided a life-saving mechanism I appreciated from the pilot standpoint.  

Limit override required a number of criteria to be matched to trigger (Nr drooped below 93% or even *approaching* 93% at a certain rate, collective moving at a certain rate, etc),  which then removed the normal inhibitors and allowed the pilot to tap-into more juice to get out of that sticky situation.  

Limit-override was only available in the AUTO mode, so if the FADEC failed, the pilot still had to go to MANUAL mode, which is essentially the same as placing the 701s in LOCKOUT.  

Anyhoo, interesting discussion.

I hear you.  I wonder if it has something to do with the Army, or when they were developed, as H-53 engines are GE T-64s, and have no TGT limiting.  They also don't have any electronic governing, so again, maybe it was something implemented later.

Automatic bypass of limitation based on rotor droop may be something that needs a FADEC to implement.  Maybe the simpler electronics of ECU/DECU aren't able to handle those kinds of operations.

[JetCat]

Ah a classic Airwolf video having an afterburner on a heli. The Hind would be jealous because she is getting a rotor blade stall on the right side at only 350km/h.

Looks like they used the old eighties trick of rotating the film roll 1/3x faster or even in double speed in certain scenes to simulate "super giga ultra hyper speeeeeeeeeed!!!!!!" of certain overpowered "super-machines" not only in all of the Knight Rider seasons, but in Airwolf too.

By the way: I want a zombie outbreak combat scenario for the helicopters. Please add placeable zombie characters like the Metal Gear Phantom Pain "puppets" into the mission editor. When having Umbrella Corps liveries and Phantom Pain liveries of course there should also be zombies.

[gatordev]

On 11/6/2021 at 11:31 AM, barundus said:

Contrasted with this, the FADEC in the Rolls Royce/Allison in the 58D featured "limit override logic", which, when triggered, opened the flood-gates and removed all the normal nannies and performance-limiting algorithms and replaced them with absolute engine-limit gates that torched the engine, but the pilot got everything those little gerbils in the hot-section could crank out. 

In normal operation, FADEC provides all the same goodies the DECU/EDECU does on the GE 701s.  But when that "oh shit" moment comes, the designers provided a life-saving mechanism I appreciated from the pilot standpoint.  

Limit override required a number of criteria to be matched to trigger (Nr drooped below 93% or even *approaching* 93% at a certain rate, collective moving at a certain rate, etc),  which then removed the normal inhibitors and allowed the pilot to tap-into more juice to get out of that sticky situation.  

Limit-override was only available in the AUTO mode, so if the FADEC failed, the pilot still had to go to MANUAL mode, which is essentially the same as placing the 701s in LOCKOUT.  

Anyhoo, interesting discussion.

 

Disclaimer:  My experience is with the -401C, but the basic function is the same as I understand it...

The T700 does have an "override logic" as well, via Contingency Power, which is a DECU function.  Depending on the ECU/DECU/EDCU/I-EDCU configuration, C-power happens either manually when the C-power switch is selected manually or with I-EDCUs, Auto-C-power turns on when one of the engines loses power (basically Ng decays below some number and Tq decays below some number...50% I think, but I'd have to go look that up).  At the end of the day, activating C-Power keeps TGT limiting, but changes the limit from 839C to 891C (+/- 10...although that number has changed over the years).  You can run at that temp for some length of time, but can STILL go higher (949 for the 401C) if demanded.  Typically the only time you'll go above 891 is if there's a wiring harness/ECU/HMU malfunction (which I've seen pretty often in the past on Navy -60s) or if you go into LOCKOUT improperly.

I'm not sure if the Army T700s had a C-power switch or even have it now with the -701 (I'm guessing not), but I'm pretty sure the function was still there.

This is extra aviation nerdery, but the original Blackhawk transmission (and what is currently in the Navy Seahawks) had such a huge Tq life limit that the limit itself has gone up over time as the -401C equipped aircraft have become heavier.  However, because of that transmission, you can't just put a -701 and new blades onto a legacy aircraft without also upgrading the transmission, unfortunately.

[Hazardpro]

On 11/6/2021 at 11:31 AM, barundus said:

A bit of a departure in the Apache forum, but perhaps a good place to talk about the design philosophy differences between the GE engines that went into the Blackhawk and Apache, and the Rolls Royce/Allison engine that powered the KW.  

I've always had real heartburn about the "save the engine" design philosophy in the GE.  Limiting RPMs when TGTs are approaching limits (acknowledged mostly due to pilot error to end up in the situations in the first-place), or limiting performance in truly life-threating dynamic situations, is such an "engineer-centric" versus "pilot-centric" design approach.  

Contrasted with this, the FADEC in the Rolls Royce/Allison in the 58D featured "limit override logic", which, when triggered, opened the flood-gates and removed all the normal nannies and performance-limiting algorithms and replaced them with absolute engine-limit gates that torched the engine, but the pilot got everything those little gerbils in the hot-section could crank out. 

In normal operation, FADEC provides all the same goodies the DECU/EDECU does on the GE 701s.  But when that "oh shit" moment comes, the designers provided a life-saving mechanism I appreciated from the pilot standpoint.  

Limit override required a number of criteria to be matched to trigger (Nr drooped below 93% or even *approaching* 93% at a certain rate, collective moving at a certain rate, etc),  which then removed the normal inhibitors and allowed the pilot to tap-into more juice to get out of that sticky situation.  

Limit-override was only available in the AUTO mode, so if the FADEC failed, the pilot still had to go to MANUAL mode, which is essentially the same as placing the 701s in LOCKOUT.  

Anyhoo, interesting discussion.

 

The Apache and Blackhawk are two engined helicopters, so some performance loss in one engine isn't the same kind of emergency as in a single engined helicopter like the Kiowa.

[Oshma]

These engines also have a tq matching function that is overridden by DEC lockout. Depending on the time on wing and conditions of the engine, usually one will have a higher power rating than the other. Tq matching will lower the higher powered engine down to close to the power of the other engine that’s usually close to its tgt limit.

So in an emergency that’s not necessarily from direct battle damage you could get some more power from the higher powered engine in theory.

my experience is on Air Force HH-60G’s which use 701C/Ds.

[Raptor9]

6 hours ago, Oshma said:

These engines also have a tq matching function that is overridden by DEC lockout. Depending on the time on wing and conditions of the engine, usually one will have a higher power rating than the other. Tq matching will lower the higher powered engine down to close to the power of the other engine that’s usually close to its tgt limit.

So in an emergency that’s not necessarily from direct battle damage you could get some more power from the higher powered engine in theory.

my experience is on Air Force HH-60G’s which use 701C/Ds.

If a weaker engine runs at a higher TGT than a healthier engine, then it just means that the engine with the higher TGT will encounter its TGT limiter before the stronger engine does.  The TQ matching function is not based on TGT, it will always try to equalize the torque output of the engines regardless of their TGT indication, up to the point one of the engines encounters a TGT limit.  If the weaker engine hits its TGT limiter and the stronger engine has not, the TQ matching function won't hold back the stronger engine, and it will continue to increase in thrust output as demanded by the crew until it too hits its TGT limiter.