UH-60L / S-70 Torque Split

[CW Pirate]

I fly the S-70A-9 Black Hawk and have a question relating to ECU malfunctions. I understand that the UH60L is very similar to our S-70A-9 (General Electric T700-GE-701C engines)?

In our checklist, there is an EP to manage a torque split (any time the torques are split by >5 %), and an EP to manage an ECU malfunction with a low-side failure (when the residual tq on the malfunctioning engine is zero).

Some people are saying that the torque split cannot occur (ie that you will always end up with zero tq) and that the checklist EP is redundant. Both EPs result in the engine being placed in 'ECU lockout' in any case. Same people have said that the tq split checklist used to be in the US Army UH60L checklist but has been taken out.

Others say that a tq split can occur but no one claims to have experienced one.

Are their any UH60L pilots who can confirm whether the Tq Split EP is in their checklist or not? Has anyone experienced one?

Thanks!

CWP

[busdriver02]

Air Force H-60 checklist still has torque split as a procedure. The short answer is that the checklist has you trouble shoot which engine is the problem child and then control that engine manually.

[CW Pirate]

Yep sounds identical. Know if any one has had one?

[TwinHueyMan]

I have sheared a LDS shear pin and seen one engine scream up while the other follows, then drops down to nothing in an attempt to control the NR through torque matching/load sharing... as well as a low side ECU failure (old A Model). The former results in a lockout control of the high side failure engine, the latter a lockout control of the low side engine. Steps 2-3-4 of the "%TRQ Split between Engines 1 and 2" in TM 1-1520-237-CL covers both a high and low side failure starting with retarding the high power engine and seeing if either A. the % TRQ on the low side engine increases, or if B. % RPM R decreases (!), to determine if it is a high side or low side failure.

High side failures are identified by the engine hitting the POU (-700) or ODV (-701) limiter, which makes a hard jolting motion through the aircraft like a rev-limiter on an automobile engine. You can fly like this for as long as you'd like, as the engine will prevent itself from causing harm so long as the POU/ODV is working properly. Low side failures (not at high power requirements) usually are identified by a "hey, look at that, the torques are splitting... interesting" comment by the pilot not on the controls. I would prefer the checklist clarify before just saying to retard the high side engine, as it may be the only engine providing any power. Identifying a typical high side failure is almost foolproof (bang bang bang bang!) and a low side failure during high power demands requires the same response as decreasing RPM-R - fly out of it before worrying about the root issue.

Mike

[JohnDixson]

CW,

While the posters have the correct drift, I have sent a PM with a few contacts, who will be able to get you the current and correct manual situation.

Thanks,
John Dixson

[Shenanigan]

Considering the -10 for a UH-60A and UH-60L are the same and the EP is in the -10 I would be surprised if it wasn't in the checklist. I fly a UH-60A+ which uses the 701 engines of the UH-60L (still has A model XMSN) and it is in my checklist. Here is the first step-

If TGT TEMP of one engine exceeds the l i m i t e r ( 700 8 5 2 ° C , 701C 701D/CC 875°C with low power engine above 50% TRQ or 901°C with low power engine below 50%TRQ), retard ENG POWER CONT lever on that engine to reduce TGT TEMP. Retard the ENG POWER CONT lever to maintain torque of the manually controlled engine at ap-proximately 10% below the other engine.

Which outlines procedures for both engines.

I imagine the idea that the torque cannot split comes from the fact the the DEC (ECU in 701) is backed up by aircraft power. So in a UH-60A a loss of the engine alternator would cause the ECU to lose power and you would lose all the functions including torque matching load sharing and supposedly the engine would fail to the high side causing a torque split. In the L model a loss of the alternator would not effect the DEC functions just cause the NG signal to fail and get an engine out warning.

So in the 701 engine I'm sure the chances are much slimmer for a torque split but since the DEC is still a piece of equipment that is capable of failing all by itself it remains a possibility even if it is remote.

[S92 driver]

CW, send me a PM

[before landing check list]

I have over 2000 hours in the A and L. I never really liked the procedure for the trq split. The 1st thing you should do upon noticing the split obtain single engine airspeed while checking RPMR. If it is high then you have a high side, if low you have a low side. If correct then slowly reduce the power on the high trq/tgt engine and see what the RPMR will do. If RPMR drops then put the engine throttle back where it was and take the low trq/tgt engine to lock out. Works for all the twins I have ever flown.

The problem is we never seem to check RPMR 1st to see what is happening.

[Shenanigan]

I don't think you would necessarily get a rise in RPM R in a high side failure.

[before landing check list]

True, so you go for the high trq/tgt engine and see what happens to RPMR as you slowly retard that throttle. If RPMR drops then put that throttle where it was and the other should go to lock out and adjust accordingly.

[SASless]

Question......

It would seem a "Low Side" failure would result in either normal Nr or lower Nr than originally set....and a "High Side" failure would result in higher Nr than originally set.

The question...."If you move the Collective....during a High Side failure....would the Nr not increase if the Collective was reduced and either stay the same if raised slightly?"

A second question....."In a High Side failure....does the N-1, Ng, or whatever it is called in the Blackhawk stay in the governor range or does the engine go to Topping or beyond?"

Next to Last question....."Does the 'Good Engine' respond correctly to Collective Movement?"

Final question....."Are you using Torque as the way to diagnose the problem or using Gas Producer and Power Turbine indications along with Nr?" I would suggest the Torque indications are not really that useful in diagnosing the problem. I taught Governor failures by disabling the Torquemeter Indicators or covering them up altogether.

As the Torquemeter needles do the most moving around compared to other indicators...they seem to attract the eye the most and offer the least useful information.


I have flown seven different Twins and have had every kind of governor or fuel control failure known to Man I think....all but a few were pretty much non-events....while two really...really....really stand out and both of them were in the Chinook. One event that stood out was two different problems....on two engines simultaneously in a very awkward situation and the other was an engine that went to absolute max power and would not respond to any corrective action....in an empty aircraft very low on fuel which made for a vertical rocket with very dangerous Nr speeds.

[Lonewolf_50]

beforelandingchecklist ... that rings a bell.

The torque sharing system can occasionally fool you, but NR tends to help you find out what's actually going on as you change power.

[Shenanigan]

It would seem a "Low Side" failure would result in either normal Nr or lower Nr than originally set....and a "High Side" failure would result in higher Nr than originally set.

Basically yes. Here is my understanding. A high side failure will cause the engine to increase power up to 120% engine RPM or max torque available. So if you were at 70% torque to maintain 100% Rotor and one engine failed to the high side you would probably see one engine go up to max torque available (TGT limiting), lets say that is 120% torque. Since the total torque before was 140 (70 per engine) the other engine would reduce to maintain 100% by going to 20%.

If you were at 50% torque dual engine torque under the same circumstances than the high side engine would go up to 120% RPM since it wouldn't reach max torque available and the other engine would go to 0 torque.

The question...."If you move the Collective....during a High Side failure....would the Nr not increase if the Collective was reduced and either stay the same if raised slightly?"

I would say from this the dual engine aircraft you operate is the same as a Blackhawk. That is exactly what I would expect to happen presuming the one engine had the power to increase the NR.

A second question....."In a High Side failure....does the N-1, Ng, or whatever it is called in the Blackhawk stay in the governor range or does the engine go to Topping or beyond?"

Below -10C the engine is typically limited by NG, above It's limited by TGT, it is also limited to 120% RPM so if the TGT limiter or NG limiter was not hit it can go to 120% engine RPM in a L model Hawk. The Rotor however is not supposed to go pass 107. Not sure why they didn't limit engine RPM at 107 like they did in a A model.

Next to Last question....."Does the 'Good Engine' respond correctly to Collective Movement?"

I would presume it does as long as one of the limiters is not met.

Final question....."Are you using Torque as the way to diagnose the problem or using Gas Producer and Power Turbine indications along with Nr?" I would suggest the Torque indications are not really that useful in diagnosing the problem. I taught Governor failures by disabling the Torquemeter Indicators or covering them up altogether.

Yes that is how the EP is written. If the RPM R is increased or decreased it's initially a different EP. The procedure is essentially to pull the high TGT engine lever back slowly and see if the other engine torque increases- if it does than it's a high side failure and you continue pulling back to manually control torques close to equal. If the Low engine doesn't increase than it's a low side failure and you can take manual control if the power is needed.

The procedure makes sense to me and I don't really know a better way but if you have a method I'd be interested to hear it. From what you are saying it would seem you could essentially run the same check by moving the collective instead of the Engine Power control levers and I can't see why that wouldn't work.

As the Torquemeter needles do the most moving around compared to other indicators...they seem to attract the eye the most and offer the least useful information.


I have flown seven different Twins and have had every kind of governor or fuel control failure known to Man I think....all but a few were pretty much non-events....while two really...really....really stand out and both of them were in the Chinook. One event that stood out was two different problems....on two engines simultaneously in a very awkward situation and the other was an engine that went to absolute max power and would not respond to any corrective action....in an empty aircraft very low on fuel which made for a vertical rocket with very dangerous Nr speeds

[SASless]

For the record....never sat in a Blackhawk but once at an Airshow and know naught of how they work.

Years of flying the Cninook taught me a few things about diagnosing engine problems....and adhering to the KISS method works the best.

Basic Assumption is you have not moved the Collective (Thrust Lever in real helicopters)...and in your bi-hourly cross check of the engine/rotor gauges....you notice a deviation from Normal.

High Nr....can only mean one thing.....it is a high side failure of some kind.

Low or Normal Nr with split indications mean it can be either a Low Side problem or a Static problem.

A split in Torque or Exhaust Temp or Gas Producer or Power Turbine.....is an indication of a problem....not what the problem is.

If one starts with the Nr....then casts an Eagle Eye through your Aviator Ray Bans to assess where all the other gauges are resting.....and compare the indications to the "normal ranges" the engines are supposed to operate at....you can begin to sort out what is going on.

Bottom line....if you move the Collective (or Thrust Lever)....in an ideal world both engines will respond in a normal manner and the Nr would remain constant. If one engine is reacting normally....and the other isn't.....the KISS method states the one that is not reacting normally is the problem child.

There is no need to move an Engine Lever/Speed Select/throttle until after doing the Collective Check (IMHO). Odds are....if you check with Collective first....you will get the correct Engine Lever on the first go....rather than having a 50% chance of getting the wrong one (assuming you can remember to keep the two things sorted out as to which is #1 and the other is #2....Port and Starboard for the Navy and Coasties....or however the Zoomies do it.

I would also suggest livening up a Safety Meeting with StanEval by asking why you even want to move things and shut things off if the Nr is in the right range as if one does nothing....one does not do anything wrong. (Assuming a very short flight to a safe landing spot.....then sort stuff out on the ground).

[before landing check list]

Just check RPMR 1st and before you move a throttle achieve SE airspeed.

[Lonewolf_50]

Back when I flew Seahawks, the number one step was "control Nr" which implies doing more than looking at it. :E


EDIT: never mind, the formatting went south.