EC135

[ec135driver]

Why would you want to do that?

With a FADEC that has frozen at (say) 20% just open the throttle when more power is needed (coming to a hover?)

You would not want to overtorque/temp one engine when the other has a perfectly serviceable manual throttle reversion that will allow you to fly (carefully) almost any profile

[Ox cidental]

135 manual fuel

You should theoretically be able to trash the engine with excessive fuel if operated manually, since there is no supervision of the engine limits.

With full FADEC fail of one engine, you will also lose the TQ and TOT figures (its a function of where the data routes through the FADEC black boxes, whereas the N1 is direct from the motor) and also the FLI needle since it has lost 2 of 3 inputs. You can only match engines by N1 figures. This is quite fiddly, especially with stiff twist grips. An easy procedure starts with noting your take off TQ and N1 figures.

With a FADEC freeze at 20-25% TQ leave it alone as you should have sufficient power for climb, and be able to descend.

On finals, as power demand builds up thru 7.5 FLI on the good engine, set manual engine to the hover N1 figure and leave alone. This will give you both engines for hover landing. Lowering the collective, wind off power to avoid Nr rise.

Hope this helps.......from an EC135/145 beefer.

[TeeS]

Hi Eddie1

To answer your question (based on my understanding of the system so could well be wrong!) yep if you keep raising the lever the good engine will continue to provide more power right up to 128% TQ (and beyond if you droop the Nr below 95%)

Whilst we aim to keep both engines below 75% TQ (on a T2) as we come to the hover, FLI 10 is actually a gearbox rather than an engine limitation so the good engine is not exceeding its limitations by going into the 2.5 minute power band. That is not to say that you won't reduce the life of that engine by using more than FLI 10, that would be up to your engineers and the TM manuals. However a mis-handling of the manual throttle leading to an overspeed or overtemp may well write the engine off!

Ox, I also find it helpful to raise the lever while in stable flight to get an FLI reading of just under 10 on the good engine. If you then note the N1 of the good engine that will give you a maximum N1 figure to open the manual throttle up to for landing.

Hope that helps.

TeeS

[Phoinix]

Just a note, based on my last IFR training flight (where my instructor failed to activate train mode and turned one engine to IDLE).

The engine has a 2.5 minute limitation and based on what we got back from eurocopter, transmission has only 2 minute limitation (not noted in any book to my surprise).
Our flight on one engine lasted for 1' 52'' so we avoided the 2' limitation by just a fraction. The engine was limited by the amount of TQ and time. 2,5' being absolute top, but at a TQ value we were at ~112% (dont hold me on that one, takem from what i remember) ment that we just made it with a 1' 52'' so the engine didn't come off. The transmission has a notice for this event, as if one XMSN chip light comes on, the transmission is of to germany.

[echelipilot]

Hi eddie,

"If you have one engine freeze at 20% Torque can I pull the 128% with the other engine? Will the FADEC of the good engine approve the 128% if the failed engine is officially only "freeze" not "eng fail". What is max. possible TRQ?"

As long as you have frozen the "ill" engine below 30 % Torque you will have the OEI-Power on the "healthy"engine. But as others already stated, why not set the Torque of the frozen engine manually as much as you need it?

Best regards
Tom

[skadi]

@echelipilot
so if one engine produces less than 30%TQ, the Fadec assumes OEI-Limits for the other one?
From where did you get this information? I`ve found nothing in the approbiate manuals...

skadi

[echelipilot]

Hi Skadi,
"@echelipilot
so if one engine produces less than 30%TQ, the Fadec assumes OEI-Limits for the other one?
From where did you get this information? I`ve found nothing in the approbiate manuals...
skadi"

I´ll check the books when back on duty next week.
regards
Tom

[zorab64]

eddie1 -

But if you had 1 engine shutdown within 6500hours, how does this go together with the message of Eurocopter "below 1 fail in 100.000hours" for JAA CAT A procedure certification purposes in Europe?

That's one that had to be shut down in 6500hrs flying - so it's actually 13,000 engine hours. There will be plenty of engines that have flown the full 3500 TBO without problem, and so the average that will make up the certification figures.

As to your other question,

If you have one engine freeze at 20% Torque can I pull the 128% with the other engine? Will the FADEC of the good engine approve the 128% . . . ?

the answer in my boook is No you shouldn't but Yes you can and FADEC will give you as much as you want. Basically, if you have one engine providing power, taking the other into the OEI zone is possible (the only Tq limiting factor is your left hand) but, if you do it, the engineers will be talking to ECD & doing over-torque checks on the transmission. Following the Flight Manual "If flight situation requires max engine power, Tq setting of affected engine may be increased" or similar, should be observed.

[Fly_For_Fun]

If both engines are running, even with one operating at a lower than optimum level or frozen due to FADEC malfunction, you are still in an All Engines Operative condition (they are both still working all be it one in manual) therefore you should observe the AEO limits.

[skadi]

But at which constellation is the system changing from AEO to OEI-Limits respective OVERLIMIT Indication? I think, thats the reason for the original question.
Is it TQ<30% on one engine or 0%TQ, is it related to N1 of the faulty engine?
Its a theoretical question, beside the option of manual override!

skadi

[TeeS]

The good engine doesn't know and doesn't care how much power the other engine is producing. When the other engine Fadec fails, it stops communicating with you and it stops communicating with the good engine. That's why you get a 'DEGRADE' caption on the good engine.

It makes no difference to the good engine whether the failed engine is producing 10%Tq or 100% TQ, it will make a difference to the gearbox though!

TeeS

[zorab64]

skadi -

But at which constellation is the system changing from AEO to OEI-Limits respective OVERLIMIT Indication?

and your other questions re Tq etc.

There is no changeover to OEI limits, they're on the FLI all the time, it's only the start limits that appear & disappear. The Flight Manual tells you that the 2.5 min countdown timer activates as soon as either engine exceeds OEI MCP - but it still stands that taking one engine over OEI MCP, whilst the other is producing power, will result in a XMSN over-torque.

[skadi]

In AEO you get the red LIMIT light with gong at 75% TQ ( T/P2 ) and an steady engine exceedance for >80%/10sec. If you are OEI , you can pull more ( 86/125/128% ) MCP or time limited without the above mentioned light/tone at 75% . Thats what i meant with "change to OEI mode" . So there must be some information going to the FLI to decide whether ist OEI or AEO?

skadi

[WOMBAT45]

Guys this is not torque related. The system senses an engine fail (and displays ENG FAIL on the CAD) when it senses less than 50% N1. When this occurs it changes to the OEI limits. That said the engine is still running but only just.

Try winding off the twist grip next time you shutdown (make sure you go the correct way) you will see it happen before your very eyes.

A lot happens at or less than 50% N1. ENG FAIL caution, start cycle terminates and Fire bottle discharges if EMER OFF Sw pressed.

[skadi]

But if you put one Eng in Idle ( >50% N1 ! ), you can still pull 86% MCP on the other one without red LIMIT . Thats what we did for OEI training before the "training mode".

skadi

[TeeS]

Quite true Skadi, however if you are still talking about post Fadec failure, selecting idle will do nothing because the switch just tells the Fadec to put the engine to idle. Sadly the Fadec is not listening to the switch at this point because it has failed/frozen.

Cheers

TeeS

[RVDT]

A lot happens at or less than 50% N1. ENG FAIL caution, start cycle terminates and Fire bottle discharges if EMER OFF Sw pressed.

and you have a FIRE indication.

Otherwise all the EMER OFF does is close the fuel valve.

[Phoinix]

There is no dual engine HV chart in any twin engine helicopter I'm aware of. The reason is that the engines have enough isolation that no single failure should be able to take both engines out at the same time.
And if there was a dual engine HV chart, you wouldn't want to know how large it would be...
A benefit of having two engines.

Thank you Shawn. For some strange reason I found your post today.

If I understand correctly, than there is no safe procedure for a T/R failure in a hover, lets say under 500ft AGL? I remember a japanese 135 video crashing while at slow speed, low height maintenance flight.

I'm asking about this because my colegues retured from 135 sim with an idea about this. After fenestron failed in a hover 1500ft AGL they tried gaining airspeed while spinning and 1500ft wasn't enough height-red screen. Than they encountered the same situation, stopped spinning by rolling off the twist grips, entering autorotation, gaining airspeed and while at more than 65kts, roll back on the twist grips and you have T/R fail during cruise flight scenario - more survivable. They lost about 1000ft height during that maneuver.

[echelipilot]

FADEC Fail - AEO-OEI Limits

@echelipilot
so if one engine produces less than 30%TQ, the Fadec assumes OEI-Limits for the other one?
From where did you get this information? I`ve found nothing in the approbiate manuals...

skadi

Hi skadi,
basically the information is from several training flights with our TRI´s. It seems that there is no written information, for example in the FADEC-system-description which says “If TQ is 27 % you have OEI Power on the good engine”. The only written evidence I could find is a NOTE in the “FADEC Fail” emergency procedure (EC 135 P2, page 3-22).
“If the flight situation requires maximum engine power, …….tq-setting may be increased. ….Do not exceed the N1/TQ value of the normal engine and the AEO limits.”
Cheers
Tom

[Phoinix]

Hmm, that's valuable information that should be entered in the FLM. Some facts about the EC135 are just not stressed enough in the FLM.


There is one more thing about these "windows" helicopters that I don't understand. A few cautions on the CAD have the importance level at which the manual says "don't start the engines, don't fly..." if one of these appears. One example is "check CAD for no INP FAIL or CAD/VEMD FAN..." that may be listed on the second page of CAD and not straight forward visible to the pilot. Why isn't the system capable of filtering those out and write accross the whole CAD screen "DON'T START, press F1 for more details". It's a straight forward caution or warning using plain logic.