DEECs and powerplant management

[svcta]

Hey, all,
question came up recently about operating engines with DEECs. Specifally TFE 731-40Rs. Question is this: should you manually set climb/cruise power along the way or set the levers in the "flats" and leave them alone. It was a different "-" number that a friend said they were told to not adjust the power settings on throughout the flight, but only to verify the proper settings are being set by the airplane and not tweek them.

The reason that I ask is that one of the guys I fly with routinely(as in always) sets the power on our powerplants to maintain ITT right at 900 degrees, which sometimes puts the power levers way out of the "climb" decals and closer to "T/O". I understand that those are only decals, but after the other conversation I want to be sure we're not improperly running our airplane. I'm about to hit the books and see what I can come up with, this was my first stop. Insights are appreciated.

 

[LJ45]

put it in the detent and leave it alone!! That is assuming you have detents like the Learjet 45.

 

[Rokit88]

DEECS dont have detents. If you have detents in your throttle quad, then you have FADEC.

If he is running that moter at 900 ITT, tell that him that he is being hard on the motor. You wont get that much more performance out of it, but you will wear it out faster.

 

[LJ45]

you have never flown a Learjet 45 with the TFE731-20 with Detents and DEEC's. You sir are wrong There are many airplanes without dual channel controls, so they are not FADEC but still provide the same function with hydro-mechanical backup instead of the second channel computer.

 

[NotFurloughed]

Deec

Yup, CE-560XL has pneumatic detents on the dual channel EEC's (manual backup)...no FADEC. In fact, they're almost identical to the 750 that has FADEC.

So, put 'em in the detents, and don't let the engine manufacturer catch you running the temps up like that.

 

[svcta]

There are just so many versions of the TFE-731, my understanding is that the temps run anywhere from (normally) the high 700s to almost mid 900s. All depending on the dash #. Anybody with some insight on the -40?

Thanks so far to all.

 

[LJ45]

It is my understanding, from what I read in the Honeywell info and have been told by the Honeywell engine rep. that... The -20BR and -40 have the same ITT limits and are the same engine except for the fluted nozzle and the take off thrust rating. To give you more info, usually the engine computer is holding 100 % N1 in the climb are very close to 100%. ITT limits for the -20BR is 991 climb and 974 is the cruise.

The "approved" procedure in the AFM is what should be followed for your aircraft.

 

[h25b]

Whatever the AFM tells you to do. You have to understand that the DEEC and a FADEC are two entirely different animals. Setting them to a "detent" and just forgetting about them IS NOT proper procedure.

 

[LJ45]

Whatever the AFM tells you to do. You have to understand that the DEEC and a FADEC are two entirely different animals. Setting them to a "detent" and just forgetting about them IS NOT proper procedure.

True...you still have to make sure the ITT is with in limits. Unless something is wrong with the engine it should be within limits, since the DEEC on the -20 sets the appropriate N1 for the conditions.
The DEEC on the -20, -40 and -60 are not like the other 731 DEEC. For example we start the engine at Idle. The DEEC's on this series does a lot more the earlier model 731 DEEC's.

 

[h25b]

True...you still have to make sure the ITT is with in limits. Unless something is wrong with the engine it should be within limits, since the DEEC on the -20 sets the appropriate N1 for the conditions.
The DEEC on the -20, -40 and -60 are not like the other 731 DEEC. For example we start the engine at Idle. The DEEC's on this series does a lot more the earlier model 731 DEEC's.

I see and speak to many Learjet 45 drivers that are confusing the DEEC with FADEC. The FADEC is set it, forget it... The DEEC is not. You are also correct with respect to the earlier N1 DEECs that you find on the higher serial 31A's and that are being installed on earlier model airframes in general. Honeywell's MSP program is requiring this installation on MSP covered TFE731's. The main reason is for the ECTM (Electronic Condition Trend Monitoring) capability.

 

[LJ45]

I see and speak to many Learjet 45 drivers that are confusing the DEEC with FADEC. The FADEC is set it, forget it... The DEEC is not.

More info...Please!

 

[ultrarunner]

Set N1 according to the chart. That is limiting until ITT becomes the limit, and at somepoint on a 731 you will reach the ITT limit and subsequently will need to reduce N1.

I'm not aware that Garrett makes any of this a mystery in their AFM supplements. Do what the AFM tells you.

 

[svcta]

Well, they really don't give you anything other than basically "climb thrust setting as attained wihtthe thrust levers in the CLB position and by reference to N1" And it says that "max. climb thrust setting may be used throughout the climb segment...."In our a/c the thrust levers at that location gives us N1 that is below and ITTs way way below max climb thrust(recommended). Like around 100 degrees cooler. My question now becomes why are our settings so low at the CLB setting? Should that be altered at all? Any other G100 guys with similar experience?

 

[h25b]

More info...Please!

F ull A uthority D igital E ngine C ontrol

"Full Authority" being the operative words there...

 

[svcta]

That's great, everybody, but I'm not talking about FADEC. I wish I did but I don't fly an airplane that has it anymore.

 

[h25b]

That's great, everybody, but I'm not talking about FADEC. I wish I did but I don't fly an airplane that has it anymore.

With your specific aircraft I would say if it's operating that much below parameters it needs to go to the nearest Honeywell service center for some engine runs where they will most likely adjust the DEEC's. It would make me wonder whether you're actually attaining full T/O thrust in that detent. What does it do with the PL's in the T/O position? Are you getting book N1 within ITT limits ???

In the meantime I'd tell that guy to bring the power back to whatever the book numbers are, especially if the engines are on MSP and submitting the DEEC downloads to Jet-Care for trend monitoring. You'll have some explaining to do and will risk MSP not covering the next engine maintenance event.

 

[svcta]

We're going in for A/B check in a week so hopefully I can get those things looked at then. We are making good N1@ T/O setting(no detents on ours), and we're actually WAY below the max ITTs(in the climb & cruise) so I know we're not burning the things up. But the main question with me has turned to wondering why the ITTs are so low even near the proper N1 settings in climb. We're talking a hundred degrees. That just sounds like a lot of wasted headroom to me.

 

[Blackjet]

N1 is King. The DEECs have tattle-tales, so there's no covering up what Honeywell considers abuse. Have a look at the -40R climb and cruise instructions:
https://www.e-engines.honeywell.com...+Pilot+Tips+Booklet&commarea=Pilot+Tips+Books

 

[ultrarunner]

And it says that "max. climb thrust setting may be used throughout the climb segment...."In our a/c the thrust levers at that location gives us N1 that is below and ITTs way way below max climb thrust(recommended). Like around 100 degrees cooler.

When you're talking 'location', you're referencing the little pieces of tape that mx put next to the thurst levers when they set up the DEEC's? That was what i remembered when I flew a DEEC plane. Then at some point, mx removed those little pieces of tape.

I have not flow a -40 motor, so I can't speak for the N1/ITT relationship. Set N1 according to the chart. Don't sweat the pieces of tape. And have mx do the 12 point runs one night. It's no big deal so check to see if things are set correctly.

 

[HMR]

svtca- He must've discovered the mythical chart in the G100 or Astra AFM that relates to setting the temps to 900.

Are you familiar with the acronym, RTFM?