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CaptKornDog

Takeoff Thrust Settings?

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Hello,

I’ve been browsing through the manuals and reference documentation in the forums, I was wondering though if there was some gouge out there on takeoff thrust settings; or perhaps reduced thrust takeoff procedures?  I certainly know the plane has a pretty short roll and rapid climb, but cross checking with what videos I can find also, it seems that there may be some reduced settings out there in terms of ITT or N1/N2 some operators use.

 

Just curious what information may be out there.  Thanks.


Kyle Weber (Private Pilot, ASEL; Flight Test Engineer)
Check out my repaints and downloads, all right here on AVSIM

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Posted (edited)

Kyle,

The Lear 35 was the first airplane to use the Garrett Air Research TFE 731 engine. The original 731s were controlled with Electronic Engine Computers, or "EECs".  There was an option in the late 90's - early 2000's to upgrade to Digital Engine Computers or DEECs. I cannot recall whether FlySimware models the EECs or DEECs.  Ark?  Can you answer this one?

The EECs were "technically" designed such that you could set takeoff thrust by going full thrust levers forward to the stop and not over-temp the engine on ITT or over-boost the engine (i.e., exceed takeoff N1/FAN).  As engines wore in, it was possible to over-temp by going full forward with the thrust levers. When I was an instructor/TCE in the 90's at FlightSafety on the Lear 35 that had the EECs, we taught as a technique to go full forward, and then back off one knobs width.  In other words, thrust levers to the firewall and then walk one thrust level back a knobs width, and then match the other backwards.  In the simulator, that technique almost always resulted in a takeoff FAN/N1 setting very close to the QRH Takeoff Thrust table, and allowed us to keep training moving along.  I know that some operators used this technique in the field.  With the DEECs, I am not sure if it's a valid technique anymore. I have used it in the FlySimware Lear and it does appear to work well.  

After takeoff, 400' AGL, bring the flaps up, turn the YD on, then set 795 on the ITT for initial climb thrust.  On an old engine, this will keep you safe if it you maintain 795 ITT in the climb.  On a new engine; however, blindly setting and climbing out at 795 can over boost the engine and cost in the hot section. 

Hope this helped.

Rich Boll

Wichita, KS

 

 

Edited by richjb2
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Richard Boll

Wichita, KS

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As I recall from earlier threads here, the FSW Lear 35 is configured with FADEC, so it's power levers to the firewall for takeoff and the computer manages power output to maintain maximum thrust for the given environmental conditions.


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5 hours ago, somiller said:

As I recall from earlier threads here, the FSW Lear 35 is configured with FADEC, so it's power levers to the firewall for takeoff and the computer manages power output to maintain maximum thrust for the given environmental conditions.

Hmm.... could be I suppose, but I just don't recall any discussion of a FADEC in the Lear35.

Al

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19 hours ago, somiller said:

As I recall from earlier threads here, the FSW Lear 35 is configured with FADEC, so it's power levers to the firewall for takeoff and the computer manages power output to maintain maximum thrust for the given environmental conditions.

The  Lear 35 or any TFE 731 does not have true FADEC.  The DEECs  provide much of the same functions as a FADEC; however, the 731 does have a cable back up and flyweight governor control in case the DEEC fails. The governor normally  acts as an overspeed protection device, but when the DEEC or EEC fails, it acts as an on-speed governor.   A FADEC has no direct link between the thrust levers and the engines beyond an electrical signal.  If that electrical signal is lost or the FADEC itself fails, the engine either shuts down or goes to idle depending on design. 

Rich Boll


Richard Boll

Wichita, KS

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Good info, thanks Rich.

Al

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16 hours ago, ark said:

Hmm.... could be I suppose, but I just don't recall any discussion of a FADEC in the Lear35.

Al

Yes, probably would've been more appropriate to say FADEC-like. The thread I am referring to had a post by FSW resident Lear 35 pilot where he stated they just push the throttles to the stops and the computer manages power output.

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23 hours ago, somiller said:

Yes, probably would've been more appropriate to say FADEC-like. The thread I am referring to had a post by FSW resident Lear 35 pilot where he stated they just push the throttles to the stops and the computer manages power output.

I seem to recall that what he describes is the correct procedure for the Lear 35's with the DEECs.  My last Lear 35 flight was in 2004, just was we got rid of our last Lear 35 for new Lear 45s. We had the EECs, but FSI was discussing the DEECs in recurrent training.  I don't think that their simulator was programmed for them. 

Just a side comment, FlySimware did an excellent job on the C414 in MSFS.  I can't wait to see the Lear 35 in MSFS! 

Rich

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Richard Boll

Wichita, KS

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So the proper technique in the FSW model is to just firewall it regardless for takeoff roll?


Kyle Weber (Private Pilot, ASEL; Flight Test Engineer)
Check out my repaints and downloads, all right here on AVSIM

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On 7/17/2022 at 4:30 PM, CaptKornDog said:

So the proper technique in the FSW model is to just firewall it regardless for takeoff roll?

That’s what I’m trying to figure out haha nobody on here has given a clear answer 😂

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Not sure what is programmed in Flysimaware's LR-35, but when I fly it, I use a technique that we taught at FlightSafety and that was used in the airplane with the EECs.  You push the thrust levers to the firewall, then back them off by about 1 inch (about a knobs width). Doing so will roughly set FAN (N1) speed to the scheduled setting in the QRH's FAN Speed chart.  I still have checklist for the Lear 35.  When I used technique in the FSW LR-35, the resulting FAN speed come out just about right.  After the gear and flaps have retracted, set 795 on the ITT for MCT.  As long as you're not flying a brand new engine or one just out of hot section, you shouldn't overboost the engine.  If it's new or just out hot section, then you might want to consider using the MCT FAN speed charts to avoid exceeding rated MCT. 

If the DEECs are modeled, then you should be able to firewall the thrust levers. 

Rich Boll

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Richard Boll

Wichita, KS

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