#1 TMS temperature setting in TGT mode von Salvador 24.11.2008 18:51

Hi all,

I wonder if anyone can give some guidance on which TGT temperature value one has to dial in during the climb... at the moment I just pick an N1 value smaller than the TOGA value and adjust the TGT to keep that N1. But I imagine in the real aircraft there are possibly tables or at least a rule of thumb on how to choose the temperature based on altitude, ISA deviation, etc.

Any guidance on this is appreciated!

Thanks,


Salvador
#2 Re: TMS temperature setting in TGT mode von Adrian19 26.11.2008 02:49

avatar
Hi Salvador,

welcome to the forum.

The TMS is relatively simple to use and a full explanation is given on P.97 of the manual.

During pre-flight, set the reference T° in the top right box of the TMS, this would normally be the OAT. When you're lined up ready for take-off press the TO button, this puts the TMS in Take-off mode and automatically sets the N1/N2 thrust. Gradually advance the throttles until the 4 blue arrows extinguish, the TMS now monitors and controls the engines.

Once you have taken off and are on climb out, press the MCT mode button, the TMS now automatically sets the Maximum Climb Thrust N1/N2. Adjust the throttles to extinguish the white or blue arrows and the TMS once again has control.

When you reach your cruise altitude switch to TGT mode and dial the required T° in the lower lefthand window, I generally find 660/680°C gives a nominal cruise speed of 0.68mach @ FL280, you will need to adjust this depending on weather conditions/OAT. Once again, adjust the throttles until all the white and blue arrows are extinguished to give control to the TMS.

Hope this helps,

Regards,
................Adrian W.
#3 Re: TMS temperature setting in TGT mode von Salvador 27.11.2008 20:35

Superb explanation Adrian! thank you very much!

The point that I actually failed to understand is that MCT was the climb thrust . I was under the impression that "max continuous" was something like an "emergency mode" max thrust, something to be used in, say, an engine out situation...

Thanks again for your help!


Salvador
#4 Re: TMS temperature setting in TGT mode von mach7 07.01.2009 02:04

As far as the TMS is concerned. There are no charts for setting temperature on the ALF502 or LF507. The only charts would be for setting the N1ref or flex for takeoff which is based on pressure altitude and temperature.

This N1 value is allowed to increase 1 percent per 1000 feet in the climb, assuming a standard atmosphere.

After takeoff, we would set in the master engine TGT in the temperature window, then make a selection of TGT + SYNC mode. This will control the master engine at the selected TGT value and drive the remaining engines to the masters N1 speed. During climb we would advance the TGT in 20 degree increments until the hottest engine reached 800 degrees.

After this we would select a straight TGT of 800, (no sync mode). This will drive all engines to 800 degrees. This would give a small variance in N1s and N2s, but it got us to altitude quicker.

MCT was only used in the event we lost an engine. MCT would drive all the engines independantly to there Maximum thrust output of 96.7 n1, 96.9 n2, or 857 degrees TGT, whichever value was reached first.

Contrary to the simulator profile, in the real aircraft the engines will get hotter as you climb because you are asking them to work harder. The sim profile has them getting cooler as you climb.

A typical reduced thrust takeoff at ISA conditions would show a takeoff TGT of approximately 760 degees C. As you climb, and add power. You would reach 800 degrees at about 15000 feet...depending on the atmosphere.

Although BAe states 857 degrees is max continuous. We found that a lot of hot section stress occurs on the engines at temperatures above 800 degrees. (857 was always available to us, but we would only go to 800 with engine anti-ice off, 810 with engine anti-ice on, and 830 with airframe ice on.

To give a closing example, on a hot summer day at FL280, we would normally have 800 degrees on all the engines trying to maintain .68 mach.

Hope this helps

-Jim
#5 Re: TMS temperature setting in TGT mode von Salvador 16.01.2009 21:01

Thank you for your response Jim, I'm impressed by your knowledge... do you have experience with this type as flight crew or MX?

From your explanation I take it that it's not possible to operate the TMS in TGT mode realistically since the temperature profile in the sim behaves the wrong way around... still I guess one could go on reducing the TGT temp during climb in order to keep N1 within limits, then cruise TGT setting would be more like Adrian suggested earlier.

Best regards and thanks for your post,

Salvador
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