FMS: Thrust Limit Page

[anthony_d]

Evening all,

Try the following actions.

1.Start up the plane, "runway threshold" ready.

2. Enter the thrust limit page on the FMS.

3. Type 86 onto the scratchpad and enter it on the top left button (1LK). This shouldn't work according to the manual, but you should anyway observe strange happenings with your engines!

On each occasion the engines shut down. Additionally:

- Two occasions the ITT went crazy with the dial rotating anti-clockwise and showing minus thousands of degrees celcius.

- Two other occasions the plane went backwards rather quickly. One resulting in a crash (a plane crash, not a CTD).

It seems to be very repeatable.

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Now follow the manual (Page 73).

Enter an outside air temperature into button 4RK. You'll observe the thrust limit numbers on the left all showing zero.

For the purposes of this test I selected the TO number (1LK) to enter into the scratchpad before entering into 1RK. At this point the engines shutdown again with strange happenings.

[philipp]

3. Type 86 onto the scratchpad and enter it on the top left button (1LK). This shouldn't work according to the manual, but you should anyway observe strange happenings with your engines!

You are not allowed to enter any value on the left side. It displays computed values and activates them. So pasting any number on the left side will ignore the number (you could enter 1000%) and set the limited to the computed value.

That it allows you to set 0% which sends the engine controller go haywire and kill your engines in the most stupid ways indeed qualifies as a bug. However, this should not happen when you follow the procedures in the manual.

Now follow the manual (Page 73).

Enter an outside air temperature into button 4RK. You'll observe the thrust limit numbers on the left all showing zero.

That means you have not selected a take off runway. TO calculate the thrust limit, the FMS needs to know the elevation of the departure runway. That means you must have entered your flightplan (which of course includes the departure airport) AND you must have set the active departure runway.

Philipp

[anthony_d]

Thanks for the detail Philipp.