Hello,
I have been flying the 787 with the heavy division mod installed and am wondering if the thrust reduction setting is working as expected. It doesn’t see to matter which value I enter for “THR REDUCTION” altitude on the “TAKEOFF REF” page on the FMC. E.g. mostly I enter 1500ft for both thrust reduction as acceleration height, but the thrust reduction always seems to happen much earlier, e.g. around 500 ft. And if it happens, the thrust is reduced so heavily that it almost go back to idle. So, as soon as this happens, I have to lower the pitch hugely to prevent the speed dropping below the stall speed.
I found a Heavy division github issue describing the same problem, but the issue has been closed already and apparently for some it is working as expected, so I was wondering if others have the same experience as me. Or maybe I’m doing something wrong.
I did some more investigation and reading through the Heavy Division’s mod discord channel and found out that it probably has to do with the default 787 flight model. This is what I understand:
The aircraft accelerates much faster in MSFS than it would in reality (due to a problem in the flight model). As a result the speed goes up much faster than the V2 + 25 (which is the default climb speed that the FMC tries to achieve). So, thrust is reduced to bring the speed back to V2 + 25.
I found a couple of workarounds, that I still need to try out (2. seems the best option):
Actually you can avoid this situation…
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Set THRUST LIM to TO-2 and CLB 2 (if possible)
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reduce your ACCEL HEIGHT to lower value (default is 1500)… with reduced ACCEL HEIGHT the FMC will command normal climb speed (250 knots typically)
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Use THR HOLD mode for take off instead of TOGA
Another workaround can be to not follow the FD for climb pitch (which is about 10 degrees), but increase pitch to about 15 to 20 degrees. This will reduce climb speed as well and prevent it to go (much) higher than V2 + 25