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invernyx / md11-bugs

The official bug tracker for the TFDi Design MD-11
https://tfdidesign.com/md11.php
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[BUG] - Momentray nose down when disconnection AP until LSAS engages #1527

Open KJA1582 opened 3 months ago

KJA1582 commented 3 months ago

Describe the bug

When disconnecting the AP, the elevator pitch returns to zero before LSAS engages in pitch hold. This creates a nose down moment

Steps to reproduce

Fly ALT HOLD on AP Disconnect AP

Watch Elevator Deflection in Debug Aircraft Data dip

Expected behaviour

Smooth transition

Evidence

Dip at 7s is AP disconnect transition to LSAS pitch hold

Screenshot (806) Screenshot (807)

Simulator

Microsoft Flight Simulator 2020 (MSFS)

Crash

No

Phase of flight

Cruise

Pitch

6.2

Bank

0

Heading

259

Altitude

5000

Departure

EDDM

Arrival

EDDM

Cruise level

5000 ft

ZFW

112.7 t

CG

25.7

Fuel

15 t

Cost index

N/A

Route

N/A

Location

N/A

Agreement

TheFightingRaven commented 2 months ago

most likely related to trim issue

KJA1582 commented 2 months ago

Makes it appear more often, but the underlying "error" (if one can call it that) is that AP lets go of the elevator and it takes some time for LSAS to engage pitch hold. That little bit of time is enough for the pitch to drop (or rise, but currently the dropping is more likely given the trim issue) when in any out of trim situation (so even when the pitch is fixed, if the aircraft is in a out-of-trim situatuin, that will happen)