8 hours ago, Denco said:

The biggest issue I have with the PMDG 777 is the trimming behavior. The aircraft does not appear to respond to trim inputs while I am holding pitch pressure on the joystick. I have to return the stick to neutral before the trim takes effect.

In the FF 777, I can trim the aircraft while still holding a pitch input, either nose up or nose down, and then gradually release pressure on the stick until the aircraft reaches the desired trimmed speed. This feels much more natural and realistic.

The Boeing 777's electric stabilizer trim switches remain fully functional in flight, but they do not behave exactly like the trim system in a conventional mechanically controlled aircraft.

The key difference is that the 777's fly-by-wire flight control system incorporates Trim Reference Speed (TRS) logic. During manual flight, the Primary Flight Computers continuously reposition the stabilizer to maintain a reference speed while minimizing sustained control-column forces. As aircraft configuration, thrust, weight distribution, and flight conditions change, the system automatically adjusts stabilizer trim to maintain the desired speed and handling characteristics.

When the pilot actuates the electric trim switches on the control wheel, the stabilizer is commanded to move. However, unlike a conventional aircraft, this input is not simply a direct request to relieve elevator force. Instead, the flight control system interprets the trim input as a command to establish a new trim condition and corresponding Trim Reference Speed. The PFCs subsequently manage stabilizer position as required to maintain that new reference condition.

As a result, nose-up or nose-down trim inputs effectively command a new speed-stability reference, after which the fly-by-wire system automatically trims the aircraft to eliminate sustained column forces. The pilot can therefore use electric trim for fine adjustments during manual flight, but the underlying system logic is fundamentally different from a conventional aircraft, where trim directly offsets elevator hinge moments and control forces.

The PMDG 777 Trim Reference Speed establishment and subsequent automatic stabilizer repositioning do not accurately reflect the Boeing 777's intended flight-control laws and need fine-tuning. 

Sounds like PMDG are looking into this and updates are to come for the 777. Just hope it doesn’t take months for it.

They may even throw in that mythical sound upgrade package as a bonus 😁

apologies, wrong thread - great age!

Edited 8 hours ago8 hr by JaneRachel