Ref the FTR discussion - the following is from the recently published TSB Canada report into the S92 LOC incident offshore (
https://www.tsb.gc.ca/eng/rapports-r.../a19a0055.html). It tends to support what many of us have said/known......
In tests conducted by the RCAF, helicopter pilots who used ATT mode while minimizing the use of the trim release had far better control in a DVE than pilots who attempted to fly with the trim release button depressed. Pilots who flew with the trim release button depressed “often failed to interpret residual pitch or roll rates (or vertical velocities) due to the reduced cues and aircraft control suffered resulting in ineffective approaches or in the worst case ground impact.”
The RCAF’s CH146 Griffon Standard Manoeuvre Manual states that using the force trim will assist in maintaining a steadier hover and aircraft attitude during night and/or during overwater operations.
Additionally, the RCAF’s Air Mobility CH149 Cormorant Operations manual warns against using the cyclic trim release button, and states the following: In low visual cueing environments (IMC, night, boat hoist, etc.), the pilot should attempt to maintain attitude retention by avoiding the use of the cyclic Trim Release button. Small and precise attitude changes can be made using the cyclic beep trim switch only. Alternatively, the pilot can easily move the cyclic in the manoeuvre mode then use the beep trim to relieve control forces, resulting in faster trim rates.66