.... in particular the last line has been worrying me. From the responses so far I am getting the impression that here may be many AW139 pilots out there who are using the 'fly-through' technique perhaps more than they should.
The argument in EH9, The EHEST document on Management of Automation asserts that the fly through technique is to be used in preference when making a turn because a stable condition with wings level can be assured simply by letting go of the cyclic. This may have been logical thing to do in the days of helicopters that rely on a simple SAS but it is not logical when you are flying a coupled 3 axis AP/FD system in a latest generation helicopter.
For a start the way to fly the aircraft is primarily by using the coupled modes. If you choose to use the beeper (no HDG mode engaged) instead of the HDG knob (in HDG mode) you are in fact doing exactly the same thing as using the HDG mode. In both cases the cyclic remains in the same position throughout.
The 139 has the added facility of being able to 'drive the heading bug to a new datum via the beeper trim in which case it will use the appropriate angle of bank for a rate 1 turn until settling on the new heading.
The idea that whilst using 'fly-through' you can respond to an upset by letting go of the cyclic is fatally flawed in the 139. The most common way we see pilots arriving at an AP-OFF situation is by their mis-selection of the SAS REL button whilst going for the FD S/BY button. We, at the same time as teaching how to manage the FD Modes, teach the industry standard response to an apparent failure of the system to do as we ask of it and that is to revert to 'manual' flying until we have understood what went wrong. What I witnessed recently was a pilot doing exactly as we wanted him to do except he found the wrong button and took out his AP's. Very nasty as he was IMC. The subsequent red screen was acutely embarrassing.
The answer as to why there is a propensity to make this mis-selection may lay in the way other types make use of cyclic buttons. Some have CAS Message cancellation buttons for example. If you are flying two types and they are very different in this respect (i.e. they have buttons in the same place but they do different things) then we have accidents waiting to happen.
The question of 'Flying-through' being in any way logical in today's complex helicopters is called into question insofar as we do not apply the same logic to the collective. If the power is set at 'cruise' and the collective moved against the spring for any climb or descent then the EHEST logic would allow us to take our hands off the controls when we encounter an 'upset' and we would be returned to 'wings level in level flight'. We don't though, do we! Do we? I hope not.
We never move the collective without pressing the FTR button first. All I'm saying is that we should be applying the same philosophy with moving the cyclic. When a stable condition has been achieved then it's over to the beeper.
I am mindful of the fact that there are many 139 pilots who achieved their TR somewhere other than at a factory school. Maybe that's why they didn't get the message. Maybe you did attend a factory school or were taught by a factory TRI or SFI and were taught the 'fly-through' technique, If so please let me know. It would be handy to know the size of the problem.
G.
