I'm not going into details, just trying to have a discussion about avoiding mis-manipulation of a/c systems in stressful/startle scenarios.
It has been mentioned many time that one common screw up is an all engine GA. People have said that a manoeuvre brief will solve many problems. Hm? Briefing something you do rarely, 30mins before you might need to do it, is not a guarantee of success. It might help, but.......What can help is if the manoeuvre is simple and familiar to another common manoeuvre. This was the case with a normal GA & takeoff of B757/767. We executed both the same. Now, on B737 CL/NG I was astonished to discover that the GA is very different to takeoff: you accelerate during flap retraction via the flap lever. This is the only manoeuvre where this happens. I am still searching for a good reason why?
To make things worse there are some operators who emphasise that flap retraction must start at 400'. So they have the GA call, initial action of thrust, flaps, gear, roll mode all coming in very close succession, and then, just to increase the workload even more they have to accelerate the a/c and retract the flaps using a method they rarely practice. What's the rush, and why design the system to be so different to a normal takeoff?
Every other time we take off, be it normal or with engine failure, we accelerate at 1000'. A SE GA is 1000': in all cases the a/c is accelerated via MCP speed bug. Why make the all eng GA so different?
What happens on other Boeings? Is this now a common company technique? I realise this is not connected directly with DXB accident, but it does seem this can have human factors elements to the root cause.
On B737NG the AT disengages 2secs after touchdown. I assume this is 2secs WOW and not a bounce. It doesn't say if it's both wheels or one. On B737NG the only time you'd land with AT engaged is an autoland. It would be possible to still make a GA, but TL's would need to be pushed manually. In all my various Boeing airlines B575/676/737 the GA SOP was PF to follow through TL's and PM verify thrust, even on a GA with AT engaged. This would happen from an autopilot approach. The autopilot might disengage, or not, but AT 'should' advance to a suitable GA thrust. Perhaps because we flew more manual approaches, certainly in the latter stages, manual thrust was in our 'instincts & muscle memory'. It also improved, sharpened and widened our scan. We flew 1 handed on each control and were aware of the thrust setting.
I admit I had forgotten this performance, or lack of, of the AT after touchdown. It had never been trained nor experienced. However, because the technique was for PF to always follow through the TL's, just as on takeoff or any other GA, I would not expect it to have been a problem. Thrust would have been advanced.
I wonder if Boeing FBW AT pilots cover TL's or just trust, and only place hands on for TOGA selection? (I hear an AB GA is initiated by manually fire walling TL's, but do you cover them on approaches?)
I just wonder if this automated system is the best it can be, is a real safety improvement or needs tweaking.
Last edited by RAT 5; 19th Sep 2016 at 11:27.