Boeing (787) speed control and FMAs
Hi all,
Currently doing the B787 type rating (2 weeks in) having flown the mini Bus for nearly 10 years and I'm having lots of issues understanding Boeing FMAs and Automatic speed reduction (for the approach) concepts. Not helped by the fact that the FPT instructors have never flown the type before and perhaps do not fully understand some of the modes themselves. The choice of words used in the FMA confuse me (3 FMA columns vs 5 from Airbus) and the behaviour of the aircraft also seems odd and against convention. Of course, I'm being unfair here and realise I still have a bias towards my old type. Could I get the help of someone who has undergone an Airbus to Boeing brain transplant in an attempt to join things up for me?
In Airbus, we have the 'managed' speed, altitude and navigation concepts. The managed speed function (where the speed automatically reduces with each flap selection) can be engaged regardless of the vertical and lateral navigation modes as long as an approach has been 'activated'. Never will an Airbus automatically reduce speed to below a min flap manoeuvering speed by itself unless you have manually planted a low speed constraint somewhere against a waypoint (I think)
First question. On a B787 on approach, with the speed window closed and when in VNAV PTH, will flap selection always automatically reduce the airspeed to flap min maneuvering speed? What's the logic/condition it relies on in order to do this? One of the instructors was surprised by this behaviour. Is this new to the 787? (Airbus have had it since 1987)
Secondly, on approach, can't remember the FMAs but sometimes after crossing the F1, F5, Fx markers on the ND, the speed automatically reduces without any flap selection and we have to select flaps. A bit dangerous isn't it? I.e. to not get caught out you should have the speed window open on approach? Why doesn't it open by itself? Or have I totally confused myself here? I hope the FPT is reflecting the real plane correctly!
Thank you