Its a pretty simple concept. If you are on an arrival with crossing restrictions, before you reach your top of descent, dial in the lowest crossing restriction. Or commonly referred to as your bottom alt. VNAV will take over the rest of the way. As far as spd brakes are concerned. The vnav isnt perfect. You will need them at times.

My usual method is to change the altitude setting in the MCP with the GSIA and press the selector BEFORE T/D. This is possibly removing some pre-programmed constraints/restrictions, which is why I probably have to play catch-up to get the right speeds at the right altitude, usually done with V/S.

 

This may be off topic, but what makes you decide whether to use V/S or FLCH to correct your descent?

 

 

but what makes you decide whether to use V/S or FLCH to correct your descent?

 

V/S is a vertical speed priority mode. The aircraft will pitch for vertical speed and then airspeed will be the problem of the autothrottles. Airspeed can then be "controlled" by adjusting thrust or using drag. The "mistake" many people do is set a descent rate of 2000 fpm and then expect the aircraft to keep the target airspeed, or even worse, slow down!

 

FLCH is an airspeed priority mode. The aircraft will pitch for speed and accept the resulting vertical speed. Vertical speed can then be "controlled" by adjusting the thrust setting or adding drag (speedbrakes).

 

Depends on what your priority is at any given point. As a "rule of thumb" (and remember, there's NO rules of thumb for descents, haha), FLCH is good for initial descent down to just before the IAF and V/S is good past the IAF for step descents and approach control.

After the Asiana accident in SFO a few years back it has become commonplace to avoid using FL CH under 10000 feet. When the swiss cheese holes line up, you will get the accident that happened in SFO. I usually use V/S under 10000 feet.

Hi Damian,

 

In your original post you mentioned trouble performing manual landings as well- although you did mention you use the FUNCTION keys for throttle control, I'm not certain what joystick you are using as your main input device.  Assuming you are indeed using a joystick of some sort I recommend using control sensitivities that are quite low; for me adjusting the sliders to the (very) low end made the plane much more "hand flyable" and more accurate.

 

Good Luck!

 

Mark Trainer

There is no reason to avoid using FLCH as a result of the Asiana accident. V/S is less well protected and might well open up a wider hole through the swiss cheese. Choose the best mode for the circumstances.

There is no reason to avoid using FLCH as a result of the Asiana accident. V/S is less well protected and might well open up a wider hole through the swiss cheese. Choose the best mode for the circumstances.

 

Completely agree!

 

I take Xander's comment as an "extension" of what I said above that FLCH is better suited for the initial descent and V/S for the late descent closer to the airport. But of course, each mode is to be used when suites best given the situation.

 

For the curious, more info on the Asiana accident in this thread.