747-400 Go-around?
 

I'm curious to know how GA's are handled on this aircraft, particularly the transition from climb-out to acceleration on the flap-speed schedule?

I understand that at the end of a flight, with little fuel on board, a 747 will be fairly over-powered. One "click" of the TOGA switches is the norm to give a climb-out of 2000fpm, correct? Now, how do you go about accelerating?

Surely, if you choose FLCH, you're going to end up with a very fast rate of climb, followed by a rapid pitching over to halt at your missed approach altitude? On the other hand, will selecting V/S give you short sharp accelerations as you advance the speed bug to each limit on the flap schedule?

I hope this makes sense? :confused:

TOGA, Flaps 20; 400': LNAV; 1000': VNAV

The missed approach procedure is programmed in the FMS. If the ILS is coupled at the time, the airplane does all the work. If not, follow the FD. VNAV will program the acceleration.

FLCH tries to attain the set altitude in 2 minutes; THRUST REF if unable.

At 1000' set speed Vref 30 + 80, accelerate and retract flaps on schedule.

For clarity thats 1000' AAL............:ok:

A Go-Around is just a Take-Off that starts at 200ft !
It's always a bun fight because we never prepare for a Take-Off when Landing!:uhoh:

PRGU - "positive rate, gear up" is also recommended.

The reason for my question is because I've been practicing a few proceedures using PMDG's 744 simulator and a G/A is the only thing that seems totally unmanageable. It's probably just down to a lack of realism, but here's a clip of my attempt.

PMDG 744 Go-Around

Everything seems ok until 1000ft when I select VNAV. Watch the speed tape, is this a bit excessive?

VNAV doesn't know it's a go-around, so it will accelerate to optimum climb speed (limited to 250 KIAS or V2+100 below 10,000'. After selecting VNAV, open the speed window and set it to the 200 or 210 Kt you want as you're retracting the flaps to 1 or Up.

Looks like a fairly normal acceleration and level off to me, although I couldn't comment on the AFDS mode selection because I don't fly the B744.

As an aside, if you're flying a missed approach in the U.K., the maximum IAS for the procedure is 185kt, so I guess you would need to maintain a flap setting that would allow you to fly at that speed.

Looks like you manually selected Vnav to accelerate, and ended up with a Thrust increase (note FMA change from THR to THR REF). :eek:
Many 744 operators advise either selecting FLCH and an appropriate speed, (usually Vref30+40 or Vref30+100) at acceleration altitude (typically 1000ft AAL) to achieve acceleration, or selecting V/S and a suitable speed. If using V/S it would be 'normal' to leave the pitch mode in TOGA until the FMC has commanded acceleration (at pre programed altitude) and a suitable pitch attitude is already achieved. This is simply for pax comfort.
A word of warning mind, leaving the Beast in TOGA for pitch until altitude capture will result in an acceleration to Vmo/Mmo/ Flap limit speed as you will still be in THR (or THR REF if you pushed TOGA twice).

Ok, I'm a bit confused (doesn't take much :confused: ).
Do you mean that in the real aircraft VNAV will engage automatically during a G/A?
But surely FLCH will give you THR REF too, or am I wrong?
I thought that V/S was a pitch mode. Do you mean that you should select V/S and leave the thrust mode in TOGA. How is this possible, won't the MCP automatically select SPD if you choose V/S? :{ :{

No, it's just that your video footage only shows a PFD, so I have to presume you pushed the VNAV button on the MCP when I see the FMA change from TOGA to VNAV.

FLCH will give an autothrottle mode of THR, THR REF, IDLE or HOLD as appropriate. In the case of a G/A it should set an appropriate thrust (approx 1.65EPR on RR RB211's) to achieve the level change in 2 minutes or 2000 ft per min. I would never expect the Thrust to drastically INCREASE at acceleration altitude as it appears to on your video. (It would give THR REF if you dialled in a large altitude change (say 45,000ft) in the ALT SEL window, only because the A/C then wants to achieve a rate of climb to get from your acceleration alt to 45,000ft in 2 mins)

Yes V/S is a pitch mode, but so is TOGA. I was alluding to the fact that in TOGA with an acceleration altitude programmed into the FMC the aircraft will reduce pitch and begin to accelerate (still remaining in TOGA). Some operators wait until this acceleration has begun and THEN select V/S.

Thanks banana head!

Very grateful for your explanations, crystal clear now! :)