G/S won't arm after go-around

[3-2-1-Now 126]

Hi, I'm able to consistently re-produce this. It doesn't seem to matter what I do before, but if I set up for an ILS approach (both boxes tuned), I press APP to arm LOC and G/S. It'll fly down the ILS no probs, until I get to DH. If I initiate a go-around (TOGA button assigned via CDU), **BUT DO NOT DISCONNECT THE FD OR AP** (select LVL CHG and HDG SEL at 400 ft RA), bring the aircratf around for another try, and press APP as before, only LOC arms (no G/S arm). The vertical mode remains ALT HLD. Anyone else able to confirm this behavior? The only way I found to fix it is to disengage the AP and turn OFF both FDs, then switch them all back on to get G/S to arm. This seems wrong. Best regards,Robin.

[henkie 0]

Hi Robin,I was about to make an topic about this as well. Obviously I have exactly the same problem. There is absolutely no way to get the GS armed again after a aborted approach. Speaking of which, did you manage to produce a well flown automatic go around? I tried it a couple of times but just after I press the TOGA button and raised the flaps to 15 the autothrottle throttles way back and the plane starts to "hoover" above the runway. Very strange behaviour. Kind regards, Daniel Verhaal

[Heffron 29]

The forum is acting strange. I think AP and F/D reset is needed to be able to capture the G/S again. This was also the case in previous 737 simulations.

[Spin737 102]

Not a normal behavior. You shouldn't have to cycle the FDs to get another approach. The A/P will of course disconnect on a single channel approach during go around.

[3-2-1-Now 126]

Hi, The way it goes around, as far as I can tell, is deliberate and not a bug. The 767 does a similar thing - it pitches to maintain 2000 ft/min. The reason is because the aircraft is light, and in a high drag configuration. It puts the aircraft in a shallow climb (1000-2000 ft/min) to enable clean-up, and a controlled transition to a high performance climb and/or turn. To just pitch up to the limits in the landing config doesn't enable the aircraft to be cleaned up without being rather uncomfortable. Once the aircraft has been clean up to the desired config, press TOGA a second time to enable the A/THR system to enter N1 mode and the aircraft to climb away. Best regards,Robin.

[henkie 0]

It shouldn't be hoovering a few feet above the runway and letting the airspeed to bleed off. You should press the ToGa switch only once for a 2000'/min climb and a second time if you need full power. Can somebody please try a automatic go/around to confirm this behaviour?

[Pat01 0]

Hello Robin,

Hi, I'm able to consistently re-produce this. It doesn't seem to matter what I do before, but if I set up for an ILS approach (both boxes tuned), I press APP to arm LOC and G/S. It'll fly down the ILS no probs, until I get to DH. If I initiate a go-around (TOGA button assigned via CDU), **BUT DO NOT DISCONNECT THE FD OR AP** (select LVL CHG and HDG SEL at 400 ft RA), bring the aircratf around for another try, and press APP as before, only LOC arms (no G/S arm). The vertical mode remains ALT HLD. Anyone else able to confirm this behavior? The only way I found to fix it is to disengage the AP and turn OFF both FDs, then switch them all back on to get G/S to arm. This seems wrong. Best regards,Robin.

It's really annoying. I can't fix it even disengaging the A/Ps (both CMD and A/P) and both FDs and get them all back on. Is this a bug or a b738 feature ? Am I missing something ? Patrick Didier.

[henkie 0]

Try to fly another ILS after going around. Still not able to arm the GS? Daniel Verhaal

[Cras 6]

One of my first flights I had to do a go around and I was also unable to arm the G/S, only VOR/LOC.

[Heffron 29]

Maybe the FMC resets the G/S On/Off option on the Landing REF page, where you set your final flaps and Vref, to off. If so, put it on again and maybe that works?

[Pat01 0]

That's right, I got it.After the GA achieved, as you fly at GA flight level for your second approach, just go to the fmc approach page and reset both vref and G/S (to ON) and G/S works again.Patrick Didier</p>

[BillC 135]

Had this issue yesterday and went in search in FCOM 2. Section 4.20.xx covers G/A procedures and the various options are well complicated and in some situations you do need to disengage the F/Ds! I suggest you fellas have a read for yourself because I'm going to have to read it again. Incidentally, one TO/GA feature is that after G/A your destination now becomes your origin (in the FMCs logic) in case you're diverting so, logic to me says, you need to treat your next approach as a "new" arrival and reset th relevant pages as if it were your first approach (i.e. teh VREFs etc). Interesting stuff!

[Pat01 0]

Bill, After your GA Just go to the fmc approach page and reset the G/S to ON. That's all. Patrick Didier

[dverha 0]

But should it work like this? I think you should be able to shoot some ILS approaches without touching the CDU except for setting the Vref's? I hope some expert can clarify this for us. Daniel Verhaal

[masneoquil 66]

The best way is to read the FCOM (by the way, these are the original Boeing ones, did you know that?)