Monitoring TouchDown G Load on B737 with ACMS

[Young_Turk]

Hello All..
Now on B737 a/c equipped with ACMS page on FMC menu key, we can have a fair idea of G Load detected on touch down phase. Here's how
Menu Key
ACMS
Alpha Menu
Alpha Menu Display
in the box prompts...type VGTD
and on the right of VGTD...Wolla...you get your Max G Load Readout.

But I do wanna know where i can read more about ACMS prompts, What all can we get out of this by typing different V-Codes in the box prompts.

Does anyone know other Codes for ACMS on Boeing 737?
Please share with us....

[lederhosen]

My co-pilot impressed me with this little trick last week. I am not for a moment advocating starting a little competition here to see who had the softest touchdown. But it made this slightly older pilot smile that the traditional 'nice landing captain' routine was backed up with some evidence.

[Young_Turk]

you're quite true!! everyone does like flattering numbers!

but i'm on the hunt for other codes.... anyone knowing more about these codes? because there are 8 pages of box prompts one can enter codes in....... makes you wonder :cool:

[Denti]

Search a bit around in the ACMS, it has a list with the codes somewhere (not a description of them though).

And the VGTD sometimes isn't right, had one of 0.7g once :)

[cmcjma]

Boeing says that the VGTD should be used with caution.
As matter of fact a landing is made of longitudinal, vertical and lateral forces.
VGTD, even though related to the vertical sensor, is not a correct measure because it is distorted by the other forces.
VGMX gives you the lateral Gs. I am still looking for the longitudinal force code, which is measured by the QAR, so it exists…
It is quite difficult to make less than 1.2, I did it just a couple of times only. But maybe I am not a good pilot...
Sometimes you have displayed 1.46 but your (vertical) landing was not as hard… Just because it was distorted by a much stronger lateral force. The longitudinal is always important because the speed of the plane at touch down.
Usually, above 1.6, you trigger a soft QAR warning, and above 1.8 a hard QAR warning, and it the limit from which is considered a hard landing by the manufacturer.
Anyway, you may use VGTD but with caution, only for information.
If you wish more, you have PTRM, that gives you the precise settings of the trim, and FLAP that provides the positions of the LE Flaps and Slats, and the TE Flaps.
Besides that, I am also looking for a list of all the possible codes to be used with ACMS pages.
Fly safe

[Miles Magister]

I agree with cmcjma, accelerometers and fatigue meters do not read landing forces. I once had it explained to me by an engineer who was good at big sums, suffice to say that a landing it jolts the instrument rather than registers a reading.

I also believe that a really gently landing is not a good one, the aircraft should be placed down smoothly by positively to ensure friction once the flying surfaces become less effective.

[whiteknuckles]

I am still trying to find an engineer who will dig out the codes for me but the ACMS on our aircraft will 'auto-suggest' codes ie simply enter 'H' into a line and it comes up with the hydraulic pressures. OK, so you already know those but it passes the time entering random letters and seeing what it comes up with.
Re Touchdown G, there seems to be little correlation between how hard the touchdown feels from the flight deck and the subsequent ACMS readout In fact, the reverse seems true. If I had to guess I would say how hard you flare has as much influence on the reading.
Certainly, having watched several people about to sail past the end of the touchdown in search of 'good' ACMs readout, I wonder if there is a flight safety risk involved?

[Golden Rivet]

I've got the 737-800/900 ACMS mnemonic list. Only problem is, it's a 51 page pdf.

[FlyBoyFloyd]

Theres the standard VGTD, VGMX, and heres another. STAR. If it throws up NO EXCEEDANCES I guess youre ok...

[whiteknuckles]

I would still like a copy if you are up to sending it:O

[frontlefthamster]

You don't need an engineer who's good at sums...

The accelerometers fitted to aircraft in line service are there to measure flight loads, not to assess the landing. Aircraft are instrumented quite differently for landing performance testing. While accelerometer data is of use, it's by no means a reliable evaluation of the landing.

As UK CAA FODCOM 21/09 says:


The primary trigger for a hard/heavy landing report should be the subjective evaluation by the aircraft commander.

And as for mucking about doing soft landings, all well and good in the right place at the right time, and by the right pilot, but I don't half get nervous when travelling as a passenger if the thing isn't delivered at the right speed in the right place, and firmly.

[slings]

I think VACMAXLA can be entered in the mnemonics page.
Should give the highest recorded G force during landing......

good luck!