G load determination after touchdown

[Aleksej]

Dear All,

does anybody know if it is possible (through MCDU) for the pilot to determine actual G acceleration at touchdown after landing? I know that according to Airbus information, if G Load is more than 1,4G it should show G load value on SD lower line (above clocks).

Thanks in advance.

[kijangnim]

Greetings,
For which type of aircraft

[Antunes]

A320 Family

MCDU Menu > AIDS > Parameter Call-up> Alpha Call-up

Then type VACC and insert it. It should give you the vertical acceleration in G's

Nice to do once, but it's better to monitor the basic flight parameters to check that the PF is doing fine instead of monitoring G's

[john_tullamarine]

Regardless of the smoke and mirrors, a main problem with data capture revolves around matching the sampling rate against the time history of the event .. if the sampling rate is too slow (which will be the usual case for touch down G) the captured data has to be normalised to give some insight into the "real" happenings ... either way, if the reported value is somewhere near a limit, then it should be interpreted with some caution.

[Capn Bloggs]

B717 (Honeywell)

MENU>ADAS or ACMS>ALPHA>ALPHA Display, then put VGTD into the boxes.

John Tulla - true! Good for bets against the FO though.

[kijangnim]

Greetings,
JOHN is right the recording of the G landing can or cannot be the creal one, we had cases of hard landings (above 1.4 Gs) that were never shown on the system ,on the other hand firm landings were recorded hard
The nose wheel dropping hard on the runway is not recorded

[Ipaq]

Airbus family - via CFDS, a Load 15 report can be created showing G at touchdown, but the methods of getting it are varied due to software - engineers will know how!

[krujje]

does anybody know if it is possible (through MCDU) for the pilot to determine actual G acceleration at touchdown after landing?

Not very useful information, unless you know how to interpret it. In my experience, pilots don't know how to correctly interpret landing 'g'. Some of them do develop a seat-of-the-pants feel, though. But if you've done enough hard landings to have that "feel", then either you're a test pilot, or...

Regardless of the smoke and mirrors, a main problem with data capture revolves around matching the sampling rate against the time history of the event .. if the sampling rate is too slow (which will be the usual case for touch down G) the captured data has to be normalised to give some insight into the "real" happenings

Not only sampling rate, but also filtering. The accelerometers in some aircraft have roll-offs around 4Hz, which means you're losing some of the signal in a hard landing (yes, even if you had a million samples per second). Check the specs for those dedicated FDR accels... you'll be surprised at what you find.

The nose wheel dropping hard on the runway is not recorded

Not necessarily true. You have to know what you're looking for.

With the variety of folks tracking FDM (aka the old FOQA), and better methods of data exchange (NTSB still sells the old tabular-data tables which will total in excess of $100 for about 30 seconds of data), and various products for analysis (FlightScape’s Insight), it seems that the investigative authorities could agree upon better methods for analysis of “ARC” [hard landing] mishaps.

Better methods have been developped, but they're aircraft specific.

[Aleksej]

Thanks to all!