A330/A340 landings at 12ft/sec

[Snigs]

For all of those big bus drivers out there I have a question. I’m currently involved in developing an “Enhanced” version of the wing landing gear bogie pitch trimmer. As an ultimate case I have to stress the trimmer for a landing at 12 ft per sec.

I understand that a “normal” landing is about 3 ft/sec, but I don’t actually have a feel for how heavy 12 ft/sec is. Can any of you put a description of what would count as an “uncomfortable” landing, what would be a “scary” landing, what vertical speed would “release” the oxygen masks for example.

I guess it’s company specific, but what vertical landing speed would you require an undercarriage inspection?

Thanks if you can help!

[scroggs]

12 ft/sec is 720 ft/min, which is approximately the rate of descent of a stable 3-degree approach. A landing without flare (which is effectively what you're talking about) would certainly rattle your teeth, and would have O2 masks deployed, passengers rather upset, and the galleys in a total mess!

I can't remember the specific RoD on landing that requires a heavy landing check (the aircraft would prompt the engineers in any case), but I'll check at work tomorrow.

[mjv]

from an engineer point of view, I would be slightly disappointed and you might have to write a couple of reports!

I do not have the accurate 330/340 figures and you have to consider the LD weight as well!

anyhow, 12ft/s that's a hard landing for sure (e.g. A321 below MLW 10 to 14ft/s)

to have the right picture we have to know:

landing weight
touch down config (nose/taildown, straight ......
fuel quantity
DFDR readout.....


it doesn't matter if it was a (severe) hard langing or (severe) overweight landing, you have to inspect the whole fuselage (painting, loose fasteners, panels....), wings (fuel leaks), primary and secondary controls, LDG, pylons and so on.

it's not an easy task and it might take a couple of days!!

mjv

[mjv]

A340:

less 155tons, max 10ft/s
more 155tons, max 9ft/s

the inspection is more or less the same, three phases:
phase 1, "only" GVI without depaneling
phase 2, if findings get access
phase 3, not funny, removing stuff LDG.....

mjv

[northwing]

As a guide I always reckon:-

0-3 ft/sec is a greaser (pax won't notice)

3-6 ft/sec is normal

6-9 ft/sec is firm (pax will groan and shriek if nervous)

9-12 ft/sec is heavy

and anything over 12 is broken.

I don't know what the regs demand but I am pleasantly surprised if Airbus are designing to 12 ft/sec as I thought most civil aircraft were designed to 10 ft/sec. It may be that their 12 is an ultimate figure rather than a design one. Certainly the only aircraft that would be designed to more than that would be trainers(ham-fisted students) or naval aircraft (runway moves upward as you move downward - painful.)

[4MONU]

I work with Boeing aircraft, but I guess it works the same:

'g' values picked up on the DFDR are great, but not an accurate way to determine a HARD LANDING. (multiple points on the A/c are monitored for 'g' values at any given time). We have had cases in which the crew thought they broke the A/c, but DFDR showed just a firm 'g' value, and also the otherway around sometimes.

As per correspondence with Boeing, they best way to initiate a hard landing inspection is as per the Pilots report. This being that there are a lot of external forces that play also, and not just vertical speed !

Boeing has different values for certification on vertical speed, but these are weight dependant, as certain Boeings are certified to land upto their Take-off weight.

[Snigs]

northwing, the 12 fps is indeed an Ultimate case, the 10 fps is a limit case, but they both have to be designed for.

It's interesting that you put 3-6 fps as "normal". I won't be specific as I could be compromising "sensitive" information (if I haven't already in my original post :oh: ), but the fatigue case I design to is between 3 and 6 fps. The hydraulic pressures induced are pretty damn high even at these "normal" landing speeds.

However, before you start getting worried, nearly all components are cleared for infinite life.

Thanks for the insight.