Landing Gear Design and Ultimate Load

[yshij]

If there are drag and vertical loads acting on aircraft wheels, what is the design and ultimate standards/limits for civil aircraft? Are they usually 0.8g in drag and 1.5g in normal?

 

[ferdo]

Hi,

As I already post previously, a useful link to check is

http://naca.central.cranfield.ac.uk/results.php?Simplequery=landing+gear+design&st=AND

Regards
Fernando

 

[yshij]

Ferdo,

You might misunderstand my question. My questions were about landing gear structure strength to ground loads (drag/friction, normal/vertical). When we design landing gears, what are structure strength (design and ultimate loads) standards/limits?

 

[ferdo]

Hi,

You are right. Maybe JAR 25 (see

http://www.jaa.nl)

will give you some answers (starting with JAR 25.473).
Regards
Fernando

 

[eezworf]

If I understand your question, then the answer (in Canada and the US) is the limit and ultimate loads are determined through drop test. Using an effective weight the appropriate portion of the gear is dropped from a height based on wing loading. This substantiates the strength (except fatigue) of the structure. By instrumenting the drop test assembly with an accelerometer the resultant inertial loading can be determined. Loads for the rest of the aircraft structure are then based on this value. A relatively simple description of the process can be found in the older regulations (CAR 3 for instance). Typical values are in the 3-4 g range

Hope that helps,
Dave Pasquill, P.Eng

 

[ferdo]

Hi,

If you want more details, you can consult:
- FAR, VOL 3, Part 25 - AIrworthiness Standards Transport Category (see

http://www.jaa.nl/section1/jarsec1.html)

- British Civil Airworthiness Requirements, Section D- aeroplanes
- MIL-A- 8860 (ASG) - General specification for airplane strength and rigidity (see

http://astimage.daps.dla.mil/online/new/

)

Maybe these will help you. Regards
Fernando

 

[Tads]

Hi,

It depends if you are talking fixed/rotary wing, as well as what level of certification you will be seeking.

A good start is FAR 25, which is very explicit in undercarriage design requirements (and it's definitely not just a drop test!).

An excerpt of the requirements are here:
GROUND LOADS

25.471 General.
25.473 Landing load conditions and assumptions.
25.477 Landing gear arrangement.
25.479 Level landing conditions.
25.481 Tail-down landing conditions.
25.483 One-gear landing conditions.
25.485 Side load conditions.
25.487 Rebound landing condition.
25.489 Ground handling conditions.
25.491 Taxi, takeoff and landing roll.
25.493 Braked roll conditions.
25.495 Turning.
25.497 Tail-wheel yawing.
25.499 Nose-wheel yaw and steering.
25.503 Pivoting.
25.507 Reversed braking.
25.509 Towing loads.
25.511 Ground load: unsymmetrical loads on multiple-wheel units.
25.519 Jacking and tie-down provisions.

Check here for the full FAR references:

http://www.access.gpo.gov/nara/cfr/cfrhtml_00/Title_14/14cfrv1_00.html