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# Landing Gear Design and Ultimate Load

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## Landing Gear Design and Ultimate Load

(OP)
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?
Replies continue below

### RE: Landing Gear Design and Ultimate Load

(OP)
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?

### RE: Landing Gear Design and Ultimate Load

Hi,

You are right. Maybe JAR 25 (see www.jaa.nl) will give you some answers (starting with JAR 25.473).

Regards
Fernando

### RE: Landing Gear Design and Ultimate Load

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

### RE: Landing Gear Design and Ultimate Load

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/ )

Regards
Fernando

### RE: Landing Gear Design and Ultimate Load

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:

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.
25.511   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

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