UAV landing load factor
UAV landing load factor
(OP)
I have to design a forward looking camera gimbal to be mounted on the nose of a UAV. How would I go about calculating the load factor experienced by the vehicle during landing?
I am sure the landing load factor would be much higher than any loads experienced during manouvres, is this a valid assumption?
I have heard load factors up to 16 g's are possible, does this sound exessive or plausable?
The vehicle is to have skid landing gear which will be built as to absorb some of the landing shock, the gimbal will also be mounted on rubber grommets or something similar to absorb shocks, but I am looking for a worst case scenario.
Thank you in advance.
I am sure the landing load factor would be much higher than any loads experienced during manouvres, is this a valid assumption?
I have heard load factors up to 16 g's are possible, does this sound exessive or plausable?
The vehicle is to have skid landing gear which will be built as to absorb some of the landing shock, the gimbal will also be mounted on rubber grommets or something similar to absorb shocks, but I am looking for a worst case scenario.
Thank you in advance.
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RE: UAV landing load factor
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RE: UAV landing load factor
assume a static attitude,
assume a sink rate (10 fps is a common assumption, for limit load)
this leads to a ground contact force (or assume a reaction factor, =2?)
this gives you the pitch moment of the landing
with the pitch mass moment of inertia you can get the aircraft's rotational inertial reaction, "alpha ddot"
and this leads to the linear accelration at the station in question, z ddot = alpha ddot*distance
and divide by 384 (assuming inches for distance) for g's
Quando Omni Flunkus Moritati
RE: UAV landing load factor
RE: UAV landing load factor
It is quite difficult to predict the loading from a skid landing. The X-15 suffered a structural failure during its first landing using a skid. The same thing happened with the Boeing Phantom Eye UAV.
RE: UAV landing load factor
Asking for the g-load factor is asking the wrong question in landing gear design.
STF
RE: UAV landing load factor
MichaelkSA, depending on market customer is there a relevant Mil Std or similar to look at?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: UAV landing load factor
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: UAV landing load factor
There is a significant difference between landing and crash loads. UAVs rarely worry about manned crash loads... no one to protect. Maybe OEM/customer requirements for damage limits [rapid repair/return to service] will define strength for crash-worthy UAV structures and systems.... or element replacability.
Landing loads are usually defined by weight/CG/max sink-rate/assymetry... then these CG centric force-generating elements are translated to the XYZ off-set location of the component.
CAUTION. Sometimes landing/takeoff/taxi loads on rough/harmonic surfaces can create peculiar loads with forcing functions that drive internal structures and systems loads sky-high.I have personally dealt with a scarry C-130 incident: acft flew with internal damage to both outer wings, discovered on post-flight. Cause? rough taxiiway, perfect [worst] taxi-speed, and max fuel load W/O cargo. Double outer wing change was mandatory before next flight. I understand that certain Cirius [single engine composite aircraft] have actually buckled the aft fuselage due to Taxi conditions.
Regards, Wil Taylor
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RE: UAV landing load factor
RE: UAV landing load factor
Not by spec, typically. The assumption is that the body is a rigid structure, so loads are directly carried to the payloads. Only on rare instances do we get any indicating that the loads are attenuated by the structure, and that's usually only because the payload is heavier than what was used in the data collections.
Of course, this is caveated by the useful life of the aircraft in some cases. We have a UAV gimbal that's designed specifically for bout 1000 hrs of operating life, because the platform will either be shot down or crash, on average, in that time frame.
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