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Runway Weight Bearing Capacity


GSXR750Pilot
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There has been much debate among my colleagues as to using weight bearing capacity and whether or not it applies to helicopters. I fully understand how to read and decipher what it means so please don't go into that.

 

Keep in mind I fly a UH-60 Blackhawk, operating anywhere from about 16,000 to 19,000 pounds normally. We would be operating under the single wheel category when it comes to the weight bearing capacity. We regularly do "roll-on" type landings and take-offs, regular approaches to the ground, and of course ground taxi procedures.

 

My argument is that those numbers are derived based on landing aircraft touching down at a high rate of speed and rate of decent ultimately multiplying the actual force during touchdown. A helicopter on the other hand doesn't nearly touch down in such a capacity.

 

What are your thoughts on this? If you could give me some actual references to your findings, please share.

Edited by GSXR750Pilot
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Yes, weight bearing capacities (CBR, etc) apply to any aircraft operated on that surface. If you put your weight on the surface, the weight bearing ratio applies.

 

Remember that flex surfaces allow an additional 10%.

 

Also keep in mind that the weight bearing ratio dictum applies not only to runways, but ramp areas and taxiways.

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The weight bearing capacity is mostly based on the surface type and thickness along with the soil compaction prep prior to laying the surface. The worst, of course, is thin pavement on a hot day. I fly Apaches and some guys in my unit like to train at a little airport that we are too heavy for but they just land in the sod. Problem solved! Of course that doesn't work for roll ons.

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I would agree with the OP that helo set downs are more of a static load, than a dynamic one. In the rare case of a dual engine failure in your aircraft touching down on the same weight bearing surface would be much more like a fixed wing touchdown of an aircraft with the same gross weight, if not more so.

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Weight bearing ratios take into consideration the weight of the aircraft divided by the number of wheels on the ground. Touchdown rate certainly impacts the loads transmitted to a landing surface, but fixed wing aircraft don't tend to land like a fighter on a carrier.

 

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Most of my fixed wing landings are fairly imperceptible, as they should be. The descent rate is minimized to near zero as a function of making a landing.

 

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Weight bearing ratios, such as the California Bearing Ratio and other measures (ACN-Aircraft Classification Number or PCN-Pavement Classification Number), apply to the aircraft weight; don't make the mistake of thinking it doesn't apply because your'e in a helicopter. ACN/PCN are applicable based on weight and type of landing gear.

 

Most helicopters don't approach weights that are a concern for the majority of runways for which weight limits are prescribed.

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  • 9 years later...

From the AFD, RE Weight Bearing Capacity: “It is not intended as a maximum allowable weight or as an operating limitation.” Call the airport manager and ask them for permission if you’re over the weight listed. It’s not always a yes or no, and is certainly up for debate. Looking in the FIH, Blackhawks and Apaches etc. are not even listed in the library of ACN aircraft. We’re also allowed to land on taxiways and non-movement areas, which aren’t built to the same standards as runways, so it’s definitely worth talking about.

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  • 1 month later...

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