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How would a helicopter deal with auto rotation when it has a payload? Will it deploy it's payload and continue with auto rotation as normal? Can't find much online, this research is for my senior design.

Helicopter with a payload

Any help would be greatly appreciated. If you can give me something to read and learn further for myself, that would also be great.

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  • $\begingroup$ Interesting question; increased potential energy to convert into RPM may be useful in some situation (which one?) during the procedure. $\endgroup$ – qq jkztd Oct 17 '17 at 15:51
  • $\begingroup$ According to the video's I've seen, an auto-rotation with a slung load is pretty much impossible at the altitudes/speeds they would be flying at. $\endgroup$ – Ron Beyer Oct 17 '17 at 21:32
  • $\begingroup$ Can you get a friendly Part 133 (or your country's equivalent) operator to provide their Rotorcraft Load Combination Flight Manual (RLCFM) or equivalent document? It should cover their procedure for auto during vertical reference (external load) flying... $\endgroup$ – UnrecognizedFallingObject Oct 17 '17 at 23:45
  • $\begingroup$ Thank you all for your kind responses. We spoke to the sponsor of our project and arrived to the following conclusion: "A vehicle as this would require multiple engines". Dropping the load would not be an option as our theortical mission would have us flying over densely populated areas. They also mentioned dropping a load of the size we are transporting would lead to wreck (because of center of gravity). @UnrecognizedFallingObject $\endgroup$ – Alexis Moreno Oct 30 '17 at 21:40
  • $\begingroup$ @AlexisMoreno -- Autorotation procedures are still needed in multi-engine helicopters (due to say transmission trouble) although you are correct that external load missions over densely populated areas do require a multi-engine helicopter $\endgroup$ – UnrecognizedFallingObject Oct 30 '17 at 23:16
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In theory, with that load, the rotor revs will be higher during the descent, and releasing the load just before flaring will give the pilot more rotor energy to control the aircraft with the collective in the last stage of the landing.

But it would be more prudent, in my opinion, to release the load as soon as possible. After all, in any dead stick landing, the lighter the aircraft, the better...

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    $\begingroup$ Yeah, my first move would be to hit the "bye bye" knob on the hanging load. $\endgroup$ – zeta-band Oct 17 '17 at 16:44
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    $\begingroup$ Keep in mind that there are operations (power line maintenance, heli-rescue) where your hanging load is a human being. Dumping them on the ground from altitude might not be so healthy for them! $\endgroup$ – UnrecognizedFallingObject Oct 18 '17 at 0:01
  • $\begingroup$ @UnrecognizedFallingObject Autorotation usually isn't possible below 700 feet AGL, I'm not sure what power lines or rescue's are above 700 AGL. At the 100-150' AGL that most power line/rescue operations take place at, personally, I'd rather take my chance being dumped than having a helicopter land hard on top of me. $\endgroup$ – Ron Beyer Oct 18 '17 at 4:25
  • $\begingroup$ @UnrecognizedFallingObject Do you actually transport people in a net using the cargo hook as an external load? $\endgroup$ – KorvinStarmast Oct 18 '17 at 17:31
  • $\begingroup$ @KorvinStarmast -- look up Class B Human External Cargo if you want the technical term -- it'll be a harness system that attaches to a line of some flavor or another :) but the exact system is unimportant from the "what to do in an auto" standpoint $\endgroup$ – UnrecognizedFallingObject Oct 18 '17 at 22:20
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From the Operator's Manual of UH-1D/H, which are single engine helicopters:

9-13 Engine Failure - Low Altitude/Low Airspeed, and 9-15 Engine Failure - Cruise both describe the procedures for establishing autorotation. Both refer to jettisoning external loads, for instance 9-15:

When engine failure occurs during cruise flight, proceed as follows:

  1. Collective pitch - Adjust as necessary. Establish auto rotational glide.
  2. External stores - Jettison as appropriate
  3. Land

For civil helicopters in the USA, external load operations are covered by 14 CFR part 133, which defines several classes of external loads and the operating rules for certification. In order to be certified the helicopter operator must provide a Rotorcraft-Load Combination Flight Manual (RLCFM).

An example of an RLCFM is found here, it does not contain any special procedures for autorotation upon engine failure. References to Long Line Operations in an R44 for agricultural activities are found here.

Autorotation upon engine failure and carrying an external load are high workload situations with a higher than normal inherent danger. Combining the two is not a good idea: FAA AC 133-1B specifies that the emergency release mechanism of the external load must be demonstrated before certification.

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Generally last minute configuration changes have adverse outcomes as the aircraft configuration creates instability which impacts judgement and the ability to perform maneuvers, such as auto rotation.

With sling loads there are added complications which include:

  • ground crew likely in harms way
  • higher lift requirements (impacting rotor loading and stored energy requirements)
  • adverse handling due to the "flexible" coupling between the load and the aircraft
  • normally low altitudes for sling loads
  • many loads cannot be quickly shed

I have not been specifically trained for sling loads, but I believe that the decision will first be influenced by altitude, then payload weight, then type of payload and release mechanism (if any), etc.

For your project, you might try to get some Army training materials, and I would search the journals and magazines for articles. The company "doctrine" will change depending upon the business, the region and the regulatory agencies involved.

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