Figure 28-1: Marshalling Signals for Helicopters
All external loads may be categorized as one of: high density, low density or aerodynamic. The high-density load will be stable while the low density will be decidedly unstable; the aerodynamic load may exhibit both characteristics. You should study the load to determine which description best suits it, and then estimate how it will likely fly.
PICKING UP THE LOAD
Whenever possible, position the load so that you can hover the helicopter into wind during the pick-up procedure. This will provide for the most stable hover. If assisted, the marshaller should be positioned in plain view, back to the wind. Usually this will be slightly right of directly in front of the cockpit, about 50 feet away from the helicopter. This position will allow the marshaller to monitor the load as it is lifted off the ground, and to observe a wide area around the helicopter in the interest of safety. It will also make sure that the pilot can see the marshaller. Once in the hover over the load, at the appropriate height, select some easily visible references. Keep these in view as you increase the hover height after hook-up to maintain as vertical a liftoff as possible.
During the hook-up, ground personnel should not position themselves between the load and the helicopter; include this point in your pre-flight briefing. Once the load is attached to the hook, you may commence a slow vertical ascent until the sling becomes taut and the helicopter is centred over the load. Brief the marshaller to position the helicopter directly over the load once you have lifted into the hover. Continue increasing collective while crosschecking the manifold pressure gauge (or torquemeter on turbine engined helicopters) to determine whether sufficient power is available for the transition to forward flight. This portion of the takeoff should be made smoothly to ensure that the load is secure and properly rigged prior to the transition.
THE TAKEOFF
Once you are satisfied that all criteria have been met for flight, initiate an altitude over airspeed transition to forward flight. This type of takeoff will ensure that obstacle clearance is achieved rapidly. When at a safe height, allow the airspeed to increase slowly to a speed that will allow the most control over the load. Check for limitations in the flight manual, in any event it is of little advantage to fly faster than 90 mph with any sling load. As the speed increases, pay attention to the flying characteristics of the load and, should oscillations begin, smoothly reduce the airspeed. In this way, you will establish the maximum safe flying speed for your load. Once safely into forward flight, select the cargo hook master switch to “off” (if your helicopter is so equipped).
It is important to reduce the airspeed at the first sign of an oscillation, but do not lower the collective rapidly. All control inputs should be gentle and smooth. Reducing collective (and thereby airspeed) and entering a shallow bank has often proven effective in reducing load oscillations.
APPROACH TO RELEASE POINT
If at all possible, plan your approach into wind to preclude the possibility of entering a situation where there is insufficient power available to arrest the descent. An approach angle slightly steeper than normal will ensure that obstacle clearance is provided until the helicopter is over the load release point. Attempt to “fly the load”, observing its speed over the ground, to avoid overshooting the release point. Perform a pre-landing check and set the cargo hook master switch to “on”. Control your rate of descent.
RELEASING THE LOAD
When the helicopter has stabilized over the load, smoothly lower the collective to begin a controlled rate of descent, until the load is on gently placed on the ground. Further lower the collective to create slack in the sling. Depending on the weight of the load, there may be a considerable reduction in collective at this point. Once the sling is slack, release the hook. Before clearing the area, verify that the load has in fact released, and the sling has not hung up, by checking in your mirror or moving a little to one side.
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