Helicoptorial

One of the unique things about helicopters is its ability to pick up and place loads into remote areas. This article will discuss external load operations using a helicopter. The pilots of these types of operations concern themselves with specific questions when performing external load operations. They want to know the type of load, the drag that it will create, the weight, the conditions for pick up and set down, how tall are the obstacles in the immediate area, what the distance is between pick up and set down and how many people are involved.

LOAD IT UP

Dream it up and, if it's not too heavy, the helicopter can lift it. (Even a CH47D can get overloaded.) Loads can come in all sizes and shapes. Logs, air conditioners, towers, vehicles, and more. They can even be live cargo. (I've done some sling loading of mules myself.) Firefighters use water buckets hanging from helicopters to perform initial attack missions. Whatever type of load you are hauling, rigging and weight of the loads are very critical.

Some of us have felt that sick feeling when the load, for whatever reason, departs the aircraft unexpectedly. This could happen if the load was not rigged correctly. Remember the type of sling or clevis must be able to handle a far greater weight than the actual load. This is because the G forces on a load, increase its relative weight. An increase in G force can happen during climbs or turns. I hate to think of live cargo accidentally dropped. So prior to every load, ensure that a qualified individual reviews the load arrangement.

The weight of the load is also very important. Remember back from our aerodynamics, that a helicopter has to work harder to hover out of ground effect. Well (news flash) most external load operations are outside ground effect. Careful computation of performance data and weight and balance information prior to picking up a load is essential. Complacency from aircrews who thought they had performance without computing the data, has wound up wrecking an aircraft. Too much weight and the pilot could lose anti-torque capability, or worse droop the rotor. Losing rotor RPM is BAD.

WHAT A DRAG

The pilot must also be concerned with the drag that the load will create. A large flat load flies differently than a round load. Some loads can even have aerodynamic properties that can make them very unstable. This could be one cause of an oscillation. Once the load begins to oscillate, the pilot must try to stabilize the load. If the load is oscillating due to aerodynamic properties it is probably best for the pilot to slow down. (More on oscillations later.) For some loads, it is advisable to use a drag chute to help streamline the load to keep it from spinning. I've used a drag chute when slinging another helicopter and also when slinging the mule.

The drag profile will have an effect on the airspeed of the aircraft as well as power used. The more drag, the more power required. As you approach the maximum power available, the pilot has fewer options with regard to maneuverability. It's always best to conserve power.

CONDITIONS

Hot, dusty conditions are probably the worst. Because not only does the higher temperature limit you on power but the downwash from the rotor makes it extremely difficult to maintain a visual reference point. Hill tops or roof tops can also pose a problem because of the lack of visual reference points to help maintain your position over the load. At times like these it is a great benefit to have another crewmember on the aircraft providing guidance to the pilot for drift or altitude. In short anything that reduces your visual cues makes life more difficult. That's when good pilot technique helps.

OBSTACLES

Wires, buildings, towers, ridge lines heck just about everything can be an obstacle when there's a load hanging 100 feet or more below your aircraft. We must be ever vigilant to maintain awareness of where the load is above the ground.

OSCILLATIONS

I've found that the longer the line used, the easier it is for a pilot to experience an oscillation in the load. An oscillation is bad two big reasons:

1. Because controlling the load for placement can be extremely difficult.
2. A heavy load will feed back the oscillation to the helicopter making it difficult to control.

DON'T GIVE ANY STATIC

A load will build up static electricity as it is flown off the ground to the next location. Keep people away from the load until it has been grounded. A grounding rod may be used or touch the load to the ground. The electric charge is enough to knock someone to the ground.

IN SHORT...

There are three things to consider when doing sling loads; planning, planning, and planning. Know your power requirements. Know your limitations. Be smooth and positive and the controls. And always keep in mind the last resort; release the load. If an emergency occurs where the load is aggravating the situation, open the cargo hook. I don't advocate this unless it's to save the aircraft and its occupants. Experience and common sense under pressure are what is needed in these situations. If possible, set the load down first, then land the aircraft.

There are a million other things that I didn't go over when conducting external load operations. Next month I would like to go over a single mission step-by-step so everyone can get a little taste of moving a load.

Till then...Chuck

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