by Patrick Lafleur, Bell Textron test pilot, leader of the Rotary Wing Working Group (RWWG)
This is the first of a series of articles on the typical dangers for helicopter pilots. In this series, we will explore the risks involved with takeoff and landing, weather, approaches and night flying.
Dynamic rollover
What makes the helicopter such a versatile vehicle is its ability to take off and land vertically. But that capability can turn out to be one of its biggest vulnerabilities. Taking off and landing vertically implies that there’s a moment in the maneuver when the pilot needs to delicately balance the dynamic forces of the aircraft while it is very close to the ground and to possible obstacles. The slightest unwanted drift can result in contacting the skid or wheel into an obstacle like a rock, a tree stump or any other asperity and can create a roll that, if not promptly corrected, can flip the helicopter over. Not the greatest way to start your day!
Another possibility is that the skids or wheels have sunk into soft ground, mud, snow or are caught in ice. In that situation, the undercarriage is already snagged by the ground, and this necessitates a perfect vertical takeoff without the slightest drift. Needless to say, takeoff and landing are critical maneuvers and must be executed delicately and precisely. A good preventative technique is for pilots to make a habit of taking more time for every takeoff and landing (not just on uncertain ground) so for that one occasion where the skids get unexpectedly caught, they will have some time to correct the situation. If you get used to expediting every takeoff, you give yourself much less of an opportunity to recognize the rare situation that necessitate a very slow maneuver. Think of the takeoff this way: instead of lifting the aircraft up in the air, slowly bring it floating up on the cushion of air building up between the ground and the rotor disk.
Takeoff techniques
The first step is done even before sitting in the helicopter. While you’re walking to it, take time to evaluate the surroundings. During your walk around, inspect the surface close to the parking area for anything that could interfere with the undercarriage during takeoff. If deemed necessary, you could prepare the surface by removing the rocks, shoveling the snow or breaking the ice. When ready for takeoff, take a second to evaluate the cyclic and pedals position, then slowly bring the collective up. Once light on (the) skids, pause the power application and yaw the aircraft left and right a couple of times to release the bond with the ground. A very slight left and right roll with lateral cyclic can tell you that you’re free, and you can continue to slowly raise the collective up into the hover. If at any time during the maneuver you feel something’s not right, reduce power and reassess the situation.
Landing precautions
It’s always important for the pilot to evaluate the touchdown area before proceeding to land, especially if it’s an unfamiliar area. In a stable hover, look for obstacles and terrain conditions and plan accordingly. Try to land as far as possible from obstacles. Maintain a very stable hover and execute a perfectly vertical descent to the ground. If landing in loose rocks or uneven ground, ensure that the aft part of at least one skid is well supported. Very slowly lower the collective, correcting with cyclic for every change in attitude, until the undercarriage is properly supported and there is minimal chance for further shifting. You can also gently move the collective up and down during the power reduction to help you feel the weight transfer to the ground and make fine adjustments with cyclic and pedals. If any doubt arises during the landing phase, apply power and ease back up to reassess. Landing in deep snow can also be a problem. Most of the weight of the helicopter is resting at the back of the skids. During the weight transfer, if you’re not equipped with bear paws, the aircraft will sink deeper in the back, putting the tail rotor very close (to) or even touching the surface. Proper technique to land in snow is the following: right after skid contact, gently swing collective down then back up in an increasing fashion while pushing the cyclic forward. That way, it sinks in the deep snow in a controlled motion with a proper attitude and not pitching tail low. Keep in mind the risk of not knowing the surface hidden under the snow blanket, which could create a hazardous landing. Obviously, use a proper technique (like discussed previously) to take off from that snow-covered terrain.
Flying is a perishable skill that should be practiced regularly, especially maneuvers that apply in rare situations throughout the year. Don’t hesitate to hire a flight instructor to brush up on these techniques at least once a year.
On any other surface (other) than a flat and prepared one, treat every takeoff and landing as though the helicopter may be stuck or can become snagged. It's always good practice to be smooth and gentle at the controls of a helicopter. At cruising altitude, you might be 1 500 ft away from any obstacle, but during takeoff and landing, you’re just 15 mm from the biggest obstacle of all: the earth! Because of that fact, it’s the most crucial time to exercise that fancy flying.