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January 1, 2014
By Ian J. Twombly
Nothing evokes the essence of a helicopter more than the image of the main rotor screaming away as the machine lifts straight up off a hospital, highway, or helipad somewhere. The ability to vertically takeoff and land is the helicopter’s raison d’être, its magic power. These feats are all the more impressive when you learn that these takeoffs are outside the realm of normal operations.
Maneuvers: Maximum performance takeoffs and steep approaches
The safest way for a helicopter to take off and land is a profile not unlike an airplane’s. The landing is a nice, stabilized approach (albeit steeper than fixed-wing at around 10 degrees), and the takeoff is a sort of running operation that feels similar to an airplane soft-field takeoff where the machine slowly builds up forward speed a few feet above the ground until pulling up to gain altitude.
Takeoffs are safest when performed within the guidelines of the Height-Velocity Diagram, a chart that plots airspeed versus altitude. The reason to stay within this chart? Engine failures. Just like an airplane, an engine failure in a helicopter close to the ground is a tricky spot to be in. Autorotations can be difficult or impossible if you’re outside the accepted profile. But obviously we see helicopters taking off and landing straight up and down all the time, so clearly doing so isn’t abnormal. And of course it’s not, but like taking off an airplane over dense forest or water, the pilot accepts some additional risk to do so.
The vertical takeoff is called a maximum performance takeoff. The pilot simply lifts off the ground and just keeps pulling collective until clear of any obstacles, at which point any increase in altitude is traded for forward airspeed. Practicing these is incredibly fun, and is a vivid reminder of why people learn to fly helicopters in the first place. The sensation isn’t so much of zooming up as it is the ground melting away. It’s like magic.
Those “vertical” landings are called steep approaches, and are done at a high approach angle (15 degrees or so) and very slow airspeed. Like many of the maneuvers required for the helicopter add-on, this one is all about finesse. Get too slow or descend too rapidly and you risk a condition known as settling with power. Too fast and you overshoot the spot. Do it right and you get a great view as you aim for a spot that appears to be pretty much at your feet.
One of the fun parts of the steep approach is that it’s done at a speed right on the verge of effective translational lift, or ETL. This is the point at which forward airspeed causes the main rotor blade vortices to drift downwind of the blade disc. It’s signature is a shake or burble in the cabin of the helicopter, which means you get this great rumble that you can decrease with forward airspeed and increase with decreased airspeed as you come down on the approach.
Plus, taking off and landing almost vertically is just cool, and is a big part of what it means to fly a helicopter. Getting a handle on these takeoffs and landings enables the student to graduate to practicing confined-area operations.
You can read all the stories in the Rotorcraft Rookie series on AOPA Online.
Next time: Confined-area operations.
Flight Training Editor Ian J. Twombly joined AOPA in 2003 and is an instrument flight instructor.
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