To pilots of the fixed wing community and to many civilians, they think if a helicopter has a serious mechanical problem, the pilot can autorotate to a safe landing. The uniformed equate gliding in a fixed wing airplane with autorotations in helicopters. To which I say, baloney, they are not the same.

Civilian helicopters tend to be operated in urban areas by the police, fire departments, radio stations and corporate flight departments. Considering all the power and telephone lines around, there aren’t many open areas to put one down. Or in the Navy, over open w6ater. Again, what seems to be simple, i.e. landing in the water, isn’t.

When a helicopter is autorotating, it is not going to travel very far. Very early in the Naval Air Training command, I learned that once the helicopter entered an autorotation, where I was going to land was not miles ahead, it was right below my feet. In other words, the helicopter doesn’t glide very far.

So, your helicopter has to land immediately. First thing is lower the collective to the bottom stop ASAP. The collective is the control that controls the pitch of all the blades, engine rpm and power being generated by the engine(s). If the pilot doesn’t get the collective down, and assuming the problem is related to the engine or engines, the rotors will start to slow down. Below a certain rpm, the helicopter becomes an uncontrollable brick.

With the collective firmly held down on the bottom stop, things happen very fast. The helicopter is descending in a hurry, as in 4,000 – 6,000 feet per minute. Do the math, if you are at 1,000 feet and the descent rate is 4,000 feet, you have one quarter or a minute – 15 seconds – to find a place to land.

Once the nose attitude is in the optimum or near optimum position for the best autorotation speed, next up is the landing itself. Remember, in an autorotation, the helicopter doesn’t have any engine power or has some other major problem such as a fire, battle damage, pieces coming off the helicopter, etc. sanity along with the desire to live says land NOW!

The theory in landing from a full auto rotation is that the pilot trades rotor rpm for rate of descent to cushion the landing. How the autorotation landing is performed depends on the size and type the helicopter, but what follows are the basic steps.

Somewhere around 100 – 150 feet, the pilot starts raising the nose to bleed off airspeed. The pilot trades off airspeed until the helicopter is about 20 – 40 feet off the ground and then flares (hauls the nose up). For a fraction of a second, the rotors accelerate and then start to decay, i.e. slow down. The trick is to land safely, not softly, while you still have enough rotor rpm to control the helicopter.

Flare too high and the pilot will run out of rotor rpm before the helicopter touches down. The result is a crash of some type. The preferred technique is to rock the helicopter forward and land with a modest – less than 10 knots – amount of forward airspeed. If the helicopter has wheels, the pilot can land with more forward speed than if the helo has skids.

Experience says it is better to wait too long and make a running landing than to flare to soon and run out of rpm. However, if one is squeezing the helo into a confined area, the pilot has to get everything right the first time.

Getting all of this right is not easy. Do it right, and you have a very good chance of walking away. Get one of many variables wrong, and you’re along with everyone else in the helicopter are going to have a very bad day!

When I was in the training command, we practiced full autorotation in the TH-57 over and over again. A full autorotation is one in which you use only the aerodynamic forces and the inertia in the rotor blades to control and land the helicopter. We students had to perform them from several different attitudes and altitudes on your check ride. Even with an instructor in the right seat, there was always the danger of rolling one in a ball.

When I reached the “fleet” in 1969, we could practice full autos in the single engine H-2A/B. In the twin-engine H-2C/D, H-3, and H-60s, they were verboten. We did everything down to where we flared the helicopter just before landing which was about 40 feet above the ground.

I guess the reason that full autos in a multi-engine helicopter were forbidden is that some mathematician figured out that the chances of us every having to do one for real was not very high. I’ll be that guy never flew a helo in his life, much less in a combat situation.

Or, that Commanding Officers didn’t want some junior officer crash a helicopter during his tour as CO. Accidents, particularly, if the investigating board determines that there was some supervisory error contributed to the accident are bad for one’s career.

In my 3,000 plus hours of flying helicopters, I’ve had engine, hydraulic, a tail rotor control and other system failures. All were brought back aboard the carrier or destroyer or the Naval Air Station. Thankfully, I never had to perform a full autorotation.

2 Comments

  1. Lee Bennett on January 4, 2021 at 9:15 am

    Marc: Couple of things. While I was an instructor at HC-2(left the service end of august, 1970) we practiced full auto rotations in all models of the UH-2. that practice must have stopped after I had departed.
    Second, your narrative references 2 flares – one at 100-150 ft AGL(150 in my time), and another at 20 feet. When I flew we had only a single flare at 150 ft, then settled into a soft landing by gradual pull up of the collective.
    I had two actual auto rotations. One in a single engine UH-2B into a pine tree forest in South Jersey, and the other in a Charlie twin failure, just making it to the edge of the runway at NAS Norfolk. Both scary as hell.

    • Marc Liebman on January 10, 2021 at 10:23 am

      Lee,
      Thanx for reading the post. BTW, I only check this part of my website on Sundays when I post my blog and other articles.

      I arrived at HC-2 in July 0f 1969 and you were the HAC on my first flight in a UH-2A on 7/29/69!!!! We flew again in August, again in a UH-2and I flew together in a B model. Typically, what I would try to do is dish out the bottom end by slowing the helo from 70ish knots to something more manageable and the around 40 – 50 feet or so, flare, pull up on the collective and hope that I had enough rotor rpm to cushion a roll-on landing at about 5 – 10 knots.

      In the training command, we did full autos in the TH-57 and then in the UH-Ds. I was in the first group of students that flew the UH-s which were very tired Vietnam vets.

      I have, at least according to my Navy log books, about 2800 hours in Navy helos and about a hundred more in civilian machines. Thankfully, I never had to perform a full auto!

      marc

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