Autorotation training

April 10, 2012 by Tim McAdams

On April 10, 2003 in Auburn, California, a Hughes 269B helicopter was destroyed when it collided with terrain while on an instructional flight. Prior to the accident, a witness on a farm about 3 miles away heard and observed the helicopter performing maneuvers consistent with multiple practice autorotations to a power recovery. The helicopter then flew off in the direction of the airport. Witnesses near the accident site observed the helicopter in level controlled flight about 500 feet above ground level flying in the direction of the airport. They observed the helicopter’s nose drop and then it dove toward the ground and disappeared behind a tree line. Ground scars and the wreckage exhibited evidence consistent with the helicopter colliding with the ground at a high rate of descent in a level upright attitude and rolling on its right side.

The National Transportation Safety Board determined the probable cause of the accident as the misjudged flare maneuver by an unknown crewmember during a likely practice autorotation that resulted in an in-flight collision with terrain.

Ironically, more accidents happen each year from practice autorotations than from actual engine failures. Surprise throttle cuts are especially critical because they can startle students and cause them to make sudden incorrect control movements. Inadvertently raising collective, pressing the wrong pedal or lowering the nose can drop the rotor rpm and risk stalling the rotor system. A student who simultaneously performs two or more of these movements could quickly stall the rotor system.

Before introducing forced landings, it is important that the CFI and student establish a strong understanding of what is expected and what can happen. Then, the CFI should introduce simulated power failures slowly by telling the student in advance of rolling off the throttle. At first, this should be practiced at very low power settings to allow extra reaction time. Only after the student’s reactions are correct and predictable should the difficulty level be increased. Even then, the CFI should always plan to initiate the autorotation and completely guard all the flight controls.

As the following accident demonstrates, guarding the flight controls is even more important for pilot examiners as they are probably not very familiar with the applicant’s background and habits. According to the NTSB, on June 28, 2003 a R22 helicopter impacted the ground and rolled over during a practice autorotation during a private pilot check ride. After completing a series of maneuvers, an autorotation was initiated. According to the designated pilot examiner, the entry and flare were uneventful, and as the pilot applied power to recover the engine and rotor rpm needles were in the green. The pilot then began to cushion the descent with collective and the low rotor rpm horn activated. The check pilot expected the pilot to lower the collective slightly and roll on additional throttle; instead, the pilot lowered the collective almost all the way down and rolled some throttle off. At this point the helicopter was very close to the ground. The check pilot told the pilot “I have the controls.” The helicopter entered a right turn, then the check pilot felt the right pedal move against his foot, and the helicopter settled to the ground at an angle. After bouncing once, it touched down on the left skid and rolled over.

Neither the pilot or the examiner were injured and after the accident, the DPE asked the pilot if he had been rolling the throttle off as he was pulling the collective up during the cushion portion of the autorotation. The pilot reported that in the past he had been over-speeding the engine, so he would slightly reduce the throttle to compensate. The density altitude at the time of the accident was 8,393 ft., leaving little margin for errors.

11 Responses to “Autorotation training”

  1. Avi Weiss Says:

    Good points Tim.

    Oddly enough I think that “advanced” students, and rated pilots in recurrency training are at a slightly greater risk of coming to grief from what I call “recovery expectation”. I know of several instances with practice autos, particularly in turbine aircraft, where the engine hesitated or otherwise failed to provide power during the power-recovery phase.

    In each case, the aircraft was forced into an actual “full-down” auto, but imprecise technique due to “power recovery expectation” led to the aircraft being out of proper orientation (skids-level), and were tail low. During touchdown, the subsequent nose pitch-down caused excessive blade flexure, which contacted tail boom and cockpit, and destroyed the aircraft (thankfully no fatalities).

    As I advise my students, I think it’s important that ANY time a “practice” auto is attempted, the “expectation” should be set that ground contact will be made, and that power-recovery is a bonus. While a bit draconian, it will help drive home the necessity of ensuring the aircraft is level at the end of the maneuver, so that any ground contact will result in little or no aircraft damage, and of course avoiding any fatalities.

  2. Dave Koch Says:

    I soloed a Hughes in 1967 (civilian) and then moved on to U.S. Army rotary-wing training in the early 1970s. I didn’t do full-touchdown autorotations until the Army training. From that point forward in my approx. 800 hours of helicopter time, we always did full-touchdown autorotations when ever autorotations were practiced. In fact, as I recall, we had to demonstrate proficiency in full-touchdown autorotations every 90 days in the Army.

    It is my firm belief that autorotations that terminate in a power recovery are negative training and should be banned by the FAA. It is also my firm belief that any pilot that is not proficient in full-touchdown autorotations should not be allowed to fly helicopters.

    The accident record confirms this belief.

  3. Phil Bridges Says:

    I retired as an Army aviator in 1993. The Army stopped doing touchdown autorotations in the late 80s (except in initial entry flight training) due to their experience that more helicopters were being damaged or lost in performing practice touchdown autorotations than in actual engine failures. As far as I know, that is still the Army policy.

  4. Rick Thorpe Says:

    I am not sure I get the point of the article, and I find the language used by the author makes me wonder about his rotorcraft experience. To suggest the rotor system will stall if the pilot pushes the wrong pedal or pulls up on the collective suggests the author doesn’t really understand the true hazard is in fact a decay of rotor RPM. First, I can’t help but question the suggestion an engine will overspeed as collective is applied in the late stages of an autorotation to cushion the landing. It is just inconsistent with reality. Yanking on the collective will never result in an overspeed of the engine or an increase in rotor RPM. Never. Second I question the logic offered for not conducting practice autorotations. That is to say that it is as a result of practice that the student pilot develop the correct instincts and reactions when presented with the symptoms of an autorotation. To suggest not practicing simulated engine failures because the student pilot might react incorrectly is kind of absurd. Finally, the autorotation scenario described at the end of the article is precisely what I expect to happen in the very late stages of an auot, within feet of the ground. Remember, engine response is not instantaneous, and that when going from flat pitch to nearly full up with the collective, there are going to be deviations in the heading of the aircraft as well as changes in rotor RPM. Perhaps I am missing the point of the article.

  5. Taser Says:

    Anyone who thinks that all auto practice should be performed to full-down is simply wrong. If that were actually undertaken we’d
    have more serious accidents and deaths than ever before.
    How many NTSB reports can you find that show engine expiration for piston or turbine helis? Not many, I think.
    No, this is a classic case of someone recalling the “good ‘ol days” and erroneously thinking that today’s methods are all wrong.

  6. Jim Borger Says:

    I started Army flight school in January of 66. As part of my training I had to solo in touchdown autos. During my training I did hundreds of touchdowns, day and night, and power recoveries. After my all expenses paid vacation to exotic Southeast Asia I returned to instruct for two years. I had 1,800 hours when I started instructing. Each of my students, I had 3 or 4 at a time, did at least a dozen touchdowns every other day and were very comfortable doing them by the time they graduated. The Army had very few accidents doing this type of traiining.

    Later the instructors had less and less experience, resulting in more accidents and incidents, so the Army stopped doing full down autos for some time. As a result, after a real engine failure, their pilots could do a great auto through the flare but the touchdown left a lot to be desired. Of course, we are talking generalities here but I personally know a number of pilots that totaled their aircraft in this way. Engines are much more reliable these days but they do still fail on occasioon. I may be an FOG (fairly old guy) living in the past and stuck in my ways but you will never comvince me that issuing a certificate to a pilot without that person demonstrating an abillity to safelly land after an engine failure is a good idea.

  7. Jim Miller Says:

    In fixed wing training I was taught full stalls,in mel.vmc demos. but in my com.helicopter.training no full down autos.? I was told only CFI training required it. I found a CFI.that would let me do them,and I must admit I think it made me a better pilot knowing what to expect.

  8. Bill Says:

    Dear Rick Thorpe,

    NOWHERE in the article does the author or anyone else suggest that an engine overspeed will develope as collective is applied in
    the late stages of an autorotation!!
    Instead of questioning the writer, you should strive to improve your incredibly poor reading comprehension skills.

  9. Bill Says:

    Dear Jim Borger,

    Just wondering why fixed wing pilots are not required to do engine off emergency landings during their training?
    Also, please provide us with accurate stats that back up your claim that the Army had “very few” accidents
    when doing full down autos. You can’t, becaise that is simply untrue.
    All this sounds like it’s your fond memory talking rather than exact data.

  10. Jim Borger Says:

    Fixed wing pilots don’t do forced landing practice to the ground because every “normal” landing is a full touchdown. In addition, you only need a small clear area to land a helicopter but a fixed wing takes many hundreds of feet to land. Touching down at 60 mph could be a disaster on a soft surface so you don’t want to do that unless you have no other choice. I was taught zero ground run autos, not the “slide on” they do now.

    By the way, I was also taught to land fixed wings by pulling the throttle all the way to idle and leaving it there until bringing it back up to taxi after landing. That way, every landing was a practice engine out landing. Today fixed wing pilots fly B-52 traffic patterns and carry power all the way to touchdown. I used to have an older friend, he passed at 102, that atarted flying WW 1 aircraft landing power off and continued that practice as an airline captain flying jets. As far as stats go about my time in the Army, facts not “fond” memories, I can only speak to what I personally observed and was told during safety meetings. Sorry, I din’t keep notes from 40+ years aago so I can’t furnish you with exact numbers.

  11. Rick Thorpe Says:

    Just a bit harsh there Bill don’t you think? Perhaps you shluld take another look at the last paragraph. It clearly suggests the pilot retards the throttle to avoid an overspeed as he applies collective to cushion the landing.

    Incredibly poor reading comprehension skills? Really? Might want to lay off the caffeine there Bill.

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