Full down autos

August 17, 2013 by Tim McAdams

When practicing autorotations, the maneuver is initiated by reducing the engine to idle causing the freewheeling clutch to open, which then disconnects power to the rotor system. As the helicopter glides toward the ground, there are two ways to terminate the maneuver. One is to add the engine power back in and bring the helicopter to a hover, this is known as a power recovery autorotation. The other is to leave the engine at idle so the freewheeling clutch stays open, keeping the engine disconnected from the rotor system. Known as a full touch down autorotation, the pilot will increase collective pitch at the right time to create a momentary burst of lift to cushion the touch down.  In the helicopter industry, there are differing opinions on the value of practicing autorotations to the ground. 

The touch down requires precise timing because as the pilot adds collective pitch, rotor rpm begins to decay. If this is done too early, the rotor rpm can get too low causing controllability issues, excessive blade coning and loss of ability to cushion the touch down. By avoiding ground contact with a power recovery autorotation the risk of damaging the helicopter from a hard landing is reduced considerably. Some instructors and companies believe the risk of damaging a helicopter during touch down is too high and the benefit of actually landing does not justify the risk. The thought being that if a pilot performs the proper entry, maintains rotor rpm, maintains appropriate airspeed and then flares at the correct altitude the autorotation will be survivable. In reality, accidents from practice autorotations rarely cause serious injury or death, however, there have been many helicopters damaged from practicing autorotations. In fact, the US Army stopped practicing autorotations to the ground because they were damaging too many helicopters. 

I understand the risk vs. benefit analysis that leads to the decision to only perform power recovery autorotations. However, I think it is beneficial to practice autorotations in the most realistic environment that can be safely done, including full touch down to the ground. The risk can be minimized by using an experienced instructor with proper and extensive training in autorotations. Factory schools like Bell and Eurocopter have been doing full touchdown autorotations for many years with a good safety record.

  • David from Alabama

    Interesting article. I took my instructor checkride in a Hughes 269C and was required to perform a 180 deg full touchdown autorotation. When we stopped, the examiner looked at me and said, “I’m glad you did that so well, because there is nothing I can do in time to respond if you mess it up.”
    I think everyone should experience it at least once, even if it is performed by a competent instructor as a demonstration because it really gives a whole different perspective. I also worry about inducing training scars if we only do power recovery. The sequence of events with a touchdown is much different at the end (not responding to torque and cushioning touchdown) than when doing a power recovery. My instructor began with a series of autorotations where we cushioned the touchdown with power, then advanced to straight-in touchdowns, then 90 deg and finally 180 deg full touchdowns.
    The shock absorber system on the H269 skids helps reduce some of the impact. Full touchdowns in a R22 or Jet Ranger might be a bit harder on the aircraft.
    Thanks for the thought-provoking article.
    David from Alabama

  • Nick a

    Obviously we all have differing experience and fly different helicopters (high vs low inertia), but the statement about instructor reaction bothers me. I believe, as an instructor, you should get the students out of their comfort box, but never outside yours. If the instructor “could not respond in time” he probably has no business instructing those types of autos until he can. I have significant experience with full touchdown autos in a Jet Ranger and while (like in ANY helicopter) it is POSSIBLE for the full auto to be rough, they usually are very smooth. We practice them through a range of speeds and DA’s. If we as CFI’s are not hugely comfortable with them, go fly with another CFI, practice them, don’t wait for a BFR to do it.

    I do agree that with proper training everything should be the same between full and power recoveries until the last few feet, always assume that engine will not come back and if it doesnt, you can walk away without any damage to the aircraft.

  • Peter bewley

    I learnt to fly in R22 all autos were to the ground .power recoveries are ok but it’s no like full autos , I know by doing quick stops helps.

  • http://TAC.aero Clarke

    I am a firm believer in full down autos, evenn at the Private level. With that being said, I also believe that the full down autos should be accomplished under the most favorable conditions for both pilots and aircraft to mitigate the inherent risk. I would like to see this maneuver required for certification, but, be done by a qualified instructor and have the students log book endorsed, much like spins in fixed wing aircraft. Requiring a CFI candidate to execute a full down during a check ride while they are under extreme nervous conditions, and the environment may very well be adverse, (calm winds, high DA), can only be described as foolish. This is why the FAA requires inspectors to observe the maneuver from the ground, but have the misguided requirement to require us DPE’s to be onboard, go figure? Power recoveries in turbine powered equipment is completely different than full downs. The only similarity is the entry phase, you will never know what the most critical part, the last 6 inches, is like unless you have executed the complete maneuver. Fly Safe, and love every minute of it!

  • Bob

    The FAA just published a new AC on practicing touchdown autorotations.

  • Bob
  • Mark

    I learned to fly helicopters in the Army in 1968 using Hughes TH55A models in primary flight school. We practiced full autorotation landings on a regular basis with those helicopters and later at Fort Rucker in advanced training we did the same thing with UH1D’s. I don’t remember any of my class mates damaging a helicopter during the 9 months of training. Only once in my career did I have to actually perform a full autorotation due to mechanical problems and it worked perfectly. I think it’s a disservice to a student pilot to teach only power recovery autorotations.

  • Chris

    While I have performed hundreds of day and night full downs as an Army instructor I do have one concern with the full downs that some instructors teach. I have had students and instructors demonstrate their full down autos with me and we end up touching down at 20 knots, sometimes higher. When I mention this is a problem they respond that it makes the full down safer. My response is if you do this in a field the odds are you’ll end up in a ball. I’d rather teach flair and pitch control to zero ground run. Maybe I’m just getting old. Started doing this in 1966. God Bless

  • Bill

    Since I just finished my add-on rating I can comfortably speak from what its like in the current Helicopter training environment. I have considerable experience in General Aviation with 30 years of largely remote operations where most flights if terminated early due to a catastrophic equipment failure are truly a matter of survival. Being able to bring a helicopter or fixed wing back to the earths surface under extreme stress and with complete control will determine ones ability to walk away safely. I know the last few seconds (I’ve been there) just prior to contact is vitally important to have ALL control inputs properly choreographed and committed to muscle memory. Over the past six (6) months of helicopter flight training at well established schools in two different states neither were willing to teach full down autos in R22’s or R44’s. I asked all my instructors repeatedly to demonstrate a full down auto and finally was shown one (1) on my stage 3 check ride.Stalls and Spins in a fixed wing aircraft are demystified when given the opportunity to experience the maneuvers with enough repetition for the external/internal sensations to become anticipated and predictable…I believe the full down autos should be taught in primary helicopter flight training.

  • John

    LAX02GA209………………….I survived for the simple fact of being fully trained. I have, and always will push new pilots toward advanced emergency training. Full downs, spins, all of it. Just no excuse. Western Operations in Rialto, CA. (rotorcraft) CP Aviation in Santa Paula, CA. (fixedwing) These organizations, and I am sure many more, are staffed with the best people in the business. As a retired, but still active pilot, I will always take refreshment EMT training and will push (annoy) other pilots to do the same. As pilots ‘in command’, we owe it to the people that put their lives in our hands. No excuse, none.

  • http://kitcopterconsult.com Homer Bell

    All above is good information. However, I flown several different helicopters in my 40 plus years of flying. I’ve experienced several engine failures and at least one very serious control failure that i was very lucky to live thru, all with little or no injure. All most all of these were in homebuilt helicopters, hence the high failure rates.
    The two most important phases of auto’s are the entry and the flare. If the pilot executes these somewhere near where he should, he will more than likely walk away with no problem to his body. The ship may very well be another story . If you can tell me where I’m going to have to set down a machine with and engine out, i’ll tell you how well you need to do auto’s, ,because if the terrain is not good, being able to do full downs isn’t going to matter much.
    Doing runon’s at much above translational speed is pretty dumb as far as i’m concerned. For all the talk about runons with stuck pedal, i want to know how many have ever really had a stuck pedal and at what position was the pedal stuck? There has been far more 269’s torn up doing practice runon’s than ever were with real stuck pedals I’d be willing to bet.
    Also, there is one heck of lot difference between different helicopters as to how well they auto. Full downs in a Bell of any model is one heck of lot easier than say a Robbie, Brantly, or 269/TH55. So if you want to teach full downs, better pick machines carefully.
    I’m not going to go back and read again, but, I think the article didn’t mention the flare as being the thing that will stop the rate of descent. They only mention pulling pitch. Good luck with that.
    One last point. There are few machines out there that will slipstream and allow you to runon with NO TAILROTOR, at least in the under $500K models, IMO. So be prepared.

  • Steve Raether

    As a retired police helicopter Chief Pilot and Instructor, I performed and taught many full down and power recovery auto rotations in MD 500E helicopters. We gave primary instruction in these helicopters and have accumulated over 50,000 hours accident and incident free. AC 61-140, as posted by Bob, pretty much covers it all. Although the AC is fairly recent, we utilized the same training recommendations for many years with much success. The only thing I would like to add is teaching the student to consider the auto rotation as the practice of managing sources of energy. Rotor RPM, Airspeed, Altitude and Engine Power are all sources of energy. Obviously, in a power off auto rotation, you only have Rotor RPM, Airspeed and Altitude. Depending on the aircraft attitude and circumstances, one source of energy can be traded for another. I have found that this understanding along with a thorough understanding of the Flight Manuals recommended altitude, rotor RPM and airspeed for performing auto rotations, students quickly master the art of performing auto rotations.

    Regarding the controversy over full down verses power recovery auto rotations, I believe both are important. I believe the highest risk of full down auto’s is injury and damage to the airframe and the risk of power recovery is primarily to components (over torque and/or over speed). Usually, airframe damage is more costly and time consuming to repair as opposed to an over speed or over torque. For this reason, my agency chose to perform power recovery auto’s during our 90 day recurrent training sessions and full down auto’s during our annual factory training sessions utilizing factory aircraft. This policy continues to work very well for my former agency.

    Thanks for the article and thank you for allowing me to share my thoughts.

  • John Horn

    In Army flight school in ’68/69 all autos were touchdown. On active duty and later in the Guard aii autos were touchdown in UH-1C,D,H, & M models. I don’t recall any accidents in flight school nor in my units. When I gave it up in 1978 policy was still touchdown. To me, the only sure way to train for maximum success is full touchdown.

  • John Horn

    Incidently, even though a touchdown auto was considered properly performed with a max slide of one helicopter lenght, we trained for zere groundrun. Pretty easy if you trained consistently to hat standard.

  • John Horn

    Sorry about the spelling.

  • http://hoverpower Ron Andress

    All comments very interesting and informative. My first hour of Bell 47 time I asked my instructor if auto rotation was a reality or was it a hope for the best situation. His response was to chop the throttle, lower the collective and as the things got quiet he looked at me and said “now we just wait for the ground to get here” a short time later we touched the grass and slid about 5 ft. to a stop. He explained that flying a helicopter is a learned skill and if I was willing to learn he would hopefully teach me enough that in an emergency I could save my life and as an added bonus if he taught me well enough and added a little luck I could hopefully not do too much damage to his helicopter in the process. I did several solos and cross countries in the Bell 47 and during that time as well as my dual time we did power recovery autos as well as quite a few full touch down autos. As my instructor put it “you never know if you will have the luxury of power so prepare for it” The point here is that from that first full touch down I never had to wonder if it could be done if needed and that was one less thing for me to be concerned about every time I went up. An important fact to note here is that a Bell 47 has a high inertia rotor system and as such much more forgiving than say a Robinson or any sort of home built that I can think of. Rotor RPM will decay very fast on a lighter system so knowing your aircraft is very important.
    Happy flying and be safe,,,,,,,,One more comment,,,,,,all you military guys out there current and retired THANK YOU FOR YOUR SERVICE , without you some of us would never know the pleasure of flying for enjoyment.