Autorotation, Settling with Power and Off Airport

Flight #: 021
CFI: Kristie H.
Aircraft: Robinson R22 Beta
Aircraft ID: N8361N
Duration: 1.1hrs
Cumulative Time: 21.2hrs

Wow. Just plain wow.

Today we finally made it to the next flight lesson; and it included some of the most interesting and exciting helicopter maneuvers to date.

Off Airport Landing:
This was just a test run, as we did not actually get to land, but there is a lot to have to think about before you actually land off-airport. As you might expect... and acronym. PAWOTFEEL:

• P: Power check.
  
• A: Altitude of potential landing spot.
  
• W: Wind direction
  
• O: Obstructions in/around the landing spot
  
• T: Turbulent air in/around your landing spot
  
• F: Forced landing areas, within your glide path.
  
• E: Entry point for your landing.
  
• E: Exit point for your takeoff.
  
• L: Landing Spot
  

The idea is that you select your spot, execute a few right-hand circles, so that you can see your landing spot and evaluate. Then, if all things look good, land. I did 4 circles around while I went through the checklist above. It will get better over time, I'm sure.

Autorotation:
Autorotation, or the state powerless flight.


A well done YouTube video of an autorotation; a few differences in what I learned, but essentially the same maneuver.

Very little lift, in a helicopter, comes from the wind being deflected down by the rotors. The majority comes from the rotating airfoil (main rotor) producing lift via a low pressure area above the main rotor disk. This is summed up nicely with Bernoulli's Principle. So, what does this mean... well, simply put, if the helicopter blades are turning, you are going to get some lift. In normal flight, the main rotor blades are given energy from the powerplant / engine. In autorotation, you are using the kinetic energy from your forward motion and the energy stored to the helicopter due to it's height (gravity pulling the helicopter to the ground). By altering the pitch of the rotor blades, and the attitude of the helicopter you force air up and through the disk, causing them to rotate; and generate lift.

That's it. You glide gently, and most importantly - safely, to the ground.

The creepiest part of it is the sound... then engine is put into idle and essentially noise drops to zero. You don't drop like a rock, you don't spiral to the ground... you glide back to the ground. There is quite a bit of adjustment in the cyclic, collective, and pedals during this time, but it is essentially a normal approach.

There is a slight dropping feeling when you drop the collective to full down, but that goes away rather quickly. The whole experience is utterly amazing. Clearly there is going to be a lot of practice going forward, but the point is to make this almost a second nature move... so that when (not if) you need it again, you are familiar with the move.

Settling with Power:
Next, we tried Settling With Power (SWP). This is a condition where large rotor-tip vortices (turbulence) occur and the lift generated by the main rotor disk is eliminated. Essentially, the helicopter is "chopping up it's own turblence" and can no longer maintain necessary lift. If you try to increase the blade pitch, what you normally do to get more lift out of the blades, you just make the condition worse. The only corrective action is to, 1) reduce pitch, and 2) push out of the turbulent air to get into "clean" air. Once you have forward motion, you can then again, raise collective and start slowing your descent.

This is a very easy condition to get into as you need three, very common, things to happen:

1. a descent rate >= 300ft / minute
2. an airspeed < ETL (Effective Translational Lift)
3. power in use

When this triad is present, the helicopter just drops out of the sky and a very high rate. To practice this, we climb to 2500ft AGL (for safety), position ourselves with a tail-wind (to hasten the dispatch of ETL) and slow our forward motion. The first thing you feel is vibration as you enter the ETL curve. Then, when you start to lose ETL, you get serious vibration. It is at this point when you start settling with power. The vertical speed indicator needle drops, and you start to fall - and fast. Kristie had said that you could easily get 600feet + per second if you let things go too far. In our case, we only dropped about 300ft before we pulled out of it.

After another test, Kristie gave me a shot and recovery, and I must say... I did quite well. Lower collective, forward cyclic, and you gain forward speed. Then, once you have speed, you raise collective and you are back to normal flight.

One hell of a day.


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