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
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:
- a descent rate >= 300ft / minute
- an airspeed < ETL (Effective Translational Lift)
- power in use
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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1 comment:
Interesting lesson Chris!
It's great that they have you doing recovery from VRS -- I never got to practice that or an auto from an OGE hover until I went to Robinson's Pilot Safety course.
As an aside, I do not like the "settling with power" term even though it's widely used. Mostly this is because the term doesn't explain how you can get the TR into a VR state.
In any case, VRS is analogous to a stall-spin in an airplne on the base to final turn. Both are essentially unrecoverable )if fully developed) because you just don't have the altitude to effect the recovery.
The importance of the training is so that you can recognize incipient VRS. And it will happen. One of these days you'll make a landing in highly variable winds and as you slow down, end up with a big tail wind. Ideal conditions for VRS! Thats happened to me a number of times, once when my wife was on board. At an airport, it's not a big deal: a little forward cyclic to get you through ETL, collective to slow the descent. Then a normal landing. My wife never knew there was a problem!
However, if it starts to develop in a landing to a confined area, you may not have the luxury of recovering, because you may not have space to regain airspeed. The moral is to always be aware of wind direction. A friend of mine told me that the Army puts a heading bug in Hueys on the compass or DG as appropriate. The purpose is not for course maintenance but to remind the pilot of expected wind direction.
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