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Tuesday, January 19, 2016

Blades of Glory

Quotes like this are how I rationalize my lack of a college education.  That and the fact that many college graduates I meet today don't seem to be very well educated, compared to the way I was by the time I finished high school.  Perhaps I've watched too much Watter's World.

Just to jump ahead of the story several decades, I skied with my cousins over the weekend.  I briefly mentioned that Tom Jones introduced me to skiing in my 30s and there is a big story behind why it became a favorite activity of mine, but I have to develop a few more situations before we can get into that.

For now, let's finish up the helicopter thing.  In the last post, I showed the various controls and explained that learning to hover was the real challenge of rotary wing flying.

This might help explain why.  The cyclic is like a stick between the pilot's legs.  It moves the attitude of the chopper in pitch and roll.  It makes the nose go up and down and banks it left and right.  It does this by increasing the angle of the blades of the rotor in the appropriate position only to change the attitude.

The collective changes the angle of all the blades all the way around the rotor to cause the chopper to ascend or descend.  

Any increase in rotor blade angle will increase drag on the rotor and begin to slow its speed.  The speed needs to remain constant, therefore you must add power to adjust and maintain the rotor speed.  Power is increased by twisting the throttle, which is on the end of the collective.

When you add power, the body of the helicopter wants to spin in the opposite direction of the rotor.  There are pedals on the floor that cause a change in the blades of the anti-torque rotor on the tail.  

So, you can see, that any change in any control causes an adjusting change in all the other controls, when hovering.  If the wind is not blowing, things are relatively easy.  When the wind is gusty, the pilot literally has his or her hands full.  It has been described as dancing on the head of a pin and requires a very high level of concentration.

You are taught to become aware of the rotor "disc" as part of its arc swings above the forward part of your field of vision.  My instructor, Pete, said that it was easy teaching me, because of my previous experience flying planes.  I had an air awareness and there were crossover concepts that made it easy for me to understand.  The fact that I was flying many hours in a short period of time was very helpful.  I had learned that with my own students.

If they allowed large chunks of time between lessons, we had to spend part of the lesson going back over things already learned to assure that they were retained.  If not, they had to be retaught.  Sometimes, I would ask if money was a problem and advise them to figure out what their total cost would be and borrow that much to consolidate their flying.  In the long run, it would save flight time and therefore it would save money.

I flew the chopper as often as I could and it took about 10 hours to learn to hover.  Pete would have me use one or two of the controls while he used the others.  Then he would have me use the others and slowly try to incorporate more and more into what I was doing.  Eventually, I was doing it all, but the aircraft was bouncing around a lot.  Then one day, it suddenly stopped and I had it. 

They say it is like trying to pat yourself on the head, while rubbing your stomach.  I think it is harder.  I can do that pretty easily.  But you try it.  Ha!  You're actually trying it, aren't you?

Then we could start doing the maneuvers necessary to pass the commercial helicopter check ride.  Some of these were hovering in a square, forward, to the left, then backward and to the right .  We practiced landing on a pinnacle at an old slag heap near an abandoned coal mine.  That was kind of fun.  You had to hover into the pinnacle slowly and put one of the skids on the pinnacle while the other one was hanging in space.  This was to learn how to rescue people from a mountain.  You always had to be aware of the width of the rotor disc, while doing this.

One maneuver was the auto-rotation, which is what you did when the engine failed.  This was very tricky.  When you first started the engine, the rotor was not turning.  There was a centrifugal clutch that engaged the rotor as you increased engine speed, while sitting on the ground.  When they engaged, you increased the speed of the engine and rotor to a green band on a tachometer that showed the speed of both with two needles.

The picture on the right shows them not engaged, while the picture on the left shows them engaged.  There are different indicators for each and they need to be matched in the green band.  In my memory the green band on the Hughes 300 was much smaller than in this picture, so it required very close attention.

Remember, that if you pull the collective the chopper ascends, so when you are first sitting on the ground after start, you must pull the collective.  This will drag down the engine and rotor speeds, so you must twist the throttle up to maintain the green band.  This will cause the body to twist with torque and you must counter this with anti-torque.  Fun, huh?

When the engine is running and the rotor is turning and creating lift, air is passing downward through the disc.  When the engine fails, you must very abruptly lower the collective, which disengages the clutch and separates the engine from the rotor.  The rotor is now free wheeling, driven by the air moving upward through the disc, and providing some lift and the ability to land the chopper with some control.  The glide path is very steep, nearly vertical.  You are sitting in a plexiglas bubble and the spot you will be landing on is pretty much down, between your knees.  You have a little choice on where you are going, but not much.  I was always impressed and a little alarmed at first, at how calmly Pete would sit next to me with his legs crossed as I practiced these. 

I could go on and on with this and tell you all the ways I scared the hell out of the FAA inspector who gave me my check ride, but let's just say I passed and have never flown a helicopter since, except for the time my friend, Mike Stephan, let me try to hover the Jet Ranger he was flying for a company.

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