Friday, February 5, 2010

CFI Checkride Details : Part 2 : The final chapter.

Yup, that's right, yesterday I became a Certified Flight Instructor : Rotorcraft Helicopter.


Been a long journey, but boy does it feel good.


So, from the previous entries you have probably seen that this the 2nd face to face with my DPE, Ron G.  I now understand why he wanted me back.  


First of all, I did not fail the first Check Ride - meaning I was not issues a "Letter of Discontinuation" denying my application the first time. He just wanted me to brush up on something before he was willing to sign.  Basically, the "examiner is always right". 


Turns out that while he thought my explanation for why blade flapping reduces lift on the advancing blade was thin, it was correct. (Phew!)  He just did not like the way I got to the point.  I could have certainly explained it much better the first time, but I didn't.  So, after getting his comments to come back again, I dug in deep.  Way deep into the Wagtendonk text.  If you are not familiar with this book and are reading (and understanding the technical aspects) of my blog... you probably should be.  It is fantastically elaborate and detailed.  So much so, that it is probably the worst book for a Private student.  Too much detail. Too much theory. Too much physics and math for the introductory student.  But, if you want to know exactly why a rotor blade does xxx or yyy, this is your source of truth.


So, I dug in, and learned it.  I know all about force vectors, resultant vectors, inflow angles, blade planes, etc.  I can explain it pretty damn well now.


I took all that knowledge down to Ron, threw it up on the white board and stepped back, all proud of what I had done. The look on his face was rather like Carl Fredrickson from Up. Actually, he really does have a Carl look in general.


Anyway, he says, "Nope, missed it again".  Shit.  SHIT!. How could I possibly have missed this?  I know I'm right, I even have the book in my bag.  I can cite references!


"You are going the wrong direction here.  Sure, your explanation is correct, but I have no idea what the hell you are talking about, and neither will your students. Sit down, listen."


So, Ron proceeds to tell me how he would do it.  He clenches up his hand... and swings (slowly) at me:


Ron: "Where is the Relative Wind?"
Me: "Coming from..."
Ron: "No, show me.  With your hand."






Ron: "Great. Right. Now, where it the Relative Wind?"

Ron: "Great. Right. Now, where it the Relative Wind?"


Ron: "Great. Right.  My point here is I just explained Relative Wind to you without vectors, without math, without all that crap you put up on the board.  Your student will understand this, they may not understand that.", as he gestures to my 4 color vector diagram explaining relative wind.  

Ron:  "Relative Wind is opposite in direction to the movement of an object."

Me:  "Right, opposite and equal in magnitude to the direction of an airfoil..."

Ron:  "No! Well, yes.. but no.  Why magnitude?  Why airfoil?  Don't cloud the issue here. This is simple, and your student must understand this fully before they will understand any of the stuff to follow.  Got it?!"

Ok, got his point here.  I'm not trying to impress my students with my physics and math background... I'm trying to teach a very complex concept of lift to someone who probably does not have any interest at this stage.  Some day they will.. just not right now. 

So, then I went on to simply explain how mixing "2 winds" from different directions produces Resultant Wind in a different direction than the first two.  Ron used a good, and simple, example of a stream of water from a garden hose can be deflected by another stream of water to produce a mixed stream going somewhere else.

Bamm... we have Resultant Relative Wind.  Relative Wind across a rotor blade, mixed with the 'wind' from Induced Flow creates a new Resultant Relative Wind across the rotor blade.  this new wind is at a different angle than the original and will give us a new angle of attack on the blade.  Hence a change in lift.  

Ok, so I think he was rather unclear about what he wanted me to do on my 2nd run at this... but he's right.  I dove in way too deep... and I should have gone shallow.

Point taken sir... point taken.

After a bit of light discussion he congratulated me and asked for my final paperwork and ID.  

Boom goes the dynamite.  

While he was at it, I asked him for my SFAR73 200hr endorsement.  Which he happily gave me, and I immediately entered into my logbook.  

That was it.  The end. I made it.  Phew!

Afterwords I asked Ron if he would mind giving me a quick tour of the facilities at HTS Helicopters, in particular the Sikorsky SkyCrane helicopters they have on site.


All I can say is WOW.  Those things are absolutely amazing. The one above is from Evergreen Aviation, and not in HTS' fleet.  Although they just did buy a few from them, at about 26M a piece.  

As you can see, they are massive.  I believe I read on the underbelly by the hook that they have a max lift capacity of 25,000lbs.  The legs could easily straddle a 18 wheel semi truck.


Couple of interesting facts.  The skycranes
  • ...burn approximately 500gal of fuel per hour.
  • ...have approximately 1500gal fuel tanks.
  • ...cost about $500 to start-up and immediately shut down.
  • ...have a low inertia rotor system.  I mean, it is all relative I guess.  But the point is that they are paid to lift... and the first thing a helicopter lifts before it picks up is its own rotor blades.
Thanked him for the tour and the "beating", and headed home. Tired, happy and proud.

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