Chopper 101 web page - info for fixed-wingers

RotaryWingBob

RotaryWingBob

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As I suggested I might do, I've put together a page describing how you might figure out what we rotorheads are up to. It was inspired by a poster on this board who asked the excellent question concerning why we frequently fly opposing traffic.

It's sort of ironic that most helicopter pilots hold fixed-wing ratings as well. I think we assume that because we understand fixed-wing operations at an airport, that fixed-wing pilots must be able to understand all the things we do. It ain't necessarily so, as the song says!

If this page provides sufficient insight to help prevent a single accident, then I'll consider the effort well spent. Please give me feedback about anything that's missing, anything that's not clear enough, typos, whatever. Thanks, and enjoy:

http://bobanddusty.com/aviation/chopper101.html
 
Very nice, I learned a lot more about 'copters!
 
third.

thanks bob.

whats holding you back from CFI in the helo?
 
Great stuff, Bob. Thanks for this.

I do have a question. This may seem kind of stupid, but reading your entry on maximum performance takeoffs I read that you shoot for 40 KIAS...then in the "The "Oh crap, we're not gonna clear the trees" Maneuver" you talk about starting a rearward movement of the aircraft in order to move away from the obstacle.

Like I said, this may be a stupid question...but why can you just go straight up? Wouldn't THAT be a maximum performance takeoff? If you see you're going to hit the trees...why can't you just come to a hover and go up and over?
 
RotaryWingBob said:
Fear, of course :hairraise:

Not to mention that I don't think I have the patience to teach.
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looking at the obvious time and thought that it took to put together that website, plus all the thoughtful and comprehensive helo explanations you have given on this forum, i highly doubt that you lack the patience to teach. thanks to you I feel like I can do my job a lot better since I actually have a decent grasp on what is going on in the helicopter cockpit.
 
FlyNE said:
Great stuff, Bob. Thanks for this.

I do have a question. This may seem kind of stupid, but reading your entry on maximum performance takeoffs I read that you shoot for 40 KIAS...then in the "The "Oh crap, we're not gonna clear the trees" Maneuver" you talk about starting a rearward movement of the aircraft in order to move away from the obstacle.

Like I said, this may be a stupid question...but why can you just go straight up? Wouldn't THAT be a maximum performance takeoff? If you see you're going to hit the trees...why can't you just come to a hover and go up and over?
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That actually is a very good question. There are two reasons. First, you might not have enough power available. A hover generally takes more power than flight does -- this is because the rotor tips, like any airfoil, generate vortices. In a hover the rotor is constantly flying through the dirty air caused by its own vortices. At around 15 kt you start to fly out of the vortices, and at 40 kt the entire rotor system is in clean air.

The second reason is safety -- a mechanical failure in a vertical ascent will cause you to make a big splat. The attached scan shows the height-velocity diagram for an R44 Raven II. Flight in the shaded area is considered to be risky. Does that mean it's never done? No. Sometimes you have to, but I try not to make a habit of it :D
 

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Bob, Thanks for the information! It's much appreciated.

I think it will be a great resource for students at airports with a lot of helo traffic like PDK.
 
Bob,

do you know what the reasoning is for the shaded area above 60ish knots and below 25 AGL? Sink rate too fast with engine failure at those speeds to respond before smacking earth?
 
Cool, but I looked up a 'Chopper 101' and all I found were some kitchen mixers. I thought that type of aircraft were called 'helicopter' or 'rotary wing aircraft'.

Tony: Yes, below 25' and above 60kts is the 'not enough time' zone to do anything but scream. The rotor has to be unloaded and the flow of air reversed from top-down to bottom-up. It requires some altitude and distance to do that. The neat thing is the descent profile of an auto-rotation. If any fixed wing pilots really want to mess their pants, offer to go along for auto-rotation practice some time. :eek:
 
docmirror said:
Cool, but I looked up a 'Chopper 101' and all I found were some kitchen mixers. I thought that type of aircraft were called 'helicopter' or 'rotary wing aircraft'.

Tony: Yes, below 25' and above 60kts is the 'not enough time' zone to do anything but scream. The rotor has to be unloaded and the flow of air reversed from top-down to bottom-up. It requires some altitude and distance to do that. The neat thing is the descent profile of an auto-rotation. If any fixed wing pilots really want to mess their pants, offer to go along for auto-rotation practice some time. :eek:
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That's because Chopper 101 is a class, not a ship :D

I'd say the right side of the h-v diagram is even worse than that: any failure is likely to induce a big yaw, so you also would have to straighten the ship out or it's gonna do one horrendous tumble. It raises an interesting question, though. If you were quick enough and had a reasonable amount of rotor inertia, you might be able to flare and lower collective to convert all that airspeed into RRPM and cushion the touchdown. I don't see any reason you would have to be in an autorotative state for that to work. I'll let somebody else try that one first though :hairraise:
 
RotaryWingBob said:
That's because Chopper 101 is a class, not a ship :D

I'd say the right side of the h-v diagram is even worse than that: any failure is likely to induce a big yaw, so you also would have to straighten the ship out or it's gonna do one horrendous tumble. It raises an interesting question, though. If you were quick enough and had a reasonable amount of rotor inertia, you might be able to flare and lower collective to convert all that airspeed into RRPM and cushion the touchdown. I don't see any reason you would have to be in an autorotative state for that to work. I'll let somebody else try that one first though :hairraise:
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Ah, 'how to operate your Queisinart, in ten easy steps'.

and yes, ant-torque becomes a big problem over there. But the bugger is you still have to unload the rotor really fast. I'm not that good. maybe we should require some kind of electro-shock cuff on the left tricept. It could be triggered by the torque meter - to low and BZZZZT! 5000 volts slams the collective through the floor! :dunno:
 
I did a posting on Vertical Reference about low fast flight. One guy had it happen -- he had a student practicing a Q-stop roll off the throttle in an R22. He said he was able to get the RPM up as I had surmised -- do a flare. It gave him time to rejoin the needles and do a power-on recovery.

I also flew with a good friend today who is a retired Huey pilot, instructor, and check airman. He told me that in the guard they used to practice low fast engine failures -- instructor would chop the throtle at 40' AGL under cruise power. You don't need to enter an auto (and don't have time anyway), but you just keep the ship straight and treat everything like the flare and touchdown in a normal auto. He said to remember that you have gobs of energy because of airspeed. Makes sense to me.

It's something that maybe everybody should practice in the event of a failure on takeoff.
 
RotaryWingBob said:
I did a posting on Vertical Reference about low fast flight. One guy had it happen -- he had a student practicing a Q-stop roll off the throttle in an R22. He said he was able to get the RPM up as I had surmised -- do a flare. It gave him time to rejoin the needles and do a power-on recovery.

I also flew with a good friend today who is a retired Huey pilot, instructor, and check airman. He told me that in the guard they used to practice low fast engine failures -- instructor would chop the throtle at 40' AGL under cruise power. You don't need to enter an auto (and don't have time anyway), but you just keep the ship straight and treat everything like the flare and touchdown in a normal auto. He said to remember that you have gobs of energy because of airspeed. Makes sense to me.

It's something that maybe everybody should practice in the event of a failure on takeoff.
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That just sounds like the ultimate pucker factor. Then again, in my mind, 40AGL is just a fleeting glimpse out the window on my way (as quickly as possible) up to 10,000 MSL, so that alone is pucker factor to me. :eek:
 
RotaryWingBob said:
I also flew with a good friend today who is a retired Huey pilot, instructor, and check airman. He told me that in the guard they used to practice low fast engine failures -- instructor would chop the throtle at 40' AGL under cruise power. You don't need to enter an auto (and don't have time anyway), but you just keep the ship straight and treat everything like the flare and touchdown in a normal auto. He said to remember that you have gobs of energy because of airspeed. Makes sense to me.

It's something that maybe everybody should practice in the event of a failure on takeoff.
Click to expand...


When I went throught flight school at Fort Rucker in the BCS phase (battle combat skills) we did did a couple low level autos everyday in a OH58A/C. They were really fun to do. You could enter it just above the trees with plenty of airspeed on final and float up and autorotate to the runway . To this day after flying the Blackhawk and a couple airplanes...if I had a engine failure I would feel the safest in a OH-58 (Bell 206).
 
Hey Bob; Excellent writeup. It tells me I've seen these Q-Stops before and thought the pilot was drunk!
I would like a similar thing for IFR. Help out the student pilots and PPL understand what IFR pilots are doing and why.
 
silver-eagle said:
Hey Bob; Excellent writeup. It tells me I've seen these Q-Stops before and thought the pilot was drunk!
I would like a similar thing for IFR. Help out the student pilots and PPL understand what IFR pilots are doing and why.
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Thanks, John.

You make an excellent point about IFR! How about it guys? Somebody want to step up to the plate? I'll make space available on my site if you need it.

Even at my home airport, I'll bet most primary students don't have a clue about what to expect when they hear "VOR A approach".
 
RotaryWingBob said:
Even at my home airport, I'll bet most primary students don't have a clue about what to expect when they hear "VOR A approach".
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I'll second that. When I did my PPL(H) at FDK you would always hear the fixed wing guys do a position report at RICKEY. I had no idea where RICKEY is/was. I asked my CFI (who was a great pilot, but had no real world flying experience) and he said he didn't fly instruments so he had no idea.
Chris
 
I have a question for a real helicopter pilot. Can you fly the helicopter in MS Flight Simulator. I think my record is 37 seconds.
 
foka4 said:
I love the yawstring! (visible in the approach photo on Chopper 101)
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All Robinsons come with them because there's no requirement to have any gyro instruments. In the case of our R44, we have an AI with a tube and ball (no TC) so I generally glance at it to make sure I'm not flying sideways :D
 
Bob, very well written peice. I which the fixed wing pilots at the airport where I got my helicopter rating had read it.
 
Unfortunately, Bob passed away just a few weeks ago from lung cancer. He would have appreciated your comment however.
 
GigG601XL said:
Bob, very well written peice. I which the fixed wing pilots at the airport where I got my helicopter rating had read it.
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t0r0nad0 said:
Unfortunately, Bob passed away just a few weeks ago from lung cancer. He would have appreciated your comment however.
Click to expand...
It just goes to show that while Bob may have passed away his spirit still lives here.
 
FlyNE said:
Great stuff, Bob. Thanks for this.

I do have a question. This may seem kind of stupid, but reading your entry on maximum performance takeoffs I read that you shoot for 40 KIAS...then in the "The "Oh crap, we're not gonna clear the trees" Maneuver" you talk about starting a rearward movement of the aircraft in order to move away from the obstacle.

Like I said, this may be a stupid question...but why can you just go straight up? Wouldn't THAT be a maximum performance takeoff? If you see you're going to hit the trees...why can't you just come to a hover and go up and over?
Click to expand...

I'm not a chopper pilot but you CANNOT go straight up because when you hover or stay in one place for a while because you essentially create a hole of low pressure from the rotors pushing all the air out from under you that you fall into it and will cause you to crash. many of helicopter accident happen because of this.
 
HawkEye007 said:
I'm not a chopper pilot but you CANNOT go straight up
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Actually, you can go straight up. For the reasons you explained (and I have heard it explained differently, but to the same end) flying straight up is a maximum power maneuver, not maximum performance. Think about it. We commonly see helicopters hovering motionless. Here in New York I frequently see police and news helicopters hovering at about 1000 agl in one spot for 20 - 30 minutes at a time.

From a hover, it takes but a small incremental addition of power to go straight up. Maybe some piston trainers can not hover except in ground effect, and these would not have much luck in a sustained vertical climb. Turbines, however, are likely to have the power required.

Best rate of climb would certainly require forward motion to fly out of the disturbed air.

-Skip
(not helicopter rated)
 
Skip Miller said:
We commonly see helicopters hovering motionless. Here in New York I frequently see police and news helicopters hovering at about 1000 agl in one spot for 20 - 30 minutes at a time.
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A couple of things. It takes more power to hover out of ground effect than it does in ground effect. And at 1000 feet, unless there is NO wind, they are not in a true hover. They have a speed into the wind that is EQUAL to the wind speed at that altitude.
 
Very true,.. and his birthday is the 29th,.. sure going to be a tough one for the family as the first since his passing. My grandfather passed away about 3 years ago, and my grandmother has a difficult time at each holiday or his birthday. (they were married 62 yrs.)

Regarding the rotorwash discussion above,... when flying an RC helicopter in ground effect, if you lift off vertically in high power, the rotorwash becomes a problem and will quickly dump you into the ground,.. Yes, ruined a few rotorblades and tailbooms when that occured, till I learned about this and rose up out of ground effect in a slight forward motion. Once out of GE, you climb rapidly and have to throttle back if you want to maintain a hover. The light winds will push you, so while flying stationary in a hover above GE, you are actually having the cyclic tipped into the wind creating a thrust vector of the rotors to compensate for the horizontal component of wind, thus, no cavitating suction of rotorwash like you can experience in GE.

Another place this occurs rapidly is in a vertical decent. You have to really be cautious, and why they are avoided at all costs. Even choppers landing on helipads at city hospitals come in on a low shallow approach, and really only are a true vertical decent the last 1-2 feet.
 
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I got to fly in a T28 called "Chitty chitty bang bang" when I was 8. I even got to take the controls for a little bit. One of the reasons I wanted to be a pilot.
 
RotaryWingBob said:
... This means that if you are looking for a helicopter that's on final, and you look where you'd expect an airplane, you're going to miss the helo because he is going to be a whole lot higher than you expect. ...

http://bobanddusty.com/aviation/chopper101.html
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Wow! After reading this, I believe helos should be restricted to "heliports"!

LOL... Just kidding. I did learn a great deal from your page that I'll keep in mind.

MMM
 
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