Author Topic: Helicopter Questions  (Read 80453 times)

Offline Roland

  • Cockerel
  • ***
  • Posts: 178
Re: Helicopter Questions
« Reply #90 on: May 07, 2006, 07:29:13 PM »
@ firegirl: there are no stupid questions! :)

The way of rotation on the main rotor is actually a matter of gearing. Should mean, the output direction of rotation after all the speed-reductions within the gearbox and all its gears. (Well, does that explain anything? I doubt it) :-\

Ok. Another try. There is one standard: all turbine engine output shafts turn the same way. Viewed from the rear to front of the helicopter the output shaft turns clockwise (cw). Most of the turbine engines turn around 6000 rpm which is quite some high speed and useless on the rotor. Far too fast. So this speed has to be reduced. Down to approximately 300 to 400 rpm. This reduction depends on the diameter of the rotor and is done within the main-gearbox. So engineers sit down and calculate some things like ratio of reduction, weight of the gearbox, available size of the gearbox and will end with any direction of rotation of the main-rotor. Viewed from above it ether turns clockwise (the European and Russian way) or counter clockwise (ccw).

European and US American companies tried to stick with the direction of rotation and had spent lots of money and efforts to do so. But with more modern times the direction of rotation is just a result of the gearing within the main gearbox. Btw, almost all tail rotors turn with the upper blade back. This has aerodynamic reasons. 8)

It is hard to tell but it seems the rotor on those Cessna turns ccw. Please donít beat me if itís wrong. :P
If helicopter flying would be difficult, engineers would do it.

Offline Frank N. O.

  • Alpha Rooster
  • *****
  • Posts: 2446
  • Spin It!
Re: Helicopter Questions
« Reply #91 on: May 07, 2006, 08:37:34 PM »
Firegirl: I never ever thought about what direction they turned so I think it's a very good question and Roland gave a great answer, especially about the tailrotor too  |:)\

And speaking of rotors, what's the purpose of checking the rotor-torque? In sims you can go well over 100% but I read an article about a person flying both FS2004 helicopters and real life fixed wing planes that tried a real Jet Ranger and he said it flew smooth and fine and didn't need to go over 85%.

Also, is there a checklist for a real helicopter, like a Gazelle, AStar or JetRanger available for the public like I've seen with GA planes? I'd like to see one because I downloaded an add-on to the std FS2004 JetRanger that gave a much more detailed start-up sequence and extra gauges and switches, like generator output, CO (I think) throttle settings etc. that had to be followed to start up and that was a lot more than the default start where the aircraft is running. That's the really bad thing with FS2004, almost no emphasis on the real start-up and shut-down sequences and per default all planes are running when the sim starts.

Frank
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."
ó Leonardo da Vinci

Offline Mike

  • Supreme Overlord
  • Alpha Rooster
  • *****
  • Posts: 3379
Re: Helicopter Questions
« Reply #92 on: May 07, 2006, 10:11:10 PM »
So, does anybody know why the rotors on a Bell turn one way and the ones on the french helicopters turn the other?

I always thought when the Americans and the Russians took over Germany at the end of the war, they took one of those German Focke-Wulf FW-61 the Germans used to fly around with indoors and split it in half.

The Americans got the left gearbox and the Russians the right one (or vice versa) and that's how they went from there . . .

TA DA !!   ;D :D

Explains it, doesn't it?!?  ;)
Dear IRS: Please cancel my subscription.

Offline Frank N. O.

  • Alpha Rooster
  • *****
  • Posts: 2446
  • Spin It!
Re: Helicopter Questions
« Reply #93 on: May 07, 2006, 10:39:05 PM »
ROFL that's a good one!

Frank
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."
ó Leonardo da Vinci

Offline Gulfstream Driver

  • Chicken Farmer
  • Alpha Rooster
  • *****
  • Posts: 1070
Re: Helicopter Questions
« Reply #94 on: May 07, 2006, 11:42:36 PM »
Frank, you should be able to find Flight Manuals (FM's) or Pilot's Operating Handbooks (POH's) for helicopters as well as fixed-wing at larger FBO's.  Unfortunately, they can be expensive, but they have everything you need to know about the aircraft.  If your FBO doesn't have the one you're looking for, they should be able to order it for you.  Unless you know a nice helo pilot (*cough* Mike *cough*) that would be willing to make some copies of the important pages for you...   ;D
Behind every great man, there is a woman rolling her eyes.† --Bruce Almighty

Offline Mike

  • Supreme Overlord
  • Alpha Rooster
  • *****
  • Posts: 3379
Re: Helicopter Questions
« Reply #95 on: May 08, 2006, 12:16:57 AM »
I have all the checklists of course.
We usually use "abreviated" checklists and I am sure I can get you some. And then there are always the pages out of the POH. Let me know what you want.
How much detail are you looking for?

About the torque thing:

It's usually a transmission limit. All the helicopters I fly (Rangers and AStars) have some sort of a hover limit (5min or under a certain speed and so on...) and that's usually 100% torque but not always.
That limitation would be the top of the "yellow arc" on the gage.

For forward flight we have the "green arc" with the limit being called "maximum continous power" which happens to be 85% on the Jet Ranger. So your friend is right, it flies quite nicely at 85% torque.
In the Ranger if you would pull the power (collective) in forward flight (above 80kts) past 85% you would get into what they call "mast bending" (pretty much self-explanatory) due to the high speed and torque forces on the mast.
So, it should be avoided. (actually MUST, not should)
In a hover (and I am now talking about the Ranger only) you can pull 100% torque for 5min (sling loads, high performance take-offs, and so on). If you overtorque the aircraft then (and I have seen it done) you will most likely start making metal in your gearboxes because you're stressing them past their limits.

There is a lot of other things to know and watch out for and I am guessing that a simulator, even a good one, probably won't take all that into account.

And why isn't there a stop on the collective that would keep you simply from overtorquing?
Any good guess?  ;)
Dear IRS: Please cancel my subscription.

Offline Frank N. O.

  • Alpha Rooster
  • *****
  • Posts: 2446
  • Spin It!
Re: Helicopter Questions
« Reply #96 on: May 08, 2006, 12:44:43 AM »
I noticed one single thing about the sim Gazelle, it was a FS2002 version but I found a complete and FS2004 upgraded version and it doesn't overheat so at least that's done. Back to reality then thank you very much for you info, and yes Mast Bending does explain itself very well, yikes! About the lack of a stop on the collective then my guess here shortly before I need to sleep is that the torque isn't a constant but varies due to speed, altitude, load (a part of the first two) and maybe also other factors. And now it's time to get some sleep, I got a long drive tomorrow.

Frank

P.S. Mike, just in case you didn't see the other post, there is still that PM in case you forgot it due to an overload of more important work. One reason to keep reminding you is that I want to be sure I didn't say something you took badly in the first one.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."
ó Leonardo da Vinci

Offline SkyKing

  • Newbie
  • *
  • Posts: 42
Re: Helicopter Questions
« Reply #97 on: May 08, 2006, 01:13:10 AM »

True, but you seem to be a high time pilot. Keep that in mind.


Care to guess how I got that way?  ;)

Quote
I can pretty much get in any helicopter on any certificate right now and on one occasion it even helped the owner lower his insurance because of all my experience.
But put yourself in the shoes of one of our young guys in the forum here. They are the most sold and usually cheapest helicopter out there....
They DO have to consider the issue.
Why talk a young guy out of a helicopter you have never even flown yourself?  ???

The first answer that comes to mind is that I've never jumped into a shark tank, either . . .   ;)
 
Quote
( I have seen other helicopters crash too. What about things like the tailrotor issue on the Bells, hydraulics on the AStar, T/R AD on the 500C, and so on....)

You missed my point.  My major problem is the official stance of the company, that the pilot was automatically the failure point, not the helo.
« Last Edit: May 08, 2006, 01:23:02 AM by SkyKing »

Offline SkyKing

  • Newbie
  • *
  • Posts: 42
Re: Helicopter Questions
« Reply #98 on: May 08, 2006, 01:16:27 AM »
Everything I've ever known and believed to be true...gone...   :-\  How can a world exist where Cessna wings whirl around above the fuselage? 

Never see the "Aerobat" models, did you . . ?


Offline SkyKing

  • Newbie
  • *
  • Posts: 42
Re: Helicopter Questions
« Reply #99 on: May 08, 2006, 01:17:18 AM »
So, does anybody know why the rotors on a Bell turn one way and the ones on the french helicopters turn the other?
Is this a stupid question?

And, which way did the rotors on the Cessna helo turn?

Toward bankruptcy.


Offline Gulfstream Driver

  • Chicken Farmer
  • Alpha Rooster
  • *****
  • Posts: 1070
Re: Helicopter Questions
« Reply #100 on: May 08, 2006, 01:24:57 AM »
Everything I've ever known and believed to be true...gone... :-\ How can a world exist where Cessna wings whirl around above the fuselage?

Never see the "Aerobat" models, did you . . ?



Actually, I flew one of those little 150 Aerobat bastards from Fargo to Riverside, CA. †My ground speed the first two days never got above 60 kts. †Got stuck in Amarillo for two nights due to T-storms. †It was "technically" an IFR bird, but had been spun so much the gyros didn't work. †Luckily, the last two days were clear and a million, I was able to get from Amarillo to the west side of Phoenix in one day, then kicked on into Riverside 5 days after I left.
Behind every great man, there is a woman rolling her eyes.† --Bruce Almighty

Offline Gulfstream Driver

  • Chicken Farmer
  • Alpha Rooster
  • *****
  • Posts: 1070
Re: Helicopter Questions
« Reply #101 on: May 08, 2006, 01:29:32 AM »
Do you guys have white, green, and yellow arcs on your airspeed and torque guages?  Are the limitations the same as fixed wing?
Behind every great man, there is a woman rolling her eyes.† --Bruce Almighty

Offline Mike

  • Supreme Overlord
  • Alpha Rooster
  • *****
  • Posts: 3379
Re: Helicopter Questions
« Reply #102 on: May 08, 2006, 02:09:33 AM »
Do you guys have white, green, and yellow arcs on your airspeed and torque guages?† Are the limitations the same as fixed wing?

Hmmm... could be. I haven't flown stuck wing in so long...

We have:
green: normal operating
yellow: some sort of limit range (either 5 min, or below a certain speed, or smthg)
red line: never exceed
red triangle: transient limit

The Rangers have a blue line for max. Autorotation Speed which is different I believe.
The AStar has a white and red hatched line for max. auto.

I don't think we have white arcs (maybe because we don't have flaps...)
Dear IRS: Please cancel my subscription.

Offline Mike

  • Supreme Overlord
  • Alpha Rooster
  • *****
  • Posts: 3379
Re: Helicopter Questions
« Reply #103 on: May 08, 2006, 02:17:01 AM »

You missed my point.† My major problem is the official stance of the company, that the pilot was automatically the failure point, not the helo.

Sorry, I might have.
I still believe the R22 is reasonable safe to fly.

About the stance of the company. I ran into the same thing with Eurocopter about the collective lock that seems to wear and makes the aircraft take off uncommanded (long story)
They never changed anything in the POH or the maintenance recommendations and I think it's because if they do, they would admit that there is a problem and all the companies who crashed one of their ships because of that reason will sue them...

Can it be that Robinson was afraid of a lawsuit?

(again I don't get paid by Robinson nor do I want to defend what they did, I just didn't want talk a young guy out of a career which seems to get pretty good lately. (my guys make $68,000 a year and up) We NEED more helicopter pilots right now. I am sure you are aware of that as well)
Dear IRS: Please cancel my subscription.

Offline Roland

  • Cockerel
  • ***
  • Posts: 178
Re: Helicopter Questions
« Reply #104 on: May 08, 2006, 06:23:18 AM »
@ Torque: let me complete Mikeís statement. On most helicopters the measured (and indicated) torque value is the torque produced by the engine BEFORE it goes to the gearboxes. Boxes? Yes, there are at least two boxes: main rotor gearbox (MGB) and tail rotor gearbox (TGB).

The power available from the engine, indicated as torque, is to be shared between those two boxes. In hover the TGB takes a lot of this available power. Depending on the weight, wind and so on it can be up to 30%. In forward flight the vertical fin takes a lot of load off the TGB and the available power can be sent to the MGB.

On some other helicopters, mainly more modern series like the Bell 412EP, the measured torque is the true mast torque. This indicates the true torque on the main rotor mast produced by the power of the engine(s) to overcome the drag of the main rotor blades.

100 points out of 100 go to Frank. The answer to Mikeís question of the collective-stop is right. (Medal icon placed here)
To my knowledge there are no flight manuals for helicopters available on the web. The companies creating and handling these manuals make an awful big money with these manuals. Therefore I cannot imagine finding those for free somewhere. And, most important, these manuals are to be kept on the latest status by amendments. Mike can make copies, I can do so too. Let me know and I will try to send it to you.
If helicopter flying would be difficult, engineers would do it.