colective / throttle

[Ed Hunter]

trying to work out the difference between the collective and the throttle control

reading the manual in one part it says to use the collective to increase/decrease altitude. but in another it says the altitude is changed by adjusting engine power. so what is what? page 6-17

 

and on a side note the auto pilot for altitude when set will is it supposed to keep me x meters above ground so it i fly up a hill i will stay 30 mts off the ground or is it set to xx metres above sea level ?

[joey45]

The throttle controls the engine speed.. KEEP IT ON AUTO!! page up twice

 

The collective controls the Altitude of the heli

 

and on a side note the auto pilot for altitude when set will is it supposed to keep me x meters above ground so it i fly up a hill i will stay 30 mts off the ground or is it set to xx metres above sea level ?

never tried it.... I don't use the Alt Hold when flying... infact I only use the 3 other dampers when flying. Edited September 13, 2009 by joey45

[nemises]

Hi Ed,

The Throttle controls the RPM of the engine, and the collective contrls the Pitch of the Rotor blades.

Technically both can affect the amount of lift generated by the blades, but only the Collective is actually meant to do this.

 

The Throttle is designed to operate in an "automatic" mode, where it will govern fuel flow to keep the engine RPM fixed between it's lower and upper operational values without any pilot intervention.

 

It is important not to use throttle as a contrl mechanism for lift , as the rotor RPM also runs the generators that supply AC power, as well as charge the batterries for DC power...if rotor RPM drops below a threshold (70%) then AC power can no longer be generated, and many of the electrical systems will stop working.

 

So, long story short, do NOT map the throttle axis, only use the "Pg Up" and "Pg Dn" keys to control the throttles position.

Using these keys, the throttle will move to 4 differnt pre-defined positions

 

1) Idle (this is where it will start on the ground and for engine start)

2) Low (this would be used for on ground testing)

3) Automatic (This is where teh throttle should remain after startup at ALL times unless...)

4) Emergency (This setting increases the RPM to it's higher limit incase one of the engines is in operable...thus the engine that is left will create more tourque at a higher RPM)

 

So, after system startup, you would press "Page Up" twice, the RPM governors will then keep the engine spinning at it's optimal RPM, and you will use Collective (ie. rotor blade pitch) to increase or decrease the amount of lift that the blades have.

 

As for your second question,

The Altitude Hold autopliot has two modes:

1) Barometric (This uses the Barometric / sea level altimeter)

2) Radar (This uses the Ground distance radar)

 

Using the Barometric altitude hols will keep you at the same altitude in relation to sea level regardless of hills, valleys, dips etc..

Using Radar will (assuming you are less than 300 Mtrs) keep you at a fixed altitude as relates to the Ground, which means it will automatically climb and descend (by increasing / decreasing colletive!) to keep your relative altitude the same to the ground.

 

The switch to change between Barometric and Radr is on the Right hand panel near the Datalink ID numbers

Edited September 13, 2009 by nemises

[Pogo]

As Joey45 says, keep your throttle on Auto and use the collective to control altitude.

 

On the Autopilot panel there is a switch to control whether the Autopilot will use Barometric Altitude(above sea level) or Radar Altitude (above ground level). The switch is labeled BR (barometric) and RD (Radar).

 

Keep in mind that the Autopilot only has 20% control authority. So if you are Radar mode and you come up on a hill that requires more than 20% collective increase to clear, then manual input will be required.

 

Also the Altitude Autopilot channel must be engaged and the Altitude Autopilot is set when the Collective Brake is engaged (F key). The Collective must already be set relatively close to 0 on the VVI (vertical velocity indicator).

 

I hope this helps.

 

Cheers,

Pogo

[Ed Hunter]

thanks for the explanations the throttle looks simple enough out on auto and leave alone. (bought myself a ch throttle quadrant and was going to assign throttles to a axis )

 

have to start to find out the auto pilot switches and key controls.

had the game a while but always used easy flight now i have moor time want to fly the thing properly and later when i can avoid hitting the ground start with the weapons then maybe join a flight on line

Stu

[Waldo_II]

This was confusing to me when I began, and I don't quite think the explanations above are full in detail.

 

First, a lesson about rotor blades. Rotor blades are an airfoil design, so they naturally will generate lift when moving. However, when flat, the rotors will not generate enough lift to actually bring the helicopter into the air. in order to amplify the amount of lift being generated, the rotors are rotated along the axis parallel to the ground moving out from the center of the rotors to the end of the rotor, creating an angle.

 

Imagine this: you are in a body of water. You put your hand out in front of you with your palm facing the bottom, flat. You move your arm straight across from the right to the left. Your hand comes into contact with a fairly little amount of water, so there is little resistance, and it is easy to move your hand. Now imagine that before you moved your arm, you rotated your hand 45 degrees, so your right hand palm faces down and to the left. Now when you move your arm across, it becomes more difficult to move it because it comes into contact with a lot of water, and it wants to go upwards at a 45 degree angle.

 

The same is true for rotor blades. When you rotate the blade, it will come into contact with more air, it will push against more air, and according to Sir. Isaac Newton's third law of motion, the air pushes back against the rotor blade, and pushes the rotor blade up, and you have lift.

 

"Collective" stands for "collective angle," meaning the collective angle of all of the rotor blades. The one lever will rotate all of the blades collectively, all at once, in unison, etc. That is where the term "collective" is from.

 

Now, when rotor blades are pushing against more air, there is more resistance. When there is more resistance, the blades will slow down. In order to counter this effect, the collective is tied into the throttle. When you increase collective, the helicopter assumes rotor RPM will decrease because of the increased resistance with the air, and will apply more throttle according to collective pitch. The next time you are in the cockpit, take a look at the throttle (on the left side, bottom, in the rear, the yellow (or red, I cannot remember) levers. Put the throttle in the "auto" position (with "page up" twice, of course), and increase collective. You will notice that the throttle levers move along with the collective. This is what I mean when I say that the throttle and collective are linked.

 

Bonus lesson: think about the effect of collective pitch/air resistance on rotor RPM when performing auto-rotation landings. (Auto-rotation is the effect of the rotors spinning by themselves without any energy input from the engines. Such landings are usually only performed when the engines are destroyed, out of gas, or otherwise not working.) If the engines go out and you are high up off the ground, put your collective at minimum to reserve rotor RPM for when you need it down low. If you put your collective at maximum when you don't have engine power, rotor RPM will slow down to a dangerously low number, and when you reach the ground you won't have enough rotor RPM to break the fall/land safely. Put collective at minimum to reduce air resistance and preserve rotor RPM, and when you are close to the ground, ready to land, increase collective and used that stored energy in the rotors to get that lift when you need it.

[nemises]

thanks for the explanations the throttle looks simple enough out on auto and leave alone. (bought myself a ch throttle quadrant and was going to assign throttles to a axis )

 

have to start to find out the auto pilot switches and key controls.

had the game a while but always used easy flight now i have moor time want to fly the thing properly and later when i can avoid hitting the ground start with the weapons then maybe join a flight on line

Stu

 

If I had a quadrant , I'd assign the throttle axis also....its just cool.

I do not know how to tell though if the throttle is at "auto" setting or not though..I assume there is a deadzone or detent on the real throttle levers?

[morg]

if you press ctrl+enter you get a window showing the cyclic, pedals, collective and also the current throttle position

[nemises]

yep, but where on the throttle's axis is "auto" ... using digital controls (pg up/pg/dwn), no problem, but using analogue ..?

[morg]

ah, that i don't know, but i guess around 3/4ths of the way

[P5138]

An easy way to find out is to check the throttle handles (and listen to the engine RPM) while on the ground as you go up in throttle. Once you start to go into the latch where the throttles lock into auto you'll hear the RPM drop and auto mode is engaged. (I think it's a little bit above 75%) Once you find it, you can just note the location in the future.

[AlphaOneSix]

I use one of the dials on my X-52 throttle, and the middle detent (50%) of the dial corresponds perfectly with the AUTO setting of the throttle in the aircraft.

[dburne]

I think I have the same here, I assigned the RNG knob on my Cougar to the throttles, while not completely sure I think the middle detent might be the auto setting...

I will have to move it a little and listen to the engines to see if I can tell.

[miguez]

Now, when rotor blades are pushing against more air, there is more resistance. When there is more resistance, the blades will slow down. In order to counter this effect, the collective is tied into the throttle. When you increase collective, the helicopter assumes rotor RPM will decrease because of the increased resistance with the air, and will apply more throttle according to collective pitch. The next time you are in the cockpit, take a look at the throttle (on the left side, bottom, in the rear, the yellow (or red, I cannot remember) levers. Put the throttle in the "auto" position (with "page up" twice, of course), and increase collective. You will notice that the throttle levers move along with the collective. This is what I mean when I say that the throttle and collective are linked.

 

Hi Waldo,

 

Great explanation! The only thing I'd say is that the engine throttle is controlled electronically, the yellow throttle handles in the cockpit, by the collective stick, are only a mode selector. They don't actually move to increase engine throttle, their whole structure (including the base) moves with the collective so that their relative position is always the same, should the pilot try and reach them for an adjustment.

 

The only way to see that the throttle is increased when you increase the collective is by watching the tachometer, or engine RPM gauge, which is the one located to the right of the ABRIS with a third of its circumference painted red. Sitting on the ground with throttles in auto and collective all the way down, your engine RPM should be at about 87%, depending slightly on atmospheric conditions. Once you increase collective you will see engine RPM move up to whatever the engine fuel control unit decides is required to maintain rotor RPM, all the way to 100% engine RPM.

[-Bazong-]

yep, but where on the throttle's axis is "auto" ... using digital controls (pg up/pg/dwn), no problem, but using analogue ..?

 

One can change this by setting the axis as a slider and setting saturation..

[AlphaOneSix]

No electronic fuel controls on the TV3-117, it is a direct, physical linkage from throttle and collective to the engine fuel control.

[miguez]

No electronic fuel controls on the TV3-117, it is a direct, physical linkage from throttle and collective to the engine fuel control.

 

Hey A16, thanks for the correction! So it is the motion of the collective going up that will increase engine throttle then, huh? That's great info!

 

By the way, any more info on the engine fuel control? Is it mechanical?

[AlphaOneSix]

By the way, any more info on the engine fuel control? Is it mechanical?

 

The fuel control is purely mechanical, although there is an electrically operated actuator to decrease fuel flow at the direction of the engine governor to prevent overtemps.

 

As far as more info, if you have something specific in mind, let me know. I have an extremely extensive collection of documentaiton on the TV3-117VM, since I work on them all the time. The VM and the VMA are virtually identical.