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Old 04-25-2008, 12:39 PM
cutty01 cutty01 is offline
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I don't get the Throttle Hold on RealFlight???

Hi, I am looking for a seasoned pilot to help me understand the Throttle Hold switch on a transmitter (specifically the Interlink). I have searched the posts and read the manual but I am still curious on the correct use of the helicopter throttle hold on RealFlight G4.

I just installed and started using RealFlight G4 today. I have never flown RC helicopters nor used a helicopter simulator. I have configured the Interlink controller. When I select any helicopter, there is no throttle response when using the controller (planes work fine). The only way I can get a throttle response is to flip the Throttle Hold switch. The helicopter RPM immediately speeds up and only then does the motor respond to the throttle toggle.

Is this how the Heli Sim its supposed to work? Is this true in real life when flying RC helicopters in the field?

Thank you in advance for your help.
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  #2  
Old 04-25-2008, 12:50 PM
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Adam Taylor Adam Taylor is offline
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Yes, this is how real helicopters work.

You'll notice that with the throttle hold in the appropriate position for the blades to spin, the rotor won't stop spinning even with the throttle all the way down. In real life, your aircraft doesn't just magically appear on the helipad. You need a way to stop the blades so you can pick the heli up and set it down without slicing up your wrist.
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Old 04-25-2008, 01:27 PM
cutty01 cutty01 is offline
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Thanks Adam.
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Old 04-25-2008, 01:34 PM
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phrank phrank is offline
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Helis can be a bit tough to understand initially, but the web is a wonderful resource for some detailed answers, Google (Throttle Hold):

For now, here is the short answer:
- Prior to takeoff, the 3-position switch should be at Normal (lowest position) and Throttle hold enabled.
- When you are ready to lift-off, disengage throttle hold, and spool up slowly.
- When you are ready for stunts, you can engage the next modes of the 3-position switch, which you are most likely not ready to conquer yet.
- When you are ready to land, pick a spot and let her down gently. It's good practice to re-engage throttle hold.

Good Luck,
Frank...
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Old 04-25-2008, 01:58 PM
cutty01 cutty01 is offline
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Thanks Frank. I did do a preliminary Google search but most sites referenced using the Throttle Hold for practicing auto-rotations. I was not finding why I need to use it when I was on the ground.

I am finally understanding. My original understanding was that I was turning "on" or "engaging" something to get the motor to spool up. But in fact its opposite. I am turning "off" or "disengaging" the throttle hold. When its "on" or "engaged" its a safety feature. Thanks again.
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  #6  
Old 04-25-2008, 03:22 PM
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Jimmy Newton Jimmy Newton is offline
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Yes, it is a safety measure but, also throttle hold 'simulates' an engine out or dead stick senario, whereas the pilot then must 'autorotate' to get the aircraft safely on the ground. It is a good skill to learn right after you learn to hover in all four orientations, because one day in real life, your heli may 'flame out' on you and you'll have to autorotate it to the ground. This one skill, once mastered can save you untold amounts of money in real life, especially if your motor is picky about its mixture settings.
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Old 04-25-2008, 05:10 PM
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phrank phrank is offline
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Funny you should mention that Jim,

Ironically, I've seen people bust blades, bent paddles, and other damages practicing that maneuver. It's overdone IMO.

If you're a 400-class heli of less you're best off leaving that maneuver alone.
Small helis just don't have the rotor momentum to succesfully complete a landing.
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Old 04-25-2008, 05:40 PM
Sirus Sirus is offline
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Momentum

Interesting....

It's not a question of the amount of momentum, it's a question of the style of Autorotation.
I have to refer to RL, as I haven't done any RC autorotations - except on G4...

Let's start with a Jetranger (Bell 206)
There's a fair amount of inertia, and when you get a flame-out (or me being nasty and setting your throttle to flight idle to test you), you have between 3 and 10 seconds to get the collective lever down (Depending upon whether you are climbing or descending etc.). Collective is what you term as throttle, but is in fact the collective pitch of the blades. Basically, the engine is either on at full power or off, it doesn't work in between, especially on an Allison 420shp turbine - and in RF, this is the throttle hold, this switch is switching your throttle between the 65% flight idle and 100% working value.

OK, so, when the engine goes to flight idle, we tend to get the collective down quick, almost to the bottom to maintain rotor rpm, then maybe lift it a tad just so the blades don't overspeed (they have a max value in RL). Then, ensuring you have around 40kias (knots indicated airspeed), you simply go down at around 45 degrees towards your chosen point.
When you get around 1 to 1.5 rotor diameter from the ground, you are going to do a round-out and flare (just like a normal airplane landing), but the flare is going to be more pronounced to almost stop forwards momentum. When flaring, lift the collective to stop excessive rotor rpm, then using cyclic, level the beast (whilst lowering the collective to keep headspeed) and as it sinks, use more collective to cushion the touchdown.

That's a standard auto in a Bell 206... Now, let's look at a VERY different beast, a Robinson R22, with virtually no momentum whatsoever....
When you lose the donk (not the donk from crocodile dundee, but the donkey or engine), you have between 0.5s and 1.5s to get that collective to the floor, your life depends upon how quick you are in this thing, if you are climbing at full power and haven't got the collective down in 0.5s, you are dead! When it's fully down, again, simply regulate rotor rpm by lifting the collective slightly to avoid overspeed.
Now, we fly at around 60kias (faster you will notice as it needs it) and when getting around 15.-2 rotor diameters from the ground, flare like heck (old english word, means LOTS), to get the speed down (again, regulate rrpm with a bit of collective), then level it and use a bit of collective to cushion landing.

OK, notice the difference...

The R22 is like your 400 class heli, less rotor momentum, means you have to keep a higher fwd speed and use it more like landing a plane, flaring lots to get the speed down at the end and it all happens very quickly.
The Bell 206 is much more sedate, you can even sometimes lift it up after you have landed, turn it around and land it softly again because of that inertia.

What I have to say is that you SHOULD do autos with your 400 class it's entirely possible, get the collective (what you term the throttle) down all the way and keep forwards momentum with a flare at the end, make the flare at Iwould guess around 3-4 rotor diameters for a model. BUT, guess what, that's why we have G4, so that you can actually practise this! Then, when it's nearly at the flooor, a little collective to cushion the landing.

Anything that flies can do auto's successfully, it just required different techniques.

Go try it guys, it's quite fun successfully auto-ing something without much inertia!


Sirus
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Old 04-25-2008, 06:15 PM
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phrank phrank is offline
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Autorotations on a 450 is possible, but tricky and you do need forward speed,
I've seen it done many times just for fun but only in very capable hands.
It is considered more of a stunt, the "cherry on top" to finish off a performance.
You only get one shot at getting it right, everything happens so quickly.

In not so capable hands such as my own, they will cost money more often than not.
I'm in the don't try it on a small bird camp.

Cheers,
Frank...
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Old 04-25-2008, 07:41 PM
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Jimmy Newton Jimmy Newton is offline
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Quote:
Originally Posted by phrank
Funny you should mention that Jim,

Ironically, I've seen people bust blades, bent paddles, and other damages practicing that maneuver. It's overdone IMO.

If you're a 400-class heli of less you're best off leaving that maneuver alone.
Small helis just don't have the rotor momentum to succesfully complete a landing.
That's entirely correct, people that are learning to 'auto' do indeed break things. It is very difficult to do with a smaller machine because, as was pointed out above, the blades have less enertia because of the lack of mass. Those with larger helis, 50 size and up and even the new Trex 500 can do a respectable auto with no muss or fuss. I for one would not even attempt an auto on a Trex 450 or Blade 400, simply because the timing is critical. As Sirus pointed out above in the R22 example you have to have a much quicker response with a smaller heli. Same is true in RL RC. A Trex 600 can start applying collective at about 20 feet and still set down soft as a feather. With a Trex 450 size heli, you have about 3 feet to do the same thing.
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Old 04-25-2008, 09:00 PM
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DirtyHarry3033 DirtyHarry3033 is offline
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Quote:
Originally Posted by Adam Taylor
Yes, this is how real helicopters work.

You'll notice that with the throttle hold in the appropriate position for the blades to spin, the rotor won't stop spinning even with the throttle all the way down. In real life, your aircraft doesn't just magically appear on the helipad. You need a way to stop the blades so you can pick the heli up and set it down without slicing up your wrist.
Huh?

With my heli's both in RF and also back when I flew RC in RL 13 years ago, the blades DO stop spinning (eventually) if you put the throttle at idle. That's the way it's supposed to work, at least with nitro heli's. Don't know about electric heli's.

(If in RF the blades aren't supposed to ever stop unless you engage throttle hold, then I guess my RF has a bug )

My RL heli (Kalt Enforcer ZR) had a centrifugal clutch that was disengaged at idle, and would start to engage as you throttled up. I would imagine all nitro heli's are the same way. Certainly seems to be simulated this way in RF.

The way I stopped my blades back in real life was to land, reduce throttle to idle, let the blades slow down a few seconds then walk over to the heli and CAREFULLY press the heel of my hand gently on the rotor head to stop the rotation. (Saves a good bit of waiting...) Then kill the engine before picking the heli up. I never once used throttle hold to stop the blades after landing


DH
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Old 04-26-2008, 03:13 AM
Sirus Sirus is offline
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Apologies

My apologies guys,

When I said - Go try it....

What I meant was get your RealFlight out and go try it there...
As Phrank and Jimmy Newton said, it's REALLY difficult, and I concurr with this,
you are likely to break something...
But that's where RealFlight comes in...

When you can do it right 100% of the time in RF, then you may just find that you can get your 400 down safely, and it may one day be a lifesaver.

Sirus

Edit: -

Sorry, should have also emphasised....


Throttle vs collective.....

The Throttle hold controls the engine on CCPM machines, it's either ON or OFF, this means that the motor is running 100% or 0%, there is no in-between...
What you know as the throttle on a CCPM machine is in fact the "Collective Angle of attack of all the blades" - When at Zero, there will be no "thrust", when at +10, there will be lots and when at -10, there will be lots of negative thrust.

On RL helis, with piston driven machines, you start the engine (with a key, just like a car) and when it's idling, you engage the clutch (electric/hydraulic/mechanical), on an R22, it's simply a little electric switch. Then you fly at around 100% with a governor taking care of the rpm (although when first brought out, they didn't have a governor and the "Twist Grip" on the end of the collective was turned in micro adjustments to keep rpm at around 100%.

In the Jetranger, the clutch is an oil pressure device. You press the starter and keep it pressed, this starts the engine spooling, and at 12-15% rpm, you introduce fuel. Then, it all starts to light up, and you then see the rotors start turning due to the automatic clutch at around 25% and at 58%, you can then stop pressing the starter and the beast should then settle at 65% (which is called Ground Idle). Then when you want to fly, you use the twist-grip throttle on the end of the collective to set it at 100% for flying and a governor or fadec takes care of it from then. In a Twin Squirrel (AS355) the throttles are levers on the quadrant above the pilots head rather than a twist grip.

This is similar to a Variable Pitch prop (V.P Prop) in real life, although there you have the prop and throttle control and in RL, you fly to two settings....

On Take off, you have the pitch fully fine and use the throttle... When you have taken off and are climbing, you can then increase the pitch (this is done by pulling back the pitch lever to reduce the rpm and is effectively a bit like changing into 2nd and third gear). So, then from a take off of full power and 2700 rpm, you may do a cruise climb at 24" and 2500 rpm, follwed by a cruise at 22" and 2300rpm
When you come back for a landing, you will again decrease the pitch to keep the rpm high (just like approaching traffic lights, you don't want to be in 4th gear, you want first for a quick getaway).


Sirus

Last edited by Sirus; 04-26-2008 at 06:09 AM.
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