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R22 related questions from a plank driver

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Old 29th Mar 2013, 08:20
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R22 related questions from a plank driver

Hello folks
I am about to take a training lesson on the r22 - bear in mind i am a plank driver so dont go too hard on me!- and i have done some reading on helicopter flying and on the r22 - you could call me a geek - and there are a couple of questions - a couple of hundreds i should say! - that spring to mind.

As far as i understand the clutch assembly allows the starter to crank the engine without having to overcome the drag from the mrs and basically consists of a lower and of an upper sheaves, of a set of V belts and of an electrical motor: during start the belts connecting the upper and the lower sheaves are loose, disconnecting the engine from the mrs while once the engine is started as the CLUTCH switch is flipped to the ENGAGE position, the electrical motor will drive an actuator located between the pulleys, moving the upper sheave up tensioning the belts, bringing the load of the mrs on the engine without stalling the engine, as reflected by an increase in rrpm's and triggering a panel mounted orange CLUTCH light. When the proper tension is reached a sensor in the actuator will de-energize the actuator extinguishing the CLUTCH warning light.
Should the belts fail to attain the proper tension due to them being worn out as the actuator reaches its fully extended position, an over travel microswitch will prevent the warning light from extinguishing IS THAT CORRECT? IS THE MICROSWITCH DE ENERGIZING THE MOTOR AS WELL?
As the DISENGAGE position is selected the electrical motor will drive the actuator in the opposite direction, lowering the upper sheave and detensioning the belts.
Should the CLUTCH warning light flicker or illuminate for more than 5 seconds during flight indicating that the electrical motor is trying to tension the V belts, an imminent belt, upper and/or lower sheave failure can be anticipated. IS THAT CORRECT.? And IS IT USING THE SAME MICROSWITCH AS DURING STARTING?
WHAT DO YOU DO IF THE CLUTCH WARNING LIGHT STAYS ON? I have no access to a poh!

In the semi rigid rotor system driven by a belt system the freewheel unit consists of a sprag clutch, i understand the basic functioning of the sprag clutch however i am not quite sure why i read that there are an inner shaft and an out one with the inner shaft running through the inner inserted in the inner race of the sprag clutch transmitting the engine power fwd to the mr gear box and the aft to the tr gear box, what about the outer one? is it just a fairing?

Is the only reasons for the coning hinges to allow the blades to flap up during coning or they serve any other purpose throughout the flight? Dissimetry of lift and so on?

Many thanks for your willingness.

Baobab72
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Old 29th Mar 2013, 08:50
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You can download the POHs from the robinson website
Robinson Helicopter Co.

If the clutch light stays on for 10 seconds or more (used to be shorter) in flight you are to pull the clutch circuit breaker and land as soon as practical or immediately if there is vibration.

The clutch light is on if the actuator is tensioning or de-tensioning the belts so it could be a sign of impending belt failure or a failure of the microswitch and the belts are being de-tensioned.

It does come on from time to time in flight as the belts warm up etc... the longest i've counted is 8 seconds
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Old 29th Mar 2013, 08:50
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You've got an internet connection. All the manuals, IPC and POH are on the Robinson website. As far as I remember it's the same micro switch,
IF the light stays lit for more than 5 seconds and you are losing rotor rpm it's time to enter into an auto and land.
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Old 29th Mar 2013, 09:37
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To answer your questions: (but I haven't been in an R22 since 1996)

"As far as i understand ..... When the proper tension is reached a sensor in the actuator will de-energize the actuator extinguishing the CLUTCH warning light.
Correct. Disengaging the clutch is done by pulling the tail rotor driveshaft downwards (bending it) until the belts are slack. There is a down limit switch to stop it pulling too far, and an upper limit switch to stop it over-tensioning the belts.

"Should the belts fail to attain the proper tension due to them being worn out as the actuator reaches its fully extended position, an over travel microswitch will prevent the warning light from extinguishing IS THAT CORRECT? IS THE MICROSWITCH DE ENERGIZING THE MOTOR AS WELL?"

If the tension doesn't reach the right level, the motor keeps trying to extend the actuator - that is why they say to pull the circuit breaker if the light remains on after 5 seconds in flight. Don't want to burn it out.


"Should the CLUTCH warning light flicker or illuminate for more than 5 seconds during flight indicating that the electrical motor is trying to tension the V belts, an imminent belt, upper and/or lower sheave failure can be anticipated. IS THAT CORRECT.? " Yes

"And IS IT USING THE SAME MICROSWITCH AS DURING STARTING?"

Remember there is a lower limit switch to stop it on disengage, and an upper limit based on tension.

"WHAT DO YOU DO IF THE CLUTCH WARNING LIGHT STAYS ON?"
Pull the circuit breaker to the clutch, come home carefully.

"what about the outer one? is it just a fairing?"

No, when the inner goes faster than the outer, the little teeth engage the outer shaft and make the rotor turn. If the rotor goes faster than the inner shaft (the engine) the teeth are over-run and the rotor can turn even if the engine has seized.

"Is the only reasons for the coning hinges to allow the blades to flap up during coning or they serve any other purpose throughout the flight? Dissimetry of lift and so on?"

They allow the blades to flap up with collective pitch and to flap independently with cyclic application.
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Old 29th Mar 2013, 10:11
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hello

thanks for the prompt reply.
to recap and make sure i have got it right, the outer race of the sprag clutch is mounted on and driven by the engine output, the inner race is built around the inner shaft. where does the outer shaft is mounted on?

kind regards and sorry for the sillyness of he question, i am sure if i had a drawing it will be much easier to grasp.

kind regards

baobab72
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Old 29th Mar 2013, 14:29
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Err no, the pulley which is mounted to the engine has the drive belts on it which in turn drive the upper pulley.

That upper pulley when it starts to spin as the belts tighten -with the clutch ( a linear actuator that tightens the belts by pushing the upper pulley upwards) - drives the sprag clutch at its inner self, which in turn drive the shaft inside it and it goes into the transmission, forward and the tail rotor rearward.

As the sprag is a free wheel in one direction, so, when the engine /lower pulley / upper pulley, stops then the inner shaft just keeps on rotating in the same direction as a free wheel, allowing a nice autorotaion.

The linear actuator has a bearing at each end so the shaft at each end (the inner shaft at the upper end and the engine drive shaft at the lower end) can spin and still keep a preset tension on the actuator for belt tension. The clutch light goes out when it has engaged to a preset tension which is reached by a special spring mechanism.

See quite simple.
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Old 29th Mar 2013, 16:00
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The spray clutch is basically like the sprocket on the back wheel of a bicycle. Think of the chain being a belt to the engine, instead of to the peddles, and the rear wheel, the rotors and tail rotor. On a bicycle, if you stop peddling, the rear wheel will keep spinning with little friction from the fact that the peddles aren't turning. Similarly if the engine on the R22 stops, you want the blades to have no friction from the engine - those blades will slow down quite quickly enough all by themselves ;o)
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Old 29th Mar 2013, 16:34
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pedals

"peddles" means to sell something...
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Old 29th Mar 2013, 17:01
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Excellent point, and well made
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Old 29th Mar 2013, 21:29
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"WHAT DO YOU DO IF THE CLUTCH WARNING LIGHT STAYS ON?"
Pull the circuit breaker to the clutch, come home carefully.
I would suggest to follow the EP as per the POH. If the clutch light remains on for longer than 7-8 seconds in flight, pull the breaker immediately and get back on the ground with the same urgency. Prepare for a drive train failure and subsequent autorotation.

It could be a failure of the motor or circuit (no big drama), but it could also be an impending failure of the belts, or one of the clutch bearings disintegrating (big drama).

Under normal circumstances, the light will not stay on longer than about 4 seconds in flight.

Last edited by lelebebbel; 29th Mar 2013 at 21:31.
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Old 30th Mar 2013, 12:54
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A lot of theories on this, may I suggest this..........

http://www.robinsonheli.com/manuals/.../r22_poh_3.pdf

Horse's mouth and all that.

Last edited by powerlimited; 30th Mar 2013 at 12:54.
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Old 30th Mar 2013, 13:53
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The book clearly states 10 seconds clutch light on in flight, pull Circuit breaker, land as soon as practical, reduce power and land immediate if other indications of a drive failure.

No mention of autorotation
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Old 30th Mar 2013, 16:29
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read on

No mention of autorotation
Right after the part you cited, in parentheses, it says: "be prepared to enter autorotation." Presumably this would be needed if there is a failure of the drive system and loss of RRPM, which would not be unlikely in this situation.

DR
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Old 30th Mar 2013, 17:33
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I would suggest that if this is your first trip/famil in a helo,there is no point in worrying about the clutch...concentrate on the handling ,controls, references,and all the outside world..let the instructor worry about lights,etc..If you enjoy it and follow on,then plenty of time to learn about the `nitty-gritty`...
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Old 31st Mar 2013, 08:39
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Or go and fly in a proper helicopter rather than the 'Crapinson Flimsycopter' - I have crashed in one so I feel qualified to make the statement
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Old 31st Mar 2013, 09:40
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I thought it wouldn't take long.........................................
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