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Chinook & other tandem rotors discussions

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Chinook & other tandem rotors discussions

Old 21st Apr 2001, 14:14
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Vfrpilotpb
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Chinook & other tandem rotors discussions

I am asking any of your ex mil Pro's out there, in simple terms how do you fly a Chinook, I am always in awe of these "flying buildings " whenever I see one, but yet I can never detect any cyclic movement to the rear blade's, is it all done at the front set, can you help?
My regards
 
Old 21st Apr 2001, 16:27
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Fr O'Blivien
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Lightbulb

Nothin to do with the green ones mate, this is the story according to the late lamented BV234!

Flying controls operate as any other helo.

Rotor articulation is a bit different.

There is no fore and aft (cyclic) movement in either disk. (there cant be, theyd strike each other) Aircraft pitch is controlled by differential collective between the disks.

Roll is produced by lateral (cyclic) in both disks simultaneously, and yaw by differential lateral cyclic, if you follow my terminology.

Actually there is a slight fore and aft input by a systen called LCT (Longitudinal cyclic trim) that tilts the gearboxes fore and aft to reduce excessive deck angle at speed, but it is not part of the primary flight controls.Conventional flight controls produce these rather unusual inputs via a very complex mechanical mixing unit in the broom cupboard behing the P1.

Due to the dynamics the Chinook develops maximum translational lift in sideways flight to the left, hence the antics of the logging machines plugung sideways on the end of theit long cables - gives them greatly increased lift capacity.

Chinook is extremely docile in handling, yet extremely maneuverable when light. Autorotation is of the thistledown type, rotor inertia is massive and the beggar wont come down fast even if you want it too. Engine off landing is merely a continuous flare to a running landing on the rear wheels which requires quite a lot of runway. I dont know if the military use other techniques.

Take off requires progressive fwd movement on the cyclic as the nose rises to prevent it scuttling off backwards, and vv for landing. There are no torque effects. On icy surfaces it is semi-hover taxiied on the back wheels - groung handling is not helped by rather delicate landing gear, fronts fixed, aft portside castoring and aft stbd only steerable.

What a fabulous toy!

Flying an ILS backwards was fun too (in the sim). Lift off on the landing datum, translate backwards and climb up the slope on instruments. 60Kts sideways and backwards rings a bell??



[This message has been edited by Fr O'Blivien (edited 21 April 2001).]
 
Old 22nd Apr 2001, 12:58
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Vfrpilotpb
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FO'B, thank you for that explanation, I admire all fellow pilots be they pro's or ppls, but to stand and watch one of these double eggbeaters fly and land is something quite different, more than any other craft, I still find it fasinating to watch them fly! my regards
 
Old 22nd Apr 2001, 22:39
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The Nr Fairy
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I had the opportunity last year to spend an hour in a Chinook simulator, with a standards guy in the left hand seat, and another standards guy acting as crewman.

After some initial collective pumping, it felt pretty straightforward to fly - mind you that was probably the AFCS, rather than me !! I got to try some general wazzing, an auto, formation flight and some sling load pickups and drops - one to take the aircraft weight to just under max. All good fun - now, where can I get my hands on the money required to buy that simulator mouldering up in Scotland ?
 
Old 23rd Apr 2001, 00:41
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Shackman
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Cannot bettr Fr O'Blivien for the tech bit, but the mil version flew just the same - actually even more manoeuvrable 'cos it was lighter. Fighter affil in the wocker was awesome, even 2 A10's had difficulty, and power margins impressive. On leaving the fleet to go to Gazelles was told to expect sports car - ugh! Chinook was faster, more fun and could lift more than almost anything else we have in the mil (I don't know about Merlin). It could even fly for ages with the overload tanks on. Odiham - Nimes or 7 hours over the Atlantic (Air India SAR), and the seat was even comfortable.

Yes I miss it - great aircraft, shame about the reputation.


Pertama

 
Old 23rd Apr 2001, 01:52
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PurplePitot
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Wink

Otherwise known as the Boeing Body Bag.... I have only declined a cabbie in two helicopters to date, this one and an Mi8 (Hip)
 
Old 23rd Apr 2001, 11:28
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MightyGem
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Cool

Wimp!
 
Old 23rd Apr 2001, 17:06
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Chinook
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Smile

Went to Chinooks after a joyful few years flying UH-1H with the strap-on offensive bits ..... have to say I love the Huey, but adore the chook ..

She's a joy to fly (as long as one doesn't think too much about the tech), bags of power, can haul a sh**load of coffee home from PNG and is faster than a Blackhawk (much to my brethren's chagrin at times)

Just a pain to pre-flight is all .....

Anyone who wishes to fly the Chinook in Oz ... apply for a job, we need drivers!!!



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Park it, tie it down, lock it, lets go to the pub!!!!!
 
Old 23rd Apr 2001, 18:10
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VLift
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The A models were a hoot. The tail was pointed as apposed to blocked, called them pin tails, also had no stabilizing "strakes" so, if the SAS came off in a turn the aircraft would fight you tooth and nail to swap ends. If the Longitudinal Cyclic Trim (LCT) fails it means the automatic forward tilt of the rotor system, not transmissions, doesn't happen which carries with it an airspeed limit or malfunction procedure depending when they fail. This aircraft was ment to work hard. I too spent many years in UH-1D & H aircraft and the Hook. Two really great aircraft.
 
Old 24th Apr 2001, 01:28
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pedroalpha
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CHINOOK? I love it to bits! I joined the team in 1982 and thoroughly loved my 5 years on the best pilots' machine in the world. I've lifted another CH47, carried 11700 Kg underslung and enjoyed two-wheel taxy games with the best. Its a beast in turbulence; a delight in straight & level (can you do 160 Kts without a dive?) and I hated my family being a passenger in it!!!!!!!!! This machine has attitude.
 
Old 24th Apr 2001, 02:19
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Chinook
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Talking

Sure would enjoy another posting to Hueys after this !!!!

Life is good, even if we do bitch about Timor, Bougainville and Risk Managment [email protected]

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Park it, tie it down, lock it, lets go to the pub!!!!!
 
Old 24th Apr 2001, 17:40
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Thud_and_Blunder
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Chinook,

Heartily concur - had 2.5 years on single Hueys starting in '82, did Chinooks from '89 to '98 and have been enjoying twin Hueys since then. Best of all worlds, eh?

PS I think that while you're Long Looking, there should be a Stn Master at Odiham who thoroughly enjoyed his exchange tour in Oz. Good timing on your part, I reckon. If you go there with the same attitude as the 2 crewmen who came through around 1997 you'll have a whale of a time; they were good ambassadors for all things Antipodean.
 
Old 28th Apr 2001, 14:02
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Arm out the window
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Smile

I've just started reading a book called "Chinook", and according to that it's actually the crewman who flies the aircraft.

Not only that, but apparently the best way to pass your aircrew training course is to do no study, drink Pi55 heavily and steal the exam papers!

I can hardly wait for the next in the series, "Orderly Room Clerk".
 
Old 1st May 2001, 00:09
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Lu Zuckerman
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To: Fr. O’Blivien

You stated:

“There is no fore and aft (cyclic) movement in either disk. (There can’t be, they’d strike each other) Aircraft pitch is controlled by differential collective between the disks”.

You further stated,

“Actually there is a slight fore and aft input by a system called LCT (Longitudinal cyclic trim) that tilts the gearboxes fore and aft to reduce excessive deck angle at speed, but it is not part of the primary flight controls. Conventional flight controls produce these rather unusual inputs via a very complex mechanical mixing unit in the broom cupboard behind the P1”.


Actually, there is a forward cyclic component but it is not introduced by the forward tilting of the gearboxes. An electromechanical actuator that is attached to an arm extension of the swash plates introduces forward cyclic. It does not actuate until the helicopter reaches a forward speed in excess of 60 Knots (approx.). Since the blades intermesh, they can’t contact each other when cyclic is input is made by the automatic system. The pilot does not have direct control of this system and therefore the pilot can’t perform a cyclic flare while flying forward. He can introduce a cyclic flare while flying sideways and because of this, autorotatations must be entered into while flying sideways.


------------------
The Cat

[This message has been edited by Lu Zuckerman (edited 30 April 2001).]
 
Old 1st May 2001, 01:23
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VLift
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Hey Lu

This is humor, right?

"The pilot does not have direct control of this system and therefore the pilot can’t perform a cyclic flare while flying forward. He can introduce a cyclic flare while flying sideways and because of this, autorotatations must be entered into while flying sideways."

 
Old 1st May 2001, 23:19
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Cyclic Hotline
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This is a link to the accident report for C-FHFH, a BV234, which crashed in Canada in 1997.

Just thought it might be of interest to any of you Chinookies.

http://www.tsb.gc.ca/ENG/reports/air.../ea97p0303.htm

 
Old 1st May 2001, 23:51
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heedm
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Thanks for the info on the Chinook crash. I wasn't on the mission but our CH113 (Canadian Forces BV107) was the helicopter on scene for the rescue (wasn't possible).

We were all very interested in why this crashed. Similiar flight control systems in the two helicopters.

For Lu, I assume that the "autorotations must be entered sideways" was a joke. Although fore and aft cyclic works differently than in tail rotor helicopters, it works the same from a practical point of view. Including autorotation.

Matthew.
 
Old 2nd May 2001, 01:27
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Lu Zuckerman
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To: heedm

The pilot of a CH-47 has absolutely no fore and aft cyclic input. As I had indicated previously the cyclic is input automatically when the aircraft reaches approximately 60 Knots.** The pilot has no part in it. The cyclic that is input is forward cyclic and this forward cyclic will be removed when the aircraft reaches a speed below 60 Knots. In a conventional helicopter the pilot can pull the cyclic back to flare to arrest his speed and at the same time increase rotor speed. This can’t be done on a CH-47 if you enter an autorotation going forward. Cyclic input can only be made when the aircraft is flying sideways and the reason for that is the pilot introduced left or right cyclic.

**On the CH-47 the highest contributor to maintenance action and overhaul cost are the two rotorheads. Because the rotorheads are mainly in full collective in a hover and a reduced collective on the Fwd. Rotor and an increased collective on the rear rotor when flying forward the rotor heads are 90% scrapped during overhaul due to the high stress levels. Boeing is developing a new elastomeric rotorhead and I will guarantee you that it won’t last as long as the rotor system it replaces


------------------
The Cat
 
Old 2nd May 2001, 02:36
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Chinook
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Lu,

Tell me again how I can't reduce speed or increase RRPM autorotating a CH-47D going forward?

 
Old 2nd May 2001, 03:39
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Arm out the window
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Sounds like just semantics to me.

I stand to be corrected, but I think Lu's saying that cyclic pitch changes can't be made on the rotors in the fore and aft sense, and therefore it would technically be wrong to say that pitch controlling is done 'cyclically'.

However, in any helicopter I'd call that stick between my legs (now, now) the cyclic, and I'd be extremely surprised if a Chinook pilot can't pull back on that and make the aircraft flare, in autorotation or not.

If you can pull the nose up, you can change the relative airflow into the disc and therefore get flare effect.

Right or wrong?
 

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