Question from a mere spotter

[NWSRG]

Folks,

This is very much an enthusiasts question, so forgive my ignorance...

Is a tandem rotor (like a Chinook) easier to fly than a more conventional helicopter? My simple mind assumes that the two rotors must effectively cancel the torque rotation tendency, but I'm also telling myself it can't be that simple.

Just curious, so any views from the professionals would be appreciated!

[Ascend Charlie]

If there was no SAS and autopilot, a Chinook would want to roll on its side and proceed sideways like a twin-engined aeroplane.

Fancy electrickery makes it behave. And it is not easy to fly any helicopter, so all helicopter pilots are steely-eyed, fabulous bodies, and get all the chicks.

[jonkster]

modest as well :)

[Hughes500]

but too
true

[Fareastdriver]

My simple mind assumes that the two rotors must effectively cancel the torque rotation tendency, but I'm also telling myself it can't be that simple.

It is that simple. Unfortunately there is a tendency for the rear rotor to try and catch up with the front rotor so to make it easy for today's spoilt brats called pilots they have electronic stabilisation.

In days of yore the pilot had to sort it out by himself.

[Bell_ringer]

In days of yore the pilot had to sort it out by himself.

..while keeping the fire stoked and the steam at the correct pressure. :E

[Ascend Charlie]

Two pilots, one for the front rotor and one for the back. Remember the blades have to give way to the left.

[Georg1na]

Only in France..................

[Two's in]

Just on the off chance the OP wanted a slightly more serious answer, other than the normal differences of aircraft types, a Chinook cockpit looks just like any other twin-engine helicopter cockpit. The lever on the left adjusts the size of the houses, stick in the middle makes you go in the direction you point it, and the pedals on the floor let you decide if you want to see where you are going or not. Some very clever mechanical control mixing handles the basics of the controls operating as per a standard helicopter, then you start to add auto stability and autopilot functions to make it really clever. You need to look at the V-22 Osprey controls to see how some very smart software handles the transition from hover to forward flight, as is the case with the F-35B, but the idea is to make it as close to standard control layout as possible.

[ShyTorque]

The pilot of a Chinook thinks he’s flying a smooth helicopter. In fact he’s strapped onto a concrete block, which is connected to the airframe by springs and tends to continue in a nice straight line, while the airframe bounces around all over the place behind him.

[NWSRG]

If there was no SAS and autopilot, a Chinook would want to roll on its side and proceed sideways like a twin-engined aeroplane.

Fancy electrickery makes it behave. And it is not easy to fly any helicopter, so all helicopter pilots are steely-eyed, fabulous bodies, and get all the chicks.

I liked this answer! :-)

But why the tendency to roll?

[NWSRG]

Just on the off chance the OP wanted a slightly more serious answer, other than the normal differences of aircraft types, a Chinook cockpit looks just like any other twin-engine helicopter cockpit. The lever on the left adjusts the size of the houses, stick in the middle makes you go in the direction you point it, and the pedals on the floor let you decide if you want to see where you are going or not. Some very clever mechanical control mixing handles the basics of the controls operating as per a standard helicopter, then you start to add auto stability and autopilot functions to make it really clever. You need to look at the V-22 Osprey controls to see how some very smart software handles the transition from hover to forward flight, as is the case with the F-35B, but the idea is to make it as close to standard control layout as possible.

...and this one too...thanks to all for your insights!

[meleagertoo]

At least a conventional helo has some longitudinal stability in the cruise due to the weathercocking effect of surfaces on the tailboom. The Chinook of course has no such luxury, the nose only points in any given direction in any flight regime because mechanical forces entice it to. This can come as something of a surprise to the pilot who is expecting it to want to point in the direction of travel....

What seriously impressed me upon graduating to SAS off flight was the machine's ability, even propensity to fly pointing in any direction at all regardless of direction of travel with equal happiness. Thus it would quite readily try to swap ends on an ILS or decide to thrunge along sideways if you let it - it simply didn't seem to mind! Not that the results of allowing it to do so were to be reccomended. Limitations, though very generous by conventional helo staandards could easily be eceeded.

A favourite sim game was transition into the hover on the touchdown markings and fly a departure tracking up the ILS in rearwards flight at 60Kts, stabilise to the hover at 1500ft and return down the ILS pointing (!) forwards.
It was possible....

[jimf671]

I am so glad the OP appears to have realised that you guys are all bonkers.

[tartare]

That is actually very interesting.
I didn't realise that if it weren't for the SAS, you steely eyed cyclic wranglers would have trouble getting a Wokka to point forwards.
Son has an Army chopper driver Officer Selection Board coming up soon.
Have told him that if he gets it - there's only one machine to fly - and it ain't got a conventional tail rotor!
Not that the green machine will let him decide - one ends up flying what one is told I gather.

[Bravo73]

If he wants to fly a Chinook in the UK, he’ll have to join the RAF, not the Army.

[John Eacott]

A favourite sim game was transition into the hover on the touchdown markings and fly a departure tracking up the ILS in rearwards flight at 60Kts, stabilise to the hover at 1500ft and return down the ILS pointing (!) forwards.
It was possible....

Sim game? We would back up the GCA at Culdrose just to see how long it would take the controller to realise what was wrong with his screen :p

[a5in_the_sim]

Helicopters fly because they are ugly and the earth repels them.

[Sloppy Link]

It has to be better to stop and then land opposed the other way round.

[T18]

Two’s In, I like the you’re explanation.

Do you instruct? As a plank driver, with you instructing, I’m sure I could learn fairly quickly!

Simples - T18

[Georg1na]

"Helicopters fly because they are ugly and the earth repels them."

They don't look so ugly when they save your life......................:E

[John Eacott]

Standard response to ragging from the paraffin pigeon drivers in the carrier Wardroom: "You all look the same on the end of the winch wire" :p

[Bell_ringer]

"Helicopters fly because they are ugly and the earth repels them."

They don't look so ugly when they save your life......................:E

Remember that these comments come from people that think cessna’s are sexy, that is like taking fashion advice from someone who likes tweed.

[tartare]

If he wants to fly a Chinook in the UK, he’ll have to join the RAF, not the Army.

But he's not in the UK, cobber.
They do things differently down here...

[MightyGem]

Surprised SASLess hasn't chipped in here.

[212man]

Surprised SASLess hasn't chipped in here.
too busy on FB! ;-)

[DOUBLE BOGEY]

Definition of a helicopter; A million parts, revolving around an oil, leak waiting for metal fatigue to set in

[PDR1]

Never fly in any air vehicle which has the impertinence to defy the natural laws by refusing to stall when flown too slowly. Unless corrected such impertinence leads to hubris, allowing the air vehicle to believe it is the one in command.

The only air vehicle permitted to defy the natural law in this way is Gods Own aircraft, the Harrier.

PDR

[[email protected]]

And what did the harrier pilots have to learn to hover in - oh yes, a helicopter:)

[Bell_ringer]

And what did the harrier pilots have to learn to hover in - oh yes, a helicopter:)

Aah harriers. View at a museum near you.

[LRP]

I've never flown the Chinook but know many that have. Based on that experience it must be relatively easy to fly. ;)

[Fareastdriver]

Take away the gizmos and it is not so easy. One way of preventing the rear rotor from catching up with the front is to differentiate the collective and cyclics. Basically if the rear rotor isn't leaning as far forward as the front it wont catch up. This means it hasn't the same vertical component so it needs more pitch. I believe that on the early Piaseckis or Vertols there was a spirit level in the cockpit to assist you to level it with differential collective.

The problem with twin rotors is the transmission. Apart from the Belvedere one or more of the gearboxs was dependent on a shaft to drive it. This breaks and you have a fatal disymmetry of lift. Luckily AFIK this hasn't happened yet.

The Belvedere had an engine under each rotor and a synchronisation shaft keeping the blades apart. This has broken twice in service. In both cases the pilots flew the aircraft so the rear rotor, turning at a different speed than the front, was stepped above the front until they landed.

The shutdown was quite noisy.

[nomorehelosforme]

Remember that these comments come from people that think cessna’s are sexy, that is like taking fashion advice from someone who likes tweed.

Agree with the Cessna comment... but the Tweed comment, You clearly haven’t been to the races at Royal Ascot, racing at Goodwood, Henley Royal Regatta or Polo at Windsor Great Park... Tweed is quite the fashion and receives many compliments when worn, Is there no Tweed at The Durban?

[NRU74]

but the Tweed comment, You clearly haven’t been to the races at Royal Ascot,

Wasn’t it Edward VII at Ascot, when he saw Lord Harris in tweed instead of a morning suit, who remarked ‘Mornin’ Harris, going ratting ‘?

[nomorehelosforme]

Wasn’t it Edward VII at Ascot, when he saw Lord Harris in tweed instead of a morning suit, who remarked ‘Mornin’ Harris, going ratting ‘?

Quite possibly true! I wonder how many people outside of the UK understand the meaning of “ratting” with ferrets or terriers

[Bell_ringer]

..You clearly haven’t been to the races at Royal Ascot, racing at Goodwood, Henley Royal Regatta or Polo at Windsor Great Park...

Actually, I have been a guest at all of these c/o the significant other and her fondness for all things four-legged. Henley was a welcome break from eau de horse.
They provide some fantastic insight into the British psyche (and frequent lack of dentistry) :}
But we wafting away from the topic.

If we had a pound for every time we heard the one about the oil leak or the earth repelling, we would all be quite wealthy.
My personal favourite is still:
How do you tell the difference between God and a helicopter pilot?
God doesn't tell you he's a helicopter pilot..

[Ascend Charlie]

How do you tell the difference between God and a helicopter pilot?

God can't fly helicopters.

[[email protected]]

And we worship at the Church of Translational Lift:)

[ShyTorque]

Aah harriers. View at a museum near you.

I always said they’d never catch on.

[ShyTorque]

The problem with twin rotors is the transmission. Apart from the Belvedere one or more of the gearboxs was dependent on a shaft to drive it. This breaks and you have a fatal disymmetry of lift. Luckily AFIK this hasn't happened yet.

The problem here is that two helicopters are being forced to fly in close formation with each other. They are so ugly that they repel each other, so sometimes the shaft breaks.

The shaft certainly has broken on an RAF Chinook, at Odiham. Thankfully the aircraft was in the low hover and the occupants escaped intact. Mind you, everything else broke, too. The pilot told me that after it fell to the ground like a railway carriage, he naturally reached up to shut the engines down and the engine controls had departed, along with the cockpit roof, which was also missing.

[The Nr Fairy]

The problem here is that two helicopters are being forced to fly in close formation with each other. They are so ugly that they repel each other, so sometimes the shaft breaks.

The shaft certainly has broken on an RAF Chinook, at Odiham. Thankfully the aircraft was in the low hover and the occupants escaped intact. Mind you, everything else broke, too. The pilot told me that after it fell to the ground like a railway carriage, he naturally reached up to shut the engines down and the engine controls had departed, along with the cockpit roof, which was also missing.

Less happily, a fatal to a British Airways Chinook in 1986 - https://en.wikipedia.org/wiki/1986_British_International_Helicopters_Chinook_crash, and the report available at https://www.gov.uk/aaib-reports/2-1988-boeing-vertol-bv-234-lr-g-bwfc-6-november-1986

And to a US Army Chinook in Germany too in 1982 - http://www.chinook-helicopter.com/history/aircraft/C_Models/74-22292/74-22292.html

[nowherespecial]

Also worth remembering that most things are easy to do in aviation when your power margin is as big as the Chinook.... Spectacular aircraft to fly, fully laden but mind blowing to fly when empty of pax and kit.

[Thud_and_Blunder]

It's the only helicopter I've operated with a max rate of climb limit (3000fpm, ISTR), apparently due to a 3-axis shuffle which developed during test-flying when that RoC was exceeded. As the aerodynamicists were unable to provide an explanation, a limitation was imposed.

As for the aircraft at Odiham decoupling on lifting to the hover (remember it well, it was on the first day of Chinook groundschool for my course) - at least the Chinook had fuel disconnect switches available in the cabin (as operated by the good Sqn Ldr as he departed the airframe). I believe that a CH53/ Sikorsky S65 variant that suffered a heavy landing which caused the disc to droop so far as to turn the cockpit into a cabriolet had no such feature, which meant that the aircraft had to be left turning and burning until the fuel supply was exhausted.

[Fareastdriver]

I didn't know about the Odiham Chinook probably because it wasn't fatal.

Mannheim was a result of the forward pinion bearing seizing which led to the transmission failing. Rumour has it that Elfinsafety stopped the overhaul team used 'dangerous' 3,000 p.s.i. to clear the oilways of the walnut grit used to clean them. Lower pressure didn't work as well so it eventually blocked it.

The Sumburgh on was where a solid gear was replaced with a lined one that could be overhauled more cheaply. Unfortunately it wasn't trialled over the North Sea so salt laden air got in and corroded the joint leading to a failure of the forward gearbox.

You can make helicopters 100% safe but then you get slammed by a bus on the way to work.

[212man]

As for the aircraft at Odiham decoupling on lifting to the hover (remember it well, it was on the first day of Chinook groundschool for my course) - at least the Chinook had fuel disconnect switches available in the cabin (as operated by the good Sqn Ldr as he departed the airframe). I believe that a CH53/ Sikorsky S65 variant that suffered a heavy landing which caused the disc to droop so far as to turn the cockpit into a cabriolet had no such feature, which meant that the aircraft had to be left turning and burning until the fuel supply was exhausted.

That was an S61 on a vessel in the East Shetland Basin - I think the tail wheel slipped off the deck (or they missed it) and the instinctive forward cyclic took the roof off. The pax and co-pilot stayed on the vessel and captain went and sat on the water until the fuel ran out. There are photos online of it (but can't find them)

[Gordy]

It's the only helicopter I've operated with a max rate of climb limit

The Bell 407 has a max rate of climb of 2,000 fpm.

[Ray_Y]

I would like to thank for this nice discussion.

Very nice Chinook background and hilarious content