Chinook & other tandem rotors discussions
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Rotorboy,
for the reasons behind VRS in any helicopter I would recommend that you read the excellent thread about the Blackhawk accident which covered it in detail. Nick Lappos has a link to a site that explains it fairly clearly.
To get into VRS you need to be in the parameters for your aircraft with power applied. In a tandem rotor helicopter you can't tilt the discs as you would normally in a single rotor because you will chop the cabin in half. I order to pitch the CH47 forward the pitch is increased on the rear head and decreased on the front head when the stick is pushed forward. This is known as Differential Collective Pitch (DCP) as the blades on each head are pitched collectively but differently between the heads. If you were in the speed and ROD limits for VRS and then pitched forward or backwards it would be possible to get one head into VRS by itself.
In addition to this, the normal recovery technique for single rotor helis is to pitch forward to gain some flying speed. In a tandem this will probably only settle the aft disc further into VRS and you probably won't pitch forward at all. The recommended tandem recovery technique is to pitch sideways which only puts a cyclic input to each head and not a collective one.
for the reasons behind VRS in any helicopter I would recommend that you read the excellent thread about the Blackhawk accident which covered it in detail. Nick Lappos has a link to a site that explains it fairly clearly.
To get into VRS you need to be in the parameters for your aircraft with power applied. In a tandem rotor helicopter you can't tilt the discs as you would normally in a single rotor because you will chop the cabin in half. I order to pitch the CH47 forward the pitch is increased on the rear head and decreased on the front head when the stick is pushed forward. This is known as Differential Collective Pitch (DCP) as the blades on each head are pitched collectively but differently between the heads. If you were in the speed and ROD limits for VRS and then pitched forward or backwards it would be possible to get one head into VRS by itself.
In addition to this, the normal recovery technique for single rotor helis is to pitch forward to gain some flying speed. In a tandem this will probably only settle the aft disc further into VRS and you probably won't pitch forward at all. The recommended tandem recovery technique is to pitch sideways which only puts a cyclic input to each head and not a collective one.
GunsssR4ever
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Chinook info wanted please
Morning all,
Another question please....
We are in the process of upgrading / rebuilding our runway / helicopter area.
Please can anybody advise me what the PCN of a Mauw Chinook is ?
Much appreciated in advance.
Gunsss
Another question please....
We are in the process of upgrading / rebuilding our runway / helicopter area.
Please can anybody advise me what the PCN of a Mauw Chinook is ?
Much appreciated in advance.
Gunsss
Join Date: Mar 2001
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Is this what you are after???
From the RAF Flight Information Handbook:
Chinook HC Mk2:
AUW/MTWA/OWE = 50044lbs - 22700kgs
Tyre Pressure in PSI = 87
Rigid pavement subgrades:
High = 11
Med = 11
Low = 12
Ultra Low = 12
Flexible Pavement subgrades:
High = 8
Med = 10
Low = 12
Ultra Low = 13
Given that they land in fields/car parks I guess you wouldn't need too much LCG.
Cheers
From the RAF Flight Information Handbook:
Chinook HC Mk2:
AUW/MTWA/OWE = 50044lbs - 22700kgs
Tyre Pressure in PSI = 87
Rigid pavement subgrades:
High = 11
Med = 11
Low = 12
Ultra Low = 12
Flexible Pavement subgrades:
High = 8
Med = 10
Low = 12
Ultra Low = 13
Given that they land in fields/car parks I guess you wouldn't need too much LCG.
Cheers
Join Date: Mar 2001
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You are welcome - the only note of caution comes from the fact that I have just realised that MY FIH expired on 22 JUN 99!!
Should be fairly accurate for planning though - can't imagine much as changed a great deal.
Can Winnie have his pics now!?
Alan
Should be fairly accurate for planning though - can't imagine much as changed a great deal.
Can Winnie have his pics now!?
Alan
GunsssR4ever
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Lo ALAN,
Yip - I pressume that is somethng that should remain "within limits". We just realized we might have ANOTHER real B I E G visitor ... Mi-26 ( 56 tons) ...
So back to the drawing board ... you will actually see on a photo I have posted a while ago - the Mi-26's used to operate from our strip (and Chinooks) but now we are extending and the original drawings and engineer - they are not with us any more !
Cheers and if Winnie is Winnie as in Pooh - that is ok but if he / she is anything to do with the Mosquito Mandela ... then NO
Just kiddin ..
Will publish soon ..
Yip - I pressume that is somethng that should remain "within limits". We just realized we might have ANOTHER real B I E G visitor ... Mi-26 ( 56 tons) ...
So back to the drawing board ... you will actually see on a photo I have posted a while ago - the Mi-26's used to operate from our strip (and Chinooks) but now we are extending and the original drawings and engineer - they are not with us any more !
Cheers and if Winnie is Winnie as in Pooh - that is ok but if he / she is anything to do with the Mosquito Mandela ... then NO
Just kiddin ..
Will publish soon ..
GUNSHIP!
Yaya
Nothing to do with the Mandela Family, I am a HE, and Winnie the Pooh is correct!
If you want to know the AUW of the Schweizer 300CB it is 1750 lbs!!
Just missing your impressive pictures of the "Aligator/Crocodil" and wish I was flying some russian heavy iron!
Yaya
Nothing to do with the Mandela Family, I am a HE, and Winnie the Pooh is correct!
If you want to know the AUW of the Schweizer 300CB it is 1750 lbs!!
Just missing your impressive pictures of the "Aligator/Crocodil" and wish I was flying some russian heavy iron!
Join Date: May 2000
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Gunsss, MAUM of a UK CH-47 is 24,500 Kgs. Some cabs can only go to 22.7 but some others can go all the way up to 24.5. Just thought I'd let you know, but I guess it doesn't matter if you're having a 56t visitor!!
Fly safe.
EnnArr.
Fly safe.
EnnArr.
GunsssR4ever
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Lo Winnie - tx for the Schweitzer weight - you never know it might have a higher PCN
EnnAr, many thanks. Although we are battling to find the Mi-26 tyre pressure, I am sure we will have to follow the Mi-26 specs.
Many thanks in any way !
Cheers and best regards,
Gunnss
EnnAr, many thanks. Although we are battling to find the Mi-26 tyre pressure, I am sure we will have to follow the Mi-26 specs.
Many thanks in any way !
Cheers and best regards,
Gunnss
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Hovering Differences in Chinooks
Hello,
I'm a fixed-wing pilot who knows almost nothing about rotary-wing ops, but I've always wondered if twin-tandem (I think that's the correct term) helis such as the Chinook are any easier to hover. It seems that the torque effects of the rotors would cancel each other out and make things much easier for the pilot.
-WN
I'm a fixed-wing pilot who knows almost nothing about rotary-wing ops, but I've always wondered if twin-tandem (I think that's the correct term) helis such as the Chinook are any easier to hover. It seems that the torque effects of the rotors would cancel each other out and make things much easier for the pilot.
-WN
Avoid imitations
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No-one is really sure if they are actually easier but designed to be more difficult, or if they are more difficult but designed to be easier.
They feel quite conventional, though, just bigger.
They feel quite conventional, though, just bigger.
Being a former Chinook pilot....who is now forced by economic necessity to endure mere single rotor devices...I will wholeheartedly confirm real helicopters are easier to hover. We Chinook pilots of years past, certify that is due to the very careful selection process that manned the cockpits (with some small assistance from sheer mass and inertia), Chinooks do hover better.
Avoid imitations
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SASless,
Yep. Some Chinook pilots do have sheer mass and inertia!
Yep. Some Chinook pilots do have sheer mass and inertia!
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The Chinook, and it's smaller brother, the CH-46 are helped immensely by a very capable automatic flight control system that provides attitude hold. Basically, when you have the attitude you want and have trimmed up the cyclic and pedals, the system will hold that until you run out of gas.
But even with the AFCS off, it is still quite easy to hover - helped not only by the lack of torque reaction, but also by the lack of side force and roll changes with tail rotor changes required by power changes.
But even with the AFCS off, it is still quite easy to hover - helped not only by the lack of torque reaction, but also by the lack of side force and roll changes with tail rotor changes required by power changes.
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CH 47 are easy
Its even easier if you have the radalt hold engaged and taking in to account that it will hold heading unless you push the pedals.
Crew Chief bring me another coffee 
Crew Chief bring me another coffee
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One thing Ive wondered is the yaw weird in the chinook. Seems like a big thing to be whipping around with the pedals and I am guessing it yaws around the CG which would prolly be somewhere inbetween the two rotors. Any thing to relate it too or am I talking out of my not so sunny side.
Jcoop....Chinook pilots are used to swinging large things around thus tromping on the footrests is a snap. One interesting fact about the CH-47 is the length of the allowable CG travel....on the order of 144 inches range....just under four meters (metres) for Euro spenders in the crowd.
Shawn...your statements might mean something when describing the C model and later variants. The B model with the square tail fin was somewhat better than the A model with the sharp tail....but the A model without SAS was real sport in Yaw. Felt as though you were pedalling the thing to keep the rotors turning or something. With SAS on...the old A model was rather docile, the B even better, and the C with Pitch SAS and SAS was pretty tame. Add the modern goodies and sooth....what more could a guy ask for...."white with two sugars" maybe.
Shawn...your statements might mean something when describing the C model and later variants. The B model with the square tail fin was somewhat better than the A model with the sharp tail....but the A model without SAS was real sport in Yaw. Felt as though you were pedalling the thing to keep the rotors turning or something. With SAS on...the old A model was rather docile, the B even better, and the C with Pitch SAS and SAS was pretty tame. Add the modern goodies and sooth....what more could a guy ask for...."white with two sugars" maybe.
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So what then is the difference between the Boeing 234 and a CH47, and what model CH47 would the 234 be closest it, if any.
Autorotate.
P.S. I watched them moving a drill rig in the PNG jungles and it was an amazing site to watch with a 260 ft longline.
Autorotate.
P.S. I watched them moving a drill rig in the PNG jungles and it was an amazing site to watch with a 260 ft longline.