Chinook & other tandem rotors discussions
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Chinook Flight Mixer linkages.
I now understand more thanx.
I am 50-ish and have been befuzzled since I started flying at 16. How does the mixer-linkages work in the control system. I dont want to hear how the concept works again? I want a schematic if linkages.
Why doesnt something brek when you apply left cycli and right rudder?
Help me. I wont die before I know and I dont want to live forever!
I am 50-ish and have been befuzzled since I started flying at 16. How does the mixer-linkages work in the control system. I dont want to hear how the concept works again? I want a schematic if linkages.
Why doesnt something brek when you apply left cycli and right rudder?
Help me. I wont die before I know and I dont want to live forever!
The video of the Chinook experiencing ground resonance was taken of a ground run test of the aircraft at the Aberdeen Proving Grounds. The aircraft was there to be shot at by various weapons to determine what resistance it had to various size rounds and when hit in various sensitive places.
Unfortunately, the aircraft was chained tightly to the hardstand and during the remote run test the aircraft was unable to move naturally and encountered ground resonance which led to the aircraft shucking the aft rotor, gearbox, and vertical fin area.
Chalk up another success to the Army!
Unfortunately, the aircraft was chained tightly to the hardstand and during the remote run test the aircraft was unable to move naturally and encountered ground resonance which led to the aircraft shucking the aft rotor, gearbox, and vertical fin area.
Chalk up another success to the Army!
CheekyChopper,
Download the following pdf file:
http://chinook-helicopter.com/Public...-240-23P-3.pdf
and go to Page 126 of 511 (or Figure 392 (Sheet 1 of 5))
for a picture of what the Chinny Mixing Unit looks like.
If you can pick out the lower assembly (to the Left of the words "Detail A") that is what a 'normal' Mixing Unit may look like!
If you can find manuals for a Whirlwind (S-55) or Wessex (S-58) they have really simple examples.
Download the following pdf file:
http://chinook-helicopter.com/Public...-240-23P-3.pdf
and go to Page 126 of 511 (or Figure 392 (Sheet 1 of 5))
for a picture of what the Chinny Mixing Unit looks like.
If you can pick out the lower assembly (to the Left of the words "Detail A") that is what a 'normal' Mixing Unit may look like!
If you can find manuals for a Whirlwind (S-55) or Wessex (S-58) they have really simple examples.
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Chinook rear gear.......
..what happens if one of the rear undercarriage units still show in contact with the ground after lift off........????.......do you have to touch down again to sort it out......???????.....
.....what happens if the indication occurs during flight.........????....
regards Robin......
.....what happens if the indication occurs during flight.........????....
regards Robin......
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tandem question/help
I am working on a project of a 10% scale model of a tandem gyroplane and I'm looking for a little help from the experts here on this thread.
This project has been on my bucket list for nearly twenty years and now that I'm retired I have the time to work on it but lack some tandem expertise. I hope some of you can help.
Today's problem is the use of gimbal heads and can DCP be acheived by making the front and aft rotors work opposite to each other...pitch up on the front and down on the aft rotor ect?
This project has been on my bucket list for nearly twenty years and now that I'm retired I have the time to work on it but lack some tandem expertise. I hope some of you can help.
Today's problem is the use of gimbal heads and can DCP be acheived by making the front and aft rotors work opposite to each other...pitch up on the front and down on the aft rotor ect?
DCP should work as you describe.....for pitch control. In order to level the fuselage in flight for better aerodynamics gets much more complicated. Read up on "Speed Trim" on the Chinook series....and you will understand why that is so.
Search for photos of the "SAS Closet" (left side of the companionway leading to the Cockpit) to get an idea of how complicated the bell crank system is for the flight controls.
I wish you ever success.....as when you get it worked out you shall be a genius on your own right!
Search for photos of the "SAS Closet" (left side of the companionway leading to the Cockpit) to get an idea of how complicated the bell crank system is for the flight controls.
I wish you ever success.....as when you get it worked out you shall be a genius on your own right!
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Thanks SASless,
I have three flights under my belt so far. All three ended in an an abrupt loop crashing nose first. The aft rotor appears to not to be generating enough lift or the AOA of the aft rotor is too shallow. Maybe the differiential movement is too much for a good take off. Who knows? I guess I'll find out soon enough!
PS I'm using a 1/1 unit ratio for my DCP changes between my rotors...is this too much?
I have three flights under my belt so far. All three ended in an an abrupt loop crashing nose first. The aft rotor appears to not to be generating enough lift or the AOA of the aft rotor is too shallow. Maybe the differiential movement is too much for a good take off. Who knows? I guess I'll find out soon enough!
PS I'm using a 1/1 unit ratio for my DCP changes between my rotors...is this too much?
What is the CG of the aircraft? Perhaps there is an issue there that might affect the necessary lift from each head.....which might change that ratio.
I am purely guessing on this.....but it would seem "airspeed" would have to be a function of pitch angle of the airframe as you have no way to level the fuselage by using speed trims.
Would reducing the sensitivity of the collective inputs make the aircraft less sensitive and perhaps more stable?
I bet it is a thrill trying to work all this out!
There was a really sharp guy that built a Huey helicopter complete with turbine engine that did some flights where Huey 509 was based several years.
I will send you a PM on a way to get in touch with him.....hopefully.
I am purely guessing on this.....but it would seem "airspeed" would have to be a function of pitch angle of the airframe as you have no way to level the fuselage by using speed trims.
Would reducing the sensitivity of the collective inputs make the aircraft less sensitive and perhaps more stable?
I bet it is a thrill trying to work all this out!
There was a really sharp guy that built a Huey helicopter complete with turbine engine that did some flights where Huey 509 was based several years.
I will send you a PM on a way to get in touch with him.....hopefully.
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SASless,
The first flight was with the CG located at the 25% station and was moved forward 5% after each attempt. The longitudinal rotation did slow somewhat with each change. Now, I'm looking at the DCP ratio. Maybe, the aft rotor need to move more than the front due to flying in the wash of the front rotor. A ratio change, as you suggested, to say 1/2 might be in order here...it's easy enough to do with a change in the linkage position on the aft bell crank.
Yes, It's great fun doing this. My grandkids love to help on Sundays, after church, by being my "ground crew". They each have a job doing camera work and picking up the pieces, lol. The most enjoyable part is the experimentation. I have made blades with BERPs and even servo flaps...Kaman style. Now, I'm playing with blade twist but it seems to be above my skill set, for the moment.
I will certainly give the Huey fellow a shout. I love to talk "helicopter" with anyone!
joe
The first flight was with the CG located at the 25% station and was moved forward 5% after each attempt. The longitudinal rotation did slow somewhat with each change. Now, I'm looking at the DCP ratio. Maybe, the aft rotor need to move more than the front due to flying in the wash of the front rotor. A ratio change, as you suggested, to say 1/2 might be in order here...it's easy enough to do with a change in the linkage position on the aft bell crank.
Yes, It's great fun doing this. My grandkids love to help on Sundays, after church, by being my "ground crew". They each have a job doing camera work and picking up the pieces, lol. The most enjoyable part is the experimentation. I have made blades with BERPs and even servo flaps...Kaman style. Now, I'm playing with blade twist but it seems to be above my skill set, for the moment.
I will certainly give the Huey fellow a shout. I love to talk "helicopter" with anyone!
joe
On the Chinook the CG limit spread is a staggering 144 inches (as I recall anyway....) which is very forgiving as compared to a Single Rotor helicopter.
Enjoy the time with the young un's.....must be good fun as they laugh when the pieces fly! I reckon that can turn into a real scavenger hunt at times.
Enjoy the time with the young un's.....must be good fun as they laugh when the pieces fly! I reckon that can turn into a real scavenger hunt at times.
Chinook CG Range
SAS, maybe the BV marketing troops thought it was 144 inches.
People evaluating the CH-47 vs the CH-53 ( thinking UK, Israel and Germany ) always got a surprise when they found out that the CG ranges were almost identical. I know the 53A/D went from 328" to 352" and I just looked up the CH-47D on an Army wt and balance presentation and at 42,000 lbs, their CG range went from 316" to 338". Pretty close.
Thanks,
John Dixson
People evaluating the CH-47 vs the CH-53 ( thinking UK, Israel and Germany ) always got a surprise when they found out that the CG ranges were almost identical. I know the 53A/D went from 328" to 352" and I just looked up the CH-47D on an Army wt and balance presentation and at 42,000 lbs, their CG range went from 316" to 338". Pretty close.
Thanks,
John Dixson
Might it be the rotor head angles?
Most tandem rotors are biased away from each other by approx ten degrees.
Don't forget that Chinook swashplates (LCT's?) change each Rotor Head's path/angles relative to forward flight speeds.
Most tandem rotors are biased away from each other by approx ten degrees.
Don't forget that Chinook swashplates (LCT's?) change each Rotor Head's path/angles relative to forward flight speeds.
John,
I stand corrected....too many Pints of the foaming Ale I presume!
I found a CG chart for the A Model Wokka.....which shows a 48 inch travel at 27,500 Pounds MAUW and 23" at 33,000 Pounds.
I know you can set a full pallet (about 4,000 pounds) of Cememt Mix on the Ramp....sling a huge Yellow Concrete Mixer bearing Blue Air Force markings and still have sufficient cyclic control. As haste was of the essence....and it being Midnight at Bien Hoa AFB....there was not a lot of planning involved.
Having a Cargo Winch, Ramp with extensions, and a Cargo Hook made Midnight Requistioning great fun....with virtually unlimited possiblilities. Having the ability to carry an M-151 Jeep with FM Radio for scouting and coordination opened up places not usually accessible.
The trick was to get the Yellow covered up with Olive Drab and place Black US Army numbers all over the Mixer.....and dryed before OSI, CID, or the MP's made it to our unit area!
I stand corrected....too many Pints of the foaming Ale I presume!
I found a CG chart for the A Model Wokka.....which shows a 48 inch travel at 27,500 Pounds MAUW and 23" at 33,000 Pounds.
I know you can set a full pallet (about 4,000 pounds) of Cememt Mix on the Ramp....sling a huge Yellow Concrete Mixer bearing Blue Air Force markings and still have sufficient cyclic control. As haste was of the essence....and it being Midnight at Bien Hoa AFB....there was not a lot of planning involved.
Having a Cargo Winch, Ramp with extensions, and a Cargo Hook made Midnight Requistioning great fun....with virtually unlimited possiblilities. Having the ability to carry an M-151 Jeep with FM Radio for scouting and coordination opened up places not usually accessible.
The trick was to get the Yellow covered up with Olive Drab and place Black US Army numbers all over the Mixer.....and dryed before OSI, CID, or the MP's made it to our unit area!
CH-47 " Other " Missions
SAS, should I have written: " sorties "? BTW, you are entirely correct about the local license applied to that subject.
Flying in a unit ( 119th Avn Co ) that had UH-1B guns and slicks in 65-66, not only didn't we have the performance to steal anything of use, but stationed at Camp Holloway we didn't have anyone nearby who had anything worth taking anyway.
Prior to that however I was at the Army Test Board ( as a 2nd Lt out of flight school ) and our three CH-47A's were having problems with resonant, self-destructing nose gearboxes that shed pieces thereof into the T-55 immediately aft, resulting in landings at the golf course and other places that got attention. Anyway, the older heads tended to avoid getting on the CH-47 schedule, so within two months or so I was an IP, which made me available ( read as " expendable " ) for an interesting mission.( Boeing changed the operating Nr from 204 to 230 which avoided the resonance ).
They wanted to know how vulnerable the UH-1 was to the sort of ground fire expected in RVN, so a full scale wooden UH-1 was built with a double metallic foil skin in 30-40 sections, each attached to an electrical feed to a tape recorder. Proposition: sling this model at the end of a 2000 ft long cable at night and shoot live ammo at it as we flew various courses and altitudes under radar control at FT Bliss. If a bullet pierced the skins, electrical contact would be recorded for that skin section on the recorder. Good job for a 2nd Looey.
To pick up and return the model without banging it around, we had a very powerful AA WWII searchlight whose beam was aimed skyward at the vertical. So after they had run out of the prescribed amount of ammo, one would come back to a hover at 2000 plus 3-500 ft and listen to another crewmember talk us down the beam to a gentle touchdown.
Did this for about a month until we got some new gunners on the ground and the cable got parted 200 ft from the CH-47. At the time, they had increased the ground fire caliber to 40mm ( no typo ) so the test was declared over.
Always thought the CH-47A, now I'm talking about 1963-5, was easy to fly, and actually the Army and Boeing managed that program pretty well over the years.
Thanks,
John Dixson
Flying in a unit ( 119th Avn Co ) that had UH-1B guns and slicks in 65-66, not only didn't we have the performance to steal anything of use, but stationed at Camp Holloway we didn't have anyone nearby who had anything worth taking anyway.
Prior to that however I was at the Army Test Board ( as a 2nd Lt out of flight school ) and our three CH-47A's were having problems with resonant, self-destructing nose gearboxes that shed pieces thereof into the T-55 immediately aft, resulting in landings at the golf course and other places that got attention. Anyway, the older heads tended to avoid getting on the CH-47 schedule, so within two months or so I was an IP, which made me available ( read as " expendable " ) for an interesting mission.( Boeing changed the operating Nr from 204 to 230 which avoided the resonance ).
They wanted to know how vulnerable the UH-1 was to the sort of ground fire expected in RVN, so a full scale wooden UH-1 was built with a double metallic foil skin in 30-40 sections, each attached to an electrical feed to a tape recorder. Proposition: sling this model at the end of a 2000 ft long cable at night and shoot live ammo at it as we flew various courses and altitudes under radar control at FT Bliss. If a bullet pierced the skins, electrical contact would be recorded for that skin section on the recorder. Good job for a 2nd Looey.
To pick up and return the model without banging it around, we had a very powerful AA WWII searchlight whose beam was aimed skyward at the vertical. So after they had run out of the prescribed amount of ammo, one would come back to a hover at 2000 plus 3-500 ft and listen to another crewmember talk us down the beam to a gentle touchdown.
Did this for about a month until we got some new gunners on the ground and the cable got parted 200 ft from the CH-47. At the time, they had increased the ground fire caliber to 40mm ( no typo ) so the test was declared over.
Always thought the CH-47A, now I'm talking about 1963-5, was easy to fly, and actually the Army and Boeing managed that program pretty well over the years.
Thanks,
John Dixson
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In accordance with the original thread title, here is something other than you Chinook. 22000 lbs A.U.W., no Auto. Stab., no rotor speed governing, and manual throttles. Pilot was F.O. Nast, who wanted to see if the beast was good for roping.
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What happens when "Tandems go bad"!
Navy H-46 (BV107). I was flying over mixed land and water about dusk at 1300 ft when the DCPT actuator in the control closet came disconnected due to a cotter pin not installed in prior maintenance about 10 flight hours before. A/C did a high G uncommanded loop and blades meshed at about 1800 ft upside down at the top of the loop. Broke into 3 sections. Very violent. On the way down I was hit in the head (concussion) by the overhead circuit panel coming loose and knocking me into the cyclic (besides having both lower legs broken by the bottom of the instrument panel) was unconscious when we hit the water and woke up about 20 feet down. Egressed and bobbed up next to the copilot (broken back) who thought I had died (had his footprint on my kneeboard where he stepped on me leaving - still friends!). Unfortunately the 3 crewmembers in the back perished. Lots more to the story - buy me a beer sometime if you want to hear the rest.
Still - with 2000 hours or so in them, it's the best helo I've ever flown for power and all around fun. Nothing like doing a head on approach to an underway ship with an external load and doing a button hook, rotating around the nose as you came abeam in a 180 turn and ending up placing the load right on the deck as you swung through.. Although, for a long time, I got a bad feeling in my stomach when the co-pilot would pull back on the cyclic quickly without saying something.
Mike
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Still - with 2000 hours or so in them, it's the best helo I've ever flown for power and all around fun. Nothing like doing a head on approach to an underway ship with an external load and doing a button hook, rotating around the nose as you came abeam in a 180 turn and ending up placing the load right on the deck as you swung through.. Although, for a long time, I got a bad feeling in my stomach when the co-pilot would pull back on the cyclic quickly without saying something.
Mike
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Mike,
I defy anyone to top that story.....you are one very very lucky fellow!
Perhaps we need to start a "There I was....." thread telling of our very lucky escapes from bad situations!
There are some corkers to be told.....and as yours....all true!
By the way.....you got a lucky Lotto number you wish to share?
I defy anyone to top that story.....you are one very very lucky fellow!
Perhaps we need to start a "There I was....." thread telling of our very lucky escapes from bad situations!
There are some corkers to be told.....and as yours....all true!
By the way.....you got a lucky Lotto number you wish to share?
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Amazing what a small world this is. I was with a friend at the Intrepid Museum on Saturday, and there was a Piasecki H-25 Retriever.
Thought this was a coincidence in name though didn't think anything of it again, until I met with a friend/colleague this week, and it turns out that was his father!
Reading his obituary it turns out he was also the first helicopter pilot to get an helicopter license without having a fixed wing license.
An interesting man indeed.
Thought this was a coincidence in name though didn't think anything of it again, until I met with a friend/colleague this week, and it turns out that was his father!
Reading his obituary it turns out he was also the first helicopter pilot to get an helicopter license without having a fixed wing license.
An interesting man indeed.
RAF Belvedere