Printer-friendly version of this topic Bookmark this topic (Registered users only)		Previous Topic | Next Topic
VPC Forums FSFORUM
Original message

BDEchols Certificates/Ratings/Crew Stations: "Tandem Rotor Helicopters" 06-30-02, 05:15z  This started as an e-mail to answer a question from a new member of Flight Adventures. Perhaps it might be of interest to others. I submit it below: Just checked out the Canadian Labrador. It is a CH46 tandem rotor turbine helicopter which is still being used by the US Marines. They call it the Sea Knight. A brief spot of history. Shortly after our Korean adventure Bell Helicopter started working on the Huey utility helicopter. At roughly the same time Boeing-Vertol started working on a heavy lift helicopter using the tandem rotor concept. The result from Boeing was two models. One, slightly smaller, and adapted for carrier use with folding rotors was the Sea Knight. It is still in use by the US marines and still plays a significant role. This is the model Canada refers to as the Labrador. Another model, larger and heavier was developed as the CH47 Chinook and used by the US Army. Both entered service in the early 60's. Both are in heavy use today. Both served in Vietnam, Desert Storm, and Afghanistan. Neither are antiquated machines. Both models have been updated with new engines, airframe enhancements and improved avionics and glass cockpits. Boeing is still producing new models of the CH47 Chinook, as well as refurbishing older models to new capabilities. For the foreseeable future tandem rotor helicopters will have a significant role. Let me explain why. All of the power produced in tandem rotors translates into lift. In conventional helicopters, the tail rotor is used to counter-act the torque of the rotating wings. Although small, maybe 10 to 20 percent of power available is used to control torque. This energy contributes nothing to lift or speed. This waste of energy translates into decreased useful load. That is why Boeing can brag of their lift to weight ratio. This efficient use of available power does not come without problems. Stability is severely compromised. All tandem rotors do not like to fly straight. The rear rotor is constantly trying to swap ends with the front rotor. Not a happy thing to happen. This was overcome by gyro stabilization called "Stability Augmentation System." This system, called SAS is critical to operation of a twin rotor. Gyros feed input into the control system to maintain stability. Part of my training was to try to fly the beast with SAS off. Only at slow speeds and small loads would this be possible. That is why even the earliest Chinooks had dual SAS systems. If one SAS was acting flaky it was possible to switch to the other. If both failed in a critical flight regime recovery would be doubtful. Complete failure of SAS never happened to me, or anyone else that I know of. Another curious fact of these tandem rotor beasts is that they are inherently faster than single rotor craft. I can already hear the cries. No way these tubs were faster than a Cobra! Allow me to explain why. Every single rotor craft is limited in speed because of a physical property called "retreating blade stall." At some point, every single rotor craft is flying through the air fast enough so that the retreating blade can not keep in advance of the relative wind to produce lift on the retreating blade side. Hence a stall and roll. Tandem rotors are counter-rotating, hence as the retreating blades on one rotor lose efficiency, the other rotor is increasing efficiency on the other side to balance the effect. Granted a torque effect on the fuselage structure is induced, but popping a few rivets was a small price to pay to outrun the Cobra! To clear up one other common misconception each rotor was not turned by one of the two engines. The rotors were connected by a drive shaft along the spine, and an efficient transmission funneled each of the engines output to a single source. Should one engine fail, both rotors were still supplied with the remaining power available. These aircraft are still heavily used by the military of numerous countries. The success of Desert Storm depended greatly on flanking the Iraqi's by placing troops, equipment, fuel and ammunition hundreds of miles into the Iraqi desert. I am sure that I told you more than you asked, but I could not resist the impulse to pontificate. Barry Echols Alert Edit | Reply | Reply With Quote | Top

Table of Contents

Subject      Author      Message Date     ID      RE: Tandem Rotor Helicopters Mike_Greenwood 06-30-02 1   RE: Tandem Rotor Helicopters vgbaron 06-30-02 2   RE: Tandem Rotor Helicopters MarkMcMaster 06-30-02 3   RE: Tandem Rotor Helicopters DeeWaldron 06-30-02 4    RE: Tandem Rotor Helicopters Ben_Chiu 07-01-02 5         RE: Tandem Rotor Helicopters RickLee 07-01-02 6              RE: Tandem Rotor Helicopters James 07-01-02 7              RE: Tandem Rotor Helicopters BillC 07-01-02 9              RE: Tandem Rotor Helicopters Emile 07-03-02 12   RE: Tandem Rotor Helicopters James 07-01-02 8    RE: Tandem Rotor Helicopters DeeWaldron 07-01-02 10         RE: Tandem Rotor Helicopters BDEchols 07-22-02 22              RE: Tandem Rotor Helicopters DeeWaldron 07-22-02 23         RE: Tandem Rotor Helicopters Kopterdok 07-27-02 25    RE: Tandem Rotor Helicopters BDEchols 07-03-02 11         RE: Tandem Rotor Helicopters James 07-03-02 13              RE: Tandem Rotor Helicopters vgbaron 07-04-02 14                   RE: Tandem Rotor Helicopters James 07-04-02 15                        RE: Tandem Rotor Helicopters BDEchols 07-16-02 16                             RE: Tandem Rotor Helicopters Mike_Greenwood 07-16-02 17                                  RE: Tandem Rotor Helicopters James 07-16-02 19                             RE: Tandem Rotor Helicopters James 07-16-02 18                             RE: Tandem Rotor Helicopters PaulCroft 07-16-02 20                             RE: Tandem Rotor Helicopters vgbaron 07-17-02 21   CH-47F Chinook in the news Ben_Chiu 07-22-02 24

Forums | Topics | Previous Topic | Next Topic

Messages in this topic

Mike_Greenwood Certificates/Ratings/Crew Stations: 1. "RE: Tandem Rotor Helicopters" 06-30-02, 15:31z  Hi Barry, Thanks so much for all of that info. I will admit that I too was one who subscribed to all of the misconceptions you cited <g>. I have a newfound respect for those behemoths. --Greenie **6 miles SSE KSJC** -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: Mike Greenwood -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

vgbaron Certificates/Ratings/Crew Stations: 2. "RE: Tandem Rotor Helicopters" 06-30-02, 17:28z  Barry - Thank you! That was really informative and, as Mike said, it dispelled some misconceptions that I had. Anytime you want to share any additional info, I, for one, would welcome it. Vic -= VPC OffLine Reader Version 1.1.1.0 =- Registered to: Vic Baron -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

MarkMcMaster Certificates/Ratings/Crew Stations: 3. "RE: Tandem Rotor Helicopters" 06-30-02, 21:27z  Barry, Wonderful explanation. Thank you, I learned a great deal. Mark -= VPC OffLine Reader Version 1.1.0.0 =- + UNREGISTERED + -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

DeeWaldron Certificates/Ratings/Crew Stations: 4. "RE: Tandem Rotor Helicopters" 06-30-02, 23:09z  I crew chief'ed 47's in 'Nam, Alaska and Georgia (old "A" models mostly, and a "C" model while in Alaska). "Slinging" one-oh-five-mike-mikes around. I can still hear the "Snake" pilots who were escorting us into and out of the LZ's to "slow down a little please!" LOL! Cheers, Dee Waldron (HJG) Remove | Alert Edit | Reply | Reply With Quote | Top

Ben_Chiu Certificates/Ratings/Crew Stations: 5. "RE: Tandem Rotor Helicopters" 07-01-02, 04:24z  > I crew chief'ed 47's in 'Nam, Alaska and Georgia (old "A" models > mostly, and a "C" model while in Alaska). Hey great! Barry used to fly them in Vietnam. I'm sure you guys have a lot of stories to tell about it. Small world... Ben -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: Ben Chiu -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

RickLee Certificates/Ratings/Crew Stations: 6. "RE: Tandem Rotor Helicopters" 07-01-02, 17:39z  Hi... I've been away from the forum for a long time. I was just reading some messages and thought I'd jump on this thread with a question. Does anybody know what happened to Keith's Virtual Helipad? The old address was: http://members.aol.com/keitht777/helipad.html The page is gone from the AOL system. It was really a great resource for those of us who mainly fly helicopters in FS. If Keith doesn't have a new site (searches have turned up nothing) then at least I hope that Keith put the files with another site. Rick Lee www.rickleephoto.com Remove | Alert Edit | Reply | Reply With Quote | Top

James Certificates/Ratings/Crew Stations: 7. "RE: Tandem Rotor Helicopters" 07-01-02, 20:03z  Hi Rick, Unfortunately Kieth was unfit to continue running his site and it was closed some time ago which to me personally was a great pity. I've never heard on the grape vine as to whether it will re-emerge at a later date. Regards, James (CONman) Anderson -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: James Anderson -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

BillC Certificates/Ratings/Crew Stations: 9. "RE: Tandem Rotor Helicopters" 07-01-02, 21:20z  Hi Rick.. > Does anybody know what happened to Keith's Virtual Helipad ? < I seem to recall that Keith ceased his site activities, because of health reasons. I cannot remember the details, but his 'closedown' notice sounded pretty final. I don't recall seeing anything regarding his files going anywhere. Nice to see you again. Regards BillC Formby, UK -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: Bill Cusick -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

Emile Certificates/Ratings/Crew Stations: 12. "RE: Tandem Rotor Helicopters" 07-03-02, 05:30z  Hello Rick, I love the "Alien Song" available on your http://www.rickleephoto.com/rlalien.htm (for the ones who do not know what I am talking about) Regards Emile EBBR Remove | Alert Edit | Reply | Reply With Quote | Top

James Certificates/Ratings/Crew Stations: 8. "RE: Tandem Rotor Helicopters" 07-01-02, 20:03z  Hi Barry, Nice write up my friend. Bring's back a few memories I know a number of years ago just prior to the Chinook crash in Scotland that Killed all SAS, MI5/6 and Ulster Constabulary Top Brass and crew that the RAF Pilots refused to fly the latest versions due to a lot of instability etc in the new engines etc. It took some time but it's now been agreed by the Crash investigators and the Government to remove ALL blame from the Flight Crew. It's now been classed as Mechanical Error (unknown)!! The reason of argument was that in a crash of this kind the transponder code would remain the same. It was known ALL along that the first two digits had been changed (prior to the accident) to 77. Regards, James (CONman) Anderson -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: James Anderson -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

DeeWaldron Certificates/Ratings/Crew Stations: 10. "RE: Tandem Rotor Helicopters" 07-01-02, 23:15z  As far back as the old A-model that I worked on, the Chinook (*hit-hook is what we called them) was know to be a touchy and difficult maintenance beast. For every one hour of flight time, it required 5 to 6 man hours of maintenance upkeep. There were a couple of well known (and filmed!) Chinook crashs where the rear x-mission tore itself loose and yanked the entire rear pylon off the aircraft. Truthfully, I was scared to death of that aircraft! Hell, I was only 19, 20 years old back then. I crawled all over my ship when I didn't have anything else to do, checking to make sure all the cotter pins were still in place, no broken safety wires (and there were lots of them!), and putting the torque wrench on everything! Dee Remove | Alert Edit | Reply | Reply With Quote | Top

BDEchols Certificates/Ratings/Crew Stations: 22. "RE: Tandem Rotor Helicopters" 07-22-02, 05:10z  Hi Dee Waldron, I owe you an apology for the derogatory comment I made on another message string. After your first post on this string, identifying yourself as a Vietnam vet I was eager to talk to you about your experiences as Flight Engineer on Chinooks. Vietnam vets are dwindling in number. I am certain that James Anderson’s post had no bearing on your subsequent post a few hours later. It was wrong of me to imply that his post influenced you. I am sorry that your experience with the CH47 Chinook was unfavorable. I am sure that you have valid reasons for your opinion. I do know that thousands of other crew members have a more favorable impression of the safety and capabilities of the Chinook. Barry Echols Remove | Alert Edit | Reply | Reply With Quote | Top

DeeWaldron Certificates/Ratings/Crew Stations: 23. "RE: Tandem Rotor Helicopters" 07-22-02, 22:53z  No Problem Barry! On second thought, I shouldn't have said I was scared of the 'hook... I should have said I had a healthy respect for what it would do to me, if I didn't do my job right. I hope that's better stated. Cheers! Dee Remove | Alert Edit | Reply | Reply With Quote | Top

Kopterdok Certificates/Ratings/Crew Stations: 25. "RE: Tandem Rotor Helicopters" 07-27-02, 00:45z  Hello Dee, I am a helicopter mechanic trained on Chinooks, I have over 17 years of experience, having worked on the B, C, and D model series of Chinooks and I know them to have one of the best records in rotary winged aviation! I know of some of the crash footage you mentioned, and one in particular was very popular with the media, it occoured in Germany in 1982, the helicopter was flying a load of German parachuters and was at 5000 ft. or so when the crew observed a chip light on the master caution panel, they went through their required procedures and were decending to make a precautionary landing, at approx. 600 ft. they made a power change to lenghten their approach path which resulted in the seizing of the forward transmission. The end result was that all engine torque was transmitted to the aft rotor which tore the aft transmission and aft rotary shaft, along with the aft rotor head assembly from the airframe. The helicopter impacted on its side on a german highway. The subsequent crash investigation concluded that walnut shell fibers had, over a period of time, clogged the oil lubrication jets that feed the main bull gears in the forward transmission causing those gears to overheat and subsequently, to seize up. The blame ended up falling with OSHA, when they visited the overhaul facility in Corpus Christi Texas, they said of the machine that is used to clean the transmission casings (using walnut shells)that the pressure setting was too high and ordered it decreased, the end result is what I described above. The point of this whole story is to show that in every case that I am aware of involving a Chinook crash, the cause was human error, not design flaw. I'm sure the Chinook went through its growing pains along with most other aircraft, but it has amassed an excellent safety record in its many years of existence. I hope you will find this informative. Sincerely, Shawn Carmody Remove | Alert Edit | Reply | Reply With Quote | Top

BDEchols Certificates/Ratings/Crew Stations: 11. "RE: Tandem Rotor Helicopters" 07-03-02, 01:26z  Hi James, I am glad you took the effort to respond to my message even though it was a slam on the Hook. Of all the Vietnam era ships, only the CH47 remains in service. The Huey, Loach, and Cobra are retired. In fact, the CH47 is still in extensive use by the RAF, even more widely used in the UK than in the US. I know of no aircraft, from the very earliest that has not claimed lives from mechanical defaults. Aviation is inherently dangerous, and fling wing ships are doubly prone due to the great number of slinging parts that can fail with catastropic results. I am currently in contact with various personnell that flew or performed maintenance on various helicopters. Some call a few of the newer single rotor craft "lawn darts." I stand by my claim that the CH47 is a proven and valuable design and still in active use. It took me safely through a tour in Vietnam without fault. Remove | Alert Edit | Reply | Reply With Quote | Top

James Certificates/Ratings/Crew Stations: 13. "RE: Tandem Rotor Helicopters" 07-03-02, 17:08z  Hi Barry, My pleasure and I didn't take it as a slam on the CH47 What I gather now from various folk in the RAF that all the faults they reported on the new CH47 have supposedly been ironed out Theres even a couple of female pilots flying them in Afghanistan at the moment so they can't be all that bad now Regards, James (CONman) Anderson -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: James Anderson -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

vgbaron Certificates/Ratings/Crew Stations: 14. "RE: Tandem Rotor Helicopters" 07-04-02, 16:39z  > Theres even > a couple of female pilots flying them in Afghanistan at the moment so > they can't be all that bad now Better hope Patty isn't monitoring this forum, James or you're in DEEP do-do! Vic -= VPC OffLine Reader Version 1.1.1.0 =- Registered to: Vic Baron -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

James Certificates/Ratings/Crew Stations: 15. "RE: Tandem Rotor Helicopters" 07-04-02, 18:10z  Ha ha ha Regards, James (CONman) Anderson -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: James Anderson -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

BDEchols Certificates/Ratings/Crew Stations: 16. "RE: Tandem Rotor Helicopters" 07-16-02, 14:13z  Hi James, Don't worry my friend. I will not post again on this board. You have made it very clear I am not welcome. Barry Echols Hook Pilot CH47 Chinook Vietnam Remove | Alert Edit | Reply | Reply With Quote | Top

Mike_Greenwood Certificates/Ratings/Crew Stations: 17. "RE: Tandem Rotor Helicopters" 07-16-02, 20:01z  >>Don't worry my friend. I will not post again on this board. You have made it very clear I am not welcome.<< Whoa there Barry, what brought that on? I didn't see anything from any of James' posts that would cause that reaction. If you're referring to the >>ha ha ha<< that was a response to Vic, and has always been a way that James expresses "LOL." The web based view of the forum can make it a tad difficult to see the threading, and who is responding to what. Try our OLR and the threading is much clearer. More importantly, STICK AROUND! <g> Your knowledge of the "fling wings" is invaluable (as is James'), and I for one would miss your expertise in the area. --Greenie **6 miles SSE KSJC** -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: Mike Greenwood -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

James Certificates/Ratings/Crew Stations: 19. "RE: Tandem Rotor Helicopters" 07-16-02, 21:40z  Hi Mike/Barry, Well this has certainly knocked me for six as I for one have in no way written any thing that would offend you or any one else on this subject as it's one I'm passionate about just as you are Barry. As Mike pointed out he couldn't see any thing in which would have such an adverse reaction. You flew in an era that I didn't and I enjoy reading them and admire you guy's that flew at that time and as Mike knows If I drop a clanger then I immediately put my hands up to it and whole heartedly apologies if any of my posts have offended you or any one else my friend. Regards, James (CONman) Anderson -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: James Anderson -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

James Certificates/Ratings/Crew Stations: 18. "RE: Tandem Rotor Helicopters" 07-16-02, 21:40z  Hi Barry, Now you have truly lost me some where along the line? As previously requested, which post are we referring to this particular statement? Regards, James (CONman) Anderson -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: James Anderson -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

PaulCroft Certificates/Ratings/Crew Stations: 20. "RE: Tandem Rotor Helicopters" 07-16-02, 21:52z  Hi Barry >> Don't worry my friend. I will not post again on this board. You have made it very clear I am not welcome. << Have I missed something here?? I've just been back through all these messages and can't see anything which might have caused offence. I've known James for a long time now and there's no way he'd deliberately do that. Just as important, it's input like yours which makes this forum the one place I love to visit. Informed comment on 'fling wings' (a new term to me and highly appropriate) is always welcome. Whatever the perceived slight was, please try and put it behind you. I'm certain it wan't intentional. Paul Croft 10 miles SE of Heathrow (EGLL) -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: Paul F. Croft -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

vgbaron Certificates/Ratings/Crew Stations: 21. "RE: Tandem Rotor Helicopters" 07-17-02, 15:51z  Hey Barry - I also just reread this entire thread and couldn't find anything to prompt your reaction. That's what I hate about the written word - you can put all the smileys, or *BOLD* that you want but it's difficult to convey the tone of the post. Hopefully you will rethink your position - I for one enjoy your comments, also at the chats. Vic Of all the things I've lost - I miss my mind the most -= VPC OffLine Reader Version 1.1.0.0 =- Registered to: Vic Baron -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

Ben_Chiu Certificates/Ratings/Crew Stations: 24. "CH-47F Chinook in the news" 07-22-02, 22:57z  Coincidentally, the 08-02 issue of Flying Magazine wrote that Boeing delivered the first remanufactured CH-47F Chinook. One of two prototypes is to begin evaluation by the US Army. First production to begin in January 03. 300 CH-47D's will be upgraded to the F model and will are planned to remain in service until the mid 2030! According to my math, the CH-47 will be a 70+ year old design by then!! Ben -= VPC OffLine Reader Version 1.1.2.0 =- Registered to: Ben Chiu -OLR.PL v1.76- Remove | Alert Edit | Reply | Reply With Quote | Top

Lock | Archive | Remove

Forums | Topics | Previous Topic | Next Topic

Select another Forum ===================== FlightAdventures Virtual Pilot Center™ (Forums)   |--FSFORUM   |--Aerobatics and Air Shows   |--The Future for GA   |--Airframes and Powerplants   |--Airlines and Airliners   |--Fighters and Warbirds   |--Flight Training   |--Aviation Safety   |--File Library - Upload, Search, and Download   |--VPC Tech