From: skunk-works-digest-owner@mail.orst.edu To: skunk-works-digest@mail.orst.edu Subject: Skunk Works Digest V5 #281 Reply-To: skunk-works-digest@mail.orst.edu Errors-To: skunk-works-digest-owner@mail.orst.edu Precedence: bulk Skunk Works Digest Friday, 26 May 1995 Volume 05 : Number 281 In this issue: Re: Woodpecker ROADMAP Internet Lessons via EMAIL [*Free*] Quiet Helicopters... RE: Re(2): quiet helicopters U-2 Overflights Re: Quiet Helicopters... Oops... See the end of the digest for information on subscribing to the skunk-works or skunk-works-digest mailing lists and on how to retrieve back issues. ---------------------------------------------------------------------- From: jburtens@bournemouth.ac.uk (John Burtenshaw) Date: Thu, 25 May 1995 09:31:49 +0100 Subject: Re: Woodpecker Gordon wrote: >Fellow Skunk'sters > >Michelle wrote recently questioning about the former Soviet >"Woodpecker" system. Dwp replied indicating the true use of the >Woodpecker as an over the horizon radar (OTHR) system. I'd just like >to chip in that the Woodpecker is definitely an OTHR facility, >although I suspect has fallen on hard times of late. (STUFF DELETED) >For those interested Australia is constructing an OTHR network >comprising the existing Jindalee radar in central Australia plus two >new radars located in Western Australia and Queensland. The full three >radar networked system is called JORN, for Jindalee Operational Radar >Network. Each receiving array is several km long - visually rather >impressive! As a licenced radio amateur (and also keen Skunker) I feel a twinge of horror to think that the HF spectrum will be polluted by more noise. It was bad enough when the Russian Woodpecker was operating. Does anyone know what frequency range the JORN system will use. I suspect the 11 MHz band as this seems to give very good worldwide coverage (the USAF and RAF use parts of this for their long-range comms). Cheers John =========================================================================== John Burtenshaw Systems Administrator, The Computer Centre, Bournemouth University - --------------------------------------------------------------------------- Postal Address: Talbot Campus, Fern Barrow, POOLE, Dorset, BH12 5BB U.K. Internet: jburtens@bournemouth.ac.uk Phone: 01202 595089 Fax: 01202 513293 AX.25: g1hok@gb7bnm.#45.gbr.eu. AMPRnet: g1hok.ampr.org. (44.131.17.82) CompuServe: 100336,3113 =========================================================================== ------------------------------ From: "Terry Colvin" Date: Thu, 25 May 95 06:42:27 EST Subject: ROADMAP Internet Lessons via EMAIL [*Free*] ROADMAP lessons are available through email from the University of Alabama. Excellent and free instructions on FTP, Telnet, Archie, Gopher, etc. features on the World Wide Web without using a browser program. Anyone interested can email me privately at . Ciao, Terry W. Colvin USMTF Program [Desert Storm I] Fort Huachuca (Cochise County), Arizona TOT: 1341GMT(Zulu) ------------------------------ From: David Lednicer Date: Thu, 25 May 1995 08:52:09 -0700 (PDT) Subject: Quiet Helicopters... I realize that this is a bit off the group's charter, but as a helicopter aerodynamicist, I feel duty bound to correct some inaccuracies I saw in someone's post. Almost any helicopter can loop or roll. However, to survive the manouver, don't ever attmept this in a teetering rotor helicopter. They rely on gravity to provide the control power. In the unloading experienced in a less than perfect loop or roll, gyroscopic forces will take over and cause the rotor to precess. Usually, this ends up with the rotor hub banging against the rotor mast, which usually results in component failure. Teetering rotor helicopters include the Bell 206 (Jetranger), Bell 204 and 205 (Iroquois/Huey), Bell 209 (Cobra), Bell 212, Bell 222 and the Robinson R22 and R44. The 222 has something called a hub spring that does provide some head moment in a low g situation, but I still wouldn't fool with it. I was once told that only one person has ever survived looping a Cobra. Most other helicopters have articulated or rigid hubs, which have varying degrees of safety in aerobatics. I have seen a video of a CH-53 rolling, a S-55 looping and stills of the S-67 looping and rolling, a S-76 rolling and a UH-60 rolling. Byron Graham, a Sikorksy test pilot, is reputed to have rolled every Sikorsky helicopter he ever flew. I have also seen an incredible video of a Bo 105 doing a complete aerobatic routine, including manouvers impossible in an aircraft (how about hammerhead turns, while flying backwards). However, the German pilot who performed the Bo 105 routine was later killed - flying aerobatics in a helicopter. Now on the helicopter speed record - many helicopters are capable of breaking the record, right now. The trouble is, it will cost $ to modify the helicopter and do the flights, so nothing has happened. Believe it or not, the CH-53E, has enough installed power, with minimal drag cleanup, to break the record quite easily. The trouble is, no one is interested in spending the money to do it. Back in 1982, Sikorsky took an S-76 (N5445J) and broke nine records in a five day period. Afterwards, the tail was replaced and the engines were inspected, and then it was delivered to a customer! And this S-76 was powered by Allison 250-C30s - the S-76B and S-76C have more installed power. I have also heard that the Boeing model 360 was within an eyelash of breaking the Lynx's record, but held back to help preserve the V-22 program. - ------------------------------------------------------------------- David Lednicer | "Applied Computational Fluid Dynamics" Analytical Methods, Inc. | email: dave@amiwest.com 2133 152nd Ave NE | tel: (206) 643-9090 Redmond, WA 98052 USA | fax: (206) 746-1299 ------------------------------ From: Kathryn & Andreas Gehrs-Pahl Date: Thu, 25 May 1995 12:27:09 -0400 (EDT) Subject: RE: Re(2): quiet helicopters With respect to the maneuverability of helicopters: >Airwolf couldn't loop the loop and never did in the TV series either, >it's a Bell 222 >However Blue Thunder, Aerospatiale Gazzelle, can nearly do it as >flown by the UK's Navy's Shark display team, >the only other chopper capable is the Hughes Apache. The first helicopter ever to make a 'loop' or a 'roll', meaning controlled flight upside-down, was the Eurocopter (MBB) Bo-105. The technology to achieve this goal was a special rigid rotor hub (head) and composite blades. Other helicopters, in fact most current generation helicopters, are able to do the same now, including: - - Westland Lynx AH Mk.11 - - Eurocopter (Aerospatial) Panther - - MDD (Hughes) AH-64 Apache - - Sikorsky S-70 versions (UH-60 Blackhawk) - - Kamov Ka-50 'Hokum' - - Eurocopter Tiger With respect to the speed of helicopters: >The Lynx of course holds the world speed record @281 mph, I'm nearly >sure that this is about the maximum speed a helicopter will ever go. Technologies to make helicopters faster include specially formed rotor blades and rotor blade tips, streamlining, additional lift surfaces, additional cruise engines, and -- put to the extreme -- X-wing or retractable rotor blades. Apparently, all of this was tested with the Sikorsky S-72 RSRA and later (or parallel) by secret 'black' military test programs in the USA. I am pretty sure some hardware was tested, at least in the form of drones -- which flew quite a bit faster. With respect to the sound of helicopters: >I'm sure at some stage and possibly now it will be possible to make >any aircraft silent using modern accoustic technologies such as >Anti-noise. Their are already headphones available that make >anti-noise in real time so when you're in the cockpit you can't hear >the engine at all. This has brought an additional problem in that the >pilot can't hear when the engine is running rough etc. Adding 'Anti-noise' only helps partially. The two main sources for noise produced by a helicopter are the engine(s) and the rotor-blades (air). You can muffle an engine, and use even (limited amounts of) active anti-noise to make them nearly totally silent. Right now, a lot of research goes into active dampening of vibrations of the helicopter, to decrease fatige and sound emissions. The problem with active noise/vibraton-cancellation is, that you have to know the frequency and amplitude of the sound/vibration BEFORE it is created, because you have to send the negative wave at the SAME TIME to cancel each other. So the only feasable way for noise cancellation is knowing the general form of the wave, and adapt for amplitude and other variables by using microphones and other data, like rpm of rotor, rpm of engines, position of the rotor blades at any given moment, etc. There is no way to have a microphone and use some secret 'black box' to somehow phase-shift the signal by 180 degrees and put it out again, canceling the original sound. It only works if you know what sound will come in -- that's why they always need so much research in figuring out the general sound characteristics of power plants, chimneys, cars, aircraft, cockpits, or offices etc. before they can use active noise-cancellation. Headphones with active noise-cancellation only remove the more or less CONSTANT background noise, often only in a limited frequency range, not any sound around you, like voices -- otherwise they would be useless. By the way, the same is true for active radar cancellation -- even much more complicated -- because sound is relatively slow, but radar has the speed of light. :) - -- Andreas - --- --- Andreas & Kathryn Gehrs-Pahl E-Mail: schnars@ais.org 313 West Court St. #305 or: gpahl@raptor.csc.flint.umich.edu Flint, MI 48502-1239 Tel: (810) 238-8469 WWW URL: http://www.umcc.umich.edu/~schnars/ - --- --- ------------------------------ From: "Robert S. Hopkins, III" Date: Thu, 25 May 1995 10:51:40 -0400 Subject: U-2 Overflights During his opening remarks at the recent CORONA conference, DCI John Duetch announced that there were 24 (twenty four) CIA U-2 overflights of the USSR. In a discussion I had immediately afterward with Chris Pocock (author of _Dragon Lady_), we agreed that 24 was consistent with all of the evidence we had found, although there were 4 (four) missions that appeared to have overflown the USSR but were not INTENDED to do so, which accounts for why we both came up with 28 (twenty eight) missions. Although the CORONA data were declassified and thoroughly discussed, the consensus was that we would have to wait quite a bit longer for the CIA to declassify its history of AQUATONE, the U-2 program. Chris suggested that this was primarily due to reservations about declassification held by Her Majesty's Government, considering their involvement in the overflights (including two overflights of the USSR by RAF pilots). Ah, one day.... Robert S. Hopkins, III Corcoran Department of History Randall Hall University of Virginia Charlottesville VA 22906 internet: rsh8s@virginia.edu ------------------------------ From: kuryakin@arn.net (Illya Kuryakin) Date: Thu, 25 May 1995 13:26:11 -0500 Subject: Re: Quiet Helicopters... + + Now on the helicopter speed record - many helicopters are capable +of breaking the record, right now. The trouble is, it will cost $ to +modify the helicopter and do the flights, so nothing has happened. +Believe it or not, the CH-53E, has enough installed power, with minimal +drag cleanup, to break the record quite easily. The trouble is, no one I remember hearing that the CH-54 was the bird that broke the time-to-climb record, as well. Rick Pavek kuryakin@arn.net ------------------------------ From: David Lednicer Date: Thu, 25 May 1995 11:56:44 -0700 (PDT) Subject: Oops... I got so busy ranting about helicopters that I forgot to make the points I set out to talk about! As to those quiet helicopters - active noise control is rather unlikely. The way active noise works is that you send out a signal that is exactly out of phase with the transmitted noise, so that positive and negative nodes coincide and cancel. The trouble is, that you must focus on a region where this is going to happen. In headphones, this is your ear, but it is much more difficult in "free space". They have installed active noise in the Saab 2000 interior, but it is focused at the ear level of the passengers. I am told that people walking in the aisle don't benefit from the active noise. Now, on the flip side, what can be done? In the 1970s the US Army put out contracts to look into this. Hughes took a OH-6, added a blade to the main rotor, two blades to the tail rotor and a BIG muffler to the engine exhaust. I think they also slowed down the rotor speed, and all this resulted in a very quiet helicopter. Different helicopters have different "worst offenders". On the S-76 the tail rotor produces a good hunk of the noise signature, while on the Huey its the main rotor. When I lived in Connecticut, I got to be real good at recognizing various models of helicopters from their noise signatures. One day, I was out working in the yard and suddenly realized that there was a helicopter hovering right over me that I hadn't been aware of. It was a S-58T. I later asked at work why it was so quiet and was told that it has a relatively low main rotor tip speed, quiet tail rotor and quiet engines. Enough for now - its time to go out and paint my R-22 black. I want to got out and give some of those conspiracy types a thrill this weekend! - ------------------------------------------------------------------- David Lednicer | "Applied Computational Fluid Dynamics" Analytical Methods, Inc. | email: dave@amiwest.com 2133 152nd Ave NE | tel: (206) 643-9090 Redmond, WA 98052 USA | fax: (206) 746-1299 ------------------------------ End of Skunk Works Digest V5 #281 ********************************* To subscribe to skunk-works-digest, send the command: subscribe skunk-works-digest in the body of a message to "majordomo@mail.orst.edu". If you want to subscribe something other than the account the mail is coming from, such as a local redistribution list, then append that address to the "subscribe" command; for example, to subscribe "local-skunk-works": subscribe skunk-works-digest local-skunk-works@your.domain.net To unsubscribe, send mail to the same address, with the command: unsubscribe skunk-works-digest in the body. Administrative requests, problems, and other non-list mail can be sent to either "skunk-works-digest-owner@mail.orst.edu" or, if you don't like to type a lot, "prm@mail.orst.edu A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace all instances of "skunk-works-digest" in the commands above with "skunk-works". Back issues are available for anonymous FTP from mail.orst.edu, in /pub/skunk-works/digest/vNN.nMMM (where "NN" is the volume number, and "MMM" is the issue number).