Kusch Posted October 31, 2007 Posted October 31, 2007 Chinook ground resonance Give me "flying telephone pole" (SA-2)!
Sundowner.pl Posted October 31, 2007 Posted October 31, 2007 Yeah, ground resonance might be a pain in th butt (literally :smilewink: ), wonder if it's simulated in BS :joystick: It may occur during the landing when touching the ground to hard, the solution is to take the machine up into hover and wait for that oscillations to stop by them self. Especially prone to this are the two bladed helicopters like Robinsons, Hueys, Jet Rangers/Creeks. Helicopters with rigid rotors, especially with elastomeric bearings and composite blades (like the OH-58D) don't see that problem much, but I read few reports of A-Stars scraped or badly damaged by this. [sIGPIC][/sIGPIC] "If a place needs helicopters, it's probably not worth visiting." - Nick Lappos
Ditch3r Posted October 31, 2007 Posted October 31, 2007 I remember that clip... :cry: https://www.youtube.com/@ditch3rgames
Aeroscout Posted October 31, 2007 Posted October 31, 2007 ouch! Was anyone hurt? DCS Wishlist: 1) FIX THE DAMN RIVERS!!! 2) Spherical or cylindrical panorama view projection. 3) Enhanced input options (action upon button release, etc). 4) Aircraft flight parameter dump upon exit (stick posn, attitude, rates, accel, control volume, control-surface positions, SAS bias, etc). 5) ADS-33 maneuver courses as static objects. 6) Exposed API or exports of trim position and stick force for custom controllers. 7) Select auto multiple audio devices
Joe Kurr Posted October 31, 2007 Posted October 31, 2007 I don't think anyone was hurt. Looking at the way it's tethered up, I'd say it is a test run. Dutch Flanker Display Team | LLTM 2010 Tiger Spirit Award
Ditch3r Posted October 31, 2007 Posted October 31, 2007 Yes it was a test. They created the video to show the effects. https://www.youtube.com/@ditch3rgames
Vekkinho Posted November 1, 2007 Posted November 1, 2007 It's the stupidest test ever done, testing resonance with Chinooks after 40 years of service = wrecking helos intentionally...that's like ramming your old car that noone wants to buy agains the wall and enjoying it, IMHO! [sIGPIC][/sIGPIC]
Sundowner.pl Posted November 1, 2007 Posted November 1, 2007 Ekhm.... Boeing Chinooks just won the USAF CSAR order :music_whistling: [sIGPIC][/sIGPIC] "If a place needs helicopters, it's probably not worth visiting." - Nick Lappos
Ditch3r Posted November 1, 2007 Posted November 1, 2007 Just a guess here.... But I imagine they used a Chinook because they are one of the cheapest birds in service. https://www.youtube.com/@ditch3rgames
graywo1fg Posted November 1, 2007 Posted November 1, 2007 this can happen in the air too when carrying extremely heavy loads. Voice of Jester AI Death From Above =DFA= Squadron Discord - https://discord.gg/deathfromabove http://www.twitch.tv/graywo1f https://www.youtube.com/user/Lonewo1fg
G3 Posted November 1, 2007 Posted November 1, 2007 quite fascinating really, had not seen this before, forgive my ignorance. definately seems like something you don't want :) o/t: took my 8yo son for a chopper flight around Mt Panorama this year while watching the bathurst v8supercars, was pretty cool. it was a jet ranger i thought, but the pilot informed me it was a 406, very similar, more powerful etc. the young fella was quite reluctant at first but the second it left the ground the look of excitement on his face was priceless, i too enjoyed it immensely. glad the 406 didn't have one of these blade snapping death wobbles:thumbup:
Eagle Driver Posted November 1, 2007 Posted November 1, 2007 I thought the 406 WAS a jetranger, 405 being Huey? Wrong? [sIGPIC][/sIGPIC] If you fly a perfect Defensive BFM and the bandit does a perfect Offensive... Someone you know is going to be recieving Insurance money very soon.
Mugatu Posted November 1, 2007 Posted November 1, 2007 Thought the Airforce was told to retender it? http://www.flightglobal.com/articles/2007/10/25/218898/usaf-attempts-to-revive-csar-x-contest-upset-boeing.html :music_whistling: Ekhm.... Boeing Chinooks just won the USAF CSAR order :music_whistling:
Sundowner.pl Posted November 1, 2007 Posted November 1, 2007 Yup, wrong ;) 206 is the Jet Ranger, 205 and 210 are Hueys , 212 and 412 are Twin Hueys. There is a 407, thats a Long Ranger with 4 bladed rotor identical to that of OH-58D Kiowa Warrior. Actually, all Bells which number start with 2, have two-bladed rotor, and the one with 4 are four-bladed. [sIGPIC][/sIGPIC] "If a place needs helicopters, it's probably not worth visiting." - Nick Lappos
Kusch Posted January 18, 2008 Author Posted January 18, 2008 HH-47 CSAR commercial video: http://www.boeing.com/rotorcraft/military/hh47/csarvideo.html Give me "flying telephone pole" (SA-2)!
GreyStork Posted January 18, 2008 Posted January 18, 2008 Evil vibes This topic suddenly has me wondering if it might be a bad idea to fire the Ka-50's gun in auto-hover. I assume there must exist a resonance frequency stemming from the delay between INS, radar altimeter, and/or attitude gyro input and actual swash plate actuation. Should the cannon firing cycle hit that exact frequency, it might pose a real risk. You can release the trigger, that's true, but who's to say the vibration won't self-amplify under those specific circumstances? Oh well, I'm sure Kamov's engineers have thought about all that. :smilewink: [sIGPIC][/sIGPIC] - Study flight sim geek since Falcon 3.0 -
britgliderpilot Posted January 18, 2008 Posted January 18, 2008 This topic suddenly has me wondering if it might be a bad idea to fire the Ka-50's gun in auto-hover. I assume there must exist a resonance frequency stemming from the delay between INS, radar altimeter, and/or attitude gyro input and actual swash plate actuation. Should the cannon firing cycle hit that exact frequency, it might pose a real risk. You can release the trigger, that's true, but who's to say the vibration won't self-amplify under those specific circumstances? Oh well, I'm sure Kamov's engineers have thought about all that. :smilewink: . . . it's not exactly a likely scenario, though, is it ;) If by some bizarre coincidence it was a problem . . . well they had interrupter gear as far back as WW1 . . . I don't think I've suffered from ground resonance in a Ka50 yet, and I've destroyed that helicopter in some fairly spectacular ways. Whether that means the Ka50 isn't susceptible to ground resonance, it's not modelled, or I've just not provoked it yet, I don't know. It indicates it's not likely to be a problem, anyway . . . now whether you breathe a sigh of relief at one less way to destroy your helicopter, or are disappointed in the lack of variety this presents in ways to destroy your chopper is up to you :P http://img.photobucket.com/albums/v121/britgliderpilot/BS2Britgliderpilot-1.jpg
GreyStork Posted January 19, 2008 Posted January 19, 2008 I don't think I've suffered from ground resonance in a Ka50 yet, and I've destroyed that helicopter in some fairly spectacular ways. Whether that means the Ka50 isn't susceptible to ground resonance, it's not modelled, or I've just not provoked it yet, I don't know. You sound like a man on a mission! ;) As for ground resonance, I imagine that it would be less of a problem for a coaxial design, since any rocking would result in symmetric, but opposite, blade bunching in the two rotor discs. Hence, the kind of swirling imbalance you see in the Chinook video shouldn't happen. If you think about it, the increased lift from the forward-leaping blade in one disc would be countered by decreased lift from the lagging blade at the same location in the other disc. This didn't work for the Chinook, because the rotor discs were located on separate axes, allowing a dissymmetry of forces to arise. On the other hand, if you ignore lift and only factor in blade bunching oscillations from a swirling rocking motion, the Black Shark's taller rotor shaft would make it more susceptible to ground resonance. Then again, the lesser blade length, compared to a conventional tail rotor configuration, would result in reduced centrifugal forces during ground resonance. I'm beginning to feel like Tevye in Fiddler On The Roof. :ermm: On the other hand... It indicates it's not likely to be a problem, anyway . . . now whether you breathe a sigh of relief at one less way to destroy your helicopter, or are disappointed in the lack of variety this presents in ways to destroy your chopper is up to you :P Can I check both of the above? :) [sIGPIC][/sIGPIC] - Study flight sim geek since Falcon 3.0 -
RvETito Posted January 19, 2008 Posted January 19, 2008 The Kamov helicoper are threatened by ground resonance like any other helicopters. They have valves in the shock struts of the landing gears that damp such oscillations and you gotta be a real talent to screw it up :) In general- avoid taxiing near the lift off colelctive value, either take-off or taxi at smaller collective. "See, to me that's a stupid instrument. It tells what your angle of attack is. If you don't know you shouldn't be flying." - Chuck Yeager, from the back seat of F-15D at age 89. =RvE=
Kusch Posted December 9, 2008 Author Posted December 9, 2008 Korean Chinook: http://www.militaryphotos.net/forums/showpost.php?p=3749617&postcount=536 Give me "flying telephone pole" (SA-2)!
tusler Posted December 9, 2008 Posted December 9, 2008 H3 and H53's are prone to this during startup of the rotor they wobble like a weeble but don't fall over. On aircraft carrier we chain down all helo's and planes, during heavy seas the chains stay on the helo until it is actually ready to lift off, but what we did was loosen the chains so they had lots of play, if the chains we not slack enough the helo would enter resonance and vibrate itself to pieces. Ask Jesus for Forgiveness before you takeoff :pilotfly:! PC=Win 10 HP 64 bit, Gigabyte Z390, Intel I5-9600k, 32 gig ram, Nvidia 2060 Super 8gig video. TM HOTAS WARTHOG with Saitek Pedals
Esac_mirmidon Posted December 9, 2008 Posted December 9, 2008 Great pics Kusch " You must think in russian.." [sIGPIC][/sIGPIC] Windows 7 Home Premium-Intel 2500K OC 4.6-SSD Samsung EVO 860- MSI GTX 1080 - 16G RAM - 1920x1080 27´ Hotas Rhino X-55-MFG Crosswind Rudder Pedals -Track IR 4
Draco Posted December 9, 2008 Posted December 9, 2008 Hmm... seems it won't let me quote. Sundowner, actually two blade Helis can't experience ground resonance because they lack Lead-Lag hinges, Only 3+ blade fully articulated rotor systems can become imbalanced about the hub.
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