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#1
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More Questions about coning forces & rotor noise!!
If you start a descent from cruse by reducing pitch and maintaining
rotor speed, what happens to coning forces as compared to cruse? I have noticed that during a decent in a R22 that you can get a "Wop-Wop" noise from the main rotor blades. Changing cyclic or increasing rotor speed a very small amount can make it go away, or at least not heard from the cockpit. Can someone explain what is occurring and why? Thanks, Eric D |
#2
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Not sure how much its related to coning, but the whop whop sound is caused
by the blade slapping the vortex wake from the blade before. It happens predictably within specifc range of descents and airspeeds. Bart "Eric D" wrote in message om... If you start a descent from cruse by reducing pitch and maintaining rotor speed, what happens to coning forces as compared to cruse? I have noticed that during a decent in a R22 that you can get a "Wop-Wop" noise from the main rotor blades. Changing cyclic or increasing rotor speed a very small amount can make it go away, or at least not heard from the cockpit. Can someone explain what is occurring and why? Thanks, Eric D |
#3
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"Eric D" wrote in message om... If you start a descent from cruse by reducing pitch and maintaining rotor speed, what happens to coning forces as compared to cruse? I have noticed that during a decent in a R22 that you can get a "Wop-Wop" noise from the main rotor blades. Changing cyclic or increasing rotor speed a very small amount can make it go away, or at least not heard from the cockpit. Can someone explain what is occurring and why? You're probably talking about when you descend 300-500'/min at around 80-85 kt. This is your blade chopping the vortex left by the previous one and can be stopped by increasing your descent, speeding up or slowing down. It's not down to coning forces. Regards Andrew -- Inweb Networks. Quality internet and telecoms services Sales: 08000 612222 Support: 08704322222. http://www.inweb.co.uk E1 call share - 65%. 0800, 0845 and 0870 numbers - best rates. Resellers welcome |
#4
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Along these lines, what causes the loud burbling blade noise in a MD 500 in
turbulence. Is it just caused by a larger than naormal vortex burbble? Craig |
#5
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It's not down to coning forces.
Regards Andrew Hi Bart & Andrew, Maybe I didn't word this properly or maybe I should have put it as to separate postings. These are two separate questions. I didn't intend them to be interrupted as part of the same question. Seeing that the focus so far is on the noise question, and it seems that it has to do with the blade colliding with the previous blades vortexes from the posting responses so far. Is this something to avoid? Does it cause harm to anything with the helicopter? |
#6
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In article , Eric D
wrote: It's not down to coning forces. Regards Andrew Hi Bart & Andrew, Maybe I didn't word this properly or maybe I should have put it as to separate postings. These are two separate questions. I didn't intend them to be interrupted as part of the same question. Seeing that the focus so far is on the noise question, and it seems that it has to do with the blade colliding with the previous blades vortexes from the posting responses so far. Is this something to avoid? Does it cause harm to anything with the helicopter? Blade slap or whatever you want to call it is not a problem for your helicopter, but it is a problem for all helicopter pilots. It will not cause any damage to the helicopter. The only problem is the noise complaints that you can get by repeatedly flying over the same people and making noise like this. HAI ( Helicopter Association International http://www.rotor.com/ ) has sponsored the Fly Neighborly program which talks about ways to fly to reduce the noice impact of your flying so we can hopefully enjoy this passion called helicopters throughout our lives. Steve |
#7
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When you do an auto rotation from a power on cruse condition you drop
the collective and at THE SAME TIME move the cyclic back and to the right to reload the rotor system for the new rotor airflow condition. If you do the transition correctly you NEVER unload the rotor system. If you do NOT move the cyclic when you drop the collective then yes you will unload the rotor and you will loose rotor RPM rapidly because the airflow has to flow up through the rotor in an auto rotation and it will not do this until the rotor is tilted back to allow this. The coning may flop around some during the power to auto transition but when a steady auto is established the cone angle is very nearly the same as at hover because the horizonal and vertical forces on the blades are almost the same. There is some difference in where the center of lift is verses span distance on the blades between an auto and powered flight but this also varies with the amount of twist built into the blades. John On 2 Mar 2004 05:30:47 -0800, (Eric D) wrote: If you start a descent from cruse by reducing pitch and maintaining rotor speed, what happens to coning forces as compared to cruse? I have noticed that during a decent in a R22 that you can get a "Wop-Wop" noise from the main rotor blades. Changing cyclic or increasing rotor speed a very small amount can make it go away, or at least not heard from the cockpit. Can someone explain what is occurring and why? Thanks, Eric D |
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