Where is G-LYNX?

Discussion in 'Aviation' started by Ralf, May 29, 2009.

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  1. After all the Bashing of our own museum I decided to treat my Ralfets to a day out at the helicopter Museum(W-S-M) and show them the fastest Helicopter in the World.........!

    How hacked off was I to pay £15.50 for the Ralf Clan and be disappointed in what was on offer.

    Was I expecting too much?

    I was most p!ssed off to find G-LYNX has sped off once again.

    Anybody know of it's where-about's or has it been bought by some MP as a Kiddies Climbing frame at public expence!

    Regards,

    Unhappy Ralfets :x
     
  2. Dunno. It was there in 2006 when we used the place as a FARP!

    It's probably been Christmas Tree'd :)
     
  3. Did the museum staff not have the information at the time?

    RD
     
  4. The old Doris at the door did'nt know what Military discount was when paying and when asked about the where-abouts of G-LYNX she said "there are lots of Helicopters in the building next door my love".
    Bless her, she's not got long on this earth! :(
     
  5. G-LYNX is still at WSM as far as I know.

    [​IMG]


    G-LYNX was actually used by several airframes over the years and not just the famous speed record runs. It's even been a Wheelybin;

    [​IMG]

    Its a sort of 'personalised reg' for Westland. The reg was carried by essentially the same airframe but it's been in different guises over the years.
     
  6. After the cancellation of RIAT last year me & the boys made a bolthole to WSM on the Sunday Morning & the Musuem in the afternoon. A wee bit dissapointed & definately no G-Lynx World Record Holder on display. Some of the Airframes were interesting though. The FAA Museum the next day was excellent.

    Flashy you can answer this. How come that the Lynx record (1976??) has never been beaten. With advances in Carbon Fibre technology and Engine Power it seems strange that this record has remained unbeaten in 33yrs.

    Have not Googled it but I think it was 176mph in 1976.

    Could some provide a simplistic answer please ?
     
  7. I could answer it but it may take a while and you would need at least a basic comprehension of helicopter aerodynamics.

    I'll be brief. The Lynx holds the record for a conventional helicopter (one that has a main rotor disc and a anti torque tail rotor). In that config, you aint going to get much faster regardless of materials or engine power. The issues are as follows;

    Advancing and retreating blade speeds. If you picture a single blade on the disc and think about its path as it travels around its orbit. In the hover (with no wind), the velocity on that blade is pretty much the same as it travels from lets say the 3 o'clock position (viewed from above) all the way round back to the 3 o'clock position. If you now make the aircraft go forward, you are introducing a positive velocity. when the blade is in the 3 o'clock position now, it has not only its rotational velocity but also the forward airspeed velocity going over it. As that blade travels past the 12 o'clock and towards the 9 o'clock, it would be sensible to assume the blade now has its rotational velocity minus the forward airspeed going over it. So, you now have a difference of velocity across the disc. This in turn should give you a difference of lift across the disc. Of course, you'll be more than aware of the lift formula? Lift = CL (1/2) ρ v2 S. Increase any of the values and you get an increase in lift. We've seen that we've got as higher velocity in the 3 o'clock position. In normal flight speed regimes, this is called Dissymmetry of Lift. This is 'cured' by ensuring the advancing blade has a reduced pitch angle thus reducing its lift and conversly, the retreating blade gets a mechanical increase of pitch. With me so far?

    So, we have our advancing blade. Lets give the disc a few random values. Lets say the disc is spinning at 400 rpm and that give the actual velocity at some arbitrary point along the blade a speed of 400 knots (the tip has the highest velocity). So, even sat in the hover with no wind, the blade is whooshing through the air at 400 knots (460mph or Mach 0.62). If we now move the helicopter through the air at say, 160 knots, this means the advancing blade will have a velocity of 560 knots (Mach 0.86) and the retreating blade (the one at the 9 o'clock) will have a V of 240 knots. If we now move the heli even faster and go 200 knots, advancing blade has a V of 600 knots (Mach 0.93). The mach number is critical. Ie, the speed of sound. G-LYNX flew at 249.13 mph (216 knots/Mach 0.335) but the advancing blade would have been at a velocity somewhere near Mach 0.95 which is right in the transonic range. This is where the amount of pressure in front of the aerofoil is extremely high and the air flow starts to break up if that aerofoil isn't specifically designed for it. That in turn causes critical failures within the structure. G-LYNX has BERP I tips fitted which helped to reduce this onsetting V crit number but only by a little bit and by just enough to cheat ripping the blade tips off.

    Lets think about the velocity that the retreating blade has at that forward speed. So, disc V is 400 knots, Heli airspeed is 200 knots, the retreating blade will have a velocity of only 200 knots. You've now got a velocity difference of 400 knots across the disc. Refer back to the lift formula and remember we needed to increase the pitch on the retreating, slower blade. As with a fixed wing, you get to a point where the blade stalls if the AoA is too high and the velocity is too low. The stall spreads from the blade root to the blade tip (the root of the blade has the lowest velocity).#

    So, lets just think about whats going on across the whole disc in high speed flight. On the advancing side, your tips are at V crit and on the Mach bubble at very very high velocity. The retreating side is almost if not already stalled and has a velocity difference of at least 400 knots across them (think about that. Lynx rotor diameter is 42ft and youve got a massive speed difference in a very small area).

    So in answer to your question, we've pretty much reached the max speed a conventional helicpoter can fly. Not much to do with engines (although drag increases by a value squared to each knot you need) or materials used (although strength and the ability to make thinner aerofoils has helped) but more to do with pesky aerodynamics. :D

    Hope this helps ;)
     
  8. I almost understood that - ever thought of becoming an instructor?
     

  9. :D :D
     
  10. I was with him until "Advancing........" then it got a bit technical for me.
     
  11. Of course we all are 8O
     
  12. Flashy you have given me an Ice Cream Headache & a bit of a mind melt but get your physics drift. Am down in Bessbrook tommorow & will be posting photos of how it looks now.

    Many thanks indeed F

    K
     
  13. Thanks Flash. A concise explanation.
     
  14. Concise but dull, hence Flash never getting laid.

    Big gay Scalextric playing, Connect four league finalist, list making, soduko playing, compendium owning nintendo virgin!