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Thread: Who Likes Aircraft?

  1. #111
    Join Date: Sep 2014

    Location: Northern Ireland

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    I'm John.

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    Quote Originally Posted by walpurgis View Post
    The Blackbird was unofficially flown to speeds approaching 3000 mph. Still not as quick as the amazing X-15 though. That was capable of over 4500 mph, but that used pure rocket power, not jets.



    Just noticed this picture is a mirror image. The logo on the tail should say NASA!
    Very interesting Geoff. Just read the Wikipedia page. Had an ejector seat you could use at Mach 4! All the best with that

  2. #112
    Join Date: Feb 2017

    Location: Sussex

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    I'm Simon.

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    Concorde and interesting stuff.

    There is a video on you tube interviewing ex Concorde captain John Hutchinson. I watched it and learnt some new stuff about Concorde adding to my own knowledge as an aviation enthusiast myself, which I think is fascinating.

    Firstly when Concorde got up to mach 1 the shock wave created by breaking the sound barrier pushed the centre of lift back down the wing. Quite how that happens by the shock wave I'm not sure, but it's probably due to the physical force it exerts on the normal point on the wing where the lift is generated, which is what the centre of lift is. Much akin to being able to blow the force of bass out of a speaker if you have a powerful fan. Lift is of course generated by the static pressure differences exerted on the upper and lower sections of the wing by Bernoulli's principle. This is basically because of the shape of a wing or aerofoil. As the top surface is curved, air moves faster and it exerts a lower static pressure relative to the lower surface where the static pressure is relatively higher. This difference in pressure creates upwards lift from a wing. Static pressure is the force on a surface by molecules in air, so if you hold a piece of paper out in front of you and blow on its top surface you effectively reduce the chance of those molecules having a static pressure effect because they are moved away. The paper will move up. Bernoullis principle in action.

    But back to Concorde because this shock wave, which is often seen as condensed air separating around the nose of a supersonic aircraft and forming a ring, meant fuel has to be pumped backwards at supersonic speeds. The centre of lift was, according to Hutchinson around 8 feet rearward of its normal position at supersonic speeds. Because the centre of lift is rearward, but centre of gravity remains at the same more forward point, the fuel in concordes front tanks had to be pumped rearward to stop the aircraft pitching down as nose heavy weight is not balanced with the centre of lift moving back. When Concorde got to sub sonic speeds the fuel had to be pumped back forward, but of course as the aircraft went from Mach 1 to Mach 2 (about 1350mph) more and more fuel would be pumped back.

    Also interesting is that concordes wing which uses elevons (ailerons and elevators in one) managed to create lift on landing by its high angle of attack relative to the airflow. So when we used to watch it come in with its nose high (that's why it needed the drop nose incidentally) it was this high angle of attack creating lift. In landing at high angles of attack, air on the upper surface of concordes wing was slowed because of its high angle presentation to the airflow, meaning air has to travel a longer distance up and around the top surface, compared to under it. But not only that but the wing was designed to set up swirling vortices on its upper surface at this high angle of attack which further created lower pressure and slowed air on the top surface. According to Hutchinson this was finely balanced in Concorde on landing and it was only just about sufficient lift to enable it to land safely, but speeds no doubt would have really been rightly controllled on landing to prevent a stall. But concordes wing could not generate lift coming in flat to land like a conventional airliner and also on take off the same principle that the wing was not at an angle to the airflow, apparently meant that concordes speed on the ground could be exceptionally high and it would not take off by itself like a 737/747 etc could and some other light aircraft. Only on adding in up elevator (or elevon) during the take off role and by presenting the wing to the airflow at an angle of attack would Concorde take off. But at much higher speeds it could fly flat due to the speeds involved.

    But the way Concorde used its engine ramp intakes is even more interesting as it enabled this aircraft to slow down the air into a conventional jet engine from 1350mph to around 300-400 mph in around 8 feet. A conventional Olympus jet engine which Concorde used cannot process supersonic air, so these double ramps on the intakes set up another shock wave to slow this air down. That's fascinating too, as if concordes ramps did not do this, the Concorde project would have been over. It's ability too to not need afterburner or reheats (pumping neat fuel into the engine nozzles and letting them effectively act like a rocket) past Mach 1, meant it could do what's called 'super cruise' i.e. Fly supersonic without burning reheat fuel. This added to concordes range as it would have been limited with using huge amounts of fuel by reheat, in excess of Mach 1. But apparently there is no jet fighter aircraft that actually can fly past Mach 1 without reheat, even when you consider latest aircraft made. And Concorde was a 1960's project not even designed on computers.

    The other thing I didn't know was Concorde used rollers under its floor to aid the expansion of the aircraft as it reached supersonic speeds.

    I can understand the commercial pressure that stopped this aircraft flying and airbus stopping support for it, which basically meant nobody could service it, but haven't we gone back in time taking it out of service. It's now 14 years since it last flew. I just can't believe that we have taken a backwards step for aviation when you consider also the airframes were all young in landing cycle terms. Bring it back!

  3. #113
    Join Date: Oct 2012

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    I'm Alan.

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    Quote Originally Posted by Dynamics View Post
    As the top surface is curved, air moves faster ....
    The air does NOT move faster on the top surface of an aerofoil wing.
    This is a total fallacy that has been promulgated by its re-telling.

    There is absolutely no reason that the air must recombine at the trailing edge at the same time.

  4. #114
    Join Date: Feb 2017

    Location: Sussex

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    I'm Simon.

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    Air has the same fluid motion as water around an aero foil in water. How do you account the differences in static pressure that account lift. Newtons laws is the only other explanation. But how do you reach your view ?

  5. #115
    Join Date: Feb 2013

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    I'm Grant.

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    Quote Originally Posted by Firebottle View Post
    The air does NOT move faster on the top surface of an aerofoil wing.
    This is a total fallacy that has been promulgated by its re-telling.

    There is absolutely no reason that the air must recombine at the trailing edge at the same time.
    True... Think its to do with low pressure atop and higher pressure below and its the curved shape that causes it
    Regards,
    Grant ....

    I've said it before and I'll say it again: democracy simply-doesn't-work
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  6. #116
    Join Date: Feb 2017

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    But with respect that misses the issue of the effects of static pressure and Bernoullis principle which equally applies to water and air. Bernoulli theory remember is that the faster a body of air over a surface the less static pressure that can be applied or exerted . That's what made Concorde so good because the pressure differences were applied by high angle of attack.

  7. #117
    Join Date: Feb 2013

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    I'm Grant.

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    Dont think it always does. Yes there are more than one way of looking at things re him and newton
    Last edited by struth; 21-04-2017 at 21:57.
    Regards,
    Grant ....

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    DENON DV2900 - TWIN PRO MONOBLOCK AMPLIFIERS - XIANG SHENG DAC\PRE\HEADPHONE AMP - AVANTREE OASIS CLASS 1 BLUETOOTH - AUDIO TECHNICA ATH-MSR7 & OPPO PM-3 PLANAR HEADPHONES - WIN10 JRIVER23, DEEZER HiFi - ECHO DOT - SMSL M6 MINIDAC - FULL RANGE TWIN TELEFUNKEN's - Q ACOUSTIC BT3 actives - CANTON SUB - MAINS REGENERATED AND FILTERED.

  8. #118
    Join Date: Apr 2012

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    I'm Geoff.

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    I was going to go on about venturi effects, but I can't be bothered.
    Mr. Tact!

    Main system: MMs/ADCs/Low output MC's/One rare Japanese SUT/One scarce British phono stage/various tonearms/hefty Japanese DD TT and hefty Japanese BD TT and small British BD TT. 4 CD players/2 jitter buster/2 DACs/Valve buffer. TVC stepped attenuator or valve pre-amp or solid state pre-amp. Current dumping power-amp or either of two Class A SS power-amp or Class A EL34 valve monos or big Japanese (part Class A) integrated. Big dual concentric speakers/Smaller dual concentric speakers/Two way British compacts and full range speakers, amongst others. And too much more to list!

  9. #119
    Join Date: Oct 2012

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    I'm Alan.

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    Quote Originally Posted by Dynamics View Post
    But how do you reach your view ?
    It's been proven by wind tunnel tests, with very clear diagrammatic evidence.
    If I could remember where I saw I would post a link.

  10. #120
    Join Date: May 2012

    Location: Toulouse

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    I'm GettingFunky.

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    Quote Originally Posted by Dynamics View Post
    I can understand the commercial pressure that stopped this aircraft flying and airbus stopping support for it, which basically meant nobody could service it, but haven't we gone back in time taking it out of service. It's now 14 years since it last flew. I just can't believe that we have taken a backwards step for aviation when you consider also the airframes were all young in landing cycle terms. Bring it back!
    In the current era, it is all about reducing costs and the ecological impact of aircraft.
    Having something powered by four Olympus engines travelling at Mach 2 just does not fit not this way of thinking.
    Keeping the older technology going with the amount of obsolescence would also be a significant challenge.
    Kevin

    Funkified Technics SL1200 Mk2 (Funk FX-1200+, Techne-Audio modified DL-103/AT33PTG/II/, Funk Firm "Strata" platter, "Spin" bearing and BO!NG Isolation feet, MCRU/LDA PSU).
    Pioneer PD-S703.
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