Shortfinals – aviation and more!

By: shortfinals

Nov 04 2010

Tags: 'Aerodynamics of Propulsion', aircraft, airframe, airliner, American, American Airlines, anti-shock bodies, area rule, Aviation, blended winglet, Boeing 757-200, Boston, Chicago, Columbus, control surfaces, controls, Convair, cylindrical, Dr Dietrich Kuchemann, drag, engineer, England, F-102A, fairings, fighter, flap-track covers, flaps, flight level, flying, fuel consumption, Gatwick, JFK, Kuchemann carrots, leading edge, Mach, Manchester, New England, New York, Newark, Oneworld Alliance, Philadephia, prototype, Richard T Whitcomb, stalling speed, trailing edge, vortex, vortex generators, vortices, wing, wing structure, YF-102

Category: aircraft, Aviation, England, Great Britain, New England, New York

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I suppose that you could say that I am a seasoned transAtlantic traveller. Over the years, I have tried many routes to and fro, (out of Philadelphia, Chicago, Newark, Columbus, New York, Toronto, Boston, etc) usually involving Heathrow, Gatwick or Manchester at the U.K. ‘end’ of things. You might expect that, given my involvement with aviation, I would be a little blasé about the whole thing. Nothing could be further from the truth. I am still passionate about every aspect of flying, and fully intend to remain so!

In the summer of 2009, American Airlines began to offer a daily JFK to Manchester, U.K. service using some of their Boeing 757-200 fleet, which had been configured into a mixed class arrangement (16 ‘lie-flat’  business class, 166 economy).  Since Manchester is only 45 minutes away from the area where some of my family live, this is as good a destination as any, particularly when you consider the difficulties of making a swift ‘get-away’ from Heathrow!

This year I had to make a rather sad trip, at short notice, due to not one but two bereavements. Consequently, I spent only five days in Britain, and devoted as much time as I could to family matters.

Here we are, headed back to New York, on board flight AA211. Cruising at around FL320, you can see the continuous cloud sheet, far below us. This is a good example of the complex wing structure of a modern airliner. The blended winglet (tastefully adorned with the AA logo, as part of the ‘Oneworld Alliance’ of airlines) considerably reduces the drag caused by wingtip vortices, and thereby decreases fuel consumption.  Looking towards the leading edge of the wing, you can just make out the small vortex generators. Wait a minute, didn’t I just say that vortices were bad? They are, in the wrong place! Small leading edge vortex generators modify the ‘boundary layer’ of air flowing immediately next to the wing, making it ‘cling’ to the surface better, and improve the effectiveness of trailing edge controls as well as lowering the stalling speed of the aircraft (amongst other things). Behind the trailing edge of the wing  you can see the flap-track covers. These cover the mechanisms for extending and retracting the flaps, it is true, but they also serve another vital function. Most airliners cruise in the subsonic range between Mach 0.8 and Mach 0.85; at these speeds it is better if the airframe obeys the ‘Area Rule’, where there is a smooth change of cross-sectional area along the length of the airframe. This was devised by a brilliant American engineer, Richard T Whitcomb. You can see this, in a rather exaggerated form, by looking at fuselage of the original ConvairYF-102 fighter, with its cylindrical shape, and the production F-102A. The Area Rule when applied to the rather disappointing prototype YF-102 caused an increase in top speed of 25%. Similarly, if anti-shock bodies, like the flap-track fairings, are placed behind the wing, they also act to reduce drag and decrease fuel consumption. These fairings are sometimes known as ‘Küchemann Carrots’, after the superb engineer Dr Dietrich Küchemann, the author of  the classic work ‘Aerodynamics of Propulsion’, who drew up the design rule for these bodies.

Oh, and the flight? Smooth as you could wish for……………

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