Originally Posted by
Grebe
And If I recall correctly re an interesting offsite conversation in the late 90's- after the time of the MDC buyout and salting the aero group with a few MDC types, there was a major push to incorporate the inboard trailing edge wedge supposedly used on the MD-11 to attempt to meet DC-11 range guarantees. About that time Aviationpartners suggested an early version of winglets and was met with bucu skeptisim- but eventually some test fights were done on a BBJ under the guise of making the BBJ at least look different than the old 737 ( executives like the deluxe hubcaps to show their importance ) provided the winglets did not cause problems. The test results compared to the 'wedge' showed a definite improvement such that ( as I recall ) a german airline ordered a few that way, and the fuel savings on relatively short flights along with takeoff performance was significant.. And the rest is history
In around 97 a B747 Classic was flown with a DTE of a design similar to Uncle Bobs work on the MD-11, at the request of the original 747 Chief Engineer, bless his soul. It was reportedly effective, and was canned, much to the annoyance of Joe S.
I've flown a B737 Classic with a DTE type device, (which was pretty mild, was looking at other items) and it was interesting, the same flow structure that exists at high AOA with a Gurney Tab is what occurs in the DTE case at low angles of attack and high Mach. The same device on a Lear was effective as one would expect. The basic aero that was applied to the MD twice was not bad, but there is more that could be done, in fact Airbus went further with their work than TBC did once they cut DAC out of the herd (or were taken over depending on your point of view) some really good work was done on an A330 by the busmen. The A320, 330, 340, 380s have always utilised blunt TE's and their wings have been effective. The bus subscribes more towards the Whitcomb notion of a SC-2 style wing section than TBC has ever done, they avoid the issues of high LE suction. The wing may not look pretty at first glance but the airbus offering is remarkably efficient IMHO. Grows on you like fungus. The most interesting thing is that none of them work as advertised, a supercritical section should have any normal shock well aft on the upper surface in transonic conditions, no one operates any of them fully subsonic, there is a shock on a 767, 747, 777, 787, 320, 330 340 380 wing in cruise, and a good one on the NG... One of the most stable shocks in cruise is off of the MD80, and it is almost where it is supposed to be for the old blender (having thirsty engines doesn't help though)
A DTE analogue was flown on my helicopter, and that was probably the most remarkable flight series I ever did. The impact of that is a subject all by its own, doing it safely takes more time and money than I had to justify on it at the time, but the stall Nr went from 82% to 68%, and the simple greatest impact was that instead of running out of pedal as the rotor stalled out, (dont try that at home) a pedal turn could be done against the torque. Do the maths to work out what the difference in applied torque is, 68^2/82^2 is the comparable Cl of the TRB, and the difference is sufficient authority to enjoy turns up to the stall. The rotor Nr was optically measured and also matched the timing N1 of the engine. If I had a fenestron, I would have taken that further, but the copter had a delicate TRB root which was not confidence inspiring. My opinion is that there is more to be done on the TE than is gained at the LE, for props, rotors, fan blades, etc. (actually, those were all tried with some fun).