"Area Rule"

Area rule or Witcombs rule is a factor in aircraft design. Sometimes called the "Coke bottle shape" or "Wasp waist", the fuselage is pinched in at the center part.

John Whitcombs theory that the smoother the shape if an object, the less resistance to drag. A fuselage shaped like a bullet has less drag, but put wings on it and it increases drag. To modify the shape and reduce the cross section where the wings attatch would result in less drag, better wind flow and more speed.

A prime example is the F-102. The fuselage was shaped like a bullet with delta wings but the aircraft would not go supersonic. Using Whitcombs rule, the team redesigned the aircraft resulting in a longer fuselage, pinched in at the center. They also added rear contoures to help even out the air flow. As a result the aircraft then could break the speed of sound.

It is now an accepted fact that Witcombs Rule, now called "Witcombs Law of Aerodynamics and Area Rule", and is tought at schools dealing with mechanical and aeronautical subjects.

Thanks Berny
deleted mine since it was so far off

QUOTE: Originally posted by wibhi2 deleted mine since it was so far off

How do you know I have the correct response? I might be throwing a lot of technical mumbo jumbo sounding stuff out their, trying to BS my way through. Though the answer is correct (or is it?). In a way the full correct answer does have something to do with wing cord, shape and overall SQ. FT. of the wing, but I tried to keep it simple and not use too much technical words or language. The simple answer is the Coke bottle shape fuselage. How to get to that stage is very technical.

you could be blowing snow up the dark side of the moon but it sounded right while I was trying to jogg my memory (head against brick wall method -:0p )

Berny is indeed correct in his (or her?) assertion.

Dr Richard Whitcombe was an aerodynamicist at NACA in the 1950s, researching the cause of the sudden increase in drag, on an aircraft as it approaches the speed of sound (The transonic region - Mach 0.7 - Mach 1.5).

It was found that this drag was due to the formation of shock waves in local regions of supersonic flow over the airframe.

Whitcombe discovered that this kind of drag (termed Transonic or Wave Drag) was highly dependant on changes in the cross sectional area of an aircraft.

By subtly shaping the fuselage on the portion of the airframe where the wings are attached (waisting) the peak transonic drag rise could be reduced. Less drag for the same amount of thrust resulted in the aircraft breaking the speed of sound.

The F102 is the classic example in the USA, but also take time to look at the shape of the Blackburn Buccaneer in the UK.

In England, Professor Dietrich Kuchemann approached the same problem from a different angle and his research led to the characteristic 'Kuchemann carrot' aerodynamic fairings later found on the wings of the Handley Page Victor.

Whitcombes work later helped the development of the Super Critical Wing, but that as they say, is another story altogether!

I can recommend an excellent book called A History of Aerodynamics by John D. Anderson Jr for further reading.

Cheers,

Rob M.

WOW!! You guys got it goin on!!

ooohhh..... wow... I am a freshman majoring in aerospace engineering.... I guess I would be studying these stuff in school!