Airfoils -w- Intakes in Wing

[Jane-DoH]

I'm wondering about if an aircraft with an intake mounted in the wing requires re-contouring of the upper and lower surfaces as there is no traditional leading-edge in the area where the intake is located (except I suppose the lips of the intake). One example that sticks to mind is the De Havilland Mosquito, though it's a military aircraft my question is a purely aerodynamic one: Early models had a traditional leading-edge inboard; later models had an intake of some sort in the leading-edge. I'm wondering if the lack of a traditional leading-edge inboard required the upper and lower wing-surfaces to be re-contoured.

[barit1]

Requires is sorta a strong word. As with so many things in life, the answer is "It all depends".

There are plenty of examples both with and without recontouring. The B-17 for one - fixed slots outboard for handling qualities, inboard LE scoops (oil coolers?) all without any obvious recontouring. But it was a pretty slow aeroplane, with many draggy protuberances.

It may be that if there's a top speed or specific range shortfall, recontouring may provide the extra efficiency to meet the spec.

[FE Hoppy]

Vulcan
Victor
Comet.

All worked pretty well. :ok:

[lomapaseo]

I probably don't understand the question, but what do you feel would cause any significant effect on a wing because of an intake?

If the air is free to pass through the intake than the effect should be minimal perhaps with some increase in drag.

If it's a concern about lift one could always design the intake non-symetrical to create lift.

[awblain]

I understand that the leading-edge intakes inboard of the engines on a mosquito are the engine radiators, and that this location reduced drag compared with building a nacelle to hang radiators off the engine pods.

[barit1]

There's another issue - and using the Mossie example:

For low-speed handling properties, it is desirable that the inboard wing region stall prior to the outboard. I'd think the contouring of the coolant inlets was influenced by this issue as much or more than by highspeed drag.

Perhaps someone with firsthand experience can expand on this.

[TURIN]

Found this here...Aerodynamics and flight dynamics of turbojet aircraft
(http://www.craftsmanspace.com/free-books/aerodynamics-and-flight-dynamics-of-turbojet-aircraft.html)

BY T. I. LIGUM

Transport Press, Moscow, 1967




Engine installation in wings. When the engines are installed in the wing (between the upper and lower plankings), the total drag is reduced. In practice, however, the engine is fastened to the fiiselage (in double engine aircraft), while the air duct extends along the chord in the wing. This leads to a decrease in thrust as a result of a pressure loss in the duct, but in contrast an advantage is the almost "clear" wing (without secondary structures) which results. Engines arranged in this manner (close to the aircraft axis), if one of them fails this creates only a slight turning moment.

Of the disadvantages which result from this arrangement, let us point out the fact that it becomes impossible to make use of the thrust reversal due to the heat effects of the gas jet on the fuselage (for a double-engine aircraft) and the partial use of thrust reversal (for a four-engine arrangement) (see Chapter IX). The stream of exhaust gases creates substantial noise in the tail section of the fuselage and causes discomfort to the passengers seated in the rear. On the Tu-104 and the Tu-124 (Figure 57), the engines are located in the base of the wing, so that the greater part of the engine pod is hidden behind the wing. In the De Havilland Comet, however, the engines are fully-hidden in the wing (Figure 58). The engine's small size makes it possible to design its pods with quite small maximum cross-sections.

Engines located at the base of the wing create positive interference at the most complex aerodynamic point the joint between the low-hung wing and the fuselage. The effect of the Jetstream causes the formation of an "active fairing" here, i.e., an increase in the "regeneration" of the surrounding flow. This leads to a decrease in drag for the aircraft as a whole.

However, this engine arrangement requires an increase in the relative thickness of the airfoil profile, which causes a decrease in the aircraft's high-speed characteristics. The angle at which the engines are installed relative to the longitudinal axis is 3-5° in this arrangement. This inclination is necessary to guarantee that the engine exhaust flow does not hit the elevator unit.



It may help.

[Jane-DoH]

TURIN

Engines located at the base of the wing create positive interference at the most complex aerodynamic point the joint between the low-hung wing and the fuselage.

What's positive interference and negative interference?

The effect of the Jetstream causes the formation of an "active fairing" here, i.e., an increase in the "regeneration" of the surrounding flow.

What is an active fairing?

However, this engine arrangement requires an increase in the relative thickness of the airfoil profile, which causes a decrease in the aircraft's high-speed characteristics.

So the wing does behave thicker even if the lips are thinner than the other portions of the wing?