Over wing missiles

[DrTre]

I'm sure I remember seeing a Lightning with missiles on top of the wing at the imperial war museum when I was a kid.

Googling a bit shows I wasn't mistaken but I'm wondering why it hasn't been adopted more?

Aerodynamics or simply down to the fact it must be easier to arm the aircraft with the hard points on the under side of the wing?

[Boatbuoy]

I can't help with your question as to why, but the SEPECAT Jaguar could also carry missiles above the wing.

[slybynight]

In the lightning's case, I think its Fuel Tanks

[arch stant0n]

I'm no aerodynamics expert - but you really don't want to slow air down over the top of the wing...faster airflow above the wing than below is what keeps you flying!

[TartanPaint]

arch stant0n said:

I'm no aerodynamics expert

You can say that again!

Angle of attack keeps you flying, no matter what the school textbooks say.

EDIT: Sorry, that reads like a knobhead comment. Being less of a smart-arse about it, the speed of air over and under the wings thing is a very common misconception, which is stated as fact in many, many textbooks. It's total nonsense.

Wings do not generate lift from the difference in speed over the top and bottom surfaces and this has nothing to do with the shape of the wing either. Otherwise inverted flight would be impossible. Angle of attack is the key. You can play with this effect by sticking your hand out the window of a moving car. Tilt the leading edge of your hand upwards and you'll feel a force on the underside of your hand lifting it. Tilt it downwards and your hand will be forced down. The faster you're moving, the less this angle has to be to have the same effect. So, forward thrust also keeps you flying. No angle of attack will matter if you've got no airspeed.

Edited by TartanPaint on Friday 15th January 09:54

[Evanivitch]

Probably a massive combination of safety, ease of maintenance, aerodynamics, structural, RCS, weapons integration and it's just not sexy.

So my answer, not a clue.

[R8VXF]

I would have thought under wing would be safer for launching as the missile can drop away from the wing before firing.

[DrTre]

Thanks very much for the answers!

Actually, I should probably have reversed my question and asked what advantages it might have.

As has been comprehensively pointed out, there are a stack load of disadvantages so it's kinda weird that it was attempted at all. Engineering curiosity?!

[Evanivitch]

Having done a quick Google, it seems they were simply a convenient location for lightweight heat-seeking missiles, whilst allowing the Jaguar to store AtG weapons on the main hardpoints. There were few benefits, like better visibility of the seeker head, but possibly little else.

[NM62]

slybynight said:

In the lightning's case, I think its Fuel Tanks

Found this picture of a Saudi One Linky

[DrTre]

Cheers for the clarification on the lightning, as a kid I guess I saw missile shaped things and put two and two together and came up with 7.

And thank you evanovitch for the info

[Maikeeh]

TartanPaint said:

Wings do not generate lift from the difference in speed over the top and bottom surfaces

Edited by TartanPaint on Friday 15th January 09:54

Yes they do. The difference in speeds is what causes the pressure differential! Lower pressure on the upper surface and higher pressure on the lower surface gives a net upward force - lift. The textbook misconception you're referring to is the equal transit time fallacy that states that the flow over the top of the wing has to travel further and therefore faster than that over the bottom. This is nonsense since the flow does not have to 'meet up' at the wing's trailing edge.

You're right that angle of attack is important. AoA is the reason why the speeds are different; it causes the streamlines to 'bunch up', leading to the velocity and pressure changes already mentioned. But even at 0 degrees AoA a wing can still generate lift, provided that it has camber. A cambered wing introduces a shape change in to the flow which has the same 'bunching' streamline effect.

[kowalski655]

Also perhaps as the Lightning had a very swept wing,so not much forward facing area,and the Jaguar had a small wing ,perhaps they used the top for extra space,not needed on planes with bigger wings. but I have no real idea

[FourWheelDrift]

Overwing rocket pods on the F.53 exported to Kuwait & Saudi Arabia

Edited by FourWheelDrift on Friday 15th January 14:14

[DrTre]

That photo shows the real reason why it makes sense to mount them on top of the wing. They just fall off the underside.

[R8VXF]

DrTre said:

That photo shows the real reason why it makes sense to mount them on top of the wing. They just fall off the underside.

Ignore the tin foil hattery of the video title, missiles are designed to fall away before igniting:
https://www.youtube.com/watch?v=9DYsYKFNSHo

[NDT]

Maikeeh said:

TartanPaint said:

Wings do not generate lift from the difference in speed over the top and bottom surfaces

Edited by TartanPaint on Friday 15th January 09:54

Yes they do. The difference in speeds is what causes the pressure differential! Lower pressure on the upper surface and higher pressure on the lower surface gives a net upward force - lift. The textbook misconception you're referring to is the equal transit time fallacy that states that the flow over the top of the wing has to travel further and therefore faster than that over the bottom. This is nonsense since the flow does not have to 'meet up' at the wing's trailing edge.

You're right that angle of attack is important. AoA is the reason why the speeds are different; it causes the streamlines to 'bunch up', leading to the velocity and pressure changes already mentioned. But even at 0 degrees AoA a wing can still generate lift, provided that it has camber. A cambered wing introduces a shape change in to the flow which has the same 'bunching' streamline effect.

Really - what you're both saying directly contradicts what I learnt in fluids in an Engineering degree.
Prepared to be wrong... but aren't the facts:
- an 'normal' wing profile will generate lift at 0 AoA - due to the difference in fluid speed top to bottom, generated by the longer path of the fluid over the top of the profile
- The longer over the top comes mainly from the shape of the profile (not really from AoA)
- AoA will generate lift even if there's no profile to the thing going through the profile

Someone can come along and talk about Coanda vs Bernoulli - both of which are all about shape of flow not AoA

[Eric Mc]

The main reason why the Lightning had hard points for the top of the wing is because there was little space under the wing for conventional pylons. The main wheel bays on the Lightning took up a large part of the lower wing.

[NM62]

I'm no expert and was told many years ago when in the ATC (circa 1973 - 74) that the Lift was generated due to pressure differences above and below the wing.

Above the air moved faster due to the shape and reduced the pressure, below and the air was slower causing higher pressure, the difference resulted in lift.

Found this which was quite informative and aimed at my level of understanding ( i.e. not degree level ) NASA's Explanation

[tight5]

R8VXF said:

missiles are designed to fall away before igniting

Looks like some don't -

Edited by tight5 on Wednesday 20th January 21:52