Overwing pylons

[Nigel Bunker]

Now I know we British used them on the Lightning (for fuel tanks) and the Jaguar (for Sidewinders & Matra Magic AAMs) but have any other planes been fitted with them?

[trickydicky210]

I believe the Irish Airforce used them, but stopped using them when they realised they made holes in the wing when the bombs were released!!

[Giorgio N]

I may have seen studies and proposals with overwing pylons, but the only production aircrafts I remember are the Lightning and the Jaguar.

Makes sense after all, overwing pylons are not the best option at all (this is being polite) and on the two types mentioned were used only because the designer had no other place to fit a pylon without extensive and expensive modifications to other parts. Had the need for these pylons been identified earlier in the design phase, they'd have likely been located somewhere else

However I've seen an example of overwing engines, the German VFW-614

[pigsty]

overwing pylons are not the best option at all (this is being polite)

I can see there would be a problem if you needed to jettison whatever was on the pylon. But if you're launching something that leaves under its own power, or not letting go at all, is it that bad?

[Test Graham]

Overwing pylons are draggier than underwing ones, partly because they exist in a faster airflow and partly because anything that interferes with the upper wing airflow is generally a bad thing - unless the flow is so poor anyway that fixes such as fences, notches or vortex generators are required.

[Giorgio N]

I can see there would be a problem if you needed to jettison whatever was on the pylon. But if you're launching something that leaves under its own power, or not letting go at all, is it that bad?

It's not only a matter of load separation, although this is indeed a problem and overwing pylons can't carry everything: Sidewinders are fine as they leave the pylon under the thrust of their motor, other missiles are dropped first and then the motor ignites, so these can not be launched from overwing pylons. Ferry tanks like the Lightning's are fine as they are not going to be jettisoned, fuel tanks that need jettisoning before combat are less so. Rocket launchers would be fine, and the Matra tank/launcher combo was indeed proposed on the Lightning.

The main issue however is that in general anything over the wing is going to disturb the flow where it's best left alone and for this reason overwing pylons are not ideal.

Access is also more difficult than with a conventional underwing pylon. Not too much of a problem with a lightweight Sidewinder or Magic missile and not too much with a seldom used tank (Lightning again), but really the aerodynamics reasons are the most important

[Selwyn]

I can see there would be a problem if you needed to jettison whatever was on the pylon. But if you're launching something that leaves under its own power, or not letting go at all, is it that bad?

Underwing stores don't leave under their own power. They are blown off using cartridges!

Selwyn

[Rob P]

And from the picture in the link below, I figure overwing pylons are awkward to load?

http://www.bharat-rakshak.com/IAF/Images/1180-3/Jaguar20.jpg

[Max Headroom]

I always wondered why the Jaguar wasn't designed with wing tip pylons for AAM's.

Trevor

[upnorth]

However I've seen an example of overwing engines, the German VFW-614

That's a feature that Honda seems to have revived in their Honda jet.

[Magpie22]

Underwing stores don't leave under their own power. They are blown off using cartridges!

Selwyn

Normally this is the case but there is normally a design requirement that stores, (and sometimes the racks and pylons), must be capable of departing the aircraft, assisted by gravity alone, in case of failure of the normal forced-release mechanism. This requirement can be met over a limited speed and attitude range and not the full envelope required for normal release.

Magpie 22

[squezzer]

Aircraft fly mainly because of the overwing airflow, then anything that disturbs this airflow is a bad idea.

Edited February 11, 2014 by squezzer

[JagRigger]

Overwing pylons are draggier than underwing ones, partly because they exist in a faster airflow and partly because anything that interferes with the upper wing airflow is generally a bad thing - unless the flow is so poor anyway that fixes such as fences, notches or vortex generators are required

Our Unit Test Pilot told me he thought an aircraft with overwing pylons ( just pylons - without the LAUs ) actually flew better !

I always wondered why the Jaguar wasn't designed with wing tip pylons for AAM's.

Trevor

Very lightweight structure towards the tips.......

Edited February 11, 2014 by JagRigger

[Giorgio N]

Our Unit Test Pilot told me he thought an aircraft with overwing pylons ( just pylons - without the LAUs ) actually flew better !

Likely because on the Jaguar the pylon is located on a wing fence, of which can be considered an extension. Having the pylon alone is like having a larger fence

[Selwyn]

Normally this is the case but there is normally a design requirement that stores, (and sometimes the racks and pylons), must be capable of departing the aircraft, assisted by gravity alone, in case of failure of the normal forced-release mechanism. This requirement can be met over a limited speed and attitude range and not the full envelope required for normal release.

Magpie 22

I don't know where you got this idea from but its totally wrong. In my 35 years of working on Aircraft munitions and release systems I have never seen or heard of a system that can do both. There is certainly no requirement in the relevant Nato STANAG or MIL STD for a system that does this.

I can assure you If the cartridges do not fire there is no alternative way of opening the suspension hooks and you get a hang up.

The only Release units that do not use cartridges (Electro Magnetic Release Units EMRU) are rarely used (if Ever) on external pylons and if seen are used internally in bomb bays.

Selwyn

Selwyn

[rickshaw]

I've read somewhere that overwing pylons for IR missiles are actually better because they allow the missile's seeker to "see" better in dogfight turns, looking into the turn, rather than out of it, when on an underwing pylon. True?

[pigsty]

I can be persuaded by arguments to do with store separation but I'm afraid I don't buy the aerodynamic ones.

1) it's not the upper-surface flow on its own that generates lift, it's the differential between that and the lower-surface flow. Anything mucking up the underside will be equally problematic yet 99 point something per cent of the world's pylons have hung off the underside.

2) upper-surface furniture isn't there to deal with "poor flow", it all has very specific functions. Fences and saw-cuts are to prevent spanwise flow migration and loss of control authority; vortex generators are generally to energise airflow in a particular location to, eg, make the ailerons effective. Any disturbance of the lifting capacity is either minimal (especially for a fence) or worth accepting for the advantages.

3) both aircraft with overwing pylons mount them inboard of the other features - the dogtooth on the Jaguar, and the saw-cut on the Lightning. So they're not plonked in airflow that's already mucky.

[Don McIntyre]

Underwing stores don't leave under their own power. They are blown off using cartridges!

Selwyn

Depends on the stores and the aircraft. Everything we carried on the P-3 would leave of it's own accord once "unlatched."

[Test Graham]

I'm sorry you don't buy the aerodynamic arguments but I'm afraid that the world's aerodynamic specialists do, on strong evidence from theory, tunnel and flight, so put that down to poor explanation here. The flow across the upper wing IS more sensitive than the flow below, perhaps because it is generally faster, and there is a greater drag penalty paid for any disturbance. Excrescences such as aileron hinges are fitted beneath the wing rather than above it, though there would be no mechanical reason for that. Airflow and access are sufficient to explain why the vast majority of weapons are carried underwing, and overwing carriage is only ever adopted when there is no alternative. There are perhaps some stability and handling aspect to the matter, but that's not something I can sensibly expand upon. (Other than pointing out that pendulums are more stable when the weight is above the pivot rather than vice versa, but I feel that is grossly over-simplistic!).

Trying this another way and using your comment about the differential between above and below: anything in the way of the flow slows it down ( = adds drag). On the undersurface, this increases the difference and thus will (if anything) add lift. On the uppersurface this slows the flow and thus decreases the difference and hence lift. The logic of your first point tells us that the underwing position is preferable.

For your second point, uppersurface furniture is indeed required to deal with poor flow. In your specific examples, spanwise migration is poor flow and loss of energy is due to poor airflow. The poor airflow is the cause of these deficiencies, the furniture there to improve it. The overall effect is beneficial, despite the introduction of increased drag, and these devices require considerable design and test effort in tailoring to the specific problems of the wing.

As do overwing pylons, to reduce the inevitable negative effects. I believe the comment about the Jaguar was that the pylon replaced/enlarged an existing fence, not the dogtooth which was indeed further outboard. As for it flying "better", that I'm afraid is in the realm of handling so I can't comment other than I'd heard a similar statement at the time (though I wasn't sure how seriously it was intended). Nonetheless, it certainly didn't fly faster!

I should perhaps add that in the late 70s I was a member of BAC's performance aerodynamics section, and specialised on the Jaguar, although I do seem to have forgotten rather a lot since.

[pigsty]

Oh well, I'll give you that one ...

[Scootsah1]

EMRU's were used on the inboard pylons of Hunters. No.1 Mk1's if I remember. When the FGA9 came along with outboard pylons No.119 ERU's were fitted. Navy Hunter's had Single point suspension (ball type) ERU's fitted, can't remember what type or mark though.

Happy days

Scoots