G Limits With Underwing Stores

[Brian Abraham]

Wondering what effect, if any, the carriage of stores has on the permitted G limit that the pilot can pull. An A-4 friend says he can't recall (with the proviso it was a long long time ago) any G limit, though there was a Mach limit. Any one able to give reliable info on say F-4, Harrier, Hawk, Buc or other FJ. Additionally what limits were placed on rolling G - any difference between clean and with stores?
Many Thanks,
Brian

[Mad (Flt) Scientist]

Underwing stores can have significant effects on both rolling and non-rolling 'g' limits, both due to the loads imposed on the store itself (and the pylon) and due to the changed aircraft behaviour due to aerodynamic and inertia changes due to the presence of the store.

I'd have to wrack my brain to get details, but there were HUGE differences on Hawk depending on what stores were carried, with some cases probably halving the 'g' and rolling 'g' envelopes relative to the clean aircraft.

[L Peacock]

Agree with scientist. Cut-backs in norm g approaching 50% are common.
There can be a smaller reduction in g limit when external fuel tanks are empty.

[JohnFTEng]

Yes, rolling with stores is much reduced than when clean.

We had a small whoopsie on Jag flight testing in early 70's when the Dep Chief Test Pilot did some full aileron rapid rolls at 0.8M with full 330L underwing tanks. Not his fault the "dolls eye" indicators were faulty so tanks showed empty. He did comment on debrief that it felt a bit ponderous in roll! Some swift checks on alignment and loads showed no real damage - other than to fatigue count.

[The Rocket]

Agree with scientist. Cut-backs in norm g approaching 50% are common.
There can be a smaller reduction in g limit when external fuel tanks are empty.

As L Peacock correctly states, there are very different limits on g loading, depending on aircraft fit and status. In the F3 Tornado, with full 1800L U/Wing tanks, the A/C is restricted to around half it's maximum g loading, however, this jumps up to around 3/4 of max once the tanks are empty, which is quite a considerable jump.

[PPRuNeUser0172]

In the F3 Tornado, with full 1800L U/Wing tanks, the A/C is restricted to around half it's maximum g loading, however, this jumps up to around 3/4 of max once the tanks are empty, which is quite a considerable jump.

Errrrm we dont have 1800L u/wing tanks. Its either 1500L or 2250L, unless there is one I have never heard of..........

Agree with the reduction in g though

[The Rocket]

Pardon me DS,

The L should have been a KG. :O

I cannot confirm or deny that alcohol may have been consumed. :p

I was referring of course to the 2250L tanks, which as you know contain 1800kg of fuel. :ok:

[3 Point]

Yep, similar story for the Harrier; significant reduction in the G and Rolling G limits with various external stores. Also most external stores configurations carry the imposition of significantly restricting Angle of Attack limits, and usually no VIFFing! Also, stores on the fuselage station carry a performance penalty for Vertical Take Off and (I think I remember correctly) for Vertical Landing.

Happy landings

3 Point

[Double Zero]

It stands to reason, which you were of course getting at in the first place, that aircraft are limited if carrying stores.

There is a relatively recent film of a Wart-on Harrier ( they don't know what to do with it up there apart from chase Whippets ) which departed in a big way & folded the pylons flat under the wing.

Also possibly more to the point, a Sea Jet years ago did a high G pull, resulting in lofting drop tanks, I believe complete with pylons, into a chap's Asparagus bed...

Most if not all fast jet a/c are limited to around 3g until the droptanks are empty or disposed of - rare due to cost unless in real combat - as aerodynamic loads soon come into the equasion.

[Double Zero]

That Harrier link has some remarkable stuff;

Leading photo is of a two-seat AV-8A Spanish Matador !

Two GAU-12 cannon ?

Wing area is different for US & UK aircraft, as the latter have LERX of various sizes.

The GR5 had the dual mode laser / tv ARBS tracker from new, the main addition with the GR7 was FLIR, some display updates & digital moving map.

GR9 to carry Amraam ?!

[Double Zero]

I think you're referring to the 2+, which has not only a cut-down F-16 radar, but strengthened rear fuselage, upward firing chaff / flares etc.

Once saw one fitted with 6 x AMRAAM on decoy launching rails, though not so sure about bring-back.

Would have been a sensible buy, even in small numbers, to go alongide the GR7 / 9 on the present & future carriers, as it's mainly compatible.

Not that I could imagine the Dave ever becoming delayed, or the UK inconveniently having a foe in the meantime.