Can anyone ID this odd thingamajig on the Javelin's wings?

[Peter O]

I'm building the Airfix 1/48 Javelin, and I've come across a detail that I can't identify. I've found enough photos of it to replicate it on the model, but I'd like to know what it does.

It's a tab or prong that protrudes from the wing surface, and is guarded by one or two wire guards. It looks like it hinges from the forward edge to lie flat. It's too far outboard to be a landing gear or flap position indicator, and it doesn't seem to be on early marks that didn't have vortex generators.

Does anyone know what this is? Other than a thingamajig, gubbins or whatnot . I was a KC-135/FB-111A mechanic back in the late 1970s, so it bugs me not to know what it is!

Thanks!

Peter

[bobgpw]

It would appear to be the stall warner. It is held by spring pressure at right angles to the airflow and closes on electrical contacts, producing an audible warning. As the airflow over the wing increases, the flap rotates in line with the airflow and the contacts open - stall warning stops.

If the airflow breaks away, the spring causes the flap to rotate back to the "closed contact" position - stall warning sounds and you'd better do something about it quickly!

Think that's what it is anyway.

[sloegin57]

I'm building the Airfix 1/48 Javelin, and I've come across a detail that I can't identify. I've found enough photos of it to replicate it on the model, but I'd like to know what it does.

It's a tab or prong that protrudes from the wing surface, and is guarded by one or two wire guards. It looks like it hinges from the forward edge to lie flat. It's too far outboard to be a landing gear or flap position indicator, and it doesn't seem to be on early marks that didn't have vortex generators.

Does anyone know what this is? Other than a thingamajig, gubbins or whatnot . I was a KC-135/FB-111A mechanic back in the late 1970s, so it bugs me not to know what it is!

Thanks!

Peter

Peter,

this is the reply I gave to the same question last October:-

"1. A device designed to cause a technician to trip and impale his left knee on to the inboard vortex generator (middle row) on Christmas Day 1965 at N'dola Zambia thus causing said technician to use profane language profusely as well as missing his new-born son's first Christmas. (Thank you Ian bloody Smith).

2. A stall warning device which also incorporated a horn in the cockpit and on some aircraft a "stick-shaker" although by the time that the latter came in the crew were well gone.

Take yer pick.

Dennis "

Have fun with a great kit of a great aeroplane.

HTH

Dennis

[Jennings Heilig]

I'm curious what a stall warning horn tab would be doing on top of the wing at mid-chord? I've never seen or heard of such an arrangement. Every stall warning device I've ever seen or heard of has been on the leading edge.

[Duncan B]

I believe the positioning was due to the Javelins nasty habit at high AoA of causing the tailplane to be starved of clean airflow and then the whole thing going into a non recoverable flat spin.

Duncan B

[Peter O]

Thanks, Gents! I had searched BM, but apparently didn't find the right posting.

It is a fun kit. So far I've just worked on the wings. I'm building XH754 using Alley Cat's conversion and Eduard's interior set. Gotta love the bumblebee undersides

Peter

[Rob G]

So the Airfix Flat Iron is a winner then? I've had a thing for them ever since I saw a photo of one in an Airfix Annual, way back when that publication was reproduced on clay tablets...

[sloegin57]

I believe the positioning was due to the Javelins nasty habit at high AoA of causing the tailplane to be starved of clean airflow and then the whole thing going into a non recoverable flat spin.

Duncan B

Aye, Aye !, Duncan's got the book out again. Almost spot on as I heard whilst on det to 29 that the Javelin could and had recovered from a "non-recoverable flat spin" - but only after the crew had ejected.

So the Airfix Flat Iron is a winner then? I've had a thing for them ever since I saw a photo of one in an Airfix Annual, way back when that publication was reproduced on clay tablets...

Which is exactly what the aircraft was designed on.

Dennis

[sloegin57]

Thanks, Gents! I had searched BM, but apparently didn't find the right posting.

It is a fun kit. So far I've just worked on the wings. I'm building XH754 using Alley Cat's conversion and Eduard's interior set. Gotta love the bumblebee undersides

Peter

You also have to admire the dedication that Alistair of A2Zee puts into his conversion/kits, one reason that the T.Mk.4 conversion was relatively late - lack of positive information. I am quite convinced that in the not too distant future, Ali will take over the exalted mantle currently worn by young John Adams of Aeroclub, if he hasn't already.

Dennis

PS - any hint of me being biased in any way shape or form is purely factual.

DR

[Selwyn]

Aye, Aye !, Duncan's got the book out again. Almost spot on as I heard whilst on det to 29 that the Javelin could and had recovered from a "non-recoverable flat spin" - but only after the crew had ejected.

Which is exactly what the aircraft was designed on.

Dennis

Absolute rubbish!

It's common knowledge that Gloster's design team had the latest in chalk and slates.........................!

Selwyn

(Who knows this because he is not normally allowed sharp things.)

[Graham Boak]

I suggest it is on the upper wing because Glosters had a pretty good idea of the movement of the separation boundary. As long as it was aft of the device the aircraft was flying normally; once it moved towards the leading edge and reached the device the aircraft was recoverable; when it was significantly forward of the device all hope was gone.

[Jennings Heilig]

I believe the positioning was due to the Javelins nasty habit at high AoA of causing the tailplane to be starved of clean airflow and then the whole thing going into a non recoverable flat spin.

I would be very interested to see the airflow disruption pattern on the upper surface of the Javelin's wing during the stall. I still can't figure out why a stall warning horn actuator would do any good at mid-chord. Makes no aerodynamic sense to me, but then I've never flown a flatiron either

[Graham Boak]

Given that's where it was, and it did work, there must have been some effect similar to what I suggested. During the stall or approach to the stall the flow pattern changed in a way to trigger the device.

Remember that a true delta will generally be controllable at greater angles than a conventional wing, and will usually settle into a stable descent post-stall with no obvious pitch change. The purpose of the device is not necessarily to avoid the stall, but to avoid angles where the high tailplane is blanked by the flow and hence unable to reduce the angle of attack and recover to normal flight. This was called deep stall. It makes aerodynamic sense to me, and I was one according to my job title, although not on the Javelin and I don't remember this case ever being mentioned. In my time the deep stall cases discussed were those of the Trident and BAC111, with more conventional wings.

Given that wing flow will generally break down aft of the leading edge, and move forward to the full stall, it is perhaps more curious that stall warning devices should be on the leading edge. But then for a conventional wing the stall is generally more abrupt than for a delta. Devices are usually present not to avoid a deep stall but an atypical (usually asymmetric) stall

Edited September 24, 2014 by Graham Boak

[AnonymousAA72]

I would be very interested to see the airflow disruption pattern on the upper surface of the Javelin's wing during the stall. I still can't figure out why a stall warning horn actuator would do any good at mid-chord. Makes no aerodynamic sense to me, but then I've never flown a flatiron either

Ah..... I see what you've done there Jennings., you've tried to apply the laws of aerodynamics to a Gloster Javelin.....a classic mistake!

[John Aero]

You also have to admire the dedication that Alistair of A2Zee puts into his conversion/kits, one reason that the T.Mk.4 conversion was relatively late - lack of positive information. I am quite convinced that in the not too distant future, Ali will take over the exalted mantle currently worn by young John Adams of Aeroclub, if he hasn't already.

Dennis

PS - any hint of me being biased in any way shape or form is purely factual.

DR

Dennis

Mantles can sometimes be quite heavy. Ali is welcome, and he's young enough to take the strain. Which reminds me Ali and I haven't had a telecon recently. The hoops on the Javelin wing are of course guards to stop the stall warning getting bent.

John

[Cheshiretaurus]

Found on this page Aircraft Profile #179. Gloster Javelin

Consequently a stall warning device was developed which proved effective. A small metal �flag� with a rotating �mast� was fitted at about mid span of the outer wing. At rest, a spring held the flag at right angles to the line of flight and a set of contacts were closed. When the aircraft took off, the airflow moved the flag round into �line of flight� position and opened the contacts. When the undercarriage retracted, a circuit to a sound box, operating on the intercom, was made except for the flag contacts. Should the airflow over the top surface of the wing start to break down, the disturbed flow would no longer hold the flag against its spring, the contacts would close and the pilot would get a warning note in his headphones.

[Work In Progress]

Given that wing flow will generally break down aft of the leading edge, and move forward to the full stall, it is perhaps more curious that stall warning devices should be on the leading edge. But then for a conventional wing the stall is generally more abrupt than for a delta. Devices are usually present not to avoid a deep stall but an atypical (usually asymmetric) stall

That's because the stall warner on the Javelin is working as you suggest, testing actual separation, whereas the stall warner on yer average American light aeroplane is really just a high AOA warning device. What the typical leading edge vane type device works off is the movements of the stagnation point around the leading edge with varying AoA. High AoA, stagnation point moves below the vane, vane closes the microswitch, merry horn goes off. It works well enough for wings with an aspect ratio of 4:1 or 5:1 plus with leading edges reasonably perpendicular to the airflow

Would not be suitable for a delta as you can get such a lot of AoA without disastrous collapse of the lift, due to the amount that starts to come off the tubular vortices. No vane triggered by movement of the LE stagnation point is going to be positionable so that it switches at an AoA higher than around 15 degrees. So it would not give you the info you need on a wing that is useful at much higher angles, which the delta Javelin wing certainly is.

Of course the real solution to all of this is proper analogue AoA measurement to the cockpit, which just about everything racy now has.

Edited September 28, 2014 by Work In Progress