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On 20 September 2016 at 5:28 PM, Ascoteer said:

 

I've been checking my photo's and all of the JP5As have the later style elevator horn.

 

Additionally what photo's I do have of the JP4 also show this style horn.

 

I think it's safe to suggest that the modified horn came in with the introduction of the JP4 and was not an 'In Service Mod'.

 

I would warrant that it was something to do with elevator flutter given that both the JP4 and JP5 could achieve 400 kts.

 

I've got a copy of Bob Clarke's book 'Jet Provost - the little plane with the big history'.  In it there's a photo of XP547 which is said to be the first production TMk4 and it has the modified elevator horn.

 

The first prototype T5 was XS230 (later G-VIVM) which was converted from the penultimate T4 and so would logically retain the T4 elevator horns (it certainly has them as G-VIVM)

 

 I think that Debs suggestion that it's something to do with the increased speed of the JP4  sounds right (but don't tell her I said that :))

 

Edited by Fritag
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WRT the intakes atop the engine bay access door, the Aircrew Manual refers to these as 'Air circulation ducts'. They serve to admit cooling air around the outside of the engine. They are definitely bigger on the JP5 (and presumably on the JP4 which had the same 3000lbs thrust RR Viper 201 engine); I would warrant this is for incresed cooling of the engine which was some 47% more powerful than the RR Viper 102 fitted to the JP3:

 

JP5A_zpsvxpnvg5b.jpg

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1 hour ago, Ascoteer said:

They are definitely bigger on the JP5 (and presumably on the JP4 which had the same 3000lbs thrust RR Viper 201 engine); I would warrant this is for incresed cooling of the engine which was some 47% more powerful than the RR Viper 102 fitted to the JP3:

That's certainly what I'm seeing.

 

My memory of watching service JP5s was that they seemed to take forever to get airborne and made a lot of noise disproportionate to movement

Now that I work on an airfield with civilian operated JPs/SMs my memory is not disappointed!

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5 hours ago, Ascoteer said:

WRT the intakes atop the engine bay access door, the Aircrew Manual refers to these as 'Air circulation ducts'. They serve to admit cooling air around the outside of the engine. They are definitely bigger on the JP5 (and presumably on the JP4 which had the same 3000lbs thrust RR Viper 201 engine); I would warrant this is for incresed cooling of the engine which was some 47% more powerful than the RR Viper 102 fitted to the JP3:

 

JP5A_zpsvxpnvg5b.jpg

I see it makes a point of referring to the roughened leading edge, does the relevant manual also comment upon its provision?

 

Just asking 'acos we noticed it during Steve's exposition and confirmed its rubberyness at Hendon a while back

 

(I have to say I do like the JP5, looks just as a straight winged jet should in my eye)

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10 hours ago, Ascoteer said:

That doesn't fit with my memory of flying the 5A. ;)

 

The 3A on the other hand, dear gods the first time I had a ride in one of those infernal things...

 

I'm convinced it only got airborne owing to the curvature of the earth!

 

As I understand the history extra performance of the 4 and 5 was  thought to be useful and cost effective in taking studes further into the fast jet training before going onto higher performance and more expensive types.

 

As it happens at Linton-on-Ouse and Church Fenton in the 80's studes transitioned from the 3 to the 5 only if selected for fast jet lead in training.

 

My memory is the same as Debs in that the 5 seemed to have more than enough performance - and I agree with Bill that it's a lovely looking aircraft :)

 

Mind you - and whatever it looked like from the outside - the old Mk 3 went plenty fast enough to be too fast for the brains of ab-initio studes!  As all of the poor s*ds who got chopped during training could well attest to :) As I remember it the darned thing was airborne way before the young Fritag brain was ready for flight......

 

 

Edited by Fritag
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2 hours ago, Fritag said:

Mind you - and whatever it looked like from the outside - the old Mk 3 went plenty fast enough to be too fast for the brains of ab-initio studes! 

 

Imagine what it was like doing your entire BFTS on the 400kt wonder jet!

 

9 hours ago, perdu said:

I see it makes a point of referring to the roughened leading edge, does the relevant manual also comment upon its provision?

 

Just asking 'acos we noticed it during Steve's exposition and confirmed its rubberyness at Hendon a while back

 

The Aircrew Manual states:

 

'Roughened outboard leading edges of each wing - to minimise any tendency for the spin to oscillate (mainly in roll).

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An observation of the kit and some information for you all.

 

This kit is my current WIP, my subject is XP629 when it was the College of Air Warfare Macaws display team as found in Xtradecal X72250

 

Contrary to the decal sheet's instructions, XP629 is a T.4 not as Xtradecal have it, a T.3, see the Jet Provost File entry here

 

So I pulled an old Airfix JP.5 out of the stash to compare the tailplanes and elevators.  My plan was simple, offer up the Mk5 tailplane to the Mk3, mark the point where the elevator horn finished on the Mk3, cut, shape and fill, et voilà!  A Mk4 tailplane - sorted! 

 

But no!  Firstly, the Mk5 kit tailplane is shorter in chord than the Mk3 kit (I suspect the newer kit to be more accurate though), no worry though as I could line up the trailing edge and still mark it up from there, then I noticed that the Mk3 kit's elevators finish at the same point as the Mk5 kit.  In other words, the Mk3 kit does not appear to have full chord elevator horns as per Fritag's photo's earlier in the this thread.  Whilst it saves me a job it does cause a bit of confusion, presumably the Mk3 measured up by Airfix had a Mk4 tailplane which would be a Modification by service engineering rules, so can somebody with access to a JP.3 vol 2 see if any such modification was promulgated (good services word that)?

 

Finally, the larger Air Circulation Ducts used on the Mk4 and Mk5.  The Mk5 kit has these as separate pieces, so if you feel so inclined and/or profligate, you could always rob them from a Mk5 kit, however, from the photos earlier in this thread, you can see they're not particularly complex and easily reproduced from stock which is what I'll be doing.  I took my trusty digital calipers to the Mk5 kit parts and can report that they're 1.81mm long, 2.62mm wide and 1.57mm high - the kit I measured was an original 1970's issue so before any wear on the moulds took place.

 

Hopefully the information on the intakes will be useful, I can assure you I won't be going to a hundredth of a millimetre accuracy for mine but they'll be close enough.

 

I'm open to other's interpretation of the elevator issue and could be quite wrong, I'd be interested to see your interpretations.

 

Wez

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1 hour ago, Wez said:

 

But no!  Firstly, the Mk5 kit tailplane is shorter in chord than the Mk3 kit (I suspect the newer kit to be more accurate though), no worry though as I could line up the trailing edge and still mark it up from there, then I noticed that the Mk3 kit's elevators finish at the same point as the Mk5 kit.  In other words, the Mk3 kit does not appear to have full chord elevator horns as per Fritag's photo's earlier in the this thread.  Whilst it saves me a job it does cause a bit of confusion, presumably the Mk3 measured up by Airfix had a Mk4 tailplane which would be a Modification by service engineering rules, so can somebody with access to a JP.3 vol 2 see if any such modification was promulgated (good services word that)?

...

I'm open to other's interpretation of the elevator issue and could be quite wrong, I'd be interested to see your interpretations.

 

Wez

 

Having built the Airfix Mk5 not that long ago I wouldn't put over much faith myself in the accuracy of dimensions such as the chord etc. So I think you're right to be cautious there :)

 

Having also just received in the post one of the new Airfix Mk 3's (purely out of interest of course....:whistle:) it seems to me that the tailplane is Airfix's interpretation of the Mk 3 tailplane and it isn't intended to be a Mk 4/5 tailplane.  I think the clue is in the shape as well as the length of the elevator horn.  Here's a piccie I've just taken of the Airfix Mk 3 tailplane alongside the completed CMR Mk 3 I built.  It's the angled tips of the elevator horns I'm referring to:

 

7000952255b21e142c1298c6cdfddc43_zpsbpai

 

And the Airfix Mk3 and the Mk 5 I built,  See the squared of end of the Mk 5 elevator horns?  You can see it on the photo of the hendon Mk5 I posted earlier.

 

3540c3d05b960c76609c65bce5f6f145_zpsbbai

 

That's my first thoughts anyway.  Like Wez I'd be interested in others too.  Debs?

 

BTW.  The CMR Kit had options to be built as a Mk3 or a Mk 4 and whilst it offered different size air circulation ducts it didn't (as I remember) offer different tailplane options.

 

I've heard that CMR used the Newark museum Mk3 (which incidently I flew - no doubt very badly - at Church Fenton) as a reference and maybe they missed the different tails?

 

Edited by Fritag
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Oooh a conundrum!

 

I must confess to not having NB'd that the elevator horn on the JP3 is tapered. Accordingly I popped down to the museum and took this shot proving that it is:

 

DSCF1568_zpssspu7qn0.jpg

 

I then measured up the tailplane and elevator and transferred the measurements onto a plan drawing in one of the engineering APs. The measurements are in cm:

 

JP3%20Tailplane_zpsa84axk5p.jpg

 

A = 161

B = 86

C = 176

D = 76

E = 7.5

F = 48

G = 77

H = 65

I = 21

J = 30

K = 64

L = 10

M = 9

N = 56

 

 

I'm of to the Bomber Command Memorial at Lincoln on Thursday. If I get chance I'll pop into Cranditz and measure up the JP5A they have on the Gate there.

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Oops - sorry -  I hadn't thought to mention that the older style elevator horns were angled/tapered as well as longer.  Might have saved Wez a bit of puzzlement if I had.

 

That plan drawing from the engineering AP posted by Debs is interesting.  If the outline is completely accurate (I dunno whether they are intended to be) then it's a little moot as to whether CMR or Airfix have captured the shape better and also that the elevator horns aren't really full chord in the sense they only go as far forward as the front spar - and it's only the curve of the elevator tip that makes it look full chord.

 

The photo that I posted of the Mk 3 tailplane is a little misleading cos of the angle it's taken from.

Edited by Fritag
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Well thanks to both Fritag and Debs (Ascoteer) again for their input, it clears things up - a little bit.  I'd be interested to see what Debs comes up with against the JP5A.

 

I've decided to revert to my original plan for the tailplane and elevator re-modelling on this.

 

I wouldn't put too much reliance on that extract from the AP, it's meant to be representative rather than accurate like a scale plan.

 

Wez

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Great! Lots of useful info here - much appreciated! -Esp as I'd like to do a T4 or two.

 

So to check if I've understood everything -to recap:

T4 differed from T3 in:
-having later style horn balance (as JP5)
-larger pitot tube bracket under wing
-bigger air circulation ducts on  and around engine bay doors.

 

Right?

 

Jay
 

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1 hour ago, Mountain goat said:

Great! Lots of useful info here - much appreciated! -Esp as I'd like to do a T4 or two.

 

So to check if I've understood everything -to recap:

T4 differed from T3 in:
-having later style horn balance (as JP5)
-larger pitot tube bracket under wing
-bigger air circulation ducts on  and around engine bay doors.

 

Right?

 

Jay
 

 

Not seen the pitot to confirm that but yes that's pretty much it.

 

A T.51 is an export T.3, a T.52 is the equivalent of a T.4

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On 26/09/2016 at 16:27, Dave Fleming said:

Sounds about right - not sure if any cockpit differences, but in 1/72 they'll be minor

 

The T4s were never brought up to T4A standard (unlike the T3 / T3A) so will have a black interior like the T3 as opposed to the grey interior of the T3A.

 

The pre avionics upgrade aircraft also had a different radio fit and there were differences in instruments and their locations.

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Yesterday I was at the Bomber Command Memorial in Lincoln so, on the way home I stoppedat Cranditz to look at the JP5A gate guard. She's a wee bit of a fraud actually because, despite wearing the RAF College blue fuselage band and the tail number '3', she was only at Cranwell (as a 'Poachers' aircraft) between 1971 and 1975.

 

Anyhoo some photos:

 

Here you can see that the engine bay door air circulation inlet ducts are significantly bigger than those on the JP3:

 

DSCF1569_zpscaxfzalb.jpg

 

But the exhausts are the same as the JP3:

 

DSCF1570_zpsbosa1u8f.jpg

 

Some shots of the tailplane:

 

DSCF1571_zpspf8lc8la.jpg

 

DSCF1573_zps6mool9zm.jpg

 

DSCF1574_zps5s556ahz.jpg

 

DSCF1575_zpskex5mmr0.jpg

 

DSCF1576_zps8tmtixgv.jpg

 

DSCF1577_zps9qeq3qcg.jpg

 

DSCF1579_zps7eu8lupf.jpg

 

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I measured up the tailplane and elevator and redrew the diagram from the AP:

 

JP5A%20Tailplane_zpsjs6w3ha8.jpg

 

The measurements are as follows:

 

A = 157

B = 80

C = 176

D = 76

E = 7.5

F = 48

G = 77

H = 65

J = 41

K = 64

L = 10

M = 9

N = 56

O =12

P = 16

 

From these measurements it is apparent that the tailplane is the same on the JP5 as the JP3 apart from a minor difference at the outboard leading edge/tip around the area of the front spar.

 

Additionally the elevator is quintessentially the same (including the tab) aside from the area of the horn balance.

 

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