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A Kestrel (prototype) for a Knave


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... or Happiness is Vectored Thrust!

 

Firstly, I am a fan of the Harrier but mostly the early variants before the airframe was “afflicted” by the lumps and bumps associated with the development of an aircraft. As you may have guessed by my screen name, I’m particularly fond of the prototype aircraft, the P.1127 and P.1127/2, otherwise known as (the/a) Kestrel. To my eye, these are the definitive forms of this aircraft concept/configuration, with their aluminium finish and long pitot tubes sticking out the front, ready for the jousting tournament.

 

I’ve recently returned to the hobby after 20 years or so: the aircraft I always fancied building all those years ago was an Airfix 1/24 scale Harrier but it was never to be. I’ve now decided that I’m going to give converting the Harrier into a P.1127 a go and I thought I’d try posting a WiP to try and keep myself out of metaphorical doldrums.

 

The question was which P.1127 configuration to model? As you may or may not know (or care) there were many configuration states of P.1127 although predominantly they can be split into two groups. The first six aircraft had registration numbers starting with XP (831, 836, 972, 976 980 & 984). The second group with the designation P.1127/2, also given the name Kestrel by the Hawker marketing department had registration numbers starting with XS (688 - 696). This is based on my limited research into the subject, anyway. The reason for being so picky with the registration numbers is because there was evidently quite a bit of variation between each aircraft, especially in the first group of six but also extending into the second group. Relevant differences include (but are not limited to):

  • the wing ¼ chord sweep (the trailing edge was unswept for the first five aircraft but was swept back on the sixth)
  • wing leading edge extensions (saw-tooth extensions were added during development to refine handing)
  • fairing of wing tip into landing gear fairing
  • fuselage length (the Kestrel was extended by 9 inches compared to the P.1127)
  • tailplane area, span & dihedral
  • sweep angle of air intakes (reduced from 35 degrees on the first aircraft to a more moderate 20 degrees on later aircraft… less so on the Harrier upon EIS)
  • various intake lip profiles
  • etc.

Of course all the aircraft above are significantly different to the Harrier (GR1) that is the subject of Airfix’s 1/24 scale kit.

 

The aircraft that I’ve decided to model (try to model) is XP984, a special aircraft for me. XP 984 was the last of the original P.1127 aircraft but was designated as the prototype for the forthcoming Kestrels (P.1127/2). This means that the aircraft originally had the Kestrel wing with the swept trailing edge, the 20 degree sweep on the air intakes and an intermediate tailplane configuration.

 

To my eyes the aircraft in its original configuration looks “the most right” out of all the P.1127 configurations: a nice swept trailing edge with no leading edge extensions to spoil things, a nice sweep on the intakes with no bulbous “elephant ears” ruining the lines but maintaining the aforementioned pitot tube at the nose. (The aircraft, now at Brooklands, has been retro-fitted with a Harrier wing and tailplane so looks less good, IMHO. I’m grateful it’s now inside however).

The reason XP984 is special to me is because I’ve had the pleasure of meeting Ralph Hooper (conceptual design and Chief Engineer of the P.1127 programme) at Brooklands and discussing the aircraft with him for an hour or so. I’d like to build this aircraft to help remember such a wonderful experience.

 

As for model itself (an eBay “bargain”), progress has been made but is intermittent due to family and work commitments. The progress so far includes:

  • Fin: removing air intake from root. I’m unsure whether a reduction in height is required… research is ongoing
  • Tailplane: modified to the correct profile but I only have one of them L a shortcoming of the eBay “bargain”. Airfix themselves couldn’t help… any other ideas? Making one will be simple enough but I’d rather modify!
  • Wing: leading edge extensions removed and tips re-profiled. The model will be displayed in the hover so the flaps need cutting out and lowering but this I’m saving for another day
  • Fuselage: the biggest job was re-profiling the air intakes the kit’s Harrier intakes are wrong for the P.1127 so they were cut out and new ones built up from plastic-card and car body filler (I love that stuff) at the required 20 degree sweep for XP984. This also required making the fairings for the cold nozzles: these have intakes in their leading edges but I haven’t got there yet. I’ve also boxed out the landing gear bays to attempt some detailing in there… we shall see how successful that is. My biggest unknown with the fuselage is the length. The Kestrel fuselage is 9 inches longer that the P.1127 but is the same as the Harrier, I think. I’m modelling the Kestrel prototype so I don’t know if XP984 had a P.1127 or Kestrel/Harrier length fuselage. Any ideas?

 

There’s clearly a lot of work left to do, especially on the fuselage (and especially if it wants shortening by 9 scale inches!). The other big thing is the fairing over the wing but I need to wait for the fuselage to be joined first, I think.

 

As I said, progress will be intermittent but I’m hoping the pressure of the forum will eventually get me over the line. The finished model will not be worthy of any special mention like so many of the fantastic efforts displayed on this forum: I shall be ecstatic if it is recognisable as a Kestrel (prototype).

 

I’ve tried to add some pictures below… fingers crossed.

 

Anyway, thanks for looking,

 

P.

 

(Sorry for the quality of the photos, clearly they were taken on my phone!)

 

The bits so far...

Xdl9MC3.jpg

 

Fuselage showing modified intakes and cold nozzle fairings

46cllIF.jpg

 

GsUm1Mx.jpg

 

lo4OLgd.jpg

 

The air intake structure aft of the cockpit is a key omission of the kit, perhaps not surprising given its age. Plasticard has been used to rough-in some of the structure but more work is required to tidy it up and fair it in. I shall invest in some Milliput, which I have never used but am led to understand that it might be useful here than my beloved Isopon.

7iuTwmp.jpg

 

Yours truly and the Chief Engineer himself, in front of the aircraft in question.

ADBip8x.jpg

 

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I too prefer the P1127 to the Harrier. You seem to have made a very nice start with the intakes and nozzle fairings. Consider yourself under pressure!

 

Regards,

Adrian

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The Kestrel had a different mark of Pegasus engine which altered the fuselage shape around engine into that more or less of the Harrier. Off the top of my head I cannot remember if XP984 had the engine. If you can find a copy, Tony Buttler's book on the P1127 Kestrel and Harrier is worth having. Published by History Press in 2017, it has a lot of info and is photo heavy with stuff I do not think has been published before. Has some good diagrams including a useful one on the evolution of the wing shape. It stops when the Harrier entered squadron service, but is a book about the development of the concept and early prototypes. 

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Hi P 1127

 

Great idea for a challenge. One thing that improves the look ofthis giant size kit is to fill in all the rivets. Halfords make a thick brush on primer that does the trick. Its best done before the parts get glued together.

 

Regards Toby

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You're a brave man. Those were exciting times in Aircraft development,with so much cutting edge stuff going on.

And I still remember some of the names of the main characters and their exploits.

I found your book, https://www.amazon.co.uk/Hawker-P-1127-Kestrel-Harrier-Developing/dp/0750965304/ref=sr_1_25?keywords=tony+buttler&qid=1563993146&s=books&sr=1-25

 

I'll be following along, take your time, and get it right or you'll regret rushing. The forum is (mostly) patient.

Pete

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Oooh, this looks interesting. Not my usual theme or scale but I can’t resist a Kestrel...

 

Welcome to BM as well. If you need any help or tips then post away - I’ve learned a lot from the great bunch on here. 

Milliput is great - sticky at first and then mouldable with a wet blade it sets hard quickly and can be sanded with ease. I would start with the normal grade. Any extra can (according to The Baron) be kept in the freezer for later use. 

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This has to be fun in the offing

 

I built (partially) the kit's early version a long time ago

 

Wish I'd finished it properly

 

😕

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Thanks for the interest! I'm feeling the pressure already 😉

 

17 hours ago, Mr T said:

The Kestrel had a different mark of Pegasus engine which altered the fuselage shape around engine into that more or less of the Harrier. Off the top of my head I cannot remember if XP984 had the engine. If you can find a copy, Tony Buttler's book on the P1127 Kestrel and Harrier is worth having. Published by History Press in 2017, it has a lot of info and is photo heavy with stuff I do not think has been published before. Has some good diagrams including a useful one on the evolution of the wing shape. It stops when the Harrier entered squadron service, but is a book about the development of the concept and early prototypes. 

Mr. T, Thanks for the heads-up on the book. As a matter of supreme coincidence I was gifted the very book just yesterday evening at club night. I can attest to the pictures in the book being useful (I haven't read it yet...) and luckily the information therein supports the assumptions and modifications that I've already made. PHEW! Interesting to hear your thoughts on the engine: I had assumed that the diameter had remained fairly constant throughout development but I was aware that the size of the accessories on the top had increased due to increased secondary power demands... leading to a larger hump on top of the wing for the Harrier. I'll pore over my new book and find out (as well as re-reading the relevant chapter in "Pegasus: The Heart of the Harrier" by Andrew Dow, recommended as a good source of info. by Ralph Hooper himself!)

 

I should have mentioned my references above, for good measure! As well as my new book, I've mainly been using "Prelude to the Harrier: P.1127" by Hugh Merewether (test pilot) and a paper (long and short versions) written by John Fozard (Harrier Chief Engineer) and published by the AIAA. The former has interesting bits a pieces about the flight testing of the P.1127s as well as individual aircraft overviews whilst the latter is fantastic for proper technical details. I'd recommend both to anyone interested: I can post a photo of the front covers if required.

 

16 hours ago, Planebuilder62 said:

Hi P 1127

 

Great idea for a challenge. One thing that improves the look ofthis giant size kit is to fill in all the rivets. Halfords make a thick brush on primer that does the trick. Its best done before the parts get glued together.

 

Regards Toby

Toby, thanks for the paint info. I'll investigate. To confirm, its a brush on thing rather than the rather fetching yellow filler/primer from a spray can? Its definitely a job to do soonish: some of the pock-marks have been inadvertantly filled with Isopon anyway but that doesn't seem like a sensible route to follow = lots of work.

 

13 hours ago, CedB said:

Oooh, this looks interesting. Not my usual theme or scale but I can’t resist a Kestrel...

 

Welcome to BM as well. If you need any help or tips then post away - I’ve learned a lot from the great bunch on here. 

Milliput is great - sticky at first and then mouldable with a wet blade it sets hard quickly and can be sanded with ease. I would start with the normal grade. Any extra can (according to The Baron) be kept in the freezer for later use. 

I confess to never have used Milliput before but am looking forward to seeing what exciting avenues it opens up for me. Good tip wrt the freezer, I'll do my very best to remember it for the future.

 

I'm now on holiday for 9 days or so and if I'm clever about packing the car I might be able to sneak the Kestrel into the boot so I can work whilst I'm away! Hopefully i'll have some progress to show upon my return!

 

Cheers,

 

 

P.

Edited by P.1127
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Welcome to BM, and what an excellent first choice subject and in 1/24 scale it should look superb. I plan to follow this one for sure!

 

Terry

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  • 2 weeks later...

A small post-holiday update on the Kestrel. The good news was that I managed to sneak it into the car with me (hoorah) but the bad news is that I didn't get as much done as I wanted to: I was too tired in the evenings from long hot days traipsing around the countryside and generally enjoying family life!

 

My intention was to have a break from the heavy duty work of filling/sanding/filling/sanding etc and have a go at some detailing on the main and nose landing gear bays. The Airfix offering leaves a lot to be desired here, in fact the side walls are not defined at all. I hadn't done anything like this before and I thought it'd be fun. I was "sort of" right but was left hankering for more filling/sanding work as a tonic from the fiddliness! In the end I only managed the MLG bay (I think I'll now focus on this area and get the large one piece door and MLG itself done before conducting any more major work). The work is rough by the standards of this site but I have learnt a lot for next time (the main thing being I should have detailed the wall panels before they were stuck together to form the box).

 

I'm not sure on the rules... perhaps I'm breaking them... but the following URL shows the basis for my efforts. http://www.primeportal.net/hangar/howard_mason2/p1127_kestrel/index.php?Page=2

 

The aircraft in question here is XP831 at the Science Museum: my assumption is that the sixth aircraft (XP984... my aeroplane) would be similar enough to the first wrt to landing gear bays to make no difference. To reiterate, I'm aiming for "that looks like a Kestrel" rather than a faithful miniaturisation.

 

Below are the photos showing the limited progress. FWIW the MLG bay fits better into the fuselage than what the photos suggest: it's much better when held together properly! I hope that by the time I've practiced on the NLG bay, which also won't really be seen once complete, that the cockpit might look half tidy.

 

Another minor victory was had whilst away though. The Tony Buttler book (referenced earlier in the thread) confirms on page 59 that XP984 had the longer (i.e. Harrier length) fuselage, which means that the plastic as supplied by Airfix doesn't need ~1cm cutting out of it. HOORAH!

 

 

W7iJkz9.jpgspacer.png

 

Until next time,

 

P.

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Nice start, talk about jumping in at the deep end!

 

Impressed of Mars 👽

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26 minutes ago, Martian Hale said:

Nice start, talk about jumping in at the deep end!

 

Impressed of Mars 👽

Well it is a jump jet Martian!

 

Terry 

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On ‎07‎/‎08‎/‎2019 at 21:40, Gondor44 said:

So is this a conversion of the Airfix 1/24 scale kit?

 

Gondor

 

Watching with interest.

Yes indeed, the venerable 1/24 scale kit, circa 1974 I think. I'm working with an early boxing so everything is still relatively crisp (although much of the detail is being obliterated anyway!)

 

On ‎08‎/‎08‎/‎2019 at 00:06, Martian Hale said:

Nice start, talk about jumping in at the deep end!

 

Impressed of Mars 👽

Thanks Martian, I'm trying my best to keep my head above water with the build...

 

As previously stated I've decided to crack on with main landing gear area. The Kestrel landing gear itself is similar enough as makes no difference to the Harrier, as far as I can tell. The big visual difference appears to be the door configuration. The Harrier has a three door MLG arrangement: a small forward door and two larger doors hinged on outboard edges. The Kestrel has a two door arrangement, the same small forward door but a singular large door, hinged on the leading edge. Thus I am in the process of modifying the two Harrier doors provided in the kit... slowly but surely.

 

Incidentally, it seems as though the singular large MLG door hinged on the leading edge may have provided a fairly effective airbrake for the P.1127s, hence the lack of the large airbrake found on the Harriers. Just a theory though!

 

Watch this space for an update over the weekend, hopefully!

 

P.

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On ‎09‎/‎08‎/‎2019 at 20:16, chrisbob12 said:

I'm all eyes! I am considering taking the plunge back into modelling with the old 1/72 P1127. And I had the old 1/24 Harrier back in the day.

Funnily enough I recently completed the 1/72 P.1127, it was a nice a relatively quick build. There was still a considerable amount of filler required along all of the seams and I decided to build mine in forward flight with the landing gear retracted... and of course the doors didn't fit well... so lots of filler there too. It was fun anyway and I learnt that I probably need to invest some time in developing my finishing techniques before trashing the paint-job on this thing.

 

I've made a small amount of progress on the 1/24th Kestrel, focusing on the MLG area. The bay is as detailed as it's going to get and as mentioned previously I've been working on the doors, which are now all but complete. The two MLG doors provided in the kit have been glued together, a plastic-card box built for the inner side to thicken it up and a pair of swan-neck hinges roughed up. Unlike the kit offering I won't have the landing gear moveable so all this will be glued in place upon final assembly, making the design of the hinges easier!

 

The MLG strut has been lengthened to represent the unloaded "extended" gear because I'm planning to display this model on a stand in the hover. The plastic-card torque link and systems positioner are a bit rough but will be hidden by the wheels, for the most part.

 

As for the wheels and tyres, my plan is to use the kit offering after a little bit of modification (I quite like the real rubber tyres... there's no accounting for taste). The hubs are plain and need a series of holes drilling into them to improve the appearance, which should be fun!

 

The photo below shows what I'm aiming for (taken from a previously referenced walk-around of XP831... http://www.primeportal.net/hangar/howard_mason2/p1127_kestrel/index.php?Page=2 )

 

 

p1127_kestrel_21_of_49.jpg

 

"All" that's left to do here before a bit of painting is some pipe-work on the MLG itself for the brake hydraulics and the tie rod linking the gear and door together (and the wheels...)

m2KWG4x.jpg

 

kVmVMJ2.jpg

 

QhjKDan.jpg

 

 

The photos are still rubbish, I'm afraid. I'll have a good think about how I can improve on them for next time.

 

 

P.

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Happiness is indeed vectored thrust!

 

I admire your boldness in taking this conversion on. Having converted Airfix's old 1/24th scale GR1A to a Sea Harrier FRS1 back in the mid-80s, then doing a major update of it in the late-90s and early-00s, I know some of the issue you will have to face. I'm also part way through converting a Monogram 1/48th scale GR1 into the original P.1127 XP831; a project which has stalled in a big way for a few years.

 

You've made a great start and trust you'll be taking advantage of Airfix's many rivets to enable you to get the finish required with those darned dirty rivets!

 

Fuselage Length

Quoting from Hugh Merewether's book "Prelude to the Harrier: P1127 Prototype Flight Testing and Kestrel Evaluation": (p21) "XP984 was delayed for the incorporation of a new wing with a swept trailing edge instead of a straight one, and curved streamwise tips. In addition the engine was moved forward 9 inches relative to the wing and everything aft of it, to correct the thrust centre of gravity relationship with the new Pegasus 5 engine. XP984 was the first aircraft to Kestrel standard..." This would indicate that the fuselage is the same length as a Kestrel's 509.92 inches (42ft 6in). The GR1's length was 546.62 inches, including the pitot (45ft 6.6in).

 

Wing shape

Quoting again from Hugh Merewether's book: (p26)"..there was some reluctance to embody a completely new wing (known as the "7th" wing) and delay the appearance of XP984, to which it was fitted. This wing had a swept trailing edge and completely eliminated transonic wing drop. However, it suffered wing rocking, which induced high fin loads at comparatively low incidence."

XP984's original wing had RAF roundels on both surfaces and the fin had RAF flashes when XP984 was fitted with this wing.

Again from Merewether's book: (p26) "After much experimentation, matters were brought under control by the addition of vortex generators to the upper wing surface and by extending the wing leading edge on the outer portion of the wing."

 

Information from Tony Buttler's book The Harrier - more correctly a P1127(RAF) - wing was fitted in early 1966, first flight on 25 March, and so fitted XP984 had the Tripartite Evaluation Squadron on the wings and fin. Its original wing was refitted by 15 June 1966 after which it did trials on Bulwark from 17-20 June, and the "Hole in the Wood" trials from 19-28 September. Flown by John Farley and Sqn Cdr John Rustin these trials proved the concept of dispersed operations in wooded sites to better promote the operational flexibility fo the design. Photos of the "Hole in the Wood" trials show that the original wing had vortex generators fitted by this time. For both these trials XP984 had the Harrier type tailplanes fitted...

 

Tailplane shape

XP984 flew with both the Kestrel/Harrier style tailplanes and the smaller original Kestrel tailplane too. Other than for the 17 June to 28 September 1966 period, I do not know when it flew with which.

 

Details

XP984 had toe-operated wheel brakes (hence the rudder pedals are as in the kit), two pylon attachments for underwing drop tanks and a 5ft diameter tail parachute for stalling and spinning trials.

 

 

On the main u/c, just be careful that you don't make the leg too long as if unloaded. An old trick of Harrier builders is to fit the nose and outrigger legs first then adjust the length of the main leg to ensure all five wheels are in contact.

 

For information on what I did on the big SHAR which you can adapt for XP984 please check out the "Modelling the Harrier" section of the Harrier SIG's website:

http://www.harriersig.org.uk/models/index.htm 

 

Drop me a PM with your email included if you need any reference material on XP984 or the P.1127 series, e.g. HS drawings, photos, cockpit information, etc.

 

A Harrier SIG member is a volunteer at Brooklands so I can put you in contact if you'd like to get up close and personal with XP984 once more, e.g. with a tape measure to confirm key measurements and a camera to get walk around photos.

 

I hope that all helps. Looking forward to seeing more progress when you're back at the desk.

 

Best wishes

 

Nick

 

Edited by NG899
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XP984 Notes

 

Outriggers

Were the same type as on the Kestrel and not like those on the earlier P1127s; unlike as depicted in the AIRfile 1st Generation Harriers book.

The same style outriggers are fitted to Kestrel FGA1 XS695 in Cosford, which is a 20 minute drive away if you want me to get some photos for you.

(Mind you, XS695 has no wing tip RCV openings so it must now handle badly in the hover!)

 

Vortex Generators

10 fitted as on the Kestrels with the small leading edge extensions on their wings.

 

On the Wings... I've done some more trawling through my archives and photos appear to show that the "original wing" refitted to XP984 was like that on the Kestrels with the small leading edge extension added to it and the 10 vortex generators. I have got black and white and colour photos of XP984 in this configuration.

 

U/C Legs

Just noted that you're making the model in the hover, on which basis you probably need to drop the oleo on the main u/c leg more than it is.

I have drawings for the front and main u/c units which will help you.

 

This video shows the "Hole in the Wood" trials: 

 

Hope that helps.

 

Cheers

 

Nick

 

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