A Kestrel (prototype) for a Knave

[P.1127]

2 hours ago, NG899 said:

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

 

 

Brilliant, Brilliant, Brilliant!

 

I appreciate your time in digging all of that out for me. In fact, I struggled to find it when I first set up the thread but I have spent some time in the past admiring your 1/48 P.117 conversion and it was that (amongst other things...) that inspired me to give this a go. "Thanks"... at least I think so for now haha

 

On the subject of XP984, there's some great stuff there which is very useful:

• I'll definitely take on your advice regarding the MLG and lengthen it even more than I have currently done so (if you could send me any drawings to assist it getting the length right then that would be brill.)
• The fuselage... if I understand correctly what you've written above, which can not be guaranteed, then the fuselage length of the Kestrel (inc. XP984) is NOT the same as that as the Harrier GR1 as provided by Airfix (ignoring the pitot length difference, of course). I've seen a diagram in an AIAA publication written by Fozard that the extension took place between the P.1127s and P.1127/2s (aka Kestrels). Have I interpreted this incorrectly?
• The wing... I think then that the wing as I have it at the moment is a valid configuration for XP984? i.e. no LE extensions, no vortex generators... I need to drop the flaps for displaying in the hover but that's a "minor" point for another day.
• The tailplane… so it seems that the tailplane as shown in my first post is a valid XP984 configuration? PHEW! (I still need to find another one though but there's plenty of time for that). My info here has come from a paper presented at a combined AIAA/AHS/ASEE conference on Aircraft Design by Fozard in 1990: figure 4.4 on page 8 gives table defining the span, anhedral and area of the tailplane configurations between the P.1127 and Harrier.
• ...
• The question remains in my mind though, if I've understood your information correctly, did XP984 fly or even just exist in the wing / tailplane configuration... or do I need to reconsider my options... or build it as a WHIFF? haha

Sorry if any of the above comes across as defensive or combative... it's not my intention, I'm just keen to learn (where I've gone wrong haha)

 

Interesting to read that John Farley flew XP984 in the Hole in the Woods proving exercise. I had the good fortune to meet him whilst I was a student at Cranfield in either 2008 or 2009 (I suppose it must have been 2009). Another nice link to the aircraft being modelled. I understand that the trial took place from RAE Bedford, is that right?

 

Wrt XS695 I was in fact at Cosford this past weekend with the family and some friends: a smashing day out although the lower floor of the Cold War hangar was closed for unpublicised reasons, including the shop which naturally left me gutted and took the edge off of the day! I'd noticed the lack of wing-tip RCVs on previous occasions but was encouraged to see that the replacement fairing over the stbd wing had been removed... perhaps to reinstate something more representative?! I digress...

 

One of the reasons I love this hobby is the fascination with historical aspects, it's just great to at least try and get this stuff right during a build! If you don't mind, I'll take you up on the offer of any extra info that you might be able to send me to help with the build. I'll PM you my address this evening.

 

Thanks again,

 

 

P.1127 (actual name... Jack)

[NG899]

Hi Jack,

 

Some more thoughts for you in reply to your latest post...

 

Fuselage length - Wait until you see the GA drawings I send you from Hawkers. Don't forget the Harrier nose cone was different to the Kestrel's nose, being a bit longer and mounting the pitot. Another trip to Brooklands may be needed - I doubt the length of XP984 has changed since 1964, even if other things have!

 

I don't have John Fozard's paper, so would be interested to see the diagram you have; also the tables of wing and tailplane types. I have seen some diagrams and tables of the differences, including TP spans and anhedral angles, in other publications but I've never been able to be sure if they were HS originals or other people's interpretations.

 

Intakes - Hugh Merewether's book (data provided by Chris Farara the HSA archivist) mentions that for its first 61 flight it flew conventionally with the sharp metal intake lips (of earlier P1127s), with the "7th" wing, i.e. it's "Original Wing." In September 1964 the new all speed metal intake was fitted, as shown in all the photographs I have of XP984. (This was tested on a comparison basis with the inflatable lips on Kestrel XS688.)

 

XP984's "Original Wing"

All but one of the photos I have of XP984 show it with the non-"Harrier Wing" fitted. They seem to show it with what you could call the "Kestrel Wing", i.e. one with the shallow LE extensions and 10 vortex generators fitted. (It was after it got its "Harrier Wing" that XP984 faded from the P1127/ Kestrel / TES programmes and became involved with the work of the RAE Bedford.) I think that the diagrams I have seen of the different P1127 wing types including the 7th Wing is possibly missing that small LE extension as it labelled the "(Kestrel) Swept Wing". Initially, XS688 did have such a wing as in the diagram without a small LE extension but was later retrofitted with the wing which has the small LE extension; as is on XS685 at Cosford.

 

That "Harrier Wing"

One photo I have shows the "Harrier Wing" fitted to XP984 on 5th May 1966 and the hovering trial of 230-gallon underwing tanks. Three interesting things about the "Harrier Wing" on XP984 are:

1. It has the wing tip extensions and outriggers as fitted to the P1127(RAF) and GR1

2. But, without any easily visible leading edge extensions, and

3. With NO vortex generators fitted.

 

The wing tips and outriggers are a giveaway that this is definitely not what Hugh Merewether calls the "Original Wing".

 

Tailplanes - All the period photos I have of XP984 show it with Harrier-type tailplanes, whether in May 1965 or the summer of 1966 and afterwards; so you may need to get two new ones of those... sorry!

 

Now the evidence I have is rather limited but I think that to build a model of XP984 you can use the few photos I have of it to help you finish it you will need to:

- Add the small LE extension to the wings

- Use Harrier-type tailplanes.

 

Finally, an important sentence in Hugh Merewether's book is the first one about XP984: "This was the first aircraft to Kestrel standard (apart from minor aspects...)". I think this can be taken as saying that possibly the cockpit layout and seat were as used in the Kestrel rather than the P1127.

 

I'll email over to you the first batch of what I have very soon.

 

Cheers

 

Nick

 

Edited August 15, 2019 by NG899

[NG899]

Good morning Jack,

 

Good news!  I had another look through Tony Buttler's book late last night and found theses headlines about XP984's when-built configuration and achievements in 1964 and an important photograph...

 

"(XP984)..was quite different from the first P1127 XP831. The final aircraft featured a swept wing with curved tips and in many respects came much closer to the standard HS Kestrel configuration... It was representative of the Kestrel in terms of geometry and aerodynamics (there were minor systems and cockpit differences)... The engine itself had been moved forward pithing an extended fuselage in a move intended to restore the correct relationship between the centre of gravity , thrust centre (in the hover) and aerodynamic centre (for conventional flight). XP984's wing (and the Kestrels') now had a proper streetwise tip, which was curved so the wing isobars would remain swept and roughly parallel with the main chord line."

 

25 February 1964 - On its 5th flight it records an altitude of 40,000ft and a speed of Mach 1.04.

22 May - Reached an IMN of 1.15 during a dive begun at 43,00ft.

26 May - Flown with the extended tailplane tips which gave a larger span of 14ft, i.e. the Harrier tailplanes; which, with a bob wright fitted to the longitudinal control circuit improved stick force and tailplane angle per 'g'. Increased incidence on the inboard vortex generators eliminated 'wing rocking' at speeds above Mach 0.8 (which now only existed between 0.74-.080 Mach, when before it had been present between 0.73 and 0.95 Mach).

12 June - Reached a level IAS of 593 knots, the highest yet recorded by a P1127.

Before 30 September had leading edge extensions fitted.

30 September - Demonstrated a VTO performance with the cambered lip (the metal intake lip fitted to the Kestrels, which differed from XP984's original intake lips) at least as good as that of the earlier 'standard configuration' XP831.

19 October - Reached Mach 1.12.

10 December - Outboard fences failed to cure the wing-rocking problems so were removed a few days later.

 

The Photo - I found in the book is of it from underneath showing XP984 in 1964 - from the information above some date between 26 May and 30 September - when it had:

- The 7th Wing shape as shown in the diagram with no LE extension - (Hurrah! You say.)

- Harrier-type tailplanes - (Oh no! You say.) - dating the photo to after 26 May 1964.

- Fuselage strakes

- Inline intakes, not Kestrel ones - dating the photo to before 30 September.

- Hard-point blisters under the wings, in what you'd call the inboard Harrier location

- A unique bullet-like tail-sting

- What Tony Buttler calls "Pseudo Tripartite" markings under the wings with the USAF third lower right on BOTH sides; some Kestrels had these roundels "handed" so to speak.

 

I hope this provides you with an early option for XP984. Sadly, I don't have any other photos of it than the underside one for the May-September 1964 dates.

 

Cheers

 

Nick

 

 

 

[Dave Fleming]

Tim McLelland's book on the Harrier has some useful diagrams on the P1127 including the undercarraige on the later P1127s

[P.1127]

Lots and lots of information has come my way over the course of the past couple of days, all of which I'm grateful for.

 

It's going to take me a couple of days to pick the bones out of it all but I think XP984 might have flown, albeit briefly, in the configuration that I've sort-of committed to model, phew! (more to follow on this)

 

Thanks to a section of a factory drawing of the Kestrel sent to me by Nick (NG899) I've managed to check the length of the Airfix GR1 fuselage. Despite a slight mis-scaling of the drawing from screen to printer by me, it seems as though the Kestrel fuselage length (from the drawing) does match the Airfix fuselage length... which means that I don't have to shorten it... HOORAH!

 

 

Next step is to revise the MLG based on new info received and crack on with the NLG.

 

Until then,

 

 

Jack

 

 

 

Edited August 17, 2019 by P.1127

[P.1127]

Afternoon all, I've not been idle over the last few days but, alas, I've not got as much done as I would have liked. Photos of the NLG bay with it's modicum of scratch-built detail. Needless to say that it all looks a little bit better in real life...

 

 

I've now moved onto the cockpit area attempting some scratch-building in way of adding detail to the tub and ejection seat. The Instrument Panel in the Kestrels is noticeably different than that supplied in the kit. This is my current focus and I'll post an update hopefully after the weekend.

 

The rest of the time I've been digging into the configuration history of XP984. Merewether's book has been a great help here for trying to nail the configuration. According to Merewether (who I assume to be correct!) the aircraft flew with two wing types: the "7th", or Kestrel wing and the Harrier wing. The aircraft flew with three tailplane types: the "original", an "extended" and the "production" (what I assume to be the Harrier) tailplanes. I have made enquiries as to what the "extended" tailplane looks like... the original tailplane is what I have modelled (I'm still to locate a replacement for the lost one) based on the literature, which was modified from the Harrier one in the kit.

 

The wasp in the beer?

 

Merewether's book provides a fantastic list of the aircraft's flights up until 11th September 1968 but it clearly states that the aircraft only ever flew conventionally, i.e. not vertically, with the original tailplane. My plan to model the aircraft hovering in it's original configuration is not accurate... as it never did hover in this configuration.

 

No worries... slight change of plan required I think... I may now display the model on the ground in a "just about to take-off conventionally" pose.

 

Thanks for the interest (and for keeping the pressure on),

 

 

Jack (P.1127)

[NG899]

Hi Jack,

 

If I recall correctly, for a hovering XP984, all you need to do is fit Harrier-type tailplanes.

 

Oh, and make sure the intakes are Kestrel-type metal intakes and not the original intakes it was built with.

 

Keep up the good work!

 

Cheers

 

Nick

[P.1127]

9 hours ago, NG899 said:

Oh, and make sure the intakes are Kestrel-type metal intakes and not the original intakes it was built with.

Gah... I assumed (clearly incorrectly) that the intake configuration was fixed for XP984... more research required obviously. 

 

I'll think on re. the tailplane: I've already modified the one I have to what I think is the original configuration and am trying to source a starboard half: if I come across both halves for sale I'll perhaps stick to the Harrier type.

 

In reality there's a little bit of time to finalise the configuration but I am getting itchy and wanting to glue the fuselage together... I MUST resist!

 

Thanks for your interest, 

 

 

Jack

[NG899]

If you know someone with a 3D printer I could lend you a set of Harrier tailplanes...

[P.1127]

The 1/24 scale Kestrel project lives on!

 

I've been pretty inactive over the last few months due to both family and work commitments but work has been rumbling along on XP984.

 

I've made some attempt to add detail to the cockpit and have remade the instrument panel to be more representative of a Kestrel: there were some significant differences between it and the Harrier in this regard.

 

The big news though is that I could no longer resist and I've glued the fuselage halves together... I probably should have waited but I needed the motivation of making what felt like progress! It has meant though that:

• I've now managed to make the loooooong pitot probe for the nose (this MUST NOT be glued until much closer to the end)... I was l looking forward to this bit  as it forms such an integral part of the overall look of the machine
• I've also filled in the Harrier airbrake and got that roughly blended in to the surrounding fuselage
• I've fitted the extended tail-boom (the full size housing for the anti-spin 'chute)
• I've glued in place the fin and faired in the bottom joint with the fuselage
• ... and finally I've started the mammoth task of filling in all of the dimples (rivet holes). TBF, I quite like them but they're definitely over-scale, at least depth-wise and so many had been obliterated by modifying the rest of the fuselage that the rest also had to go. For this job I had intended to use filler/primer but I was also told that Perfect Plastic Putty (?!) was good stuff so I treated myself to a tube. It's gone on well so far, sands beautifully, dries much faster than anything else I've tried and is definitely more controllable than the Humbrol filler or Isopon car body filler I had been using for the big jobs.

I've managed to secure myself the missing (starboard) tailplane half for the princely sum of £45... but it does come with an un-made Sea Harrier FRS1 kit so not TOO bad... but it still means I'm half a tailplane down... nevermind!

 

I'm hoping to be able to take some photos over the next few days so will show the progress then!

 

Thanks,

 

 

Jack

[Col.]

Your update certainly reads like impressive progress so I'm looking forward to your photos  

[P.1127]

Aaaaand finally, here are some photos taken showing the current state of play (sorry for persistent poor quality... maybe one of them is in focus?!)

 

The revised ejection seat and landing gear are not shown here: I left them in the box by mistake.

 

You can see that I have committed to the original Kestrel tailplane shape. XP984 only flew a few flights in this configuration and only ever conventionally (no hovering) but I think it adds another layer of interest to the model and was a quick and easy thing to do to the original Airfix bits. The pitot probe is (obviously) home made and is intended to be as durable as possible. It's made from snuggly fitting styrene tube of varying diameters along it's length whilst the tip is a piece of piano wire. It's not yet glued, nor will it be until just before the final coats of paint. I'll then attach it with the tiniest amount of super-glue, fill and sand the joint and hope that it doesn't get knocked too much!

 

The next job is to tidy the air intake a little more before spraying a coat of filler-primer to really see how it's doing! Once the intake is "sorted" I'll then glue the engine in place, followed by the wing. This will then allow me to tackle the revised over-wing fairing!

 

Thanks for looking,

 

 

Jack

 

 

 

 

 

 

 

Edited December 6, 2019 by P.1127