Hawker P.1121

[kitnut617]

Hi everyone,

I got hold of a Hawker P.1121 made by Whirlbirds the other week and even though I haven't started it, I've been studying the bits almost every night.  I've had a discussion with Trevor (Howard of Effingham) about this over the last few days too because I think I've spotted a possible error with how the landing gear is orientated.  The following is an edited version of what I wrote to Trevor

If any of you have this kit, have a look at the fuselage and the resin wheel bay openings.  Maybe some of our experts can comment but at the rear of the main gear bay there are two slots and then as you come forward there's a large space at the front. The pictures and instructions would have you fix the U/C leg at the front of the wheel bay and would insinuate that the wheel stows away in the slots. I believe this is actually the other way around.  The slots for those who don't have a kit are near the center of the fuselage, not down the sides.

I have studied numerous aircraft models that I have and how the U/C fold away, I would say the legs should be fixed at the back end of the slots, right at the rear, and as the leg retracts forward (and not backwards as the kit would have it) into the large area, the wheel would actually rotates 90 degrees to fold flat in the large area. The slots are where the leg retracts into. This would also orientate the stance of the aircraft on it's wheels better. I don't think the aircraft is supposed to sit tail down quite like it shows, it's quite odd actually.

In my opinion, the U/C arrangement is very much like a Focke Wulf Ta.183 arrangement. This was used on a number of post war designs.

Here's a photo of the parts: the wheel bay is middle bottom and the slots point to the rear of the fuselage:

http://groups.msn.com/TheWhatifandoddballm...to&PhotoID=2256

[Mossie]

Hi Robert, I've had a look at the drawings in BSP: Fighters & Secret Projects & it definately shows the undercarriage retracting backwards as the kit suggests.  The wheels rotate, resting at 45 degrees.  I'd still think the oleos would be mounted in the narrower slot though.  It's seems they've got the wheel bay section the wrong way round, can it fit either way or is does it have to be fixed in the direction marked in the instructions?

The drawings also show a pronounced tail down attitude when on the ground.

Theres a copy of the diagram on this French language site:
http://prototypes.free.fr/p1127/image/p1121_03.jpg

[kitnut617]

Hi Simon,

Well seeing that drawing, it looks like the wheel bay is the wrong way around. It would also suggest that the slots are too far inboard too.

Thanks for the drawing and when I get my books unpacked again I'll have a closer look at the BSP one.  Interesting is the wing tip tanks,  I might do mine this way as the one I'm making is going to be a LR escort interceptor (not a fighter as it will only have two Redtop missiles ) as I'm pairing it with my Concorde B.1.

Cheers,  Robert

[Howard of Effingham]

when i first saw the photograph of the P1121 mockup in BSP: fighters i did not
realise that it may have been intended to have the real thing on its undercart with
a nose up attitude.

i have the same kit as kitnut617 but have gotten further down the line with building
it. mine is currently sitting on the undercart legs and is in the process of being
painted.

i feel that production P1121's would have sat level on their undercart and as robert
says with the leg mounted in the narrow and rear part of the resin block in the kit.
on my second model, i'll also add a support strut as my backstory for the type has
on the third flight a heavy landing leading to a partial collapse and i feel for flight
#4, the undercarriage would have been rebuilt and redesigned. the size of the
main wheels also is pushing me towards modifying the undercarriage doors from
one of those hasegawa F-16D kits with the larger intake and bulged gear doors on
the extra sprues.

given that the P1121 is one of those 'nearly made' types much of the detail is
open to speculation. so here is some of mine.  ^_^

i see the type as at first a pure interceptor [20 or so aircraft] & a later and bigger
batch of about 150 as a mix of two seat trainers & a single seat LR fighter bomber
with a good secondary intercept capability. performance would definately have
been good as the aircraft would easily have been supersonic on the level and in a
way would have been of similar performance to republic's F-105 series. it would
have been produced by hawker, but in a co-production deal with handleypage.  

the first prototype [which is on my bench] will have the serial XM854 or XM548 as
one or both of these was part of a blackout block during the period 1958 to 1961.

the second will be a early production F1, in the markings of the RAF's AFDS or
Air Fighting Development Sqn in the late 1960's as a test aircraft for the AIM-7. to
make life easier, the SAM buccanneer resin detail sets are donating the weapons
pylons here.

#3, is gonna be in 43 sqn markings at leuchars in the mid to late 1980's as the
upgraded FGR2A model and should be in all over gray.

should keep me busy for a few weeks at least!  

trevor

[kitnut617]

Hi Robert, I've had a look at the drawings in BSP: Fighters & Secret Projects & it definately shows the undercarriage retracting backwards as the kit suggests.  The wheels rotate, resting at 45 degrees.  I'd still think the oleos would be mounted in the narrower slot though.  It's seems they've got the wheel bay section the wrong way round, can it fit either way or is does it have to be fixed in the direction marked in the instructions?

The drawings also show a pronounced tail down attitude when on the ground.

Theres a copy of the diagram on this French language site:
http://prototypes.free.fr/p1127/image/p1121_03.jpg

I've been looking at this drawing again Simon,  I'm not sure that this is the P.1121.  To start with the wings are the wrong shape (the P.1121 drawings I've seen the wings are all like an enlarged Hunter wing) and also the tailplane is mounted on the fin, the P.1121 has it's tailplanes mounted on the lower fuselage and below the tailpipe.  They also have dyheadral.

Robert

[Zen]

I think thats the P1116 which sits intermediate between the P1103 and the P1121.

[Mossie]

I've just looked over it & Zen's right, it's the p.1116, the predecessor to p.1121.  The wing & tail are different, but the fuselage & undercarriage instalation are identical to the p.1121.

[Glenn Gilbertson]

Typical - I finally finish my Maintrak P.1121 after years on the back burner, then spy the Whirlybirds upgrade at Telford!   If the store size is correct, the nose-up undercarriage stance gives more clearance.
Would like to add pictures if I was not too old and daft to work out how - drag'n drop gives a security setting error message, "add file attachment" locates the picture in "browse", but what do I do then to insert the picture?
All advice greatfully received.    

[jcf]

I've been looking at this drawing again Simon,  I'm not sure that this is the P.1121.  To start with the wings are the wrong shape (the P.1121 drawings I've seen the wings are all like an enlarged Hunter wing) and also the tailplane is mounted on the fin, the P.1121 has it's tailplanes mounted on the lower fuselage and below the tailpipe.  They also have dyheadral.

Robert

Yep not the 1121, however Barrie Hygate's 1121 drawings have the same landing gear arrangement as the kit and the 1116 drawing...or its probably more correct to say that the kit is the same as the drawings. Its very likely that the Hygate drawings were used to design the kit.


Cheers, Jon

[kitnut617]

Yep not the 1121, however Barrie Hygate's 1121 drawings have the same landing gear arrangement as the kit and the 1116 drawing...or its probably more correct to say that the kit is the same as the drawings. Its very likely that the Hygate drawings were used to design the kit.


Cheers, Jon

I have a set of those drawings and that is what got me thinking about the drawing Simon posted.

I've been studying all these drawings over the weekend and being a detail draftmans I've begun to realize that there's actually no room for the wheels to fold away to the rear.  The section views just don't provide for it and the wheels plus the legs will definitely not fit in the small slots as shown.  I am more and more convinced that my initial feelings that the legs were mounted at the rear of the slot at sometime in the design by what I see in the drawings.  There's no disputing that the set of drawings that are available show the U/C at the front of the bay, although they could have been updated by the drawing office at the time just to see what the outcome would be.

I seem to remember reading somewhere that the Gyrone was quite a heavy engine and my feelings are that maybe the final product of the engine ended up lighter than first estimated which could be a reason for the legs to be moved forward.  And also that the project was cancelled before any U/C was fitted to the section of fuselage that was built (I have seen a photo of this part which still exists in the RAF Museums Reserve Collection)  This could have been in part of a re-design for the U/C bay which would have entailed.  Just my observations of what I see.

Robert

[Zen]

Sorry kitnut, all my information says the wheels stowed rearwards, which is in a bay behind the engine under the jetpipe and in front of the aft fusilage fuel tank.

The legs attatchement point seems under the rear of the engine, no surprise, as this makes the mounting and that part of the fusilage naturaly strong, having to take the weight of the engine. So the designers killed two birds with one stone, or should we say with one strong frame, the other being at the front of the engine and mating neatly with the front wing spar. A very neat solution, very Hawkers at their best.

There is also the issue of the trailing edge surfaces and their interference with the U/C doors, having the wheel bays forward does'nt solve this, if anything I suspect it makes things worse.

I have no idea why anyone would think the wheels ever stowed forward, not the P1103, or P1121 have that.

[Howard of Effingham]

Sorry kitnut, all my information says the wheels stowed rearwards, which is in a bay behind the engine under the jetpipe and in front of the aft fusilage fuel tank.

hmm, i is gonna disagree here or at the very least say that its open to interpretation.

on my first P1121 i have the u/c legs as per the kit, but on the second and subsequent models,
the undercart will be retracting forwards with the mainwheel stowing in the large
and open part of the resin block in the kit. i have wondered if the open part of
the resin block would be better off mounted the other way around but because i
could see the movement of the u/c doors in this arrangement would foul the wing
trailing edge am leaving it as it is.

[Mossie]

Sorry guys, I'm with Zen on this one.  I've only got BSP & Project Cancelled to go on, but it seem that the undercarriage arrangement didn't change from the initial p.1103 designs through to the p.1121.  The only change came in the p.1123, the designs last gasp to adapt it to TSR2 requirements.  In order to cure the problem with the undercarriage/flap interferance, the legs retracted backwards into kuchemann fairings in the wings.

I can understand that there may have been attempts to change the undercarriage to enable them to be down with the flaps, but there doesn't seem to be a single Hawker design that had undercarriage retracting forwards.  Sydney Camm liked simple, solid engineering & the undercarriage retracting in this way would fit well with his design ethos.

What I will say is that Howards right, it's open to interpretation & to go with what you feel, we could discuss this for weeks without a definitive answer.  If I was building the kit, I'd personally do it with the wheels backwards, but it's a whiff, the machine never flew, who knows!  If your personal conviction is that the wheels went forward, do it that way.

Glenn, would love to see your pics & interpretaion of the kit.  The easiest way to post pictures is to open a Photobucket.com account, or at some similar image hosting site.  It's free & fairly easy to do.  If you need any help, PM me & I'll give you some pointers.

Simon.

[kitnut617]

After reading all the comments and looking at the drawings again, it would appear that the main wheels would have to go from pointing outwards when deployed to pointing inwards when retracted, that is they have to turn a full 180 degrees as they go through the motion.

For a while I couldn't get my head around how they would do that as the U/C doesn't appear to have any mechanical or hydraulic system to do that.

But now I think I'm having to eat a bit of humble pie because I've just printed the drawing Simon posted nice and big (where I was having difficulties before getting it to print on a 11x17 sheet of paper, but somehow manage to do it) and it reveals some interesting info and all of a sudden I see how it all works.  

There's some other factors that I hadn't taken into account either,  Zen rightly points out that the U/C is attached to a very large bulkhead which also serves as the rear spar attachment point (about halfway down the engine actually), this being at the forward end of the wheel bay, then halfway through the wheel bay, where the big doors change into little doors, is another bulkhead which shows the small slot for the leg of the U/C (this being the rear engine mount too).  This is also the point where the rear fuselage attaches to the center fuselage (half the U/C bay is in the center section and the other half in the rear section) and I think is how the engine is removed.  So an U/C mount behind that bulkhead wouldn't work.

Looking at Simon's drawing shows how the U/C hinge is orientated, which is very simple once the geometry is worked out and doesn't involve any mechanical or hydraulic system to turn the wheel inside out.

Sorry Trevor for leading you up the garden path but it does now appear that the undercarriage is at the front of the bay, but it doesn't explain how the wheel gets into that little slot, I would surmise that the small doors should have a larger section to it, at least the size of the wheel.  There should be though, a space set to conform to the lower fuselage sides at this point the size of the wheel as the wheel at the point of entering the bay is practically flat to the side of the fuselage.   There is no problem of the flaps hitting this door as in the front view on the drawing it shows the flaps in the down position and they are well clear of the fuselage or any door that might be open.

Robert

edit:  also what threw me off was the resin part in the kit.  I realize now that the slot should be running 90 degrees to the way it is in the casting and that there should be at the rear end of the slot a larger pan shaped recess which would accommodate the wheel, this being set at about 45 degees to the vertical. This recess should be deeper than the slot depth because the slot only accommodates the leg and the leg runs very close to the fuselage skin.  If anyone has drawings or the kit of the XB-42/43, this shows how this should work.

[Glenn Gilbertson]

It'll never win a prize, but it was fun. 6 sqn. seemed right, and that air intake just called for a sharkmouth!
Hope the pictures work.
IMG]http://i165.photobucket.com/albums/u68/glenngilbertson/IMG_5566crop.jpg[/IMG]