Blackburn NA39, intakes, length and radome questions

[John R]

Post #74 corrected

John

[Space Ranger]

15 hours ago, Graham Boak said:

Station 0.00 will either be the original tip of the nose or a chosen point ahead of the design.  If there has been a change in length then there should be either an oddity in the station numbers, or differences in station numbers between prototype and production.  This would upset the production jig plans as well as the area ruling, which is carried out from the tip of the nose to the top of the tail. Neither makes a stretch impossible, as on the Tornado ADV, but evidence for this should be visible.

I thought it odd myself that the station numbers are continuous, without any discontinuities as might be expected from what we know about the changes in length from prototype to S.1 production. But the drawing is of an S.2, so it may be that Blackburn's engineers simply re-numbered the S.2 fuselage stations in order to eliminate any confusion, both on the production line or in service. I've never been a design or production engineer, but that's what I'd have done.

[canberra kid]

5 hours ago, Space Ranger said:

I thought it odd myself that the station numbers are continuous, without any discontinuities as might be expected from what we know about the changes in length from prototype to S.1 production. But the drawing is of an S.2, so it may be that Blackburn's engineers simply re-numbered the S.2 fuselage stations in order to eliminate any confusion, both on the production line or in service. I've never been a design or production engineer, but that's what I'd have done.

That was my thoughts too

John

[Graham Boak]

I've never been a production engineer either, but they do have an ingrained resistance to change, because change costs.  Renumbering all the stations would require renumbering all the production drawings, no small feat, and would introduce confusion by having identical parts between the first five and later aircraft with different numbers, and different parts with the same numbers.  In the older system, a stage (e.g.) 5A would have been introduced between stages 5 and 6.  Where the station numbers are based on distances from a fixed datum, then all the stations aft of the change would remain the same but those forward would have to change, being closer to (or even ahead of) the datum.  It is however possible that early aircraft were not built on production jigs anyway, so the numbering system would then be free to be re-established for all production aircraft.  Never having worked at Brough, I've no iidea of their system.

[Seahawk]

On 3/28/2020 at 2:08 PM, John R said:

Regarding Roy Boot as 'the authority' may not be entirely sound as I remember a reviewer remarking, when the book was first published, that there were a number of errors.

Depends on the reviewer.  Do we take his word over that of a Brough design engineer?  Are they genuinely "errors" or just not what the reviewer expected to read?  I've no horse in this race but there are a number of people on this site whose opinions I would esteem over those of most reviewers in the aviation mags, let alone modelling mags, nowadays.

[David Womby]

FWIW, the engineer I found who worked on the NA39 development at Blackburn sent me an updated opinion including: 

 

"a gentleman named Colin Cruddas, same age as myself (86) who worked with me as a development engineer at Holme on Spalding Moor and asked him the same question you asked. He had responsibilities for the fuel system and in flight refuelling. Like me, he does not remember any addition to the fuselage length.  However, we both realized that we arrived at Holme on Spalding Moor after XK491 was added to the 20 a/c development group and may not have realized that such an extension could have occurred during the build stage without our knowledge. We both have a healthy regard for Maurice Allward and his book and trust him. (Colin is a book author himself having published a number of British Aviation books). Therefore, with humility I retract my certainty about there being no extension to the fuselage. "

David

[John R]

The plot thickens/unthickens... now where do we go?

I tried emailing the FAA Museum but it (surprise) is closed

For those interested Roy Boot's book 'From Spitfire to Eurofighter' is available cheaply (£0.81 upwards) from

https://www.abebooks.co.uk/book-search/author/BOOT,-ROY?cm_sp=brcr-_-bdp-_-author

John

 

2 hours ago, Seahawk said:

Depends on the reviewer.  Do we take his word over that of a Brough design engineer?  Are they genuinely "errors" or just not what the reviewer expected to read?  I've no horse in this race but there are a number of people on this site whose opinions I would esteem over those of most reviewers in the aviation mags, let alone modelling mags, nowadays.

I do not remember what they were but there was at least one, a date, that presumably could be verified. There are always 'typos', slips of memory and unverifiable details as evidenced by threads like these on BM. However I do agree that reviewers can be subject to the same human failings as the rest of us.

John

[David Womby]

 

20 minutes ago, John R said:

The plot thickens/unthickens... now where do we go?

Short of finding an actual official, Blackburn or MoD,  document from the period in question or an engineer who was there and remembers, I think we are left with the mooted fuselage extension first appearing in XK491 as being unproven.  I, however, believe there was such an extension and am about to cut out a suitable chunk, aft of the cockpit,  to build NA39 XK486 (or 487 - I want to do a blue and white one).  I will also be shortening the radome and changing the airbrake strakes.

 

David

[ChocolateCrisps]

12 minutes ago, David Womby said:

Short of finding an actual official, Blackburn or MoD,  document from the period in question

Looks like Kew has no shortage of documents on the NA.39, but whether any of them mention the fuselage extension is another question (and it'll be months before anyone can check!)

[David Womby]

4 minutes ago, ChocolateCrisps said:

Looks like Kew has no shortage of documents on the NA.39, but whether any of them mention the fuselage extension is another question (and it'll be months before anyone can check!)

Intriguing and, given current circumstances, frustrating😒

 

David

[ChocolateCrisps]

Just had another thought - the dimensions of the Blackburn B.103 are given in British Secret Projects 2, and the length is given there as 61ft 6in. Obviously this is only the provisional length given in the brochure, but it may have carried over to the early prototypes.

[David Womby]

13 minutes ago, ChocolateCrisps said:

Just had another thought - the dimensions of the Blackburn B.103 are given in British Secret Projects 2, and the length is given there as 61ft 6in. Obviously this is only the provisional length given in the brochure, but it may have carried over to the early prototypes.

Fits very nicely with 22.55 inch addition, doesn't it?  Would bring overall length to 63' 4.55".   Prod Buccaneers are described as 63' 5".  Coincidence?

David

[canberra kid]

11 minutes ago, David Womby said:

Fits very nicely with 22.55 inch addition, doesn't it?  Would bring overall length to 63' 4.55".   Prod Buccaneers are described as 63' 5".  Coincidence?

David

That sounds like a good hypothesis to me David.

John

[ChocolateCrisps]

48 minutes ago, David Womby said:

Fits very nicely with 22.55 inch addition, doesn't it?  Would bring overall length to 63' 4.55".   Prod Buccaneers are described as 63' 5".  Coincidence?

Sounds like it fits pretty well! We can't be sure without more information, but it all appears to tie up quite nicely!

[John B (Sc)]

Maurice Allward's book states, on page 36, that a 13" increase in forward fuselage length was made from the sixth aircraft (that would be XK491) to assist equipment balance and stowage.  The fuselage manufacturing breakdown certainly would make an increase in length in the blue area shown earlier fairly easy to do. 

[canberra kid]

1 minute ago, John B (Sc) said:

Maurice Allward's book states, on page 36, that a 13" increase in forward fuselage length was made from the sixth aircraft (that would be XK491) to assist equipment balance and stowage.  The fuselage manufacturing breakdown certainly would make an increase in length in the blue area shown earlier fairly easy to do. 

That sounds interesting.

John

[David Womby]

Just now, canberra kid said:

That sounds interesting.

John

 

3 minutes ago, John B (Sc) said:

Maurice Allward's book states, on page 36, that a 13" increase in forward fuselage length was made from the sixth aircraft (that would be XK491) to assist equipment balance and stowage.  The fuselage manufacturing breakdown certainly would make an increase in length in the blue area shown earlier fairly easy to do. 

How the heck did I miss that!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[John B (Sc)]

It took me several readings David - I thought I'd seen a measurement somewhere.

 

John (canberra kid) ; Looking at your diagram either a length increase within the blue area or  a small insert just behind and on the line of the red diagonal would fit the manufacturing breakdown. Probably the red line build would be easier.  

 

Like you David, I still have several of the old Airfix Buccaner S1 kits and have long been intrigued and exasperated at the poor depiction of the exhaust area. Having seen many of the S1s flying from Lossie in the old days, improving that kit still attracts.   I was acquainted with one of the early Buccaneer pilots from the Intensive Trials Unit, Mike Hornblower, who many years afterwards still had his ancient Bentley.

[David Womby]

6 hours ago, David Womby said:

Fits very nicely with 22.55 inch addition, doesn't it?  Would bring overall length to 63' 4.55".   Prod Buccaneers are described as 63' 5".  Coincidence?

David

Actually, I am thinking that must be coincidence because presumably the overall increased length must include the change to the prod radome as well as any fuselage insert aft of the cockpit.

 

David

[David Womby]

45 minutes ago, John B (Sc) said:

Like you David, I still have several of the old Airfix Buccaner S1 kits and have long been intrigued and exasperated at the poor depiction of the exhaust area. Having seen many of the S1s flying from Lossie in the old days, improving that kit still attracts. 

Maybe it's all those cute working features in the kit that attracts us, John?  Folding radome, folding wings, retracting nosewheel and arrestor hook (but non-moveable doors and non-moving main undercart) and the famous  rotating bomb bay.  I know I thought that kit was so cool when I first got one in the late 60s.   The exhausts are  basically right for any airframe up to XK523.  The kit is based on the 6th prototype XK491 and not an S1 at all.

 

David

[John B (Sc)]

You may well be right David about the attraction of moving parts.   It was a feature, way back.

 

 I recall seeing these machines taxying past at Lossie, unfolding their wings as they prepared to turn onto the main runway, I thought it terrific, as a youngster back then. I also used to see the aircraft in your avatar picture occasionally, though to my disappointment Airfix never made a 1/72 Sea Vixen. 

 

I think the best moving parts model I ever had was the old Monogram Avenger, with rotating turret, elevating gun, opening torpedo bay, folding wings - showing that impressive Grumman system - and I think working undercarriage as well.   

Edited April 3, 2020 by John B (Sc)

[Space Ranger]

3 hours ago, David Womby said:

Maybe it's all those cute working features in the kit that attracts us, John?  Folding radome, folding wings, retracting nosewheel and arrestor hook (but non-moveable doors and non-moving main undercart) and the famous  rotating bomb bay.  I know I thought that kit was so cool when I first got one in the late 60s.   The exhausts are  basically right for any airframe up to XK523.  The kit is based on the 6th prototype XK491 and not an S1 at all.

 

David

What a coincidence. I was going through some old issues of RAF Flying Review looking for further information on the fuselage stretch, when I came upon this, from the October 1960 issue:

 

 

And this, from the December 1960 issue:

 

 

And my nominee for the worst box art of all time is this, from a US release of the kit. Note what appears to be a Mitsubishi Zero falling in flames:

 

[Pete in Lincs]

Some years ago on Hyperscale? there was a thread for bad box art. There were some shockers out there.

[John B (Sc)]

Thanks Space Ranger. A Flying Review model discussion that predates  W R Matthews!  Those Airfix ads encouraged a lot of modelling - rather sadly I realise that over the years I made all of the models in that ad ! I think the level crossing and the Bentley lasted longest!

[general melchett]

Hi all, I've been asked by JohnR to have a look through all my reference material on the Bucc/NA.39 and see if I can shed any light on the length conundrum between the pre-production NA.39 and production S.1. Like many others I don't like using photographs to compare things as there are just too many variables at play to draw an accurate conclusion. However, just for the sake of it I'll include a few here. The nearest comparison images I have are these. The upper is the fourth pre-production machine (XK489) and lower the eighth (XK524) and although the angles are not identical and taken at the same distance there does appear to be an obvious disparity between the two intake lengths, with XK489 seemingly longer. I agree that the Allward book is excellent and he does refer to a 13 inch length extension incorporated into the design from the sixth aircraft on, in other words between the aircraft shown in the images here.

 

Scans taken from old book and magazine articles.

 

 

 

 

 

Also, a bit of a giveaway of an increase is the difference between the distance of the trailing edge of the nose-gear bay door and the leading edge of the intake, with the NA.39 (XK486, first pre-production aircraft) being almost in line, vertically speaking. Interestingly, it would seem that the vertical line between the rear of the door and the angled central canopy 'bar' is the same on both aircraft leading to the conclusion that the intake 'cones' were indeed of different length (the roundel having been repositioned back slightly on the production S.1 giving the illusion of a similar distance between it and the intake lip). 

 

 

Hope this helps.

 

Melchie

 

 

 

 

 

Edited April 4, 2020 by general melchett