Bristol Blenheim Bomb Carrier Inspection Doors

[Walter Lindekens]

An interesting feature of the Bristol Blenheim and which has apparently been missed out on by all kit manufacturers and most draughtsmen are the two oval bomb carrier inspection doors located on each side of the aircraft, just above the outer bomb door hinge line.

 

A.P.1530B :  “Immediately above the hinge longitudinal support member of the outer doors are two hinged inspection doors which are secured by turnbuttons engaging in the plate brackets (12) mounted on the longitudinal support tubes (13)”.    Nrs 12 and 13 referring to below illustration from same manual.

 

 

This photo has been taking looking forward and you can see that the front inspection door is open.

Those doors rarely show up clearly in photos as they’re always in the shadow of the wing but once you know what you’re looking for it gets easier!

 

On this photo of a Finnish Blenheim you can just about see the oval outline of the doors but the piano hinges at their bottom stand out clearly:

 

Another snip from a Finnish photo shows the two turnbuttons at the top:

 

 

On this poor quality photo of an RAF Machine being bombed up you can see the two doors are open and are resting on the bomb door:

 

 

And this is one of the best photos I found, clearly showing the inner detail of the opened front inspection door.  Note the longitudinal stiffener (looks like a section of the type of stringer used in the fuselage construction):

 

 

Finally another photo of an RAF Blenheim where you can just make out the two inspection doors above the bomb door hinge line:

 

 

In 2001 Czech draughtsman Martin Lébl produced a set of scale drawings of the Finnish Blenheims for REVI magazine and  they are by far the best drawings I have ever seen.  Although the Finns produced some of the their Blenheims under licence from Bristol’s and which differed in details from the British built machines (it appears they did away with those inspection doors for one), they also employed a number of Bristol built aircraft and thankfully Mr Lébl covered these as well and so we now have a drawing of those elusive doors!

 

This is a snip of that drawing,  port side shown, starboard side identical as far as the positioning of the oval inspection doors goes:

 

 

These inspection doors were a feature of all Blenheim marks, I, IV and V and also of the Bolingbroke Mk IV as they are clearly referred to in the Canadian air publication of the latter.

 

So why has just about everyone missed out on those inspection doors?    As mentioned above, they hide in the shadow of the wing and don’t show up very well or not at all in most photographs.

Then, all kit manufacturers and draughtsmen will have based their drawings on the surviving machines which are mostly exhibited as Blenheims but which are in fact all Canadian built Bolingbroke airframes.   The issue of the upper nacelle shape springs to mind :)!

 

The Bolingbroke Mk IV was followed on the production line by a general trainer version, the Mk IVT.   As opposed to the bungee operated bomb doors used by its predecessors, the MK IVT had electrically operated bomb doors.    My theory is that they did away with the inspection doors as the electrically operated doors where much easier to open and close than the bungee operated ones.    And a list I found of preserved Boly airframes in museums around the world shows these are in fact all Mk IVT’s.   That might just explain…

 

All photos shown come from various sources and are reproduced for research purposes only.

 

I've been meaning to share this information for quite some time now so I hope my fellow Blenheim enthusiasts will find this of interest!   

 

Cheers,

Walter

[Ivor Ramsden]

An interesting new bit of information. Thanks Walter. I've sent you a PM