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Lancaster MLG doors - a question


Scott Hemsley

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Specifically, I'm working on the 72nd Airfix Lancaster B.II, but I assume this question could be about any version;

 

On the kit gear doors, there's a 'jack' molded to each one that IMO, holds the doors wide open at an angle that's far more exaggerated than one would normally expect.  When I consulted the Lancaster photos I've amassed, on file .... I only found one period photo of a Lancaster on the ground that had visible proof that these 'jacks' did exist, while all the rest of the photos without these in place had the gear doors hanging open at a much more 'normal' resting position. 

 

I'm wondering if these 'jacks' weren't actually a permanent part of the gear doors (as Airfix would have you believe), but rather supports for the gear doors, manually placed there by groundcrew to support the gear doors for ease of maintenance/inspection or similar.

 

Scott

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I used to have some shots of the Australian War Memorial's "George", taken when it was possible to get up close and personal with it. They included shots of the undercarriage. Sadly they went south when my computer had a major non-cope a couple of years ago. They showed those jacks in place, but from memory there was nothing to indicate whether they were a permanent or temporary fitting.

 

I've since seen several museum aircraft in the UK, including "Just Jane" at East Kirkby, and (again from memory) all had the jacks in place. I have read somewhere that their purpose was to open/close the gear doors as the gear extended/retracted, and would surmise from that that they were a permanent fixture. Whether or not Airfix got the lengths right in their kits is, of course, another question again!

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I've since seen several museum aircraft in the UK, including "Just Jane" at East Kirkby, and (again from memory) all had the jacks in place. I have read somewhere that their purpose was to open/close the gear doors as the gear extended/retracted, and would surmise from that that they were a permanent fixture

Makes sense. To be honest, I'd heard that as well, but it wasn't something others picked up, so I began to question it.  I also noticed that no other mfgr that I'm aware of, including Airfix with their 80's offerings, included these 'jacks'.

 

Quote

Whether or not Airfix got the lengths right in their kits is, of course, another question again!

I bet that's it.     OOTB, the kit has the gear doors spread to their max. so that the 'side' of the gear door is almost parallel to the undersurface of the wing or so it appears, whereas period photos tend to show them open, but hanging down/open at a point much closer to the width of the wheel well - that's what I meant by the use of 'normal' in my OP.   

 

I think I'll shorten them on my kit.....

 

Thanks Admiral Puff.

 

Scott

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@Scott Hemsley the “jacks “ as you describe them are simple articulated rods linking the undercarriage doors to the legs.  As the legs retract the rods initially push the doors outwards and then pull them in to the closed position as the legs reach the upward/rearward limit of their travel.  If you can find the BBC Perpetual Motion episode on the Shackleton there’s a short sequence showing one of 8 Squadron’s AEW. 2s taking off from almost dead ahead that illustrates the sequence quite nicely.

 

 The same system was used, surprise, surprise, on the York, Lincoln, Shackleton MR. 1 and 2 and probably Tudor.  I’ve not built any of my Airfix Lancasters yet to see how well, or not, the linkages hold the doors in the right position.  Interestingly the Shackleton kits don’t depict them.

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The Revell Germany kit from 2007 had the door operating links too. 

 

Given the location, the dark colours and deep shadow surrounding the undercarriage I'm not surprised they don't often jump out in pictures.  I have a downloaded one of R5727, the pattern example for Victory production, in brilliant sunshine at Dorval with the links in plain view.

 

As I think about the mechanism, what could be a simpler way to manage the doors?  They're just doors, they don't actually have a complicated job to do.  They go up, they come down. :) So no screwing around with little motors or anything else, just a simple unpowered link.  Another little detail to look for the next time one gets to Hamilton or Windsor.

 

A plug for CH2A, now renamed Canada Aviation Museum, at Windsor.  Work on FM212 is really moving ahead and much of it can be viewed up close.  It won't be long before a lot of the innards are hidden from view.  The natives are friendly and any time I've been there the guys are only too willing to answer good questions.  They also maintain a really good Facebook page with plenty of detail pictures.  A first rate job being done.  A link:

 

https://canadianaviationmuseum.ca/

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6 hours ago, RJP said:

 

As I think about the mechanism, what could be a simpler way to manage the doors?  They're just doors, they don't actually have a complicated job to do.  They go up, they come down. :) So no screwing around with little motors or anything else, just a simple unpowered link.  Another little detail to look for the next time one gets to Hamilton or Windsor.

 

There is a quote that,I think is attributed to Roy Chadwick "We are simple people who design and build simple aeroplanes to be flown and maintained by other simple people."  I sometimes wonder what he'd make of our modern plastic computers with wings?

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The mechanism was a Dowty freefall gear mechanism.

Just gravity!

This has to be taken in account.

Landing procedure in case of emergency needs twisting the a/c to get the gear down.

This is just part of your answer.

The door including all fixed leverages will stand in the vertical position from center of gravity of the unist.

Think simple, as it is untill today the dictum of all Dowty products!

Happy modelling

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Hello, dov

These days that is industry standard in emergency situation. Even with total failure of hydraulic/electric/pneumatic system pilot can lower and lock undercarriage just by unlocking it and then let gravity and aistream do the rest. Cheers

Jure

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That photo from the rear of VR*A & that l/g diagram really removed the guess-work re the angles of the gear doors.  Many thanks, Chris!!   Those two items combined do, in my mind, confirm that Airfix did get the length of the 'jacks' wrong - as Admiral Puff suggested may be the problem.

 

Once again, the BM community came through.  Thanks gentlemen.

 

Scott

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An Airfix Lancaster II completed earlier this year did not indicate the problem you encountered.

 

I have got it down from the shelf and I cannot see the undercarriage doors looking different in angle from the photos above or from a lot of Lancaster references on the bookshelf.

 

Maybe their is variance in mouldings during production?

 

Michael

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Hi!

In the manual figure it looks like gear door end of the retraction strut has a sliding connection?

If so, moving the door side end fitting back-forward the effective length of the retraction strut changes and thereby also the door "hanging" angle? Hard to explain in words.

 

Cheers,

Kari

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