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Old 20th Apr 2020, 10:23
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DaveReidUK
 
Join Date: Jan 2008
Location: Reading, UK
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Originally Posted by mustbeaboeing
Monarch B720’s sat in the hangar at Luton for a month or so, on a big check, with the fin ‘folded over’ unsupported. I suspect the earlier photo of a US KC135 (post #5) had either been just lowered, or about to be lifted by the attached crane. Unless Boeing had changed the system for the US military.
Looking at some more fin photos on the Net, it appears to be more a question of geometry rather than weight.

Here's another view of the KC-135 fin folded, captured from a USAF video:



You don't need to be an engineer to work out that, if the crane is removed without any other means of support, the fin will continue to hinge downwards until it clobbers the tailplane. Hence the crane in the photo is continuing to take the load to keep the fin horizontal (actually in this instance as a preliminary to complete removal of the fin to replace the rudder).

This photo, on the other hand, of 720 OY-DSK before it was impounded and broken up at Luton, appears to show how MAEL got round the problem:



Rather than defying gravity, you can just discern between the base of the fin and the fuselage what appears to be some kind of pad which, in conjunction with the pin attachments for the fin, maintains it in a more-or-less horizontal plane with a reasonable amount of clearance from the tailplane - it's clearly not resting on it.

The photo from Flickr rather unhelpfully claims that it was taken on October 2010 (which is obviously nonsense), so it's not clear whether the 720 in question ever flew again after the photo was taken.



We're still no nearer knowing whether the 707 shared the 720's ability to fold the fin. Given the close relationship between the two types, it might seem a reasonable assumption - but on the other hand, wth many more 707s built, it has so far proved impossible to track down photographic evidence.

Any offers?
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