Banjo Fitting

"Banjo fitting" is trying to fit your banjo into the overhead compartment without breaking it!

(Sorry, I couldn't resist.)

Googling on 'Aerospace' and 'banjo fitting' gives a number of hits, for example:
http://www.tc.gc.ca/aviation/applications/AWD-CN/documents/US96-25-14.htm [Broken]

A banjo fitting appears to be a type of pipe fitting that is particularly good in high or low pressure applications.

 

Bascially it's a mounting system that looks a bit like a banjo (with a very short neck) - i.e. a circular frame that fits all the way round a object.

They are not only used for pipes. Some engine mounts are designed that way.

Aero engineers like giving things silly names - I know one engine mounting system usually called the "donkey's plonker". A different engine had a tank underneath is connected by a "gorilla bracket" (think King Kong with arms above head) - and the connection at the other end was called the "banana beam" (for the obvious reasons).

 

Donkey plonker? Is that another version of a dog bone?

 

Yeah, Aleph... I need details about this. I feel the need to bring it up in normal conversation, so I should know something about it.

 

You can probably work out which two senses were intended...

http://www.allwords.com/word-plonker.html

I guess it's a UK language thing.

Talking of which, a long while back we were teaching some USAF engineers about the Harrier VSTOL aircraft, in particular the vector thrust nozzles which are officially called "bifurcated pipes". As always with "English as a foreign language" terminology, the trainees were asked if they knew what it the word bifurcated meant.

Blank looks, till some guy on the back row said "Yeah. It's a pipe that's been furcated twice".

 

Oh, I knew what you meant by 'plonker'; it was the design of the engine mounting that I was curious about.

 

Something like the sketch. Best not ask why somebody (not me, honest!) thought this was a good idea.

 

Well, that just looks... weird. I still don't quite see wherefrom the name derives, though (unless it was applied to the designer rather than the design itself).

 

I can't recall seeing a banjo fitting on an commercial aircraft but I have seen them on automobiles. It is a doughnut shaped fitting that has fluid delivered to it via a tube. The doughnout is held to whatever receives the fluid by a bolt with a sealing washer; the doughnut hole is slightly larger than the bolt. The fluid comes down the tube, through to the center of the doughnut, through the center of the bolt and makes a 90 degree turn into whatever device receives the fluid. Where is it applied? I don't know. Maybe to a small aircraft's brake caliper?

Go to Google images and search for banjo fittings

 

It's a "universal" elbow. Its design enables one to hard plumb lines where there is insufficient clearance for a bend or a conventional elbow, and enables the threaded section to be tightened to spec regardess of what direction is chosen for the tube. It offers some advantages that otherwise couldn't be met by other means. Their lower profile and greater mass might also be useful where the fitting would be exposed to damages.