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Milt
24th Sep 2004, 00:58
The Case of the Bent Connecting Rod

Late in the last century Ron Green presided over the Down Under Flight Test Unit of the RAAF which had in its fleet a flock of the last five irreplaceble Gooney Birds all heading for extinction.

Ron just had to see them all in the air together for the last time and had barely enough pilots for the purpose. But launch them he did to the delight of those who had been tendering to their needs so affectionately.

The pilots did their best to take out the raggedness from their formation with gross throttle movements to which the old birds were not too accustomed. One of these wild throttle movements defeated an engine's prop governor to the extent that the poor bird sounded a groan of overspeed protest because of the pain it was feeling..

All came back to roost with one poor Gooney writhing in pain. She was carefully taken to sick bay for a diagnosis before a major operation on her innards. The surgeons poked around until they found that all was not as it should be and followed through with an organ replacement.

The removed bent engine connecting rod was fashioned into a souvenir for presentation to Ron.

Now there must be some highly skilled engineer PPRuNers around who can tell us pilots something about the aggro that can be heaped on to poor innocent connecting rods of a radial engine in conditions of some overspeed and high boost.

411A
24th Sep 2004, 03:10
In my experience with large radial engines (CurtisWright R3350 turbocompound series, P&W R2800CB series), the Bifler pendulem dampers (crankshaft counterweights) are the problem, with overspeeds.
These counterweights are there to dampen torsional vibrations, and during gross overspeeds (sometimes not so gross as well) these dampers can become 'out of phase' with the rotational forces, causing bent/fractured con rods.
Oftentimes, the master rod bearing is also damaged, which leads to abrupt engine failure...expensive.:{

Now having said this, my experience with these large radial engines was all too brief (the chief pilot of one operator I was destined for, tried a short field landing with a 1649A Constellation, which tore the gear off about a week before my type rating ride...damn), so I stand to be corrected by those with better ideas.

Additional information can be obtained from the website..
www.enginehistory.org

Loose rivets
24th Sep 2004, 05:06
Bent con-rod? Kah!, in my day we were expected to fly with all the con-rods bent, the counter-balance weights all centrifuged off, and our feet hanging out where the floor used to be...what's amatter with the younger generations?

Seriously though...or at least fairly seriously, I was visiting a small field just north of Austin TX and happened across a book which I have always regretted not buying. It was dedicated to extreme...er, occurrences on the DC3/ Dak. It was of particular interest to me as my first job and later my first command, was on type.

It showed the usual run of photos and text about coming back with the tail shot up, no undercarriage etc., but towards the end there was a picture of the leading edge of the stb. Wing looking like it had been opened with a can opener. The prop of another Dak had chomped away at it! The ultimate picture was of one with the majority of the port wing - outboard of the engine - totally missing. Somehow they had got back after hitting a mountain. The caption read simply more or less I bet this got their attention'

if anyone has a copy of this, I would appreciate the details so that I can at last get a copy LR