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Old 09-26-2018, 03:44 PM   #289
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Join Date: Jan 2018
Location: Tocumwal, NSW, Australia
Posts: 1,184
Default Re: tell a Model A related story

# 4 Incident north of Deniliquin NSW. Late 1980ís.

I had owned a radial Airtractor powered by a Pratt and Whitney R1340. R meaning radial, (9cylinder) and the numbers meaning cubic inch capacity. The R1340 has a large crank, probably 3 and half inch diameter by memory. I replaced this aeroplane with the biplane Agcat, power by a Pratt and Whitney R985 which has a 2 and half inch crank, again by memory. Keep that in mind.
It is or was anyway, common practice to do flat turns around obstructions such as power poles or trees. An out of balance rudder turn whilst keeping the wings level. Slightly uncomfortable.
Gyroscopic effect is when a spinning mass acts 90 degrees from the input. By example donít you notice when shift direction of a powered up angle grinder the shift in the machine is not what you applied? If you turn it horizontally it twists in your hand. Other examples can be illustrated when you lift a bicycle front wheel, spin wheel and turn handle bars, the bike wants to lay over. Now thatís a long explanation isnít it.
Both the R1340 and R985 have large propellers attached to their crankshafts and gyroscopic effect applies here. A rapid flat turn puts enormous pressure on the crank and components in the crank case including the con rods. (Again at 90 degrees to the input.)
I recognised this and keeping in mind the R985 has a smaller diameter crank I modified my flat turns but I think too late.

Now fast forward.
I was spraying a rice crop, spray height about 6 feet. Just the moment I lifted for the return run I heard this fihh fihh fihh noise. I figured I had a cracked cylinder head which makes the same or similar noise. I climbed and turned left towards a strip only 500 yards away. I started to loose power and pushed the throttle open. She quit. Even the propeller stopped rotating. Well I couldnít make the strip and all the ground nearby had be worked into check bank contours for past rice crops. I had no where to go. One can think fast and clearly - believe me. There was a small channel infront and I figured Iíd bounce over that so I let the aeroplane hit the ground hard and pulled back. Yes it worked BUT on the other side of this channel was a suspension fence nicely hidden with high grass and the weed ďPattersonís curseĒ. (it was springtime) That pulled me in. The immediate deceleration to a stop and stationary turn to the right was most unpleasant. So was my view of my aeroplane because it was badly damaged. If I had seen the fence maybe I would have turned but would have messed up the aeroplane on those check banks and probably over turned. I donít know.
I donít recall the year but I do recall the date. My birthday. The aeroplane was rebuilt and returned to service. I quit doing big input flat turns.
I ended up with 3 Agcats and the farmers loved them. Slow and able to get manoeuvre in difficult places. I did sell off 2 when I purchased a turbine Airtractor. I also bought an eastern block Dromadier which gave me nothing but pain and I grew to hate this aeroplane.
I know many things,
But I don't know everything,
Sometimes I forget things.

And there are times when I have a long memory. is offline   Reply With Quote