pulling the prop through on geared radial engines | FerrariChat
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pulling the prop through on geared radial engines

Discussion in 'Aviation Chat' started by snj5, Apr 20, 2008.

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  1. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
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    Russ Turner
    #1 snj5, Apr 20, 2008
    Basic question for the pros on radial engines: after a recent 1820 accident due to a failed rod that was bent, it has posed a question:
    In a geared engine, is there any value in pulling through the prop prior to starting. I did this with a direct drive 1340 for years. The mechanical advantage seems to work against bending the rod in a geared engine, and I have always heard to use the starter motor which will not bend a rod from hydraulic lock.

    Many thanks
     
  2. Bob Parks

    Bob Parks F1 Veteran
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    Nov 29, 2003
    8,017
    Shoreline,Washington
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    Robert Parks
    #2 Bob Parks, Apr 20, 2008
    After years of pulling the prop thru before a start , I have been retrained to USE THE STARTER. The leverage put on a 6 foot blade by two people can overcome the resistance of oil in the cylinder and bend a rod when the force is applied. I can't imagine the number of times that I walked the prop through on many of the " B" airplanes during and after the war. Then my DC3 pilot son told me " WRONG ". Use the starter. How I would hate to see that beautiful R1820 damged !
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  3. Bob Parks

    Bob Parks F1 Veteran
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    Nov 29, 2003
    8,017
    Shoreline,Washington
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    Robert Parks
    #3 Bob Parks, Apr 20, 2008
    The big radials are known by all to drain vast quantities of 50 weight oil down into the lower cylinders after sitting for a while. This stuff is non-compressible and applies a solid force to the pistons down there in the bottom four or five barrels when the piston tries to compress it. I can remember seeing quarts of black goo dripping out of the hole in the collector ring or the tail pipes of many airplanes after the prop was walked through for 10 or 12 blades.
    I have just finished a painting of a Curtiss Jenny JN4D for a museum in Oregon and I was talking to the museum director about running the 1917 OX5 in the airplane and he told me that it takes about ONE HOUR of preparation before you can ATTEMPT to start it. All eight plugs have to be pulled to pre-oil the cylinders, after which a multiple rotation of the engine is required, then the plugs are re-installed and torqued, then there is something that has to be done to the cooling system fluids, and.....then priming and the attempt to get it to fire which isn't always a sure bet. All this should be done when it isn't too hot, the wind isn't blowing more than 5, and there is a long clear space in front of you when you start your take-off. On a standard day the engine rated at 90HP will maybe produce 70 HP. On a hot day that output drops to 50 or 60 HP if it is in a good mood. And to think that the barnstormers would have people hanging off the airplane while they were doing their shows.
    Ride anyone?
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