Handstarting the Douglas B-19

Discussion in 'Aviation' started by Graeme, May 23, 2009.

  1. Graeme

    Graeme Well-Known Member

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    Found this in an old magazine today. Caption reads...

    Looks like rope burn waiting to happen. Centripetal force removed the ropes once started? Did any warplane engines of WWII have to be hand started?

    [​IMG]
     
  2. HoHun

    HoHun Active Member

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    Hi Graeme,

    >Did any warplane engines of WWII have to be hand started?

    I don't believe any of the powerful engines were hand-started, if you discount devices like the DB 601's hand-cranked inertia starter.

    Note that the quote doesn't actually mention hand-starting, but merely turning the propeller. This appears to have been standard operating procedure, mainly to ensure that there was no "liquid lock" present in an engine, resulting from oil seeping into the bottom cylinder, that would prevent the engine from turning (unless done with sufficient force to break something, as the stater motor could).

    From what I'e read, one or two crewmen were usually enough to turn the engine, so the picture above seems a bit crowded - perhaps because everyone wants to be featured on the photograph. Enough crewmen pulling at the same time might also be able to break something ...

    The practice seems to have become unnecessary only post-WW2 when the starter motors were equipped with reliable clutches to disengage them if the torque became too high. It might be that the wartime engines were thus equipped too and the operaters just lacked the trust in them while suffering no shortage in manpower - I don't know for certain.

    Regards,

    Henning (HoHun)
     
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  3. Graeme

    Graeme Well-Known Member

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    Thanks Henning. Ignorantly I thought it was the process to start the engine.
     
  4. GrauGeist

    GrauGeist Well-Known Member

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    HoHun has it right, Graeme

    The earlier radials needed this process performed on them as the oil would settle in the lower cylinders and hand turning would clear the oil, preventing a hydraulic lock. Later engines were designed to eliminate this condition.

    It takes two people per prop to "push through" or more, depending on your time frame.

    They push the "push through" 9 times or three times per prop on the three bladed engines. They start on the outboard engine on the right wing, moving to the inboard engine, then the inboard on the left wing, then on to the last engine.

    When the engine has been rotated, the prop is positioned with one blade at the 12 O'clock position and an engine that is waiting to be rotated has a prop facing to the 6 O'clock position. The photo shows #1 engine in the position indicating it hasn't been rotated yet, and barely visable are the bottom of the props on the right wing showing they have been rotated already.

    A tall bomber would have to have a rope gang to turn the props since the guys aren't tall enough to physically push the blades, like on a B-17 for example.
     
  5. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Usually to remove liquid lock, one would pull a few sparkplugs on the lower cylinders. If not removed it would bend connecting rods. T-28s have a set up to remove the excess oil build up.
     
  6. wheelsup_cavu

    wheelsup_cavu Well-Known Member

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    There are several videos showing this procedure being done.
    Of course I can't find one right now when I want it.

    I never knew the reason why they were doing it.
    Another tidbit of information for my files.
    Thanks. :thumbright:


    Wheelsup
     
  7. Rkt_Sci

    Rkt_Sci New Member

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    During the period Apr 1956 to Apr 1959, I was employed by my Uncle Sam as an engine mechanic, reciprocating and worked on R-3350-89A Turbo-Compound engines installed on C-119G Flying Boxcars. In tech school, we were taught that, before attempting to start any cold radial engine, it was necessary to pull the prop through a part of its arc. If two airmen were unable to move the prop, it was assumed we had a case of liquid lock. Never saw it happen, nor did I hear of it happening during those three years. I do not know that CC's or FE's (usually the same guy in the 10th, 11th and 12th squadrons, 60th Troop Carrier Group) did this check religiously, but I always assumed they did.

    The proof would be to pull the front spark plug on number 10 cylinder (bottom, center front row) to see if oil drains out. if no oil in 10, check numbers 9 and 11 in the back row. If nothing is found, there is probably some other nasty problem.
     
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  8. GregP

    GregP Well-Known Member

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    I am unaware of any radials that aren't susceptible to oil lock, but I'll take your word for it, Joe. Certainly the aerobatic Russian M-14 radials are. I know maybe 5 people who fly them and 2 of them have bent rods in the past. Most of the M-14 issues can be solved by getting a English language M-14 book and following it. They have special shutdown procedures that mitigate the issues by removing a lot of oil back to the tank, at least accoring to Robin Scott who flew a Yak-52 for years. All the American radials we run (R-980, 1340, 1820, 1830, 2600, 2800, 3350) need to be turned over before starting after a prolonged stop. Our Nakajima Sakae-31 also tends to "mark its spot," like all the other radials. Some have devices installed to facilitate draining, but they have never really solved the oil leakdown issue and manage to offer another chance for engine malfunction. The last thing you want is for an oil drain to decide it's time to auto-drain the entire engine at 5,000 feet.

    Piston rings all have an end gap and the oil will slowly migrate into the cylinders, drop by drop, right through the rings via the ring gaps. Usually 2/3 of the cylinders that are below the oil level have one valve or the other open. The R-2600 always leaks since the clyinders with open exhaust valves feed short exhaust stacks. At least the B-25 has a nosewheel and the oil leaks are mostly confined to the lower exhaust stacks and a few drips from the cowling area. One pan will usually do it for each engine.

    The only real cure I know of is to run an oil pump and remove the oil from the engine back to the tank (dry sump it) after the engine has shut down while cutting off oil flow to the cylinders. That will result in you needed to oil-prime the engine before starting it or turning it over as far as I know.

    When I worked at an Allison shop. we oil-primed each and every Allison before first startup after overhaul. And ALL of them leaked a small bit while breaking in before everything "steated" and the TightSeal got properly set. Not much ... minor small weeps that could be removed easily with a small rag. It usually got "oil tight" mostly everywhere at about 4 - 6 hours on the test stand, right when the rings would start to seat. Most of the Merlins I see run have a few minor weeps about in the same spots. Few and far between are the really externally-dry V-12's, but there are some out there. Probably the only reason I haven't noticed it on Griffons is that almost all the Griffons I have seen had the engine case painted black ... sort of makes spotting minor oil weeps problematic. But they aren't like most radials that need a drip pan almost immediately after shutting down to avoid oil spots. Our P-47 needs several drip pans as some of the oil drips tend to run down the center of the fuselage and find any opening along the way.
     
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  9. yulzari

    yulzari Active Member

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    Just out of curiosity how does this affect inverted V12s?
     
  10. GregP

    GregP Well-Known Member

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    #10 GregP, Nov 28, 2016
    Last edited: Nov 28, 2016
    The only inverted V-12 I am on a familiar basis (sort of) with is the one in our Pilatus P-2. It is a German Argus AS-410 and is a 465 HP inverted V-12. Yes, we have a pan under it, but there is usually not much oil there. I have NO IDEA why, but it seems like a fairly oil-tight engine. From purely a speculative standpoint, I assume it has a longer piston skirt on the lower side and the normal oil level might be below that. Otherwise, it SHOULD rather leak like a radial if there is normally oil on top of the pistons. Perhaps it splashes up there but is not that level normally. I have never heard of the DB 600-series engines being notorious for oil issues.

    Just for information, the Pilatus P-2 was built using the landing gear and instrument panels from Bf 109 fighters, including the tailwheel ... but they reversed the main gear so it retracts inward! Now that's a money-saving thing to do ... recycle the usable parts from the fighters you are retiring! Who'd have thought?
     
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  11. bobbysocks

    bobbysocks Well-Known Member

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    my dad told me he once watched them turn a 17s engine over prior to start up. he said they had a rig that was 2 leather cups attached to a long rope. they would put the inner cup over the blade that was vertical and the other on the next blade that would follow...then a couple guys would pull it. they did that 3 or 4 times for each engine.
     
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  12. GregP

    GregP Well-Known Member

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    Wonder what would have happened if the engine had started due to an unexpected live mag and the rope and cup pulled really hard on the prop turners ... not fun to think about ...

    I also know it had to be done since no other method was available at the time. Still, I suppose you were expendable in wartime, and that's the bottom line ... get it done and move on to the next task.
     
  13. Milosh

    Milosh Well-Known Member

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    Wouldn't fuel be required for the engine to start Greg? I doubt the engine could be started as it is not likely it could be pulled over fast enough.
     
  14. Shortround6

    Shortround6 Well-Known Member

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    Depends on how good the carb was. AS in leaking fuel into/through the intake system and into the lower cylinders. Perhaps the injection carbs were immune, I don't know. I do know that my old BMW motorcycle would occasionally hydraulic lock if parked on the side stand. Can't remember if it had to be up hill or down hill at the same time but carb on low side would overflow into the cylinder.

    However chances of more than one cylinder having an ignitable mixture would be pretty slim and without priming/proper start position chances of more than one cylinder firing would be pretty slim.
     
  15. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    "It should also be noted that the engine should be run for 60 seconds at 1200 rpm prior to stopping.
    In a radial engine the lower cylinders are vulnerable to the flow of oil into the cylinder head when
    the engine is stopped.This may cause liquid lock on a subsequent start. Liquid lock will place

    severe loads on the engine and connecting rods have been bent when an attempt has been made
    to start a liquid locked engine. Under normal operation the scavenge oil pumps can easily return all
    oil accumulating in the engine sumps. However, at lower rpm the scavenge pumps are relatively
    inefficient and may not be able to scavenge all the oil unless a sufficient time period is allowed for
    this purpose."

    http://www.antsairplanes.com/downloads/T28B&CPilotsHandbook.pdf
     
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  16. bobbysocks

    bobbysocks Well-Known Member

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    #16 bobbysocks, Nov 29, 2016 at 2:04 PM
    Last edited: Nov 29, 2016 at 2:28 PM
    unless you turn off a fuel valve and run the engine to starvation ( which you would do if you pulled lean on the mixture control ), there is always a chance that fuel vapor can be in a cylinder. I imagine that would be the shut down procedure rather than just turning off the mags. but if was just shut down with the mags then low pressure caused when the piston descends in the cylinder will draw fuel from a carbureted system. the ignition is shut off so the fuel will not detonate....unless you have some carbon build up that is glowing..then the engine will (diesel ) and sputter. once shut down if either of the intake or exhaust valves are open then the vapor can bleed off and dissipate. if the engine comes to rest after the down stroke but with both valves closed its "live"....( why you always take the sparkplug wire off of your lawnmower before fiddling with the blade ).

    an unexpected live mag or defective mag that stayed live would really make for a BAD, bad day. hand propping a small 4 cylinder cub is bad enough...something that big...
     
  17. GregP

    GregP Well-Known Member

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    Anytime you move prop on an aircraft, the mag can fire. So, pull at your own risk. That means stay out of the prop arc when pulling and it matters not whether it fires or not. I have known 3 people who did not follow this advice and are dead ... from prop strikes. It isn't often, thankfully, but it happens. If I pull one, I am applying a decent amount of outward (away from the prop arc) force. If it fires, my hand(s) will naturally move away from the prop arc and will likely fall down. Better than dead. Don't wear a tie, it might kill you when it gets pulled into the prop.

    If you don't follow this procedure, you may live a long, happy life or a short, traumatic one. The difference is whether or not the cylinder has an ignitable mixture in it. Your call. I assume it does.

    When a spark plug is removed from each and every cylinder, it can't fire and start but it CAN fire and still hurt you. It won't have much compression, but the prop can move a bit. If you happen to be in the way, you are still toast. Assume it will fire every time you move the prop and you will not get killed accidentally.

    What happens if the mag switch ground wire is broken or disconnected? It starts easily by hand.
     
  18. GregP

    GregP Well-Known Member

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    Back in post #10, I said I was sort of familiar with the Argus 410. I was having some real issues with Photobucket at the time, but they are resolved. Here is our airworthy Argus AS-410 from the side on our Pilatus P-2.

    [​IMG]

    Here it is from the front.

    [​IMG]

    The front half of the spinner has small vanes on it and serves as as airspeed indicator to keep the prop in the correct pitch / rpm range. You can still buy them in the Czech Republic and they make the constant-speed prop a non-issue for the pilot as there is no control for it. The airspeed controls the pitch automatically and YOU set the mainifold pressure.
     
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