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DC3 startup

Old 6th Apr 2020, 07:50
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DC3 startup

I was reading a copy of pilots notes for the DC3 some while ago and it showed that the engines were started with the mixtures in idle/cutoff. Could anyone explain why it is done this way?
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Old 6th Apr 2020, 08:31
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Originally Posted by Boslandew View Post
I was reading a copy of pilots notes for the DC3 some while ago and it showed that the engines were started with the mixtures in idle/cutoff. Could anyone explain why it is done this way?
I never flew DC3, but this link dc3throt suggests that there was a priming fuel pump which was operated in bursts of about 1 second. The mixture lever would need to be at cut off to prevent flooding. Once the engine fired, the mixture control could be moved to auto rich and topped up with more prime if necessary.
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Old 6th Apr 2020, 10:12
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As I understand it, all those old radials were started on the primer then bring up the mixture lever when it's running. Cessna 414 does that even today.
I spent a few years maintaining DC3 & DC4 and that's how we started them when we did engine runs. With 1 guy in the cockpit you moved the mixture lever out of the detent first and when the engine was running on the primer moved it up to rich with your foot. Take a look at the pedestal and you'll see that this is the only way.
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Old 6th Apr 2020, 10:31
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Yep, just as mustafagander put it - the Wright Cyclone was started on the primer, the mixture being selected to Auto Rich once it had caught. You certainly needed lots of hands; the starter energise/mesh switches were high up on the right for the PM to operate with the primer over on the left to be blipped by the PF.

So; 15 seconds to energise the starter flywheel before going to mesh (that took 2 hands!) After a minimum of 3 blades (i.e. one full rotation) the roof mounted Ignition went to Both. Hopefully the engine would fire, but may need judicious use of the Primer under it fully caught - then Mixture to Auto Rich.

The Dak was probably harder to start - especially when hot - than it was to land in a crosswind!!
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Old 6th Apr 2020, 12:40
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Many thanks, gentlemen. My only experience with piston egines was with small engines on the Chipmunk and Saunders Roe Skeeter. The Chipmunk mixture was only used in the cruise for economy. The Skeeter engine had no mixture control but it did have a primer that had to be used cautiously. It had a cartridge starter that either started the engine or it didn't. I think our record one cold and damp day on exercise was something like fifty cartridges before it finally caught.

If ever I win the lottery I think my first purchase will be a DC3 conversion.
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Old 6th Apr 2020, 13:22
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I have flown DC3. Although strictly by the book it started with the primed fuel and once stable handed over to fuel system. Bigger engines are generally started this way. But this wasn't necessary for DC3. It was routinely started by moving the mixture lever, very rarely primer was used.
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Old 6th Apr 2020, 13:35
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Most GA fuel injected engines are still started this way (at least the ones that I've flown). Prime it a bit, start with the mixture pulled back and push this forward as soon as the engine fires. Fuel flow as delivered by an injection system is set for idle air flow through the engine, or above. The mass of air being pulled through the engine at starting is not enough and would therefore cause it to be flooded. So the priming system overprimes the engine and by keeping the mixture in idle cut-off, you allow the mixture in the cylinders to weaken as the priming fuel is diluted with air. Once it reaches a proper fuel/air ratio, it will fire.
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Old 7th Apr 2020, 10:38
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I’m with vilas on this. Stroke the throttle a few times and then crank the engine. Can’t remember if we started in auto rich or auto lean. And count at least 6 blades to insure there’s no hydraulic lock. The prop is geared just a bit less than 1 to 2. Don’t know why you’d have to use your foot to move the mixture even if you were starting on the primer. Right hand up working the starter, booster and primer. Left hand gets the mag at 6 blades and drops down to the mixture.
On the R2800 we started on the primer and brought the mixture up when the engine was running.
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Old 9th Apr 2020, 19:21
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I feel so let down. I opened this thread hoping to read about some daft plan for a new airline using DC3s. That’s what ‘startup’ means, to me. Honestly, with people applauding Johnson, Trump’s approval ratings going as they are, and the abject failure of the world to address the wholly predicted catastrophe of this virus, I’m searching hard for something to laugh about, but ready to believe anything.
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Old 9th Apr 2020, 20:09
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Originally Posted by Kit Sanbumps KG View Post
I feel so let down. I opened this thread hoping to read about some daft plan for a new airline using DC3s.
Give it a few more months and it might happen!
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Old 10th Apr 2020, 20:04
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"After a minimum of 3 blades (i.e. one full rotation)"

That will result in almost two full turns of the engine, i.e. a full 4 stroke cycle on each cylinder with each cyl. starting from a different position.

Douglas DC-3 Dakota
Propeller reduction gear ratio:- 1 : 0.5625

So a turn of the engine turns the propeller a bit more than half a turn.
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Old 11th Apr 2020, 01:34
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Propeller reduction gear ratio:- 1 : 0.5625
Just to point out that the venerable aircraft was powered by both P&W R-1830 and Wright Cyclone R-1820, leaving aside the Russian and Japanese built versions. Loved listening to the start on those using an inertia starter, the whine prior to engaging the mesh seemed to portend an approaching event of some import.
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Old 16th Apr 2020, 06:47
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Where I worked it was 12 blades on the starter - prime for three blades- wait 3 blades then repeat. This was to ensure there was no hydraulic lock.

After 12 blades magnetos on and then prime as needed until the engine fired then mixture to auto lean.

Each engine was different - some started very easily others required switching between the primer and mixture controls to get them running.

If the engine was cold I wouldn't do anything with the primer - just put the mixture straight to auto lean. That worked very nicely.

The above is for the Pratt and Whitney R-1830-92.

I would start the right engine standing between the seats so I could see what was going on. Right hand for the starter left hand for everything else.

Left hand engine started sitting in the left seat - same use of hands.

I've even started one engine with a rope wrapped around the prop dome and attached to a pickup truck - works too!

I've heard it's possible to hand prop large radials - the technique has been explained to me but I've never seen it done.
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