Starting engines

[rcomella 1]

2 hours ago, Wothan said:

 

Here is a small edit that also works every time and should be closer to how it should be done in order to follow the POH:

1. Battery/Gnd power - On

2. Inverters and Instrument power - On

3. Master Prop RPM- Full forward

4. Fuel Tank and crossfeed levers - Full forward

5. Fuel boost pumps for all four main tanks - Low

6. Cowl flaps - 3 Fully open

7. Mixture - 3 Cut off

8. Throttle - 3 Forward slightly

9. Engine selector to - 3

10. Starter & safety - On,

11. Primer - On after 3 Blades

12. Ignition - 3 to Both after 6 Blades

13. Boost -  On (normally straight after ignition to both)

14. When it catches (12 Blades) - Mixture 3 Auto rich

15. Throttle - 3 Adjust to 1000 RPM

 

Repeat for Engine 4, 2 & 1

After engine 2 is startet set to to Plane Battery (going from ground to battery power)

Moving the Mixture lever from Cut-off to Auto rich too late after the 12 Blade call and the start will fail - Repeat the sequence.

I agree with the procedure up to step 9.  I was taught to start the engines differently after step 9( I was a mechanic on a fleet of DC6 A&Bs in the 70's) 

  10.  Mech in right seat clears #3 for start.

  11.  Mech in left seat engages safety, primer, starter, and booster coil switches.

  12.  Mech in right seat calls out blades.

  13.  Mech in left seat switches mags to Both after 12 blades.

  14.  Mech in left seat releases start and booster coil switches after engine starts, but keeps primer engaged . 

  15  After engine is running  fairly stable between 800 and 1000 RPM on primer only,  mech in right seat sets mixture to autorich.

  16.  Mech in left seat watches for a 200 RPM drop(rich mixture) then releases the primer ( This is to prevent a back fire from a lean mixture if primer is released too soon.)

I used this procedure successfully many times.  I have tried using it to start the PMDG DC6.  Not much luck so far.  Keep in mind, I am presenting a procedure from a mechanic's point of view.  I absolutely loved my time with these wonderful planes.

[Wothan 173]

The problem here is that the Primer switch is timed and that You need to move the mixture lever as soon as You hear the engine catches (right when "12 Blades" is called". Waiting much longer, moving the mixture lever, and the engine will not start. Running on primer seems not to be simulated.

[downscc 1,327]

14 minutes ago, Wothan said:

The problem here is that the Primer switch is timed and that You need to move the mixture lever as soon as You hear the engine catches (right when "12 Blades" is called". Waiting much longer, moving the mixture lever, and the engine will not start. Running on primer seems not to be simulated.

Even in a twin Cessna the mixtures are lean cutoff until the engine fires when you push to full rich.  Same here.  Running on primer? Is that a real thing?  Too much primer is more likely to lead to a flooded engine, and that is a mess to deal with, usually means you're not going anywhere for 30 min.

[MatzeH84 81]

Too much, indeed, will flood it.

What he means is, you are supposed to start on primer only, and the engine should then intially run on the fuel primed (which it doesn't). Usually you will give shots of it, and not just leave it on of course. When the engine fires, you should have enough time available to get in some mixture. Right now, if you don't immediately add mixture when the engine catches at (always exactly) 12 blades, it will starve again. But it should remain running on the fuel primed.

It is also stated in the manual that the mixture must be in the idle cutoff position, as any other position in combination with the fuel pump will flood the engine real quick (or even lock it, if you leave it on without turning).

The AFE interestingly doesn't care about the manual and provides auto rich for start plus the fuel pump. But there seems to be no penalty either, so the whole thing is rather theoretically..

[Wothan 173]

12 minutes ago, downscc said:

Even in a twin Cessna the mixtures are lean cutoff until the engine fires when you push to full rich.  Same here.  Running on primer? Is that a real thing?  Too much primer is more likely to lead to a flooded engine, and that is a mess to deal with, usually means you're not going anywhere for 30 min.

In real life the engines could run on primer for a short period, but offcourse it hard to keep the mixture right for very long and the amaount of fuel would only be enough for idling.

The reason not to move the mixture lever out of cut-off before the engine catches (on the fuel from the primer), is to prevent backfiring (can cause damage to the induction system and start an engine fire), which can happen if the mixture is too lean. Thats why You rather want to prime for a rich mixture and as fast as possible bring the mixture lever into auto rich. You also need a richer mixture for starting, just like using the choker in older cars.

You cannot compare ar radial engine with the engines of a Cessna, cause on a big radial engine, the mixture in each cylinder can be very different, since some are "hanging and others are on top.

Thats also why You turn the engine over a couple of revolution, in order to more slowly drain out oil from the lower cylinders, cause if this oil isn´t brought out of the cylinders, You risc a liquid lock, which can damage the engine.

The inconsistent mixture between the cylinders is also why starting a radial engine is more dramatic - the individual cylindres does not start working together as fast than in in-line engine, where mixture distribution for each cynders is much more consistent. Thats also why alot of caughing and spruttering happens when a radial engine is started.

[downscc 1,327]

Yup, I agree with everything you say.  I wasn't aware that you would motor on primer tho-- that part is interesting.  I don't think I'd like that at all if it happened.

By the way, the backfire issue is the same in the TSIO-520...and I follow you on the radial verses flat explaination up to that causing a difference in mixtures.  Not sure how the intake stroke vacuum created in the manifold is going to vary from cylinder to cylinder because it is orientated the way it is... more just a matter of minor  differences in  flow restriction between each intake.  Seems to me that the plenum on the discharge of the supercharger would distribute fuel/air rather evenly.  Interesting topic.

[Wothan 173]

downscc...

When You prime a radial engine, I guess that the mixture might be richer for the lower cylinders.

Radials have a poorer induction system than horizontal opposed or in-line engines.

You have two rows of cylinders fed from the same carburator, so the distance from the carburator and to the individual cylinder can be quite different, whereas it's much esier to put the carburator more central on in-line or horizontal opposed engines. And even on an old carburator fed 4 cylinder in-line engine, the 2 outer cyslinders run more lean than the inner, thats why on higher performance cars You put individual carburators on each cylinder, but then again these must be very precisly adjusted.

[downscc 1,327]

Don't know Finn, the engineer part of me is still not going where you are leading.  Why is the mixture richer for the lower cylinders?  Fuel/air mixture is lighter than air so why does it sink?

The induction system of the radial is pretty dang impressive, plus the carb is located centrally right in front of the supercharger, regardless, all the cylinders are receiving the fuel/air mixture from a plenum on the supercharger discharge.  Okay, you don't have to convince me but I thought you had some insights that would be of interest. Thanks for trying..

[Wothan 173]

You can read alot about engines and find that the cylinders thats farther away from the carburator will run leaner.

Read f.ex here: https://arc.aiaa.org/doi/abs/10.2514/8.373?journalCode=jans

Thats for a single row radial engine, then consider how that work on a multirow radial engine.

[Alan_A 1,650]

Perhaps of interest - here a beta tester's video, just posted, showing the startup sequence.

Interestingly, the settings here include mixture auto rich and mags on both before the engine is cranked.

Unfortunately, I haven't yet managed a successful start using this or any of the other procedures listed in this thread.  That's in spite of years of simulated radial time thanks to A2A (full system modeling) and to Manfred Jahn's C-47 (scripted start sequence).  

I think I'm either missing something completely obvious, or I've got a controller issue.  Will try to run it down, but there might be a support ticket in my future.

In the meantime, I hope the video is of some help.

EDIT: Corrected to clarify that this is not an official PMDG video, per the post below.  But comes from an experienced beta tester.  Again, hope it's helpful.

[Olympic260 415]

Just to be clear. The video is not official PMDG video. I am a beta tester and not represent PMDG :)

 

i am using the same steps as AFE does on the before start i.e. Mixture and mags on before anything else

[Alan_A 1,650]

16 minutes ago, Olympic260 said:

Just to be clear. The video is not official PMDG video. I am a beta tester and not represent PMDG :)

Thanks, Chris - I edited my post to make that clear.

Have been enjoying your videos and I'm sure this one will do me some good once I figure out what's getting in the way of my startup.

[sgreen91 182]

I've found the way to start with mixture in cutoff.  Click the start switch, then booster (this will give the coil more charge), then boost pump to low, primer click and at the count of 12 ignition to both.  

Since I read about the booster it has helped me getting it started the proper way.

[Alan_A 1,650]

Well, I'm getting nowhere.  Engine cranks but won't catch.  This happens with and without realistic start.  If I set ready to taxi, engines are running fine.  So this has to be a problem in my setup - maybe a hardware issue.  I don't want to trouble PMDG with a ticket yet, not 'til I've run everything down.  Will keep working the problem.

 

[Olympic260 415]

26 minutes ago, Alan_A said:

Well, I'm getting nowhere.  Engine cranks but won't catch.  This happens with and without realistic start.  If I set ready to taxi, engines are running fine.  So this has to be a problem in my setup - maybe a hardware issue.  I don't want to trouble PMDG with a ticket yet, not 'til I've run everything down.  Will keep working the problem.

 

Alan,

 

Where the trottle levers are when you try to start the engines?