Jump to content

engine startup modeling


pepto

Recommended Posts

(this has probably been talked about before but i don't feel like digging through pages and pages of old forum posts :P) ok so most people who have done some light digging on P-51 operations will probably know that the correct way to start the engine is to leave the mags off while starting it, count 5-6 blade rotations and then switch on the mags so it can catch (something about getting the oil or fuel flowing i can't remember) but i know it's a pretty important thing to do. the problem is in DCS you can't count 5-6 blade rotations because the engine catches WITHOUT the mags on which is kind of disheartening if you want your operations to be as authentic as possible :( what does everyone else think of this? i have a general idea of how engines from that time worked but i could very well be wrong so keep that in mind

Link to comment
Share on other sites

Yes the engine can "catch" before 6th blade, how ever: if the outside temp. is realy cold you are never able to fire that merlin up like in 15°c or higher on the 6th blade. If you have near perfect condition's (outside temp.) you are never going to have issues to fire it up.

 

The Merlin is carbureted (like u mentioned) and its normal that it does not allways fire up on the exact same stroke everytime.

 

And the perfect example for a perfect condition startup is in this video

 

 

Some Airplane engines did have a magneto that would throw a spark as long as the starter was pulled. Idk if it is the case on the P51d.


Edited by LURKINGBADGER

[sIGPIC][/sIGPIC]

Link to comment
Share on other sites

ok so most people who have done some light digging on P-51 operations will probably know that the correct way to start the engine is to leave the mags off while starting it, ...
Let's start from the very beginning. Yes, that's a subject that has being talked at length here in the forums, so if you read those previous threads you would know there's no correct way to start whether P-51 or any aircraft engine, there's always a couple or three ways in which engine starts and all of them are correct, only depends on what's the pilot or owner's liking usually. P-51 manuals has changed a lot of times while model was operative, all manuals has changes (and almost all also has mistakes) and start up procedure also varies from one to another, when it happens it doesn't mean you cannot use the "old procedure" any more, or engine won't start up if you don't follow current manual procedure. So after discussing that last thread something is clear, you can start up DCS model with a variety of procedures and all of them are true to life. That said, there's no need to leave magnetos off to start the Merlin, many pilots like to do that way but there's no need nor it's the only procedure, you can check on a variety of youtube RL videos. Also prop blades could be previously hand wind by ground crew, so you don't need to wait those six blades to start up. DCS engine model appears with the engine ready to start, like already hand winded propeller, so you can use all the real World variety of start up procedures and all of them work provided you follow them correctly. Anyway,

 

 

the problem is in DCS you can't count 5-6 blade rotations because the engine catches WITHOUT the mags on which is kind of disheartening
Check your procedure, last time I checked engine doesn't start up with magnetos off, it is impossible for the engine to start up with magnetos off, and so forth you can burn starter turning bladed a hundred times if you want before engine catches up fire, so something is going on there. Check again.

 

 

S!

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

Link to comment
Share on other sites

 

Check your procedure, last time I checked engine doesn't start up with magnetos off, it is impossible for the engine to start up with magnetos off, and so forth you can burn starter turning bladed a hundred times if you want before engine catches up fire, so something is going on there. Check again.

 

 

S!

 

I think he means the puzzling aspect of the DCS Mustang engine operation, which has been here since the release of the module, and which is - engine actually catching without magnetos indeed, every single time after two blades, even in winter map conditions. True, it will obviously not continue to run with mags off, but one cannot wonder where the hell the initial catch animation and sound comes from if there's no spark in the plugs. Seems to be some scripted effect.

i7 9700K @ stock speed, single GTX1070, 32 gigs of RAM, TH Warthog, MFG Crosswind, Win10.

Link to comment
Share on other sites

You need to do your research, guys. While the slow engine model in DCS is far from perfect, the P-51 does have a booster coil wired to the starter switch that will provide ignition even when the mags are off. If you want to give it 6 blades, don't prime prior to engaging the starter.

Good, fast, cheap. Choose any two.

Come let's eat grandpa!

Use punctuation, save lives!

Link to comment
Share on other sites

I personally don't assume anything. Nothing has ever stated, that the virtual "ground crew" has done anything beyond setting up the aircraft to the specifications the mission creator set (fuel and armaments levels, etc.).

 

I always start turning the engine with magnetos off (and without having pre-primed the intake manifold), and even in the best of weather, I never get cylinders firing before I start to prime and switch magnetos to "Both" at the same time, namely after 6 blades.

 

Sent from my GT-I9505 using Tapatalk

When you hit the wrong button on take-off

hwl7xqL.gif

System Specs.

Spoiler
System board: MSI X670E ACE Memory: 64GB DDR5-6000 G.Skill Ripjaw System disk: Crucial P5 M.2 2TB
CPU: AMD Ryzen 7 7800X3D PSU: Corsair HX1200 PSU Monitor: ASUS MG279Q, 27"
CPU cooling: Noctua NH-D15S Graphics card: MSI RTX 3090Ti SuprimX VR: Oculus Rift CV1
 
Link to comment
Share on other sites

You need to do your research, guys. While the slow engine model in DCS is far from perfect, the P-51 does have a booster coil wired to the starter switch that will provide ignition even when the mags are off. If you want to give it 6 blades, don't prime prior to engaging the starter.

 

 

Not arguing , just curious, what would keep the engine from "popping" while the ground crew were walking the prop through?

Link to comment
Share on other sites

Not arguing , just curious, what would keep the engine from "popping" while the ground crew were walking the prop through?

 

AFAIK walking the prop is only common on radial engines, because the oil tends to pool in the lower cylinders. If one were to engage the starter while there is still oil in a cylinder, it would result in a bent cylinder rod.

 

Since inline engines do not have this problem, it shouldn't be necessary to walk the prop.

Good, fast, cheap. Choose any two.

Come let's eat grandpa!

Use punctuation, save lives!

Link to comment
Share on other sites

AFAIK walking the prop is only common on radial engines, because the oil tends to pool in the lower cylinders. If one were to engage the starter while there is still oil in a cylinder, it would result in a bent cylinder rod.

 

Since inline engines do not have this problem, it shouldn't be necessary to walk the prop.

 

Have you every read any manual for real Mustang?

I think no, because you are not right.

 

just an example from one:

 

Pilot`s Flight Operating Instruction Army Model P-51D-5..... (AN 01-60JE-1)

 

SECTION II

5. Staring Engine

(3) Have ground personnel turn propeller several revolutions by hand.

 

It is exactly written in all P-51 manuals, not only in this one from 1944, or it is in similar form.

F-15E | F-14A/B

P-51D | P-47D | Mosquito FB Mk VI |Spitfire | Fw 190D | Fw 190A | Bf 109K |  WWII Assets Pack

Normandy 2 | The Channel | Sinai | Syria | PG | NTTR | South Atlantic 

F/A-18 | F-86 | F-16C | A-10C | FC-3 | CA | SC |

Link to comment
Share on other sites

  • ED Team

Never saw this action for in-line engines...

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

Link to comment
Share on other sites

Never saw this action for in-line engines...

 

Me neither, i'm curious as to what that should achieve...

 

Have you every read any manual for real Mustang?

 

Have you ever seen it done for ANY inline engine?


Edited by sobek

Good, fast, cheap. Choose any two.

Come let's eat grandpa!

Use punctuation, save lives!

Link to comment
Share on other sites

Of course not, neither i have not seen any complete pre-flight check WWII planes.

I have no idea why it is written in P-51 manuals and what they wanted to achieve, or British in Merlin maintenance manual but there is it for lower temperature (no too low, it is another procedure).

 

In one flight manual from 1944 is written "...to clear combustion chambers."

F-15E | F-14A/B

P-51D | P-47D | Mosquito FB Mk VI |Spitfire | Fw 190D | Fw 190A | Bf 109K |  WWII Assets Pack

Normandy 2 | The Channel | Sinai | Syria | PG | NTTR | South Atlantic 

F/A-18 | F-86 | F-16C | A-10C | FC-3 | CA | SC |

Link to comment
Share on other sites

Of course not

 

So not *that* wrong after all, eh? ;)

 

neither i have not seen any complete pre-flight check WWII planes.

 

Knock yourself out.

 

Good, fast, cheap. Choose any two.

Come let's eat grandpa!

Use punctuation, save lives!

Link to comment
Share on other sites

I know this video i have seen it many times, it is great. :thumbup:

 

btw. approx. 5:46 he speaks about pre-oil engine? and then do it by el. pump. And he describes why he does it, around 6th minute. May be, it is now used instead of mechanics rotating propeller :).

Can be it that reason?

 

When i flew in real P-51D, pilot did it for 2 minutes too, like Kermie does and nothing like this is written in any manual which i have read but i read only free accessible on the Internet.

Moreover, war Mustangs do not have any controls for it, neither DCS P-51D. ;)

 

and last one, i meant whole pre-flight check, including works on plane before pilot come

F-15E | F-14A/B

P-51D | P-47D | Mosquito FB Mk VI |Spitfire | Fw 190D | Fw 190A | Bf 109K |  WWII Assets Pack

Normandy 2 | The Channel | Sinai | Syria | PG | NTTR | South Atlantic 

F/A-18 | F-86 | F-16C | A-10C | FC-3 | CA | SC |

Link to comment
Share on other sites

Let me phrase it differently, in case of an inline engine, what can mechanics do that the starter can't? You can't bend a rod in an inline engine in this way because there's simply no pooling of oil to the degree it happens on radials.

 

Maybe during the war they wanted to go easy on their batteries or who knows for what arcane reason they put that in the manuals. I've never seen it done for an inline engine ever, though.

Good, fast, cheap. Choose any two.

Come let's eat grandpa!

Use punctuation, save lives!

Link to comment
Share on other sites

?

He explains why he does it.

It's the opposite of what the hand cranking of the rotaries is intended to achieve.

He's not clearing oil to avoid a catastrophic failure, he's adding oil to prevent wear at start-up.

If the engine's been sitting for a while all the oil will drain down, and there's nothing sitting in the oil-ways so starting the engine from this state would meant that if it caught straight away, the first few revolutions would be running with no oil pressure at the con-rod, cylinder & cam-shaft.

If the engine were started like that the pressures generated by the running engines would be carried by the un-lubricated (presumably soft white metal) bearings, and the cam followers would be running metal to metal.

If he cranks the engine without firing it (or in this case starts the electric oil pump) he turns the oil pump & fills the oil-ways and gets the inside of the cylinder oiled so everything is lubricated before the engine faces combustion pressures.

Cheers.

Link to comment
Share on other sites

?

He explains why he does it.

It's the opposite of what the hand cranking of the rotaries is intended to achieve.

He's not clearing oil to avoid a catastrophic failure, he's adding oil to prevent wear at start-up.

If the engine's been sitting for a while all the oil will drain down, and there's nothing sitting in the oil-ways so starting the engine from this state would meant that if it caught straight away, the first few revolutions would be running with no oil pressure at the con-rod, cylinder & cam-shaft.

If the engine were started like that the pressures generated by the running engines would be carried by the un-lubricated (presumably soft white metal) bearings, and the cam followers would be running metal to metal.

If he cranks the engine without firing it (or in this case starts the electric oil pump) he turns the oil pump & fills the oil-ways and gets the inside of the cylinder oiled so everything is lubricated before the engine faces combustion pressures.

 

This is exactly my understanding of the reason for turning the propeller 6 blades before engaging the magnetos.

 

I've always wondered about the pre-oiling Kermie does for 2 minutes in his video. The P-51 he is in is a "C" and the instrument panel is very different than the "D", so there is no way to tell from that video alone, whether the pre-oil system is a post-war addition or something characteristic to the "C".

When you hit the wrong button on take-off

hwl7xqL.gif

System Specs.

Spoiler
System board: MSI X670E ACE Memory: 64GB DDR5-6000 G.Skill Ripjaw System disk: Crucial P5 M.2 2TB
CPU: AMD Ryzen 7 7800X3D PSU: Corsair HX1200 PSU Monitor: ASUS MG279Q, 27"
CPU cooling: Noctua NH-D15S Graphics card: MSI RTX 3090Ti SuprimX VR: Oculus Rift CV1
 
Link to comment
Share on other sites

?

 

I'm NOT talking about pre-oiling... :music_whistling:

 

This is exactly my understanding of the reason for turning the propeller 6 blades before engaging the magnetos.

 

Yes, but in an inline engine, it's perfectly safe to do this with the starter. It's only unsafe in radials.

Good, fast, cheap. Choose any two.

Come let's eat grandpa!

Use punctuation, save lives!

Link to comment
Share on other sites

8<

 

Yes, but in an inline engine, it's perfectly safe to do this with the starter. It's only unsafe in radials.

 

I agree.

 

I wonder if the German inverted "V" engines had any issues with oil leaking into the cylinders.

When you hit the wrong button on take-off

hwl7xqL.gif

System Specs.

Spoiler
System board: MSI X670E ACE Memory: 64GB DDR5-6000 G.Skill Ripjaw System disk: Crucial P5 M.2 2TB
CPU: AMD Ryzen 7 7800X3D PSU: Corsair HX1200 PSU Monitor: ASUS MG279Q, 27"
CPU cooling: Noctua NH-D15S Graphics card: MSI RTX 3090Ti SuprimX VR: Oculus Rift CV1
 
Link to comment
Share on other sites

Never saw this action for in-line engines...

 

I have done it in the Rotax 912 (boxer engine). The reason is that the oil gets stuck in the circuit, therefore it is impossible to check the actual quantity. Rotating the prop, the oil eventually falls down into the reservoir. Obviously this is a different reason than in the Merlin.

 

Anyway, starting the engine is very demanding on the battery and the starter, nobody would just crank the engine with the starter motor.

[sIGPIC][/sIGPIC]

Link to comment
Share on other sites

  • 7 months later...
You need to do your research, guys. While the slow engine model in DCS is far from perfect, the P-51 does have a booster coil wired to the starter switch that will provide ignition even when the mags are off. If you want to give it 6 blades, don't prime prior to engaging the starter.

 

"Ignition: Ignition is by two high-tension rotating magnet magnetos mounted on each side of the wheelcase. The "A" bank magneto serves the intake spark plugs and the "B" side magneto serves the exhaust spark plugs. The magneto has an integral coil and breaker points operating off a four pole cam, each magneto is driven by a serrated coupling shaft turning at 1.5x engine speed. A distributor turning at 1/3 the magneto speed provides one complete cycle of 12 sparks every 2 revolutions of the engine. Provisions exist for an engine control mechanism to move the breaker base through 25 degrees of advance. In addition, the distributor features a two contacts on its rotor -- the leading finger is energized by the magneto and the trailing finger by an external terminal which can be connected to a booster coil to facilitate starting. The booster coils are essentially high tension coils with vibrating points which provide continuous spark -- when applied to the retarded finger they provide a high energy retarded spark which can greatly facilitate starting, especially with cold, slow turning (thick oil) engines which don't provide much speed for the magnetos. Merlins in aircraft only boosted the "A" bank, but I've seen boats with no boost, with booster coils on both banks, and both combinations in between."

 

"Starting: Electric starter motor composed of 24V series wound electric starting motor engaging reduction gear at bottom of wheelcase (motor mounted vertically). The geartrain provides a reduction more than 104:1, and includes a safety clutch and a modified Bendix-type mechanism to protect the drivetrain and related components from excessive torque and to allow the starter to disengage while the engine is running. Booster coils are employed to retard spark and increase ignition during low-speed cranking. Primer system for direct injection of fuel through atomizing nozzles into intake manifolds provided."

 

In Short, the Booster coil retards the spark and increases ignition for starting. The booster coil is on "A" Bank or the intake side, and Both A and B are powered by the mags, if the mags are OFF there is no spark, thus as an A&MP put it so greatly, No Sparky Sparky, No Bang Bang.

 

http://thunderboats.ning.com/page/rolls-royce-merlin-v1650-engine Source.


Edited by Enzo
Link to comment
Share on other sites

I don't read it that way Enzo. The A and B banks refer to the spark plugs, of which there are 2 serving each cylinder, and are served by separate Mags. The Booster coil is a separate system, energised by the starter circuit, and in aero engine Merlins, supply a continuous spark to only the A bank of spark plugs. No sparky sparky - bang bang until the starter circuit is disconnected.

 

It is also not a good idea to quote boat engine operations for aero engine applications as there may well be a very different set of procedures and configurations.

 

Pre-oiling makes sense, but so does the tendency to fire regardless of the mag position. It might also explain why there is a need to pull through a Merlin before starting it. And the pre-oiling system fitted to post war models.

 

I am guessing the implication in DCS is that all pre-pre-start operations have been carried out by the ground crews. There is nothing stopping either pre-oiling or no pre-oiling to be carried out in the sim it would seem. Each to his own, with no clear indication as to which is right or wrong.

Link to comment
Share on other sites

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...