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Cannons/MG firing order


Bozon

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I am not sure how the real thing was supposed to work, but here is what happens in the sim:

It seems that of each set (cannos/MGs) the guns fire one at a time on a sequence starting from the port-side pair of each 4.

First "problem" with this is that it significantly reduces lethality versus firing all 4 cannons simultaneously - in the latter case, with the tight clustered guns it means that if you hit, you'll likely hit with all 4 cannons for a devastating effect. When firing in sequence you just speard the fire more for reduced lethality.

Second problem is that if you fire in many short bursts, the port cannons/MG run empty before the starboard cannons/MGs do, and you are left with the last couple of seconds of fire shooting from only 2 guns respectively. This is more pronounced on the MGs since they have a longer total firing time.

I am just reporting an observation since I have no information whether this is correct or not. If this is correct then this combined with the cannons firing delay it makes this gun package a hell of a wasted potential.

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“Mosquitoes fly, but flies don’t Mosquito” :pilotfly:

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I don't know abou the firing sequence, but that may be right, since the Mosquito uses a pneumatic system for its cannons and guns, maybe the system resets and goes back to the first gun and does not starts over from where it stopped.

Regarding the firing sequence, firing all guns at once would defeat the purpose of volume of fire. What they thought at the time (and still do) was having a significant volume of fire over the target, so you fire a gun first, while it is ejecting the cartridge and recocking, the second is firing, the third one is priming, the fourth is ready to go and so on.

If they fired all guns at once would have a time interval without any rounds being fired down range.Also, you would have to have perfect aiming every time you fired, in order to properly use all the guns potential. It would be, fire...wait...fire...wait...

The way it is is fire..fire...fire... And all the cannons are adjusted to hit the center of the sight, no matter their position on the aircraft.

So, what I believe their logic in WWII was (and still is), is to have as many rounds per second thrown down range as possible. If the first round misses the target, the second would miss also, but the pilot is correcting, the third and fourth will be on target, and then it goes all over again.

And it is no exclusive to the Mosquito. If you fire all the ammo on the Mustang for instance, you will see that some MGs end their ammunition before the others, and when it is ending, only two or three MG of the six will be still firing. I don't know this is the case because some guns carry more ammo than the others in the wing or if it is a case of firing sequence, with ones always coming before some others, but a MG or cannon running out of ammo before others was a common thing in WWII aircraft. 

 

 

 

 

 

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This is an amazing sim! 'Nuff said!:pilotfly:

 

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@RodBorza Planes with wing mounted guns fire together left and right symmetrically to reduced swing due to recoil. I dont know about multiple barrels per wing if they fire together or in sequence. Firing in sequence at a high rate introduces crosstalk between vibrations caused by each gun, which may be an issue if they resonate - if so then that’s another reason to, as the song goes “fire all of your guns at once and explode into space”.

If I recall correctly, in the Mustang the inner gun on each wing has a longer ammo belts than the two outer guns.


Edited by Bozon
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“Mosquitoes fly, but flies don’t Mosquito” :pilotfly:

- Geoffrey de Havilland.

 

... well, he could have said it!

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@Bozon I gather you didn't play the first generation of Il-2 series, where guns firing in perfect sync were a subject of heated debates and people had exactly opposite request to you ;). The problem was - apparently the game didn't trace every round when playing online and the synchronized bullet "packs" were wide apart enough for the enemy plane to slip between them at high deflection shots. There's a limited effect of punching power of bullet "pack" when each "pack" is too far from the previous one and thus fast traversing target can be missed by both. That's why, since inter-war period, in guns designed or modified strictly for aircraft, ROF (rate of fire) has always been a primary factor, with projectile weight coming second. Granted, nowadays we've impressive guns which combine both, but I digress...

Back to the topic, please keep in mind that there was no such thing as synchronized ROF on real planes in WWII simply because of how guns worked (and still work today). Apart from minor differences in the triggering systems activating each gun (electric, pneumatic), there were always some variations coming from the guns themselves. Remember, that "catalogue" ROF is an average value and it's normal for it to be slightly higher or lower from gun to gun even out of factory. For example early versions of Hispano cannons were rated at 600 rpm, but they were going from about 580 to 620 and that was considered acceptable. Not to mention changes in ROF caused by gun wearing out or heating up (although the latter was more of a factor during long bursts). In single engine fighters as long as guns on each wing worked, the average recoil on both sides was still comparable not to cause yaw stability issues (with rare  exceptions, like first bubble-top Thunderbolts).

To sum it up, having all guns firing at constant rate in flight simulators is a "game'ism" and simplification compared to real life (although understandable given current PC limitations).

I doubt even DCS simulates all these small variations, so maybe the devs decided to at least change the constant ROF slightly from port to starboard guns to obtain similar "de-synchro" effect? Note, that's just my wild theory, one would have to take a deeper look at relevant Mosquito .lua files (IF they're not hardcoded?) to check, but I've never done it.

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With the cannons, the Air Ministry rejected the existing pneumatic system used in fighters because of a delay between the trigger being pressed and the cannon firing, caused by the length of the pipe runs from the air storage bottles in larger airframes. A new system was developed that had the sear system using an electro-pneumatic method instead to remove the delay. The design of the firing buttons changed to reflect the fact that they were now switches rather than operating a valve.
So if the cannons do fire sequentially then there must be an electrical sequencing box involved somewhere.
I have access to a comprehensive set of RAF armourers handwritten lecture notes that belonged to my friends dad, but I don't remember seeing a sequencer for cannons in there. Which doesn't mean it never existed, but my gut feeling is why would they needlessly complicate production ?

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2 hours ago, Extranajero said:

With the cannons, the Air Ministry rejected the existing pneumatic system used in fighters because of a delay between the trigger being pressed and the cannon firing, caused by the length of the pipe runs from the air storage bottles in larger airframes. A new system was developed that had the sear system using an electro-pneumatic method instead to remove the delay. The design of the firing buttons changed to reflect the fact that they were now switches rather than operating a valve.
So if the cannons do fire sequentially then there must be an electrical sequencing box involved somewhere.
I have access to a comprehensive set of RAF armourers handwritten lecture notes that belonged to my friends dad, but I don't remember seeing a sequencer for cannons in there. Which doesn't mean it never existed, but my gut feeling is why would they needlessly complicate production ?

It is about trigger delay not rate of fire, just like we have in mosquito right now, cannons are probably pneumatic so the response time is low, but rate of fire is very dependent on cannons it self.

To sync cannons you would need electric trigger which would lower rate of fire so the slower cannons could keep up with faster ones, for example 600 rof cannons would fire at 500 rof so even the slowest one would made full cycle before electric trigger would fire all again. Or you would need bunch of sensors which would detect when each cannon is ready to fire again, very complex system too many things can fail.

Any way most of the shooting was rather short burst, so all cannons should open up at the same time, if you hold trigger some desynchronization will appear but after couple rounds we can say that all cannons should fire at the same time, so no argent need to develop synchronization system which would complicate things.

I must say that cannon fire delay make me go crazy, because of this i have very hard time to hit something with cannons in mosquito, maybe some day we will get electro-pneumatic firing system w/o delay. 


Edited by grafspee
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Think of the electro-pneumatic system as a man holding a rifle. His finger on the trigger is the pneumatic part of the sear release and the nerve that makes his finger move is the electrical part. There is no reason why there should be a delay in firing, especially as the system was specifically designed to cure that problem.

The actual cyclic rate of the cannon is set by the manufacturer via the weapons design and it's primary consideration is reliability ( all sorts of issues for them to consider there ) and there might also be a secondary consideration of the rate of ammo use. I'm fairly familiar with this stuff because I have a background in working with small arms, but if anyone is really interested in the fine details of how aircraft mounted automatic weapons work and how they evolved over the years - up until the early cold war at least, then the classic Machine Gun books by George M Chinn are a brilliant read. He wrote them for the US Navy, so they are available online.

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@Extranajero looks like DCS mosquito has pneumatic trigger for cannons which has delay, and mgs are eletro-pneumatic trigger which has no delay, probably 🙂

Delay is noticeable for cannons in mosquito this is the only explanation if this is accurate.

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There should be no delay in the cannon firing system, but if ED decide that it's " correct as is " then I really don't have the time or energy to argue with them about it.

I'd have to travel 300 miles to scan the diagram from the armourers notebook as my friend won't let it out of his sight - it's not very valuable in terms of money, but it was his dad's, so it has great sentimental value. I have a specialist book which discusses the gun firing systems fitted to WW-2 RAF aircraft, but that doesn't contain a schematic, only a description.

Even if I presented them with the drawing I don't have any confidence in the problem with the Mosquito firing circuit ever being recognised or changed. Bugs are fixed at a glacial pace, even when ED admit they exist.
 

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Maybe the laws of physics are different in Russia ? - that's the only reason I can think of why there'd be a delay - but in any event, it won't be changed so there's no point discussing it.

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19 minutes ago, Extranajero said:

Maybe the laws of physics are different in Russia ? - that's the only reason I can think of why there'd be a delay - but in any event, it won't be changed so there's no point discussing it.

It was resolved over on the ED discord. Someone involved in keeping PZ474 airworthy who advised on the ED Mosquito explained how the pneumatic system as modelled is accurate. The firing solenoids at the gun end of the firing circuit have an inherent actuation delay, apparently.

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20 minutes ago, Skewgear said:

It was resolved over on the ED discord. Someone involved in keeping PZ474 airworthy who advised on the ED Mosquito explained how the pneumatic system as modelled is accurate. The firing solenoids at the gun end of the firing circuit have an inherent actuation delay, apparently.

I hope they told the BATF they were going to restore and fire the cannons 😄

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I found the AP201 for the Mossie. Looking at the diagram of the gun firing system there is nothing that could introduce a delay, unless there is something very weird going on inside the pneumatic gun firing unit. The associated electrical diagram shows four solenoids inside it, to open the valves, but that's only an electrical schematic. Presumably it's got more than 200psi on one side and nothing on the other - once the solenoids open the sears release, and they stay released until the pilot takes his thumb off the lever. Then the downstream air pressure bleeds off and firing halts. I wonder if the cannon had a tendency to run on a little after the solenoids closed ? that would be ironic....
I'd post images from the AP201, but then I'd have to host them somewhere and I honestly can't be bothered.
In fact this is just an exercise in futility, because nothing will change, I wish I hadn't bothered now 😄

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As quoted above by @razo+r ED insist that the delay is correct and they explain it as an issue with electric part rather then the pneumatic of the electro-pneumatic system (said solenoid). This thread is not about that - it is about the guns not starting to fire all at the same moment.

I don’t think there was any syncing device between the guns - what I expected was that all guns/mg will trigger at the same time. This is not what is happening in the game and the initial triggering of the cannons/mg is staggered - this requires a mechanism that introduces a varying delay for the triggering of each gun.

If correct, this means that DH intentionally introduced additional delays to the guns on top of the supposed base delay due to the solenoid. 

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“Mosquitoes fly, but flies don’t Mosquito” :pilotfly:

- Geoffrey de Havilland.

 

... well, he could have said it!

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5 hours ago, Bozon said:

I don’t think there was any syncing device between the guns - what I expected was that all guns/mg will trigger at the same time. This is not what is happening in the game and the initial triggering of the cannons/mg is staggered - this requires a mechanism that introduces a varying delay for the triggering of each gun.

If correct, this means that DH intentionally introduced additional delays to the guns on top of the supposed base delay due to the solenoid. 

From what I remember of the ED Discord discussion from months ago the Mosquito FB.VI's main air bottles are towards the tail (presumably for the ballast effect?) meaning the pipework to the guns runs for most of the fuselage length and therefore accounts for most of the delay between pilot pressing the trigger and shots being fired. There was a suggestion that the difference in pipe length between the outboard and inboard guns is the cause of the firing delay.

Somewhere out there is an RAF AP that specifically details electro pneumatic aircraft gun firing mechanisms. I can't remember its number or title but the Mosquito AMM that's available online does reference it. That's the only part of the Mosquito trigger mech that's a mystery at the moment.

I can easily imagine why you wouldn't want all guns firing in precise synchronisation but similarly, maintaining a specific firing offset is a lot of overhead in wartime.

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