correct as is Cannons have a 1 seconds delay before firing (actually .25 second delay on first pull)

[Bozon]

2 hours ago, No1sonuk said:

Maybe the pneumatic triggering on the Mosquito takes longer as all four are split off one manifold.
I don't have the Spitfire's system diagram to compare, but I'd have thought the control lines would be split earlier in the path as the cannon are not all in one place.
Maybe that makes it quicker to respond?

I would also like an explanation of this.

 

The trigger on the stick is electric, there are no pressure tubes going through the control column.

My guess is that the cannons are un-cocked before firing - when the trigger is pulled a pneumatic piston is used to cock the cannon, after which it fires and uses the Hispanos return gas tube and blow-back to pull the bolt for the next shot, repeatedly. Maybe after firing the cannon ends up in a un-cocked state again, so next time we pull the trigger we start from the same state? Maybe. I know other planes with other cannons either had their guns cocked on the ground, or cocked them once in the air (Like the guns on the Mig21) and then the guns will remain in a cocked position when stopped firing. Why would the mosquito be different than every other plane in this regard?

 

If my guess is correct more or less, then the delay is cased by the time it takes to pull back the bolt by pneumatic pressure to start the continuous firing sequence. The command from the trigger on the stick to the valve of the pneumatic piston is electric and takes no time. There are 2 relevant valves in the schematic below: [17] "E.P. firing valve", and [16] "Cocking valve". The cocking valve leads pressure into the [15] "Dunlop hose" - I don't really know what that means, it seems to lead to [13] the "reload mechanism", which sounds like the belt-feeding mechanism.

 

The [17] valve leads to the [14] "20-mm canon firing control mechanism". This sounds like the mechanical trigger. If so, it does not require high pressures or long piston movements to operate. The electric pneumatic valves themselves also should operate very fast - the (modern) ones I am familiar with operate at ~100Hz frequencies, i.e. time scales of ~ 0.01 seconds.

 

Anyway, during auto-fire Hispanos bolts are blown back by the remaining pressure in the barrel VERY FAST - the rate of fire is > 700 rpm, which is < 0.083 seconds per round and the bolt travel time is a fraction of that. Why would a pneumatic piston driven by (potentially) 200 psi take a second to pull back the bolt and cock the gun?

 

 

[No1sonuk]

28 minutes ago, Bozon said:

 

 

Anyway, during auto-fire Hispanos bolts are blown back by the remaining pressure in the barrel VERY FAST - the rate of fire is > 700 rpm, which is < 0.083 seconds per round and the bolt travel time is a fraction of that. Why would a pneumatic piston driven by (potentially) 200 psi take a second to pull back the bolt and cock the gun?

 

 

The only thing I can think of is that the gas reload system is higher pressure, acting on fewer parts - assuming the pneumatic cocking is external to the gun, it's an add-on abd would need to act on external cocking mechanism.
If the Spitfire-fitted guns are pre-cocked, that would explain the shorter, if any delay.
As for why the Mosquito guns may not eject and re-cock at the end of the cycle, I can only assume it would be some kind of ground safety measure.

Edited September 30, 2021 by No1sonuk

[DD_Fenrir]

I am highly skeptical of the "correct as is" announcement.

 

I also find it highly unlikely that a combat aircraft would be allowed a handicap of such nature given the crucial implications that even a split-second can have in high speed warfare.

 

This delay from button activation to actual cannon firing is not something I have EVER come across as noted in any of the literature I have read on the Mosquito; unless ED can provide some evidenced documentation I will continue to push for this as a bug.

 

Edited October 1, 2021 by DD_Fenrir

[PL_Harpoon]

To be honest, a delay in firing the guns would be a big thing in real life too. 

 

No sane engineer would design a system with 1 second delay between pressing the trigger and firing a gun and even if somehow they would, the pilots would definitely complain about it.

 

In other words, if there really was a delay it would either be mentioned in the aircraft manuals (warning pilots about it) or it would pop up at least once in pilots memoirs as its a pretty big design flaw. 

[Basco1]

31 minutes ago, DD_Fenrir said:

I am highly skeptical of the "correct as is" announcement.

 

I also find it highly unlikely that a combat aircraft would be allowed a handicap of such nature given the crucial implications that even a split-second can have in high speed warfare.

 

This delay from button activation to actual cannon firing is not something I have EVER come across as noted in any of the literature I have read on the Mosquito; unless ED can provide some evidenced documentation I will continue to push for this as bug.

 

I totally agree,as I replied in an earlier post....there is a fundamental flaw somewhere,and I too don't believe for one minute this is correct behaviour,as you quite rightly state that it is highly unlikely that a combat aircraft would be allowed a handicap of such nature given the crucial implications that even a split-second can have in high speed warfare.

 

This is so right.....these were life and death crucial moments to a pilot and I too have never ever heard of any momentary loss of time being wasted prior to these cannons firing.

 

So I too will also be regarding this as a bug until a more thorough understanding is put forward to prove otherwise.

Edited October 1, 2021 by Basco1

[No1sonuk]

The only way I can think of that would give such a delay is very long air pipes from the firing valve to the gun.

Longer pipes would have more air requiring to be compressed before the cylinder could act on the gun mechanism. 

However, the system diagram seems to indicate the pipes are far shorter than that.

[Bozon]

8 hours ago, No1sonuk said:

The only way I can think of that would give such a delay is very long air pipes from the firing valve to the gun.

Longer pipes would have more air requiring to be compressed before the cylinder could act on the gun mechanism. 

However, the system diagram seems to indicate the pipes are far shorter than that.

The diagram is symbolic so the length of a line in the drawing does not indicate anything about its actual length. However, reasonable design of an electro-pneumatic actuator is to place the electric valve as close as possible to the actuator’s piston. 
 

The way electro-pneumatic systems are usually designed is that there is a main valve that compresses the lines to the actuators, and each actuator has a two-way electric valve built into it - the valve directs the pressure to one side of the piston and vents the other side (or switches upon electric command) to move it. Therefore, the lines all the way to the actuator are kept compressed and only the volume of the piston is filled/vented in every actuation.
 

The amount of work that needs to be done per actuation determines the piston volume (pressure times volume is energy). This includes extra kinetic energy so that the cannon mechanism will really fly and slam backwards quickly - this is how you design the desired actuation time. The pressure line must be able to supply air fast enough so the time to compress the piston volume is shorter than the desired actuation time - this is usually easy to achieve with thick enough lines going into the actuator and buffer volumes if needed). So I can’t see why it would be so poorly designed to include a very long response time.

 

[No1sonuk]

If it helps, I've thought of how the gun may not recock at the end of the triggered burst, and that subsequently making the initial shot take longer:
If the gas tube is opened, there won't be enough pressure in it to unlock the bolt when the bullet passes the port in the barrel.
If sufficient compressed air was then fed into that tube, it could operate the mechanism, bit it might be slower than during firing because the pressure is lower and the air leaks out of the port into the barrel.  The bolt would also need to be pulled back after unlocking as there would be no residual blowback.

Unfortunately, if that is the case, none of it would explain why a different setup would be used in the Spitfire.

[Ercoupe]

At the speeds that air combats occur, having even a one second delay before the guns fire would mean that you'd lose most of your targets. It's ridiculous to think that's correct.

[bell_rj]

17 minutes ago, Ercoupe said:

At the speeds that air combats occur, having even a one second delay before the guns fire would mean that you'd lose most of your targets. It's ridiculous to think that's correct.

I'm just reading the Battle of Britain by James Holland (which is an excellent book BTW) which mentions about halfway through that many shooting opportunities lasted for a split second and were then gone.

[Ercoupe]

It isn't even just air to air combat. Flying low, the ground passes by at a dizzying speed.  With a one second delay, the target would be far behind you by the time the guns fired. Let's not be silly. This is wrong.

[Skewgear]

Bozon's post here has reasoned out how the Mosquito FB.VI's Hispano Mk.II installation works. The delay should only apply to the first round fired and even that's very debatable and depends what specific situation ED is simulating. But for completeness...

The Mosquito FB.VI was armed with four .303" Browning Mk.II machine guns and four 20mm Hispano Mk.II cannon. We know this is what's supposed to be modelled in our game because that's what it says on the DCS store page.

The Hispano Mk.II* manual, Air Publication 1641F, tells us how the gun works. AP1641F Chapter 2 is downloadable from this WW2 aircraft forum. In the Mosquito the gun was belt-fed, which matters later on. Par 6 of AP1641F describes the Hispano's basic operation as follows:

Quote

6. To enable the first round to be loaded and fired, the breech of the gun is opened and the gun cocked by a cocking piston on the right-hand side of the gun body. The operation of this piston, either by hand or pneumatically, forces the breech block assembly rearwards against the pressure of a return spring. When the gun has been cocked, the breech block assembly, consisting of breech block, two unlocking plates, locking piece, and firing pin, is held in the rear position by a sear which protrudes into the gun body and engages the underside of the locking piece. The gun is then ready for firing.

This tells us the Hispano is cocked either by an armourer on the ground (by hand) or in flight by the pneumatic system. Par 7 goes on to say that the firing of the gun can be controlled by a Bowden cable (like a bicycle brake) or pneumatics. In the Mosquito it's a pneumatically actuated mechanism as Peachmonkey posted earlier in this thread. For convenience I'm going to call that pneumatic mech "the trigger". (The Spitfire V's Hispano Mk.II installation worked in exactly the same way as the Mossie and this YouTube video briefly covers what I'm writing below)

As par 7 of AP1641F says, the trigger works so as "to withdraw the sear and so allow the breech block assembly to travel forward, propelled by the return spring." Par 8 explains:

Quote

8. The breech block assembly, as it travels forward, pushes a round from the magazine (or belt-feed mechanism) and forces it home in the chamber. When the breech block assembly reaches its forward position the un-locking plates and locking piece can move independently of the breech block itself. The locking piece moves down in front of a locking shoulder which is fixed in the gun body, and the unlocking plates move forward over the locking piece, thus positively locking the breech. The firing pin, being tied to the unlocking plates, moves forward with them and fires the cartridge.

TL;dr when the breech mechanism is released by the trigger and flies forward, it chambers and fires a round.

So: the gun starts in the uncocked state. When we pull the trigger in the cockpit the pneumatic system cocks the gun and depresses the sear, allowing the newly-cocked breech mechanism to fly forwards and fire a round. That's the source of our delay: pressurising the pneumatics to cock and fire the gun. Should the delay be as long as 1 second? I don't know, but I'd be surprised if a 200psi system (per [14] of AP2019E Vol I Sect 9, AL25, Nov 1944, Mosquito FB.VI Servicing and Descriptive Handbook) took that long to function.

What happens after you've fired the first burst? Does the gun need to be recocked?

AP1641F again, par 10:

Quote

If the firing control mechanism [pilot's trigger] has been released, the breech block will be held to the rear position by the sear, but if it has not been released, the breech block will be propelled forward again by the return spring and the sequence of action will be repeated...

This is repeated in par 21 in the full detailed description of the gun's operation:

Quote

... If the firing control mechanism is released, the sear will engage in the bent in the locking piece and thus retain the breech block in the rear, or cocked position.

Once the gun is cocked the only source of delay on firing is the lock time for the pilot's trigger to operate the sear through the pneumatic system. This should be minimally different from the Browning guns.

 

At this stage the question for ED is: are you simulating the guns being decocked when the aircraft spawns in? If so, the delay should only apply to the first burst.

This might be the situation if you imagine the Mosquito armourers chose not to cock the guns on the ground. Cocking the Hispano looks like a dangerous operation because if you don't get the breech block fully rear so it engages the sear, you'll fire the gun.

For simplicity I'd say the cannon delay on firing should be adjusted to match the .303" Browning guns. I don't think the 20mms' current delay-on-every-burst is correct at all.

[Nealius]

Wait the Hispanos are open-bolt? For a 20mm? All this time I thought they were a standard closed-bolt gas system. 

[Bozon]

@Skewgear thanks for the info! This fills many of the knowledge gaps I had when trying to guess how DCS modeled the Mosquito Hispanos.

ED, @BIGNEWY or whoever reads the boards, please look into this again and if the conclusion is still “correct as is” then fine, but please give us a short explanation of how the Mosquito cannons work and the root cause of the firing delay. Beyond fixing or not fixing the early access, we really want to learn.Thanks.

[Magic Zach]

4 hours ago, Skewgear said:

Bozon's post here has reasoned out how the Mosquito FB.VI's Hispano Mk.II installation works. The delay should only apply to the first round fired and even that's very debatable and depends what specific situation ED is simulating. But for completeness...

The Mosquito FB.VI was armed with four .303" Browning Mk.II machine guns and four 20mm Hispano Mk.II cannon. We know this is what's supposed to be modelled in our game because that's what it says on the DCS store page.

The Hispano Mk.II* manual, Air Publication 1641F, tells us how the gun works. AP1641F Chapter 2 is downloadable from this WW2 aircraft forum. In the Mosquito the gun was belt-fed, which matters later on. Par 6 of AP1641F describes the Hispano's basic operation as follows:

This tells us the Hispano is cocked either by an armourer on the ground (by hand) or in flight by the pneumatic system. Par 7 goes on to say that the firing of the gun can be controlled by a Bowden cable (like a bicycle brake) or pneumatics. In the Mosquito it's a pneumatically actuated mechanism as Peachmonkey posted earlier in this thread. For convenience I'm going to call that pneumatic mech "the trigger". (The Spitfire V's Hispano Mk.II installation worked in exactly the same way as the Mossie and this YouTube video briefly covers what I'm writing below)

As par 7 of AP1641F says, the trigger works so as "to withdraw the sear and so allow the breech block assembly to travel forward, propelled by the return spring." Par 8 explains:

TL;dr when the breech mechanism is released by the trigger and flies forward, it chambers and fires a round.

So: the gun starts in the uncocked state. When we pull the trigger in the cockpit the pneumatic system cocks the gun and depresses the sear, allowing the newly-cocked breech mechanism to fly forwards and fire a round. That's the source of our delay: pressurising the pneumatics to cock and fire the gun. Should the delay be as long as 1 second? I don't know, but I'd be surprised if a 200psi system (per [14] of AP2019E Vol I Sect 9, AL25, Nov 1944, Mosquito FB.VI Servicing and Descriptive Handbook) took that long to function.

What happens after you've fired the first burst? Does the gun need to be recocked?

AP1641F again, par 10:

This is repeated in par 21 in the full detailed description of the gun's operation:

Once the gun is cocked the only source of delay on firing is the lock time for the pilot's trigger to operate the sear through the pneumatic system. This should be minimally different from the Browning guns.

 

At this stage the question for ED is: are you simulating the guns being decocked when the aircraft spawns in? If so, the delay should only apply to the first burst.

This might be the situation if you imagine the Mosquito armourers chose not to cock the guns on the ground. Cocking the Hispano looks like a dangerous operation because if you don't get the breech block fully rear so it engages the sear, you'll fire the gun.

For simplicity I'd say the cannon delay on firing should be adjusted to match the .303" Browning guns. I don't think the 20mms' current delay-on-every-burst is correct at all.

Thanks Skew!

[Art-J]

4 hours ago, Nealius said:

Wait the Hispanos are open-bolt? For a 20mm? All this time I thought they were a standard closed-bolt gas system. 

What a coincidence. Just finished watching Forgotten Weapons episode in which Ian describes British Mk II* .303 Browning machine gun, aircraft version. Apparently Brits converted Browning to open-bolt system because unlike US ammo, theirs used cordite propellant which caused cookoffs when firing long bursts during trials.

I believe Hispano was adopted after the Browning - wonder if it followed the same system for the same reasons?

P.S. - I recommend aforementioned episonde - here it is:

https://www.youtube.com/watch?v=jqq3Jf3Jpxo

 

[grafspee]

Also open bolt provides nice cooling effect between bursts

[Hog_driver]

23 hours ago, Nealius said:

Wait the Hispanos are open-bolt? For a 20mm? All this time I thought they were a standard closed-bolt gas system. 

IIRC, the German MK108 fired from an open bolt.

Anyway, regardless of the fact if a cannon fires from an open or closed bolt, there shouldn't be any significant (1 second) delay.

If the cannon wasn't cocked on the ground and has to be cocked in the air by a pneumatic system, I guess there can be a short delay. But (IMHO) after the first cartridge has been fired, there's not need for the pneumatic system to cock the cannon again and there shouldn't be any delay anymore.

[Basco1]

The silence from ED over this issue is 'deafening'......an explanation to why they've implemented this delay in the cannons,and it's 'correct as is',would be a start,but to date it's been very non committal on their part.....Sssshhh I can hear a pin drop,lol.

Edited October 27, 2021 by Basco1

[razo+r]

Thats pretty normal. ED doesnt often if at all talk about their warbirds in the english part. 

[Basco1]

7 minutes ago, razo+r said:

Thats pretty normal. ED doesnt often if at all talk about their warbirds in the english part. 

Yeah.....but that's the big point.....maybe they should !.....after all we are their customers,and we're only asking.....no one is demanding anything,it would be nice just clear this issue up once and for all.....do you not agree ?

[Holbeach]

Measuring the time delay, cannons only, with a video editor, the times were:

 

First shot ---- 0.25 secs.

Second shot - 0.15 secs.

Subsequent shots - 0.15 secs.

..

Edited October 27, 2021 by Holbeach

[Krupi]

It is ridiculous that they have yet to address this, all we want is an explanation. 

They can make mistakes, the Anton fuses being modelled incorrectly is a good example. 

[Hog_driver]

12 minutes ago, Holbeach said:

Measuring the time delay, cannons only, with a video editor, the times were:

 

First shot ---- 0.25 secs.

Second shot - 0.15 secs.

Subsequent shots - 0.15 secs.

..

 

In theory, it's not that bad, but it's noticeable nonetheless.

It seems not to be the case when you fire the guns in the Kurfurst, for instance.

[Krupi]

It is definitely noticeable, especially compared to any other aircraft in DCS. 

It just doesn't feel right, I can't imagine such a delay being accepted in reality.

Just think about the missions that the Mossie was used on, when staffing a AA packed airfield one wouldn't lackadaisically select an aircraft to shoot up. One pass at high speed and then you get out as fast as you can without even debating a second pass.

The kind of firing delay we currently have would be laughable in this scenario. 

Edited October 27, 2021 by Krupi