WWI Aircraft MGs - duration of fire?

[mikebrn]

Can I ask for help on the following - either answers or a pointer to where I can find the info?

I am interesting in finding out the approx duration of fire for certain weapons. For example, the Vickers on a Camel or Spandau on a Fokker Triplane, how many seconds fire did each gun have? Did they all carry roughly the same length belt of ammo?

For drum or other belt felt guns like the Lewis or parabellum, how many seconds fire did each gun have before the drum needed to be changed?

Thanks for any help.

MIKE

[Maxim08]

Duration,
The Maxim style guns - 'Spandau' 08, 08/15 and Vickers Maxim, have a cyclical rate of up to 600 rounds per minute. Note the up to clause. The actual rate of fire is controlled by the interrupter gear which is controlled by engine revs. Different ammunition loads can change the rate as well. I believe that most Fokker and Albatri carried 1one 250 round belt per gun.

Can't comment too much on free guns and non interrupter, but the cyclical would no longer be reduced by the prop / interrupter gear.

Lewis guns have two magazine types that I am aware of and I believe that the large capacity one is about 90 rounds.

The assult version of the 08/15, not the lmg 08/15, carried a 50 round drum on the right hand side.

Hope that this helps a bit. Corrections welcome to the above.

Regards,
Maxim08

[Rbailey]

The Lewis drum held 97 (originally 47) rounds, with a rate of fire 500-600 rpm.

[Romani]

The following thread will answer some of your questions, it's still open, I am still researching

http://www.theaerodrome.com/forum/showthread.php?t=25587

[Dave_Watts]

Hi,

Maxim 08 said most of it.

With the lmg 08/15 mounted on a German fighter (like a Fokker triplane), were looking at, normally;

500 rounds per gun.

440 - 450 rate of fire per gun, (from my observations of many photographs).

Maxim 08 was correct with regards to the motor speed affecting the rate of fire. I conducted a study of the firing system and demonstrated the rpm of the motor directly affects the guns rate of fire. I'll dig up the chart showing the rate of fire versus the rpm, and post it for you. I had a thread on it a long time ago, but can't recall where it is.

Here they are;

First an image of the gun with the rate of fire (spring tension) set for 442 (a common setting observed).
http://fokkerdvii.com/pics/rudder-markings/rof442.bmp

Here we have the chart;
The rate of fire running up the left side of the chart, 0 at the bottom and the maximum 660 at the top.
The rpm of the motor at the bottom running from left to right, again with 0 at the left and 1450 at the right.
http://fokkerdvii.com/pics/rudder-markings/rof660.bmp
As you will note the achieved rate of fire for both setting of 440 or 660 have the same graph form simply "stepped" forward. It has to be said this graph is made with the premise that the ammo is perfect, (which often wasn't the case).

This is for German aircraft. I imagine the French and British had similar systems resulting in motor rpm affecting rate of fire.

With regards to Allied guns, Tony Williams is one of the "on staff" Aerodrome machine gun experts who can help out with this field of discussion.

Best,
Dave W.

[Pips]

I've always wondered at the rate of fire on WWI aircraft.

In the movie 'Blue Max' Stachel claimed (falsely) an enemy. On returning to his aerodrome it was found that his guns had jammed after just firing 40 rounds. When Heidemann confronted him on this he said something like
"40 rounds! Just two three seconds burst. Is your aim that good?"

Is that figure correct? A two x 3 second burst from a twin MG setup breaksdown to:

2 x 3 sec = 40 rounds (twin MG)
1 x 3 sec = 20 rounds (twin MG)
therefore
1 x 3 sec (one MG) = 10 rounds
1 sec burst = 3.33/sec

Thats equates to just 199.80 rounds per minute per gun. Seems awfully slow. But as someone mentioned the interruptor gear would slow the rate of fire down quie a bit. And there are many accounts by pilots of the tac, tac, tac, sound of gunfire.

Then again if that figure is right then that explains the urgent desire by pilots to have a twin gun setup - as enjoyed early on by the Germans, and lamented by the French and British.

[TomVrille]

I am interesting in finding out the approx duration of fire for certain weapons. .
MIKE

If duration of fire is the primary point of interest, a factor which should not be overlooked is overheating of the guns. The probability of jamming was much higher if the gun was overheated by firing protracted bursts. I do not have any authoritative data on this point, but it appears that continuous firing of about 100 rounds at maximum rate of fire is close to the limiting duration of fire without allowing some cooling time. :huh:

[Dave_Watts]

Hi Cobby,

I apologize if my chart did nothing for you, it is confusing.

To your statement of;

"40 rounds! Just two three seconds burst. Is your aim that good?"

I found your math a little confusing. Especially when you started out;

2 x 3 sec = 40 rounds (twin MG)
1 x 3 sec = 20 rounds (twin MG)

I thought some more on this, and I see where you are thinking, "40 rounds! Two bursts, each with a duration of three seconds."

Okay, 2 bursts X 3 sec. = 6 sec. of two guns shooting resulting in 40 rounds expended.

To divide we should proceed, 1 gun for 6 seconds = 20 rounds. Carried out, we get;
1 second = 3.333 rounds. Extended we get 60 seconds X 3.333 = 199 rounds per minute. Just as you figured! Sorry to check your math, I just had to work it out for myself to get a handle on it.

Try this out:

I interpret Heidemann's statement as, "Two (guns with a) three second burst." equals 40 rounds. Therefore one gun for three seconds equals 20 rounds.

Recap;
2 guns for 3 sec.s = 40 rnds.
1 gun for 3 sec.s = 20 rnds.

1 gun for 1 sec. = 6.666

6.666 x 60 sec.s = 399.96 rnds.

Bottom line; I think that's acceptable, especially for a movie!

400 rounds per minute per gun is a little low, but in the range of what someone might deduce for the rate of fire when talking off the top of your head as was the case with Heidemann. In his head, he may have just taken 400 and divided by 60, gotten 6.6 and then multiplied by 6 (2 guns @ 3 seconds) and come up with 40.

I would have used 420 as when divided by 60 seconds that would give me a clean round number of 7 (rounds per minute) and then make that 14 (2 guns) then multiplied by the seconds required to get 40 (= about 3 seconds; = 42).

Sorry if my last two paragraphs of "calculation" was a bit over the top, but you get the point...the movie was pretty accurate for the rate of fire of a German lMG 08/15 aircraft gun.

Looks like were down to how to interpret what Heidemann's said, or what he meant?

Very best,
Dave W.

[Dave_Watts]

Hi Mike,

TomVrille has a good point to your question of "...how many seconds fire did each gun have?" since you would never try to shoot the gun all in one long burst. You could either over heat the gun, or the odds are you would incur a dud round in the entire belt load and that would stop you.

As to how many seconds of fire did one have, that is determined by not only the Rate Of Fire (ROF) setting on the machine gun, but (as I shown with the graph) from the motor rpm. Still we can give you some sort of answer.

At a minimum, at 440 ROF, and optimal motor speed, your 500 round ammo load/per gun, would result in 68 seconds of firing, (as stated, not in one burst, but over several bursts).

I hope this answers your question.

Best,
Dave W.

[SCMc]

This may be game related. Rather than counting bullets, the program could keep track of the cummulative time that the trigger has been depressed. The programmer would have to know the total duration of fire for each plane.

FiringDuration = (NumberOfRoundsPerGun)/(RoundsPerSecond)

RoundsPerSecond is the firing rate (in rounds per minute) divide by 60

Steve

[CodyPaul]

When i was in the army they made a great deal out of pounding it into our heads, when firing full auto shoot three round bursts. It didn't matter whether it was a M-16 or 50 cal. 3 round bursts.

I'm sure pilots did similar when in combat, very short bursts. Extended firing would cause overheating and jams.

[Simba]

I recommend reading Harry Woodman's 'Early Aircraft Armament: The Aeroplane and the Gun up to 1918', if you can get hold of it; the best one-volume work on the subject, IMO. Also, his 'Albatros Mini Datafiles' on the Vickers and Lewis guns.

'How long's a piece of string?' There are several factors that need to taken into account when assessing duration of machine-gun fire: cyclic rate of fire (rounds per minute the gun mechanism is capable of firing); reduction for synchronisation (the rounds not fired when the propeller's in the way); reduction for breakdowns (the rounds not fired because the gun and/or its loading mechanism has broken and/or jammed); physical ability of the firer to hold sights on target and cope with the gun's trigger mechanism.

Cyclic rates of fire are easy to ascertain, they're published in almost every manual for any particular weapon. Synchronisation reduction is trickier, being dependent on the synchronisation system used, engine speed in revolutions per minute and whether the gun was being fired through the arc of a two-bladed or four-bladed propeller (see the erudite posts, above). Reduction for breakdowns is even more difficult: Vickers guns had over 25 possible ways to jam, some half of which could be addressed by hitting particular points on the gun with the rawhide mallet thoughtfully provided for such emergencies; ammo belts could 'whip' due to g-forces; etc. Finally, oxygen-starved pilots and gunners could find find firing, aiming and reloading very difficult at times - which is why the twin-Lewis 'Huntley and Palmer' arrangement for Poor Bloody Observers was rarely if ever used on any other than low-flying Corps two-seaters.

End result for the RFC and RNAS was that the Lewis remained a favoured weapon for single-seaters as well as for two - no belt to jam, lighter, easily manoeuvred on overwing mountings and as a flexible weapon - and the Vickers was doubled-up so the pilot still had one gun to fire when t'other went U/S.

General rules for aiming and firing: get as close as possible before firing, preferably upright and with minimal deflection; and squeeze off in short bursts.

[Makhpiyaluta]

When i was in the army they made a great deal out of pounding it into our heads, when firing full auto shoot three round bursts. It didn't matter whether it was a M-16 or 50 cal. 3 round bursts.

I'm sure pilots did similar when in combat, very short bursts. Extended firing would cause overheating and jams.


More then three rounds are of no use only spilling ammo. The gun will climb and that means all rounds after the third wil mis their target and overshoot.
It was in the Vietnam war when they found most ammo was spilled, nowadays the M16 can only fire three round bursts.

Willem

[Pips]

Talking about spillage, you should try firing the Australian Owen sub-machine gun. Man, that thing will spin you around if your not careful. And hose all over the sky. :)

[mikebrn]

Thks for the info.

MIKE

[mustang]

Simba

You are quite correct in stating that the number of blades in the prop. affects the rate of fire of synchronised forward firing guns. Another factor relating to the prop. is the engine to prop gear ratio in geared engines.

I don't have any experience using the interrupter type of mechanism although I have some data on it in my library. However, I do have experience using the Constantinesco mechanism firing twin Vickers through a three bladed geared prop. Prop.to engine ratio 0.666 to1. This slowed the rate of fire considerably and made synchronisation difficult.

It was not uncommon to come back with a hole through one. and some times two, blades.

Best regards

Mustang

[Simba]

Thanks, Mustang.

I mentioned only two- and four-bladed props because three-bladers were very rare in WW1; the only pic I have of one is the experimental jobbie fitted to the prototype Martinsyde G.100, although I expect there were others.

Please indulge this curious ol' cat: what aircraft did you test/simulate with the CC gear, twin Vickers and geared three-blade prop?

(hoists sundowner)

Cheers!

[Barrett]

(Pulling my cyber soap box from beneath the keyboard.)

Ahem...

The three-round burst setting is a mechanical solution to a training problem. The gadget is unnecessarily complex in some weapons (the HK MP-5 trigger group is at least two full days in the armorer's class).

If we'd just Do The Right Thing and cancel one damned F-22 (or better yet, one damned submarine) we could afford to buy more than enough ammo and build enough ranges to teach soldiers and soldierettes how to shoot.

I thank you.

(Soap box kicked back under the keyboard.)

[mustang]

Simba
Thanks for the reply.Most props. in WW1 were wood. The main reason for two or four bladers was the difficulty of attaching single blades to the hub in a three bade prop. With a two or four blader there was a continuity of material from one blade to the one diametrically opposite. This wasn't the case in a three blader where the blade terminated at the hub.

I have only seen one three blade wooden prop. There is, or was, one mounted on the wall of the bar in a small hotel just outside Bankstown airport near Sydney. It was quite small and obviously off a low powered aircraft, what type I have no idea.

As regards the aircraft with twin Vickers and a geared engine it is very well known in this part of the world. It is known as the Wirraway and was built by the Commonwealth Aircraft Corportion, entering service with the RAAF in 1939, eventually 750 were built. This aircraft was very similar to the Harvard, both it and the Harvard were developed fom the North American NA y16 and NA y33 series of aircraft produced by North American in the late 1930s.

The Wirraway used the 650 HP Pratt & Whitney geared engine and a three bladed metal prop. Although it was of American origin it used British armament equipment, hence the CC twin Vickers.

I did my advanced training on this aircraft and later flew it at OTU (Operational Training Unit) and subsequently instructed on it.

It had several nasty characteristics, (as did the Harvard which I flew later) and killed quite a few of the unwary. It had to be treated with respect at all times close to the ground. It was the basic trainer at Fighter OTUs before converting to Spitfire, Kittyhawk, Boomerang or Mustang aircraft.

At one particular OTU there was a piece of macabre aircrew humour written above the door to the crew room in blood red letters. I can recall it clearly,

"Ashes to ashes and dust to dust;
If the Wirras don't get you the Kittyhawks must"

Regards

Mustang

[Simba]

Mustang, might I be right in thinking your handle's based on the CAC version of the immortal P-51 and not the North American one?

I spent three of my younger years (1959-61 and 1965) in Singapore - being the son of a Royal Navy Chief ERA, my family 'followed the Fleet' - and I've been interested in the history of the region ever since, particularly that of the Malayan campaign of 1941-42. I lived at Sembewang, where the RAAF and RNZAF Buffalos took off to challenge the Japanese all those years ago.

424 Sqn RAAF flew Wirraways from the field; I believe the type had been relegated to advanced training just prior to the outbreak of hostilities, being badly needed to convert pilots quickly onto fighters from the miscellaneous types they'd flown previously (such as Vickers Vildebeests!). I know a fair bit of the Wirraway's history - defender of Rabaul, etc. - and of that other type that shared so much of the NA Harvard's bits 'n' pieces, the Boomerang.

If you have any technical details of the synchronisation gear used with their three-blade props, I'd be very intyerested in seeing it. My e-mail address is simba.duxwing@blueyonder.co.uk

<hoists sundowner>

Cheers!

[mustang]

Simba

Re recent posts.

The handle is based on both. I flew both versions.

I am sorry that I don't have any original technical information on the CC gear.
However, there is some available in the UK.

That excellent magazine, "Aeroplane Monthly of September 2005 had a very good article on pages 32-33 of the CC gear. This article had an excellent technical description with clear coloured diagrams. Back issues are available from:

Sundry Sales,
Aeroplane Editorial,
King's Reach Tower,
Stamford Street,
London SE1 9LS

E-mail: Aeroplane_Monthly@IPCmedialtd
Cost: 3.95 pounds a copy. P&P UK included. Make cheques payable to IPC Media Ltd.

Incidently, the twin Vickers were removed from the Wirraway sometime early in 1945, and replaced with a Browning under each wing. just outside the prop. arc. I used this version at OTU and it increased the rate of fire considerably.

Best regards

Mustang

[Simba]

Thanks, Mustang. I'm a subscriber to 'Aeroplane'; unfortunately, all but the past three months' back-numbers are stowed in my li'l casa in Spain and I'm busy working in Bristol, UK. Next time I'm over there, I'll dig out that article.

I've got no flight-time in WW2 aircraft, but I was a 'hangar rat' in my teens and managed to chalk up over 200 hours on Chipmunks and glide Slingsby T.Mk.3s and Sedburghs to many happy landings before the RAF decided my health possibly wasn't up to serving a short-service commission and grounded me.

<S>

Simba.