Vertical range for machine guns

[centurion]

And I would think very few if any AA rounds were fired absolutely vertically

[dman]

Ask for terminal velocity of bullet - was case number of years ago in New York City. Group of fisherman in boat offshore fired a rifle at school of

sharks (Lee Enfield rifle no less) . Bullet richochet off the surface of water and traveled for mile and half . Went through open car window and struck woman in back of head killing her. Coroner said if window had been closed would have glanced off and woman would have survived...........

[Rockdoc]

Maximum elevations from Hogg & Thurston:

French 75: 70 degrees

British 13-pdr 6-cwt Mk III on Mk 1 HA mount: 70 degrees

British AW 13-pdr Mk IV on its own mount: 85 degrees

British 13-pdr 9-cwt on Mk 3 or 4 mount: 80 degrees

British 3-in 20-cwt: 90 degrees.

Keith

[centurion]

Indeed thanks for this. What I was trying to ascertain was what was the ceiling above which machine guns would be ineffective in protecting balloons. I suspect that it's going to turn out to be around 3,000 feet or lower which means they'd be effective mainly against low level attacks only, probably when the balloon was being hauled down in response to the sighting of attackers. Given the relative cheapness of balloons to aircraft and the ease of replacement it would seem that the main reason for attacking balloons was not so much to destroy the balloon but to temporally blind the enemy. The achievement of Luke, Coppens et al was to destroy enough balloons in a particular location as to extend this period of blindness whilst new balloons were brought up from some depot in the rear and therefore to cover some major tactical movement etc. However just forcing the observers to take to their parachutes whilst the balloon was hauled down would probably buy more than an hour of unsightedness. It would seem that observers were not asked to go up again immediately after a jump (and indeed some are recorded as refusing to ever go up again) so a fresh crew would have to be brought forward before the balloon was allowed to rise to altitude again. This could well allow, say, a long range gun to me moved into a new position and concealed or a sizeable raiding party to be moved up into it's jump off position

What I'm struggling with is how the overall defence of balloons was organised. What combination of guns were used, what were the restrictions on where and when they could fire (so as to avoid the risk of hitting their own balloon and/or observers as well as any protective fighters). The is not much out there that I can find apart from some limited accounts of American and German arrangements in terms of types of gun used but not of how they were deployed and controlled. I did open a thread but it almost immediately got hi jacked with photos of Caquot and Drachen balloons which was not the question I was trying to get an answer to (and annoyingly there are already other threads to which these could have been posted)

[Rockdoc]

I can only speak about the situation on the Salonika Front but balloons were certainly seen as a very important tool because, even though there was never anything remotely like a surplus, AA sub-sections were associated with balloon positions from the first. By and large, balloons seem to have been kept in place for extended periods of the time but they were also moved about temporarily because the AA Diaries record their being sent to give cover for a few hours up to a day or so. I know nothing abut the MG side of things, I'm afraid.

Keith

[centurion]

Can't answer for Salonika but the number of balloons in use by all sides on the WF grew to such numbers that I doubt there was enough AA and fighter availability to give them all equal protection without spreading this impossibly thin and that AA cover might be moved to provide extra protection should any particular balloon line become especially important (possibly because of some local tactical reason). "We think Jerry is up to something in sector xyz, possibly preparing for a local attack, it's important that our balloons are able to maintain constant observation for the next day or so. Can we have some extra AA protection please?" sort of thing

[MikB]

The round has only to be fired a small way off vertical for it to follow a standard trajectory and continue to the ground point first. It will then arrive at a much higher residual velocity because although the effect of gravity will be exactly the same, air resistance to the pointed bullet will be far less than to a bullet falling base first.

Regards

TonyE

I'm not so sure about this. I would have expected the spin to decay below the stabilisation needed to maintain the precession which allows the point to follow the line of trajectory. SA bullets have enormously less angular momentum of rotation - and sectional density for velocity retention - than artillery shells, because of square/cube proportionality, so I wonder whether at upper-register elevations their trajectories would be anywhere near as stable.

Is there any literature describing extreme-range stability in small projectiles?

Regards,

MikB

[centurion]

Interesting discussions but a million miles away from what I was trying to ascertain which was the maximum effective ceiling for MG AA fire. A bullet that goes straight up until gravity reclaims it has reached its maximum ceiling but is way past its effective one (unless just possibly it carries an explosive charge and therefore is not reliant on transfer of kinetic energy on impact to achieve a result). From info posted here and elsewhere it would seem likely that the maximum effective ceiling was somewhere between 2,000 and 3,000 feet partly dependant on circumstances. Given that by 1918 Caquot balloons could operate at up to 5,000 feet (but didn't always do so) there was a substantial part of their performance envelope over which machine guns could offer no protection. However the Caquot designed balloon winch could get a balloon down from 5,000 feet to 2,500 feet in about four minutes. It would also appear that observers did not go higher than was absolutely necessary to be able to see what their mission required them to observe. Aircraft did not normally persist in attacking balloons that were below 1,000 feet as there was a very high risk that the machine gun(and other small arms ) fire would get them. There is an account of a British squadron carrying out a low level raid on balloons being winched down and destroying some but at the cost of one pilot killed, one wounded and every single aircraft that took part so badly damaged that it had to be written off. I would suspect that such attacks were only ordered to be pressed home where there was an overwhelming tactical need to ensure that there would be no enemy balloon cover in that area for an appreciable time (destroying a balloon meant that a new one had to be brought up and filled with gas, which took some time, and judicious attention from medium artillery could probably ensure that this had to wait until night time). Forcing the crew to bale out and the balloon winched down would in itself buy some time during which there was no cover as a replacement crew would need to be briefed and then re orientate themselves once the balloon was winched up again.

[Chasemuseum]

When using a machine gun for AA-fire, one needs to consider the type of burst fired, the cyclic rate of the weapon, the type of sights installed, the type of mounting and the attitude of the attacking aircraft.

Considering the last factor first, if the aircraft is maintaining a steady approach towards the AA gunner, this will give the best range. The next best will be from a long level flight passing across the front of the gun. Given a typical speed of a late war fighter in level flight as about 200km/hr or 56m/s, the aircraft will only be “in range” of the AA-mg for a very short period of time.

With respect the type of burst, an air cooled gun will have problems with bursts greater than 20 rounds. Water cooled guns will maintain a nominally indefinite burst however in the AA role this will be limited by belt feed jams and managing the waste belt.

Cyclic rate, say 400 to 450 rpm for Vickers/Maxim and 500/600 for Lewis (above 45° from horizontal mgs cycle a little slower). A 20 round burst is just over 2 seconds on the Lewis and about 3 on the Vickers/maxim.

Regards sights, only a proper AA ring site and a tall front bead sight will be effective for AA use as the gunner has to be able to clearly follow the track of his tracer and correct his lead onto the target. With the ordinary MG sights, the gun will only be effective against aircraft at very low level, providing a good steady target. However that style of flying cost Von Richthofen his life.

For effective AA fire the mg must have a very stable mount where the gunner can easily traverse and elevate the gun across wide arcs with ease.

So what’s the answer, what is the effective cover provided by a WW1 rifle calibre mg, configured as an AA gun with suitable sights and mounting? In my opinion, a hemisphere of about 3,000 feet (1,000m), so long as the aircraft enters and remains in this space in a straight line for about 2 to 3 seconds (say 100 to 150m). In practice reducing the effective hemisphere to about 2,500ft.

A definitive answer – No, just an opinion.

Other things to consider:

• WW1 aircraft were relatively robust, a bullet through the aircraft generally had little effect. The pilot and the engine were the vulnerable points. To cause enough damage to make a pilot abort a balloon attack, meant the AA gunner had a small target.
  
• The gunner's training and experience. Having instructed infantry using a section GPMG against ground targets, I can assure you that this is a critical factor. Without adequate training and practice the effective AA range could well be down to 1,000ft, possibly even less.
  

Regards

Ross T

[Steven Broomfield]

Broadly speaking, one might assume the safest place to be would come under the generic heading of "far, far away".

[centurion]

The Americans and French used the air cooled Hotchkiss mounted on a long legged tripod with a long central 'pole'. This allowed the gunner to fire upwards at angles of up to about 60 degrees whilst standing up. However this would leave the loader with a problem in reaching the feed slot and I suspect that he would have to stand on a box! This would give raise to problems if the gunner was swinging the gun to track an aircraft. The only film clip I've seen of this gun being used in AA mode has the gunner firing a single ammunition strip - there is no sign of a loader. As fas as I can see gunner was using standard ground sights.

The problem with a hemisphere is that it will tend to have the balloon being defended in the middle and some provision would need to be made to safeguard it from the defensive fire.

[centurion]

l

• WW1 aircraft were relatively robust, a bullet through the aircraft generally had little effect. The pilot and the engine were the vulnerable points. To cause enough damage to make a pilot abort a balloon attack, meant the AA gunner had a small target.
  

The non armoured non self sealing fuel tank was also pretty vulnerable as were the wing mounted radiators on some types (eg Albatross D III and V) and the frontal radiator on the Fokker D VII. In fact unless you hit a fuel line or a plug most engines themselves were fairly robust as far as small arms fire was concerened. Structurally there were plenty of weak points that a bullet in the wrong place could cause disaster, It's probably fair to say that the unarmoured WW1 fighter of 1918 was at least as equally vulnerable as the partially armoured fighter of say 1940

[MikeMeech]

Hi

The USAS had an establishment of 6 anti-aircraft MGs per balloon, so they would have each covered an area of sky with some overlap. The gunners were supposed to be 'well trained' in theory, so should avoid hitting their own balloon, heavier AA weapons were supposed to be deployed near by but not on establishment of the Balloon units. Other nations would be similar probably.

Aeroplanes were difficult to shoot down, S.S. 205 'Notes on Observation from Aeroplanes' gives the RE.8 as an example:

"Suppose the machine to be flying at 500 feet, over a machine gun, and five degrees to a flank. The total surface presented to the eye is approximately 461 square feet. The total surface, which if struck, will damage the machine as to render it unserviceable for flying for from 12 to 24 hours is approximately 106 1/2 square feet. The total surface which, if struck, will render the machine unserviceable for from 24 to 56 hours is approximately 20 3/4 square feet. The total surface which, if struck, will bring the machine down at once is approximately 2 1/2 square feet. These figures are exclusive of the pilot or observer, either or both of whom may be struck, and the machine show no immediate sign of injury.

From the above it follows that a machine, though easily damaged-and damage is a serious matter-is not easily brought down at once."

I hope that is of use.

Mike

[centurion]

Hi

The USAS had an establishment of 6 anti-aircraft MGs per balloon, so they would have each covered an area of sky with some overlap. The gunners were supposed to be 'well trained' in theory, so should avoid hitting their own balloon, heavier AA weapons were supposed to be deployed near by but not on establishment of the Balloon units. Other nations would be similar probably.

Aeroplanes were difficult to shoot down, S.S. 205 'Notes on Observation from Aeroplanes' gives the RE.8 as an example:

"Suppose the machine to be flying at 500 feet, over a machine gun, and five degrees to a flank. The total surface presented to the eye is approximately 461 square feet. The total surface, which if struck, will damage the machine as to render it unserviceable for flying for from 12 to 24 hours is approximately 106 1/2 square feet. The total surface which, if struck, will render the machine unserviceable for from 24 to 56 hours is approximately 20 3/4 square feet. The total surface which, if struck, will bring the machine down at once is approximately 2 1/2 square feet. These figures are exclusive of the pilot or observer, either or both of whom may be struck, and the machine show no immediate sign of injury.

From the above it follows that a machine, though easily damaged-and damage is a serious matter-is not easily brought down at once."

I hope that is of use.

Mike

I think that forgets the fuel tank

[MikeMeech]

Hi Centurion

I think the fuel tanks would be included in the 'vulnerable' areas, although of course a fuel tank is quite a small area compared with the aircraft. Many memoirs mention, fuel tanks, fuel lines being hit but aircraft did not come down immediately or catch fire immediately. The document (SS 205) was issued down to Battalion, Regiment and Battery level and one of its purposes was to 'encourage' troops on the ground to fire at low flying enemy aircraft, using examples of RFC experience. This included:

"In one squadron of the R.F.C on 31st July of this year (1917), of six machines in the contact patrol flight, not one was serviceable by the end of the day, all rendered unserviceable by small arms fire from the ground, though in no case could the German infantry have received visible satisfaction."

So they were hit but not shot down. Anyone firing from the ground would probably be quite 'lucky' to hit a fuel tank on purpose. On many aircraft there was a fuel tank under the pilot's seat so in theory you could shoot the pilot and the fuel tank with one shot, I expect that was quite rare.

Mike

[centurion]

But a lot bigger than the 2½ square feet quoted and yes hitting the fuel tank might not bring down the aircraft at once but it certainly could if it flamed and a lot of aircraft were shot down in flames. Nobody aiming from the ground was aiming at the fuel tank or the pilot or any other particular part - that's boys comic book stuff. They were tying to hit the aircraft full stop.

Surprisingly no one did a scientific study on what the likelihood of hitting any part of an aircraft was and how likely this was to bring it down until WW2 when decisions had to be made on where armour plate could be best applied. This was the genesis of operational research (OR). Professor R E Jones used to do a very entertaining and instructive talk on it - I was fortunate enough to hear him. Originally teams went round to bomber stations recording which parts of aircraft had returned from raids and where the most damage had been sustained until some one pointed out that these were the ones that had returned. What information was really needed was where the ones that didn't return had been hit (and put any spare armour plate there). sounds as if the guy who wrote SS205 made the same sort of error.

When they started doing it right some interesting things emerged - for example all the vital electrics and hydraulic systems on the early model Stirlings passed through the same point in the fuselage, fire a burst there and the aircraft went down - the point was located on the inside of the fuselage just behind where the big RAF roundel was painted! I believe retrospective analysis would show many WW1 aircraft also had the same sort of vulnerable points.

[TonyE]

...........Regards sights, only a proper AA ring site and a tall front bead sight will be effective for AA use as the gunner has to be able to clearly follow the track of his tracer and correct his lead onto the target. With the ordinary MG sights, the gun will only be effective against aircraft at very low level, providing a good steady target. However that style of flying cost Von Richthofen his life.............

We have discussed this before, but the use of tracer by ground guns did not happen until quite late in the war.

The first demand for "Ordinary" SPG Tracer did not occur until February 1918 when a request for 2 million rounds per month was made. Prior to that, all tracer had been made to "Special" standards for the RFC.and they had been demanding 2 million per month for their use. Actual production in 1917 was 29 million rounds of SPK/SPG tracer or an average of just under 2.5 million per month. Included in this were any supplies to the French and Russians Whether any of that got into the hands of ground troops is not clear.. Even if it did it is not very much compared to the average of 131 million rounds of ball ammunition per month in 1917.

data from the History of the Ministry of Munitions, Vol XI, Part VI.

Not Tracer, but this is a nice "Red Label" for RFC ball ammo.

Regards

TonyE

[TonyE]

...........Regards sights, only a proper AA ring site and a tall front bead sight will be effective for AA use as the gunner has to be able to clearly follow the track of his tracer and correct his lead onto the target. With the ordinary MG sights, the gun will only be effective against aircraft at very low level, providing a good steady target. However that style of flying cost Von Richthofen his life.............

We have discussed this before, but the use of tracer by ground guns did not happen until quite late in the war.

The first demand for "Ordinary" SPG Tracer did not occur until February 1918 when a request for 2 million rounds per month was made. Prior to that, all tracer had been made to "Special" standards for the RFC.and they had been demanding 2 million per month for their use. Actual production in 1917 was 29 million rounds of SPK/SPG tracer or an average of just under 2.5 million per month. Included in this were any supplies to the French and Russians Whether any of that got into the hands of ground troops is not clear.. Even if it did it is not very much compared to the average of 131 million rounds of ball ammunition per month in 1917.

Data from the History of the Ministry of Munitions, Vol XI, Part VI.

Not Tracer, but this is a nice "Red Label" for RFC ball ammo.

Regards

TonyE

[centurion]

And if I remember correctly it has been suggested it was primarily used for signalling purposes (ie as an alternative to flares and the like)

Balloon and air attacks on infantry were in daylight - how effective was the tracer of the day (not a pun) then?

[MikeMeech]

But a lot bigger than the 2½ square feet quoted and yes hitting the fuel tank might not bring down the aircraft at once but it certainly could if it flamed and a lot of aircraft were shot down in flames. Nobody aiming from the ground was aiming at the fuel tank or the pilot or any other particular part - that's boys comic book stuff. They were tying to hit the aircraft full stop.

Surprisingly no one did a scientific study on what the likelihood of hitting any part of an aircraft was and how likely this was to bring it down until WW2 when decisions had to be made on where armour plate could be best applied. This was the genesis of operational research (OR). Professor R E Jones used to do a very entertaining and instructive talk on it - I was fortunate enough to hear him. Originally teams went round to bomber stations recording which parts of aircraft had returned from raids and where the most damage had been sustained until some one pointed out that these were the ones that had returned. What information was really needed was where the ones that didn't return had been hit (and put any spare armour plate there). sounds as if the guy who wrote SS205 made the same sort of error.

When they started doing it right some interesting things emerged - for example all the vital electrics and hydraulic systems on the early model Stirlings passed through the same point in the fuselage, fire a burst there and the aircraft went down - the point was located on the inside of the fuselage just behind where the big RAF roundel was painted! I believe retrospective analysis would show many WW1 aircraft also had the same sort of vulnerable points.

Hi

I think they well knew where the most 'vulnerable' parts were (the parts that would bring down the aircraft) that was the engine and the pilot! Any armour, when/if fitted, would be to protect them. During 1918 squadrons were equipped with 'seat armour' for operations at low level. (no point at higher level as the weight effected the climb rate and other performance criteria). Camels, SE.5As RE.8s etc. did have plates to fit for those operations. The Bristol Fighter could be fitted with the RE.8 seat armour. German armoured support aircraft only had the armour around the crew and engine (including fuel tanks) the rest of the aircraft would still be shot up making the aircraft unservicable but at least they could get back in most cases. But it all came at the expense of performance. Self-sealing tanks were being developed (there are files on them in TNA, at least some French two-seaters were equipped with them, and USAS document, in 1918, reported that British two-seaters were due to be fitted with them at the end of 1918. Flying control wires could not be protected from gun fire, but some memoirs report that squadron riggers sometimes doubled up the wires so if one was shot apart the other would still be there to use. Again spars and ribs in the wings could not be protected but again you would be quite unlucky to have them shot apart by MG fire, Archie was another matter.

As for the 'writer' of the SS documents, these were usually more than one person who had gone through the data available (after action reports, trials, experiments etc.), write up the draft and send it out to units to comment on before publication. It is quite interesting to read this process in TNA AIR 1 documents, especially when opinions differ. The BEF was also noted for doing surveys after operations, indeed some officers complained about it. On reading these documents one finds that little gets into a SS document without first being tried out in 'battle' first, indeed they thought that "Battle was the only real test". It may not be as sophisticated as OR in WW2 but it could be classed as the beginning of that type of process.

Mike

[TonyE]

The Mark VIIG SPG ( re-titled Tracer G Mark I after 1926) was actually quite a good daylight tracer. It traced bright white to about 800 yards and remained the service tracer until 1939.

Regards

TonyE

[centurion]

Hi

I think they well knew where the most 'vulnerable' parts were (the parts that would bring down the aircraft) that was the engine and the pilot! Any armour, when/if fitted, would be to protect them. During 1918 squadrons were equipped with 'seat armour' for operations at low level. (no point at higher level as the weight effected the climb rate and other performance criteria). Camels, SE.5As RE.8s etc. did have plates to fit for those operations. The Bristol Fighter could be fitted with the RE.8 seat armour. German armoured support aircraft only had the armour around the crew and engine (including fuel tanks) the rest of the aircraft would still be shot up making the aircraft unservicable but at least they could get back in most cases. But it all came at the expense of performance. Self-sealing tanks were being developed (there are files on them in TNA, at least some French two-seaters were equipped with them, and USAS document, in 1918, reported that British two-seaters were due to be fitted with them at the end of 1918. Flying control wires could not be protected from gun fire, but some memoirs report that squadron riggers sometimes doubled up the wires so if one was shot apart the other would still be there to use. Again spars and ribs in the wings could not be protected but again you would be quite unlucky to have them shot apart by MG fire, Archie was another matter.

As for the 'writer' of the SS documents, these were usually more than one person who had gone through the data available (after action reports, trials, experiments etc.), write up the draft and send it out to units to comment on before publication. It is quite interesting to read this process in TNA AIR 1 documents, especially when opinions differ. The BEF was also noted for doing surveys after operations, indeed some officers complained about it. On reading these documents one finds that little gets into a SS document without first being tried out in 'battle' first, indeed they thought that "Battle was the only real test". It may not be as sophisticated as OR in WW2 but it could be classed as the beginning of that type of process.

Mike

I think you miss the point completely. Aircraft shot down immediately (as opposed to damaged) by AA would fall in enemy territory so that the cause could only be guessed at not known until after the war. They would have extensive knowledge of what damage tended to occur on aircraft that made it back over the lines. Engines were actually quite robust and tended to fail because of major damage from things heavier than small arms fire (proper AA guns) or fuel cut outs, electrical failures, or coolant loss all of which could be caused by small arms fire. The two big causes of loss were crew injury and FIRE. With engine loss you might still glide to safety

Quite a lot of experimentation was done with armour, originally with specially armoured BE2s. In both British and German aircraft armour was in many cases applied not only around the crews but also round the fuel systems so that, for example, in the Junkers J1 the fuel tank was included in the Nickel Steel forward section. What made the Junkers particularly proof against small arms fire though was the absence of any control wires or cables- these being especially vulnerable to ground fire, rods being used instead.

[MikeMeech]

Hi Centurion

They could of course get some idea of what could bring down aircraft from the German ones brought down over 'allied' lines, the aircraft were not totally different in construction and design.

Mike

[dman]

As for "balloon busting" - did the RFC use incendiary ammuniion on the Western Front ...?

Aircraft on Home Defense were issued incendiary Buckingham bullets which contained white phosphorus

The bullet had (IIRC) slits covered with a plug of solder - the solder would melt from passage up the barrel and the white phosphorus

would extrude out and ignite in the air.

The incendiary ammunition along with improved aircraft (SE 5) which could reach the altitudes which Zeppelins operated caused heavy losses that the

Germans gave up Zepplein raids as too expensive in material and crews.

[TonyE]

Yes, the Buckingham was widely used on the western front. Although at first there was concern about how the Germans would react and aircraft carried a special card which stated the ammunition was only for use against balloons and was not intended as anti-personnel. These concerns soon diminished when the Germans started using their version of the Buckingham. the phosphorus filled SPr bullet.

Most Zeppelins were brought down by a combination of Buckingham, Brock and Pomeroy rounds and there was still reluctance to issue the latter two types in France as they were explosive rather than incendiary and thus clearly breached the St.Petersburg/Hague conventions. Again though, by 1918 such things were forgotten and all sides were using explosive rounds for air service.

Regards

TonyE