Flying Guns – The Modern Era
Development of Aircraft Guns, Ammunition and Installations since 1945
Anthony G. Williams and Emmanuel Gustin
Hardcover, 240 pages.
ISBN 1 86126 655 3
This is the third and final volume in the “Flying Guns” series. The first volume discussed aircraft gun armament between 1933 and 1945, and the second one covered the period before 1933. The third book in the series describes evolutions since 1945, until today and even beyond today, as we wonder what the future of aircraft armament will be.
Here are corrections and additions to the book that we found later or that a number of people have offered to us. No attempt has been made to capture the technological evolution since the publication of the book.
Chapter One: Technical Developments
Page 12 The Hispano stayed in service for longer than decade after the war. The Canberra retained a capability to carry four Hispano cannon until the later 1960s. (Dave Everest)
Page 12 The B(I)8 aircraft of 3 and 16 Squadrons at RAF Laarbruch were still flying as late as 1971 – I’m not sure when they finally left; however, it was after 31 Squadron (PR7s) disbanded in March 1971. (Geoff Cox)
Page 16 News has emerged of two experimental Russian aircraft guns dating from the 1950s or 1960s, both designed by Makarov whose name is now associated with the standard Russian Army pistol.
The Makarov TKB 539 was a 30mm 4-chamber revolver cannon, with an unusual action in which the cylinder was allowed to recoil via the gas system action in order to unlock from the barrel, rotate 90 degrees and then relock. Obturation was achieved by inserting the case neck into the barrel for about 25mm. The cylinder was loaded from the front with special cartridges having a reduced-diameter head (a similar arrangement to the R-23). Fired cases were ejected from the front using gas pressure from the next shot. The gun weighed 73 kg (the feed system another 16.8 kg), was 184.5 cm long and fired at 2,000 rpm. The ammunition generated a muzzle velocity of 1,000 m/s.
The Makarov TKB 532 was a 23mm gun using an entirely different mechanism. It is unclear from the description whether the breech was unlocked by recoil or gas, but ejection of the fired case was purely due to blowback (no extractor or ejector fitted) with fresh rounds being catapulted into the breech by a short-stroke spring-loaded rammer. The breech was also unusual, consisting of two sideways-sliding elements like dual sliding doors.
Page 20 The following information on the Vektor 55C5 aircraft cannon was provided by Gert Rossouw, who kindly gave permission to post it here:
I was the chief designer on the project and was responsible for all design and project management during the final phases.
As is the case worldwide the pilots of our air force needed a higher rate of fire due to the short time on target. The basic requirement for the upgrade was thus an increase in firing tempo. For obvious reasons the Defa 553 was used as technology carrier.
The design focused on the feeding of the cartridge in three phases. (I believe the same principle used in the Defa 544.) The XDM was designed to eject the links on top of the feed cover but as this will result in changes to the aircraft, the approach was changed and the links were ejected in the same path as the Defa 553. Development went well and a firing rate of 2200 rpm was achieved on a firing range. However the high rate caused excessive component wear and reduced reliability. Changes were effected to bring the rate down to about 2000 rpm. Very good reliability and acceptable component life was achieved.
Integrating into the aircraft brought some new challenges which all were overcome in the end. During the final acceptance tests performed by out air force the cannon was subjected to an flight envelope of -3 and +7g force with excellent results. An entire week of evaluation was complete without a single stoppage and in-flight firing rate of 1900 were measured. Furthermore the new cannon gave the pilots higher accuracy and increased pipper control.
Several production cannons were manufactured and integrated into the air force but during the late nineties major changes took place in our defense force resulting in the replacement of the Cheetah aircraft with the SAAB Grippen. With the phasing out of the Cheetah the project was shelved. A very sad string of events for me personally but unfortunately that the way it goes.
Page 26 More detailed information about the reasons for the failure of the Aden 25 has emerged. The first problem was ‘light strikes’ on the primer by the firing pin, causing a failure to fire. A percussion ignition system has to work very hard in a revolver cannon as it has only a very small fraction of a second in which to work. After much effort it appears that this problem was solved, only to be replaced by a more serious one; the ammunition feed. The design of the gunpods intended to fit under the Harrier aircraft required the ammunition belt to be curved more or less on the limit of tolerance. The shape of the round and the design of the link also may have played a part in the feed problems, which proved insoluble.
Page 30 The 20×70B ammunition for the 27-mm developments of the M61 was produced by the Olin Mathieson ammunition and development department, in East Alton, USA. Until the end of the contract in 1955 they made a pilot production run of 50,000 rounds, including T142 (TP), T143 (dummy), T144 (HEI), T145 (high pressure test), and T147 (incendiary) rounds.
Muzzle velocity was 2000 ft/sec (609 m/s), projectile weight 3500 grains (250 gram) with fuze. The projectile length was 113mm. The filler in the T144 round was 66.4 g of MOX-2B and RDX. The fuze was fitted with a safety delay and a self-destruct mechanism.
There was also a longer cased variant, with the same overall length of the round, but a case length of 96 mm. The projectile was lighter at 200 gram with fuze (50 gram of filler), and muzzle velocity increased to 2700 – 2800 ft/sec (860 m/s).
Page 45 The 20×102 PGU-28/B “multipurpose” ammunition used in the US M61 aircraft guns has reportedly suffered from an unacceptable degree of premature detonations so the M50 series remains in service, with the PGU-28/B for emergency use only.
Page 60 From Tony Williams: “ Russia has produced ammo for both 23mm and 30mm aircraft guns in which the shell is stuffed full of chaff. It is detonated a short distance after firing. I have just acquired one of these 23mm rounds, deactivated but still full of chaff.
I could understand the purpose of the 23mm version for use in bomber defensive guns to decoy incoming missiles, but I couldn’t understand why a 30mm version was developed, as this calibre has only been used in fighters. However, I met a former USAF officer the other day, who explained it to me.
It seems that at one stage the USAF enjoyed the benefit of longer-ranged AAMs than the Russian fighters were equipped with. So the Russians developed the tactic of loading the first dozen or so rounds in their ammo belts with chaff. In a head-on clash, USAF fighters were expected to fire their missiles first. The plan was that the Russians would then fire their chaff rounds to set up a decoy cloud in front of them, using that to move out of the line of flight of the missiles. By the time this manoeuvre had been completed, the Russians would be within range and could fire their own missiles.
The rest of the ammo in the belts would be the usual HEI/AP mix for serious work.” (Tony Williams, on his military guns and ammunition forum.)
Page 60 Right column, line 8: “Luftwaffe’s Rüstsatze” should be “Luftwaffen Rüstsätze”. (Dirk Paulfeuerborn)
Chapter Two: Early Jets
Page 69 Transsonic wind tunnels. To clarify this a bit: Windtunnels capable of supersonic speeds did exist. Problems occured in the transsonic region, between about Mach 0.8 and 1.2. Later tunnels with slotted walls were designed to overcome this.
Page 82 The Brigand operated over Malaya, not Burma. (Wing Commander C J Jefford MBE BA, in his review for the RAF Historical Society Journal 32 (2004).)
Page 97 A Vampire could be re-armed in 12 minutes, a shorter time than required by refuelling, which took 15 minutes. (Dave Everest)
Page 105 The photo captioned as an illustration of the “GP-9” gun pod in fact illustrates the later, more streamlined installation of the GSh-23 gun, with the magazine (200 rounds) internal to the fuselage. The GP-9 was a conformal pod which contained 250 rounds external to the fuselage, and was much bulkier. (Weaver, on The Forum of the 1.Jagdmoroner Abteilung)
Page 109 During development of the MiG-27 fighter-bomber, the onboard GSh-23L gun of the MiG-23 was replaced by more a powerful one. The energy of the GSh-23L is not enough to guarantee a successful engagement of armoured vehicles and ground targets. NATO already had a new tanks with armour that the 23-mm shell can’t penetrate. The problem was sharpened by an unsettling lag in aircraft artillery development.
The Military were interested in an aircraft weapon capable of effective engagement of all types of armoured vehicles, including APCs, light tanks and modern MBTs, such as the American M1 Abrams. To achieve this, a transition to higher caliber and more powerful ammunition was necessary. The Soviet government ordered the development of a 45-mm aircraft cannon with an active-reactive, rocket-boosted high armour-piercing shell. However, development of a new cannon and ammunition required a lot of time. Therefore it was decided to install in the MiG-27 a 30-mm Gatling-type multi-barrel cannon with a high rate of fire and high per-second burst weight. The initiator of the transition to 30-mm cannon was the Vice-Minister of Defence of Army Armament, general V.Ya. Shabanov, who supported the idea of unification of ammunition, based on a standard high-power shell for Army, Navy and Air Force.
The transition from 23-mm to 30-mm shells resulted in a doubling of shell mass (175-185 g. against 400 g.) and a tripling of the weight of explosives contained in it. Better ballistics provide high armour-piercing capability, with the possibility to engage different targets, and high accuracy. The rate of fire with a multibarrel layout is 3-4 times higher than with a traditional single barrel gun.
As basis of the new cannon the 30-mm six barrel naval cannon AO-18 was selected, constructed by V.P. Gryasev and A.G. Shipunov. Development of this cannon was started on 15 June 1963 by a resolution of the Council of Ministers of the USSR, which described the task to a construct Gatling-type multibarrel cannon with a high rate of fire for naval artillery installation, the AK-630. The cannon was designed to fire a new 30-mm shell. However, this naval cannon was too heavy and too powerful for aircraft use.
Before it was installed on the MiG-23BN, the cannon was greatly modified. The weapon was lightened as much as possible. The heavy water-cooling case was removed, and the barrel length was shortened. The size of cannon decreased from 2176 × 295 × 336 mm (length × width × height) to 1877.5 × 252 × 285 mm. The new gun was named the GSh-6-30, and had a weight of about 145 kg (AO-18 – 205 kg) with a rate of fire of 5000-6100 rpm. The muzzle velocity of shell is about 850 m/s. The ammunition load consists of 300 rounds of OFZ (high-explosive incendiary), OFZT (high-explosive incendiary tracer), FZ (high-explosive) or BZ (armour-piercing incendiary) shells with a weight of 400 g. Effective firing range against ground targets is about 1200-1600 meters, against airborne targets – 200-600 m. (Estafiev Denis)
Page 117 It is reported that the GSh-6-23 has been withdrawn from service in the Su-24 because of an unacceptable level of premature detonations in the barrels. After two Su-24 were lost because of shell detonation in 1983, plus some different problems with gun usage (system failures and etc., very similar to the situation with GSh-6-30 and MiG-27) usage of the GSh-6-23 was stopped by a decision of the Soviet AF Command. But for now all aircraft in the Russian AF are flying with fully operational guns, but without ammunition.
Page 118 The length of the linear magazine of the M61A2 in the F/A-22 is almost 2m: Of course 2m is 6.6ft (6ft 7in), not 6.6in. (Wing Commander C J Jefford MBE BA, in his review for the RAF Historical Society Journal 32 (2004).)
Page 119 A four-barrel derivative of the GAU-12/U has been designed specifically for the F-35: the GAU-22/A. The first model was assembled in January 2006 and commenced testing in February. The GAU-22/A fires at 3000 rpm and is primarily intended for air-to-ground gunnery with a secondary air-to-air capability. Currently it is qualified for PGU-20/U API ammunition and PGU-23 TP ammunition. The F-35A (the USAF, CTOL version of JSF) will have a linear linkless feed system with a capacity of 181 rounds. Qualification of this installation was completed in 2008, with over 50,000 rounds fired in tests and qualification trials. The F-35B (STOVL) and F-35 (conventional carrier) versions will have a missionized pod with a helical feed for 220 rounds. This is in its 36,000 rounds qualification test program.
Chapter Four: Korea and Vietnam
Page 132 It has been reported recently that the armament of at least some AC-130H and AC-130U gunships will be changed again. By the end of 2005, the first modified aircraft will be delivered on which the 25 mm GAU-12 and 40 mm M2A1 Bofors (erroneously described by that source as the M61A1) are replaced by two 30 mm Mk44 Bushmaster II cannon. The reason for the replacement of the GAU-12 is cited as the high cost of maintenance of this weapon; no reason is given for the replacement of the Bofors gun.
Longer-term plans (2008) to equip the gunships with guided weapons are also being evaluated. Apart from Maverick, Hellfire II and guided 2.75 in rockets, one option under study is a 120 mm breech-loading mortar, which could also fire the Army’s M-395 Precision Guided Mortar Munition.
Chapter Six: Helicopters Go to War
Page 151 “four fixed .60 MGs and two rocket pods, plus two more M60s firing from side windows” — probably the fixed guns were M60s as well! (Posted by Do335 on the Military Guns and Ammunition forum.)
Page 160, 170, 180 On 23 February 2004, the cancellation of the RAH-66 Comanche programme was announced. (Dirk Paulfeuerborn)
Page 165 On the Ka-50 and Mi-28: The Ka-50 has won the first combat helicopters in 1986 and 1994 and entered service in limited numbers. A later competition for a combat helicopter with a night fighting capability was won by the Mi-28N, against the opposing Ka-52. The Mi-28N was ordered in production, again in limited numbers, but the Ka-52 is entering service as well, for “special operations.” (Dirk Paulfeuerborn)
Page 169 The new Chinese Z-10 attack helicopter uses a 23-mm “chain gun” that fires the same ammunition as the GSh-23L.
Page 174 The correct rendering of the designation “Bo.105” appears to be “Bo 105” or “BO 105”.
Page 174 German Bo 105 helicopters are not equipped with the Stinger missile. There was a plan to convert 54 Bo 105VBH (the unarmed utility version) to Bo 105BSH-1 configuration, armed with 4 Stinger missiles. One helicopter was modifed and tested in 1989, but after the reunification of Germany the project was stopped. (Dirk Paulfeuerborn)
Chapter Seven: Trends and Prospects
Page 181 See the note on page 119 on the gun for the F-35.
Appendix 1: Installation Table
Page 185 Sources at Dassault confirm that all built versions of the Rafale, including the Rafale N naval version, carry the 30M791 revolver gun, in all their increments (F1, F2, F3). Only the design of the two-seat Rafale M for the French Navy omitted the gun, to allow for a reinforced undercarriage and some other changes, but this version was not put into production.
Appendix 5: Projectile Colours
Page 212 For the .303 in and .50 in Browning cartridges a complementary system was used of colours in the annulus, between the cartridge cap and the base of the cartridge.
For the .303 in: Ball, purple. AP, green. Night or day tracer, Red.
For the .50 in: Tracer, red.