Thanks for the link, Brian, very informative. The two photos you mention are shown below.
I ran the text through google translate and edited it a bit, so here it is, to save everyone else the bother!
XM140 WECOM ARMAMENT SYSTEM
In this post I will talk about the XM140 30mm automatic cannon and its major subsystems.
Despite being unknown to most, the XM140 had a certain role in the development of automatic cannons to attack helicopters. In fact, while the present day commonly sees 30mm weapons on board aircraft such as Apache, Tiger and Havoc, at the time of the debut of the XM140 was one of a kind.
In the fifties and sixties calibres higher than 12.7mm were exceptionally rare. It was mostly guns for fighter aircraft adapted and mounted on handmade installations or semi-handicraft made in a limited series (e.g. Mauser MG 151 of the French Alouette in Algeria and M24A1 American Huey in Vietnam). The importance of the XM140 lies mainly in the fact that it was the first real autocannon specifically designed for a combat helicopter
The XM140 had automatic electrical feed to a fixed weapon breech and single barrel actuated by a cylinder cam. The XM140 consists of two masses: the first recoiling; the second does not recoil (or fixed). Receiver, barrel, drum cam and breech block are components of the recoiling mass. Feeder, support, motor, clutch and the feed system are part of the mass that does not recoil.
The XM140 was driven by a 2.5 hp ac 28V motor. The nominal rate of fire was 400 rounds per minute, but it varied depending on the voltage. It was air-cooled and had an electro-mechanical feed. In the event of a jam and/or faulty ammunition, the weapon automatically ejected the ammunition and loaded the next round.
There was a muzzle brake with six channels on each side in order to mitigate the effects of recoil.
- MAIN FEATURES OF XM140
Designer: Springfield Armory
MV: 670 meters / sec.
rate of fire: 400 rounds / min
recoil-based operating system
Closing system: cam
Loading System: Electro-Mechanical
Ammunition: XM552, XM554, XM669
maximum range: 3000 meters
Barrel length: 660 mm
Maximum length: 1530 mm
maximum width: 123 mm
Depth maximum: 368 mm
Weight: 63.5 kg
The main ammunition of the XM140 was the XM552 dual-purpose high explosive grenade based on a 30x100B caliber cartridge.
The XM552 was developed at the Picatinny Arsenal in 1965. The head of the projectile was of the dual-purpose type, based on a shaped explosive charge. The length of the complete ammunition was approximately 178mm and weight little more than 400 grams.
The long and difficult development of this weapon began under the Kennedy administration in 1963, when the US Army Weapons Command issued a requirement for a new generation of cannon intended for armed helicopters (also called gunships) and future attack helicopters.
After the necessary evaluations and comparisons with other weapon systems, the US Army decided to award the project to Springfield Arsenal, which was allocated the task of continuing with the development of the new weapon.
Initially, the project was known under different names:
- Gun Type Aerial System (GTAS);
- Point Area Weapon System (APWS)
- Weapons Command, 30mm (Wecom-30).
It was only when the formal development started (June 1964) that the appropriate official designations were assigned: for the XM130 gun, and XM30 for the first subsystem for the helicopter UH-1.
The XM140 was born mainly for two reasons:
A. totally or partially replace the XM3 2.75 inch rocket launcher normally mounted on the UH-1 Huey of Aerial Rocket Artillery;
B. equip attack helicopters with multi-role weapon capable of engaging personnel and lightly armored vehicles (i.e. APC, IFV etc).
The XM140 was required to be able to hit both area and point targets.
One of the first prototype XM140 shown at Springfield Arsenal, 24 August 1964. Note the 30mm ammunition, very different from what was later adopted for this weapon.
2.1 - Lockheed Cheyenne and first test of XM140
The main recipient of this weapon was actually the Lockheed AH-56 Cheyenne, a futuristic compound helicopter that in 1966 won the Advanced Aerial Fire Support System (AAFSS), organized by the US Army a couple of years before. The XM140, however, could also be installed on other types of aircraft, both fixed wing and rotary.
The programs for the construction and testing of XM140 / XM30 were approved in January 1967, however, various problems with the weapon and ammunition delayed the start of testing at the Aberdeen Proving Ground until September 1968.
In the next ten months the weapon and subsystems were tested first on a UH-1C (XM30 subsystem), and finally on real attack helicopters like the AH-56 (XM52 subsystem) and the AH-1G (XM120 subsystem). Also in that time frame the XM140 was again subjected to modifications aimed at increasing performance and reliability.
3 - WEAPON SUBSYSTEMS
While the weapon was obviously the same, the three subsystems differed greatly from each other:
XM30 armament subsystem
The subsystem XM30 included:
• Two XM140 guns enclosed in as many streamlined pods;
• A pair of feed systems for XM140;
• A container for the ammunition (sited in the UH-1 cargo area);
• Boosters and amplifier junction;
• Control panel and aiming station.
A total of 1200 rounds (600 per weapon) were carried.
This subsystem was the first US Army tested.
XM52 armament subsystem
Lockheed AH-56 Cheyenne
The AH-56 Cheyenne was used instead subsystem XM52, which had a single gun and was installed inside a belly turret. The major components included:
• XM140 gun with ammunition feed system;
• Ventral turret;
• control panel;
• Cylindrical magazine.
The turret could rotate 200 ° to the right and to the left with an elevation and depression, respectively maximum of + 26 ° / -60 °. For security reasons the XM52 was provided with blocks that prevented the weapon’s fire from hitting the aircraft.
The drum contained 2010 rounds and had a diameter of 99cm and length of 101cm.
XM120 armament subsystem
Bell AH-1G HueyCobra
As regards the Cobra it was decided to exploit the space normally occupied by the M29 turret with Minigun and grenade launcher. It came as a prepared installation with the electrically powered XM120 turret.
- SERIES PRODUCTION AND CANCELLATION OF PROGRAM
The Aeroneutronic Division of Philco-Ford won the contract for the construction of the weapons. 70 weapons were manufactured: 11 in 1967, 16 in 1968, 43 in 1969. In 1969 the weapon reached the first stage of limited series production.
Unfortunately the AH-56 Cheyenne, was plagued not only by seemingly insurmountable technical problems, but also by the gradual increase in development costs. Also friction and rivalry with the US Air Force played a secondary role in the fate of this aircraft.
The US Air Force, feeling threatened by the AH-56, did everything in its power to scuttle the Army plans for close air support (CAS). In fact, one of the motivations driving the A-X, which became the A-10, was to convince the political and military leadership that the USAF was able to provide an aircraft able to fulfill CAS functions.
Returning to the Cheyenne, development testing started with the inaugural flight on September 21, 1967; continued between ups and downs until the accident of 12 March 1969 in which the test pilot died. Meanwhile, the Department of Defense, due to budget cuts, had canceled the order for 375 examples signed in 1968.
Lockheed continued development, hoping to get new government funding, but the diversion of funds to other company programs any further effort to an end in August 1972, after making just ten examples. By that time, the XM140 was now well under way and, according to US Army data, the ammunition fired had exceeded 620,000.
Unfortunately, the end of Cheyenne coincided with that of the XM140, which was abandoned shortly thereafter.
Shortly after the end of the Cheyenne program, the US Army launched a requirement for an Advanced Attack Helicopter (AAH), who later would result in the AH-64 Apache and a new gun: the Hughes M230. But that 's another story.
I should add that the site is well worth visiting, as there are lots of photos of the XM140, by itself and installed: https://sobchak.wordpress.com/2010/01/05/xm140-30mm-gun-xm30-xm52-xm120-armament-subsystems/