US Centurion, Part 3.

The_Chieftain: This is the third in a series of four articles about the US’s evaluation of early Centurion tanks. Part 1 is here, part 2 here. This third one has been delayed for a couple of reasons. Firstly, frankly, I’ve been a tad busy. Secondly, the report on Centurion II’s fire control system is pretty much a wall of text. Not a single graph or picture to it, making assessing the 28-page report a little difficult. Ultimately, there is no real way around it, this will be one of the most boring Hatch articles ever. Feel free to skip this one, and come back the following week for the ‘lessons learned’ article. If you’re not familiar with US report systems, they follow a fairly standard format, in which the first couple of pages are a background overview and a superficial overview of the results. The details are found in the appendices, which can be many pages long. Unfortunately, in this case, there’s as much overview as there is detail, so I’ll try picking a few bits here and there, linking to the ‘meat’ of the tests in a PDF, and then do a quick personal assessment. So, onwards. DESCRIPTION OF MATERIEL. a. The Centurion II, mounting a 17-pounder gun, is the forerunner of the Centurion III which mounts a more powerful weapon, the 20-pounder gun. The two tanks are identical except for their main armament and certain modifications incorporated in the latter. The secondary armament of the Centurions consists of a coaxially mounted 7.92-mm Besa machine gun. Four mencomprise the crew. The driver's compartment is located in the right-hand, front corner of the hull. The left, forward portion of the hull is utilized for ammunition stowage. The remainder of the crew operate within the fighting compartment, the loader being on the left of the main armament. b. The gun control systems provide manual traverse and elevation, non-stabilized power traverse and manual elevation, stabilized power traverse and elevation, and emergency traverse at a fixed rate. Powered control is accomplished by the Metropolitan-Vickers all-electric gun control system in which, when desired, stabilization in azimuth and elevation is effected in relation to the rate at which the turret and gun are disturbed by vehicular movements. The primary direct fire control equipment consists of a range gear and periscopic sight which, together, permit mechanical adjustment of range and axial aiming in elevation. Firing can be carried out electrically or mechanically. BACKGROUND. The prototype of the Metrovick gun control system, installed in a Centurion II, underwent preliminary testing in1946. Operational and acceptance tests, using production equipment, followed in 1947. Currently, the Metrovick system is standard with all Centurion II and III tanks. Nevertheless, refinement of the components has continued. Minor modifications were made in 1948in order to improve reliability and efficiency. The test item as installed by this board includes those improvements. This board was directed to service test the Metrovick system for possible application to US tanks. SUMMARY OF TESTS. a. Ease of installation and adjustment investigations were carried out in conjunction with refitting and repairing the gun control system and its related mechanical components. The resultant experience demonstratedthat turretcomponents must be designed and mounted to facilitate installation, adjustment, and unit replacement. The Metrovick system was deficient in these respects, having an excessive number of separate components, especially external cables, all of which were relatively inaccessible. This slowed up not only the physical fitting of the equipment but also the substitution of individual components when carrying out unit replacement procedures. This complexity, in addition, made trouble shooting exceedinglydifficult. Furthermore, the proper functioning of the system depended on the precise adjustment of a number of interrelated controls. Setting up, consequently, was a tedious process and required the services of highly trained personnel. Moreover, this initial adjustment was usually voided when certain key component parts were replaced, necessitating setting up the system again. Operational trimming of the system, on the other hand, was a relatively simple process. It is believed that the deficiencies cited above are a question of design and capable of correction. Projected improvements listed in subparagraph d (3) should greatly simplify adjusting thesystem in its entirety. b. The electrical gun control system, despite deficiencies known to be present, was subjected to intermittent use for a total of 36½ hours between 2 February 1949 and 16 December 1949, a period of 10½ months. During this time the equipment received only routine care and underwent periods of prolonged operation. Nevertheless, the system functioned without abreak-down until mid-December, at which time the traverse gyro failed and had to be replaced. However, judging by experience with the Centurion III, an excessive number of amplifier trims (nine) had to be carried out. This was attributed, at least in part, to misalignment of the elevating gear and to the undetected presence of a. faulty traverse friction switch. c. Limited moving-vehicle firing tests were conducted. In part, this was dictated by circumstances. Comprehensive testing, although originally scheduled, appeared pointless in view of the difficulties involved in drawing subsequent comparisons withUS developments which are to be tested on different courses and with different crews. As a result, an abbreviated stabilized firing program, sufficient to check the effectiveness of firing on the move with the Centurion II, was carried out to determinewhether or not it was worthwhile to utilize the British tank in comparative testing at a later date. Results obtained confirmed the worth of the Metrovickstabilizer. (1) In continuous, head-on runs, closing from 1,500 to 500 yards at average speeds of 8 to 15 miles per hour, 80 percent effectiveness was achieved with shell HE; the number of target effects equaled the number of actual hits. Fifty-five percent of the hits were obtained with 17-pounder shot APCBC on 12- x 12-foot panels during similar runs. The average firing range was approximately 950 yards and, as a rule, the majority of the hits were experienced at ranges short of 1,150 yards. It should be noted that the initial and subsequent ranges were known to the tank commander when the aforementioned firing was carried out. In later firing, only the initial range was known and changes thereafter were based on visual estimates. Under the latter conditions, 83 percent hits and target effects were obtained with 90-mm and l7-pounder shell HE in halting-to-fire engagements using hand elevation and straight power traverse. The same crew, again relying mainly on estimated range data achieved 64 percent hits and target effects with 17-pounder shell HE on nonstop, stabilized runs over the same course and against the same targets.   (2) In the halting-to-fire runs, the minimum standstill time for one shot was 10 seconds, the average being closer to 13 or 14seconds. The interva1 between moving out and the first shot and between subsequent shots in continuous runs varied widely, the shortest experienced being 5 seconds. The rate of fire, as well as the accuracy, was, of course, directly affected bythe nature of the terrain and the speed and adeptness with which it was negotiated.  (3) Under the conditions of the test, the firing interval on nonstop runs was 10 seconds, or less in 30 percent of the instances and was 15 seconds, or under, in 50 percent of the time. On the nonstop runs, the average tank speed was 10 percent higher than the average speed, exclusive of halts, attained on the stopping-to-fire runs. The elapsed time on a given course was 70 percent less for the tank which fired on the move than that for the tank which halted to fire five times in the same distance. d. The current US tank-development program calls for stabilization, in azimuth and elevation, of the main armament of the new light and medium tanks. In addition, each of these tanks is to be supplied with a built-in range finder and computing mechanism. The flow of range datato the computer is to be automatic and the computer, in turn, is to resolve input data and automatically apply superelevation and lead angle to the gun.  (1)The Metrovick system, being of the rate-responsive type and utilizing constrained gyros, may not be suitable for use with fire control devices presently envisaged. A stabilizer employing one or more positional gyros will probably insure greater efficiency. In any event, the Metrovick unit has no provisions for the automatic application of superelevation and lead angle to the gun.  (2) The test stabilizer, however, is adequate for use with conventional sighting equipment wherein superelevation, for instance, is obtained by altering the line of sight. Nevertheless, there are practical limitations to utilizing the Metrovick equipment. In the first place, its use is contingent on the provision of a balanced gun mounting. Secondly, its operation is dependent on related mechanical components, principally the elevating gear and the traverse gearbox, which would be difficult to fit into a turret for which they were not designed. Lastly, the British stabilizer in its present form consists of numerous and, in some cases, bulky components; the limited space in US turrets would cause a hardship.  (3) Despite the foregoing, it appears unrealistic at this time to regard the Metrovick system as out of date or to eliminate it from further consideration, especially since the merits and demerits of a fully integrated system of fire control have not been established and US development-type fighting compartments are as yet unproven by service testing. Moreover, it is conceivable that circumstances,including logistical factors, may force suspension of the requirement for fully integrated fightingcompartments, at least for a certain class of tank. In such an eventuality, the Metrovick gun control system, which is aprovenitem, might prove acceptable, particularly if the following projected improvements are carried to a successful completion.