US Centurion, Part 3.

The_Chieftain:    (a) The first embraces modification of three major components and is designed to reduce the instability of the traverse servo system and to simplify and quicken the setting up or adjusting of the stabilizing system. (b) The second modification affects the dampening unit in the gyroscopes end is intended to assist in maintaining a constant dampening figure and to increase reliability. © It is also understood that the present Metrovick system is being redesigned in order to reduce the number of separate components, especially external cables, and to reduce its bulk.  e. It was found that, at least from a user's viewpoint, it is difficult to isolate the performance of a stabilizing system from the performance of its associated equipment. In this connection it should be noted that reference 2a above [Parts 1 and 2 of this series – Chieftain], contains an evaluation of the fighting compartment components common to the Centurion II and III. It was also discovered that both the rate and accuracy of fireon the move were affected by the operating conditions encountered in a moving tank and by other factors not present when firing from a stationary platform. Crew efficiency, for example, was noticeably lessened as a result of the random motions of the tank. In fact, in view of the crew's resultant inadequacy under certain conditions, it appeared that there might be a practical limit to stabilizing accuracy insofar as tank armament isconcerned. At the same time, it was evident that conventional fighting compartments did not represent an optimum asfar as fightability on the move was concerned end that the adverse operating conditions, which are to be expected in a moving vehicle, could be tempered considerably by providing suitable crew facilities.  f. It was forcefully demonstrated, as a result of experience with the Centurion II, that the successful solution of the gunnery problems arising when firing on the move required the concerted efforts of two crew members, the gunner and the tank commander. It proved impractical for the commander to turn the execution of a fire order over to the gunner while he,the tank commander, carries out his command responsibilities.  (1) Range and deflection errors were more prone to increase during a nonstop firing run than to decrease, as is the case when firing from astationary tank. Consequently, the gunner could not be expected to correct fire on the move without assistance since this forced him to cope not only with his initial errors in elevation and deflection but also with changes in those elements, especially in elevation, as the tank progressed on its course.  (2) Of necessity, the commander established and applied the initial range, sensed the shot with respect to the target, and applied a corrected range on the basis ofthis sensing and the new position of the tank. The gunner, on the other hand, concentrated on aiming, firing, and correcting his sight picture, a pattern which was compatible with the characteristics of firing from a movingtank.  (3) This experience disclosed no basis for believing that this two-man technique can be modified materially without sacrificing firepower unless an automatic range-rate device can be provided or unless quick, optical ranging by the gunner proves to be feasible while under way.  g. Special training aids were not considered for this idem of equipment since adoption is not recommended.  h. A draft of this report was circulated to interested agencies for comment. Their comments are listed and discussed in Appendix F, Coordination.  CONCLUSIONS. As a result of experience with the Metrovick stabilizer in the Centurion II, Army Field Forces Board No. 2 concludes that:  a. The test item is adequate for tanks employing a balanced gun and fire control equipment similar to that in the Centurion II. b The system will not permit the automatic application of input data resolved by a computer, to the gun in the form of superelevation and lead angle. c. Neither a theoretical or direct comparison can be made between the Metrovick gun control system and United States’ systems until the latter have been service tested. d. The Metrovick equipment, being of proven worth, should be considered for use in US tanks in the event that US development-type stabilizers are not successful. e. The full effectiveness of stabilizing the main armament of a tank can only be realized by considering, in the design of the fighting compartment and its components, the problems peculiar to firing from a moving vehicle.  RECOMMENDATIONS. Army Field Forces Board No. 2 recommends that a. The Metrovick gun control system be considered a satisfactory installation for tanks which feature a balanced gun and a conventional fire control system. b. A new Centurion III tank embodying the latest type stabilizer and modifications be furnished this board for further test, and the Centurion II be returned to United Kingdom control.  H.H.D Heiberg Colonel, Armor President   So that's the overview. Here's some of the meaty data, in this PDF. Chieftain's commentary. It is interesting to observe how the US Army is learning about a technology which we take for granted today. Although the US had had stabiliser systems in its tanks for several years, by this point, they were of such dubious effectiveness that it was not uncommon for units in the field to simply remove them from the tanks, and, in theory at least, were an order of magnitude below the dual-axis stabilisation that the British had implemented into the Centurion. In practice, of course, the dual axis stabilisation still didn't provide a true fire-on-the-move capability, but it was certainly an improvement, at least at medium and close ranges. Until the advent of coincidentally-fired stabilised sights in the 1970s, as opposed to a stabilised gun, this would prove to be an elusive capability. Note that in the report above, even the theoretical advantage of the stabilised sight when firing from the short halt seems to be more conceptual than in fact, presumably the crew was conducting the full ranging process. The two notable conclusions were the fact that gunning in such a tank as Centurion was now back to being a two-man process, no longer could the gunner be left to his own devices while the vehicle was moving. The other was the realisation that there was more to firing on the move than simply stabilising the gun, the entire crew needed to be stabilised. Part 4 of this series is the observations of the Armored Board on the difficulties of the crew when firing on the move. As for the system itself, the other point to note is that the US had decided, basically, to skip a generation in stabilisation systems, by incorporating the ballistic computer into the system. In Centurion II, it was still necessary to manually apply the range and superelevation (The amount the gun has to aim above the sight-target line to counter the drop caused by gravity). The US Army wanted a system which would do this automatically, the gunner would just put pip on target and the system would take care of the rest. That this would prove to be easier typed than done, of course, they had no way of knowing at this point. So, overall, the US generally liked Centurion. They appear to have considered it to be inferior to the new generation of tanks they were designing, but quite competent for an already-extant vehicle. Some features, like the tracks and transmission, they didn't like. Some, like the stabilisation system and general capability, they did. The engine power they deemed insufficient for the future tank. The entire evaluation process was more of a learning experience, learning some lessons, both good and bad, from the tank the British had built, it was never an attempt to comparatively rate the tank in order of preference. As ever, my Facebook page remains here, my Youtube channel here, and Twitch stream (Every Tuesday, and occasional evenings) is here.