Tank Modernization

(The following article represents the views of the author and not necessarily those of the Department of the Army.) Tank modernization can be defined simply as the modifcation of older tanks to make them competitive with newer tanks. Three ways to achieve this modernization will be addressed here. First, the changes made on the assembly line during production; second, the changes made after production has been completed and the tank has been fielded and third, the changes made in the field by purchasing allied countries to suit their individual needs. Modifiatwns on the assembly line. All tank-producing countries extensively practice this mode of modernization. These changes may be minor modifications as a result of original design deficiencies, major modifications required to keep pace with improvements in potential adversary tanks, or modifications made to incorporate improvements innovated as a result of technical advancements achieved while the tank was still in production. Examples of such changes are numerous. One example is the German tanks during World War II which were extensively modified to keep pace with Soviet tank developments.'

During WWII, the US made extensive changes during assembly line work to improve their capabilities. Beginning in August 1942, theM4 Sherman was modified to incorporate a 76-mm gun to replace the 75mm gun.2 This was just the beginning of many major modifications made to the Sherman tank that resulted in it becoming the most modified tank in the world.

If the Sherman was the most modified tank, the Centurion and the T34 must be close runners-up. The Centurion had 13 marks, or major factory modifications, not to include variants such as bridgelayers, engineer, or recovery vehicles. Centurion main guns have included the 75.2-mm 17-pounder, the 83.4-mm 2O-pounder, and the L7 105-mm gun. Extensive changes have been made in armor, night vision equipment, and other mdifications. The T-34 had at least three major modifcations between 1940 and 1943, retaining various forms of a 76.2-mm gun until 1943 when it was modified to carry an 85-mm gun. In addition, the T34 chassis was used to produce self-propelled guns mounting 100- or 122-mm gum4 Modern tanks also came in different varieties. The Chieftain has had 12 major marks and several minor changes.5 The M60 tank has had four major modifications: the original M60 with the M48-style turret; the M60A1 with improved turret; the M60A2 with the Shillelagh missile; and the M60A3, a product-improved M60A1. Almost all other tanks could be listed as being modified or product-improved in some way during their production runs. The advantage of product-improving during the production run is that increased capability can be built into the equipment at a relatively low cost? Modifitions afcer production. By contrast, cases when the tank is modified after production have been relatively less frequent. Until recently, when a country stopped production of an old tank and began production of anew tank, the older model tanks were retained, but not modernized and were kept in service only until they could be replaced. Rising tank production costs have precluded the complete replacement of one model tank by anew model. Instead, major tank-producing world powers began to replace only about one-half of their existing tank fleet with new tanks. Table 1 lists the tank inventories of several countries. As can be 28 ARMOR seen, very few large countries have only one type of tank in service; therefore, it has become an economic necessity to improve existing tanks. The basic tank may be obsolete or obsolescent, but frequently it can be rebuilt to increase its capability to cope with more modern tanks to improve mobility, to reduce maintenance costs, or any combination of these, for just a fraction of the cost of anew tank. The Soviet Union has the largest tank improvement program of any major world power (40,000-50,000 tanks at current estimates) and the Soviets have never had only one type of main battle tank in service at any one time. The T-54 and T-55-series tanks are probably the tank series with the largest number of modifications. Over the years, most T-54s and T-55s have been retrofitted with external improvements to include infrared night vision equipment and bore Table 1 Tanks in Service in Major Countries Country us UK USSR

France FRG

Greece Iran (prewar) Israel Italy Netherlands Turkey Sweden Switzerland Type of Tank 1825 M48. 9480 M60, 152+ MI

1289 M48. 2437 Leopard 1, 1 00+ Leopard 2 350 M47. 800 M48 875 Chieftain. 400 M47/M48, 460 M6OA 1 1000 Centurion, 650 M48, 810 M60, 400 T 541T-55. 150 T-62, 100 (7) Merkava 550 M47. 300 M60. 745 Leopard 1 468 Leopard 1. 340 Centurion 3000 M47. 500 M48 300 Centurion. 300 S-Tank, 200 lKv-9 1 320 Centurion. 150 Panzer 61. 330 Panzer 68 (Source "The Military Balance 1980-81," The Infernational Institute for Strategic Studies. London, 1980 ) Table 2 Penetration of 100-mm Tank Gun Projectiles Projectile Penetration (mm of RHA at indicated degrees of obliquity at indicated range) 1 OOOM

2000M 0 '60 Deg 0'60 Deg BM 8 (APDS)

390 150 3901 1 50 (Source p 33, "Chinese Armored Vehicles." "Armies and Weapons ' No 50, January 1979 ) evacuators.' It can be presumed that two-plane stabilization and other internal modifications also have been made. The most important modification made to the T-54/T-55 tanks has been the fielding of an APDS round for the main gun. While some may argue that anew round for the main gun does not constitute a modification to the tank, it requires that the gunner's sight must also be modified by anew sight reticle to enable the round to be fired accurately. The fielding of the BM-8,100-mm APDS projectile with its 1,415 meters per second ( d s ) muzzle velocity gives the T-54IT55 main gun a much better performance over the old BR-412 APC-T projectile which had a muzzle velocity of only 916 m /. The penetration of the two kinetic energy projectiles as well as the ZBK-5M HEAT projectile as shown in table 2 reveals their increased lethality. While some may argue that T-55 modifications are not an example of this second mode of modification since the T-55 actually did not go out of production in the Soviet Union completely until 1980: the fact that the T-54s have most T-55 modifications merits inclusion in the second case. The latest Soviet tank modification seen is a probable laser rangefinder mounted on the mantlet of T-55 and T-62 tanks. The use of this rangefinder should improve probability of hit (Ph) at longer ranges.1° The U. S. completed conversion of 2,064 M48 tanks to M48A5 standards in 1980. This conversion basically included adding diesel engines to M48Als and adding 105-mm guns to the turrets of M48Als and M48A3s. Numerous minor changes were also made.” This program followed the one started in February 1962 when 1,200 M48Als were converted to M48A3s by adding diesel engines to the basic M48 hu11.12 The addition of the diesel engine required rebuilding of the engine compartment.

Modifications by Allied countries. Conversion of tanks by other than the producing country is a program adopted by many countries to meet either political or fical constraints. This allows a country to field tanks meeting current standards for fmt-line equipment. The masters of this industrial wizardry are the Israelis.

The first Israeli Army tanks were scrapped, demilitarized tanks.13 The first Sherman tank acquired by the Israeli Army in 1948 had no engine, track, gun, or optical systems. Initially, a 20-mm gun was fitted, followed by a salvaged 75-mm gun.14 Between 1948 and 1951, the Israelis selected the Sherman as their main battle tank and a mixture of various Sherman models were acquired. Some had the original 75-mm gun and some had Swiss surplus Krupp 75-mm M1911 field guns. In 1956, France supplied a number ofM4 Shermans, mounting 76.2-mm guns. These were designated MI or Super Sherman by the 1sraelis.ls The Israelis realized the problems of fielding a tank fleet with a heterogeneous collection of main guns. They were faced with the Egyptian Army’s armor fleet which included T34s and SU-1OOlSU-152 assault guns. At this time France had fielded the CN 75-50 75-mm gun in the AMX-13. Boastinga muzzle velocity of 1,000 d s, the gun was a major improvement over the standard 75-mm gun on the Shermans and in 1954, the Israelis began a program to modify the Sherman to mount the French gun necessitating a redesigned turret. By 1959 the first battalion of modified tanks designated the M5Ol6 was delivered. The Israelis, however, were still using several different types of engines to power the Shermans. Beginning in 1960, the Israelis began a program to fit Cumming’s diesel engines in modified M4A3 hulls.17 While these modifications resulted in improved tanks, the Egyptians had begua to receive JS-3 heavy tanks with 122-mm guns and thicker armor. The Israelis began to seek away of countering the JS-3, and their answer was to adapt another French gun to their tanks. This time they adapted a modified version of the 105-mm CN 105 F1 gun fitted on the AMX-30. Due to the high recoil ofthe CN 105 F1, a shortened barrel was adopted, designated D1504. The new gun had a muzzle velocity of 800 d s instead of the 1,000 m/s of the CN 105 M1. (The same projectile was fired by both guns.) Tanks equipped with this gun were designated M-51. They were converted from M4A1 Sherman tanks by installing the new gun, Cumming‘s 460 horsepower (hp) diesel engine, the E8 HVSS suspension system, and other minor modifkations. The resulting tank had a top speed of 45 km/hr and a cruising range of 270 km.19 Both model tanks served well in the 1967 and 1973 wars. However, as tank technology advanced and Israel received more modern tanks, many of the older Sherman tank variants have been converted to self-propelled artillery or other specialized uses.20 Israeli tank modification has not been limited to the Sherman. In 1960 Israel began to receive Centurion tanks equipped with the 83.4-mm 20-pounder gun. These Centurions had definite reliability problems and the main gun proved difficult to keep in zero. They therefore converted the tanks to carry the British L7 105mm gun and their crews were retrained to improve gunnery and maintenance procedures. While the Centurion became an effective tank, the low cruising range and maintenance requirements of its gasoline engine were still unsatisfactory, and the decision was made to completely modernize the Centurion. A Continental AVDS 1790-2AC 750 hp diesel engine and Allison transmission were installed and other changes made to make the tanks more reliable in desert operations. About 250 of these modified Centurions were ready for service in the 1967 war and performed well in both the 1967 and 1973 wars. A total of 900-1,000 Centurions are believed to be in Israeli stockpiles.21 In 1955 the Israelis had purchased AUX-13 light tanks, but because of their poor performance and heavy losses suffered against the Egyptian T-54s in the 1956 war, they were removed from Israeli armor battalions and limited to reconnaissance use. Between 1960 and 1964 Israel received a p proximately 200 surplus M48 Putton tanks from West Germany in accordance with an agreement negotiated between Israel and West Germany after the onset of production of the Leopard 1.23 Most of these still had the 90-mm gun but one tank company had modified these M48s by adding a diesel engine and a 105-mm main gun.25 These were designated the M48A3 and were in service by the 1967 war. By the 1973 war the Israeli Army had modified all of their M48 tanks to M48A3s. The Centurions and M48s in Israeli service now had the same engine, transmission, and main gun, which greatly reduced maintenance requirements. Modification of Centurion and Putton tanks has not stopped. Recently published photographs taken in 1978 show Centurion tanks with Xenon searchlights fitted and small studs located on the turret glacis plate.26 Similar type studs are seen on Israeli M60A1 tanks in several illustrations in the October 1980 issue of the Japanese magazine THE TANK MAGAZINE.27 These studs are not present on any tanks photographed during the 1973 war. While there is no acknowledgement by the Israelis of the studs’ function, Centurion and M60Al tanks photographed during the 1982 invasion of Lebanon show them fitted with applique armor. The West Germany Army has fielded an applique armor kit for Leopard 1Als. Tanks so converted are designated Leopard lAlAl. The German applique armor is said to increase protection by 30 percent.28 The Israelis are not the only country to extensively modernize armor. Brazil has taken M3 and M3A1 light tanks from WWII and modernized them. At least 80 M3Als were converted to the X1 tank. The major modifcations on the initial prototype included anew diesel engine and the French 90-mm D-921 A-90 F1 gun in anew turret. After completion and testing of the prototype, two new series of tanks were built, using theXl as a starting point. TheXlAl is for the Brazilian Army and uses the M3Al chassis. The XlA2 chassis is new production, that is totally made in Brazil. Both theXlAl and theXlA2 use the Engesa 90-mm gun, a modified Cockeril d i g n. 2 Norway developed a conversion program to modernize its M-24 light tanks. The modernization included fitting anew French 90-mm low pressure gun, diesel engine and automa-januaty-february 1983 29 tic tranmision. Norway has converted 72 M24 tanks to the NM-116 standard. The conversion costs about onethird of what anew tank would &.3l West Germany is also upgrading M48 Patton tanks. West Germany converted at least 650 M48s by adding a 105-nun gun and improved fire contr01.32 Spain has had an ongoing program to modernize its M47 medium tank fleet. More than 300 M47 tanks were converted to diesel power and provided a 105-mm tank gun. The conversion included rebuilding the engine compartment and adding the equivalent of an M60Al add-on stabilization fire control system.33 Tank modernization has grown in importance to the point where the market offers such good opportunities that several foreign and domestic companies have developed modernization packages for export. Israel has a program to modernize M47s with Israeli Military Industries (IMI) installing a diesel engine and 105-mm main gun. Since Israel has few M475, the modifcation program is for export only. The cost of all modifications, including laser rangefinder and NBC equipment is reported to be about $500,000.34 A US manufacturer has developed or licensed several packages for the M24 and M41 light tanks and M4 and M48 medium tanks. The conversions require very few costly modifications to be made to the engine cmpartment. Several corporations offer improved fire control systems and night vision gear for fitting to all the previously mentioned tanks plus the T-54tT-55 and T-62.

Modernization of tanks is now an important consideration for many armies. As newer tanks enter the inventories of major powers, the need to modernize older tanks increases. Newer tanks, such as the British Challenger, US MI, West German Leopard 2, and Soviet T-64, T-72, and T-80, all feature improved mobility, firepower, and protection. Tanks designed 20 years ago may not be able to survive on the battlefield against them.

Most emphasis on modernization has focused on improved powertrains (engine and transmissions), fire control, night vision equipment and guns. Very few improvements in armor protection have been made (excluding some Israeli and West German tanks). A major modification program to the M60 series tanks to include a 1,200 hp engine improved transmission, better fire control, and a hydropneumatic suspension system and a spaced applique armor to be added to the hull and turret has been proposed by private industry. The US Army looked at similar suggestions for the M60Al but ruled them out because of the high In the case of the M60, the US Army simply cannot, at this time, sard to start any major new programs. There are many other programs requiring funding and the line has to be drawn somewhere. Ifthe cost ofthe conversion is $500,000 per tank, such as the M47 upgrade mentioned above, then the cost of converting 1,000 M60s would be $500,000,000. Almost three armored divisions could be equipped with the proposed uparmored M60s at that cost. When that cost, however, is added to the original cost of a M60A3 (with thermal sight) of $953,216, in 1977 dollars, it is more expensive than an M1 tank (given that both the MI and M60A3 were produced in the same year). Thus, for many countries the choice must be to improve their tank fleet by modernization rather than by the purchase of the newest models on the market.

Footnotes 1p. 226-283, Heinz Guderian, “Panzer Leader,” Zenger Publishing Inc., Washington D. C. 20015, 1979 (Reprint of the 1952 Dutton edition). 2p. 210-207, R. P. Hunnicutt, “Sherman, A History ofthe American Medium Tank,” Tarus Enterprises, Belmont, California, 1978. 3p. 20-21, Stephen Tunbridge,“Centurion in Action,” SquadrodSignal Publications, Warren, Michigan, 1976. %. 1-20, J. M. Brerton & Michael Norman, “Profiie 47, Russian T-34,” Profile Publications, Windsor, England, 1972. 5p. 46-48, George Forty, “Modern Combat Vehicles: 1 CHIEFTAIN,” Charles Scribner’s Sons, NY, 1979. 6p. 11, William H. Gregory, “Mods and Pods,” Aviation Week and Space Technology, November 17,1970.

7p. 142-143,YJSAREUFt Pamphlet 30-60-1, Identification Guide, Part One, Volume 111, Armored Vehicles, Tanks and Self-Propelled Artillery,” 15 February 1973. $. 176 & 289, DIA Projectile Fragment Identification Guide-Foreign (U), DST-1160C-029-80.29 February 1980. $. 12, Soviet Military Power, Government Printing Office, Washington DC 1981. lop. 1206, International Defense Review, 811978. lip. 39, “Army Logistician,” MayJune 1980; & p. 33, “Army Reserve Magazine,” Summer 1980.

12p. 13-15, “A “New” Tank and the Block,” “Armor,” September-October. 1980.

1%. 5 & 9-10, David Eshel, “Israel’s Armor in Action,” Eshel Bramit Ltd, Masada, Israel, 1978 (hereafter cited as Israel’s Armor). 1%. 21-24, Simon Dunstan & D. Eshel, “War Data No. 6, “Sherman,” Eshel GMbh, Koln, W. Germany, 1980. (Hereafter cited as Sherman.) ’$.

25-27, Sherman.

1%. 28-29, Sherman.

17p. 30, Sherman.

1%. 30-32, Sherman. ’%.

35, Sherman.

2op. 37-39, David Eshel and Simon Dusdtan, “Centurion, War Data No., 1,” Eshel-Dramit Ltd, Hod Hasharon, Israel, 1979. (Hereafter cited as Centurion.)

21p. 41-44, Centurion; p. 15, Steven J. Zalo “Armor of the Middle East Wara 1948-1978,” Osprey Publishing, Long;, 1981. (Hereafter cited as Middle East Armor); p. 12, Irvine Conhen, “ “Rehabilitation” Still Israel’s Prime Armor Source,” “Armed Forces Journal International,” December 1976.

2%. 25, Israel’s Armor. %. 26, D. Eshel & S. Dunstan, “M-48/60 Patton Main Battle Tank, FV No. 4,” Eshel Dramit Ltd, 1979 (Hereafter cited as Patton MBT); p. 23, Middle East Armor.

2%. 15, Middle East Armor.

25p. 27, Patton MBT.

2%. 46-47, Centurion.

27Cover, p. 3-9, “The Tank Magazine.” October 80, Vol. 3 No. 14, Sensha-Magazine Co. Ltd, Tokyo, Japan (Some information in this magazine is in English, the remainder of the magazine is in Japanese). 2%. Enrim Po, “Tank Retrofitting: New Life For Old Vehicles,” “Military Technology,” 22.

29p. 109-110, Ronald0 S. Olive, “A New Family ofTracked Armoured Vehicles From Brazil,” International Defense Review (IDR), 111981. 3.

957, IDR 6/1979.

31p. 114-115, Peirangelo Caiti and R. A. Riccio, Modem Armor, Squadron Signal Publications, Warren Michigan, 1978. 32p..22, “Improvements to the German M148,” “Armies and Weapons” No. 48, November 1978.

3%. 33-34, “The New Face of Spain’s M-478,” Ground Defense International No. 60, January 1980. (Note: Some other sources do not agree that 105mm guns have been installed on all the M-47Es produced.) %. 51-53, “Modernized M-47 on Trials,” “Defense Attache” No. 111981. 35.309-315, Christopher P. Foss, “NAPCO Power Packs: A New Lease Of Lig For Old Vehicles,” “Jane’s Defense Review,” Vol. 2, No. 4, 1981. 36 p. 9-10. “High Performance M-60A1 Developed” and p. 10-11, Sam Meyers, “No More PIPS for the M-60A1,” “Armor,” March-April 1981. GERALD A. HALBERT graduated from California State University-Fullerton in 1974.

He served with the 1Olst Airborne, 9th Infantry, 82d Airborne divisions, I Corps (ROW US) Group and Xvlll Airborne Corps, 66th MI Group, and Hq, USAEUR. Prior to his retirement, he was assigned to Studies Division, Directorate of Com ba t Developments, USAARMS, Fort Knox, KY.

january-februaty 1983