ONLY FOR HARDCORE TANK BUFFS: The Arjun controversy

This post is a prelude to an article that I'm writing on the recent controversy over the Army’s statement to Parliament’s Standing Committee on Defence, which was tabled in parliament as a part of the Committee’s 29th Report. The part relating to the Arjun, in Para 8.18 of the report, is quoted below:

8.18. During evidence before the Committee, a representative of the Army clarifying the position regarding performance of the Arjun tank submitted as under:-

“Sir, we have just carried out the trial in winter. The tanks have performed very poorly. There have been four engine failures so far. The tanks have done about 1000 km each. There has been a problem. The Defence Minister has been apprised by the Chief. I think two or three days back, he has written a DO letter giving the exact position. So a lot of improvements have to be done before the Army will be satisfied with the Arjun tank.”

The factual position

During the AUCRT in Pokhran, there was NO problem with either of the two engines. The problems were actually with four transmission systems: supplied by Renk AG, from Germany.

The problem: When the oil temperature went up, the oil viscosity was reduced… and the oil pressure was therefore insufficient. As a result, the bearing gave way, and the main shaft in the transmission also got damaged. Pieces were flying around and, when the transmission gearbox was opened, it looked pretty ugly.

The investigations are focusing on three aspects:

1.    The possibility that the use of indigenous oil, rather than German oil, may have led to a failure of lubrication. The CQA (PP)… that is Controller of Quality Assurance (Petroleum Products)… has examined the oil and said that it is of the same grade as the foreign oil. However, the experts from Renk AG are still not convinced. They have taken samples of the oil to Germany to analyse, are will reach a conclusion by Monday, 21st April.

2.    The possibility that recent changes made to the Arjun’s system of dual gear levers might have led to the problem. The driver has a Mode Selector Switch (with options: Forward-Neutral-Reverse)… and also a gear lever (with options: 1, 2, 3, Automatic). So totally, the tank has four forward and two reverse gears. Recently, when the production series tanks began being manufactured, the Gear Lever options were changed to (1, 2, Automatic). In the new system, gears 3 and 4 engage and disengage automatically. In fact, one school of thought amongst the designers is to have just the first gear manual… and then 2-4 automatic, i.e. (1, Automatic).

The CVRDE’s Transmission Group Team has recommended that another Manual Gear lever be introduced. That would be used while tow starting the tank. There are also problems with the logic of gear change in the Pokharan area where the tests are taking place. Unlike the Suratgarh desert, which had heavy sand, the Pokhran desert has hard, flat ground. Since the driving conditions are different, the logic for gear changing has to be different, and the micro-switches that signal the gear changes have to be calibrated differently.

3.    There is also a possibility that a recent change in the supplier of the bearing that failed might have led to the problem. [Renk AG, which manufactures the gearbox, recently changed its bearing supplier.]

Experts from Renk AG are reaching the trial area and also CVRDE, Avadi, on 22nd April. Renk AG is one of the world’s most respected suppliers of transmission systems and it’s prestige is at stake here. A top Arjun designer says, “Renk’s prestige is at stake. I have no doubt they will fix the problem fast.”

Problems with four HSUs

The second problem that the Arjun faced was in some Hydro-pneumatic Suspension Units (HSUs). The Arjun has 7 road wheel stations on each side, which means that each tank has 14 HSUs. With two tanks participating in the trials, there were 28 HSUs that were effectively taking part. Of these, four HSUs failed.

One of them was a genuine failure, in which the HSU’s breather pipe got damaged and sand went in through that. The other three HSUs failed after 2000 km of running. HVF lays down a service life of 2000 km for each HSU, so that was predictable. This was not a problem at all.

It might also be noted that it takes just two hours to replace an HSU in the Arjun. This tank does not have a torsion bar suspension, in which replacing a road wheel station was a major undertaking.

Incidentally, the HSU has been an area where the Arjun’s designers have put in some really serious thinking. The terrain in Pokhran, which is flat and hard, generates in the HSU pistons a low amplitude, high frequency vibration. That is in contrast to heavy sand dune country like Suratgarh, where the HSU pistons undergo a high amplitude, low frequency vibration. In Suratgarh there were no problems, but the resurfacing of problems (albeit after the specified service life) in Pokhran brings to mind the earlier problems in which HSUs were leaking while the tank was being transported by train. The low-amplitude, high frequency vibrations generated by the vibrations of a train were enough to cause the HSUs to leak. That problem was resolved by changing the rings of the floating piston in the HSU. Also, the CVRDE tried out different types of piston rings, including imported ones from Hunger, Germany. Eventually, a life of 2000 km was achieved.

Problems with top rollers

Three or four top rollers also failed. That is being investigated.

Problems with tank Muzzle Reference Sight (MRS)

Of the two tanks undergoing AUCRT, one had a problem with the MRS, which was found to shift when the tank fired. This could have been easily overcome by firing through other means, disregarding the MRS. But suffice to say, the MRS had a problem.

These are very interesting dimensions to the trials in Pokhran, but far more interesting is the way the Army has reacted to them… taking the opportunity to slam the CVRDE for a “substandard” tank. An article on that will be appearing in the Business Standard on Saturday morning.

And, of course, it will be posted here on Broadsword.