DEFENCE MINISTER Berislav Roncevic had promised to resign The most serious presumption of the cause of the fall of the Mi-8 helicopter registered under number H-253, which took place on 9 July 2007 at the Vukovar military barracks resulting in the death of three and the injuring of 8 people, is a failure of the AP-34B autopilot. The autopilot is a device that is capable of bringing the helicopter from the ground to a hovering position and maintains the position and assigned hovering altitude. At that moment it is responsible for stabilising the helicopter's roll and yaw without the need for the pilot to do anything. By his own testimony given before friends, Captain Robert Garic was at great pains to maintain the stability of the fallen H-253 helicopter.

PILOT Robert Garic was unable to stabilise the helicopter despite undertaking all measures He most likely was on autopilot while raising the helicopter from the Vukovar barracks area to a hovering position at an altitude of about 20 metres. At that point the helicopter began to yaw slightly to the left and instead of the autopilot carrying out its function and stabilising the helicopter, it further increased the torque to the left and also increased its roll. It is presumed that Garic then assumed control in place of the autopilot, which he likely turned off, but it was too late. The foot command could no longer prevent the rotation of the machine, he then reduced power, which should have automatically moved the machine to the right.

THE AP-34B AUTOPILOT was an integral part of the parts overhaul that were taken to Ukraine in 2005 Neither the fully depressed right foot pedal, nor a reduction in power, prevented the helicopter's spin to the left. The autopilot navigation box in the Mi-8 helicopter is located in the lower forward section of the cockpit between the seats of the pilot and co-pilot. The Mi-8's autopilot consists of a navigation unit, a command panel, indicators, an amplification block, a directional angular velocity transmitter and a roll angular velocity transmitter. That the cited failure in the AP-34B autopilot unit might have been the cause of the accident was a conclusion arrived at by employees of the Aeronautics Institute at Velika Gorica after they inspected a further three Mi-8 helicopters that had, over the past two to three weeks experienced difficulties with maintaining helicopter stability and control in the initial phases of flight. The inspected autopilot units do not fully carry out their stabilisation and corrective function during individual helicopter manoeuvres but, rather, do the opposite, instead of correcting unexpected roll, pitch and the like, they additionally worsen them and in doing so threaten flight safety.

THE PRESIDENT'S helicopter H-254 has also been grounded as a result of an autopilot failure Considering that the same problems have been found on as many as four helicopters over the past month, including the downed H-253, everything points to a technical failure after all, and not to human error. Nacional has learned that the life of President Stjepan Mesic would also have been in danger because, among other things, helicopter H-254 was also recently grounded as a result of a failure in the autopilot unit. Besides this, on the Mi-8 helicopters bearing registration numbers H-202 and H-212 the same difficulties have also been registered over the past month, so that this can no longer be considered a chance occurrence. With last week's replacement of some components on the AP-34B autopilot unit the employees of the Aeronautics Technical Institute at Velika Gorica put the Mi-8 helicopter registered under designation H-212 in working order.

All of the anomalies and errors in the autopilots over the past month have been registered in the official documentation on the inspection of the helicopters at the Aeronautics Institute at Velika Gorica, so that it cannot be said that these are speculations. Immediately following the fall of the helicopter in Vukovar the first presumptions surfaced on the cause of the fall based on the statements given by eye witnesses concerning the way the helicopter fell, so that the first assumption was that the tail rotor auxiliary motor had failed or that the cable linking the steering unit in the cockpit with vital parts of the helicopter had snapped. There was an idea that there had been a choking of the motor leading to its failure, but a subsequent inspection of all of these parts and the so-called SARPP registration of the operation of all motor parameters did not confirm these suspicions.

THE SARPP 12-DM is a device that records the operation of all vital parts of the helicopter on film At the Aeronautics Institute the commission that is investigating the circumstances of the accident is not able to carry out a complete investigation and inspection of parts of the downed helicopter because the Institute is not equipped to test motors and similar assemblies. That is why the members of the commission have suggested the assistance of Russian experts from the State Aeronautics Council for Accidents based in Moscow, which is able to test each part in laboratory conditions. In previous issues, Nacional has already written that the detailed testing of the motor taken from the H-253 cannot be carried out at the Aeronautics Technical Institute because it is not authorised to do so and lacks the personnel and equipment to carry out the testing. Most of the other important testing can also not be carried out in Velika Gorica, so that the commissions proposal is entirely justified and Defence Minister Berislav Roncevic should answer it positively.

If it is established that the AP-34B autopilot is responsible for the Vukovar tragedy, and considering that the same problem has been found on several other helicopters, then it is the result of the slipshod general overhauls of ten Mi-8 helicopters in Ukraine in 2005 and the installation of parts of suspect quality without the supervision of Croatian experts and without the receipt of documentation on the work carried out. The replacement of the AP-34B autopilot assembly was led on the list of the names of parts that needed replacement under list number 209.

Among other things, this too was a part of the general overhaul contract between the Ministry of Defence and the Ukrainian company Aviakon, brought to Croatia by the director of the Informatika sistemi Company and the top man for spare parts acquisition for the needs of the Croatian Air Force, Djuro Sesar. No one in Croatia knows what warehouses and military junkyards in the Ukraine the Aviakon Company used during the overhaul of the Croatian helicopters because there was no supervision. And although the 2005 general overhaul contract said that employees of the Aeronautics Institute could supervise the Ukrainian experts in order to see whether all of the planned work was carried out, that did not happen.

UA MAGNETIC RECORDING in the form of a diagram records the operation of the motor, the altitude and speed of the helicopter in flight The Ukrainians carried out 60-80 percent of all the necessary overhaul work in their own facilities, but no one knows for sure if they were carried out properly because there are no results of operational testing of the vital assemblies despite the fact that the employees of the Aeronautics Institute requested them. Colonel Zeljko Idek, head of the Directorate for Acquisitions at the Ministry of Defence, is the only one responsible for the contract not being respected, and so, for example, the entire motor assembly of the helicopter was not overhauled, and two cranes installed on the helicopters do not work to this day. Idek allowed the Ukrainians to use expendable supplies in Velika Gorica and that they take parts from Croatian helicopters that had been written off, and install them on those undergoing overhauls, and all of this was an unequivocal breach of contract.

At the Ministry of Defence, following a de-briefing with pilot Robert Garic and a preliminary inspection that did not establish that a cable had snapped on the steering levers or that the motor had failed, and a review of the SARPP 12-DM recordings that indicate the operation of all key parameters, they were aware that the inexplicable instability and loss of control over the helicopter in spite of the pilot undertaking all necessary measures could have happened by the failure of some hydraulic assemblies or the faulty operation of the autopilot, and that means that the cause of the fall was of a technical nature, which would in no way be in their favour.

In order to completely turn the attention from the fact that a technical failure caused the instability, they served the public the idea that the weight of the parlour furnishings in the helicopter and its distribution caused a shift in the aircraft's centre of gravity, and that that was why the helicopter fell. The claim that the fall was caused by a shift in the helicopter's centre of gravity was an indirect accusation of the Aeronautics Institute in Velika Gorica, which installed the equipment.

EMPLOYEES OF THE AERONAUTICS TECHNICAL INSTITUTE warned the Defence Minister and Prime Minister Sanader That there had in fact been helicopter instability previously, however, was confirmed by the official statements given by most pilots during the investigation into the causes of the fall, and the furniture in H-253 was most certainly not the cause. Roncevic was especially keen to see that claims of a shoddy overhaul and a poor system of spare parts acquisition were no longer mentioned in the public, as Nacional has documented revelations of numerous improprieties and illegal carryings-on among high-ranking military officials. Roncevic was informed in writing of all of these irregularities, the breaches of the contract on the 2005 helicopter overhauls, and of the unnecessary acquisition of parts, but undertook no measures against the responsible individuals, so that it is understandable that he would be very much responsible if it is demonstrated that the cause of the accident was a technical failure.

The disconcerting state of affairs at the Croatian Air Force will be further complicated by union activities by the employees of the Aeronautics Institute in Velika Gorica. After the end of the fire-fighting season everything is ready for a strike because of the failure to fulfil the promises and conclusions of the top brass at the Defence Ministry and the Armed Forces Supreme Command on separating the Velika Gorica Aeronautics Institute from the Defence Ministry system and the start of its operation on a commercial basis.