About overhaul

About overhaul


  1. Overhaul of turbojet engines
  2. Overhaul of turbojet engines before the expiration of the service life
  3. Maintenance of turbojet engines according to condition
  4. Servicing of turbojet engines in operation
  5. Repair of aircraft components - landing gear
  6. Repair of aircraft structure elements
  7. Design and equipping of overhaul capacities
  8. Technology transfer
  9. Design and equipment of test benches for turbojet engines

Engines that we overhaul:

  • VIPER Mk. 22-6 for Galeb G-2
  • VIPER Mk. 531 for Jastreb J-21
  • VIPER Mk. 632-46 for Super Galeb G-4
  • VIPER Mk. 632-41 and Mk. 633-41 for Orao  and J-22 and J-22
  • VIPER 632-43 for Alenia Aermacchi MB-339
  • VIPER 22-8 for HJT-16 Kiran Mk. I/IA
  • P13-300 and P25-300 for MiG-21 and MiG 21 BIS

Washing and cleaning parts, dry and wet sandblasting

Washing and cleaning according to all relevant Rolls-Royce requirements:

  • Steam degreasing in accordance with RPS 128
  • Liquid degreasing in accordance with RPS 313
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Defectoscopy (NDT methods)

Within the NDT methods we have:

- testing with liquid penetrants

- magnetic particle testing

- ultrasonic examination

- X-ray examination, radiography

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Regeneration of parts

Regeneration of parts involves the application of the following coatings:

- "High velocity oxy-fuel" coating process (HVOF)

- Plasma spraying procedure

- Flame spraying procedure

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Static and dynamic rotor balancing

The position of the inertial axis of the rotor depends on the distribution of its elements around the circle. If the masses of all mounting units and parts are evenly distributed, the inertial axis coincides with the axis of rotation.

Such a rotor is called balanced. In most cases the masses are distributed unevenly, the inertial axis is movable with respect to the axis of rotation, an imbalance equal to the product of the unbalanced mass and its eccentricity occurs. Such a rotor is called unbalanced. In the case of unbalanced rotors, centrifugal forces proportional to the imbalance and the squaring of the speed of rotation occur.

Dynamic balancing of the rotor is performed on special devices that allow determining the weight and position of balanced weights in two correction planes. Correction planes are called planes perpendicular to the rotational axis and in which the imbalance of the rotor is compensated by removing or adding mass.

Static balancing in ORAO JSC  Bijeljina means balancing of individual disks of which one compressor rotor consists.

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Anticorrosive galvanic-chemical protection



In PVD process, deposition of material is performed atom by atom, through condensation from gas Plasma State into solid state – formation of coating on the surface of workpiece.

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Testing of aircraft engine units on modern DOWTY and AMS Test Cells

Testing of aircraft engine units is performed with the most modern  "DOWTY", "GREER" and "AMS" test cells. Specially designed test cells are universal tools for testing the performance and durability of units, which requires simulation of all operating modes, in which units can be found during the aircraft flight. Grouped into special technological units, modern test cells enable efficient and quality testing of all types of units, all in accordance with the needs of engine overhaul.

Testing of aircraft engine and its components

"ORAO" JSC  performs complete equivalent, homologation and verification tests of aircraft engines and their components. We have two test cells for testing of turbojet engines.

The turbojet engine test cell in Bijeljina is equipped with a modern data acquisition system and is used for testing Rolls-Royce Vipers of all series, it is capable  to test engines up to 10,000 daN thrust.

The test cell for testing turbojet engines in Batajnica is equipped with a modern data acquisition system and is used for testing engines R13-300, R25-300 and RD-33 (II series), it is capable to test engines up to 12000 daN thrust.

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