Remote control system SDU-10MK (aircraft SU-30MK)

After reading the article Digital airplanes , I decided to write my own small review of the domestic development - Remote control systems SDU-10MK.

From 2007 to 2009, I worked at the instrument-making enterprise ( Elara , Cheboksary) as the lead engineer for this product. I am writing more from memory, as I am currently working elsewhere and do not have access to technical documentation. There is only a summary. The product is not a secret.

SDU-10MK (SDU-10MK ser. 2) is a 4-fold duplicated analog-digital aircraft control system in the longitudinal, transverse and track channels. The system replaces mechanical control wiring. This system is installed on SU-30MK aircraft ... (Mainly for the Indian Air Force)

The composition of the product

• 2 dual power supplies. The CDS is supplied from two independent DC sources with a voltage of 27V, operating in a battery buffer, and two independent sources of three-phase alternating current with a voltage of 115V and a frequency of 400 Hz. Withstands short-term DC voltage peaks up to 50 volts. The CDS is a life support system. The plane will simply fall if the SDU refuses
• Calculators. Combined in several units and a closet. In total, they consist of 60 modules (read - printed circuit boards). They process signals from sensors and issue executive signals to steering gears. The calculators work simultaneously and form the average resulting signals. The system continues to operate with two independent failures in different channels of calculators. That is, if one of the calculators fails, its output signals begin to differ from those of other calculators. When the threshold is exceeded (downgraded), the calculator is turned off and a signal is sent to the voice informer and to the control panel. You can try to restart it from the control panel. With several failures, there is nothing to compare the signals with and the system goes into tight coupling mode (In this mode, it is almost impossible to control the fighter, since it has an unbalanced aerodynamic configuration and it constantly leads away). There was not a single catastrophe associated with the failure of SDU-10MK. The accident was like one.
• Sensors. Transform various physical parameters of flight into electrical signals. The sensors in the CDS are completely independent of other systems. That is, for example, the navigation complex (PNK) and the CDS have sensors similar in functionality. All sensors are 4 times duplicated. The CDS "removes" the following flight parameters:
  - Static and dynamic pressure (DBP, DDD - absolute pressure sensor, differential pressure sensor) for measuring the speed and altitude of flight. These parameters need to be known, because at different heights different air density, and at different speeds different resistance
  - Angular velocities (ALS, BDG - angular velocity sensor, gyroscopic sensor unit). Required to determine the angular velocity of rotation around their axes. SDU instantly returns the plane to its original position with any deviations of the airframe
  - The position of the control knob and pedal (DPR - position sensor redundant). These sensors convert the position of the control knob in two planes (roll, pitch) and pedals (course) to an electrical signal.
• The remotes. PP, PU - control panel, control panel. Designed to perform a CDS performance check and CDS control during operation, as well as to monitor performance and restart the system during flight.
• Steering cars. Designed to convert electrical signals into mechanical SDU. Mechanical signals are pre-amplified by hydraulic machines that are not included in the CDS

Modes of operation

The CDS operates in several modes: take-off, flight, refueling. Modes differ mainly in the transfer coefficients and the functioning of individual deflected surfaces. For example, in the "refueling" mode the plane moves much smoother than in the "flight" mode. During the flight, the system constantly analyzes the position of the aircraft in space, the speed and direction of flight, and controls the flaperons, toes, front horizontal tail, rudders and height, as well as the deflection angle of the nozzles in the vertical plane.
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The system has limiter limit modes that do not allow the pilot to take the aircraft beyond its capabilities. When approaching the limit modes, the pilot's hand begins to tremble powerfully, as if the plane is now falling apart, although in reality it is an imitation.

Production technology and quality control

The system is fully implemented on the domestic element base. The manufacturer has its own machine shops, a workshop for the production of printed circuit boards, a shop of microelectronics. The system is not sealed. All printed circuit boards have a waterproof coating in the form of 3 layers of varnish. Particularly sensitive boards are coated. Bearing structures are manufactured on CNC machines.

Quality is controlled at all stages of production by the workshops themselves, the Quality Control Department and the military mission. The test report of the product is commensurate with the 96 sheet magazine. After production, the system is tested for approximately 2 weeks.

Rest

The system passes the most severe tests, and in my opinion, this is the most enduring electronic product on the plane. It is tested at temperatures of -60..60 degrees, shakes for hours on vibrostands, contaminated with salts, sand, mushrooms, and vapors. The system weighs about 120 kg. and is very expensive, but it is a commercial secret of the manufacturer.
At the moment, more modern digital counterparts (for example, KSU-35 ) have been developed, but SDU-10MK is still being produced and successfully used.

Figure 3 shows the power supply unit BP-58 from SDU-10U, S (SU-27) after testing at low temperature. This is an older system that is still being released.

PS Transferred to popular science. Thank!