8AT-7420

Power transfer through the 8AT-7420 collector

The 8AT-7420 works through a collector-and-brush arrangement. Electrical current is supplied to the rotating collector rings, while carbon brushes maintain contact during rotation. This allows the anti-icing system to receive power while the tail rotor is spinning at operating speed. The unit must keep stable electrical contact under vibration, rotation, and changing helicopter operating conditions. For this reason, the condition of the collector rings and brushes is important during inspection, especially if there are signs of unstable heating, poor continuity, brush wear, or local overheating.

8AT-7420 in the tail rotor anti-icing system

The main aircraft system associated with the 8AT-7420 is the tail rotor blade anti-icing system. The current collector supplies electrical power to heating elements installed on the rotating tail rotor blades. These heaters prevent ice build-up on the blade surfaces during flight in icing conditions. The tail rotor is highly sensitive to imbalance and aerodynamic disturbance, so reliable anti-icing power supply is not just a comfort feature. It is part of the helicopter’s protection system, helping preserve controllability and stable tail rotor operation in difficult weather.

Installation area of the 8AT-7420 unit

The 8AT-7420 is installed in the tail rotor area, where the stationary electrical wiring must interface with rotating elements. The assembly works in a mechanically demanding zone: vibration, centrifugal effects, temperature changes, moisture, and contamination can all affect its service condition. The unit must be installed and inspected according to the helicopter maintenance documentation. Particular attention is normally given to brush seating, brush holder condition, collector surface condition, fastening security, wire connection points, and the absence of mechanical damage.

Maintenance role of 8AT-7420 brushes

The brush set is one of the most service-sensitive parts of the 8AT-7420. Brushes must maintain reliable contact with the collector rings without excessive wear, sticking, chipping, or overheating. If the brushes are worn or contaminated, the anti-icing circuit may become unstable even when the rest of the wiring is serviceable. During maintenance, technicians usually check brush length, contact quality, spring pressure, collector cleanliness, and signs of arcing. Replacement must be carried out using the specified brush type and size, not by visual similarity alone.

Aircraft compatibility and identification of 8AT-7420

The 8AT-7420 is used on helicopters of the Mi-8 and Mi-17 family, including Mi-171 variants, and is also associated with Mi-24 applications. Before ordering or replacing the unit, the designation should be checked against the parts catalog of the exact helicopter model and the anti-icing system documentation. Similar current collectors may differ in installation details, brush type, electrical rating, or connection arrangement. For supply, the item should be identified by its full designation, required condition, documentation status, and whether brushes or other consumable elements are included.

Related system equipment: TSV36M313, SO-121VM ver. A, DSL-40T, PE-11M. These positions are grouped by system function and installation context, not as interchangeable replacements.

Confirmed installation context includes Mi-8 / Mi-17 family helicopters. The exact execution and installation position must be checked against the illustrated parts catalogue and documentation for the specific aircraft.