MSL-3M

MSL-3M in the aircraft external lighting system

The MSL-3M is an aircraft signal lamp beacon used for light marking of airplanes and helicopters in flight. It forms part of the aircraft external lighting system and helps make the aircraft more visible at night, in poor meteorological conditions and during low-visibility operation. The beacon produces periodic flashes that can be seen from different directions, improving visual identification of the aircraft for other crews and ground personnel.

Flight safety role of the MSL-3M beacon

The main purpose of the MSL-3M is to increase flight safety by providing a clear flashing signal around the aircraft. This is especially important during night flights, taxiing, takeoff, landing and operation in poor weather. A working beacon helps other aircraft and ground services identify that the aircraft is powered, moving, airborne or preparing for operation. On transport aircraft such as An-70, An-72 and An-74, this type of beacon is used as part of the standard visual signalling equipment.

Operating principle of MSL-3M

The MSL-3M uses a lamp and rotating optical system. Inside the beacon, an electric motor drives a rotating reflector or optical assembly. As the reflector turns, the lamp light is converted into a directed flashing beam passing through the light filter. This creates the visible beacon effect. The motor circuit and lamp circuit are separate functional parts of the unit, so during troubleshooting it is important to check both lamp operation and rotation of the optical mechanism.

MSL-3M lamps and signal color

Depending on the exact version, the MSL-3M may use halogen lamps or special aircraft lamps such as SM3 28-60. The basic beacon versions normally produce a white signal, while “K” modifications such as MSL-3MK or related MSL-4K variants may be used with a red signal. The final color and lamp type should be confirmed by the aircraft documentation and installed beacon modification. During maintenance, the lamp, light filter, reflector, contacts and protective dome should be inspected together.

MSL-3M with BZ-4 protection block

The MSL-3M may be supplied or installed as part of a beacon complex together with a remote BZ-4 protection block. In this configuration, the beacon and protection block operate as a system rather than as a single standalone item. The BZ-4 block provides protection functions for the electrical circuit, depending on the aircraft wiring layout. When ordering or replacing the beacon, it is important to clarify whether only the MSL-3M unit is required or the complete complex with the BZ-4 block.

Application of MSL-3M on An aircraft

The MSL-3M is used on Soviet and Ukrainian aircraft including An-70, An-72 and An-74. It may also be found on other aircraft and helicopters with compatible external lighting systems, depending on documentation and modification. The beacon is installed in positions that provide good external visibility, usually as part of upper or lower aircraft signal lighting. Exact installation location, light color and wiring configuration should always be checked against the aircraft maintenance manual and parts catalog.

MSL-3M modifications and related versions

The MSL-3M family includes versions such as MSL-3M-2S and related indexed beacon bodies. Some modernized complexes may use updated units such as MSL-4, with different dimensions and configuration. The designations MSL-3M, MSL-3M-2S, MSL-3-2S and MSL-4 should not be treated as automatically identical without checking the aircraft documentation. Differences may include body size, lamp type, signal color, wiring, protection block compatibility and installation requirements.

Supply and documentation for MSL-3M

For procurement, the full beacon designation, modification, signal color, lamp type, required condition and documentation should be stated clearly. The MSL-3M may be supplied as a standalone beacon or as part of a complex with the BZ-4 protection block. For aircraft use, passport or manufacturer documentation should confirm designation, configuration, acceptance status and suitability for the target aircraft. Before installation, the unit should be checked for lamp condition, reflector rotation, dome condition, electrical contacts and compatibility with the aircraft lighting system.

Product Type: Aircraft signal lamp beacon
Designation: MSL-3M
Alternative Designations: МСЛ-3М; MSL-3M-2S; МСЛ-3М-2С; MSL-3-2S; МСЛ-3-2С depending on modification
Function: Light marking of airplanes and helicopters in flight
Application / Where Used: Aircraft external lighting and visual signalling systems
System / Installation Area: External aircraft beacon lighting system
Compatible Aircraft / Equipment: An-70, An-72, An-74 and other aircraft / helicopters with compatible lighting systems depending on documentation
Operating Principle: Lamp with rotating reflector / optical system driven by electric motor
Power Supply: 27 V DC aircraft electrical system
Motor Current: Up to 0.2 A
Lamp Current: Up to 5 A depending on lamp type and modification
Lamp Type: Halogen lamps or special aircraft lamps such as SM3 28-60 depending on version
Signal Color: White for basic versions; red for “K” modifications such as MSL-3MK / MSL-4K depending on configuration
Associated Protection Unit: BZ-4 protection block when supplied as a complex
MSL-3M Beacon Dimensions: 152 × 120 × 102 mm
MSL-3M Beacon Weight: Not more than 1.0 kg
BZ-4 Protection Block Dimensions: 148 × 132.5 × 88.5 mm
BZ-4 Protection Block Weight: Approximately 1.35 kg
Complete Complex Weight: 2.35 ±0.3 kg
Modernized Beacon Body Example: MSL-4 version approx. 200 × 158 × 155.5 mm
Scope of Supply: Beacon unit, light filter / dome, lamps and passport depending on delivery set; BZ-4 block if supplied as a complex
Technical Documentation: Product passport / manufacturer documentation

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