PKP-77M

PKP-77M as a primary flight director instrument

The PKP-77M is an aircraft command flight instrument used as a cockpit attitude and flight director indicator. It displays the aircraft’s spatial position relative to the true horizon and provides command guidance for the pilot. The instrument shows roll and pitch, flight director commands, deviation signals and slip indication, depending on the connected onboard systems. In practical cockpit use, the PKP-77M works as one of the main pilotage references, especially in aircraft where attitude, director and navigation command data are displayed through electromechanical instruments.

Attitude indication by the PKP-77M

The PKP-77M displays aircraft roll and pitch angles using the “view from aircraft to ground” principle. The aircraft symbol remains fixed, while the moving sphere represents the outside attitude picture. This makes the display intuitive for the pilot: the instrument visually shows how the aircraft is positioned relative to the horizon. According to the passport data, the indication error is within ±0.7° at main zero / small-angle marks and increases within specified limits at higher roll and pitch marks. This level of accuracy is important because the instrument is used directly in the pilot’s scan.

Flight director command functions of PKP-77M

Besides attitude indication, the PKP-77M receives command signals and displays them to the pilot through director indicators. These command channels help the crew maintain required flight parameters, such as course, altitude or approach path, depending on the aircraft’s flight-navigation system. The instrument can display roll command, pitch command, course-zone deviation, glide path deviation, altitude command and related signals. The PKP-77M itself is not an autonomous control system; it is an indicator that converts signals from external onboard systems into visual command cues.

PKP-77M connection with onboard sensors and systems

The PKP-77M does not operate as a standalone gyroscope. It receives attitude and command data from external aircraft systems, including precise vertical reference and flight director / navigation equipment. In aircraft applications, it works together with systems that form roll, pitch, course, glide path, altitude and slip signals. This is why compatibility must be checked by the aircraft wiring diagram, equipment list and installed flight-navigation complex. A visually similar instrument may not be suitable if the power supply, signal channels or connector layout do not match the aircraft configuration.

Electrical power and signal channels of PKP-77M

The passport data for the PKP-77M lists several power channels: 27 V DC, 36 V three-phase AC at 400 Hz, and a 5.5 V AC or DC circuit. These supply channels are typical for electromechanical cockpit instruments of this generation, where indication is driven by analog electrical signals and internal mechanisms. Correct voltage, frequency and signal quality are important for stable movement of the sphere, pointers and command indicators. If the supply is unstable, the instrument may show incorrect indications, slow response, vibration of pointers or failure of command cues.

Cockpit operation and service checks of PKP-77M

During operation, the PKP-77M must be checked for stable indication, correct response of roll and pitch channels, movement of command indicators, slip indication, lighting condition and cleanliness of the front glass. Passport notes require the protective glass to remain clean and undamaged. The instrument should not be operated with damaged glass. In tropical or subtropical conditions, the glass should be cleaned more frequently. If pointers stick, the sphere moves unevenly, indications are unstable or the instrument fails control checks, it should not be accepted as serviceable based only on its external appearance.

Supply and documentation for PKP-77M

The supplied passport identifies the unit as “Command Flight Instrument PKP-77M”, passport 6D2.338.019 PS, serial number 0180644771, manufactured and accepted in 1984. The complete supply includes the PKP-77M instrument, mounting screws, washers, spare mounting parts, operating manual and maintenance regulation. For aircraft use, the unit should be checked by passport, serial number, aircraft equipment list, remaining resource, storage history, repair records and conformity with the installed cockpit system.

Product Type: Command flight instrument / flight director attitude indicator
Designation: PKP-77M
Russian Designation: ПКП-77М
Passport Reference: 6D2.338.019 PS / 6Д2.338.019 ПС
Serial Number from Passport: 0180644771
Function: Display of aircraft attitude, flight director commands and deviation signals
Application / Where Used: Aircraft flight director and pilotage-navigation complexes
System / Installation Area: Cockpit instrument panel
Part of System / Included in Set: Flight director / attitude indication equipment
Compatible Aircraft / Equipment: Mi-26, Ka-27, Yak-42, Tu-95MS and other aircraft equipped with compatible PKP-77 / PKP-77M systems, depending on configuration
Instrument Type: Electromechanical command flight indicator
Display Principle: “View from aircraft to ground”
External Data Sources: Aircraft vertical reference, flight director and navigation systems depending on installation
Displayed Parameters: Roll, pitch, roll command, pitch command, course-zone deviation, glide path deviation, altitude command, slip indication and service signals depending on system configuration

DC Power Supply: 27 V, +2.4 / −3 V
Three-Phase AC Power Supply: 36 V, +1.8 / −3.6 V
AC Frequency: 400 ±20 Hz
Additional AC or DC Circuit: 5.5 ±0.55 V
Operating Temperature Range: −60 to +60 °C

Roll Indication Error at 0° and 10° Marks: ±0.7°
Roll Indication Error at 15°, 30°, 45°, 60°, 90° and 180° Marks: ±1.5°
Pitch Indication Error at 0° and 10° Marks: ±0.7°
Pitch Indication Error at 30°, 50° and 70° Marks: ±2°
Roll Command Voltage at 0 Mark: ±0.35 V
Roll Command Voltage at 2 Mark: 5 ±1 V
Pitch Command Voltage at 0 Mark: ±0.35 V
Pitch Command Voltage at 2 Mark: 5 ±1 V
Course-Zone Deviation Current at 0 Mark: ±15 µA
Course-Zone Deviation Current at 1 Mark: 75 ±15 µA
Course-Zone Deviation Current at 2 Mark: 150 ±15 µA
Glide Path Deviation Current at 0 Mark: ±15 µA
Glide Path Deviation Current at 1 Mark: 75 ±15 µA
Altitude Command Voltage at 1 Mark: ±0.2 V
Altitude Command Voltage at 3 Mark: 3 ±0.6 V
Slip Indicator Sensitivity in Zero Zone: ±2°

Minimum Roll Pointer Movement Speed: 150°/s
Minimum Pitch Pointer Movement Speed: 50°/s
Minimum Pitch Command Pointer Movement Speed: 40 mm/s
Minimum Course-Zone Deviation Pointer Movement Speed: 10 mm/s
Minimum Altitude Pointer Movement Speed: 10 mm/s
Insulation Resistance: Not less than 20 MΩ
Atmospheric Pressure Range: 1075 to 7 hPa
Mass: 3.48 kg

Resource Before First Overhaul: 3000 flight hours within 10 years, including 2.5 years storage in manufacturer conservation
Inter-Overhaul Resource: 3000 flight hours within 10 years
Warranty Period: 7.5 years from manufacture
Warranty Operating Time: 2000 flight hours within the warranty period
Scope of Supply: PKP-77M instrument, mounting screws, washers, spare screws and washers
Additional Documentation: Operating manual 6D2.338.019 RE; maintenance regulation 6D2.338.019 RO
Technical Documentation: Product passport 6D2.338.019 PS

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