Tumansky R-25
The Tumansky R-25 is a turbojet engine, which is seen as the ultimate development of Tumansky R-11. It was designed under the leadership of Sergei Alekseevich Gavrilov.
| R-25 | |
|---|---|
 | |
| Tumanski R-25-300 engine in Karhulan ilmailukerho Aviation Museum | |
| Type | Turbojet |
| Manufacturer | Tumansky , UMPO NPP Motor |
| First run | 1971 |
| Major applications | Sukhoi Su-15 Mikoyan-Gurevich MiG-21 |
| Number built | 3,200 |
| Developed from | Tumansky R-11 |
Design and development
The Tumansky R-25 was designed as a replacement for Tumansky R-13 in MiG-21 fighters. R-25 is a two-spool axial-flow turbojet featuring a new compressor with increased overall pressure ratio and airflow, variable two-stage afterburner, and greater use of titanium.
The R-25 jet engine's specialty was the addition of a second fuel pump in the afterburning stage. Activating the ЧР (rus. "чрезвычайный режим" - emergency mode) booster feature allows the engine to develop 96.5 kilonewtons (21,700 lbf) of thrust under 2,000 metres (6,600 ft) of altitude. The limit of operation is 2 minutes in practice and in war, as further use causes the engine to overheat and potentially explode. Use of EPR requires engine take-out inspection upon landing and every minute of its use counts as one full hour of engine runtime on the logbook. This further shortens the already limited cycle time of Soviet made engines between industrial-level overhauls and adds great cost.
The R-25 engine was used on the MiG-21bis and the Sukhoi Su-15bis. A total of 3,200 R-25 were built between 1971 and 1975. The engine was also built under license by HAL in India for its fleet of MiG-21bis.
Specifications (R-25-300)
General characteristics
- Type: Afterburning turbojet
- Length: 4,615 mm (181.7 in)
- Diameter: 1,191 mm (46.9 in)
- Dry weight: 1,212 kg (2,670 lb)
Components
- Compressor: Two-spool axial compressor 3 LP stages, 5 HP stages
- Combustors: Cannular 10 burners
- Turbine: 1 HP stage, 1 LP stage
Performance
- Maximum thrust:
- 40.2 kilonewtons (9,000 lbf) [1]military power
- 67.2 kilonewtons (15,100 lbf) max afterburner
- 96.5 kilonewtons (21,700 lbf) CSR mode
- Overall pressure ratio: 9.5:1
- Turbine inlet temperature: 1,040 °C (1,904 °F)
- Specific fuel consumption:
- 93 kg/(h·kN) (0.91 lb/(h·lbf)) at idle
- 98 kg/(h·kN) (0.96 lb/(h·lbf)) at maximum military power
- 229 kg/(h·kN) (2.25 lb/(h·lbf)) max afterburner
- 340 kg/(h·kN) (3.34 lb/(h·lbf)) max afterburner with EPR.
- Thrust-to-weight ratio: 5.6 (max afterburner)
