Motorlet M-701
- the first Czechoslovak jet engine of domestic design
It was developed between 1957 and 1960 at the Ján Šverma Plants in Jinonice by developers under the leadership of Ing. Radu and Ing. Pospíšil. Both of them had already worked on the development of the M710 engine with a projected ťah of 850 kg. However, this engine remained only at the design stage because the axial compressor was too sensitive to sucked-in objects.
The new engine, designated M-701, was therefore equipped with a single-stage radial compressor. The reason why such emphasis was placed on reduced sensitivity to sucked objects was that the engine was intended for a jet trainer Aero L-29 Dolphin designed also for operation from unpaved (e.g., grassy) surfaces. The Ďother requirements were that the new engine should be low-maintenance, ľagile and fuel-efficient. All these conditions were met by the engine, so it is not surprising that the main designers were awarded the Klement Gottwald State Prize for its development.
The first ground tests of the engine took place in 1958, it passed flight tests mounted in place of the rear gunner of the Il-28 bomber. It was first fitted to the L-29 in July 1960, whenď by then a prototype Dolphin was flying with a Viper V8 Mk20 engine ťah 795 kg. In total, approximately 8,750 M-701 engines were produced between 1961 and 1992. During these years, the engine design did not change, only the engine resource changed. The M701b-150 was used from the third L-29 prototype and had a resource of 150 hours, the M701c-150 had a resource of 250 hours, the M701c-400 had a resource of 400 hours, and the M701c-500 had a resource of 500 hours and a total service life of 1500 hours.
Technical description:
The M-701 engine had a single-stage centrifugal compressor with 61 impeller blades and a single-sided air inlet at the front. The turbine was axial, single-stage, mounted flush to the rear end of the rotor. An inner cone was fixed in the outlet diffuser. At the top of the inlet housing was the actuator enclosure (fuel pump, dynamo, hydraulic pump and tachometer). The oil was at the bottom of the inlet cabinet. The turbine disk and blade feet were air cooled. The electrical system operated at 28V. The starter was electric.
The direct current combustion chambers were seven in total and were slightly rotated in the direction of engine rotation. This helical arrangement of the chambers was chosen in consideration of the L-29 fuselage designers' requirement for the shortest possible engine bay. The inlet elbow of the combustion chamber formed one unit with the compressor casing. The flames (the time in the combustion chamber where the mixture is formed and the combustion and mixing takes place) were stored in the combustion chamber jackets on three telescopes. The combustion chambers were connected to each other by cross tubes. The spark plugs were located on the second and sixth chambers
The ignition of the fuel when the engine was started took place in the two opposite chambers (the second and sixth chambers mentioned above) by means of an electrical discharge on the low-voltage condenser spark plugs. In the other chambers, the fuel was gradually ignited through the combustion tubes by which the individual combustion chambers were interconnected around the perimeter.
The fuel system was duplex, which means that it had two fuel circuits and two sets of injection ports in the fuel nozzles. The first circuit was referred to as the so called small gas, for higher modes the second circuit, the so called big gas, was brought into operation. The reason for this arrangement was to make it easier to achieve stability of the fuel system control over the entire engine speed range.
TTD
maximum diameter: 896 mm
height: 928 mm
length: 2067 mm
dry weight: 330 kg
compression ratio: 4.3 : 1
air flow: 16.9 kg/s
ťah
- maximum (at 14,900 rpm): 890 hp (8,728 kN)
- Nominal: 800 hp (7,845 kN)
- cruise: 720 hp (7,061 kN)
Fuel consumption: 1,14 kg/kp/h
speed
Nominal: 14,950 rpm
cruise: 14,500 rpm
max. permitted: 15,400 rpm
rpm: 5,400 rpm
Air flow rate: 16.9 kg/s
sources:
Wings of the Motherland
http://www.leteckemotory.cz/motory/m701
Nedelka, M. et al: Slovak Aviation Dictionary, Magnetpress Slovakia 1998
- the first Czechoslovak jet engine of domestic design
It was developed between 1957 and 1960 at the Ján Šverma Plants in Jinonice by developers under the leadership of Ing. Radu and Ing. Pospíšil. Both of them had already worked on the development of the M710 engine with a projected ťah of 850 kg. However, this engine remained only at the design stage because the axial compressor was too sensitive to sucked-in objects.
The new engine, designated M-701, was therefore equipped with a single-stage radial compressor. The reason why such emphasis was placed on reduced sensitivity to sucked objects was that the engine was intended for a jet trainer Aero L-29 Dolphin designed also for operation from unpaved (e.g., grassy) surfaces. The Ďother requirements were that the new engine should be low-maintenance, ľagile and fuel-efficient. All these conditions were met by the engine, so it is not surprising that the main designers were awarded the Klement Gottwald State Prize for its development.
The first ground tests of the engine took place in 1958, it passed flight tests mounted in place of the rear gunner of the Il-28 bomber. It was first fitted to the L-29 in July 1960, whenď by then a prototype Dolphin was flying with a Viper V8 Mk20 engine ťah 795 kg. In total, approximately 8,750 M-701 engines were produced between 1961 and 1992. During these years, the engine design did not change, only the engine resource changed. The M701b-150 was used from the third L-29 prototype and had a resource of 150 hours, the M701c-150 had a resource of 250 hours, the M701c-400 had a resource of 400 hours, and the M701c-500 had a resource of 500 hours and a total service life of 1500 hours.
Technical description:
The M-701 engine had a single-stage centrifugal compressor with 61 impeller blades and a single-sided air inlet at the front. The turbine was axial, single-stage, mounted flush to the rear end of the rotor. An inner cone was fixed in the outlet diffuser. At the top of the inlet housing was the actuator enclosure (fuel pump, dynamo, hydraulic pump and tachometer). The oil was at the bottom of the inlet cabinet. The turbine disk and blade feet were air cooled. The electrical system operated at 28V. The starter was electric.
The direct current combustion chambers were seven in total and were slightly rotated in the direction of engine rotation. This helical arrangement of the chambers was chosen in consideration of the L-29 fuselage designers' requirement for the shortest possible engine bay. The inlet elbow of the combustion chamber formed one unit with the compressor casing. The flames (the time in the combustion chamber where the mixture is formed and the combustion and mixing takes place) were stored in the combustion chamber jackets on three telescopes. The combustion chambers were connected to each other by cross tubes. The spark plugs were located on the second and sixth chambers
The ignition of the fuel when the engine was started took place in the two opposite chambers (the second and sixth chambers mentioned above) by means of an electrical discharge on the low-voltage condenser spark plugs. In the other chambers, the fuel was gradually ignited through the combustion tubes by which the individual combustion chambers were interconnected around the perimeter.
The fuel system was duplex, which means that it had two fuel circuits and two sets of injection ports in the fuel nozzles. The first circuit was referred to as the so called small gas, for higher modes the second circuit, the so called big gas, was brought into operation. The reason for this arrangement was to make it easier to achieve stability of the fuel system control over the entire engine speed range.
TTD
maximum diameter: 896 mm
height: 928 mm
length: 2067 mm
dry weight: 330 kg
compression ratio: 4.3 : 1
air flow: 16.9 kg/s
ťah
- maximum (at 14,900 rpm): 890 hp (8,728 kN)
- Nominal: 800 hp (7,845 kN)
- cruise: 720 hp (7,061 kN)
Fuel consumption: 1,14 kg/kp/h
speed
Nominal: 14,950 rpm
cruise: 14,500 rpm
max. permitted: 15,400 rpm
rpm: 5,400 rpm
Air flow rate: 16.9 kg/s
sources:
Wings of the Motherland
http://www.leteckemotory.cz/motory/m701
Nedelka, M. et al: Slovak Aviation Dictionary, Magnetpress Slovakia 1998
