At the beginning of 1966, Václav Kačírek was appointed as the chief engineer of the M601 engine. The requirement for engine power was increased to 383kW (550 hp). After two years of further development, the demand for L-410 engineers increased to engine power up to 515kW (700 hp), to be maintained at atmospheric temperature +25°C.
It was necessary to reconstruct the air path of the engine to accomplish this task. In 1970, Motorlet was asked to achieve engine certification and start mass production reaching hundreds of units per year.
At the end of 1971, the first prototype engines M601-A were supplied to Kunovice for the experimental installation of the airframe XL-410 (v.č.003). However, the first L-410M aircraft (No. 730206) with the M601A was not flown until November 1973. The aircraft was then immediately transferred to VZLU, where it served for flight tests.
In July 1974, another L-410M aircraft (No. 730207) took off with the M601-A engines, which were certified and later operational tests. On April 29, 1975, the State Aviation Inspection Authority for the M601-A turboprop engine issued "Type Certificate of Airworthiness Capability" No.75-03. The engine was L8/C-certified, virtually conforming to the BCAR Part C regulation. It was certified with a double-acting three-liter hydraulic propeller AVIA VJ8.508A with a diameter of 2.5 m. The M601-A had a take-off power of 515kW, KW and a weight of 178kg. The overhaul was set at 500hrs (without any intersections of hotpipes). after the first overhaul, based on the design modifications made to these engines, the time for the next overhaul was extended to 750 hours, which in comparison, was a similar TBO period to the Vedeneyev M-14 radials. By December 1975, the L-410M had been flying for 250 hours.
The engines have been widely used in twin-engine L-410 aircraft for commuter and cargo operations. These engines are also suitable for the following types of aircraft Piper Malibu, King-Air, ST51 Mustang, Comp Air 7 & 10, Legend, Malibu, Navion, and Lancair 4P.
Walter M601-B Turboprop
Following the learnings from the M601-A engines, additional requirements for maintaining higher max take-off power to higher atmospheric temperatures and an increase to overhaul times. The M601-B version was then introduced and included a range of modifications and enhancements:
- two torch lighters to increase trigger reliability
- free turbine guard
- coating the exposed parts of the combustion chamber with nickel solder to increase their service life
- a ramp for water injection into the compressor to maintain maximum take-off power even at higher atmospheric temperatures
- the material of the generator turbine sheet material on the EI 437B has been changed
- an electrohydraulic driver (EHO) of the propeller automatic propulsion system has been introduced
- adjusted fuel regulator for the use of extraordinary elevated and medium extraordinary modes
- other adjustments
With the injection of water into the compressor, the maximum engine output of 515kW could be maintained up to an atmospheric temperature of +30°C. Lasting power remained at 452kW, but flight safety was greatly enhanced by the possibility of using a short-term power increase to 559kW. The reverse power that could be used was 311kW. The design measures and material improvements not only increased the reliability of this version but also allowed to extend the time between general overhauls to 750hrs with a total service life of 2,250hrs after introducing further changes from the 21st production series (November 1981) to 1,000 hours between general overhauls. 3,000 hours was the designated total life of this variant of the engine.
The M601-B was certified by the State Aviation Inspection pursuant to L8/C "Appendix No. 2 to Type Certificate No. 75-03" issued July 28, 1977. It was fitted with a double-acting three-leaf hydraulically adjustable propeller Avia VJ8.508B. The first serial engine (744-100) was passed to the receiving authorities of the MNO on 28th December 1977 and by the middle of 1978 another 10 engines were delivered. Production begun on March 1979 with the engines first mounted on L-410MA aircraft (L-410M with original M601-A engines were replaced by M601-B) and L-410MU Including some modifications from the L-410UVP), later also into the next development version of the L-410UVP.
In July 1980, the M601-B was also certified by the Soviet GAR Supervisory Authority, along with the L-410UVP (as part of it), according to the NLGS-2 (Certificate No. 08-410) as the first foreign aircraft engine ever. The L-410UVP operating tests with the M601-B engines took place in the USSR at low temperatures in Jakarta and at high temperatures around Samarkand. Testing of natural ice was then carried out on the Kola Peninsula. Serial production of the M601-B was completed at the end of 1982. The latest M601-B engine, No. 0824 072, was passed on January 19, 1983. In total, 1,123 engines were produced.
The M601-B’s have been superceded by newer models and therefore are no longer in production or supported by Walter/GE. Unlike some turboprop engines, 'hot section inspections' between overhauls are not required with the M601 range. Maintenance between overhauls consists primarily of filter and screen cleaning, compressor wash, oil change, borescope inspection, ignitor replacement, testing and calibration.
The Walter M601-B engine is a dual-shaft reverse-flow free turbine engine. The gas generator section consists of two axial and one centrifugal compressor stages, an annular combustion chamber, and a single stage axial compressor turbine. The power section consists of a single stage axial power turbine, exhaust system, and a two stage planetary reduction gearbox (15:1) with torquemeter. Engine starting is accomplished using a combination starter-generator and electronic ignition (dual low voltage torch ignitors). An accessory gearbox is mounted on the rear of the engine. The propeller is a Czech. S.S.R V-508B 3-blade full-feathering constant speed type with aluminum spinner.
Turbine engine reliability and performance has long been desired by, but rarely available to the general private pilot community. The Walter M601-B is an outstanding engine in its own right and until recently, was largely found on Let 410 passenger/cargo and Let 19 aerobatic aircraft.
The M601-B weighs just 197kg (418lbs). The recommended TBO for this engine is defined in engine start 'cycles, flight time and calendar time. Factory recommended TBO intervals vary from 2,250-20,000 cycles (depending on type of service and engine series), from 1,500-3,000 hours flight time, and from 5-8 years calendar time between overhauls. However, 300hr inspections are advisable.
For reference, even though the M601-B engine has been superceded and is no longer supported by Walter GE, it can still sell for around $25-30,000. Due to the high operational serviceability of these engines, overhauled units are found to be in the $45,000-$50,000 range.
Log books are present and available for inspection.
Prices: from €15,000 +shipping (depending on which engine chosen).
See below for more information and contact us with your questions.