Introduction

The L39 advanced trainer is in daily use by the air force's of sixteen countries in Europe, Asia, Africa, and Latin America.

It's rugged and simple design has proved its qualities in every climate from desert summers to siberian winters to tropical jungles. The aircraft's well designed systems result in easy maintenance, excellent reliability, simple pre-flight checks, and no requirement for a full-time ground crew. The airframe has a proven service life of 6000 hours. A turbofan engine with low fuel consumption and low sensitivity to foreign object damage (FOD) is combined with high wing protected air intakes. This makes the aircraft ideal for operations from unimproved airstrips and for training. The excellent handling qualities make it one of the best training aircraft in the world.

Power Plant

The aircraft is powered by a AI-25 TL twin shaft turbofan engine. The control of the engine is hydro-mechanical with an emergency backup circuit. The engine is attached to the airframe by means of four hinges enabling quick removal of the engine after rear part of the fuselage is disconnected.

The engine is automatically started on the ground by means of air starter, that is fed by compressed air from the Saphir-5 auxiliary power unit (APU). In the air, to the engine can be restarted by either the APU or autorotation.

The bypass ratio of the engine is 2.0. Maximum static thrust is 16.87 kN, specific fuel consumption 56.9 kg/kN.hr.

Controls

Elevator, ailerons, and rudder are controlled through the direct mechanical system. Flaps and airbrakes are actuated by electro-hydraulic system. In case of failure, the functions can be performed by an emergency hydraulic system.

Landing Gear

The aircraft has a rugged tricycle undercarriage that is designed to work as well on unpaved runways  as it does on concrete or grass. The main undercarriage wheels are equipped with hydraulically operated double-disk brakes with an antiskid system. The forward retracting nose wheel has a shimmy damper.

Aircraft Systems

Hydraulic System

The main circuit of the hydraulic system provides the power needed to operate the flaps, airbrakes, landing gear, ram-air-turbine, wheel brakes and braking anti-skid devices. Power is supplied by a variable delivery constant pressure pump working at 15Mpa (2000psi). The emergency circuit is supplied by an hydraulic accumulator.

Pneumatic System

Pneumatic canopy seals are supplied by a 2 liter compressed air bottle in the nose compartment.

Electrical System

The main electrical system runs on  28V (DC). The auxiliary electrical system is a  three phase system  (3x115/200V - 400Hz.) In addition to the main system, the aircraft is  equipped with both reserve and emergency systems.

Fuel System

The aircraft's fuel is contained in five tanks in the fuselage, two fixed wing-tip tanks, and two optional under wing drop tanks. Total fuel capacity is 1,995 liters.

Air-conditioning and Oxygen System

The pressurized cockpit is equipped with automatic pressure and temperature regulation. Oxygen masks in both cockpits can be used for long duration high altitude flights.

Anti-G System

An anti-G system protects the pilot from the effect of high load factors during maneuvers by using special suit with automatic regulation.

De-Icing System

The aircraft de-icing system protects the windshield and both air intakes and runs on hot air from the engine compressor.

Ejection System

The ejection system ensures reliable egress of the pilots in the whole range of operating speeds from 150 km/hr up to maximum permissible airspeed from zero height up to maximum ceiling. Two VS1-BR1 ejection seats with autonomous survival kits are installed.

Reliability

Testimony to the reliability of the L39 is proven in the number of L39 aircraft being currently used and in the repeat orders from existing customers. The Mean Time Between Failure in flight is higher than 300 flight hours. The probability that a one hour sortie will be successfully completed is 99.6%. The safety record of the L39, combined with its unique built in features make the aircraft highly cost-effective for its mission.

Servicing

Rapid Servicing and low maintenance cost was one of the main criteria in the development of the L39. For easy servicing and maintenance, the airframe is furnished with large numbers of access doors with quick release locks, and easily accessible from the ground with simple airfield servicing equipment. The engine can be removed and fitted back in less than three hours. All parts of the airframe are replaceable and interchangeable. Overhaul of the airframe is required after 2,000 hrs and overhaul of the engine after 1,000 hrs. Proven airframe service life is 6,000 hrs. 

Specifications