v1.0.4 / 01 apr 09 / greg goebel / public domain
* The Czechs have a long tradition of arms manufacture from the both pre-war days and the years of Communist rule. One of the important products built there during the reign of the Communists was a series of jet trainers built by the Aero Vodochody organization, starting with the "L-29 Delfin (Dolphin)" and then the improved "L-39 Albatros".
These two aircraft were among the most heavily produced jet trainers ever built. The Albatros is regarded as an excellent aircraft with a relatively low pricetag for its capability. Aero Vodochody has now extended the basic L-39 design with Western gear as the "L-159" light attack aircraft in hopes of continuing its success into the 21st century. This document provides a history and description of the Delfin and Albatros.
* The Aero Vodochody organization of Czechoslovakia was involved with the license production of Soviet jet designs in the early 1950s. In the later part of the decade, the organization began design work on a tandem-seat jet trainer, which emerged as the "L-29 Delfin".
The Delfin was designed by a team under Z. Rublic and K. Thomas, and the "XL-29" prototype performed its maiden flight on 5 April 1959, powered by a British Bristol Viper turbojet. The project had of course been implemented with Soviet blessing and knowledge, and in 1960 the Soviets announced a competitive fly-off between the Delfin, the Polish PZL-Mielec TS-11 Iskra, and the Yakovlev Yak-32, with the winner to become the standard trainer for the USSR and its allies.
A second Delfin prototype flew in July 1960, this aircraft being fitted with the production-fit Czech-built Motorlet M-701 turbojet, and was followed in 1961 by a pre-production prototype that was evaluated in the trainer competition in that year. The Delfin was declared the winner, ensuring that it would have a long and heavy production run. The type first entered operational service in 1963. NATO gave the Delfin the codename "Maya".
* The L-29 was a simple and conservative design, some might say too conservative, with a mid-mounted straight wing and engine intakes in the wing roots, a tee tail, and a tandem cockpit with separate canopies hinging open to the right. The back seat was only stepped up by about 15 centimeters (6 inches), giving the back-seat instructor a poor forward view.
The tricycle landing gear, with single wheels on all three legs, was designed
for rough-field operation. The main gear hinged in the wings and retracted
outward in the wings to give a wide and stable ground track. The aircraft
was powered by a Motorlet M-701c-500 turbojet with 8.73 kN (890 kgp / 1,960
lbf) thrust. "Swiss cheese" perforated airbrakes were fitted on either side
of the rear fuselage. The L-29 could be fitted with a "wet" stores pylon
under each wing, allowing the type to carry bombs, rocket pods, or gun pods
for armament training, or two 150 liter (40 US gallon) external tanks. A
gunsight and gun camera could be fitted for gunnery training.
AERO VODOCHODY L-29 DELFIN:
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spec metric english
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wingspan 10.29 meters 33 feet 9 inches
wing area 19.85 sq_meters 213.55 sq_feet
length 10.81 meters 35 feet 6 inches
height 3.13 meters 10 feet 3 inches
empty weight 2,280 kilograms 5,027 pounds
loaded weight 3,540 kilograms 7,805 pounds
max speed at altitude 655 KPH 407 MPH / 355 KT
service ceiling 11,000 meters 36,100 feet
take-off run 550 meters 1,805 feet
range with drop tanks 895 kilometers 555 MI / 485 NMI
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Small numbers of a single-seat "L-29A Akrobat" aerobatic performance variant
were built, with the first flying in 1967. A prototype was also built of an
"L-29R" light attack variant, but as the Delfin's warload was minimal the
idea went no further.
* The Delfin remained in production until 1974, with 3,665 delivered, making it one of the most heavily-produced jet trainers in history. The USSR acquired over 2,000 of these aircraft, with most of the rest going to other Warsaw Pact countries, including Bulgaria, Czechoslovakia, East Germany, Hungary, and Romania. The Poles did not acquire the L-29, preferring instead to stay with their locally-built TS-11 Iskra.
Production quantity was really the Delfin's only major distinction. It could not be called a "bad" aircraft, but it certainly was an uninspiring one, with a low power-to-weight ratio, modest performance, and arguably nothing much in the way of looks. In all fairness, however, its handling was docile, generally a good characteristic in a primary or intermediate trainer, and the main selection criteria was reliability and maintainability. In short, it met its specifications well. It was certainly superior to the aircraft that it replaced, the MiG-15UTI, which had some handling quirks. The Delfin was still otherwise uncompetitive with contemporary trainers, and only about 200 of the huge production total were ever delivered outside of the Eastern Bloc.
* The L-39 Albatros was designed by an Aero Vodochody team under Jan Vlcek as a successor for the Delfin for use for flight training by the USSR and Warsaw Pact countries, as well as Soviet allies elsewhere. Although there was no official requirement for the design, there was substantial interest from the Czechoslovak and Soviet air forces for the new trainer on its merits, allowing development to go forward.
Two initial prototypes were built, the first being for static testing, and the second performing its maiden flight on 4 November 1968. Following successful flight trials, five more prototypes were built, again with one reserved for static testing. Ten preproduction aircraft were delivered beginning in 1971. These were similar to the prototypes, but had bigger air intakes and slightly longer air intake trunks. Production was initiated in 1972, with service trials the following year and volume deliveries beginning in 1974.
* The Albatros was a low-wing aircraft with tandem seating, powered by a Soviet-built Progress AI-25TL turbofan with 16.87 kN (1,720 kgp / 3,790 lbf) thrust. This engine was originally designed for the Yak-40 airliner and modified by the Czech Motorlet organization for the L-39. The engine air intakes were set high behind the cockpit, reducing the chance of foreign-object ingestion and keeping them out of airflow disruptions from the wings. The Albatros also had a French-made auxiliary power unit (APU) for self-starting.
The Albatros was arguably a much more pleasing aircraft than the Delfin, with sporty looks. The wings had a modest leading-edge sweepback of about 6.5 degrees, and a shallow dihedral of 2.5 degrees. The wing was fitted with double slotted flaps to reduce takeoff roll. The tailplane had a greater sweepback and was "all-moving", though it had conventional elevators as well. The tailfin was sharply swept back.
Fixed fuel tanks were mounted on the wingtips. They were designed to improve flight efficiency by reducing wingtip vortex drag, and incorporated landing and navigation lights. As with the Delfin, the landing gear had a wide track and was designed for operation from rough airstrips.
The L-39 was simple to fly and maintain. For example, the rear fuselage was only held on by five bolts, and could be quickly removed for access to the engine. The aircraft also featured a large number of access panels, and most maintenance could be conducted without the use of ladders or external platforms.
The cockpit had twin canopies, one for each seat, both canopies opening to
the right. The two seats were separated by an internal windscreen. The L-39
improved on the Delfin by giving the back seat a reasonable step-up,
improving the back-seater's view forward. The cockpit was pressurized and
climate-conditioned. Czech-designed VS-1 rocket ejection seats were fitted,
which could be used at zero altitude but required a minimum speed of about
150 KPH (93 MPH).
AERO VODOCHODY L-39ZA ALBATROS:
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spec metric english
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wingspan 9.46 meters 31 feet
wing area 18.80 sq_meters 202.37 sq_feet
length 12.13 meters 39 feet 9 inches
height 4.77 meters 15 feet 8 inches
empty weight 3,400 kilograms 7.500 pounds
loaded weight 5,650 kilograms 12,460 pounds
max speed at altitude 750 KPH 465 MPH / 405 KT
service ceiling 11,000 meters 36,000 feet
range, no drop tanks 1,350 kilometers 840 MI / 730 NMI
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* Several different L-39 variants were produced:
L-39Cs are sometimes fitted with a camera for simulated gunnery training. Along with service as a trainer, L-39Cs are also sometimes used as hacks, as well as target tugs, towing a sleeve target from a fixed lug on the belly.
The inner pylon on each wing is "wet", allowing it to carry drop tanks, and the aircraft has a maximum load capacity of 500 kilograms (1,100 pounds). The outer pylon has a maximum load capacity of 250 kilograms (550 pounds). However, the L-39ZO cannot carry a full warload when fully fueled and carrying two crew. It was built as an interim type pending development of the more optimized "L-39ZA", described below.
Possible stores include four unguided rocket pods; two 350 liter (92 US gallon) drop tanks; four 250 kilogram (550 pound) bombs; two 450 kilogram (1,000 pound) bombs; six 125 kilogram (275 pound) bombs; or a reconnaissance pod.
The cannon pod carries a GSh-23 twin-barreled 23-millimeter cannon, with 150 rounds stored in the fuselage. The pod can be removed but is normally fitted. The outer pylons are wired for heat-seeking air-to-air missiles (AAMs) for self-defense, and the type is also capable of carrying a reconnaissance camera pod on the right inboard pylon.
Initial flight of the first L-39ZA prototype was on 29 September 1976. Aero Vodochody continues to sell this variant, and is willing to provide a degree of customization. For example, L-39ZAs sold to Nigeria were fitted with Bendix-King radios and English-labelled cockpit indicators, making them the first of the Albatros family to carry Western equipment.
Over 2,925 L-39s were built, with deliveries as of 1998 to:
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Afghanistan 16 L-39C
Algeria 7 L-39C / 32 L-39ZA
Bangladesh 8 L-39ZA
Bulgaria 36 L-39ZA
Cuba 30 L-39C
Czechoslovakia 38 L-39C / 30 L-39ZA / 8 L-39V
East Germany 50 L-39ZO
Ethiopia 25 L-39C
Iraq 22 L-39C / 59 L-39ZO
Libya 181 L-39ZO
Nigeria 24 L-39ZA
Romania 32 L-39ZA
Syria 55 L-39ZO / 44 L-39ZA
Thailand 40 L-39ZA/ART
USA, private buyers 5 L-39C
USSR 2,080 L-39C
Vietnam 24 L-39C
Yemen 12 L-39C
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Different sources give slightly different numbers of aircraft. A number of
these aircraft have since been transferred from their original users to other
countries. In particular, with the breakup of the Soviet Union, the L-39s
operated by the Red Air Force were distributed among the new nations that had
previously made up the USSR. About 935 were retained by Russia, 440 were
kept by the Ukraine, and smaller numbers were obtained by the various new
republics.
One of the more amusing of these "redistributions" was the fate of seven Libyan L-39ZOs captured by the French in Chad. These aircraft ended up being sold to private buyers, with six going to the US and one going to the UK. In fact, with a number of surplus L-39s on the market, they are proving a popular type with private fliers who can afford a snappy little refurbished jet aircraft at about a half million USD.
Due to the L-39's excellent handling characteristics and agility it has also proven a useful mount for aerobatic demonstration teams, including one from the Vyazma Air Academy in Russia, and the Czechoslovak "Biele Albatrosy / White Albatrosses". The Biele Albatrosy came under Slovak control after the partition of Czechoslovakia. Apparently, a group of US civilian Albatros operators have also formed up their own flight demonstration team for performances at airshows.
* In the 1980s, Aero Vodochody began work on a substantially improved version of the L-39 under the designation "L-39M", where the "M" stood for "Modernised". This particular design was never built, since the organization decided to move a step further beyond it with the "L-39MS", where "MS" unsurprisingly stood for "Modernized Super".
The L-39MS was introduced with the name of "Super Albatros". Only six were built for the Czechoslovak Air Force; a larger buy was disrupted by the partition of the country. 49 were sold to Egypt as "L-59Es" and 12 were sold to Tunisia as "L-59Ts". The Tunisian aircraft were given the local name of "Fennec" after a desert fox.
The Super Albatros is derived from the L-39ZA and looks much like it, but features:
Initial flight of the L-59 was on 30 September 1986, with two more
prototypes flying in 1987. Initial flight of the first production version
was on 1 October 1989.
AERO VODOCHODY SUPER ALBATROS:
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spec metric english
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wingspan 9.54 meters 31 feet 4 inches
wing area 18.80 sq_meters 202.37 sq_feet
length 12.20 meters 40 feet
height 4.77 meters 15 feet 8 inches
empty weight 4,030 kilograms 8,890 pounds
loaded weight 7,000 kilograms 15,435 pounds
max speed at altitude 870 KPH 540 MPH / 470 KT
service ceiling 12,200 meters 40,000 feet
range, no drop tanks 1,570 kilometers 975 MI / 850 NMI
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* In the 1990s, following the fall of the Iron Curtain, Aero Vodochody decided to revise the L-39 to keep it up to date and obtain sales from new markets.
The "L-139" was a further updated Super Albatros, with an Allied Signal /
Garrett TFE731 turbofan engine providing 18.15 kN (1,850 kgp / 4,080 lbf)
thrust, and Westernized digital systems, including a Flight Visions head-up
display (HUD) and Bendix-King avionics. Initial flight was on 9 May 1993.
AERO VODOCHODY L-139 ALBATROS:
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spec metric english
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wingspan 9.46 meters 31 feet
wing area 18.80 sq_meters 202.37 sq_feet
length 12.13 meters 39 feet 4 inches
height 4.77 meters 15 feet 8 inches
empty weight 3,460 kilograms 7,630 pounds
loaded weight 6,000 kilograms 13,230 pounds
max speed at altitude 760 KPH 470 MPH / 410 KT
service ceiling 12,200 meters 40,000 feet
range, no drop tanks 1,650 kilometers 1,025 MI / 890 NMI
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The L-139 never reached production status. The TFE731 engine was in some
ways a step backward from the Progress DV-2 of the Super Albatros. Although
the Western turbofan was more fuel-economical, lighter, and in principle more
reliable, it also produced significantly less thrust, making the L-139
relatively underpowered.
The L-139 did provide a basis for an improved derivative, the "L-159 Advanced Light Combat Aircraft (ALCA)", which is primarily a light attack aircraft that could also be used as a lead-in trainer. It is substantially more optimized for combat than other members of the Albatros family, with cockpit armor protection, plus a centerline stores pylon and three stores pylons under each wing, for a total of seven. It has been qualified with a variety of weapons, including Sidewinder, Maverick, and Brimstone missiles, as well as unguided rockets, bombs, and electronic countermeasures or reconnaissance pods.
The "standard" cannon pod is the ZPL-20 Plamen 20 millimeter gun pod, but others could be qualified. Other stores, such as beyond-visual-range AIM-120 AMRAAM missiles, have been considered.
The L-159 is powered by an Allied Signal / ITEC F124-GA-100 turbofan engine with dual redundant "full authority digital controls (FADEC)" and 28.0 kN (2,860 kgp / 6,300 lbf) thrust. Larger intakes were designed to accommodate the new engine, which is about twice as powerful as the L-39's original AI-25TL engine.
The aircraft is fitted with modernized cockpit instrumentation and controls conforming to Western standards, making a suitable combat aircraft for Eastern European nations trying to mesh their military services with NATO. Features include:
The L-159 also includes a digital "Aircraft Monitoring System (AMOS)" to log the health of the aircraft in flight for readout by service crews on the ground.
There are two versions: a single-seat "L-159A", and a two-seat "L-159B" for
training and operational conversion. Interestingly, both have the same
tandem clamshell canopy. In the L-159A, the back seat area is occupied a
fuel tank and combat avionics, hidden under a cover. In the L-159B, the
back-seater has flight controls and a control panel that largely duplicates
that of the front seat, including a HUD repeater panel.
AERO VODOCHODY L-159A ALBATROS:
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spec metric english
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wingspan 9.54 meters 31 feet 4 inches
wing area 18.80 sq_meters 202.37 sq_feet
length 12.72 meters 41 feet 9 inches
height 4.77 meters 15 feet 8 inches
empty weight 4,160 kilograms 9,150 pounds
loaded weight 8,000 kilograms 17,640 pounds
max speed at altitude 910 KPH 565 MPH / 490 KT
service ceiling 13,200 meters 43,300 feet
range, no drop tanks 1,570 kilometers 975 MI / 850 NMI
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The project was initiated in 1992 following discussions with the Czech air
force, leading to formal specifications in 1993. Rollout of the L-159A
prototype was on 12 June 1997, and initial flight followed on 2 August, with
Aero Vodochody chief test pilot Miroslaw Schutzer at the controls. The
first full-specification prototype flew on 18 August 1998, with initial
deliveries in late 1999.
In 1997, the Czech government ordered 72 L-159s, originally to be initially delivered in 1999 with following deliveries over the next three years, though the first delivery date slipped to 2000. Due to funding problems, only 24 were delivered, the last in 2003, with the remainder built to be sold on the international market. So far there have been no foreign buyers. Four single-seaters were rebuilt into two seat trainers and delivered to the Czech air force in 2007.
The company's strategic alliance with the US aerospace giant Boeing may be helpful in promoting foreign sales. Boeing bought over 35% of the company's shares in 1998 and is now intimately involved with the company.
* There were a number of unbuilt Albatros variants:
* Sources include:
This document began life as notes taken from datafiles obtained from the German FLUG REVUE website.
* Revision history:
v1.0.0 / 01 dec 01 / gvg
v1.0.1 / 01 dec 03 / gvg / Minor cosmetic update.
v1.0.2 / 01 dec 05 / gvg / Minor cosmetic update.
v1.0.3 / 01 may 07 / gvg / Minor cosmetic update.
v1.0.4 / 01 apr 09 / gvg / Minor cosmetic update.
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