The Aero Vodochody Delfin & Albatros

v1.0.0 / 01 dec 01 / 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 manufactured 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 proved to be 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 short history of the Delfin and Albatros.

[1] L-29 DELFIN
[2] L-39 ALBATROS
[3] L-39MS / L-59 SUPER ALBATROS
[4] L-139 / L-159
[5] COMMENTS, SOURCES, & REVISION HISTORY

[1] L-29 DELFIN

* The Aero Vodochody organization of Czechoslovakia had been involved with the license production of Soviet jet designs in the early 1950s. In the later part of the decade, the organization initiated the design for 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 was 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 890 kilograms (1,960 pounds) thrust.

"Swiss cheese" 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 ordnance 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:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                10.29 meters        33 feet 9 inches
   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
   _____________________   _________________   _______________________

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 for looks.

In all fairness, however, its handling was docile, the primary selection criteria was reliability and maintainability, and it met those requirements well. It was certainly superior to the aircraft that it replaced, the MiG-15UTI, which had some nasty handling characteristics. Nonetheless, the Delfin was otherwise uncompetitive with contemporary trainers, and only about 200 of the huge production total were ever delivered outside of the Eastern Bloc.

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[2] L-39 ALBATROS

* 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. 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 is a low-wing aircraft with tandem seating, and is powered by a Soviet-built Progress AI-25TL turbofan with 1,720 kilograms (3,790 pounds) 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 are 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 has a French-made auxiliary power unit (APU) for self-starting.

The Albatros is arguably a much more pleasing aircraft than the Delfin, with sporty looks. The wings have a modest leading-edge sweepback of about 6.5 degrees, and a shallow dihedral of 2.5 degrees. The wing is fitted with double slotted flaps to reduce takeoff roll. The horizontal tailplane has a greater sweepback and is "all-moving", though it has conventional elevators as well. The vertical tailplane is sharply swept back.

Fixed fuel tanks are mounted on the wingtips. They are designed to improve flight efficiency by reducing drag, and incorporate landing and navigation lights. As with the Delfin, the landing gear has a wide track and is designed for operation from rough airstrips.

The L-39 is simple to fly and maintain. For example, the rear fuselage is only held on by five bolts, and can be quickly removed for access to the engine. The aircraft also features a large number of access panels, and most maintenance can be conducted without the use of ladders or external platforms.

The cockpit has twin canopies, one for each seat, opening to the right. The two seats are separated by an internal windscreen. The L-39 improves of the Delfin by giving the back seat a reasonable step-up, improving the back-seater's view forward. The cockpit is pressurized and climate-conditioned. Czech-designed VS-1 rocket ejection seats are fitted, which can be used at zero altitude but require a minimum speed of about 150 KPH (93 MPH).

   AERO VODOCHODY L-39ZA ALBATROS:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                9.46 meters         31 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
   _____________________   _________________   _______________________

* Several different L-39 variants have been produced:

L-39C: Standard basic and advanced training aircraft, with "C" standing for "Cvieny" or "Training" in Czech. The L-39C can be optionally fitted with a single stores pylon under each wing for weapons training. The pylons are "wet" and can carry a 150 liter (40 US gallon) drop tank or up to 220 kilograms (550 pounds) of stores, but are rarely fitted in practice.
L-39Cs were sometimes fitted with a camera for simulated gunnery training. Along with service as a trainer, L-39Cs were also sometimes used as hacks, as well as target tugs, towing a sleeve target from a fixed lug on the belly.
L-39V: Single-seat dedicated target tug, used by Czech and East German Air Forces, only eight built. Winch gear was installed in the rear cockpit, with a wind turbine under the belly to provide power, allowing the variant to tow a KT-04 target, which takes off on a three-wheel trolley. These aircraft were painted in an unusual yellow-and-white color scheme.
L-39ZO: Training and multipurpose light attack aircraft, with a reinforced wing, a belly gun pod, and four stores plyons. The "Z" stands for "Zbrojni (Armed)". In initial studies, the variant was assigned the designation "L-39D". Initial flight was on 25 August 1975.
The inner pylon on each wing is "wet", allowing it to carry drop tanks, and 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 in the next entry in this list.
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.
L-39ZA: Improved light attack / trainer variant with a cannon pod under the nose, gyro gunsight and gun camera, modernized avionics, provision for a reconnaissance pod, and stronger landing gear to handle greater weights. However, the engine remained unchanged, and, like the L-39ZO, the L-39ZA cannot carry a full combat load, two crew, and full fuel load at the same time. For this reason, the L-39ZA has mostly been used as a weapons trainer rather than as a combat attack aircraft.
The cannon pod carries a GSh-23 twin-barreled 23-millimeter cannon, with 150 rounds stored in the fuselage. The pod could be removed but was normally fitted. The outer pylons were 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.
L-39ZA/ART: A specialized version for Thailand, originally designated the "L-39ZA/MP", where "MP" stands for "Multi-Purpose". This variant is intended for use as a trainer, light attack aircraft, and target tug. It features a Westernized avionics supplied by Elbit of Israel. First flight of the prototype was in 1992, with deliveries of one batch of 36 in 1993, two more in 1996, and a final pair in 1996.

Over 2,925 L-39s have been built, with deliveries as of 1998 to:

   __________________  ________________________________________________

   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
   __________________  ________________________________________________

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.

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[3] L-39MS / L-59 SUPER ALBATROS

* 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, as 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, as 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:

A strengthened fuselage with a slightly longer nose.
A ZMK DV-2 turbofan engine with 2,200 kilograms (4,850 pounds) thrust, allowing to carry a full combat load.
New cockpit instrumentation, updating the earlier all-analog cockpit layout with a modernized layout featuring a single multifunction display (MFD) and a head-up display (HUD).
VS-2 "zero-zero" ejection seats.
A new single-piece "clamshell" type canopy.
Larger wingtip tanks.

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:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                9.54 meters         31 feet 4 inches
   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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[4] L-139 / L-159

* 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 1,850 kilograms (4,080 pounds) 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:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                9.46 meters         31 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
   _____________________   _________________   _______________________

* 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 2,860 kilograms (6,300 pounds) 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:

Two Allied Signal color LCD MFDs.
Flight visions FV-3000 HUD.
FIAR Grifo-L multimode radar, with eight air-to-air and ten air-to-ground and navigation modes. The radar has the ability to track eight targets simultaneously. The Grifo-L radar gives the L-159 a distinctive long "Pinnochio" nose that makes it relatively easy to distinguish from other variants of the Albatros family.
Honeywell GPS navigation system with ring-laser gyro inertial navigation system backup, along with Bendix-King Distance Measuring Equipment (DME) and VHF Omnidirectional Range / Instrument Landing System (VOR/ILS) units.
Lear Astronics autopilot and stabilization system.
GEC Marconi Sky Guardian 200 radar warning receiver (RWR).
Vinten Vicon chaff-flare dispensing system.
Two Collins VHF/UHF radios.
Raytheon AN/APX-100 IFF transponder, providing compatibility with NATO operations.
MIL-STD-1553 multiplex data bus system.
Night vision goggle compatible cockpit.
"Hands on throttle and stick (HOTAS)" controls.
An "on-board oxygen generation system (OBOGS)" for the flight crew and an "on-board inert gas generation system (OBIGGS)" to provide nitrogen for the fuel system.

It 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:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                9.54 meters         31 feet 4 inches
   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
   _____________________   _________________   _______________________

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, to be delivered in the 1999:2002 timeframe. These were originally all to be L-159As, but now the government is considering delivery of the final 12 or more as L-159Bs. The Czechs have been considering purchase of a new first-line fighter, but given the expense there has been a move towards an pure L-159 force, armed with AMRAAMs to provide effective air defense.

Cost of the L-159 was given at about $15 million USD in mid-1999. Aero Vodochody needs to double existing sales to make a profit on the aircraft. Venezuela and South Africa have considered the type, but so far there have been no foreign buyers. However, the price-performance point of the aircraft is excellent and the company's prospects are good, particularly for their neighbors in Eastern Europe who need to rationalize and modernize their forces and are familiar with the Albatros.

The company's strategic alliance with the US aerospace giant Boeing won't hurt, either. Boeing bought over 35% of the company's shares in 1998 and is now intimately involved with the company.

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[5] COMMENTS, SOURCES, & REVISION HISTORY

* There were a number of unbuilt Albatros variants:

L-39B: A dedicated single-seat reconnaissance variant of the basic Albatros, with cameras taking up the space given to the back-seat flight instructor in the trainer version. It was also to have been capable of being fitted with a "rocket-assisted takeoff (RATO)" bottle for short-field takeoffs.
L-159 Sokol: a single-seat twin-engine attack derivative of the L-39 considered in the 1960s. It was never built, but the L-159 designation was passed on later to the modern ALCA variant.
L-39E / L-39 Mach Trainer: Unbuilt studies for a substantially modified high-speed / supersonic trainer derivative of the L-39.
L-49 / L-49 VTER: Another set of unbuilt studies for a high-speed follow-on to the L-39.
L-39-97: The Russians initiated an upgrade program in the 1990s to keep their L-39Cs flying, with system updates assigned to the Myasischev organizations. However, the status of this "L-39-97" program is uncertain.

* Sources include:

"Aero L-39 Albatros: Trainer With Teeth", WORLD AIR POWER JOURNAL, Volume 3 / Fall 1990, 19:21.
"Aero L-39 Albatros Family Variant Briefing" by Jon Lake, WORLD AIR POWER JOURNAL, Volume 43 / Winter 2000, 116:131.
"Western Performance, Eastern Price" by David M. North, AVIATION WEEK, 23 July 2001, 54:57.

This document began life as notes taken from datafiles obtained from the German FLUG REVUE website, which incidentally is highly recommended.

* Revision history:

   v1.0.0 / 01 dec 01 / gvg

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