The ‘Firekiller’ is a water bomber derivative of the well-known An-32 turboprop airlifter, developed by Kiev, Ukraine-based Antonov Design Bureau (now known as Antonov Company). It is capable of carrying up to 17,637lb (8,000kg) of water or fire extinguishing agent in four non-removable side-on tanks, installed in pairs on each side, discarding the liquid through systems of flaps. This design solution left the cargo hold unchanged and it can accommodate up to 30 firefighters, paradropped nearby the fire area. The aircraft could be also used without limitations as a cargo hauler with a 14,326lb (6,500kg) payload.
A research project undertaken in the 1980s by the Leningrad Agricultural Institute in then Soviet Union found that a burning forest fire
could be suppressed only when the layer of water dropped on it was at least six centimeters (2.4in) thick. The An-32P was touted as the
first aircraft developed in the former Eastern bloc, able to safely deliver an optimum water flow onto a fire due to its good
maneuverability near the ground, appropriate volume and discharge rate, and the sheer power reserves delivered by its massive engines. This
capable combination provided a reliable suppression of the blazes, with the Firekiller delivering more than six centimeters of water layer
onto the area. The aircraft is also promoted as being capable of use for rain-making purposes, dispersing MP-26 chemical cartridges into
clouds by means of side-mounted UVP-26 dispenser units.
Minimum-change conversion
The compact and agile water bomber that is capable of operating from short, austere airfields, was developed by Antonov in 1992-1993 by converting an existing An-32 transport. It made its first flight in the new guise 16 February 1993. The installation of the external water tanks was straightforward, necessitating local strengthening of the fuselage structure and adding tank mounts. Refilling of the tanks is possible only after landing but taking no longer than 10 minutes. There were no changes made to the aircraft’s powerplant, equipment or avionics suite during the conversion process. The aircraft’s radius of action was limited to 93nm (150km), when operating with a full water load.
The first water drops were made during the 20th test sortie. During the tests it was found that the external tanks created excessive drag and thereby reduced performance below the designer’s expectations. In addition, during a salvo drop of 8 tons of water the aircraft experienced a sudden kick upwards, hitting a positive load factor of 3.3g instead of the calculated 1.4g. The reason for this unwanted control issue was soon discovered. The sharp increase in the vertical acceleration when discharging the tanks in salvo mode was caused by water leaving the tanks, which hit the stabilizer and disturbing the aircraft’s balance for a moment and causing it to fly at an increased angle of attack which, in turn, sharply increased the g-force. The problem was solved by redesigning the drop system in order to avoid water reaching the stabilizer during the discharge sequence.
Precise water-dropping capability
During the flight testing, the Antonov aircrews demonstrated precise water drops within 33ft (10m) of the aim point. Water drops were made at a minimum altitude of 82ft (25m) and at speeds as low as 119kt (220km/h).
At the start of the firefighting operations, water drops were permitted to be made at 98ft (30m) minimum altitude, at a speed of between 117 and 124kts (217 and 230 km/h), with the water covering a swathe up to 160ft (50m) wide and 480ft (150m) long. Later on, however, the minimum permitted drop altitude was lifted to 40m (131ft) due to flight safety considerations, while the speed was set at 130 to 140kt (240 to 260km/h).
The system’s discharge rate in the salvo drop mode is 4,400lb (2,000kg) per second. There is an option to discharge the pairs of tanks one by one, in order to allow two attack passes. The water coverage of the serviced area accounts for about 8.5 liters per square meter (providing a water layer of 8.5 centimeters), which made the Firekiller suitable to tackle high-intensity catastrophic forest fires.
A single aircraft is capable of delivering, at least in theory, up to 512 tons of water per day (equating for 72 passes for dropping eight tons of water in each), operating continuously for 18 hours, while six more hours are allocated for ground servicing. This productivity, equating to 32 tons a hour, could be achieved only in case the distance between the airfield and the fire is 8nm (15km) or less. When the distance is 40.5nm (75km), the productivity drops to 16 tons an hour, and at 81nm (150km), it goes down to 8 tons. This most effective way of using the Firekiller is said to be in a formation of three or four aircraft, attacking the fire one after another.
First operations
While still in testing, the first prototype was called upon to participate in real-world firefighting work in Ukraine. It was in the summer of 1993, near the city of Yalta in Crimea Peninsula, where the Firekiller showed its best in fighting big forest fires. The second prototype was urgently completed and also sent to participate in the firefighting effort in Crimea. Each of the aircraft amassed 10 to 15 sorties a day during the short but intense campaign, showing pretty good effectiveness. About 100 sorties in total were amassed to tackle fires in Crimea, all of them in mountain areas.
The Firekiller was certified by Ukraviatrans, the Ukrainian civil aviation authorities, in March 1995. In the mid and late 1990s, Antonov, together with the Aviant plant which was to produce new An-32Ps, made a number of unsuccessful attempts at selling the type abroad. The first prototype, UR-48004, was extensively used during the campaign to fight forest fires in Portugal and Spain in 1994, together with two other An-32s. All the aircraft owned by Antonov and provided at a wet-lease rate of $2,700 per flight hour.
A total of 545 sorties were made during the campaign on the Iberian Peninsula, which saw one of the aircraft crashing into mountainous terrain in near Valencia in Spain on 6 July 1994. Four Antonov aircrew perished in the crash, together with one Portuguese pilot occupying the right seat in the cockpit and responsible for the communications with the ground, while one Ukrainian crewman miraculously survived the crash. According to Yury Kurilin, an Antonov test pilot who headed the Iberian operation, the aircraft hit a hill slope while approaching its water drop zone against the setting sun in poor visibility conditions. The pilot was trying to drop the water load as precise as possible during his 10th sortie for the day. He however failed to realize that the aircraft was dangerously low, flying well below a hill-top over unfamiliar terrain. As a result, during a sharp pull-up to avoid collision with terrain while simultaneously slamming the engine throttles forward to take-off mode, the aircraft’s speed decayed to 97kt (180km/h) and the aircraft entered a super stall (a surprising phenomenon that has never been encountered during the flight testing). The aircraft then experienced a full loss of control in the pitch and roll axes and the aircraft collided with the terrain only 33ft (10m) bellow the hill-top.
After the crash, as Kurilin shared, the Antonov test team, together with Portuguese pilots, made an in-depth analysis of the fatal sortie. They also developed a procedure for instrument control by utilizing a Northstar Avionics GPS-600 satellite navigation receiver. The two remaining An-32Ps continued their dangerous but highly-prized work in Portugal and Spain until the end of the fire season on 30 September 1994, demonstrating, in addition to its superior firefighting ability, very good reliability with no serious failures or sortie cancellations due to technical issues.
The Firekiller was offered to Greece, Malaysia, Philippines, Australia and Thailand but without any success in the second half of the 1990s and the early 2000s. In addition, Russia, which was expected in the beginning to become a big customer for the aircraft, proved reluctant to buy the type and instead invested in the development of the Beriev Be-200 amphibian, which was taken on strength by the aviation service of the Ministry of Emergency Situations.
The aircraft finally found its launch customer in Libya, and an order for four Firekillers was placed in 2004. Two of these were used aircraft, participating in the testing program and then involved in the operations in Portugal and Spain, in addition to two newly-built examples. Two of the Libyan Firekillers were provided by Antonov – the second-hand machines, priced at US $3 million each - and the other two were built at Aviant. The first of the newly-built An-32Ps for Libya took the air 28 January 2005. The total price for the package including four An-32Ps, training, maintenance services and spare parts was US $27 million. The Firekillers were delivered to Libyan Arab Air Cargo, the cargo division of Libyan Airlines, operating all-cargo services. Since the 2011 revolution, all these aircraft have been grounded.
The next customer for the Firekiller was the Ukrainian Ministry of Interior’s State Service for Emergency Situations, which ordered four aircraft, produced at the Aviant plant by using uncompleted An-32B fuselages, with the first reported delivery in November 2007. In 2018, the Ukrainian Minister of Interior, Arsen Avakov, told the press that there was an order placed for another An-32P, slated for delivery until the end of 2019. Most likely this will be a second-hand machine, built in 1992 and currently owned by Antonov.
The Ukrainian MoI’s An-32Ps, based at Nezhin airfield, are used for firefighting both in country and abroad. In the past, they were sent on missions to tackle fires in Russia, Georgia and Montenegro between 2012 and 2018. In addition to the fire bomber role, with 207 sorties reported in 2018 in Ukraine, these aircraft are also involved in occasional transport missions.