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Bulgarian nuclear bomber
MiG-23BN Flogger-H

Evgeni Andonov and Alexander Mladenov reveal the story of the Bulgarian air arm’s secret nuclear strike training and strategy during the Cold War.

Source: Aviation News incorporating Classic Aircraft January 2014
Evgeni Andonov and Alexander Mladenov

Other than the USSR the Bulgarian Air Force was the first Warsaw Pact air arm to receive the fighter-bomber derivative of the MiG-23 when its first MiG-23BN Flogger-H squadron was inducted into service in 1976 with the 25th Fighter Bomber Air Regiment. The first 18 of the nuclear-capable jets went to 2nd squadron of the 25th Fighter Bomber Air Regiment followed by 18 more for 1st squadron in 1981.

All these fighter-bomber derivatives of the swing-wing Flogger were nuclear capable from the outset, featuring all the necessary wiring, pylons and cockpit control panels for delivery of the nuclear bomb. A group of carefully selected pilots and maintenance personnel from the 25th regiment was sent to the Soviet Union in September 1980 for a rigorous course in preparation for their nuclear mission. The training was conducted at Martynowskaja airfield, where the Soviet 5th Tactical Air Force’s elite 642nd Guard Fighter Bomber Air Regiment was stationed, operating the basic MiG-27 Flogger-D.

Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H
Bulgarian Air Force nuclear bomber MiG-23UB Flogger-C Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H

Major (later Colonel, now retired) Tsoko Tsokov recalls those uneasy days of high combat readiness and hard training: “We were four pilots from the 25th regiment with good experience on the MiG-23BN Flogger-H – including the combat deployment of conventional bombs and rockets – appointed to attend this top-secret training course on the art of air delivery of nuclear munitions. We traveled to the place of training in our own aircraft, flying directly from our home base of Cheshnegirovo to Martynowskaja, located some 86nm (160km) north of the city of Odessa.” Pilots and maintenance personnel were trained separately, under conditions of very tight secrecy. Technicians were introduced to the specifics of the wiring and control devices that enable the deployment of the nuclear bomb and the functional checks required for the circuits of the weapons control system. They were also given generic information on the design and principle of operation of the nuclear bomb. Practical drills on fitting the nuclear munitions followed, using a single-seater MiG-23BN aircraft ferried from Bulgaria and housed in a hardened shelter under armed guard. There the technicians mastered the skills of installing the adaptor beam used for carrying the Spetzbomba and then suspending the practice bombs, which were brought to the aircraft on a dolly. The aircraft was also required to be started-up and checked with its engine running, still behind the closed doors of the shelter.

The pilots were introduced to the technical details of the RN-28 bomb as well as how to arm and program the weapon before each sortie. They were not given any information about the pre-flight functional checks of the weapons control system or the procedures related to installing the adaptor beam and attaching the bomb – and in turn, the technicians were not taught about the arming procedure.

Soviet RN-28 nuclear bomb

The RN-28 low-yield tactical nuclear bomb featured a programmable control unit, enabling selection of the type of detonation best suited to a target – either airburst at a pre-selected altitude; or on impact with the ground. For an airburst, with the bomb slowly descending under a parachute, detonation was triggered by a command issued by the bomb’s own radar altimeter. In addition the yield of the bomb could be adjusted pre-flight to between one and ten kilotons. The pilot could arm and disarm the bomb as well as change between airburst and ground detonation when his aircraft was in the air, but not change the preprogrammed yield.

Left: Soviet RN-28 nuclear bomb model

“Before this course we were taught that the aircraft carrying the nuclear bomb should be supported on its route to the target by no less than one entire squadron, responsible for sweeping the airspace within the designated ingress corridor and suppressing the enemy air defence, ”Col Tsokov explains. “During the training course at Martynowskaja, however, we were told that the aircraft tasked to deliver the nuclear bomb should operate in either a two- or four-ship formation on its way towards the designated target. When we asked our instructor, Lt Col Avenir Reshetnokov, why this change had been introduced, he replied that it was now (1980) much easier to organise delivery of the bomb because there were considerably more munitions available than during the previous decade.”

Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H
Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H

The MiG-23BN Flogger-H could deliver the RN-28 bomb using three principal flight pro- les – in horizontal flight, in a 20° dive or in a 15° climb. There were no specific altitude and speed restrictions for the drop and the only requirement was for the pilot to ensure separation of eight seconds between release and detonation in order to remove his aircraft to a safe distance. For a low-level drop the minimum altitude was usually set at between 200-600m (656-1,968ft) above ground level, but there was an option to drop the bomb from as low as 50m (164ft) in level flight.

According to Col Tsokov, there was almost no difference between conventional and nuclear bombs’ deployment methods. During training flights at Martynowskaja, the Bulgarian pilots practised dive bombing at different diving angles as well as drops while climbing and in level flight. They flew their own MiG-23UB Flogger-C two-seaters with a Soviet instructor in the rear seat, dropping P50-75 practice bombs which featured ballistic characteristics very similar to those of the RN-28. These characteristics were also virtually identical to those of the conventional bombs “Everything was the same and the only specific requirement when dropping the nuclear bomb was that the engine should be running at a constant setting until the nuclear shockwave was over,” Col Tsokov explained. When anticipating the detonation, the pilot was required to put his helmet light filter on and close his eyes. After returning home, the quartet of nuclear-capable pilots from the Bulgarian 25th Fighter Bomber Air Regiment continued to hone their bombing skills by dropping conventional bombs for the remainder of their flying careers.

Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H
Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H Bulgarian Air Force nuclear bomber MiG-23BN Flogger-H

“The MiG-23BN Flogger-H was a potent bomber and, in the case of war, we were con- dent in its penetration capability at ultra-low level and high subsonic speed, sneaking below radar coverage when flying just above the ground alongside the Maritsa riverbed towards the designated targets in Greece and Turkey,” said Col (Ret) Slavi Pavlov, another highly experienced Flogger-H pilot and a 25th Fighter Bomber Air Regiment commanding officer during the mid-1980s.

Source: Aviation News incorporating Classic Aircraft January 2014, Evgeni Andonov and Alexander Mladenov

Photos: Retrospotters and Christian Boisselon collection - every photo is from around 1990-1991

Bulgarian Air Force, VVS, Cold War, Warsaw Pact, 10th Composite Air Corps, Plovdiv, 25th Fighter Bomber Air Regiment, Cheshnegirovo, MiG-23BN Flogger-H, MiG-23UB Floger-C, MiG-17 Fresco-A, MiG-15UTI Midget, Soviet RN-28 nuclear bomb

Военновъздушни сили, ВВС, Военновъздушни сили на Република България, 10-и САК, 10-и Смесен авиационен корпус, Варшавски договор, Студена война, 25-ти изтребителн-бомбардировъчен авиополк, 25-и ИБАП, Чешнегирово, МиГ-23БН, МиГ-23УБ, МиГ-17, МиГ-15