Sukhoi Su-27P

The Su-27 was formally accepted into service by government decree on 23 August 1990, once the main shortcomings revealed in testing had been corrected; by then the aircraft had already spent five years, since 1985, flying with operational units. At that point two designations were fixed for the same single-seat fighter: in the Air Force (VVS) it became the Su-27S ("seriyniy", series-built), while in the aviation branch of the Air Defence Forces (PVO) it was called the Su-27P ("perekhvatchik", interceptor). The letter P therefore does not denote a later development but the same production aircraft with a somewhat simplified equipment fit, tailored exclusively to the interception mission. In practice many of these machines are referred to simply as Su-27, without the suffix.

Early-series Su-27Ps carried the RLPK-27 radar sighting system built around the N001 "Mech" pulse-Doppler radar (NATO "Slot Back"), complemented by the passive OEPS-27 electro-optical system: a gyro-stabilised 36-Sh infrared sensor, a laser rangefinder and a helmet-mounted sight that let the pilot designate a target by looking at it. For threat warning the first Su-27Ps used the L-006 "Beryoza" radar warning receiver, housed in the tail-boom extension between the engines. With this combination the interceptor could search and track with radar or, in electromagnetic silence, with the infrared channel, and guide R-27 medium-range and R-73 short-range missiles.

The two versions differ neither in aerodynamics nor in powerplant, which are identical, but in mission equipment. The Su-27P lacks the air-to-ground weapons control system and its associated wiring, so it could not be used as a strike aircraft against ground targets; its job was defending national territory against bombers, cruise missiles and reconnaissance aircraft. The Air Force's Su-27S retained that capability and, in late production batches, added active "Sorbtsiya-S" jamming pods on the wingtips and the SPO-15 warning receiver in place of the L-006.

A particular feature recorded in Russian sources is that on part of the Su-27P fleet, in compliance with international agreements, the circuits for entering the activation code of special munitions were blocked, so those aircraft ceased to be carriers of tactical nuclear weapons.

The Su-27P gave rise directly to the Su-27PU, a two-seater designed to support single-seat Su-27Ps, MiG-31s and other PVO interceptors with tactical data; that project was renamed Su-30 and eventually turned into a multirole fighter aimed at export, moving away from its original purpose. In the post-Soviet era the single-seat Su-27PD demonstrator, fitted with an in-flight refuelling probe, also appeared.

The successor states that inherited Su-27Ps have upgraded them on their own: Kazakhstan with the Su-27M2 and, through the Belarusian repair plant, the Su-27BM2; Ukraine with the Su-27P1M, put into service alongside the Su-27S1M and Su-27UB1M within a fleet modernisation programme.

According to US intelligence, the Soviet Air Defence Forces already had more than 100 Su-27s in 1988. The interceptor was unveiled to the West at the 1989 Paris Air Show, where test pilot Viktor Pugachev performed in front of the press the "Cobra" manoeuvre that became associated with the aircraft. With the dissolution of the USSR in 1991, the PVO regiments were divided among the new republics.

Ukraine inherited between 66 and 70 Su-27s of all versions; lack of funding and the type's demanding maintenance reduced the operational fleet to about 34 aircraft by 2019. Its Su-27Ps have been regulars at European air shows: one flew to the Royal International Air Tattoo in 2018 and another appeared that same year at the Belgian base of Kleine Brogel. Belarus took over the aircraft of the former 61st Fighter Aviation Regiment, between 23 and 28 airframes; it sold nine to Angola in 1998 and kept 17 Su-27Ps and 4 Su-27UBM1s until retiring them in December 2012. Kazakhstan received 26 Su-27s from Russia between 1996 and 2001 and still flies Su-27Ps from the bases at Taldykorgan and Aktau, alongside upgraded Su-27BM2s and Su-27UBM2s. Ethiopia bought second-hand from Russia up to 17 Su-27S, Su-27P and Su-27UB in two batches, nine from 1998 and eight from 2002, based at Debre Zeit.

In Russia the Su-27P stayed with the air-defence aviation and with display units: the "Russian Knights" aerobatic team has flown this version. An episode that illustrates its mission took place on 15 January 1998, when a pair made up of Su-27UB No. 61 and Su-27P No. 10, the latter flown by A. Oleynik, forced an Estonian-registered L-29 jet (ES-YLE) crewed by two British military pilots to land at Khrabrovo airfield, in an interception carried out at minimum speeds.

Besides the examples still flying in Ukraine, Kazakhstan and Russia, one Su-27P (serial number 36911034512) is preserved on display at the Victory Park in Hlybokaye, Belarus.