In February 1944, the MiG OKB initiated the design of a
mixed-power single-seat fighter with the Izdeliye designation
N. Conceived to use the so-called "accelerator",
or VRDK (Vozdushno-reaktivny dvigatyel kompressorny,
or Air-reaction engine compressor), which
had been developed at the TsIAM under the leadership
of K V Kholshchevnikov, the N preliminary design was
finished on 28 March 1944. Drawings were completed by 30 November 1944, by which time the official designation
I-250 had been applied to the project, and
three months later, on 26 February 1945, the first of two
prototypes, the N-1, left the factory. Primary power was
provided by a Klimov M-107A (VK-107A) 12-cylinder
Vee-type engine rated at 1650hp for take-off and armament
consisted of three 20mm G-20 cannon, one between
the engine cylinder banks and the others flanking
the engine.
The first flight took place on 3 March
1945, and the VRDK was fired for the first time during
the third test flight. The VRDK consisted of an engine-driven
compressor which fed compressed air via a
water radiator to a mixing chamber in which fuel was
introduced under pressure, the mixture being ignited
in a double-walled combustion chamber and then
ejected through a variable orifice. This provided 300kg of thrust for up to 10 minutes, boosting speed
by 100km/h. N-1 crashed during mid-May
when the permissible load factor was exceeded and the
horizontal tail collapsed at low altitude, but a second
prototype, the N-2, was rolled out on 26 May 1945. This
lacked armament and the vertical tail was enlarged to
rectify some longitudinal instability, but this prototype,
too, was destroyed in an accident. In July 1945, the OKB
received instructions to supervise the construction of
10 I-250 aircraft to participate in the Air Parade that was
planned for 7 November 1945, barely four months later.
Nine I-250s were ready on time, but inclement weather
resulted in cancellation of the Parade. These aircraft,
together with a further seven, were subsequently delivered
to the Navy as MiG-13s, equipping an evaluation
unit based at Skultye airfield, near Riga. Several
of the pre-series MiG-13s were experimentally fitted
with sabre-shaped propeller blades, and official NII
VVS trials were conducted between 9 October 1947 and
8 April 1948. Production of the I-250 alias MiG-13 had
totalled 16 pre-series aircraft, and although the fighter
was essentially successful, it had been overtaken by
pure jet fighters and surviving examples were retired
by the Navy in May 1948. The following performance
data relate to the N-1, weights and dimensions being
applicable to the MiG-13.
