Strana 11
Overall view of the NR-30 aircraft
cannon equipped with a muzzle
break as would be found on,
for example, the MiG-19S.
A cutaway of the NR-30
from the right.
Principle behind Cannon Operation
during Pneumatic Tensioning
By channeling compressed air from the pres-
sure cylinder to the cocking cylinder of the
weapon, the barrel with the breech block and
the locked breech is pulled backwards. In the
initial phase of the movement, the recoil accel-
erator is activated, which unlocks the chamber
and moves the breech block to the rear posi-
tion, where it is caught by a trigger. The barrel
with the breech block is pulled further back-
wards to the rearmost position (100 mm). After
releasing the cocking button, the compressed
air returns the barrel with the breech block to
the front position. The movement of the bar-
rel backwards and forwards is simultaneously
transmitted by gears to the ammunition feed-
er, which advances the cartridge belt by one
round and inserts the cartridge into the breech
block. This makes the weapon ready for firing.
This is indicated in the cockpit by the lighting of
a red indicator light after the electrical installa-
tion contacts in the trigger are engaged.
Principle behind Cannon Function
during Firing
After applying electric current to the trigger of
the weapon, the bolt is released, which, under the
pressure of the tensioned spring inserts the round
into the cartridge chamber and locks it. After lock-
ing, the round is mechanically fired. The resulting
exhaust gases exert pressure on the bottom of the
round and the bottom of the cartridge case. The
round begins to move forward and the barrel with
the breech block backward. The effect of the re-
coil accelerator kicks in, the cartridge chamber is
unlocked and the breech with the empty cartridge
is moved backward, where it is captured by the
electromagnetic trigger. At the moment when the
round passes the vent holes in the barrel, some of
the exhaust gases are released into the gas cyl-
inder. As a result of the movement of the barrel,
the gas cylinder space is closed and the resulting
gases are compressed by a floating piston, which
is moved by the barrel nut. Compressing the gas-
es dampens the effects of recoil arising during
the firing sequence. When the barrel reaches its
rear position, it returns to the front position under
the pressure of the gases in the gas cylinder. In
the front position, the gases from the gas cylin-
der escape to the outside. The movement of the
barrel is simultaneously transferred to the feeder,
which moves the cartridge belt by one round and
inserts another cartridge into the breech head.
This pushes out the spent cartridge and ejects it
outside the aircraft, while the ammunition belt
links are channeled to a box for collecting them
inside the aircraft. After returning the barrel to the
front position, if the breech is in the rear position
and electric current is still supplied to the trigger,
the automatic operation of the firing sequence is
repeated and the cannon fires another round.
NR-30 30x155B Ammunition Types
The development and the evolution of the NR-
30 system was not limited to the weapon itself.
The ammunition evolved as well. As noted earlier,
the 30 designator refers to the caliber of ammu-
nition used in millimeters, while 155 specifies
the length of the cartridge, also in millimeters.
During the development of the weapon, a range
of ammunition types was also introduced:
OFZ (NATO Equivalent HEI) – high-explosive – in-
cendiary with a head fuse,
BR (APHE) – armor-piercing – high-explosive
with a bottom fuse,
PRL – anti-radar chaff,
LP (TP) – inert, for verifying the function of the
weapon,
FZ – high-explosive – incendiary (anti-balloon).
Later, the following types of rounds were devel-
oped and modified:
OFZ – modernized,
ME – multi-element.
This does not complete the list of available
rounds used in the NR-30. Those listed above are
base types, used by the Czechoslovak and later,
the Czech Republic Air Forces.
Main types of 30x155B ammunition. From the left,
modernized, HEI, APHE and TP (early and later
types).
Fifteen rounds of APHE in the ammunition belt
prior to loading into an aircraft.
HISTORY
INFO Eduard
11
January 2025