The Mk 4 and Mk 40 FFARs are conventional 70 mm (2.75 in) diameter unguided rockets comprising a solid-propellant motor with four folding fins and an appropriate exhaust nozzle and warhead. The standard helicopter-launched Mk 40 rocket motor is 1.01 m long, weighs 5 kg and, because of its scarfed exhaust nozzle, has an induced spin rate of 20 rev/s. It is filled with an extruded N5 double-base propellant charge that has a burn time of 1.55 seconds and gives the rocket a total impulse of 514 daN. The Mk 4 rocket motor, which is designed for fixed-wing aircraft applications, is identical in all respects to the Mk 40, except the exhaust nozzle is not scarfed and, as a result, the rocket has no spin rate. Both variants, when fitted with an M151 HE warhead and M433 nose fuze, are 1.42 m long, have a body diameter of 70 mm and weigh around 10 kg. Warheads associated with the Mk 4 and Mk 40 rockets are: the Mk 1, a 2.63 kg blast/fragmentation; Mk 5, 2.63 kg anti-tank; Mk 61, 2.95 kg target practice; Mk 64, 3.91 kg blast/fragmentation; Mk 67, 2.04 kg smoke containing white phosphorus; M151, 4.68 kg HE which is 0.41 m long, filled with 1.04 kg of Composition B-4 explosive and is used for anti-personnel and anti-material targets; M229, 7.62 kg HE that is 0.68 m long; M247, anti-tank shaped charge; and the WDU-4A/A a flechette warhead. In addition to the above, the Mk 4