Airburst fuzes usually have a combined airburst and impact function. Bell developed two complete fuzing systems, airburst or surface burst. The weapon had both an airburst and contact fuzing modes. It has a multi-mode airburst, point detonation, and delay fuse. The round is engineered with three firing modes&colon; airburst; point detonation; and self-destruct. However, airburst fuzes have to have the required fuze length set. British time fuzes, required for airburst shooting, were powder burning (igniferous). Both base and nose ejection are almost always used with airburst fuzes. The fireball exploded in an airburst above Earth's surface. Airburst fuzes have to have the fuze length (running time) set on them. Airburst munitions for Russian 30mm and 57mm autocannons are in development. Airburst munitions significantly increase the relative risk for lying men, etc. It is capable of engaging helicopters with a timed airburst. Airburst fuses were either igniferious (based on a burning fuse) or mechanical (clockwork).