Military helicopters play an integral part in the sea, land and air operations of modern military forces. Generally manufacturers will develop airframes in different weight/size classes which can be adapted to different roles through the installation of mission specific equipment. To minimise development costs the basic airframes can be stretched and shortened, be updated with new engines and electronics and have the entire mechanical and flight systems mated to new fuselages to create new aircraft. For example, the
Bell UH-1 Iroquois (known as the "Huey") has given rise to a number of derivatives through stretching and re-engining, including the
Bell AH-1. Modern helicopters have introduced modular systems which allow the same airframe to be configured for different roles, for example the
Augusta Westland AW101 "Merlin" in
Royal Navy service can be rapidly configured for ASW or transport missions in hours. To at the same time retain flexibility and limit costs, it is possible to fit an airframe
for but not with a system, for example in the US Army's
Boeing AH-64D Apache variants are all fitted to be able to take the Longbow radar system, but not enough sets have been bought to equip the whole force. The systems can be fitted to only those airframes that need it, or when finances allow the purchase of enough units.
Equipment Most military helicopters are
armoured to some extent; however, all equipment is limited to the installed power and lift capability and the limits installed equipment places on useful payload. The most extensive armour is placed around the pilots, engines, transmission, and fuel tanks. Fuel lines, control cables and power to the tail rotor may also be shrouded by Kevlar armour. The most heavily armoured helicopters are attack, assault and special forces helicopters. In transport helicopters the crew compartment may or may not be fully armoured, a compromise being to give the passengers Kevlar lined seats but to leave the compartment for the most part unarmoured.
Survivability is enhanced by
redundancy and the placement of components to protect each other. For example, the
Blackhawk family of helicopters uses two engines and can continue to fly on only one (under certain conditions), the engines are separated by the transmission and placed so that if attacked from any one flank, the engine on that flank acts to protect the transmission and the engine on the other side from damage. Aviation electronics, or
avionics, such as communication radios and navigation aids are common on most military helicopters. Specialized avionics, such as
electronic countermeasures and
identification friend or foe systems, are military specific systems that can also be installed on military helicopters. Other payload or mission systems are installed either permanently or temporarily, based on specific mission requirements; optical and IR cameras for scout helicopters, dunking sonar and search radar for anti-submarine helicopters, extra radio transceivers and computers for helicopters used as airborne
command posts. Armour, fire suppression, dynamic and electronics systems enhancements are invisible to casual inspection; as a cost-cutting measure some nations and services have been tempted to use what are essentially commercial helicopters for military purposes. For example, it has been reported that China is carrying out a rapid enlargement of its assault helicopter regiments with the civilian version of the Russian
Mil Mi-17. These helicopters without armour and electronic counter measures will function well enough for training exercises and photo opportunities but would be suicidal to deploy in the assault role in actual combat situations. The intention of China appears to be to
retrofit these helicopters with locally produced electronics and armour when possible, freeing available funds to allow rapid creation of enough regiments to equip each of its
Group Armies, allowing a widespread buildup of experience in helicopter operations.
Attack of the
People's Liberation Army Ground Aviation Attack helicopters are helicopters used in the
anti-tank and
close air support roles. The first of the modern attack helicopters was the Vietnam era
Bell AH-1 Cobra, which pioneered the now classic format of pilot and weapons officer seated in
tandem in a narrow fuselage, chin mounted guns, and
rockets and
missiles mounted on stub wings. To enable them to find and identify their targets, some modern attack helicopters are equipped with very capable sensors such as a
millimeter wave radar system.
Transport operated by the
Russian Air Force Transport helicopters are used for transporting personnel (troops) and cargo in support of military operations. In larger militaries, these helicopters are often purpose-built for military operations, but commercially available aircraft are also used. The benefit of using helicopters for these operations is that personnel and cargo can be moved to and from locations without requiring a runway for takeoffs and landings. Cargo is carried either internally, or externally by slung load where the load is suspended from an attachment point underneath the aircraft. Personnel are primarily loaded and unloaded while the helicopter is on the ground. However, when the terrain restricts even helicopters from landing, personnel may also be picked up and dropped off using specialized devices, such as rescue hoists or special rope lines, while the aircraft hovers overhead.
Air assault is a military strategy that relies heavily on the use of transport helicopters. An air assault involves a customized assault force that is assembled on the pick-up zone and staged for sequential transport to a
landing zone (LZ). The idea is to use the helicopters to transport and land a large number of troops and equipment in a relatively short amount of time, in order to assault and overwhelm an objective near the LZ. The advantage of air assault over an airborne assault is the ability of the helicopters to continually resupply the force during the operation, as well as to transport the personnel and equipment to their previous location, or a follow-on location if the mission dictates.
Observation operated by the
French Army Light Aviation The first
reconnaissance and
observation aircraft were balloons, followed by light airplanes, such as the
Taylorcraft L-2 and
Fieseler Fi 156. As the first military helicopters became available, their ability to both maneuver and to remain in one location made them ideal for reconnaissance. Initially observation helicopters were limited to visual observation by the aircrew, and most helicopters featured rounded, well-glazed cockpits for maximum visibility. Over time, the human eye became supplemented by optical sensor systems. Today, these include
low light level television and
forward looking infrared cameras. Often, these are mounted in a stabilised mount along with multi-function
lasers capable of acting as
laser rangefinder and
targeting designators for weapons systems. By nature of the mission, the observation helicopter's primary weapons are its sensor suite and communications equipment. Early observation helicopters were effective at calling for artillery fire and
airstrikes. With modern sensor suites, they are also able to provide terminal guidance to anti-tank guided weapons, laser-guided bombs and other missiles and munitions fired by other armed aircraft. Observation helicopters may also be armed with combinations of gun and rocket pods and sometimes
anti-tank guided missiles or
air-to-air missiles, but in smaller quantities than larger attack helicopters. Primarily, these weapons were intended for the counter-reconnaissance fight—to eliminate an enemy's reconnaissance assets—but they can also be used to provide limited direct fire support or close air support.
Maritime (left) and
UH-1Y Venom (right) operated by the
United States Marine Corps Among the first practical uses of helicopters when the
Sikorsky R-4 and
R-5 became available to British and American forces was deployment from navy cruisers and battleships, at first supplementing and later replacing
catapult-launched observation aircraft. Another niche within the capability of the early helicopters was as
plane guard - tasked with the recovery of pilots who had
ditched near an
aircraft carrier. As helicopter technology matured with increased payload and
endurance, anti-submarine warfare (ASW) was added to the helicopter's repertoire. Initially, helicopters operated as weapons delivery systems, attacking with
air-launched torpedoes and
depth charges based on information provided by its parent and other warships. In the 1960s, the development of the
turboshaft engine and
transistor technology changed the face of maritime helicopter aviation. The turboshaft engine allowed smaller helicopters, such as the
Westland Wasp, to operate from smaller vessels than their
reciprocating engine predecessors. The introduction of transistors allowed helicopters, such as the
Sikorsky SH-3 Sea King, to be equipped with integral dunking
sonar,
radar and
magnetic anomaly detection equipment. The result was an aircraft able to more quickly respond to submarine threats to the fleet without waiting for directions from fleet vessels. Today, maritime helicopters such as the
Sikorksy SH-60 Seahawk and the
Westland Lynx are designed to be operated from
frigates,
destroyers and similar size vessels. The desire to carry and operate two helicopters from frigate- and destroyer-sized vessels has affected the maximum size of the helicopters and the minimum size of the ships. Increasing
miniaturisation of electronics, better engines and modern weapons now allow even the modern, destroyer-based, multi-role helicopter to operate nearly autonomously in the ASW, anti-shipping, transport,
SAR and
reconnaissance roles. Medium- and large-sized helicopters are operated from carriers and land bases. In the British, Spanish, and Italian navies, the larger helicopters form the main anti-submarine strength of carrier air wings. When operating from shore bases, the helicopters are used as anti-submarine pickets to protect against hostile submarines loitering outside military ports and harbours; their endurance and payload providing advantages over smaller helicopters. Soviet maritime helicopters, operating from its cruisers, had the additional role of guidance of the cruisers' long range anti-shipping missiles. Maritime helicopters are
navalised aircraft for operation from ships. This includes enhanced protection against
salt water corrosion, protection against ingestion of water, and provision for forced ditching at sea.
Multi-mission and rescue and a
military dog being lifted into a rescue-equipped UH-60 Black Hawk As helicopters came into military service, they were quickly pressed into service for
search and rescue and
medical evacuation. During World War II,
Flettner Fl 282s were used in Germany for
reconnaissance, and
Sikorsky R-4s were used by the United States to rescue downed aircrews and injured personnel in remote areas of the
China Burma India Theater, from April 1944 until the war's end. The use of helicopters for rescue during combat increased during the
Korean War and the
Algerian War. In the
Vietnam War the
USAF acquired
Sikorsky S-61R (Jolly Green Giant) and
Sikorsky CH-53 Sea Stallion (Super Jolly Green Giant) helicopters for the
Combat search and rescue (CSAR) mission.
Training Some services use a version of their operational helicopters, usually in the light class, for pilot training. For example, the British have used the
Aérospatiale Gazelle both in operations and as a trainer. Some services also have an
ab initio phase in training that uses very basic helicopters. The
Mexican Navy has acquired a number of the commercially available
Robinson R22 and
R44 helicopters for this purpose.
Utility A utility helicopter is a multi-purpose
helicopter. A utility military helicopter can fill roles such as
ground attack,
air assault,
military logistics,
medical evacuation,
command and control, and
troop transport. ==Tactics and operations==