ALARM encyclopedia topics

burglar alarms, designed to warn of burglaries; this is often a silent alarm: the police or guards are warned without indication to the burglar, which increases the chances of catching him or her.
alarm clocks can produce an alarm at a given time
Distributed control manufacturing systems or DCSs, found in nuclear power plants, refineries and chemical facilities also generate alarms to direct the operator's attention to an important event that he or she needs to address.
Alarms in an Operation and Maintenance (O&M) Monitoring system, which informs the bad working state of (a particular part of the) system under monitoring.
safety alarms, which go off if a dangerous condition occurs. Common public safety alarms include:

tornado sirens
fire alarms

"Multiple-alarm fire", a locally-specific measure of the severity of a fire and the fire-department reaction required.

car alarms
Community Alarm or Autodialer alarm (medical alarms)
air raid sirens
Personal alarm
tocsins — a historical method of raising an alarm

Alarms have the capability of causing a fight-or-flight response in humans; a person under this mindset will panic and either flee the perceived danger or attempt to eliminate it, often ignoring rational thought in either case. We can characterise a person in such a state as "alarmed".

With any kind of alarm, the need exists to balance between on the one hand the danger of false alarms (called "false positives") — the signal going off in the absence of a problem — and on the other hand failing to signal an actual problem (called a "false negative"). False alarms can waste resources expensively and can even be dangerous. For example, false alarms of a fire can waste firefighter manpower, making them unavailable for a real fire, and risk injury to firefighters and others as the fire engines race to the alleged fire's location. In addition, false alarms may acclimatise people to ignore alarm signals, and thus possibly to ignore an actual emergency: Aesop's fable of The Boy Who Cried Wolf exemplifies this problem.

Etymology

"Alarm" came from Old French 'à l'arme' = "to the weapon", telling armed men to pick up their weapons and get ready for action (because an enemy may have suddenly appeared).

History

The Ministry of Defence received bids for a new anti-radiation missile in late 1982; British Aerospace Dynamics offered ALARM while Texas Instruments teamed with Lucas Aerospace offered its HARM missile. Defence Secretary Michael Heseltine announced the selection of ALARM on 29 July 1983. The initial order was 750 missiles for the RAF. The selection process was controversial; the battle between the contractors was bitter, the Ministry of Defence favoured ALARM to retain UK industrial capabilities while the Treasury favoured the cheaper and proven HARM.

In early 1986 BAe recognised that Royal Ordnance was having difficulties delivering the missile's motor, named Nuthatch, and began to consider alternatives. Royal Ordnance's solution to the required burn-loiter-burn characteristic of the engine was complex. In July 1987 BAe, by then the owner of Royal Ordnance, replaced the Nuthatch motor with a lower risk motor designed by Bayern-Chemie. BAe's GB£200 million contract for the missile was renegotiated with the price increased to GB£400 million and delivery pushed back from 1988 to 1990.

Features

ALARM is a fire-and-forget system, with an added loiter capability. In loiter mode, ALARM will, when launched, climb to an altitude of 13 km. If the target radar shuts down, the missile will deploy a parachute and descend slowly until the radar lights up. The missile will then fire a secondary motor to attack the target.

Combat Performance

ALARM has been used in the following conflicts:

1991 Gulf War, during which 121 missiles were used.
Kosovo War
2003 Invasion of Iraq

During the 1999 'Allied Force' offensive in Kosovo, Luftwaffe Tornado ECR, USAF Wild Weasel F-16s and US Navy EA-6B Prowlers attempted to destroy a Serbian air defence radar with HARMs. After almost 100 attempts, the RAF was called in and the radar was destroyed with a single ALARM, thanks to its loiter capability.

Operators

Specifications

Primary Function: Suppression of Enemy Air Defence
Contractor: MBDA
Power Plant: Bayern Chemie two stage solid propellant rocket motors
Length: 4.24 m
Diameter: 23 cm
Wing Span: 73 cm
Launch Weight: 268 kg
Speed: 2455 km/h (supersonic)
Warhead: Proximity fused high-explosive
Range: 93km
Fuse: Laser Proximity
Guidance system: Pre-programmed/passive radar seeker
Unit Cost: undisclosed
Date Deployed: 1990
User: UK (RAF)

Tornado GR.4, although only IX Squadron and 31 Squadron specialise in the role.
Tornado F3 - fitted in time for 2003 Gulf War - receiving designation Tornado EF3
Weapon has been "fit checked" on other RAF aircraft, such as the Jaguar. Due to its relatively large weight it is not suited to the entire RAF fleet.
Also expected to be usable on the Eurofighter Typhoon

References

External links

RAF: ALARM description
Bayern-Chemie - Development and production of a rocket motor used by ALARM. More than 1,200 produced
Matra-BAe Dynamics ALARM at Eurofighter Typhoon—a brief history of ALARM
RAF Weapons at armedforces.co.uk