Grumman EA-6B Prowler
For many years the US Marine Corps operated a number of EF-10B Skyknights as EW platforms, particularly in Vietnam, but as these aircraft aged it became essential that an effective replacement was developed and a version of the A-6A Intruder attack aircraft was soon identified as the most cost-effective option. A total of 28 A2F-1Q aircraft were built or converted from A-6A airframes and these aircraft were split into three squadrons and were used to support strike aircraft by jamming enemy radar systems, whilst at the same time gathering intelligence on North Vietnamese electronic systems - the aircraft were soon re-designated the EA-6A. The two-seat EA-6A was quite similar in appearance to the A-6A, but carried signals surveillance and recording systems, various EW jammers and a number of EW antennas housed in a bulbous fairing on top of the tail. Nevertheless, the EA-6A was always a 'stop-gap' design and, despite the aircraft operating successfully, a number of significant problems were identified, particularly the need for the aircraft to carry additional EW operators and jammers. The EA-6As continued to operate until the late 1970's and began to be withdrawn when the EA-6B was introduced, although some aircraft were used as electronic aggressor training aircraft until the early 1990's.
With the experience gained in combat operations over North Vietnam, plans were soon being drawn up for a larger, more effective version of the aircraft - this became the EA-6B Prowler. To accommodate two additional crew members, the A-6 fuselage was extended by 54 inches and the pod on the tail was enlarged. The four crew are accommodated in a side-by-side twin cockpit layout which has improved crew efficiency on long missions. The EA-6B is more than 10,000lbs heavier than the A-6E Intruder and although the wing areas are the same, the additional weight does adversely affect the maneuvering capability of the larger aircraft. Rather underpowered for its weight, the Prowler is powered by two Pratt and Whitney J52-P408A turbojets which each produced 19,400 lbs of thrust, this gives the aircraft a cruising speed of around 500kts, a maximum ceiling of 40,000ft and an unrefueled range of of over 1,000nms. The EA-6B first flew on 25 May 68 and entered operational service in July 1971.
The Prowler's crew consists of a pilot and three Electronic Counter-measures Officers (ECMOs). The senior officer among the four crew is normally the mission commander. The ECMO1, who sits to the right of the pilot, is responsible, along with the pilot, for operating the navigation and communication systems, the air-to-ground radar, the defensive electronic countermeasures systems and firing the HARM. In the rear cockpit ECMO-2 and ECMO-3 are responsible for operating the ALQ-99 Tactical Jamming System (TJS) and the ALQ-99 OBS which gathers tactical electronic order of battle data which can be relayed back to tactical headquarters whilst airborne and stored for later detailed analysis on the ground.
The AN/ALQ-99 Tactical Jamming System is the heart of EA-6B and this consists of of up to five externally mounted pods and equipment in the fairing above the tail. However, the EA-6B normally operates with three external pods, two under each wing and one under the centre fuselage, leave two wing stations free for either fuel tanks or HARM missiles. The pods generate their own electrical power using a Ram Air Turbine (a small electrical generator powered by a small propeller on the nose) and each pod contains two continuous wave jamming transmitters, covering one of seven frequency bands, use beam steering to direct the jamming signal at the threat and an exciter to adjust the jamming signal. Each pod also contains a computer linked to the ALQ-99 Central Processing Unit (CPU) which processes the various threat signals, manages jamming operations and displays the data to the crew. The fairing on top of the tail contains a variety of surveillance receivers that are capable of detecting hostile radar transmissions at considerable range and long before that radar is capable of detecting the aircraft. Detection, identification, direction-finding and jammer-set-on-sequence may be performed automatically or by the crew.
For a number of years the Prowler was used just as a very effective EW aircraft, but it was eventually realised that it made sense to also give the aircraft an even greater offensive capability. Since 1986 Prowlers have been capable of carrying the Texas Instruments AGM-88 High Speed Anti-Radiation Missile (HARM) on any of the underwing pylons. With a range of over 80 miles and a very effective blast-fragmentation warhead, the missile can be fired on any hostile radar transmitter and has a high rate of success and quickly encourages the enemy to shut down surveillance and missile guidance radars.
To ensure the aircraft remained effective throughout their long service, the EA-6B fleet has been progressively upgraded throughout it's career under three programmes know as Increased Capability (ICAP) 1-3. Currently, the EA-6B fleet is a mix of aircraft in either ICAP II or III configuration The ICAP III programme began in Nov 00 with the upgraded aircraft first flying in Nov 01. The $200 million ICAP III programme will allow selection and switching between jamming frequencies accoring to the threat, rather than diluting the effectiveness of the system by pre-emptively targeting a broad spectum. The new system now locks onto a frequency and can mimic frequency hopping patterns. New crew displays, Link 16 datalink, additional processors and a new tactical display interface complete the upgrade. Initial operational capability of the revised aircraft is expected during 2005.
The premature withdrawal of the EF-111A Raven in 1998 left the EA-6B as the only dedicated EW aircraft in service and since then the aircraft has become another 'high demand - low density' platform, high on the 'wish-list' of every commander in an operational theatre. Production of the EA-6B ended in 1991 and, of the 170 built, around 123 Prowlers are still in service, with around 105 'active' aircraft divided between eight squadrons - four mixed USAF/USN squadrons and four USMC squadrons, that operate either as part of a Carrier Air Group or from shore-based airfields. Although plans are already underway to replace the Prowler with the Boeing EA-18G Growler, many doubt whether this smaller aircraft will ever the capability of the EA-6B Prowler and, with a crew of two it will certainly more automated systems. Nevertheless, with the EA-18G Growler is still some way away from squadron service, it will still be many years before the distinctive shape of the EA-6B Prowler disappears from active service.