During the Vietnam War (1954-1975), the U.S. Air Force (USAF) lacked a purpose-built Close Air Support (CAS) aircraft. Several aircraft were used to conduct ground attack and CAS sorties, but none of these specialised in those duties. At the end of the Vietnam War, it seemed very likely that the Soviets would invade Europe, so the USAF had to analyse its arsenal. The Cessna A-37 Dragonfly was used in combat as a CAS aircraft, but it was essentially a beefed up training aircraft. A-1 Skyraiders were very tough and rugged, but were obsolete and would be ineffective if used as modern weapons platforms. Ultimately, A-7 Corsair IIs became the best CAS aircraft, but even these were not specifically designed to destroy tanks. Naturally, destroying tanks, or ‘tank busting’, would be a CAS aircraft’s primary duty if a Soviet invasion had to be countered. The only solution to the USAF’s lack of a dedicated ‘tank killer’ CAS aircraft, was to design one specifically for that purpose.
The Fairchild A-10 Thunderbolt II made its maiden flight in May 1972 and the USAF announced full scale development less than a year later. It was named after the Republic P-47 Thunderbolt, which was the heaviest single-seat piston-engined fighter ever produced. During World War II, P-47s were formidable ground attack aircraft, which could absorb massive amounts of battle damage and excelled at destroying tanks and trains. Would the Thunderbolt II be a reincarnation of the legendary P-47?
Let’s not beat around bush. The A-10’s most dominant feature is its primary weapon: the GAU-8/A Avenger cannon. It is a 30 mm, seven-barrel Gatling-gun, which fires up to 4 200 rounds per minute – that’s 70 rounds per second! A single hit by one armour-piercing incendiary (API) round, weighing 750 g, could be devastating to a tank. Bear in mind it would take that round less than three seconds to reach a tank over a distance of three kilometres. Recently, the firing rate on A-10s has been set to a fixed rate of 3 900 rounds per minute with the capacity of 1 174 rounds in its ammunition drum. It is the largest, heaviest and most powerful aircraft gun in the US arsenal.
The A-10 is probably better known as the ‘Warthog’, due to its rather ungainly appearance, but there is a reason for its unique shape. Survivability, an essential attribute of any successful ground attack aircraft, is where the A-10 excels. The engines, for example, are located high on the rear fuselage, where the aircraft’s wings, fuselage and tail shield them against attacks from most angles. The engines are also a safe distance from the ground, when A-10s operate from rough airfields, damaged runways or roads. Flight controls operate with dual hydraulic systems and, should both systems fail, there is a mechanical ‘manual reversion flight control system’ as backup. 1 315 kg of armour ensures that A-10s are immune to small arms fire, which is useful if one considers that Warthogs often operate between 50 and 500 ft above ground level. The cockpit is situated inside a titanium armour ‘bathtub’, capable of withstanding a direct hit from a 23 mm round at close range. In theory, an A-10 could still be flown back to its base, having one engine, one vertical stabiliser and a large part of a wing destroyed. As is necessary with CAS aircraft, Warthogs can operate from bases with limited facilities, near the actual combat area. Some of the A-10’s components, such as the main landing gear and vertical stabilisers, can be fitted to either the left or right side of the aircraft. Modern A-10 pilots have the advantage of Night Vision Imaging Systems (NVIS), enabling them to operate effectively at night.
In short, the A-10 Thunderbolt II exceeds the basic requirements of an effective CAS aircraft: accurate weapons delivery, survivability and the ability to loiter around the target area for a prolonged time. However, can the same be said about its Russian counterpart?
Soviet strategists watched with great interest as the competition for a new USAF CAS aircraft culminated in the A-10. After all, the Soviets essentially pioneered the dedicated CAS concept with their World War II Sturmoviks, but now they had to catch up. Sukhoi Design Bureau’s T-8 prototype was selected as the Soviet answer to the A-10, after making its maiden flight in February 1975. It looked remarkably similar to the Northrop A-9 prototype, which was rejected by the USAF in favour of the A-10. The production version of the T-8 was called the Sukhoi Su-25 ‘Grach’, meaning ‘rook’, but it was known to the West by its NATO code name ‘Frogfoot’.
There are some similarities between the Su-25 and the A-10. For example, the Su-25 also utilises a dual redundant hydraulic control system and its cockpit is also placed in a ‘tub’ of titanium armour. Both aircraft are very suitable for unprepared, rough airfields close to the combat area. However, if an A-10 could be compared with a modern BMW X5, the Su-25 would be a classic Land Rover with a tyre on its bonnet and a spade tied to one of its doors. In typical Soviet fashion, there are several practical solutions to common problems. The nose wheel has a mudguard to prevent it from shooting up bits of debris into the engine intakes. Maintenance and servicing equipment can be stored in underwing containers, whilst the landing gear has heavy duty shock absorbers and low pressure tyres. Another important feature is that the Su-25’s engines can run on any fuel available in the combat area, including diesel, petrol and Avgas.
At one stage the Soviets experimented with underwing pods, designed to transport ground crew members, but this idea was later abandoned. An armour plate behind the ejection seat prevents any rearward vision, so a periscope rear view mirror was installed on top of the canopy. After initial combat experience in Afghanistan, it became evident that the Grach’s engines were too close too each other, so damage to one engine would lead to both engines being destroyed. The Americans avoided this problem by separating the engines on the A-10. The Soviets responded by installing an armour plate between the engines and under the fuel tanks. As with the A-10, later Su-25s had foam-filled fuel tanks to prevent explosions.
Later on, a two-seater version of the Su-25 was built as an operational weapons trainer, whilst a naval variant with an arrestor hook was produced for carrier operations. More recently, aerospace companies from Israel and Georgia collaborated to produce the Su-25 K ‘Scorpion’. This variant features a glass cockpit, HUD (Head Up Display) and more advanced navigation and weapons delivery systems. Ironically, these aircraft are now in line with NATO weapons and communication standards. Meanwhile, Sukhoi has developed more advanced Su-25 Ts and TMs, which are dedicated ‘tank killers’, also known as Su-39s.
Su-25s in combat
In 1980, the Soviets hastily sent some of their early production Su-25s to Afghanistan for combat evaluation in the Soviet-Afghan War (1979-1989). A number of Su-25s were lost to American supplied Stinger missiles, but that was before the introduction of armour plates between the engines and fuel tanks. Nevertheless, only 23 Su-25s were lost in combat during this war, which has often been referred to as the Soviets’ Vietnam War. This loss rate was considerably lower than the loss rates of MiGs that participated in the same theatre. One Su-25 was lost for every 2 800 flying hours. Grach pilots would mostly use rockets and external cannons to attack ground targets, with guided missiles only becoming a factor later in the war. Mujahedin rebels would usually wait until the aircraft had passed overhead, before leaving their cover to fire their Stinger missiles. Su-25 crews countered this tactic by fitting backward firing cannon pods. They would then fire these cannons as they pulled up and away from the targets, essentially providing their own ‘cover fire’. There are several reports of Su-25s safely limping home, having sustained severe battle damage, such as a direct hit from a Stinger missile.
These CAS Sukhois saw combat in several conflict areas, such as Chechnya, Abkhazia, Macedonia, India, Ivory Coast and Ethiopia. Iraq, under control of Saddam Hussein, used Su-25s extensively during the Iran-Iraq War. Angola is the closest country to South Africa that is currently operating Su-25s.
A-10s in combat
As mentioned, the A-10 was originally designed to counter a Soviet invasion of Europe. However, they first saw action in 1990, when the Gulf War erupted. Warthogs flew well over 8 000 sorties and fired more than a million cannon rounds. Also, 90% of the Maverick air-to-ground missiles used during the conflict were launched from A-10s. These ‘tank busters’ destroyed more than 4 200 targets, including two enemy helicopters, whilst only six A-10s were shot down. Warthogs saw more action in Afghanistan, Kosovo and again in Iraq, during the 2003 invasion.
Let us take a quick look at the basic characteristics of these ‘tank busters’. The Su-25 is quite a bit smaller than the A-10, but has a top speed of 527 kts – that is over 140 kts faster than the A-10. The Warthog’s square wings span three metres wider than those of the Grach and are ideal for manoeuvring at very low altitudes. Both aircraft can carry an array of bombs, rockets, missiles, pods and fuel tanks under their wings, but the A-10 can take off with almost 3 000 kg more weapons than its Russian equivalent. The 30 mm cannon on the Grach is considerably less impressive than the Avenger on the A-10, but it still packs a punch that would intimidate most tank crews.
As far as survivability goes, the A-10 is definitely a more solid aircraft. The Su-25 is a very tough aircraft, but the Warthog is in a class of its own when one looks at redundant systems and components. The distance between the A-10’s two engines, as well as their position on the plane, is a revolutionary concept. On the other hand, Su-25s are smaller and faster, making them more difficult targets. Also, A-10s do not accelerate as quickly as the Sukhois. This is a definite disadvantage in mountainous areas, but one cannot ignore the A-10’s Avenger cannon. It is simply magnificent. It may not be politically correct to use ‘magnificent’ to describe a device that kills people, but it is without doubt ‘the mother of all guns’. Ultimately, it seems that the Fairchild A-10 Thunderbolt II is not only the safest, but also the most feared and respected CAS aircraft in the world.
This article was written by Divan Muller and was first published in African Pilot Magazine - www.africanpilot.co.za