There seem to be four different types of aircraft either in use or under consideration for close air support work:

1. attack helicopter (e.g. AH-64)
2. fixed-wing turboprop (e.g. AT-6)
3. fixed-wing jet (e.g. A-10)
4. large gunship (e.g. AC-130)

Most of these aircraft carry the same types of targeting sensors, typically EO/IR/laser, and weapons, such as guns, rockets, guided missiles, and guided bombs.

Attack helicopters have yet to be tested in a high-intensity combat environment, and when they have faced serious ground fire, they tend to suffer. They are very expensive to acquire and to maintain and operate. Their VTOL advantage is rarely used, as they usually operate from airbases. They are slow.

Fixed-wing turboprops are relatively cheap to buy, maintain and operate. They are faster than attack helicopters, almost as fast as an A-10, but slower than fighters used for CAS (e.g. F-16). They have longer loiter endurance than jets, who can persist over the battlefield only by regular air-to-air refuelling. Their weapon load is typically less than a jet.

Fixed-wing jets is a category that has two subsets – aircraft designed for CAS, typically the A-10 and Su-25; and fast jets employed for CAS missions, such as F-16s or Mirages or Tornados. It is said that troops on the ground favour slower aircraft such as the A-10 for CAS, as they are more likely to be accurate in their attacks.

The large gunship is a specialist aircraft that is only operated by the US. It seems to be only operated at night, even in relatively permissive environments such as Afghanistan, which suggests it is very vulnerable.

So it seems to me that in deciding on the most suitable CAS aircraft, the nature of the conflict (a spectrum from top-end extreme intensity down to COIN policing) needs to be considered, as does the mission: the anti-tank mission is different from providing ‘flying artillery’ support to troops in contact. After that it’s the usual balancing of costs versus effectiveness.

And finally, I would hope that inter-Service rivalry between the US Army and the USAF won’t prevent a proper testing of the fixed-wing turboprop option, which appears to offer a great deal of savings on the cost side, while maintaining the ability to get the job done.

25 were sold to Thailand, and the UK Defence Evaluation and Research Agency bought 12 as chase planes and flight test platforms. Prices were giveaway, apparently: saw one mention of $27,000 each for the Thai aircraft.

According to Wikipedia,

“Armament
Guns: 1× 27 mm (1.06 in) Mauser BK-27 Revolver cannon in centreline gun pack w/120 rds or 1x 30 mm DEFA in centerline pod w/150 rds
Rockets: 2× Matra rocket pods with 18× SNEB 68 mm rockets each; 2× CRV7 rocket pods with 19× 70 mm rockets each
Missiles: 2× AIM-9 Sidewinders; 2× Matra Magic IIs; 2× AGM-65 Maverick;
Bombs: 2,500 kg (5,500 lb) of payload on five external hardpoints, including a variety of bombs (such as the Hunting BL755 cluster bombs) or Drop tanks for extended range.”

But what can a fixed-wing CAS aircraft do that, e.g. an Apache helicopter couldn’t?