Friday, June 3, 2011

The Apache AH1


The Attack Helicopter requirement

The requirement for a new attack helicopter was identified by the British government in the early 1990s. In 1993, invitations to bid were issued. Bids recieved included the Eurocopter Tiger, a modernised Bell AH-1 SuperCobra, the Boeing AH-64 Apache, the Boeing/Sikorsky RAH-66 Comanche, and the Agusta A129 Mangusta. Both the Tiger and Cobra variant were derided for requiring development, and thus risk, while the Apache was combat proven. The Apache was selected in July 1995, a contract for 67 helicopters was signed in 1996, with license production to be done by Westland. The first prototype WAH-64D Apache AH1 was produced by Westland, under licence from Boeing, in September 1998. The first 8 series helicopters were then built by Boeing, and the Initial Operational Capability was reached with nine Apache AH Mk1 helicopters on 16 January 2001. The remaining helicopters were all Westland-built, and the 67th and final Apache was handed over to the British Army in July 2004. The cost of the helicopter fleet was around £3.1 billion, with a total aquisition cost of £4.1 billion. Amounts of helicopters of course varied more than once during the story of the programme: from an ambition for 125, which would have seen even the 847 NAS (Commando Helicopter Force’s Scout and Attack squadron) armed with the new helo, to 91 then to 67. In May 2005, the first Apache regiment achieved operational status. In 2006 the Apache was deployed to Afghanistan, and a 8-choppers detachment remains there to this day.

The programme risked being cancelled in 1999 when the US grounded their whole Apache fleet as a precaution after a rear rotor failure, and again when the Longbow radar met development problems. The armored threat of the URSS block had also been becoming less and less probable a future enemy, leading to calls for the scrapping of the attack helicopter. But luckily, the 2001 Strategic Defence Review did confirm the requirement, and also called for Apaches to be able to undertake amphibious attack missions, operating from the helicopter carrier HMS Ocean, the Invincible class aircraft carriers and their successors, and possibly from the amphibious assault vessels HMS Bulwark and Albion. Each squadron equipped with the Apache was mandated a strength of eight operational aircraft. 

An Apache AH1 approaches HMS Ocean to land on her deck.

Apache AH1: design

The UK’s Apaches, WAH64D Apache AH Mk1 or simply AH1, did thus receive some very substantial changes from their American counterpart. One major difference for the WAH-64 is the folding blade mechanism to stow the helicopters in confined spaces and for operations at sea; the rotor blades also have anti-ice protection to allow operations in arctic environments. Interestingly, the US Army looked at this idea with interest: their focus was less on Ship-capability, and more on ease and rapidity of air transportation of Apache into theatre, but the end result has been the same, since their November 2002 requirement was met with folding blades. The folding blades allows the main rotor to be folded along the aircraft's length without being removed. The solution also provides for storage of the Apache Longbow's radar dome on the aircraft aft of the rotor hub for transport. 

Apache with rotor folded. This gives the Apache roughly the same Deck Footprint of a Folded Merlin helicopter or Sea King. The Apache is slightly longer (17.76 meters vs 16.9) and larger (5.5 against 5.2). The folding rotor speeds up and eases also air transportation within cargo planes such as the C17. 

Theblade fold system also saves space. A single C-5 aircraft can now carry six Apaches, their flight crews, reassembly technicians and their tools. In the past, a second aircraft was needed to haul in special reassembly equipment, and additional personnel, and only 5 Apaches were carried. The blades had to be removed and stored along with the radar apart from the aircraft, taking up space in the cargo airplane and requiring more time to reassemble at the Apaches' destination. Folding blades remove the need for a test flight, necessary after a disassembly/reassemply op, and significantly reduces the logistics load required to deploy.

A C17 can carry 3Apaches, while without folding blades that would be 2.

Another major change is the usage of a pair of Rolls-Royce Turbomeca RTM322 01/12 engines, replacing the original General Electric T700-GE-701C engines. The Rolls-Royce engine produces 1,565 kW (2,100 hp) vs 1,410 kW (1,890 hp) for the GE T700C engines, meaning that the UK’s Apache is significantly more powerful (a 19% boost), and better performs in hot and dry conditions. Even the GE T700-701D, planned for the upgrade Apache Block III of the US Army, only reaches 1,490 kW. It is known that US Apaches in Afghanistan have had to dismount their Longbow radars, while UK Apaches do not need this. Even with the RTM322 engines, however, rolling takeoffs are common in Afghanistan’s hot, high-altitude conditions for WAH-64Ds with full fuel and weapons. The Apaches proved invaluable in Afghanistan, and in 2007 it was undisclosed that they were regularly exceeding their planned flight hours by 20-30%. Indeed, this lead to serious availability problems, as insufficient spares and mainteinance started biting. To contrast this, AgustaWestland acquired rights from Boeing and progressively brought Apache mainteinance in-house in the UK. The process has quite recently been completed, and now the UK Apaches are maintained in the UK, while before they had to be sent in the US. Availability has been improving.

The Apache AH1 is fitted with the Longbow radar, very visible and characteristic thanks to its placement above the rotors, which also allows the Apache to hover behind cover scanning for targets, with only the radar unit exposed. The radar, truly ground-breaking at the time of its appearance, can track 256 targets and prioritize up to 16 for immediate engagement in just a few seconds. The Longbow radar over Stan has not been chasing tanks and armored vehicles as it is meant to do, but it still is used for a variety of roles. The Longbows can act as aerial coordinators, using their radars to keep track of other helicopters, jets, and UAVs in their airspace – especially at night. They also sweep large areas of desert terrain, and on at least one occasion the radar’s ability to penetrate dust and other obscurement helped the pilot talk a CH-47 Chinook onto a landing zone, after the Chinook pilot’s night vision goggles had become useless. It is a precious asset, and makes flying in congested air spaces a lot safer and easier. 

There were of course other changes made to the sensor and avionics outfitting the craft as well, among which obviously featured connectivity with the BOWMAN secure communications system to interact with other British military units. The SELEX (formerly BAE Systems Avionics) Helicopter Integrated Defensive Aids System (HIDAS) was also fitted. The HIDAS system was retrofitted onto the aircraft in mid-2004 just prior to entering service, along with several redesigned composite bodywork components. An eye-safe training laser was also installed.

The UK Apache uses the same Hellfire missiles of the US ones, but instead of the American Hydra 70 rocket pods, the Westland Apache can carry up to 76 CRV7 rockets. The CVR7 comes with a variety of warheads, and the most controversial is the WDU-500X/B "General Purpose Flechette" for use against personnel, some light armour, think skin vehicles and helicopters which releasing 80 tungsten flechettes that can penetrate 1.5 inches of roll-hardened armor, which some consider a submunitions-weapon, to be banned. This though ignores the fact that the flechettes do not contain explosive, and deliver their effects by means of kinetic energy. The WDU-5002/B FAT warhead, Flechette Anti-Tank, contains five tungsten-reinforced steel flechettes that can penetrate a T-72's side and top armour at a distance of 10,000 feet (3,000 m). Bristol followed this with the 16 lb WDU-50001/B "Anti-Bunkerette" round, a semi-armor piercing high explosive incendiary (SAPHEI/HEISAP) warhead designed specifically for use against reinforced concrete buildings, specifically hardened aircraft shelters. Its heavy steel shell allows the round to penetrate the hangar wall before the 75 g incendiary warhead is ignited. The round can penetrate 13 ft of earth, 3 ft of concrete and 1 inch of steel, in series. An HE, a Smoke and a Flare warheads are also available, plus of course training rounds. In 2006 a laser-guided CVR7 rocket, CVR7-PG, was revealed. 

The fearsome Flechette CVR7 rocket is a deadly multipurpose weapon, blessed by being quite cheap and quite accurate, even without a guidance system. Its speed and kinetic energy tend to naturally keep the weapon on course and reduce dispersion.
 
The helicopter is armed with a chin-mounted Hughes M230 Chain Gun 30 mm, single-barrel automatic cannon developed by Hughes and now manufactured by Alliant Techsystems. It is an electrically operated chain gun, a weapon that uses external power instead of recoil to load its rounds. It uses a 2 hp electric motor to load 30 mm linkless ammunition at a rate of 625 ± 25 rounds per minute. The gun requires a spool-up time of 0.2 seconds to achieve this rate of fire. The practical rate of fire is about 300 rounds per minute with a ten minute cooling period as the gun is air cooled. The gun has a positive cook-off safety for open bolt clearing, and double ram prevention. Spent casings are ejected overboard through the bottom of the gun. The 30 x 113 mm M789 is typically used in the M230. Each round contains 21.5g of explosive charge sealed in a shaped-charge liner. The liner collapses into an armor-piercing jet of molten metal that is capable of penetrating more than 2 inches of RHA. Additionally, the shell is also designed to fragment upon impact. The lethal radius against unprotected, standing targets is about 10 feet under optimum conditions. The M789 requires about 2 seconds to travel 1,000 m. However, as the shell slows down, it takes over 12 seconds to cover 3,000 m. Effective range is 1500 meters, maximum is 4500. The Apache is capable of carrying up to 1,200 rounds for the gun.

AgustaWestland have since made several upgrades to Britain's Apache fleet. In May 2005, a $212 million contract was awarded to equip all 67 Mk1 helicopters with the Apache Arrowhead sensor system upgrade, to be completed by 2010. It uses second-generation long-wave Forward looking infrared (FLIR) sensors with three fields of view, a CCD TV camera, dual field of view pilotage FLIR, electronic zoom, target tracker and auto-boresight.
In 2009, it was announced that AgustaWestland was also integrating new external fuel tanks with ballistic protection. These are known as Reduced Capacity External Fuel System tanks, from Robertson. These fuel systems are the same size of the non-crashworthy, non-armored self-deployment fuel tanks (4 can be carried at the weapon pylons) but have a reduced capacity because of an internal self-sealing protection, making them suitable for use in war zone. Two are cleared for use on the inwards weapon pylons. With four external, uncrashworthy fuel tanks the Apache AH1 can fly for up to 1900 km in order to self-deploy.

The UK Apaches in Afghanistan also use a Combo Pack IAFS+, also from Robertson, which reduces the ammunition load for the gun from 1200 to 300 rounds, but gives 100 gallons more of fuel, allowing a 45 minutes increase in mission endurance. For self-deployment, the whole ammunition load can be eventually replaced with a larger IAFS+ tank, for 130 gallons.

On 17 May 2011, the Apache tested its Hellfire missiles against sea targets for the first time, in a training exercise off Gibraltar. 4 helicopters from 665 Squadron Army Air Corps, embarked on HMS Ocean, fired 9 missiles with a success rate of 100%, completing 665 Squadron’s qualification for full ship ops. Days later, HMS Ocean was committed to Operation Ellamy, the UN-authorized campaign of air strikes against Libya. 

A wonderful cutaway of the Apache Longbow. The Rolls Royce/Turbomeca engine is shown.

The Apache will stay in service at least until 2030, and probably much longer. One of the future targets of the British Army modernization is the Apache fleet, for which there is desire to join the US programme of upgrade to Block III standard. The Americans signed the contracts in 2006, and deliveries started in 2007: hundreds of Apaches are being upgraded, and the British Army likely wants to try and secure funding to insert its own helicopters as a tail to the US programme. The upgrades mainly involve the avionics, enhance network capability, allow the Apache to work with UAVs (and makes the Apache crew capable to control UAVs in flight, something the RAF experimented with a modified Tornado GR4), replaces the rotor blades with new ones in composites, and improves performances. It also lengthens the life of the fuselage and, for US helicopters, replaces the engines with more powerful ones. The UK would not take this on, though, as the current Rolls Royce turbine still has an advantage even on the latest GE one! Reduced  cost for flying hour and improved maintenance progress, with addition of diagnostic capability, is also planned. It is likely that the upgrade will move the retirement date of Apache AH1 all the way to 2040, if not further away.  

AgustaWestland/Boeing AH64D Apache AH MK1 


General characteristics

  • Crew: 2
  • Length: 17.7 m (58 ft 4 in with rotors turning)
  • Rotor diameter: 14.6 m (48 ft)
  • Height: 3.87 m (12 ft 8 in)
  • Disc area: 168.11 m² (1,809.5 ft²)
  • Empty weight: 5,165 kg (11,387 lb)
  • Loaded weight: 8,006 kg (17,650 lb)
  • Max takeoff weight: 9,525 kg (21,000 lb)
  • Powerplant:Rolls-Royce/Turbomeca RTM322 turboshaft, 1,566 kW (2,100 hp) each
Performance

  • Never exceed speed: 365 km/h (197 knots, 227 mph)
  • Maximum speed: 293 km/h (158 knots, 182 mph)
  • Cruise speed: 259 km/h (140 knots, 161 mph)
  • Range: 475 km (295 miles) – 476 Km indicated for US Apache Longbow. Evidently the RTM322 is not an insatiable drain of fuel despite its greater power.
  • Ferry range: 1,700 km (1,121 mi)
  • Service ceiling: 6,400 m (21,000 ft)
  • Rate of climb: 12.7 m/s (2,500 ft/min)
Armament
  • Guns: M230 Chain Gun, up to 1156 rounds
  • Missiles: Hellfire (and Stinger or Starstreak for AA) – Up to 16 in 4 launchers
  • Rockets: CRV7, with Flechette (Tungsten dart) or High-Explosive Incendiary Semi-Armour Piercing (HEISAP) warhead. Up to 76 in 4 pods
Typical Apache armament configuration (UK):
·         2 x 19 rockets pods CRV7
·         2 x 4 Hellfire missiles
·         300 x 30 mm gun rounds and 100 gallons extra fuel in Robertson Combo Tank.


For Self-Defence, the Apache can be armed with 4 Stinger AA missiles in two twin wingtips launchers, and ATASK (Air To Air Starstreak) has also been successfully tested. The ATASK, also known as Helstreak were tested as far back as 1997, since for some time the ATASK was considered with interest by the US Army for its own Apaches. The laser beam guidance system of Starstreak can beintegrated with the target acquisition sight (TADS) and fire control system of the Apache.

The performances of the Apache depend of course on the loads carried: the Apache Longbow has slighty lower performances than the original Apache AH-64A, because of the Radar, and other additional weight. The Apache AH1 has better performances thanks to its more powerful engines, and since fuel consume is almost perfectly the same, range remains equal. Indicatively, though, performance for weapons-load are comparable to those indicated in this useful US Army table: 


The words of  Chief of the General Staff, General Sir Charles Guthrie, who in 1996 said: "I have no doubt whatsoever that the Attack Helicopter will represent the biggest single enhancement to the Army's capability for many years. It will change the way we go to battle." have certainly proved true. The Apache is proving its worth on all fronts, and will continue to be a fundamental Army capability well into the future. 

3 comments:

  1. Good article about Apache; only I'm fairly certain that UK Apache fleet has never returned to the US for maintenance. Yes, some components were and are still returned direct to manufacturer for repair / overhaul; AW are slowly taking on more of this work where possible.
    Good work Gabriele, very well informed.

    regards

    UK Apache Engineer

    ReplyDelete
  2. This may be of interest:
    http://www.airplane-pictures.net/photo/277131/zj217-uk-army-westland-apache-ah-1/

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