On 2 November, Boeing delivered the first two of 690 AH-64D Apache Longbow Block III attack helicopters to the US Army.

A training aircraft will also be delivered to the first export customer - Taiwan - in mid-2012, with the balance of the nation's order for 30 Block III aircraft to begin delivery a year later.

The Block III version of the AH-64D is also the only aircraft now being considered by the Indian defence ministry for its attack helicopter contest, after the nation eliminated a rival bid from Russia's Mil Mi-28N.

And the US airframer's latest rotorcraft product is close to completing deals all over the world, including in Saudi Arabia and South Korea - not bad for a helicopter programme that survived at least two evolutions of its operational purpose since it was launched.

The AH-64D Block III now has no true competitor that can match its capability in the heavy helicopter gunship market.

The Block III programme was conceived in the immediate aftermath of a notorious operational deployment.

In 1999, Task Force Hawk revealed glaring performance shortfalls in the AH-64D, which Lt Col Dan Bailey - a member of the ill-fated task force, and now AH-64D Block III product manager - said was unable to fly with a full weapons load in the mountains of Albania.

Two decades of added bulk - including new sensors, weapons and support equipment - had eroded the Apache's lift and speed by 1999.

In response, the Block III introduces upgrades to the transmission with a split-torque face gear, allowing US manufacturer General Electric to increase the thrust rating of its T700-701D engines from 2,830shp (2,080kW) to 3,400shp.

Four years later, the AH-64D was again caught off guard. The Apache fleet generally performed well in the second invasion of Iraq in 2003, but a pre-planned deep strike mission on 24 March was a debacle. An Apache force was ambushed by Iraqi villagers and militiamen, and one aircraft was downed - possibly by a mere rifle bullet.

"That specific fight was not a decision point for [Block III]," said Col Shane Openshaw, AH-64 programme manager, adding: "It was an opportunity to re-look at the way we were going to use the aircraft."

Never again would a large formation of Apaches fly deep and alone into enemy territory.

The Block III standard allows the AH-64D to control unmanned air systems (UAS) - so instead of flying deep behind enemy lines alone, UAS could fly ahead of the formation and watch for anything unusual.

Nearly a year after the ambush, the army formally launched the Block III modernisation programme in February 2004. At the time, it planned to make the AH-64D a central node in the battlefield network in development by Boeing's Future Combat System (FCS) programme.

However, that part of the Block III programme's original justification was lost when the army terminated FCS.

The new variant includes additional antennas to communicate with UAS, but the ability to communicate with US Air Force aircraft will not arrive until a Link 16 datalink is added in a few years.

Other communications waveforms, such as the soldier networking waveform and wideband networking waveform, will not be integrated for several years.

In the aftermath of FCS' termination, Block III was re-cast as a service life extension programme and a necessary performance upgrade to keep the AH-64D fleet relevant through to its planned retirement in 2040.

Despite so many concept revisions, the demand for the Block III upgrades for the Apache never wavered. Rotorcraft of all types remain a top priority in the US military's acquisition plans. While budgets are starting to tighten, the AH-64D Block III is still fully-funded - and after orders for 51 aircraft in the low-rate initial production phase, the army is scheduled to make a full-rate production decision in August 2012.

Approval is expected, and the only debate is how fast the service will buy new Block IIIs.

The minimum rate is to deliver enough aircraft to equip a single combat aviation brigade with two battalions a year, Bailey said - and that is not expected to change.

Source: Flight International