Anti-aircraft fire prompts army to modify methods
Blinding sand, adverse weather and intense ground fire are providing a formidable operating environment for the US Army's helicopter fleet, particularly the Boeing AH-64D Apache Longbow, now at the vanguard of coalition forces attacking the Iraqi army's Republican Guard, south of Baghdad.
The US Army has been forced to reassess its tactics in the wake of the first massed helicopter assault against the Republican Guard's Medina Division near Karbala. The army cut short its 24 March attack after 30 AH-64Ds from the US Army's 11th Aviation Regiment were met with a barrage of anti-aircraft ground fire, including rocket- propelled grenades.
One AH-64D was forced down and its two-man crew captured, while many of the other helicopters returned with battle damage, including one machine that had lost one of its two General Electric T700 turboshaft engines. Shortly after returning to their temporary base, the helicopters were grounded by a sandstorm and winds of up to 160km/h (100mph).
More helicopters would have been lost but for the Apache's robust design. This includes 12.7mm (0.5in) round-tolerant armoured crew seats, cockpit floor and sides, along with a 23mm tolerant transparent blast shield between the pilot and forward co-pilot/gunner. The helicopter features self-sealing fuel cells with nitrogen inerting and ballistic foam protection against fire, redundant load paths, back-up flight controls and a gearbox capable of running for 30mins dry as proven recently during combat in Afghanistan.
Iraq's fine desert sand is proving more of a challenge than coarser material in Afghanistan and sources are blaming this for a number of forced helicopter landings in recent days. Sand ingested by engines clogs up turbine blade cooling and turns to glass when ultra hot. The army has equipped many of its helicopters with either static filters or centrifugal particle separators, but which can bleed off up to 10-15% of turboshaft engine power.
Source: Flight International
