Non-Subscriber Extract
Down in the dirt: helicopter brownouts
By Gareth Jennings
13 February 2008
Brownout - the effect of swirling dust and debris caused by the rotors' downwash obscuring a pilot's vision during the take-off and landing of a helicopter - has long been a problem for rotary-wing operations. However, it is only in recent years, with the US-led wars in Afghanistan and Iraq, that the drive to solve it has taken on such a degree of urgency.
Helicopters are today being called upon to conduct operations in environments and at tempos that were not conceived of at the conceptual planning stage of their development nearly 20 years ago. As Phil Naybour, head of Helicopter Operations for Thales Helicopter Business Line, succinctly put it: "If you're looking at patrolling the East German border then you probably don't get brownout that often."
Figures released in June 2007 by the United States' Project On Government Oversight - a non-governmental organisation - show that the US Army suffered 41 brownout incidents from Fiscal Year 2002 (FY02) to FY05, with the percentage of brownout-related accidents rising from 8.7 per cent of all US Army helicopter accidents before the invasion of Iraq to 17.6 per cent during it. One senior US military source has even put the figure as high as three out of every four helicopter accidents in desert conditions being directly attributable to brownout.
According to the US Army Safety Center, "spatial disorientation (SD) accidents result in the tragic loss of 40 lives on average per year. The cost of SD accidents also includes mission failure, the impairment of mission effectiveness, the monetary value of aircraft and equipment lost, and fatalities and disabilities. The estimated annual materiel cost of SD accidents is in the billions of dollars".
Figures released to Jane's under the UK Freedom of Information Act show that the Ministry of Defence (MoD) has suffered 16 helicopter brownout incidents between 2000 and 2007, including the loss of an Aerospatiale Gazelle light utility helicopter in February 2000 during what the MoD described as a "dust landing".
As well as the risk of serious injury or death, brownouts can cause mechanical failures due to the ingestion of sand, the accelerated wear of rotor blades and rotor gear and the increased general wear on engine parts and filters. The time between overhaul is substantially shortened when operating in such an environment and the service life of the fleet can be dramatically reduced.
Surprisingly, given the vastly increased number of rotary-wing operations being flown by the US and UK armed forces in desert environments over recent years, neither the US Department of Defense (DoD) nor the MoD have formally documented a requirement for a material solution for operations in degraded visibility environments (DVEs).
Even so, all branches of the US armed forces and the MoD have identified brownout and obstacle-detection/avoidance issues as a high rotary-wing priority.
Greg Lund is chief pilot for FLIR Government Systems and a former US Army pilot with extensive experience on the Boeing AH-64 attack helicopter and the Sikorsky UH-60 transport helicopter, including two tours of Afghanistan where he grappled with brownout on a "daily basis". Piloting a medical evacuation (MEDEVAC) UH-60, Lund noted that "landing in unimproved locations, we experienced brownout on every occasion. Every time we came close to the ground there was a dust cloud".
Image: A US Marine Corps MV-22 demonstrating extreme brownout conditions during testing at the US Army's Yuma Proving Ground, Arizona (US DoD)