In aviation, a brownout (or brown-out) is an in-flight visibility restriction due to dust or sand in the air. [1] In a brownout, the pilot cannot see nearby objects which provide the outside visual references necessary to control the aircraft near the ground. [2] This can cause spatial disorientation and loss of situational awareness leading to an accident. [3] Pilots have compared landing during brownouts to parallel parking an automobile with one's eyes closed. [4]
The brownout phenomenon causes accidents during helicopter landing and take-off operations in arid desert terrain. Intense, blinding dust clouds stirred up by the helicopter rotor downwash during near-ground flight causes significant flight safety risks from aircraft and ground obstacle collisions, and dynamic rollover due to sloped and uneven terrain. [5] Brownouts have claimed more helicopters in recent military operations than all other threats combined (as of 2005). [6]
There are several factors which affect the probability and severity of brownout: [6]
Countermeasures to prevent brownout-related accidents include:
Blowing sand and dust can cause an illusion of a tilted horizon. A pilot not using the flight instruments for reference may instinctively try to level the aircraft with respect to the false horizon, resulting in an accident. Helicopter rotor wash also causes sand to blow around outside the cockpit windows, possibly leading the pilot to experience the vection illusion, where the helicopter appears to be turning when it is actually in a level hover. This can also cause the pilot to make incorrect control inputs, which can quickly lead to disaster when hovering near the ground. [10] In night landings, aircraft lighting can enhance the visual illusions by illuminating the brownout cloud. [11]
The visible effects of sand rotor abrasion have been extensively observed in Afghanistan. [12]
Several coalition military aircraft were lost due to roll-overs while executing dust landings during the Gulf War period of 1990–91. In the decade between then and Operation Enduring Freedom, the U.S. Army recorded over 40 cases of brownout condition accidents during training at the Fort Irwin Military Reservation National Training Center in California, and other various sites. Since 1991, there have been over 230 cases of aircraft damage and/or injury due to unsuccessful take-offs or landings in a dust environment. Although the majority of the incidents occur during landings, there have been a significant number of incidents occurring during take-offs as well. For the more than 50 brown-out incidents with damage reported to date during Army military operations in the 2001–2007 time frame, 80 percent were during landings and 20 percent during takeoffs. [13]
Helicopter brownout is a US$100 million per year problem for the U.S. Military in Afghanistan and Iraq. The Army cites brownout in three out of every four helicopter accidents there. [14] Brownout accidents occur close to the ground and at low airspeed, giving these accidents a higher survivability than other types. However, there have been deaths in military accidents in Iraq and Afghanistan, and nearly all of those were preventable. [15]
Brownout accidents destroyed or severely damaged four AH-64D Apache Longbows in the first three weeks of the 2003 Iraq invasion, while only one had been lost in combat in the same time period. The tandem seat Apache has a narrower stance than the UH-60 Black Hawk, making it more susceptible to rollover if the pilot begins to lose roll attitude control from the brownout. But at night, the Apache's infra-red vision system provides improved visibility when dust obscures the moonlight — the Blackhawk's night vision goggles only amplify available visible light. [16]
The CH-47 Chinook has had a relatively high frequency of brownout accidents. As of 2007 [update] , nine Chinooks were lost in action in Afghanistan, and at least two were caused by brownout, which likely played a role in several other incidents. [17] According to the Project on Government Oversight (POGO), 12 of 41 U.S. Army brownout accidents between 2002 and 2005 involved CH-47s. Data compiled by POGO from government sources show the Chinook flew 7 percent of all U.S. Army helicopter flight hours between 2003 and 2005 but accounted for 30 percent of all brownout-related accidents. [18]
Brownout is a particular concern for the U.S. V-22 Osprey tiltrotor aircraft, [19] which was deployed for combat in Iraq in September 2007. The high proprotor disk loading creates a high-velocity downwash, which stirs up the dust cloud from a much higher altitude. This can be a problem while hovering during personnel insertion and extraction via hoist or rope. [20] Initial operational experience indicates that although the dust cloud is larger with the MV-22 than it is with the CH-46 it is replacing, pilots report regaining visibility near the ground, allowing them to use visual references prior to landing. [21]
The Boeing AH-64 Apache is an American twin-turboshaft attack helicopter with a tailwheel-type landing gear and a tandem cockpit for a crew of two. Nose-mounted sensors help acquire targets and provide night vision. It carries a 30 mm (1.18 in) M230 chain gun under its forward fuselage and four hardpoints on stub-wing pylons for armament and stores, typically AGM-114 Hellfire missiles and Hydra 70 rocket pods. Redundant systems help it survive combat damage.
The Boeing CH-47 Chinook is a tandem-rotor helicopter originally developed by American rotorcraft company Vertol and now manufactured by Boeing Defense, Space & Security. The Chinook is a heavy-lift helicopter that is among the heaviest lifting Western helicopters. Its name, Chinook, is from the Native American Chinook people of Oregon and Washington state.
The 160th Special Operations Aviation Regiment (Airborne), abbreviated as 160th SOAR (A), is a special operations force of the United States Army that provides helicopter aviation support for special operations forces. Its missions have included attack, assault, and reconnaissance, and these missions are usually conducted at night, at high speeds, low altitudes, and on short notice.
The CH-53 Sea Stallion is an American family of heavy-lift transport helicopters designed and built by the American manufacturer Sikorsky Aircraft. The Sea Stallion was originally developed in response to a request from the United States Navy's Bureau of Naval Weapons made in March 1962 for a replacement for the Sikorsky CH-37 Mojave helicopters flown by the United States Marine Corps (USMC).
The Mil Mi-8 is a medium twin-turbine helicopter, originally designed by the Soviet Central Aerohydrodynamic Institute (TsAGI) in the 1960s and introduced into the Soviet Air Force in 1968. Russian production of the aircraft model still continues as of 2024. In addition to its most common role as a transport helicopter, the Mi-8 is also used as an airborne command post, armed gunship, and reconnaissance platform.
The AgustaWestland Apache is a licence-built version of the Boeing AH-64D Apache Longbow attack helicopter for the British Army Air Corps. The first eight helicopters were built by Boeing; the remaining 59 were assembled by Westland Helicopters at Yeovil, Somerset in England from Boeing-supplied kits. Changes from the AH-64D include Rolls-Royce Turbomeca RTM322 engines, a new electronic defensive aids suite and a folding blade mechanism allowing the British version to operate from ships. The helicopter was initially designated WAH-64 by Westland Helicopters and was later given the designation Apache AH Mk 1 by the Ministry of Defence.
The Boeing Chinook is a large, tandem rotor helicopter operated by the Royal Air Force (RAF). A series of variants based on the United States Army's Boeing CH-47 Chinook, the RAF Chinook fleet is the largest outside the United States. RAF Chinooks have seen extensive service in the Falklands War, the Balkans, Northern Ireland, Iraq, and Afghanistan.
The Bell 407 is a four-blade, single-engine, civil utility helicopter. A derivative of the Bell 206L-4 LongRanger, the 407 uses the four-blade, soft-in-plane design rotor with composite hub developed for the United States Army's OH-58D Kiowa Warrior instead of the two-blade, semi-rigid, teetering rotor of the 206L-4.
In aviation, a tailstrike or tail strike occurs when the tail or empennage of an aircraft strikes the ground or other stationary object. This can happen with a fixed-wing aircraft with tricycle undercarriage, in both takeoff where the pilot rotates the nose up too rapidly, or in landing where the pilot raises the nose too sharply during final approach, often in attempting to land too near the runway threshold. It can also happen during helicopter operations close to the ground, when the tail inadvertently strikes an obstacle.
The 5th Aviation Regiment is an Australian Army aviation unit. Formed in 1987 after the Army took over responsibility for operating helicopters from the Royal Australian Air Force, the regiment is based at RAAF Base Townsville, in Queensland. It currently forms part of the 16th (Aviation) Brigade and it operates the majority of the Army's transport helicopters. Throughout its existence, the regiment has been deployed overseas numerous times, supporting both peacekeeping and warlike operations. Since its formation elements of the regiment have made operational deployments to Cambodia, Papua New Guinea, East Timor, Iraq, Indonesia and Pakistan.
The Kopp–Etchells effect is a sparkling ring or disk that is sometimes produced by rotary-wing aircraft when operating in sandy conditions, particularly near the ground at night. The name was coined by photographer Michael Yon to honor two soldiers who were killed in combat; Benjamin Kopp, a US Army Ranger, and Joseph Etchells, a British soldier. Both were killed in combat in Sangin, Afghanistan in July 2009.
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The 159th Combat Aviation Brigade (CAB) formerly supported the 101st Airborne Division, and was stationed at Fort Campbell, Kentucky. While active, 159th CAB made the 101st Airborne Division the only US Army Division with two organic aviation brigades, and currently the 101st CAB is the only CAB supporting the unit at Fort Campbell. The 159th CAB was inactivated on 15 May 2015.
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On 6 August 2011, a U.S. CH-47D Chinook military helicopter operating with the call sign Extortion 17 was shot down while transporting a Quick Reaction Force attempting to reinforce a Joint Special Operations Command unit of the 75th Ranger Regiment in the Tangi Valley in Maidan Wardak province, southwest of Kabul, Afghanistan.
The Australian Defence Force has operated Boeing CH-47 Chinook heavy-lift helicopters for most of the period since 1974. Thirty four of the type have entered Australian service, comprising twelve CH-47C variants, eight CH-47Ds and fourteen CH-47Fs. The helicopters have been operated by both the Royal Australian Air Force (RAAF) and Australian Army.
Brown-out conditions connote in-flight visibility restrictions due to dust or sand in the air.
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(help)Pilots have compared landing during brownouts to parallel parking a car with your eyes closed.
Brownouts have claimed more helicopters in recent military operations than all other threats combined.
The [multi-function display] replaces the standard horizontal situation indicator and shows the crew digital ground velocity, analog vertical velocity, digital and analog radar altimeter, and analog heading symbology.
To counteract this, the EH101's 'winged-tip' rotor blades create what its pilots call the "donut effect" – a circular window of clear air inside the dust storm that allows them to see the ground as they come in to land.
"Pixie dust" is a strange phenomenon often encountered during night brownout landings.
Sometimes the halos appear like distant galaxies.
Data compiled by POGO from government sources show the Chinook flew 7 percent of all U.S. Army helicopter flight hours between 2003 and 2005 but accounted for 30 percent of all brownout-related accidents.
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(help)V-22 downdraft is so strong...that it can create "brownout" conditions...as a result, when rope ladders are used, the V-22 must hover at higher altitudes...
The search-and-rescue Black Hawk helicopter crashed into a sand dune near the perimeter of the airfield in Dalbandin.
Right here on the flight line in crash landings, the helicopters landing in what are called brown-out conditions, meaning the dust on the desert floor rises up and engulfs the helicopter and it is very difficult for the pilot to see the ground in those conditions and very easy to mess up the landing.
D-105 was lost on the 27th of July and replaced by the D-104