Brownout (aviation)

In aviation, a brownout (or "brown-out") is an in-flight visibility restriction due to dust or sand in the air.cite book
publisher = National Transportation Safety Board
title = Special Investigation Report on Emergency Medical Services Operations
version = PB2006-917001
date = 2001-06
url = http://www.ntsb.gov/publictn/2006/SIR0601.pdf
id = NTSB/SIR-06/01
accessdate = 2007-06-26
quote=Brown-out conditions connote in-flight visibility restrictions due to dust or sand in the air.] In a brownout, the pilot cannot see nearby objects which provide the outside visual references necessary to control the aircraft near the ground.cite paper
first = David L.
last = Key
date = 1999-09-14
title = Analysis Of Army Helicopter Pilot Error Mishap Data and The Implications For Handling Qualities
issn =
doi =
url = http://www.aero.polimi.it/~rolando/bacheca/imprimatur/Pilot_Error_Analysis.pdf
accessdate = 2007-06-23 ] This can cause spatial disorientation and loss of situational awareness leading to an accident.Cite web
title = AFOSR News - National Helicopter Experts Gather to Discuss Aerodynamic Solutions for Brownout
author=Stein, Vicki
publisher=The Air Force Office of Scientific Research, AFRL
accessdate = 2007-06-25
date=2007-02-12
url = http://www.afosr.af.mil/News/nr_2007_03_helicopterExperts.htm] Pilots have compared landing during brownouts to parallel parking an automobile with your eyes closed.

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. [Cite web
title = STO: Solicitations - Sandblaster Program
publisher=Defense Advanced Research Projects Agency
accessdate = 2007-06-24
url = http://www.darpa.mil/sto/solicitations/BAA06-45/index.html] Brownouts have claimed more helicopters in recent military operations than all other threats combined.cite news
date=2005-03-01
title=Military Spin
first=Lt. Col. Steve
last=Colby
work=Rotor & Wing
publisher=Access Intelligence, LLC
url=http://www.aviationtoday.com/rw/training/specialty/1418.html
quote=Brownouts have claimed more helicopters in recent military operations than all other threats combined.]

There are several factors which affect the probability and severity of brownout:
*rotor disk loading
*rotor configuration
*soil composition
*wind
*approach speed and angle

Countermeasures to prevent brownout related accidents include:
*Site preparation
*Pilot technique
*Synthetic vision systems also known as "see and remember" [cite news
url=http://www.flug-revue.rotor.com/FRNews1/FRNews07/FR070318.htm
title=News in Brief / Kurzmeldungen
date=2007-03-18
work=Flug Revue (Germany)
publisher=Motor-Presse Stuttgart]
*Upgraded horizontal situation indicator with improved symbology [cite news
url=http://www.vtol.org/news/issues704.html
publisher=AHS International
title=Vertiflight Breaking News : Army Prepares Brownout Kit
date=2004-07
accessdate=2007-06-28
quote= 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.]
*Aerodynamics such as the "winged rotor" on the AgustaWestland EH101

Sensory illusions

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. [cite news
title=Desert sandstorms add dangers for pilots
date=2003-04-09
first=Dr. Charles
last=Lessard
work=Texas A&M Engineering
publisher=Texas A&M Universityurl=http://engineer.tamu.edu/news/story/?p_news_id=464]

In night landings, aircraft lighting can enhance the visual illusions by illuminating the brownout cloud. Another phenomenon observed at night is "Pixie dust" caused by small particles hitting the leading edge of the rotor blades and making tiny sparks, creating a disk-shaped sparkling glow around the rotor. This effect can also produce spatial disorientation in the uninitiated pilot.cite news
date=2005-07-01
title=Military Spin
first=Lt. Col. Steve
last=Colby
work=Rotor & Wing
publisher=Access Intelligence, LLC
url=http://www.aviationtoday.com/rw/commercial/ems/1652.html
quote="Pixie dust" is a strange phenomenon often encountered during night brownout landings.]

U.S. military experience

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. [cite news
url=http://www.quad-a.org/Archives/070405/GantApril-May07.pdf
title=Owning the Aviation Edge : NVGPID: A Simple Device to Train Crucial Skills
Author=Gant, Randall, CW5
work=Army Aviation
publisher=United States Army
date=2007-04
page= 22]

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. [cite news
title=Flying Blind in Iraq: U.S. Helicopters Navigate Real Desert Storms
first=Leslie
last=Sabbagh
work=Popular Mechanics
date=2006-10-03] 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.cite journal
first = LTC Ian P.
last = Curry
year = 2006
month = 01
title = Situational Awareness and Spatial Disorientation in the Fight
journal = FLIGHTfax
publisher = Unites States Army
issn =
doi =
url = https://crc.army.mil/MediaAndPubs/magazines/flightfax/2006_issues/ffjan06.pdf
accessdate = 2007-06-23 ]

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.cite news
url=http://stripes.com/article.asp?section=104&article=14191&archive=true
title=Desert landings rattle pilots' nerves
first=Steve
last=Liewer
work=Stars and Stripes, European edition
date=2003-04-14]

The CH-47 Chinook has had a relatively high frequency of brownout accidents. As of 2007, 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. [cite news
title=Nobody's First Choice : Another Air Force deal that doesn't pass the smell test
first=Michael
last=Goldfarb
date=2007-04-19
work=The Weekly Standard
url=http://www.weeklystandard.com/Utilities/printer_preview.asp?idArticle=13532&R=11369982] 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. [cite news
author=United Press International
title=Rescue Helicopter has Brownout Problems
url=http://www.upi.com/Security_Terrorism/Briefing/2007/06/21/rescue_helicopter_has_brownout_problems/8339/
quote= 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.]

Brownout is a particular concern for the U.S. V-22 Osprey tiltrotor aircraft, [cite paper
title=V-22 Program Status Report to Congress
author=United States Department of Defense
url=http://www.g2mil.com/ReporttoCongress04-2002.pdf
date=04-2002] 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. [cite news
title=Combat, With Limits, Looms for Hybrid Aircraft
first=Leslie
last=Wayne
date=2007-04-14
work=New York Times
url=http://www.nytimes.com/2007/04/14/business/14osprey.html?ex=1334203200&en=4dc39587d0ab00dd&ei=5088&partner=rssnyt&emc=rss
quote=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...] 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. [cite web
url=http://www.dash2.com/204_interview.htm
title=Interview - Major Rob Freeland, VMMT-204 - Former Operations Officer and CH-46 pilot.
author=Llinares, Rick
publisher=Dash 2 Aviation Photography
accessdate = 2007-06-23
date=2006-11-11]

Partial list of related accidents

Civilian

*August 18, 2001, Vinton, California — Rocky Mountain Holdings, Aerospatiale AS355F1 (N53LH) — MEDEVAC helicopter damaged in dynamic rollover after an aborted takeoff at a remote location, with no injuries. The helicopter was substantially damaged. Pilot experienced brownout after lifting off approximately 3 feet (1 meter) off the ground. [cite web
url=http://www.ntsb.gov/ntsb/brief.asp?ev_id=20010822X01755
title=NTSB Accident Brief: LAX01LA283
publisher=National Transportation Safety Board
date=2005-06-08
accessdate=2007-06-26]

* September 22, 2001, Chico, California — Enloe Medical Center Aerospatiale AS350BA (N911NT) — helicopter was destroyed after colliding with trees in an aborted landing at a ballpark killing the pilot and injuring one of two flight nurses on board. Witnesses on the scene reported a brownout cloud obscured their vision of the accident sequence. [cite web
url=http://www.ntsb.gov/ntsb/brief.asp?ev_id=20011002X02023
title=NTSB Accident Brief: LAX01LA304
publisher=National Transportation Safety Board
date=2005-06-08
accessdate=2007-06-26]

* March 21, 2004, Pyote, Texas — Med-Trans Bell 407 (N502MT) — EMS helicopter crashed into terrain while maneuvering in reduced visibility at night while transporting a patient. The pilot, flight paramedic, patient, and patient’s mother were killed, and the flight nurse was seriously injured. Witnesses reported brown-out conditions at the time of the accident.

* June 26, 2004, Cibecue, Arizona — Native American Air Ambulance AS350B3 (N5226R) — MEDEVAC helicopter landed hard on a baseball field in a brownout, damaging the tail boom, but without injuring the crew. The damage was not discovered on a post-flight inspection, or subsequent pre-flight inspections, and was only noticed by a aircraft maintenance technician 8 days later. [cite web
url=http://www.ntsb.gov/ntsb/brief.asp?ev_id=20040917X01456
title=NTSB Accident Brief: LAX04LA285
publisher=National Transportation Safety Board
date=2005-09-13
accessdate=2007-06-26]

* August 16, 2005, Donnelly, Idaho, Heliflite LLC, Hughes 369E (N500FU), helicopter was substantially damaged when the main rotor blade hit a tree on landing, with no injuries. Recent construction work at the site disturbed the surface, creating unexpected brownout conditions. [cite web
url=http://www.ntsb.gov/ntsb/brief.asp?ev_id=20050914X01452
title=NTSB Accident Brief: SEA05CA173
publisher=National Transportation Safety Board
date=2005-12-20
accessdate=2007-06-26]

Military

* October 19, 2001, Dalbandin, Pakistan — U.S. Army Rangers, Task Force 3/75 MH-60K Black Hawk — As the search and rescue helicopter approached to land at night, it caused a brownout, obscuring the landing area. The aircraft crashed into a sand dune, killing two rangers on board as passengers, and injuring three others. [cite book | last = Bahmanyar | first = Mir | title = Shadow Warriors: a History of the Us Army Rangers | publisher = Osprey Publishing | location = Reading | year = 2006 | isbn = 1846031427 | pages = p. 184] [cite news
title=Officials Report on Chinook Incidents in Afghanistan
work=wo Soldiers Killed; Special Forces Assault Taliban Sites
publisher=United States Department of Defense
date=2001-10-20
url=http://www.defenselink.mil/news/newsarticle.aspx?id=44628] [cite web
url=http://www.globalsecurity.org/military/facility/dalbandin.htm
publisher=Globalsecurity.org
title=Dalbandin, Pakistan : 28°52'41.15"N 64°24'12.54"E
accessdate=2007-06-28
quote=The search-and-rescue Black Hawk helicopter crashed into a sand dune near the perimeter of the airfield in Dalbandin.]
* December 6, 2001, Forward operating base (FOB), Afghanistan — U.S. Marine Corps, HMM-365, UH-1N — Helicopter inadvertently touched down on takeoff while drifting to the right and rolled over. One member of the crew was ejected, and the other three exited before the aircraft was destroyed by fire. Another nearby helicopter was damaged by flying debris from the rotor. [cite news
work=Naval Aviation News
publisher=Naval Aviation
volume=86
number=6
page= 4
author=Wilbur, Ted
date=2004-09-01
title=Brownout.(Grampaw Pettibone)
url=http://findarticles.com/p/articles/mi_m0IAX/is_6_86/ai_n6220833]
* August 12, 2002, FOB, Operation Enduring Freedom — U.S. Air Force, 347th Rescue Wing, HH-60G Pave Hawk — helicopter departed slowly and had insufficient power to climb out of the dust cloud generated on take-off from its own rotor wash. The pilot tried to land and hit a sand berm. The six aircraft occupants evacuated without serious injury. [cite news
work=AIR FORCE Magazine
date=2003-02
pages = p. 24
title=Aerospace World
first=Suzann
last=Chapman]
* February 13, 2003, near Ali Al Salem Air Base, Kuwait — U.S. Air Force, 20th Special Operations Squadron, MH-53M (s/n 10930) — helicopter was badly damaged when crew misjudged a night landing in brownout conditions. Some minor injuries. Aircraft was salvaged. [Cite web
title = 1968 USAF Serial Numbers
accessdate = 2007-06-25
date = 2007-06-01
url = http://home.att.net/~jbaugher/1968.html]
* March 23, 2003, U.S. Army Aviation Base Camp, Central Iraq — U.S. Army 6th Cavalry Regiment, AH-64D Apache Longbow — helicopter crashed on takeoff on the unit’s first day at that base camp.
* March 28, 2003, Iraq — U.S. Army 101st Aviation Regiment, AH-64D Apache — while departing from FOB Shell for a combat mission with approximately 40 other fully loaded helicopters, the helicopter rolled over in severe brownout approximately 4 minutes after the first aircraft took-off.cite book | last = Bernstein | first = Jonathan | title = Ah-64 Apache Units of Operations Enduring Freedom and Iraqi Freedom | publisher = Osprey Publishing (UK) | city = Oxford | year = 2005 | isbn = 1841768480 | pages = pp. 53-54 ] cite news
work=Cable News Network
title=On the Scene : First deep attack
date=2003-03-29
last=Chilcote
first=Ryan
url=http://www.cnn.com/2003/WORLD/meast/03/29/otsc.irq.chilcote/index.html
quote=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.]
* March 28, 2003, Iraq — U.S. Army 101st Aviation Regiment, AH-64D Apache (97-5032) — after returning to FOB Shell from a combat mission, the helicopter landed hard in brownout conditions, rolled over, and was severely damaged (though later salvaged and repaired).
* March 31, 2003, Iraq — U.S. Army 103rd Aviation Regiment, AH-64D Apache (99-5104) creates brownout on takeoff for a MEDEVAC escort mission, resulting in main rotor strike, rollover, and loss of the aircraft. [cite book | last = Cordesman | first = Anthony | title = The Iraq War | publisher = Praeger | location = New York | year = 2003 | isbn = 0275982270 | pages = p. 255]
* April 5, 2003, Camp Thunder Road, Kuwait — U.S. Army 101st Aviation Regiment, UH-60 Black Hawk — helicopter collided with a sling load during a pickup attempt in brownout conditions. The three injured crew members pulled the two seriously injured pilots from the burning wreckage before it was destroyed by fire.cite news
title=U.S. helicopter crash-lands in Iraq, injuring pilots, crew
work=Milwaukee Journal Sentinel
date=2003-04-07 by KATHERINE M. SKIBA
first=Katherine M.
last=Skiba
url=http://findarticles.com/p/articles/mi_qn4196/is_20030407/ai_n10880884
quote=Pilots have compared landing during brownouts to parallel parking a car with your eyes closed.]
* April 26, 2004, location not specified — U.S. Marine Corps, HMM-266, CH-46E — Hard landing during brownout. Rotor blades struck terrain, but helicopter remained upright. [cite news
title=Corrosion repairs using the radial bristle disc.(Air Wing Toolbox)
date=2004-06-22
author: Doughty, Thomas
url=http://www.encyclopedia.com/doc/1G1-123580046.html]
* July 27, 2005, Spin Buldak Afghanistan — Royal Netherlands Air Force, 298 Squadron CH-47D Chinook (D-105) — helicopter made a "hard landing" due to "brown-out conditions" as the crew was attempting to insert forces on the border between Afghanistan and Pakistan. The aircraft was destroyed by fire but there were no injuries. [cite news
title=Officials Report on Chinook Incidents in Afghanistan
work=American Forces Press Service
publisher=United States Department of Defense
date=2005-07-28
url=http://www.defenselink.mil/news/newsarticle.aspx?id=16541] [cite web
url=http://www.touchdown-aviation.com/orbats/rnlaf/298sq.htm
title=Touchdown Aviation - Royal Netherlands Air Force - 298 Squadron
accessdate=2007-06-24
quote=D-105 was lost on the 27th of July and replaced by the D-104]

References

ee also

* Safety of emergency medical services flights
* Hazards of helicopter flight