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Flying Aircraft In “Brownout” Conditions

Degraded Visual Environment / By Mr. Mark A. Schauer: Takeoff and landing are the two most dangerous periods for any aircraft. The danger is compounded when a helicopter is caught in a degraded visual environment (DVE) such as a brownout. Caused by rapidly blowing sand and dirt thrown into a vortex by the rotor blades of a helicopter, a brownout’s swirling dust gives pilots the illusion they are moving even if they are hovering stationary. Hazardous in any situation, it is particularly risky when landing in a combat zone.

A Black Hawk test aircraft performs a brownout landing to the DVE LZ at YPG.

“We are visual creatures,” said MAJ Joe Minor, Degraded Visual Environment Mitigation Program Manager who has flown multiple missions in Afghanistan. “80 percent of the information we take in is visual. You have to fight that impulse and trust the aircraft’s symbology and guidance, which takes some training.”

YPG has conducted tests of multiple technologies to mitigate this risk, but recently hosted the first portion of a significantly more comprehensive effort to gain knowledge of how best to technologically confront all manner of DVEs, from snow and fog to smoke and the flat, endless white light of the world’s snowiest places.

“This is not a panacea,” said Dr. William Lewis, director of the Aviation Development Directorate at the Army Aviation and Missile Research and Development Center. “This is something near-term and real, where everyone recognizes its importance.”

“This DVE mitigation program is a concerted effort to attack not only brownouts, but to build the capability of being able to fight in all weather conditions,” added COL Steven Braddom, director of the Aviation Applied Technology Directorate. Braddom observed that with modern infrared sensors and other technologies, night time, perhaps the most degraded visual environment of all, is now prime time for American military operations. “Dark night went from being a hazard to our greatest tactical advantage,” he said. “Now we prefer to operate in the darkest night we can find. We’d like to transform operating in other weather environmental conditions to our advantage, just like this.”

Sensors, Cueing, Flight Control
The testers are looking at three different facets of the pilot’s flight tools – sensors, cueing, and flight control—to find the best mix for flying in all types of degraded environments. For example, advanced flight controls and cueing may reduce an aircraft’s reliance on sensors in some situations. The testers are also aware that a comprehensive solution meant for all types of DVEs will likely involve trade-offs, and want to identify what the potential consequences of each could be.

“The project is trying to investigate what makes more impact in solving the DVE problem,” said Hi-Sing Silen, test officer. “The sensor is something that can see through the degraded environment. Cueing is flying virtual reality – the pilot is given a display, either head-mounted or dash-mounted, with a lot of cues that tell things like altitude and velocity.”
Though highly technical, the most visible aspect of cueing comes from symbol displays on a flip-down visor pilots look through in a DVE. There are also audio and tactile cues, such as vibrations in the seat or safety harness if flying too close to an obstacle.
“Cueing is a good solution to fly safely to a given point, but not a complete solution,” said Silen. “The advantage comes if you have accurate profiles of known terrain; but if you’re in a tactical scenario, you likely don’t have a lot of situational awarenesss as to what is going on down there. If you are in a dynamic landing zone with adversary vehicles coming in, the cueing will guide you to that point but won’t have the SA of what is going on around you.”

YPG Testing Focus
The focus of YPG’s portion of the testing is on brownout conditions, which are multi-faceted. Aside from different models of helicopters producing different types and degrees of brownouts, the conditions on a landing zone obscured by standing dust are different than one caused by multiple aircraft landings in short or simultaneous sequence.

“Our focus to this point has been single-ship, but on the sensor side we have looked at multi-ship operations,” said Minor. “Successive aircraft have to go into an area that already has been browned out. We’re looking at the ability of the sensors to see through existing poor conditions to find obstacles.”
YPG’s DVE landing zone (LZ) has multiple tilled lanes meant to maximize the grit and dirt kicked up by a helicopter’s rotor wash, and also includes target areas and obstacles. Flying successive tactical sorties through on multiple days takes a great deal of planning to ensure safety.

“We have a robust obstacle field that the team at YPG has put together that incorporates a number of poles, wires and vehicles, all at different angles and sizes,” said Minor. “Because of the need to detect obstacles inside of a dust cloud, we have Humvees drive into the dusted-out scene to check the radar and sensors’ ability to see an obstacle when already in an obscured environment.”

Every test day, experimental test pilots fly tactically realistic scenarios across the proving ground, utilizing the DVE LZ and various mountain ranges along the way from Laguna Army Airfield. The DVE LZ in particular is a challenge even to the most experienced of these pilots.
“It’s a fairly tight squeeze for a Black Hawk, especially in a degraded visual environment,” said MAJ Mike Osmon, experimental test pilot. “It takes varsity-level moves to land safely.”

In addition to giving reports on their experiences using the system, the pilots can be accompanied by a test observer and a chase helicopter that gathers data during each flight. The effort commonly requires the support of between 20 and 25 personnel. YPG test officers coordinate helicopter re-fueling at the isolated DVE LZ to maximize the testers’ range time and ensure that the wide-ranging missions can take place without interference from other test programs in progress on the range.

“YPG support is amazing,” said Minor. “There is nowhere else we can get the terrain and mission support we get here. Flexibility isn’t enough: you have to be fluid, and YPG has always gone the extra mile accommodating our tests safely within the limits of the test plan.”
“It is a great capability and a great center of hospitality,” agreed Lewis. “The broader Yuma community was very gracious to us as well.”

Mr. Mark A. Schauer is a public affairs specialist and editor of the garrison news publication for Yuma Proving Ground, AZ.

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