Such are the flights that researchers from UMR's Cloud and Aerosol Sciences Laboratory must endure in order to study aircraft exhaust emissions in the North Atlantic Flight Corridor.

Despite the conditions, Ray Hopkins considers it an honor to be on the specially equipped German Dassault Falcon plane. He's one of only a handful of international researchers who can say, "Been there. Done that."

Based out of Shannon, Ireland, this tour of duty beats the one Hopkins had 26 years ago as a gunship pilot during the Vietnam War. His training there, however, has proven beneficial for his job today as a CASL research engineer at UMR. Nothing shakes him -- even when he's riding in a twin-engine jet just 150 meters behind an European Airbus cruising at 37,000 feet over Germany.

A test flight begins after Hopkins and four other researchers board an already crowded research aircraft. Ducking through a narrow passageway, past a hive of equipment, Hopkins settles into what will be his home for the next four hours -- a small, crowded corner just in front of the plane's restroom. There, he will hover over a computer and a rack of sophisticated equipment to gather aircraft exhaust emissions in the most heavily traveled airways of the world. The data he and other international scientists gather may one day be used to set new emissions standards for aircraft exhaust.

Space aboard the Falcon is at a premium, and scientific equipment takes precedence over human comforts. Cabin temperatures soar as the equipment motors generate heat. Outside the cabin it's -40 degrees Fahrenheit.

Inside, temperatures can reach 90 degrees Fahrenheit. While most passengers would only want to survive such a flight without having to reach for the little white bag, Hopkins must analyze atmospheric particle samples. He probes the outside air and determines the size of the ultrafine particles emitted by aircraft.

"It takes four to six minutes to get one size sweep," Hopkins says. "We look at the size distribution from 10 to 200 nanometers (billionths of a meter). We do as many sweeps as we can because it gives us a profile of the evolution of the particles."

He does take notice, however, when a wing tip catches a wake from a wide-body jet.

"Updrafts, downdrafts and gusts pale in comparison to getting a wing tip caught in the wake of a wide-body jet at 150 meters," Hopkins says.

While right behind a wide-body jet may be an ideal place to gather aircraft exhaust data, it's a risky proposition to fly there. It was especially so the first time, because no one knew for certain if the plane could withstand the air turbulence created by the jet's exhaust. Based on their models, calculations and predictions, the German Aerospace Research Establishment, DLR, determined that the Falcon could safely fly between 50 and 150 meters behind a wide-body jet. Modelers reasoned that a jet's exhaust is like the wake of a boat: to travel immediately behind it would be safer than farther back. They knew, however, that the same aircraft following between a few hundred meters and five miles would be ripped to pieces.

Dr. Jonathan Paladino, a postdoctoral fellow in chemistry at UMR, was on the Falcon the first time it dove behind an Airbus at 150 meters. It was March 1996.

The risks were staggering: The plane's wings could get ripped off. An engine could flame out. Anything was possible.

"I don't remember thinking about what could happen that first time," Paladino says. "If I thought about it, I probably wouldn't have done it." Paladino's confidence in pilot Frank Roessler compensated for the risk factors he faced on this maiden test flight.

"He's an outstanding pilot who has logged thousands of hours in this type of aircraft," Paladino says. Once Roessler announced he was going up into the exhaust plume, silence followed.

"When we first entered the plume, it was like driving down a country road -- it was bumpy, but there were no tremendous jerks," Paladino says.

Data counters shot up.

"The samples saturated our counters," Paladino says. "No one was prepared for the strength of the signals." Nor were they prepared for what happened next.

In a flash, the aircraft flipped to a 60-degree angle.

"We got caught in the jet's vortex, and I was hanging from my seatbelt," Paladino says. "That part was scary, and I was white-knuckled through the rest of the flight."

While the flight was rough, the plane and its passengers stayed intact, and a new era of aircraft exhaust emissions study was born. Paladino, by the way, continues to participate in these flight campaigns.

"We can do all the modeling on Earth that we want, but the only way to prove or disprove these models is to test the actual exhaust," says Dr. Philip Whitefield, associate professor of chemistry and CASL senior investigator, who along with Dr. Donald Hagen, professor of physics and CASL senior investigator, leads this research at UMR. "It is very important for us to go up into the atmosphere to gather the exhaust samples, so that intelligent decisions can be made about aircraft exhaust emission standards."

The international team already has proven that aircraft exhaust emissions can build up in heavily traveled airways, says Hagen. In September, the team took advantage of an occasional atmospheric phenomenon called an anticyclone to study emission buildups. Anticyclones, caused by high-pressure air masses, are ideal for exhaust studies because the same air re-circulates several days over the same area, allowing aircraft emissions to build.

"Every time an aircraft passes through the anticyclone, emissions are added," Hagen says. UMR's preliminary data indicates planes leave behind a trail of sub- micron particles that results in a four-fold increase in an anticyclone over a period of a few days.

UMR's team of researchers will continue to test aircraft exhaust for the foreseeable future. Their research results will be shared by the United States and European nations and are to be included in a United Nations Report, "Aviation and Global Atmosphere," commissioned by the UN's Intergovernmental Panel on Climate Change. The report is scheduled for publication in 1998.

In the meantime, there's no shortage of air travel. Aircraft make up to 2,000 crossings daily in the North Atlantic Flight Corridor between North America and Europe. Unlike the researchers, most passengers on those flights get head room, leg room, reclining seats, magazines, peanuts, flight attendants and comfortable temperatures.

Note: If no author is given, the source is cited instead.

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