Flying into the largest storms on Earth is all in a day's work for pilots on a NASA mission to explore hurricanes.

by Steve Price and Patrick L. Barry

These unusual aviators endure the dangers of flying through hurricanes in the hope that scientific data they collect will improve hurricane modelling and prediction, which in turn might help save property and lives. Instruments aboard the planes measure temperature, pressure, humidity, precipitation, wind speed, lightning and ice crystal sizes - providing scientists with a hard-won view of the inner workings of a hurricane.

"You pass through this build-up of clouds that literally fills the sky in front of you," said Gordon Fullerton, a highly decorated aviator and former astronaut who pilots a DC-8 aircraft into hurricanes targeted by the CAMEX-4 study.

"Entering the storm, we're faced with rotating bands of thunderstorms as we fly at about 35,000 feet. A hurricane is just a group of thunderstorms circulating around a point called the 'eye.' You can pass through the eye and experience a calm as you observe thunderstorms circling all around you," Fullerton said.

It may be true that the eye of the storm is cloudless and less windy than the rest of the tempest - but only someone like Fullerton with plenty of experience (and perhaps nerves of steel) could feel calm surrounded by most intense thunderstorms in the whole hurricane. It's a dangerous place to fly an airplane!

How do the pilots safely navigate these powerful hazards?

Visit Dommin's photo gallery for more such spectacular views or HurricaneHunters.com to learn more about the daring pilots who pioneered the dangerous art of flying into great storms. This view, looking straight up through the eye of a hurricane, was captured by navigator Scott A. Dommin - one of the US Air Force's famous "Hurricane Hunters."

Simply looking out of the cockpit window is one way. Because a hurricane is a collection of thunderstorms, pilots can often visually spot the stronger storms and simply avoid them. For example, says Fullerton, "If I see a thunderstorm that climbs up to 60,000 ft., I can tell by its thickness and blackness that I don't want to go in there."

Clouds can make such visual spotting difficult, however. "If we encounter a lot of cirrus clouds, we're stuck with just the radar," Fullerton said. The DC-8 pilots can direct their Doppler radar's up and down the storm scanning for trouble.

"These storms can be very rough," Fullerton said. "We can experience strong turbulence as well as rapid accumulation of ice crystals, something scientists call 'graupel.' And large hailstones can terribly damage the aircraft."

"It's also noisy," he added. "All the precipitation begins pounding on the windshield. It compares with driving your car fast through a heavy thunderstorm, with the difference being we're above 30,000 ft."

The pilots sometimes pass through strong vertical winds that accelerate the plane downward and then upward. These intense gusts can toss the pilots "up against their straps."

Image courtesy NOAA. Hurricanes form as warm, humid air rises, causing the moisture to condense out, which releases heat into the air and causes it to rise still faster in an accelerating cycle. This forms the tall, billowing thunderstorms and also leaves an area of low pressure near the surface. Surrounding air is drawn toward this low pressure, spiralling in toward the centre due to the Coriolis effect. The rising air also creates a high-pressure area at high altitude, which causes an outward spiralling of clouds high above the main storm clouds.

"Depending on the level of turbulence, it can be structurally significant to the airplane," said Fullerton, who said the heavier turbulence can surprise even seasoned pilots. "When you reach turbulence and the coffee flies out of your cup.... [well,] that's when we turn the aircraft toward an area where radar indicates the conditions are better."

Encountering a severe storm within a hurricane can be quite an experience!

While Fullerton's DC-8 ventures into the storm, ER-2 pilots fly high above it - at the very edge of space! The ER-2, a civilian version of the U-2 military spy plane, soars to 60,000 feet where instruments can record both the height and girth of the storm.

"One of the reasons that the ER-2 is such a unique platform is the instruments are basically the same as on the satellites in outer space," said Jan Nystrom, an ER-2 pilot with Lockheed. Only the ER-2 is much closer to the storm than orbiting satellites. "We are the close-up lens."

The view from the dizzying height of 60,000 ft. is "definitely something you're not used to. We're kind of in the twilight zone there," he laughed. "The sky above you is much darker because we are above about 90 to 95 percent of the Earth's atmosphere."

From their high perch, ER-2 pilots get a different view of the hurricane's eye than the DC-8 crew.

NASA's ER-2 research aircraft is an elegant-looking plane, and its resemblance to the famous U-2 is no coincidence - the ER-2 is a civilian version of the military spy plane. [more]

"Depending on how well-defined the eye of the hurricane is, you can sometimes look down all the way through the storm and see blue water," Nystrom said.

A single pilot flies the ER-2 aircraft, which is 63 ft. long with a wingspan of 104 ft. These long, thin wings give the plane a maximum altitude of about 65,000 ft., and its light weight enables it to have a range of 3,000 nautical miles (about 3,452 miles or 5,555 km).

"It really amounts to a high-altitude jet glider," said Larry Montoya, mission manager for the ER-2.

All pilots flying the ER-2 missions received previous experience with the aircraft during stints with the military. These aviators are well aware of the dangers involved and actually are outfitted with spacesuits just like the astronauts use.

Image courtesy NASA's Dryden Flight Research Centre NASA's DC-8 research aircraft may look like a commercial airliner from the outside, but the inside is a different story! The interior of the plane has been converted into a flying laboratory filled with data-gathering scientific equipment. With the lives of the scientists who operate the instruments also at stake, the DC-8 pilots must be extra-cautious.

The cabin is pressurised to about 28,000 ft.," said Nystrom. "However, if we should lose cabin pressure for any variety of reasons, then the pressure would drop to ambient pressure. If we didn't have that suit to protect us, our blood would boil .... it would be fatal."

The majority of these missions are flown high above the destruction the storm unleashes at ground level, but the storms right around the eye can sometimes extend all the way up to the altitudes where the ER-2 flies. "When we experience moderate to strong turbulence, we tend to get away from that," Nystrom said.

Mission rules are followed closely, especially regarding turbulence, where pilots are instructed to escape the area before the situation gets out of hand.

"These rules are driven, basically, by the capabilities of the airplane," Montoya said. It's a situation where following the rules is very important! With the proper caution and equipment, these skilful pilots are able to do their seemingly treacherous jobs safely, collecting vital data from inside the largest storms on Earth.