Volume 6, Number 3, 1997

At the edge of the envelope

At the edge of the envelopehe line separating success and failure is pretty well marked when you're an experimental flight test engineer for the U.S. Air Force. That's one of the reasons why Dan Sheridan, EG '87, says he loves his job.

Most Americans can vividly recall the rockets that lit up the night skies over Baghdad during the 1991 Gulf War. Sheridan's mission includes the testing and evaluation of such leading edge, non-nuclear weaponry.

"We insure that weapon systems are built as designed and that they will meet the warfighters' requirements," says Sheridan. "Last summer, we received an urgent request for a previously untested aircraft and missile combination. We completed that testing in 28 days, start to stop. The result was immediately put into action."

Born in San Antonio, Sheridan lived for 12 years in Houston, during the glory years of the Apollo space program.

On several visits to the Johnson Space Center, he says he was fascinated with the wonders of space and the lure of flying.

His family moved to Doylestown, Pa., where he attended Central Bucks High School West and became a student government leader and first chair trombonist playing in concert, jazz bands and orchestras around the region. Sheridan also wound up with a choice of two ROTC scholarships-Navy or Air Force.

"I chose the Air Force since it supported my interest in aviation," says Sheridan. "By then, I realized my eyesight wouldn't allow me to qualify as a pilot, but I knew I could still become involved in flight test programs as an engineer."

At UD, he enrolled in the Honors Program, graduating with a degree in electrical engineering. Sheridan entered active duty in 1988 and was assigned to a program that provided the first-ever combat capability for F-16 aircraft with advanced, medium-range, air-to-air missiles.

"I learned a great deal about managing test flights and about the Department of Defense at the F-16 program office," says Sheridan, who lives in Crestview, Fla., with his wife, Gail, and young son, Daniel. "That experience, along with my engineering background, enabled me to compete for a flight test engineer program. I was one of 18 engineers selected out of several hundred candidates."

After qualifying, Sheridan was given responsibility for all aspects of the development and testing for the B-1B Bomber. Two years later, he attended the Defense Systems Management College in Virginia.

In May 1996, Sheridan was assigned to his current position, where he is responsible for the planning, execution and reporting of all air-to-air missile test programs, including the AMRAAM, AIM-9X Sidewinder and the ASRAAM (Advanced Short-Range Air-to-Air Missile). He also is able to pursue his love of flying as airborne test conductor for the safe separation test.

"As test conductor, my main job is to direct and control the pace of the test mission, and, on a given day and mission, I direct the activities of the test pilots, project engineers, range safety office and aircraft controllers, all on a real-time basis. Believe me, there's a lot going on.

"We evaluate the separate characteristics of the missile as it's launched or ejected from an aircraft," he explains.

"Of particular concern is the missile's behavior as it passes through the plane's flow field. We must define a safe separation flight envelope, in which the missile can be employed without contacting or colliding with the launching aircraft."

Typically, the testing is done over the Gulf of Mexico at the "edge of the envelope," a flight regime where the aircraft and missile will undergo the greatest amount of aerodynamic stress under dynamic flight conditions. "It's your basic worst-case scenario," explains Sheridan.

Although the flight test engineer's creed is "plan to fly and fly the plan," things rarely go as planned, Sheridan says. "Nothing's routine. Nothing ever happens the same way. You're just waiting to see what happens next," he says.

"The most dynamic testing in which I've flown is the compatibility flight profile in which we conduct a three- to four-hour test mission at the edge of the envelope," says Sheridan. "We execute high 'g' maneuvers to assess the handling characteristics and structural integrity of the aircraft and missile. It's a shake-out."

[A "g" is a unit of force equal to the force exerted by gravity on a body at rest and used to indicate the force to which a body is subjected when accelerated.]

Although the work is physically demanding at times, Sheridan compares this type of testing to training for a sport. "The more you do it, the more you build your 'g' tolerance."

"I guess I'm living my boyhood dream. I'm very comfortable flying, and I love the dynamics and leading edge of flight test," he says.

Sheridan is stationed at Eglin Air Force Base, the world's largest military installation, located in the panhandle of Florida. There, he says, "We've accomplished over 250 live missile launches of various types, ranging from safe separation missiles to guided missiles with live warheads. It's extremely exciting to be on the leading edge of technology and to see the weapon systems we may use in combat."

Sheridan continues to pursue his dreams. He recently submitted an application to NASA to compete for the astronaut candidate program. If selected, he will enter astronaut training as a mission specialist.

-Terry Conway