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U.S. Navy E-2C Hawkeye
U.S. Navy E-2C HawkeyeA U.S. Navy E-2C Hawkeye, a carrier-based electronics platform that serves as the eyes and ears of carrier battle groups, arrived at Dryden recently from its base at the Naval Air Warfare Center Aircraft Division at Patuxent River, Md.

A U.S. Navy E-2C Hawkeye recently arrived for tests in the Dryden Loads Laboratory, where loads equations will be developed to assist the Navy in determining how the aircraft will respond to the added weight of planned modifications. NASA Photo by Tony Landis

The Hawkeye, distinctive with its 24-foot diameter rotating radome, is part of a fleet of aircraft that has been operational for more than 30 years and is about to undergo modifications that will add weight to the aircraft. Navy officials have asked Dryden to help formulate loads equations aimed at determining how the additional weight will affect the aircraft's flight envelope.

A C-130 arrived in advance of the Hawkeye to deliver tools and aircraft support hardware such as aircraft jacks, necessary for the Dryden Loads Laboratory work, which will take until next summer to complete.

A Navy crew will need two to three weeks to prepare the aircraft in Dryden's Research Aircraft Integration Facility, removing engines and purging fuel tanks. As many as eight Navy representatives will be at the Center during the Hawkeye tests.

Essentially, the test series will apply force, or loads, on the aircraft to develop loads equations, said Paul Lundstrom, Dryden's E-2C lead test engineer. To complete this task, Loads Laboratory researchers will use a data-recovery system connected to instrumentation on the airplane.

"We read and record what those instruments are telling us," Lundstrom said. "That data is used to develop what we call loads equations. This is similar to what we did with AAW (the Active Aeroelastic Wing testbed). We give (Navy technicians) loads equations that can be used to estimate loads while they're flying the airplane. This allows them to know when they're approaching loads that are too high for the structural capacity of the aircraft. It helps them define the flight envelope. You can only turn so fast at so many (g-forces). You can only dive so hard. You can only fly this turn at this altitude at this airspeed. It has to do with defining the performance parameters of the aircraft while maintaining a safe structure."

The E-2C research isn't the biggest project completed in the Loads Laboratory, but it is among the largest ever undertaken and could lead to similar work in the future, he added.

An unmodified E-2C weighs about 39,561 pounds. The Hawkeye at Dryden will have its weight beefed up with metal plates to simulate 42,061 pounds - mimicking the latest weight configuration of the upgraded Hawkeye, which also is known as the E-2C+, or Hummer. Loads will be applied to the aircraft's wings and tail. The testbed has an 80-foot wingspan and is about 58 feet long and 18 feet tall. The Loads Laboratory can accommodate the aircraft with room to spare for equipment and fixtures necessary for conducting the research.

In preparation for the aircraft's arrival, a team of Dryden researchers met several times to discuss the schedule and scope of work to be performed. Step-by-step procedures are being developed for each project task, and responsible parties identified for each.

Dryden personnel will install and monitor the 224 strain gauges, which measure stress on the aircraft's surface, and 15 string pots, which essentially are electronic measuring tapes. Six load cells will measure aircraft reactions at fixed points on the ground. An additional 24 load cells (instrumentation that records how large a force is being applied to an area) are used for loading the wings and eight for the tail.

Lundstrom said the biggest challenge for the Dryden team is adhering to a schedule he described as tight, for a test of this size and scale. "Our task is to find a way to get everything finished in time to support the Navy's completion date," he said.

Dryden researchers will see benefits from this project, he added.

"Every airplane you test, I think you learn something from it, because every airplane is different," he said. "In this case, one thing we'll learn is how to push on an airplane that has a very thin skin on the wings."

This work also could represent new opportunities for Dryden.

"It represents a new line of business that we hope to cultivate," he said. The E-2A Hawkeye first entered service in 1961, was updated in 1969 as the E-2B and the E-2C was introduced in 1973. The Hawkeye engages in missions similar to those of the Air Force E-3 Airborne Warning and Control System aircraft, also known as AWACS.

The Navy's Hawkeye, which was built by Northrop Grumman, has extensive communication and long-range surveillance radar capabilities. It is considered the "quarterback" - or manager - of carrier-group operations, and boasts the ability to monitor six million cubic miles of airspace and more than 150,000 square miles of ocean surface while detecting hundreds of ships, aircraft, missiles, or targets up to 200 miles away.

+ E-2C Hawkeye X-Press story

+ View Volume 46, Issue 9, October 2004 Dryden X-Press

+ View current headline stories

Jay Levine
NASA Dryden Flight Research Center