THE US NAVY HAS begun flight-testing a Grumman F-14D equipped with a digital flight-control system (DFCS) designed to prevent flat spins and improve carrier-approach handling qualities.

The 1.3h first flight on 14 July demonstrated safe operation of the system in clean and landing configurations, the Navy says.

Carrier-landing mishaps and departures from controlled flight during high angle-of-attack (AoA) air-combat manoeuvring have resulted in the loss of some 20-25 aircraft, says Navy F-14 programme manager Capt. Richard Evert.

Excessive yaw rates can be generated rapidly during high-energy departures. Yaw rates reaching 70¡/s in 3s have been observed, and sustained yaw rates of 180¡/s are common in fully developed flat spins, the USN says.

In the clean configuration, at low airspeed and high AoA, the DFCS reduces pilot control inputs, slowing aircraft response, and giving the crew more time to recognise and counteract the impending spin.

The F-14 is more difficult than other Navy fighters to land aboard carriers. In the power-approach configuration, with the gear and flaps down, Dutch roll causes the F-14's nose to yaw in response to roll inputs, making it difficult to line up with the carrier, Evert says.

The DFCS includes a lateral stick-to-rudder interconnect to improve handling qualities and reduce pilot workload during the approach and landing.

The DFCS has been developed by Northrop Grumman, GEC-Marconi Avionics and the US Navy, and replaces the F-14's analogue stability-augmentation system.

A budget request for less than $80 million to retrofit the DFCS to 251 F-14s was rejected by the US Department of Defense in 1994, but Congress voted funds for the flight tests.

Funding is available for only 20 of the required 30-50 test flights. These, are expected to be completed in August, after which, the USN will decide whether to proceed with the programme.

Source: Flight International