Flight tests of 737-700 AEW&C aircraft prove successful following change to Northrop Grumman MESA antenna
Flight tests of the Boeing 737-700 airborne early warning and control (AEW&C) aircraft have resumed after modifications were completed to improve the performance of its Northrop Grumman multirole electronically scanned array (MESA) antenna. Boeing says the modification involved raising the upper surface of the flat-topped "top hat" antenna by around 100mm. The 10.7m (35.5ft) -long unit, mounted on top of a support structure on the upper aft fuselage, is now increased in depth to around 0.5m.
Boeing says the decision to raise the "top hat" was taken after a cost-benefit analysis showed the performance improvements "far outweighed" any potential disruption to the test and development schedule. By raising the top hat, the space between the radiating elements and the radome is increased, reducing interactions between the two and "gaining a substantial increase in performance", it says.
The redesign also "increases the margins we need to allow for normal uncertainties when detecting targets", at the cost of a "relatively minimum change to the outside", says Boeing.
Although some tests such as bird and hail impacts had to be rerun with the modified shape, Boeing says the airworthiness tests that restarted around 26 January showed no impact on cruise performance. Despite spending around one month undergoing the modification, Boeing says the schedule for air vehicle 1 (YG201) is virtually unaffected because of the "substantial test contingency" time built into the programme.
The aircraft is expected to complete airworthiness tests by the end of March, including crosswind and natural icing tests that will occur as soon as weather conditions permit. "Between now and April" the aircraft will also be flown to Victorville, California to undergo high-power electromagnetic interference tests originally set for last December. The company made "a conscious decision to defer that until we had the right radome", it adds.
The second test aircraft, which will be the first to be equipped with a fully operational radar and the rest of the mission system installed, is scheduled to make its first flight on 16 May, two weeks ahead of schedule, says Boeing. The two aircraft are to undergo production acceptance tests in 2006, culminating in operational utility demonstrations in Australia and the USA, before delivery to the Royal Australian Air Force in November 2006.
*Northrop Grumman has announced a $42 million fourth quarter charge to cover the expense of "redesign and retrofit of antenna elements" for the Wedgetail project.
GUY NORRIS / LOS ANGELES
Source: Flight International
