Andrzej Jeziorski/MUNICH

FAILURE TO TELL the pilot of critical changes to the aircraft led to the loss of a Rockwell/Daimler-Benz Aerospace (DASA) X-31 in a crash on 19 January, say sources close to the project.

Test pilot Karl Lang, is believed to have been insufficiently briefed before the test flight, which led to the loss of first of two prototype aircraft.

The Rockwell/ DASA X-31A enhanced fighter- manoeuvrability aircraft was destroyed, following a loss of control which was triggered by pitot icing, while the aircraft was returning to Dryden Flight Research Center, California, after a series of test manoeuvres.

Programme sources say that the pilot-heating system had been disconnected because of adjustments being made to the pitot system intended to give better readings at high angles of attack. Lang was reportedly not told about this during the pre-flight briefing, nor when he radioed in with anomalous instrument readings, which were then followed by increasing pitch oscillations and a violent roll before he decided to eject.

If Lang had known about the heating system, he could have switched to a back-up instrument mode and landed normally, says one source.

The accident came as the $250 million X-31 programme was entering its final stages, having exceeded its goals in investigating thrust vectoring as a boost to fighter manoeuvrability. The partners are still campaigning to obtain funding for a follow-on programme.

The second prototype X-31A arrived at DASA's Manching site, in southern Germany on 23 May, to prepare for its appearance at the Paris air show at Le Bourget, in June. The aircraft was flown in on a Lockheed C-5 Galaxy transport, and was due to have been re-assembled in time to start flying in Germany before the end of May. DASA says that the display flight in Paris will include a demonstration of the aircraft's post-stall flight capability.

Source: Flight International