David Learmount/LONDON
The Embraer ERJ-145 regional jet has suffered four control emergencies this year in UK airspace, according to the British Civil Aviation Authority (CAA). The pilots had problems controlling the aircraft when the pitch trim appeared to stick, leaving the pilots to counter a strong nose-up pitch force. The UK Air Accident Investigation Branch is investigating the incidents.
In a 7 November incident, an ERJ-145 operated by British Airways franchise partner British Regional Airlines (BRAL), flying a domestic scheduled flight from Belfast International Airport, Northern Ireland, to Manchester, suffered pitch control problems just after take-off, the airline says.
The aircraft adopted a steeper climb angle than normal, but the crew regained control and levelled off at about 11,000ft (3,500m) using elevator. The crew had declared a full "mayday" emergency while still on the Belfast tower frequency, but after levelling out continued to Manchester and made a safe flapless landing. "Mayday" status was not downgraded as control problems persisted throughout.
Similar EMB-145 events recorded this year by the CAA involved two other BRAL flights and a British Midland Commuter flight. There were some related incidents during 1999, the CAA says, but an Embraer-developed modification was supposed to have dealt with the problem.
BRAL says it has found that reducing speed below 370km/h (200kt) enables control to be regained, but says that it is "not sure what is causing [the problem] yet", and it is working with Embraer.
Embraer says that the problem occurs when pilots fail to trim nose-down soon after take-off as the speed increases rapidly. Once above 200kt, says Embraer's director of engineering Jose Renato Melo, the aerodynamic loads on the trim jack get too high for the trim system to work. Reducing the speed below 200kt allows trimming to take place, he says.
Source: Flight International
