Bombardier is replacing fuel-pump couplings in CRJ700 regional jets, after an in-flight failure resulted in uncommanded fuel-transfer from a wing tank, causing the centre tank to overfill. An airworthiness directive (AD) issued last week limits the 70-seater to flights within 1h of an alternative airport until a fix is incorporated.
The Canadian manufacturer has developed a modification, which had been fitted to a third of the fleet as Flight International went to press, with the rest to be retrofitted by the end of March, says CRJ700 programme director Jean-Guy Blondin. The fix involves a redesigned coupling and a stabilising clamp to prevent ejector pump vibration.
On the CRJ700, ejector pumps feed fuel from the wing tanks to the engines via lines which run through the centre tank. When the right coupling failed, fuel was pumped into the centre tank. A boost pump automatically took over feeding the engine.
But pumps intended to transfer fuel from the centre tank to the wing could not keep pace, and the tank overfilled, triggering automatic venting.
Bombardier had prepared a service bulletin for the premature ageing, but did not expect the total disconnection which occurred in February. The fix is an interim step, with supplier Intertechnique working on a solution.
Source: Flight International
