Description

On 17 January 2007, a Bombardier CRJ 100 being operated by French airline Brit Air on a scheduled night passenger flight from Paris CDG to Southampton could not be directionally controlled after touchdown on a dry surface in normal visibility and almost calm winds and departed the side of the runway during the landing roll. There were no injuries to any of the 36 occupants and there was no damage to the aircraft.

Investigation

An Investigation was carried out by the UK AAIB. It was established that with the First Officer as PF, the aircraft had suffered a failure of the No 3 hydraulic system when the landing gear had been selected down on approach at about 6 nm - approximately 2 minutes - from touchdown. The aircraft commander had then taken what he believed to be the necessary actions prior to landing but “without apparent reference to the QRH”.

As a direct consequence of this, the aircraft landed with one of the No 3 hydraulic system pumps still running and the nosewheel steering on, which was contrary to the relevant drill given in the QRH for the malfunction experienced. This resulted in an uncommanded steering input to the right which became apparent at about 70 knots, shortly before the First Officer would have been expecting to pass control to the aircraft commander because there was only one steering tiller fitted to the aircraft. The steering input could not be corrected and the aircraft departed the from right hand side of the runway and travelled 61 metres across a level grass surface separating the airport apron from the runway before coming to a stop 34 metres from the runway centreline. The passengers were subsequently disembarked using the aircraft steps and transferred to the terminal by bus.

Although the landing gear, brake units and the fans and intakes of both engines were found to be contaminated by mud, more detailed examination did not disclose any damage.

It was noted that, following the initial response to the indication of a hydraulic malfunction, the First Officer had “advised the commander that they would have reduced braking and no steering, and asked him if it was not better to divert to London” and the commander had restated “that they would continue with the landing and request a tow if it became necessary”. It was also noted that “whilst there was, in fact, sufficient landing distance available for landing with the malfunction present, “the CVR gave no indication that such a calculation was carried out by the crew prior to landing”.

Whilst noting that the correct actioning of the appropriate QRH drill would have prevented the accident, the investigation considered that “there remains the possibility that, in another case, a hydraulic failure could occur just before touchdown. In such a case it would be unreasonable to expect a crew to take the appropriate actions quickly enough to prevent a similar lack of controllability on the ground”.

The cause of the hydraulic failure was identified as a leak at the outlet of hydraulic pump 3A at the elbow joint where an ‘O’ ring had ruptured in a way that appeared consistent with a rapid loss of fluid. It was found that a locking wire was missing between the pump and the elbow fitting and it was considered that either this, or the incorrect installation of the ‘O’ ring, was probably the origin of failure.

One Safety Recommendation was made:

• That Bombardier Aerospace review this design of nose gear steering system, in the CRJ100 and other company products, to prevent uncommanded nose gear steering following a hydraulic failure. (2007-101)

The Final Report of the Investigation was published on 7 February 2008 and may be seen in full at SKYbrary bookshelf: AAIB Bulletin: 2/2008 EW/C2007/01/02

Further Reading

• Runway Excursion
• Deceleration on the Runway
• Runway Overrun On Landing (OGHFA SE)
• Maintenance Error