On 28 November 2005, a Dornier 328 (D-CPRW) being operated by Austrian-registered operator EuroManx on a scheduled passenger service departing from the Isle of Man to an unrecorded destination in day VMC was unable to rotate at the speed calculated as applicable and the takeoff was successfully rejected.
A Field Investigation was carried out by the UK AAIB. It was noted that the 53 year-old Captain, who had been PF for the flight had accumulated a total of 5,575 flying hours including 310 hours on type and that the First Officer had accumulated a total of 1,305 flying hours including 63 hours on type, having passed his Final Line Check the previous day to complete type conversion training.
It was established that although icing conditions were not present, because of significant frost deposits on the airframe, the aircraft had been de iced with a heated mixture of 75% Type II+ fluid and 25% water prior to departure. A Flap 12 takeoff was briefed with a V1/Vr of 109 KIAS. The aircraft commander, subsequently found that when he attempted to move the control column aft to initiate rotation, the aircraft did not respond and so the takeoff was rejected.
The Investigation found that regardless of whether or not icing conditions were present, the Aircraft Flight Manual (AFM) requirement was for specified higher takeoff speeds to be used a departing aircraft had been ground de/anti-iced. The correct V1/Vr in this case was the “icing” Vo/Vr of 128 KIAS. Both pilots had recently completed their type rating training with different Type Rating Training Organisations and both had then completed their line training with the Operator. They had been provided with an easy reference chart shoeing normal takeoff speeds but neither pilot was aware of the AFM requirement under ‘Normal Procedures’ to use icing takeoff speeds in non-icing conditions following the application of thickened fluids, for which there was no corresponding reference in the Company Operations Manual.
The Investigation noted that V1/Vr speeds for icing conditions in the Do 328 AFM are typically around 20 knots higher than those for non-icing conditions. And that such a large increase is not unusual for turbo-prop aircraft such as the Dornier 328 that are fitted with de-icing, but not anti‑icing, systems.
The Conclusion of the Investigation was formally stated as follows:
“The probable cause of the incident was the incorrect V1/Vr speed selected. Had the correct V1/Vr speed been selected then the effects of any contamination of the horizontal stabiliser and elevator undersurfaces with thickened fluid would probably have been negated by the increased airflow and fluid run-off. Had the contamination been untreated frost, it is possible that the aircraft may not have rotated normally, even at the higher rotation speed. Contamination must have been present because the aircraft would not rotate at the ‘normal’ rotation speed for its configuration and load but it was not possible to determine whether the contaminant was ice or thickened fluid. However, the de-icing/anti-icing fluid streak marks on the lower surface of the horizontal tailplane surfaces suggested that little or no fluid had been applied to the leading edge of the horizontal tailplane lower surfaces. This may have occurred because the fluid was sprayed from the trailing edge towards the leading edge instead of the recommended method of spraying from the leading edge towards the trailing edge.”
During the Investigation, the Operator issued a ‘Notice to Aircrew’ to all pilots on their Dornier 328 fleet to which was attached the relevant extract from the AFM. This advised that "If the aeroplane is treated with de/anti-icing fluids, irrespective of ambient conditions or temperatures and even if non-icing conditions exist: V1, Vr, V2 and Vsec with horn heat on and related takeoff performance for icing conditions MUST be used” (Vsec = speed for single-engined climb)."
Two Safety Recommendations were made as a result of the Investigation as follows:
- that the Joint Aviation Authorities should contact all Dornier 328 Type Rating Training Organisations within JAA member States and emphasise the need to train pilots to use icing speeds following de-icing/anti-icing with thickened fluids, even when in non-icing conditions.
- that EuroManx should provide annual pre-winter flying awareness refresher training and information to all its flight crews. This refresher training should emphasise the need to use the correct icing speeds even in non icing conditions.
The [Final Report] of the Investigation was published on 5 October 2006.