RUNWAY EXCURSIONS - Cross Wind as a Factor in Runway Excursions - Runway excursions on takeoff, where the cross wind has been a significant factor, usually identify one or more factors: inappropriate flight crew decision to attempt a takeoff; inappropriate flight crew aircraft handling;•high rates of variation in surface and near-surface wind velocity; inadequate availability of information about the state of the runway surface; and incomplete understanding by flight crew of the aircraft performance limitations or recommendations in relation to cross wind takeoffs

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Runway Excursions

Cross Wind as a Factor in Runway Excursions

Investigation of Runway Excursions on takeoff, where the cross wind has been a significant factor, usually identify one or more of the following factors:

·       Inappropriate flight crew decision to attempt a takeoff

The origin of such a decision usually lies in poor Crew Resource Management.

Sometimes this relates to the ‘original’ decision to commence preparation for departure which later becomes clearly questionable but is not effectively reviewed.

Both Operator Culture and Authority Gradients between flight crew members can play a role in this scenario.

·       Inappropriate flight crew aircraft handling

This may arise directly from poor skills, especially where the simulator training for the aircraft type is carried out in devices which cannot realistically replicate low level wind velocity.

It may be related to insufficient understanding of the ‘basic theory’ of directional control during takeoff, or it may be related to the use of inappropriate, or possibly unapproved or non-recommended techniques for aircraft control during acceleration to takeoff speed.

·       High rates of variation in surface and near-surface wind velocity

Gusty wind, variable wind direction or wind that is intermittently blocked by airport structures or terrain features can make directional control during the takeoff run more difficult.

·       Inadequate availability of information about the state of the runway surface

When a runway is declared to be contaminated, there are clearly specified processes for measuring and communicating surface friction.

A reduction in friction index or braking action normally correlates to a reduced maximum allowable cross wind value and the reduction mat be considerable.

The modified cross wind takeoff limitations or recommendations should be published in the Aircraft Flight Manual (AFM) or the Operations Manual.

·       Incomplete understanding by flight crew of the aircraft performance limitations or recommendations in relation to cross wind takeoffs

Aircraft limitations for dry runway operations can be expected to be unequivocal in their specification and may be qualified by runway width.

By contrast, the limitations or recommendations for runways which are not dry may be difficult for flight crew to apply on the basis of the information they have on runway surface condition and cross wind component at any point in time. It is important that flight crew have clear Operations

Manual guidance on restrictions to dry runway crosswind limitations and any necessary clarification on how to interpret the guidance material for wet or contaminated surfaces.

https://www.skybrary.aero/index.php/Cross_Wind_Takeoff_Hazards_and_Techniques