Recent addition to our manual, hope it sheds some light,
Recommended crosswind technique during takeoff
At regular intervals we receive questions concerning the correct technique for crosswind takeoffs. Especially the
text concerning “large control wheel inputs” in FCTM 3.12 leaves room for interpretation.
In this Plane Fact we will look into the effect of raised flight spoilers during the takeoff roll and the allowance for
flight spoiler deployment in the takeoff performance calculation. The following information is compiled from
information we received from Boeing.
In FCTM 3.12 guidelines are given for crosswind takeoffs. The following quotes are relevant for the preferred
takeoff technique:
“Throughout the takeoff roll, gradually increase control wheel displacement into the wind only enough to
maintain approximately wings level”
"Large control wheel inputs can have an adverse effect on directional control near V1(MCG) due to the
additional drag of the extended spoilers."
“Note: Excessive control wheel displacement during rotation and liftoff increases spoiler deployment. As
spoiler deployment increases, drag increases and lift is reduced which results in reduced tail clearance, a
longer takeoff roll, and slower airplane acceleration."
Relevant for the understanding of the FCTM text is the fact that drag caused by excessive spoiler deflection can
only be limiting when the takeoff is continued after V1 with an engine failure or a loss of thrust. Excessive
spoiler deflection during a normal two-engine takeoff will lead to reduced tail clearance, a longer takeoff roll
and slower airplane acceleration, but the impact on performance will be negligible compared to a takeoff with
an engine failure.
An engine failure during the takeoff roll will cause extra drag due to required rudder and aileron inputs. Boeing
states it to be impossible to define what "large control wheel input" or "excessive control wheel input" values
are since conditions and speeds will vary. Boeing advises to use enough control wheel input to keep the airplane
on centerline with approximately wings level. Any input beyond that would be considered 'excessive'.
The FCTM technique of using only enough control wheel inputs to maintain wings level will minimize the
performance impact of spoiler deflection during the takeoff roll, and immediately following liftoff. Boeing did a
study of the effect of crosswind on takeoff roll and concluded that the drag effects of extended spoilers on the
upwind wing are offset by the positive effect of the crosswind on the same wing. In other words; the airflow to
the upwind wing is at a higher speed than the actual measured airspeed because the lateral component of the
wind is bigger at the wing. The resulting increase of lift counteracts the effect of the increased drag. As a result
the correct use of control wheel inputs (including flight spoiler deployment) will not have a negative effect on
takeoff performance calculations.
The technique to gradually increase control wheel displacement into the wind only enough to maintain
approximately wings level should not be limited to a certain maximum. Boeing does not recommend setting
limits to control wheel roll inputs on takeoff as crews must be ready to apply as much correction as necessary in
the event of takeoff upset events such as strong gusts or wake turbulence encounters.
The correct application of con