. “non-calculation and/or discussion of [the]
crosswind component resulted in continuing the approach in adverse weather conditions;
. “disconnect of the autopilot in the ‘align’ mode under the existing wind conditions
resulted in an out-of-trim condition of the aircraft;
.
“the low altitude of the autopilot disconnect in relation to the existing wind conditions al-lowed the pilot insufficient time to gain com-plete control of the aircraft, which resulted in a hard, traversing landing; [and,]
.
“the hard nosewheel touchdown, exceeding
the certified design limits, resulted in a failure
of the nose-gear [structure].”
Beware Tricky Tail Winds
T
ail winds are especially challenging for con-ducting a stabilized approach. Neither Airbus nor Boeing publish VREF correction factors for tail winds. Because of the increased groundspeed caused by a tail wind, rate of descent must be in-creased to maintain the proper glide path.38
Figure 2 (page 12) shows the rates of descent
required to maintain a three-degree glideslope
at a constant approach speed of 145 knots with tail winds of five knots, 10 knots and 15 knots at
various altitudes. (Wind speed normally decreases with altitude and typically is measured at 33 feet
agl.)
To maintain the proper approach speed while increasing rate of descent, thrust must be reduced. If a go-around is required, precious seconds might be lost as the engines accelerate; the airplane would continue to descend and might touch down on the runway before the engines produce enough thrust to enable a climb.
Jaa and Faa require that the “effects of increased [runway] contact speed must be investigated” only for landings with tail winds exceeding 10 knots.
Several airliners have been certified for operation with a 15-knot tail wind component.
ICAO recommends that the tail wind component,
including gusts, should not exceed five knots on
the designated landing runway. Again, adherence to this recommendation varies among member
states. in the united States, for example, Faa
sets the tail-wind-component limit for clear, dry runways at five knots; the limit increases to seven knots if anemometers are installed near the run-way touchdown zone. FAA allows no tail wind component if the runway is not clear and dry.39
When in Doubt, Go Around
S
everal hard-landing accidents have been at-tributed to the flight crew’s failure to conduct a go-around. Some of the accidents occurred when the approach became unstabilized in the flare.
When is it too late in an approach to conduct a go-around?
“Generally, depending on the airplane model you’re flying, when you deploy the thrust revers-ers or ground spoilers — you’re committed to
land,” Carbaugh said. “Sometimes, a last-second
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