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was in the process of making a sharp turn. This can be
explained in part by the power requirements associated
with ramp operations—an aircraft initiating movement
from a full stop requires relatively more power to overcome
inertia and tire friction than an aircraft already in
motion. Additional breakaway thrust is needed if the
aircraft must also turn during the initial movement.
Unless carefully managed, these power applications
can result in jet blast damage.
One reporter described unusually severe damage from
jet blast that occurred during a hard turn, on a congested
ramp not designed for larger aircraft:
✍ “While taxiing out, we were advised by another
aircraft that due to our turn and tailpipe position, his
aircraft had sustained some damage. After calling
Ramp Control, we later learned we had blown out
some terminal windows, knocked over a ramp truck,
put the elevators of two aircraft into the full up
position, and done some damage to miscellaneous air
freight cargo equipment…At departure time, because
of our close proximity to the terminal and the
heavy weight of our aircraft, all engines were started
up at the gate. After the salute, I advanced the
throttles to breakaway thrust, and was directed to
begin a hard right turn to clear another aircraft
parked on our right. Once the aircraft was moving, I
reduced power and concentrated on the signalman.
The ramp at XYZ, like at many small airports, was
not designed to handle LGT [large transport] and
MLG [medium-large transport] sized aircraft. By
attempting to maneuver around without the use of a
tractor or tug, we are compromising safety…We
were fortunate that no one was injured…” (ACN 57960)
Powered 180-degree-or greater turns seemed especially
likely to result in jet blast damage, even when
crews used “normal” or “only necessary” thrust. Several
reports illustrate:
✍ “…A fuel truck refueling an aircraft at an adjacent
gate had a ladder blown off the top…and it
struck the aircraft it was refueling. My taxi out
involved a 180+ degree turn. My use of thrust was
normal…” (ACN 108825)
✍ “…Taxiing requires a hard right 180 turn to get
out of gate. I used power to 3 engines to start
forward, initiated hard right turn, reduced #3 to idle,
and kept power on 1 and 2 to keep aircraft rolling in
the turn. I used only what I felt was necessary to
keep my aircraft rolling. Clearance is tight and I was
concerned about missing poles, building, etc. Captain
of another aircraft immediately to left of our
parking spot complained that his aircraft was damaged
by jet blast.” (ACN 112237)
✍ “…As I turned into “C” area, I realized my assigned
gate was a hard left turn on ramp. We asked
and were cleared by Ground for a 180 degree turn. I
did not see any problem so proceeded to turn left.
Approaching the gate we heard someone on Ground
say that we just blew over a catering truck. I went to
scene and observed truck lying on left side. Truck
was in “raised” mode; no stabilizing “outriggers”
observed; no chocks observed…Damage to parked
aircraft confined to lower portion of left rear entry
door and my ego. Suggestions: all catering trucks
have “stabilizers”; shut down all jet engines when
making turns on ramps (get a tug!).” (ACN 170016)
The corrective suggested by several reporters is to
position jet aircraft so that their forward thrust is
directed away from gate areas, people, and ramp equipment:
✍ “Corrective action: push aircraft back to a position
where initial taxi can be made in a forward
direction.” (ACN 58798)
Positioning is especially critical to safe powerback operations,
which are the turbojet equivalent of “reverse
gear.” In a powerback operation, the flight crew deploys
engine thrust reversers to direct thrust ahead of the
aircraft, thus pushing the aircraft backwards. Concluded
one reporter of a powerback incident that resulted
in jet blast damage:
✍ “This type of damage could be avoided if aircraft
are towed out of congested areas, especially when
situations exist where the possibility of jet blast
damage is high. At a minimum, when powering back,
the aircraft should be directed into a position so that
the aircraft is parallel to the centerline of the taxiway
so that when forward thrust is applied, the jet
blast isn’t directed into the gate area.” (ACN 70969)
　
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