Gate Delays

Question:   When do you start the engines, and how
long does it take to start both?  Is this the
cause of the short wait after pushback?
Brad Kwest
Denver, Colorado

Answer:
The B-777 is the one airplane I know capable of
starting both engines at once, which was a real
pleasure when I was flying this aircraft.  On
other airplanes, we may start one, commence the
taxi and then start the second one, but if both
are started at the gate it just takes about
another minute or two after the first to start
the second.  At times, the second engine may be
started while the first one is still getting
cranked up.

Some planes, such as the Airbus 319/320, have a
tendency toward hot brakes.  If we taxi out to a
distant runway with both engines running, we're
going to need to brake enough to possibly cause
the brakes to heat up too much.  So, depending
upon weather conditions, whether the airplane has
already flown and the brakes already warm and a
few other factors, we make the decision whether
to taxi out on one engine or both.

On the B-727, which I flew in the 90's, we'd
often start engines one and three at the gate
(left and right engines), then start #2 on the
way out somewhere.  That was mostly to get out of
the gate a little more quickly and also to help
conserve fuel.  The start of each flight there
are several factors considered with regard to how
many engines we have going when we leave the
gate.

To answer your question more directly, the delay
you sometimes experience at the gate is more
likely to be the delay while we wait for the
ground personnel disconnect us from the tug, and
for us to get clearance from the ramp tower to
begin our taxi.  We also have a few checklist
items to accomplish just after engine start.
During times of really heavy traffic, it might
take several minutes to start our taxi while we
wait for traffic behind us to clear out.  Ramp
control keeps us advised and gives us clearance
when they can, but interestingly enough we can
often see behind us and can at times anticipate
when our clearance will come.  How (you ask)?
Because of the reflection in the glass of the
terminal.  It's really quite handy.  Check out
our reflection in the terminal glass at Osaka,
Japan:
Terminal At Osaka

By the way, if you look at the photo in the above
link you'll see a "9" and a series of numbers
beneath it.  We're at Gate 9 in Osaka and those
are the coordinates beneath it--the latitude
longitude--which we enter into our GPS's.  Just
in case you were wondering.

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