Filing suboptimal plans
Despite all the effort taken to optimise flight plans, there are certain circumstances in which it
is advantageous to file suboptimal plans. In busy airspace with a number of competing
aircraft, the optimum routes and preferred altitudes may be oversubscribed. This problem
can be worse in busy periods, such as when everyone wants to arrive at an airport as soon as
it opens for the day. If all the aircraft file optimal flight plans then to avoid overloading, air
traffic control may refuse permission for some of the flight plans or delay the allocated takeoff
slots. To avoid this a suboptimal flight plan can be filed, asking for an inefficiently low altitude
or a longer, less congested route. [5]
Once airborne, part of the pilot's job is to fly as efficiently as possible so he/she might then try
to convince air traffic control to allow him to fly closer to the optimum route. This might
involve requesting a higher flight level than in the plan or asking for a more direct routing. If
the controller does not immediately agree, it may be possible to re-request occasionally until
they relent. Alternatively, if there has been any bad weather reported in the area, a pilot might
request a climb or turn to avoid weather. As air traffic controllers do not know the precise
location and height of pockets of turbulence, they would not know if the pilot was
exaggerating the problem to get a more efficient route.
Even if the pilot does not manage to revert to the optimal route, the benefits of being allowed
to fly may well outweigh the cost of the suboptimal route.
VFR flights
Although VFR flights often do not require filing a flight plan, a certain amount of flight
planning remains necessary. The captain has to make sure that there will be enough fuel on
board for the trip and sufficient reserve fuel for unforeseen circumstances. Weight and center
of gravity must remain within their limits during the whole flight. The captain must prepare an
alternate flight plan for when landing at the original destination is not possible
A - Z of Flight
July 2017
www.alliance-airways.net
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