for heavy maintenance. And since the aircraft types arriving for
line maintenance can’t be predicted, those workdocks would
often be useless. But you need quick access to all parts of the
aircraft. The solution is some combination of portable lifts, air
stairs, and, in very high volume operations, teleplatforms.
Varying Airframes Require Open Space
Third-party maintenance providers also usually need long-span, flexible hangar space even for heavy maintenance. Those
companies don’t have a defined fleet like an airline. They see a
wide variety of airframes and must maintain flexible space and
equipment to densely pack aircraft at odd angles and shorter
clearances. Portable equipment also provides the flexibility to
mate to those oddly parked and densely packed aircraft. But
those facilities sacrifice some efficiency for the flexibility to
service the full range of airframes.
The airline heavy maintenance mission is much different in turn
times, scope and intensity of work. Fleet mix is well-defined.
Aircraft dwell times are measured in tens of days. The aircraft
is disassembled, placed on jacks and left open for maintenance
access. Efficiency is gained by using work docks that mate
to the aircraft to provide access to all areas of the aircraft
simultaneously. Those work docks define the hangar bay size,
so extra space doesn’t add efficiency.
Hangar spans can be reduced to what is needed for a single
aircraft surrounded by work docks. The bridge cranes and
some work docks suspended from the roof structure are
heavy, so shorter spans save roof structure cost. Further
efficiency is gained by customizing the hangar bay for the
airframe type. The general division is wide-body and narrow-body dedicated bays, although new super-wide-body aircraft,
such as the Airbus A380 and B747-8, create a new hangar
class for those largest aircraft.
Know Your Needs
The key to balancing hangar flexibility and efficiency in
aircraft maintenance is to define the maintenance mission
and provide the hangar bay design that best meets that
mission. In general, use long spans for line maintenance and
short spans for heavy maintenance. Study the maintenance
needs — line versus heavy — carefully, and assess the
fleet size and mix, the availability of land and funding,
and the needed efficiency before deciding on a large,