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For medium/long-haul pressurized airliners that are used on short routes.

How is a cycle calculated?

Wouldn't the short flights impact the maintenance schedule due to the frequency of pressurization cycles?

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  • $\begingroup$ You may consider several parameters to define a cycle, some of which only occur at take off and landing (landing gear touch down effects on wheels --rotation, break--, engine full thrust, engine start up,...) other only when transitionning from ground level to cruise level (pressurisation, flaps operation, engine at climb thrust for several minutes,...) $\endgroup$ – Manu H Sep 22 '16 at 9:51
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    $\begingroup$ What do you define as a cycle? $\endgroup$ – Notts90 Sep 22 '16 at 11:27
  • $\begingroup$ This question cannot be properly answered unless the type of cycle is defined. Different aircraft have different cycle definitions, including engine starts, pressurization, and wheels up/down. Our operation determines cycles based on engine starts, not pressurization, since engine starts are what our maintenance ops are most concerned about. $\endgroup$ – J Walters Sep 22 '16 at 13:14
  • $\begingroup$ If you are talking about a flight cycle, then yes, this does increase maintenance costs. The Zero-G Airbus considers each parabola a cycle for the aircraft and engines and greatly increases maintenance and operation costs. $\endgroup$ – Ron Beyer Sep 22 '16 at 14:02
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Much of the wear on an engine happens during startup, so while yes it does have a significant impact on maintenance costs, it's rather unavoidable unless the operator chooses to avoid shutdown between flights (as some do, e.g. skydiving and ag spraying)

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A cycle is mainly based on the pressurization and depressurization of the cabin, during these stages the diameter of the fuselage increases and decreases (pressurization, increase in diameter, depressurization, decrease in diameter). The causes fatigue stresses in the material. For the fatigue it is less of an issue what the duration is of the cycle.

For the engines, before takeoff the engines need to reach operation temperature (about 3 minutes after start or faster for newer engines )For the engines the same hold as for the fuselage but here the temperature is responsible for expanding and shrinking of parts.

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  • $\begingroup$ A cycle is not necessarily a pressurization cycle. Cycle has multiple meanings. $\endgroup$ – J Walters Sep 22 '16 at 13:12

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