Originally Posted by
zenlizard
Typically, performance for aircraft in this period is given as "service ceiling". There is a difference between this and absolute ceiling.
The service ceiling is close to the "effective ceiling" you're groping at.
The absolute ceiling is the density altitude at which an aircraft can sustain level flight at maximum engine output; in other words, the vertical component of the thrust vector is zero. No further vertical speed (upward) is possible.
The service ceiling, however is quite different, and usually quite a bit lower than absolute ceiling. The definition of service ceiling is the density altitude at which the aircraft's rate of climb reaches a given value-for propeller-driven aircraft, this is typically a value of 100ft (or 30m)/minute. Although for multi-engine aircraft, this defined value is sometimes 50ft (or 15m)/min, with one engine off, and propeller feathered.
The reason for this being that while climb beyond an aircraft's service ceiling is by definition possible, there have to be exceptional situations to make the climb to the extra altitude worth the effort.
Hope this helps.
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