Service ceiling
Encyclopedia
With respect to aircraft, a ceiling is the maximum density altitude
Density altitude
Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground...

 an aircraft can reach under a set of conditions.

The word ceiling
Ceiling (cloud)
- ICAO :The height above the ground or water of the base of the lowest layer of cloud below 6000 meters covering more than halfthe sky.- United Kingdom :...

can also refer to the height of the lowest obscuring cloud layer above the ground.

Service ceiling

The service ceiling attempts to capture the maximum usable altitude of an aircraft. Specifically, it is the density altitude
Density altitude
Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground...

 at which flying in a clean configuration
Clean configuration
Clean configuration refers to the flight configuration of an fixed-wing aircraft when its external equipment is retracted to minimize drag and thus maximize speed for a given power setting.-Application:...

, at the best rate of climb
Rate of climb
In aeronautics, the rate of climb is an aircraft's vertical speed - the rate of change in altitude. In most ICAO member countries , this is usually expressed in feet per minute and can be abbreviated as ft/min. Elsewhere, it is commonly expressed in metres per second, abbreviated as m/s...

 airspeed
Airspeed
Airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed , calibrated airspeed , true airspeed , equivalent airspeed and density airspeed....

 for that altitude and with all engines operating and producing maximum continuous power, will produce a given rate of climb (usually 100 feet per minute climb or 30 meters per minute). Margin to stall
Stall (flight)
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded...

 at service ceiling is 1.5g.

The one engine inoperative (OEI) service ceiling of a twin-engine, fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

 is the density altitude at which flying in a clean configuration, at the best rate of climb airspeed for that altitude with one engine producing maximum continuous power and the other engine shut down and feathered, will produce a given rate of climb (usually 50 feet per minute).

However some performance charts will define the service ceiling as the pressure altitude at which the aircraft will have the capability of climbing at 50 ft/min with one propeller feathered.

Absolute ceiling

A less often used term is the absolute ceiling – the highest altitude (calculated on the ground and which will never be reached in flight except during flight testing) at which an airplane can sustain level flight, which means the altitude at which the thrust of the engines at full power is equal to the total drag at minimum drag speed. In other words, the altitude where maximum thrust available equals minimum thrust required, so the altitude where the maximum sustained (with no decreasing airspeed) rate of climb and angle of climb reach 0. Most commercial jetliners
Jet airliner
A jet airliner is an airliner that is powered by jet engines. This term is sometimes contracted to jetliner or jet.In contrast to today's relatively fuel-efficient, turbofan-powered air travel, first generation jet airliner travel was noisy and fuel inefficient...

 have a service (or certificated) ceiling of about 42000 feet (12,802 m) and some business jets about 51000 feet (15,545 m). While these airplanes' absolute ceiling is much higher than standard operational purposes, it is impossible to reach (because of the vertical speed asymptotically approaching zero) without afterburner
AfterBurner
The AfterBurner is a lighting solution for the Game Boy Advance system that was created by Triton-Labs.Originally, portablemonopoly.net was a website created to petition Nintendo to put some kind of light in their Game Boy Advance system...

s or other devices temporarily increasing thrust. Flight at the absolute ceiling is also not economically advantageous due to the low indicated airspeed which can be sustained: although the true airspeed (TAS) at an altitude is typically greater than indicated airspeed (IAS), the difference is not enough to compensate for the fact that IAS at which minimum drag is achieved is usually very low, so a flight at an absolute ceiling altitude results in a low TAS as well, and hence in a high fuel burn rate per distance traveled. Also, the absolute ceiling varies with the air temperature and, overall, the aircraft weight (usually calculated at MTOW).

Combat ceiling

Combat ceiling is the highest altitude at which an aircraft is expected to have a given (usually 500 feet per minute) climb.

Alternatively, combat ceiling is defined as the highest altitude at which an airplane can sustain altitude and airspeed during a horizontal maneuver with a given bank angle (usually 15-20°).

Dynamic ceiling

Dynamic ceiling is the highest altitude an airplane can reach by using its kinetic energy
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...

 while still maintaining minimum controllable airspeed.
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