critical altitude


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critical altitude

[′krid·ə·kəl ′al·tə‚tüd]
(aerospace engineering)
The maximum altitude at which a supercharger can maintain a pressure in the intake manifold of an engine equal to that existing during normal operation at rated power and speed at sea level without the supercharger.
(ordnance)
The maximum altitude at which the propulsion system of a missile performs satisfactorily.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

critical altitude

i. A specified altitude or height in the precision approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. Decision altitude is with reference to mean sea level, while decision height is with reference to the threshold elevation. The visual reference means that section of the visual aids or of the approach area that should have been in view for a sufficient time for the pilot to have made an assessment of the aircraft's position and change of position in relation to the desired flight path.
ii. The altitude beyond which an aircraft reciprocating engine cannot maintain normal-rated power, or in some contexts, beyond which it cannot maintain military-rated power.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
(5) This altimeter operates in a CW mode at all altitudes that are equal or lower than a predetermined critical altitude [H.sub.CR], and an interrupted ICW mode at all altitudes that are greater than [H.sub.CR].
The height at which sprites spark to life also roughly agrees with what theorists like Pasko estimate to be the critical altitude for breakdown.
However, at some point above critical altitude, the pilot must comply with a table that shows the maximum allowable manifold pressure and reduce power accordingly.
An induction leak, while perhaps not an emergency situation, still affects the engine's efficiency as well as limits its critical altitude. Think about it: The turbocharger essentially pressurizes the induction system, but if there's a leak, all that squeezed air will try to escape through the opening.
Although it's a good, economical performer at low altitude, SMA originally spec'd a turbo that lacked sufficient pressure ratio, so the engines critical altitude was essentially sea level and its service ceiling was limited to 12,500 feet--anemic for a turbocharged engine.
Owners say they get a higher critical altitude with the inter-coolers, along with lower operating temperatures.
Another issue exists for the turbocharged-engine operator in the flight levels: "bootstrapping." This term describes the relationship between manifold pressure, propeller speed and fuel flow at and above the engine's critical altitude, or where the turbo's wastegate is fully closed.
Technically, the turbonormalized system doesn't have a critical altitude since it boosts to sea-level to the airplane's certificated ceiling of 25,000 feet.