Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1998-12-10
2001-09-11
Assouad, Patrick (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S144000, C340S966000, C701S014000
Reexamination Certificate
active
06289289
ABSTRACT:
FIELD OF THE INVENTION
The invention relates in general to a system for monitoring accumulated structural fatigue experienced by an aircraft. More specifically, the present invention relates to a system that monitors the fatigue that accumulates on aircraft structures caused by vertical vibrations, such as turbulence and maneuvering, and pressurization—depressurization cycles.
BACKGROUND AND RELATED ART
At this time, the number of aircraft that exceed their originally designed lifetime service objectives is approximately 39% of the modem air transport fleet. Maintenance of these “aged” aircraft is an important issue; especially the evaluation of accumulated structural fatigue that may cause fatigue failure of the aircraft components during flight. It is estimated that about 3% of all aircraft accidents are a result of accumulated structural fatigue .
Cyclical loading caused by pressurization/depressurization as the aircraft climbs and descends is a material contributor to fuselage fatigue and failure. These pressurization cycles account for from 90% to 100% of the fuselage fatigue life. Recent accidents have occurred that have been directly related to fuselage fatigue failure. In these instances, the aircraft's accumulated flight cycles exceeded the original design service objective, resulting in widespread materials fatigue, or skin cracking, around rivet holes. Ultimately structural failure, such as the separation of parts of the fuselage skin from the aircraft, occurred. As a direct result of these accidents, the aviation industry is increasingly concerned about aircraft component failures due to accumulated structural fatigue.
Aircraft also experience wing fatigue failures that are due to the loads placed on the aircraft by turbulence and maneuvers, in addition to the normal wing loads that occur during takeoffs and landings. The individual contributions of each phenomenon depend on the particular route of the individual aircraft, i.e., number of landings per day, turbulence encounters, flight path, and the like. An accepted estimate of the relative contribution to wing fatigue failure of the various components is: Turbulence 35% to 60%; Takeoffs and Landings: 35% to 50%; and, Maneuvers: 10% to 15%.
Presently, airlines routinely inspect aircraft for fatigue damage, typically during a “C” checks, which occur every 2,400 flight-hours. During the “C” check maintenance technicians use non-destructive equipment such as high-frequency eddy current ultrasound and x-rays to detect structural fatigue. However, “C” checks are expensive and cannot reasonably be done on a frequent basis. Thus, there is a need for a method that helps determine when an aircraft should be scheduled for additional fatigue testing, even before the scheduled “C” check.
By knowing the history of a given aircraft in terms of the parameters that affect fatigue life, airlines could adjust their fatigue maintenance schedules to accurately reflect the number of structural load cycles that the aircraft has encountered and thereby permitting safer aircraft operations while possibly reducing unnecessary maintenance actions.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a system for monitoring, storing, and reporting the accumulation of fatigue occurrences experienced by an aircraft.
It is another object of the present invention to provide a system that monitors, stores, and reports the accumulation of fatigue occurrences experienced by an aircraft without the use of additional measuring devices.
It is a further object of the present invention to provide fatigue monitoring system in which data is collected on the magnitude and cycles of any turbulence encounters; magnitude and number of g-loading accrued by aircraft maneuvering; the number of pressurization cycles that the aircraft has experienced; and the number of takeoffs/landing cycles that have occurred. These data are stored in electronic memory for later review by the flight crew or maintenance personnel.
It is yet another object of the present invention to provide a fatigue monitoring system that accumulates the number of wing flap cycles and landing extensions/retractions, which may also be used to facilitate the maintenance operations of these two critical flight controls.
The novel features which are characteristic of the invention, both as to structure and method of operating thereof, together with further objects and advantages thereof, will be understood from the following description, considered in connection with the accompanying drawings, in which the preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and they are not intended as a definition of the limits of the invention.
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Assouad Patrick
Bui Bryan
Honeywell International , Inc.
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