Method and apparatus for monitoring aircraft fuselage deterioration

• US 5,083,451 A
• Filed: 10/10/1990
• Issued: 01/28/1992
• Est. Priority Date: 08/21/1989
• Status: Expired due to Fees

• Current Assignee: J V - 1 Limited
• Original Assignee: J V - 1 Limited
• Inventors: Kling, Harry P.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): ROSKOS, JOSEPH
• Application Number:
  US07/597,357
• Time in Patent Office: 475 Days
• Field of Search: 73/49.2, 73/40, 73/49.3, 73/52, 340/605, 340/606, 340/611
• US Class Current: 73/49.2
• CPC Class Codes: G01M 3/3254 using a flow detector G01M3/3245, G01M3/3272 take precedence

Abstract

In a pressurized aircraft, the net air leakage occurring while the aircraft is pressurized at altitude, i.e., the difference between the mass flow rate of all air supplied to the pressurized compartments of the aircraft and the mass flow rate of all air intentionally discharged to the external ambient, is calculated by a system employing air mass flow gauges in the air supply and discharge ducts. Increases in the rate of leakage over time furnish an indication of deterioration of the aircraft structure such as that caused by fatigue and stress corrosion of the external skin.

Claims

1. A method of measuring the deterioration and movement toward ultimate failure with age of the fuselage of an aircraft of the type having an internal pressurization system which comprises:

monitoring the rate at which air leaks out of the fuselage while the fuselage is pressurized by said pressurization system at altitude due to corrosion and fatigue induced porosity of the fuselage.

2. A method of detecting deterioration of the fuselage of an aircraft of the type having at least one pressurized compartment and a pressurization system including a source for supplying pressurized air to the compartment and means for controllably discharging air from the compartment to the ambient which method comprises the steps of:

determining the rate of leakage of air from the compartment through the fuselage while the compartment is pressurized at altitude; and

comparing the rate of leakage determined during a pressurization cycle with the rate of leakage determined during previous pressurization cycles to thereby detect a leakage rate increase indicative of increasing fuselage deterioration.

3. The method according to claim 2 wherein the rate of leakage is determined by measuring the mass flow rate of air supplied by the source in pressurizing the compartment, measuring the mass flow rate of air discharged from the compartment through the controllable means during the same time interval, and calculating the difference between the two measured mass flow rates.

4. The method according to claim 3 wherein the aircraft includes openings into the compartment which constitute additional paths of air leakage while the compartment is pressurized at altitude and wherein the determined rate of leakage is compensated by a factor representative of the air leakage through the additional paths.

5. The method according to claim 4 wherein the compensation factor is updated upon performance of aircraft maintenance operations having an effect on the rate of air leakage through the additional paths.

6. The method according to claim 5 further including the step of recording the determined rate of leakage during each pressurization cycle to develop, over time, a history of the leakage rate for the aircraft.

7. The method according to claim 2 wherein the aircraft includes openings into the compartment which constitute additional paths of air leakage while the compartment is pressurized at altitude and wherein the determined rate of leakage is compensated by a factor representatiuve of the air leakage through the additional paths.

8. The method according to claim 7 wherein the compensation factor is updated upon performance of aircraft maintenance operations having an effect on the rate of air leakage through the additional paths.

9. The method according to claim 8 further including the step of recording the determined rate of leakage during each pressurization cycle to develop, over time, a history of the leakage rate for the aircraft.

10. The method according to claim 2 further including the step of recording the determined rate of leakage during each pressurization cycle to develop, over time, a history of the leakage rate for the aircraft.

11. A system for detecting deterioration of the fuselage of an aircraft having at least one pressurizable compartment and a pressurization system including a source for supplying pressurized air to the compartment and means for controllably discharging air from the compartment to the ambient comprising:

means for measuring the rate of leakage of pressurized air from the compartment through the fuselage while the compartment is pressurized at altitude; and

means for calculating, from the measured rate of leakage during a pressurization cycle and the measured rate of leakage during previous pressurization cycles, the change of the leakage rate to detect an increase therein indicative of increased deterioration of the fuselage.

12. The system of claim 11 further including means for recording, during each pressurization cycle, the determined rate of leakage during that cycle to develop, over time, a history of the leakage rate for the aircraft.

13. The system of claim 12 wherein said means for measuring includes first air mass flow gauging means for measuring the mass flow rate of air supplied to the compartment from the source, second air mass flow gauging means for measuring the mass flow rate of air controllably discharged from the compartment, and means for computing the difference in the mass flow of air measured by the first and second gauging means.

14. The system of claim 13 wherein the compartment has at least one closeable opening to the external ambient and wherein said means for computing compensates for leakage at the opening in determining the change of the leakage rate.

15. The system of claim 11 wherein said means for measuring includes first air mass flow gauging means for measuring the mass flow rate of air supplied to the compartment from the source, second air mass flow gauging means for measuring the mass flow rate of air controllably discharged from the compartment, and means for computing the difference in the mass flow rates of air measured by the first and second gauging means.

16. The system of claim 15 wherein the compartment has at least one closeable opening to the external ambient and wherein said means for computing compensates for leakage at the opening in determining the change of the leakage rate.

17. The system of claim 11 wherein the compartment has at least one closeable opening to the external ambient and wherein said means for computing compensates for leakage at the opening in determining the change of the leakage rate.

18. A method of detecting the status of the closures of the pressurized compartment of an aircraft of the type having an internal pressurization system comprising the steps of:

pressurizing the compartment via said pressurization system while the aircraft is on the ground to a level above the ambient;

measuring the rate of leakage of air from the compartment while so pressurized; and

furnishing an alarm indication in the event the measured rate of leakage exceeds a predetermined value.

19. A system for detecting the status of the closures of the pressurized compartment of an aircraft of the type having an internal pressurization system comprising:

means for measuring the rate of leakage of air from the compartment during an interval in which the compartment is pressurized via said pressurization system to a level above the ambient while the aircraft is on the ground;

means for comparing the measured rate of leakage to a predetermined value; and

alarm means responsive to the means for comparing to furnish an alarm indication in the event the predetermined value is exceeded.