Autothrottle Height Verification via Barometric Cross-Check
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Solution Overview
Problem
Aircraft automatic throttle systems rely solely on internal verification of low range radio altimeter (LRRA) readings, leading to undetected failures and catastrophic accidents during landing, as seen in the 2009 Boeing 737-800 crash, where an erroneous LRRA reading caused premature throttle reduction and stall.
Innovation Solution
A system that combines barometric altitude with a ground-elevation database to verify aircraft height, allowing the autothrottle control to prevent premature throttle retardation by comparing LRRA readings with barometric altimeter readings and ground-elevation data, thereby providing additional safety measures to ensure accurate height calculation and safe landing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the autothrottle system relies solely on internal verification of LRRA readings, then the system complexity is reduced, but the reliability of height measurement deteriorates leading to undetected failures
Solution Approach 1:
The patent combines barometric altitude measurement with ground elevation database lookup to create a verification system for radio altitude readings. The barometric altimeter and ground elevation data are merged with the existing LRRA system to provide cross-validation, thereby improving reliability without significantly increasing overall system complexity.
Solution Approach 2:
The ground elevation database acts as an intermediary that enables comparison between barometric altitude and radio altitude. By introducing this database as a mediator, the system can verify LRRA readings against expected heights derived from barometric data and terrain information, improving detection of erroneous readings.
2Reliability
If additional verification systems are added to verify LRRA accuracy, then the reliability of height measurement is improved, but the device complexity increases
Solution Approach 1:
The barometric altimeter serves multiple functions: it provides altitude information for navigation and serves as a verification source for radio altitude readings. This multi-functionality reduces the need for dedicated verification hardware, thereby improving reliability while minimizing increases in device complexity.
Solution Approach 2:
The system implements feedback by continuously comparing radio altitude readings with heights calculated from barometric data and ground elevation. When discrepancies are detected, the system can alert the pilot or automatically adjust throttle settings, creating a closed-loop verification system that improves reliability through intelligent monitoring rather than additional hardware.
3Ease of operation
If the autothrottle system uses only LRRA internal verification, then the ease of operation is maintained, but the loss of information occurs when LRRA fails undetected
Solution Approach 1:
The system performs preliminary verification by comparing radio altitude with barometric-derived height before the autothrottle acts on the LRRA reading. This preliminary check ensures that erroneous readings are detected in advance, preventing loss of critical height information and allowing the system to maintain ease of operation through automatic detection and correction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces the reliance on LRRA internal verification, preventing incidents related to undetected errors by correlating radio and barometric heights, and includes features like autothrottle disable or prevention of engine idle retardation, enhancing the safety of aircraft landing procedures.
Implementation Method 1
a barometric altimeter. The barometric altimeter may be used in calculating a second height of the aircraft above ground-level
Implementation Method 2
a low range radio altimeter. The low range radio altimeter may be used in calculating a first height of the aircraft above ground-level
Data Source
AI summary
A system for safely landing an aircraft including a low range radio altimeter, a barometric altimeter, and an autothrottle control. The low range radio altimeter calculates a first height of the aircraft above ground-level, the barometric altimeter calculates a second height of the aircraft above ground-level, and the autothrottle control determines if the first height and the second height do not correlate. If the first and second heights are determined to lack correlation, then automatic thrust-control of the aircraft is stopped. In some embodiments, the second height is partially calculated by accessing a ground elevation database to obtain an elevation of the ground above sea level and determining a difference between the elevation of the ground above sea level and an elevation of the aircraft above sea level.