Vertical required navigation performance containment with radio altitude

A system comprising:

• a GPS receiver;
• an air data inertial reference unit;
• a radio altimeter;
• a data logging memory for logging data received from said GPS receiver, from said air data inertial reference unit and from said radio altimeter;
• a programmable command processor programmed to manage the logging of data in said data logging memory;
• and a data transceiver for transmitting data from said data logging memory to a central processing facility on the ground and for receiving programming for said command processor from the central processing facility.

An onboard system for detecting deviation of true airplane vertical position of an aircraft from a desired reference path, comprising:

• means for storing high and low radio altitude thresholds, wherein said high and low radio altitude thresholds vary as a function of horizontal distance from a runway threshold;
• a GNSS receiver for acquiring horizontal position measurements as the aircraft approaches the runway threshold;
• a radio altimeter for acquiring radio altitude measurements as the aircraft approaches the runway threshold;
• and
• one or more processors disposed onboard the aircraft and programmed to perform the following operations:
• (a) recording GNSS horizontal position measurements as the aircraft approaches the runway threshold;
• (b) computing a horizontal distance from the runway threshold as the aircraft approaches the runway threshold using the horizontal position measurements;
• (c) recording radio altitude measurements as the aircraft approaches the runway threshold;
• (d) determining whether any of said radio altitude measurements are less than the corresponding low radio altitude thresholds as the aircraft approaches the runway threshold;
• (e) determining whether any of said radio altitude measurements are greater than the corresponding high radio altitude thresholds as the aircraft approaches the runway threshold;
• and
• (f) performing one of the following operations (i) through (iii) depending on the results of operations (d) and (e):
• (i) generating a first alert signal as the aircraft approaches the runway threshold if a determination is made that any of said radio altitude measurements are less than the corresponding low radio altitude thresholds;
• (ii) generating a second alert signal as the aircraft approaches the runway threshold if a determination is made that any of said radio altitude measurements are greater than the corresponding high radio altitude thresholds;
• and
• (iii) not generating either of said first and second alert signals as the aircraft approaches the runway threshold if a determination is made that said radio altitude measurements are less than the corresponding high radio altitude thresholds and greater than the corresponding low radio altitude thresholds.