"DISPLAYS SIMULATED GEOMETRIC AIRCRAFT ALTITUDE IN TEN FOOT INCREMENTS,THE READOUT DOES NOT COMPUTE A GEOMETRIC ALTITUDE BELOW SEALEVEL,IF BAROMETRIC PRESSURE IS INCREASED BY ONE INCH OF MERCURY WHILETHE TRAINER IS AT SEA LEVEL,THE READOUT WILL INDICATE AN AMBIGUOUS NEGATIVE VALUE SINCE THE INTEGRATOR ISNOT CAPABLE OF COMPUTING THIS LARGE CHANGE"