26 AIRCRAFT INSTRUMENTS INCLUDING ACCELEROMETERS, AIR SPEED INDICATORS, ALTITUDE INSTRUMENTS, ANGLE OF ATTACK INDICATORS, COMPASSES, MACHMETER (SPEED RATIO) INDICATORS, PITOTS, PRESSURE GAGES, PICKUPS, SEXTANTS, TACHOMETERS AND SYNCHROSCOPES, VERTICAL SPEED INDICATORS, NAVIGATING DEVICES, ASTRO-TRACKERS AND OPTICAL NAVIGATIONAL INSTRUMENTS