1. 8644. When an unpressurized aircraft’s static pressure system is leak checked to comply with the requirements of Section 91.411, what aircraft instrument may be used in lieu of a pitot-static system tester? 1. Vertical speed indicator. 2. Cabin altimeter. 3. Altimeter. 4. Cabin rate-of-change indicator. 5. Airspeed indicator. A. 1 or 5. B. 2 or 4. C. 3