Learjet 36
Air Traffic Control Fully Certified; Flight Crew Flight Instructor; Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 60; Flight Crew Total 10000; Flight Crew Type 200
Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Inflight Event / Encounter Weather / Turbulence
Flight Crew Overcame Equipment Problem
Aircraft; Human Factors; Weather
Activated Windshield Heat (WSH) ten minutes prior to top of descent. Seconds later; annunciator panel illuminated 'WSH overheat' accompanied by strong odor throughout aircraft. Deactivated WSH until Overheat (OH) light extinguished. Re-activated WSH. WSH OH light illuminated again. Despite repeated attempts to sustain normal operation; WSH OH light re-illuminated at even minimal settings. Descending through FL240 autopilot disconnected. Attempts to reconnect accompanied by un-commanded right roll. With left windshield occluded; storm clouds interspersed throughout flight path; and the AP inop; considered switching pilot flying (PF) and pilot monitoring (PM) duties with SIC; whose windshield was clear; possibly due to absorbed heat radiating from glare-shield (black) after prolonged flight with sun on right side of aircraft. Prior to assigning aircraft control to SIC; checked to confirm normal operation of right side flight instruments: noted SIC's EADI (Electronic Attitude Direction Indicator) indicated 'Fatal Failure.' Aircraft type does not provide for electronic switching to bootstrap gyro signal from opposite side to inop side. Elected to retain aircraft control and PF duties until descended into continuous VMC. SIC performed PM duties and provided visual guidance to avoid cumulonimbus clouds (CBs). Slowed AC to 250 kts at 10;000 ft. At approximately 6;500 ft MSL; observed airspeed indication had increased to 280 kts. Corrected and continued flying by instrument reference until descending to approximately 2;500 ft (1;000 ft above pattern altitude); and continuous VMC; in vicinity of [the airport]. Then asked SIC to take controls for landing.
Learjet crew reported encountering failures of the Windshield Heat; Autopilot; and Electronic Attitude Direction Indicator during flight. Crew continued to VMC conditions and landed uneventfully.