Flight Crew Air Transport Pilot (ATP)
Confusion; Communication Breakdown; Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Inflight Event / Encounter Weather / Turbulence
Flight Crew Landed in Emergency Condition; General Maintenance Action
Procedure; Human Factors; Aircraft
We were getting vectors to the GPS Rwy 8 at ZZZ1 in IMC conditions and active icing (Ice light illuminated)  when we got the Horizontal Stabilizer (HStab) Ice Fail annunciator. As we were near the airport and knew that the cloud bases were fairly high; we felt the best course of action to exit the icing conditions would be to continue descent to the airport.  We accomplished the Emergency procedure for an HStab Ice Fail light and continued to a Flaps-10 landing as called for in the procedure. Approach and landing was without incident.  This was the aircraft's first encounter with icing conditions since it had come out of Maintenance in ZZZ for troubleshooting of an HStab Ice Fail annunciation. Maintenance in ZZZ had run the Ground Test of the system and found no anomalies; but noted some areas on the HStab that needed additional sealant which they applied.  Our incident thus makes this the second consecutive icing encounter and subsequent HStab Ice Fail. (We  had also tested the system prior to takeoff and found no faults).  After landing at ZZZ1; and at the direction of Maintenance Control; we were asked to push in the pulled circuit breaker (C/B) and retest the system. We accomplished this and found no fault.  With two consecutive icing encounters and two consecutive HStab Ice Fails; and all the while the Ground Test passes; it is obvious that the normal Ground Test is not robust enough to find the cause of this system failure.  Maintenance should be required to escalate the troubleshooting of this system beyond a normal Ground Test and sign-off; before this aircraft is allowed to re-enter icing conditions!
Reporter stated the Circuit Breaker (C/B) they pull removes power from the Horizontal Stab (HStab) De-ice Heater Controller. Opening the C/B is part of their Abnormal Procedures to prevent a possible thermal runaway of the Controller or heating mats that are bonded to the HStab leading edge and Elevator horns. Reporter stated that part of the problem with identfying the cause of a HStab Ice Fail annunciation is finding a Maintenance facility that is familiar with the Beechjet BE-400XP De-Ice System and will do adequate troubleshooting. Until recently; he was not aware there are two procedures: an electrical Continuity and Resistance Check and a Pitot Static Check that should be accomplished by Maintenance before an HStab Ice Fail write-up is signed-off in the Logbook. The previous incident only had one test accomplished.  After his second HStab De-Ice failure; Technicians from a different Maintenance facility performed both tests and also used a 'cold' spray and ice packs on various sensors to simulate a cold environment. That's when the Speed sensor failures seem to occur. The same technicians also noted that without the 'cold' tests; the warmer ground environment does not seem to find the sensors that are known to fail in a cold environment. One of the Speed sensors was replaced and seems to have corrected the problem.Reporter stated he has already experienced four HStab Ice Fail annunciations this winter on BE-400XP aircraft requiring Abnormal Procedures and landing with 10-degree Flaps instead of 30-degree flaps. Two of the HStab Ice Fails occurred in icing conditions and two after exiting icing conditions when he shut-off the HStab Anti/De-Ice switch. The HStab De-Ice System does go through one final heat cycle after the De-Ice switch is shut-off. Either way; Flight crews must still perform an Abnormal Procedures Check whenever the HStab Ice Fails annunciator illuminates and red light flashes. Ice on the Horizontal Stab could lead to a tail stall; made worse if flaps were extended more than 10-degrees.
A Captain notes that after two consecutive icing encounters and two consecutive Horizontal Stab (HStab) Ice Fail annunciations on two different flights; the normal Ground Test used by Maintenance is not 'robust enough' to find the cause of the HSTAB Ice Fails that have occurred in flight; on a Beechjet BE-400XP aircraft.