Beechjet 400
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
Flight Crew Diverted; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft; Weather
The initiating event for this report is the failure of the Horizontal Stabilizer (HSTAB) de-ice system on this aircraft.  Crew was flying Aircraft X with a high profile passenger.  At altitude we encountered the tops of the weather and turned on HSTAB de-ice; only to have it fail.  Weather was unacceptable to continue to destination; with potential icing conditions present all the way to the surface.   We diverted back to the east and were able to descend while remaining clear of clouds; but not without considerable difficulty and assistance from ATC.  The checklist calls for the crew to remain clear of icing conditions; but given the definition we have for icing conditions; this is nearly impossible while flying IFR in the flight levels except on the clearest of days.  Had we not encountered the high altitude cloud deck; we would not have discovered the failed system until much closer to destination; possibly without the option of remaining clear of clouds while diverting back to the east.  We were able to coordinate a recovery trip on another aircraft and diverted in order to meet that aircraft.  But the following day; we were assigned another aircraft; Aircraft Y.  This aircraft had a long history of issues with the HSTAB de-ice system; and had a heater mat replaced just before we flew it.  This mat showed signs of having been burned while on the tail of the aircraft.  On the maintenance line was the following entry (paraphrased) 'Aircraft has recurring issue with HSTAB de-ice and needs to be ferried for evaluation.'  But apparently the mat was replaced and we were the first to fly it.  The system tested good on the ground check but failed immediately the first time we turned it on in flight; with passengers on board.  These two events are but symptoms of a much larger problem.  Every pilot flying the 400XP knows the failure rate of the HSTAB system; yet every winter we continue to fly in icing conditions and accept the likelihood of it failing to function properly.  This is no longer an acceptable way to operate.  The aircraft accumulates ice quite quickly; and the buildup of ice on the tail could result in an unrecoverable situation during approach and landing.  There was a relevant event in the New York area a few years ago which I am certain all involved in safety are aware of.   We have a long history of problems with the HSTAB de-ice system on the 400XP; and to date no good fix has been identified.  While writing up one aircraft we were told by MX control; 'well at least we're not doing as bad as last year.'  This is a disturbing thing to hear; that our measure of success is simply comparing failure rates to last year; especially when this has been an extremely mild winter season.  Maintenance now sends a form for crews to fill out following every HSTAB failure in order to collect more data on the nature of the failure.  My flying partner has filed another report involving repeated issues on Aircraft Z; and this was evaluated as being an isolated problem with a single aircraft.  But he has had failures in no less than THREE different aircraft; including these two while flying with me; in the past three weeks.  While I am sure the company is tracking this from a reliability standpoint; it is obvious to crews on the line that this is more of a design and certification issue than one of proper maintenance.  We all realize this is not an easy thing to fix; but it must be addressed. The aircraft will be in our fleet for several more years and we will continue to operate with undue risk.  We should move away from looking at these failures as simply maintenance issues and start looking at the more serious implications.  Our Maintenance folks are doing an admirable job addressing the individual events; but are unfortunately chasing ongoing problems with a poor design. As I understand it; this is the third attempt over the history of the Hawker 400XP to implement a reliable HSTAB de-ice system on the aircraft.  The complexity of this current design cannot be overstated.  Barring another manufacturer design change or modification; I feel that the following options should be considered for implementation by the company:  1. Restrict the aircraft from operating in icing conditions; or  2. Following ANY maintenance on the HSTAB de-ice system; require the aircraft to be evaluated in flight (preferably in visible moisture) prior to releasing it for passenger flights.  Rarely does the system fail the test on the ground; but it has been my experience that the failures occur in the air; especially once in a high-moisture environment or precipitation.  3. The above mentioned change should be inclusive of any 'unable to duplicate' maintenance findings.  This system is critical to the safe operation of the Hawker 400XP; yet time and again it fails to provide the protection needed to ensure this safety.  If it continues unaddressed; we are inviting real danger.
The reporter has been flying the BE400 for about seven years and the HSTAB deice system has been an ongoing problem with several attempts to correct the problems; none of which has been successful.  The control system seems to be the cause of the failures with the heating elements themselves not being implicated.  The control system is complex and receives sensor inputs concerning altitude; airspeed; temperature; dynamic pressure; flap position; and a flap delay sensor.  This system is essential on this aircraft during approach in icing conditions and tail stalls are likely when it is inoperative.
BE400 Captain describes a reoccurring series of failures of the Horizontal Stabilizer (HSTAB) de-ice system of aircraft in his company's fleet.