Challenger 300 flight crew reported spurious indications from the Flight Directors led to unusual aircraft attitude and a course deviation. The aircraft was turned over to Maintenance after arrival at destination airport.
Synopsis
Challenger 300 flight crew reported spurious indications from the Flight Directors led to unusual aircraft attitude and a course deviation. The aircraft was turned over to Maintenance after arrival at destination airport.
Narrative
On Day 0 at XA:23; Aircraft X (A Bombardier Challenger 300) departed ZZZ en-route to ZZZ1. The aircraft filed and operated under an IFR flight plan; VMC conditions prevailed. Pre-flight inspections were normal; the aircraft was configured for a normal flaps 10 takeoff. The departure procedure was not new to either pilot as we operate out of ZZZ often. The clearance is almost always the same; turn to a heading and maintain 3;000 feet.Tower cleared us for takeoff and assigned a right turn to a heading of 240; maintain 3;000 feet. Takeoff was normal; gear retracted and flaps retracted on schedule. The Pilot Flying (PF) began to make the turn to heading 240 and climb was normal.As Pilot Not Flying (PNF); I began to perform the After Takeoff Checklist; briefly lowering my eyes from the instrument panel to do so.At about 1;500 feet and climbing; I noticed that the aircraft was in a sharp bank to the right (as directed by the command bars) and very shortly after the aircraft aural warning sounded 'Bank Angle..Bank Angle'(indicating 60 degrees of bank). I estimate that the aircraft was in an approximate 60 degree turn to the right and that the nose of the aircraft had dropped; briefly; which caused the aircraft to descend at a shallow rate. On seeing this I asked the PF if he 'had the aircraft' which he responded to in the affirmative. The PF was flying the aircraft by reference to the attitude indicator in which the aircraft indicator was within the command bars. The attitude indicator/command bars showed that the aircraft was on course and within the indicated command bars; albeit at a high pitch angle and high roll rate uncharacteristic of this phase of flight. The command bars then indicated a turn back to the left and again directed an abnormally high pitch angle of at least 20 degrees. As the aircraft turned back towards the commanded course the vertical speed increased substantially; partially due to the conversion of horizontal to vertical component of lift. The altitude limit of 3;000 feet was exceeded. The PF stopped flying via reference to the command bars; reverted to raw data and began to return the aircraft to its assigned altitude of 3;000 feet/heading 240 degrees. Before this was able to happen; approach control assigned a higher altitude and direct to a NAV fix.The time from takeoff to the time of the excursion was approximately 3 minutes. The time to recognize the deviation and respond appropriately took about 15 seconds (Human Factor - time to identify; interpret and respond). At all times during this incident; and until the PF reverted to raw data; the aircraft was flown within the command bars indicated on the attitude indicator.Approach control (XXX.XX ZZZ Departure) notified us of a possible pilot deviation and gave us a number to call on arrival at our destination.On arrival at our destination we discussed the incident; deviations made; and called the number assigned to speak with ZZZ TRACON. As a crew; we understand that deviations such as this are serious and must be identified in a very short period of time. We did identify a problem almost immediately; however; only after the altitude/heading excursion was made as we were within 1;500 feet of level off. ZZZ TRACON also stated that the aircraft had turned to the east from its assigned 240 degree heading. We have requested radar track to confirm this as it is important to know and compare to what we witnessed in the cockpit so that we are able to report this to both the aircraft and avionics manufacturers. During the entire incident; there were no Master Caution or CAS Indications. The only abnormal indication that presented was the uncharacteristic command bar indication and the TAWS AURAL Warning of 'Bank Angle...Bank Angle'.As a crew we are very concerned with what happened. We take full responsibility for the heading and altitude deviation. As a crew; we followed standard operating procedures which include the use of the attitude indicator;aircraft indicator and the command bars. The aircraft was flown completely within the limits indicated by the command bars. Had the autopilot been activated; we feel that things could have been much worse. While both of us as a crew followed the prompts of the command bars and there was a moment when the aircraft was flown outside of the indicated limits due to reverting to raw data only; we corrected and returned to the course assigned. If the autopilot had been engaged during this time and the command prompts presented as they were to the hand flying crew; structural damage would have been likely and a much worse situation may have unfolded.Previously; a similar incident on the same airframe type and same avionics package occurred which resulted in the loss of one life. The conditions that center around the core problems of that aircraft are remarkably similar to what we experienced as a crew on Day 0. Namely; the possibility of material introduced into the pitot static system. The previous incident included many Pilot errors including leaving a pitot tube cover on a probe resulting in an aborted takeoff. Though not mentioned in the NTSB Preliminary Report; there is a theory among pilots on professional pilot boards that this may have resulted in the introduction of melted plastic or other debris into the pitot static system which on a later flight caused an Air Data Computer malfunction and subsequent system failures or mis compares. On our flight on Day 0; we originated out of ZZZ2 and departed in very heavy rain. It is my opinion that there may have been water accumulation within the system though there were no CAS messages or other indications to confirm this and the aircraft operated normally until the departure from ZZZ. On arrival to our home base; our Director of Maintenance contacted the last service center that we were at (we had just taken delivery of the plane from maintenance several days prior - this was the first assigned flight since maintenance) as well as the Aircraft Manufacturer and Avionics Manufacturer. At this time; Technicians are en-route to evaluate our system; and the aircraft is grounded until firm evidence of the malfunction is presented and resolved.Both crew members intend to fully cooperate with any investigation of the excursion and would like to help find the cause of the erroneous information that contributed to the deviation while also continuing to improve skills that will prevent this type of deviation from happening again.Human factors - the time to identify; interpret and respond to what we saw played a part in the deviations made. The Challenger 300; lightly loaded; on a cool day at sea level has an initial climb rate ability that exceeds 5;000 FPM.Crew identification of an uncharacteristic commanded pitch and roll attitude also played a role. Identifying what is not normally seen in normal operations and reverting to raw data only; knowing when to remove automation and just fly the airplane. As a result of this incident; we are going to move performing the After Takeoff Checklist to an altitude of at least 5;000 feet AGL. At this point; as trained for the last XX years the standard call out on departure is gear up; flaps set (if greater than 10 degrees - indicate setting); flaps up; after takeoff checklist. This is often called for at X00 feet AGL as the flaps are retracted. This experience has shown that moving ones attention from takeoff and climb out to a checklist (however briefly) is unnecessary. Most operations observe a 'Sterile Cockpit' below 10;000 feet - In my opinion; this should apply to all activities including the after takeoff checklist. The items on that checklist are not necessary for the safe operation of the airplane and consist of mainly cleaning the aircraft up; verifying that the gear and flaps are retracted. Both gear and flaps can be called as a course of flow and later verified at a safer altitude when there is more time and altitude. We will investigate further and incorporate into our SOPs if this is determined to be a safer option. Given the incident at hand and the very short time it took to deviate; I believe that this one action will be beneficial. Crew experience - both crew members are seasoned pilots with a great amount of experience with the Challenger 300/350 airframe. The PF that day is a former Air Force Fighter Pilot; Airline Pilot and Corporate Aviation Manager with approximately X years and over X;000 hours of experience on this aircraft. I have personally flown this model of aircraft for XX years; approximately Y;000 hours over many different serial numbers; performing flight tests; entry into service; new aircraft delivery and instruction for pilots new to this airframe. In XX years of operating this aircraft domestically and internationally; I have never experienced what I saw on Day 0. I would like to have answers to what happened and will cooperate with any inquiry or investigation into this matter. I take full responsibility for the deviation of assigned altitude and heading. I would like to know what prompted the command bars to initiate action that contributed to the deviation made.At this time the aircraft manufacturer; avionics manufacturer and service center are working with us to identify any problems.
Second reporter narrative
On Day 0 at XA:23; Aircraft X departed ZZZ en-route to ZZZ1. Pre-flight inspections were normal; the aircraft was configured for a normal flaps 10 takeoff. The departure procedure was not new to either Pilot as we operate out of ZZZ often.Tower cleared us for takeoff and assigned a right turn to a heading of 240; maintain 3;000 feet. Takeoff was normal; gear retracted and flaps retracted on schedule. As Pilot Flying (PF); at approximately 400 feet I began to make the right turn to heading 240 and climb to 3;000 feet referencing and following the flight director guidance. As the aircraft climbed through approximately 1;500 feet the aural warning 'Bank Angle' was announced and the flight director still indicated a command to turn right and climb at approximately 20 degrees nose high. My co-pilot alerted me of these conditions and at that point I realized that the flight director commands were not correct and transitioned back to raw data to fly the aircraft. As a result of incorrect flight director commands aircraft turned past 240 degrees and climbed to an altitude of approximately 4;400 feet at which point I began to correct back to the assigned heading and altitude. During this period approach control assigned a higher altitude and direct to a NAV fix and we complied with those instructions as directed. The time from takeoff until the time of the excursion was approximately 3 minutes. The time to recognize the deviation and respond appropriately took about 15 seconds. At all times during the heading and altitude deviation the aircraft was flown within the command bars indicated on the attitude indicator.Approach control (XXX.XX ZZZ Departure) notified us of a possible pilot deviation and gave us a number to call on arrival at our destination.On arrival at our destination; we discussed the deviations made and called the number assigned to speak with ZZZ TRACON. As a crew; we understand that deviations such as this must be identified in a very short period of time. We did identify a problem almost immediately; however; only after the altitude/heading excursion was made. ZZZ TRACON also stated that the aircraft had turned to the east from its assigned 240 degree heading. We have requested radar track to confirm this as it is important to know and compare to what we witnessed in the cockpit so that we are able to report this to both the aircraft and avionics manufacturers.As a crew we are very concerned with what happened. We take full responsibility for the either heading or altitude deviation. As a crew; we followed standard operating procedures which include the use of the attitude indicator; aircraft indicator and the command bars. The aircraft was flown completely within the limits indicated by the command bars. Had the autopilot been activated; we feel that things could have been much worse. While both of us as a crew followed the prompts of the command bars and there was a moment when the aircraft was flown outside of limits; we corrected and returned to the course assigned. If the autopilot had been engaged during this time and the commands prompts presented as they were to the hand flying crew; structural damage would have been likely and a much worse situation would like lay have unfolded.Previously; a similar incident on the same airframe type and same avionics package occurred which resulted in the loss of one life. The conditions that center around the core problem of that aircraft are remarkably similar to what we experienced as a crew on Day 0.On arrival to our home base; our Director contacted the last service center that we were at as well as the aircraft manufacturer and avionics manufactured. At this time; technicians are en-route to evaluate our system and the aircraft of grounded until firm evidence of the malfunction is presented.Both crew members intend to fully cooperate with any investigation of the excursion and would like to help find the cause of the erroneous information but also continue to improve skills that will prevent this level of excursion from happening again. Crew members will work with ATC as well as FAA to do this.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.