Date: 201204
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Cessna Citation Sovereign (C680)
Operator: Fractional
Operating under: Part 91
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Flight Dynamics
Component problem: Failed
Reporter organization: Fractional
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: I was the pilot non flying. MAU 1 [Modular Avionics Unit] failed message appeared just as the lead customer was near the cockpit and giving me a panic look because he saw the flashing lights; and was able to sense the brief loss of pressurization. In an instant; we lost: Autopilot; Yaw damper; Air Data Computer (ADC); attitude and heading indicator; terrain display. The pilot flying quickly kept the airplane going the same way; the loss of the ADC computer rendered the left side Primary Flight Display (PFD) with no airspeed; Vertical Speed Index (VSI); attitude and heading. It also forced the pressurization system to go to manual; which explained the quick change of pressure and condensation that happened in the cabin. The owner asking what was going on was an added distraction; but I chose to not answer him right way; as I first needed to realize what the discrepancy was. ATC called and gave us our filed cruise altitude of FL430. Although I did acknowledge this call; I did not inform them of our situation yet; as it just happened; and needed more time to assess. But I did turn to my copilot; and inform him that I wanted him to level off at FL410. Most checklists ask us to level off at this level; and I thought we certainly do not need to go higher at this point. I quickly located the appropriate checklist; which unfortunately was a laundry list of lost items but had absolutely nothing about troubleshooting. I was able to get back airspeed; VSI; ATT; HDG to the left display via reversion but was unable to get an autopilot back on or moving map. It became clear that we were no longer able to fly another 3 hours to the islands; but more importantly; was unable to maintain RVSM since we would be hand flying this aircraft to who knows where. It was also easy to realize that this did not constitute an emergency. Although the art of hand flying is not common on jets; it is not the end of the world; as we know it. We now had the time to think. First; inform ATC that we have lost part of our avionic equipment. Second; inform them that we were now non-RVSM compliant. Third; call company and let them figure out where they want to pick up 6 passengers who would love to continue the beginning of their vacation. So that is exactly what we did in this order. The pilot flying kept flying the best he could and doing the radio. I first talked to the lead passenger who still wanted to know what was going on. [I] then made a first call to the Duty Manager; which unfortunately went straight to voice mail. I hung up; and called Maintenance; who wanted to know if I had called the Manager first? We finally figured out that the company wanted us to go. At this point; we were [about two hours away] and were not comfortable flying a now un-airworthy aircraft for this distance or this length of time. So they suggested a closer airport; and I agreed to it; although it was still slightly over 1 hour of flight time. I figured this was a justifiable trade off between helping the company find another aircraft and making the FAA happy if they were looking over our shoulders. While I was on the phone; I saw my partner struggling to descend to FL280 as assigned below RVSM; struggling to maintain a heading; type in the FMS a new intersection given to him by ATC. He must have had trouble with spelling; because I saw the airplane make a 180 to the right. I asked him what was going on; and he responded that ATC wanted us to go to this point. I then told him that this didn't make sense; and although I still could not help him with the radios (I was about to be transferred to Dispatch to be released to our new diversion airport); I wanted him to confirm what ATC wanted. I saw him struggle some more with spelling; input in the FMS; altitude variation of +-200 FT; which I tried to help him correct. He was doing the heading changes; and I the pitch; while still being on the phone. It is not easy to become a single pilot in what became a high load work environment; and he later told me that he felt harassed by the Controller who evidently did not understand the difficulty of our situation. Hence the dilemma: We did not feel that this situation warranted declaring an emergency. He did tell ATC that at this point; he was single pilot and that his Captain was on the phone with company. Yet; this particular Controller kept giving him a hard time when he was unable to comply with his instructions. Because I was not listening; I do not know how the transcript went over the radio. Perhaps; he should have said unable; and kept a radio silence until he had the airplane under control. I know he did say stand-by a few times; but the Controller kept pushing. Regardless of how it went between him and ATC; I felt compelled to write this report to offer our apology if we briefly created a mess on a radar screen that day; and perhaps also to provide a better clue to a controller that when a crew asks for some time; they really mean it; and leave them alone until they can come back on the radio. There are not many things that we could have done differently. Perhaps; we could have waited to be level at FL280; under RVSM; before one of us makes a phone call. This leaves the person flying with the radio; with no longer a 'check and balance' if he hears a waypoint incorrectly; as it happened on this flight. On the other hand; it seemed that it would be an easy diversion; and we could not have expected an impatient controller.




Synopsis: CE680 Captain experiences a MAU 1 failure at FL340 resulting in the loss of Autopilot; Yaw damper; ADC; attitude and heading indicator. After the failure the aircraft is no longer RVSM capable and the crew diverts to a suitable airport.