Narrative:

I had slowed back to .75M because we were navigating around/between thunderstorms. Our destination was reporting winds gusting to around 30 KTS and ceilings at 1800 ft. I decided to brief early in cruise because we were in a relatively smooth patch of air and it looked like the descent was going to be bumpy. We briefed/set up for the ILS to 6R and I believe that somewhere around that time; we got our first master caution 'ding.' the caution text extinguished immediately; though; and I don't believe I even had a chance to read it before it was gone. I had noticed; however; that I kept getting slow and was adding power often to maintain our mach. Sometime soon after the first master caution; we got a second; again quickly extinguished; but this time not before I saw an 'EFIS comp mon' message. We checked our heading indicators because that's what we're used to seeing with EFIS comp mon; but everything was matching. Then we got a mach trim master caution. The captain ran the QRH; but I was busy figuring out that I was adding power too often for a .75 cruise; and when the EFIS comp mon went off again; I had already noticed that; while I was maintaining .75 beautifully on my pfd; I was passing through .80 to .81 on my captain's instruments and the isi (integrated standby instrument). I made corrections; told the captain; and this time; when the EFIS comp mon came on--and stayed on. I also had an airspeed flag. I want to say we got a stall fail caution at this point as well; but I don't really remember exact chronology. I believe at this point the plane started making small rolling motions; but rapid; and I turned off the autopilot and requested that the captain get us clearance out of rvsm. (Somewhere during all of this; we had descended down to F330). He requested lower; and I began hand-flying the step down while he ran the QRH for a stall fail first; then the EFIS comp mon. My airspeed indicator was winding down 40 KIAS; but I kept the FD on for the heading guidance while flying pitch for vertical speed and airspeed off the captain's pfd and the asi. Somewhere along the way; the captain completed the EFIS comp mon checklist and switched the air data source selector to air data computer 1. I now had airspeed indications back on my side; but I was still hand flying. Because we had filed 'nonstandard routing;' we were not filed on an arrival; but rather direct to the airport. On the descent; while the captain was running a checklist--not sure which--we were given direct to a VOR for an arrival. I was still hand flying; and the airspeed I was getting from air data computer 1 was decaying while the isi airspeed was not; and I did not want to mess with navigation in addition to hand flying. I told the captain how I felt; and he made a call to ATC that we had lost some of our instrumentation and would like vectors. Somewhere right around then; every indicator on the pfd flagged red; and I believe a number of master cautions went off; but I'm not sure. I expressed my desire to declare an emergency; and the captain did so; then ran a checklist (I'm assuming air data computer failure) and said that we needed to land at nearest suitable; and that we were already on our way there. Upon declaration of the emergency ATC started us directly toward the localizer for 6R; which we had already planned for; and I was realizing that I may have to do a raw-data ILS from the isi--not good-- and that it was gusting to 30 on the ground and that this was probably going to get ugly. I told the captain my worries; and he decided we should try putting the source selector over to air data computer 2; just to see what would happen. I agreed; we couldn't actually lose any more information as it was. When he selected ADC2; I got all my information back except for airspeed; that indicated 40 KIAS. But my pfd's information matched the isi's and I had enough information to fly the ILS safely; I felt. At that point; ATC asked for souls on board and fuel; and the captain stated that we had gotten some of our instrumentation back and thus no longer needed to be treated as an emergency. I had to work to get down because we were high and joining the localizer; about 35 miles out. The winds were about 60 KTS from the left; and then they swung to about 40 KTS from the right; but on the ground they were only about 15 KTS at that time; I think. I slowed early so I would have extra time to be stabilized and make corrections; and we broke out around 4-5 miles out; where I flew the remainder of the approach visually. The landing and taxi-in were without incident. A contract mechanic on the ground later found water in the pitot-static drains.

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Original NASA ASRS Text

Title: A CRJ-700 Flight Crew encountered multiple anomalies associated with an ADC compromised by water ingestion.

Narrative: I had slowed back to .75M because we were navigating around/between thunderstorms. Our destination was reporting winds gusting to around 30 KTS and ceilings at 1800 FT. I decided to brief early in cruise because we were in a relatively smooth patch of air and it looked like the descent was going to be bumpy. We briefed/set up for the ILS to 6R and I believe that somewhere around that time; we got our first Master Caution 'ding.' The Caution text extinguished immediately; though; and I don't believe I even had a chance to read it before it was gone. I HAD noticed; however; that I kept getting slow and was adding power often to maintain our Mach. Sometime soon after the first Master Caution; we got a second; again quickly extinguished; but this time not before I saw an 'EFIS Comp Mon' message. We checked our heading indicators because that's what we're used to seeing with EFIS Comp Mon; but everything was matching. Then we got a Mach Trim Master Caution. The Captain ran the QRH; but I was busy figuring out that I was adding power too often for a .75 cruise; and when the EFIS Comp Mon went off again; I had already noticed that; while I was maintaining .75 beautifully on MY PFD; I was passing through .80 to .81 on my captain's instruments and the ISI (Integrated Standby Instrument). I made corrections; told the captain; and this time; when the EFIS Comp Mon came on--and stayed on. I also had an airspeed flag. I want to say we got a Stall Fail caution at this point as well; but I don't really remember exact chronology. I believe at this point the plane started making small rolling motions; but rapid; and I turned off the autopilot and requested that the Captain get us clearance out of RVSM. (somewhere during all of this; we had descended down to F330). He requested lower; and I began hand-flying the step down while he ran the QRH for a stall fail first; then the EFIS Comp Mon. My airspeed indicator was winding down 40 KIAS; but I kept the FD on for the heading guidance while flying pitch for vertical speed and airspeed off the Captain's PFD and the ASI. Somewhere along the way; the Captain completed the EFIS Comp Mon checklist and switched the air data source selector to ADC 1. I now had airspeed indications back on my side; but I was still hand flying. Because we had filed 'nonstandard routing;' we were not filed on an arrival; but rather direct to the airport. On the descent; while the Captain was running a checklist--not sure which--we were given direct to a VOR for an arrival. I was still hand flying; and the airspeed I was getting from ADC 1 was decaying while the ISI airspeed was not; and I did not want to mess with navigation in addition to hand flying. I told the captain how I felt; and he made a call to ATC that we had lost some of our instrumentation and would like vectors. Somewhere right around then; every indicator on the PFD flagged red; and I believe a number of master cautions went off; but I'm not sure. I expressed my desire to declare an emergency; and the Captain did so; then ran a checklist (I'm assuming ADC failure) and said that we needed to land at nearest suitable; and that we were already on our way there. Upon declaration of the emergency ATC started us directly toward the localizer for 6R; which we had already planned for; and I was realizing that I may have to do a raw-data ILS from the ISI--not good-- and that it was gusting to 30 on the ground and that this was probably going to get ugly. I told the captain my worries; and he decided we should try putting the source selector over to ADC 2; just to see what would happen. I agreed; we couldn't actually lose any more information as it was. When he selected ADC2; I got all my information back except for airspeed; that indicated 40 KIAS. But my PFD's information matched the ISI's and I had enough information to fly the ILS safely; I felt. At that point; ATC asked for souls on board and fuel; and the Captain stated that we had gotten some of our instrumentation back and thus no longer needed to be treated as an emergency. I had to work to get down because we were high and joining the localizer; about 35 miles out. The winds were about 60 KTS from the left; and then they swung to about 40 KTS from the right; but on the ground they were only about 15 KTS at that time; I think. I slowed early so I would have extra time to be stabilized and make corrections; and we broke out around 4-5 miles out; where I flew the remainder of the approach visually. The landing and taxi-in were without incident. A contract mechanic on the ground later found water in the pitot-static drains.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.