2010-02 · NASA ASRS report 876161
A Captain and First Officer report about losing both Flight Directors on their B757-200 during initial climb going into IMC conditions. The First Officer; who was the Pilot Flying; noticed his Airspeed roll back to 110 knots; his Vertical Speed Indicator showed 500 feet per minute (FPM) down and the Altimeter frozen at 5;300 feet. A cabin pressurization problem also developed at 10;000 feet.
During takeoff roll; with the First Officer (F/O) as Pilot Flying (PF); shortly after the 80kts call; I noticed the F/O's Airspeed needle seemed to be lagging. I did not think this warranted a high speed abort; as all other indications appeared normal; with no EICAS warnings. Rotation was normal; but during initial climb; the F/O's Airspeed; Vertical Speed Indicator (VSI); and Altimeter were giving erroneous indications; compared to mine and the standby instruments. We also lost both Flight Directors. After the Flaps-Up call; the F/O transferred aircraft control to me. I engaged the Autopilot at about 8;000 feet MSL; and at some point the Flight Directors came back on. We then got an EICAS Mach Speed Trim and Rudder Ratio message; along with associated lights on the Overhead Panel. At this point the F/O's Pitot Static instruments were completely failed; and we suspected an Air Data Computer (ADC) failure. ZZZ Departure was very helpful in giving us vectors; and eventually holding at XYZ VOR; as we were not sure at that point whether we were going back to ZZZ. We contacted Dispatch and Maintenance Control; and after consultation we switched the First Officer's (F/O) Air Data to Alternate; at which time his instruments were fully restored. After evaluating weather; fuel; and aircraft condition; we all concurred that the safest course of action was to continue to ZZZ1. I gave the Purser a cabin advisory; and subsequently advised of our decision to continue. I also advised the passengers. The flight continued normally to ZZZ1. During discussions with Maintenance Control; we learned that Maintenance had worked on the Standby Instruments and ADC the previous evening. I would like to find out the reason for the failure.
I was the Pilot Flying (PF) and as we rotated; both Flight Directors disappeared. We were given a turn to 030 and at 400ft I initiated the turn. That is about the same time we entered IMC conditions. I saw my Speed roll back to 110 KTS and my Vertical speed showed 500 fpm [feet per minute] down. I lowered the Nose to 10 Aircraft Nose UP and cross checked my instruments. My Altimeter was 5;300. None of this made sense so I looked at the Standby and Captain's instruments and they show us climbing slightly and accelerating through 220 KIAS. I called for Flaps-Up and disregarded my instruments; other than the Attitude Director Indicator (ADI). The Captain had full instrumentation so we transferred control to him. He leveled off at 10;000 and we told ZZZ we needed to work on an issue. We had a Rudder Ratio and Mach/Speed Trim EICAS. All my Pitot/Static related instruments were frozen except Air Speed Indicator (ASI) which showed bottom of the scale. I sent Dispatch a message to call me and asked for Maintenance Control to be on line. Dispatch came back with a frequency; but we could not hear each other. After a couple of tries; we got a conference call going; ran all the appropriate Checklists and Abnormal Procedures; and discussed returning to ZZZ. The weather was going down and we were now limited from Autolanding or crosswinds over 15 kts. After confirming we had instrumentation in Air Data Alternate; the Captain; Dispatch and Maintenance Control decided that it was good weather all the way to ZZZ1; and the weather there was better. After re-looking at all the numbers including fuel burn; weather; et cetera ..we continued on uneventfully to ZZZ1. We wrote up the fact that I slightly exceeded the Flap 5 speed while ascertaining what data was correct.
Reporter stated the weather was like a misty fog after Takeoff and initial climb; but did clear after. He noticed the First Officer's Altitude was frozen at 5;000 feet and his Airspeed at Zero KTS. They also had a pressurization problem develop at about 10;000 feet; which seemed to go away after the First Officer switched his Air Data to Alternate.Reporter stated Maintenance later informed him the # 2 Air Data Computer (ADC) was changed.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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