B757 flight crew reports a go-around at their destination due to windshear and a subsequent diversion to their alternate. Airspeed indication anomalies prompt the crew to declare an emergency enroute while ACARS messages from the Dispatcher are reported as very distracting.
Synopsis
B757 flight crew reports a go-around at their destination due to windshear and a subsequent diversion to their alternate. Airspeed indication anomalies prompt the crew to declare an emergency enroute while ACARS messages from the Dispatcher are reported as very distracting.
Narrative
We flew through a break in a line of thunderstorms with the intent of getting on the north side of the line and landing north at our destination. The line of weather closed off the approach course so we started positioning for landing to the south with a 4 KT tailwind. The wind suddenly shifted out of the west gusting to 32 KTS. I decided to try the VOR approach on another runway. At around 400 FT we received a windshear warning from the rapidly approaching storm front. Executed a go-around with a immediate right turn to north. The weather rolled over the field and the parade of thunderstorms precluded wasting any time attempting to hold. Diverted to our alternate. IMC. Real bouncy ride; St Elmo's; lightening; moderate to heavy rain with TAT well below 10 degrees Celsius. The First Officer's airspeed indicator and the STBY indicator started fluctuating wildly. Rudder Ratio and Mach Speed Trim EICAS messages also briefly displayed. Declared emergency due to the airspeed indication issue. Landed without incident.
Second reporter narrative
Cleared for the approach and landing we received wind shear advisory and noted increasing performance with associated increase in speed. Because of increase of airspeed; aircraft was not in position to land and we elected to go around. Conditions at field were too severe and we decided to go to our alternate. In climb as pilot monitoring I was very busy with the short trip to our alternate; communicating with ATC; retrieving weather from new destination and normal clean up and climb checklist. Our alternate is an airport we both were unfamiliar with and I was busy getting charts ready for our new destination. I made diversion report to dispatch with our ETA noted. Immediately was questioned by ASARS message requiring acknowledgement of our new destination. I responded with confirmation. Almost immediately was questioned again with a request that we consider holding and new approach; this also with a requirement for acknowledgement. After discussion with the Captain I responded NO. Within just a couple of minutes a third ACARS wanting to know the ETA; into the trip from our go-around to the alternate and while I was working on diversion plans; approaches; weather and ATC communications I noted the First Officer's airspeed decreasing to between 100 and 120 KTS for no apparent reason. Standby matched the right side with an upper EICAS message of Mach Speed Trim and Rudder Ration warning. We were in IMC and in icing at the time. The Captain declared an emergency. Emergency checklist was added to the workload and a safe landing was accomplished. While I understand the work of dispatch is to accomplish the mission of our flight and to arrive at the intended destination I am very bothered by the interference during an obviously busy phase of flight. The continual questioning of our decision and the fact that dispatch kept prodding and bothering us could have led to a very dangerous situation. Because my attention was continually taken from the situation trying to comply with Dispatch's repeated questions I was distracted to some degree when the unexpected did happen and we had a real emergency. I would prefer that dispatch help the crew with the decision they make and not interfere just to ease their own workload. Incidentally the choice of our alternate was not a good one by dispatch as they were not prepared for a 757. In fact we were questioned by station personnel when we landed as to what type of aircraft we had; they obviously had not been told what to expect. We were lightly loaded and could have easily been given proper fueling for our original destination. After we elected to go-around; a following 737 diverted immediately to another airport. In the 20 years that I have been with this air carrier; I can only think of 3-4 times that I have been on the crew that diverted and I can only remember maybe half a dozen times that we even had to go-around. These decisions are made by crews and made with years of experience and knowledge. It is frustrating to me as crew member to continue to be second guessed to the point of producing a dangerous situation.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.