From the above accident report:
After an uneventful take-off and climb the crew suddenly heard an unusual noise, accompanied by vibration, as the aircraft passed through FL 283. The noise was heard in the cabin as a series of thuds and the FDR indicated that it was directly associated with the stalling of the fan and/or the LP compressor with attendant surging of the No 1 engine. In addition to the noise and vibration, the lateral and longitudinal accelerations recorded on the FDR were consistent with the reported lower frequency shuddering that was sufficiently marked to shake the walls of the forward galley. Very soon after the onset of these symptoms there was a smell of fire and possibly some visible smoke in the cockpit. This combination was interpreted by the pilots as evidence of a serious engine malfunction, with an associated fire, and appears to have driven them to act very quickly to contain this perceived condition.
Neither pilot appears to have assimilated from the engine instruments any positive indication of malfunction but subsequent tests showed the engine instrument system to have been serviceable and there was no evidence to indicate that it did not display the large engine parameter variations that occurred when the compressor surged. The FDR showed four distinct excursions in N1 on the No 1 engine, with a 6 second period of relative stability between the second and the third.
Throughout the period of compressor surging the No 2 engine showed no parameter variations but because the first officer was unable to recall what he saw on the instruments, it has not been possible to determine why he made the mistake of believing that the fault lay with the No 2 engine. When asked which engine was at fault he half formed the word 'left' before saying 'right'. His hesitation may have arisen from genuine difficulty in interpreting the readings of the engine instruments or it may have been that he observed the instruments only during the 6 second period of relative stability between the second and third surges. However, any uncertainty that he may initially have experienced appears to have been quickly resolved because, when the commander ordered him to 'THROTTLE IT BACK', without specifying which engine was to be throttled back, the first officer closed the No 2 throttle.
The commander said that he gained from the engine instruments no clear indication of where the trouble lay. He had, however, disengaged the autopilot 8 seconds after the first compressor surge and most of his attention thereafter would probably have been on the handling of the aircraft and the flight instruments. The fact that when the aircraft rolled to the left he made no corrective movements with the flying controls appeared to indicate that he did not detect from the behaviour of the aircraft any loss of thrust from the No 1 engine. After the accident, he stated that he had judged the No 2 engine to be at fault from his knowledge of the aircraft air conditioning system. His reasoning was that he thought the smoke and fumes were coming forward from the passenger cabin; the air for the cabin came mostly from the No 2 engine; therefore the trouble lay in that engine. Whilst this reasoning might have applied fairly well to other aircraft he had flown, it was flawed in this case because some of the conditioning air for the passenger cabin of the Boeing 737-400 comes from the No 1 engine. In any case, his assessment was not supported by the evidence because the fumes had been perceived in the cockpit, and it was not for some time that he was able to confirm from the flight service manager that there had also been smoke in the passenger cabin. It seems unlikely that in the short time before he took action his thoughts about the air conditioning system could have had much influence on his decision. It is considered to be more likely that, believing the first officer had seen positive indications on the engine instruments, he provisionally accepted the first officer's assessment.
The speed with which the pilots acted was contrary to both their training and the instructions in the Operations Manual. If they had taken more time to study the engine instruments it should have been apparent that the No 2 engine indications were normal and that the No 1 engine was behaving erratically. The commander himself might have had a better chance to observe these abnormal indications if he had not disengaged the autopilot but this action by itself should not have prevented him from taking whatever time was necessary to assimilate the readings on all the engine instruments. In the event, both pilots reacted to the emergency before they had any positive evidence of which engine was operating abnormally. Their incorrect diagnosis of the problem must, therefore, be attributed to their too rapid reaction and not to any failure of the engine instrument system to display the correct indications.
If I remember correctly, BA's 737-400s (G-DOC*) were delivered with the non-solid state EIS displays as a consequence of this crash.
Your bone's got a little machine