BA038 (B777) Thread

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Dear Oluf,

Having re-read our May 1st and 2nd exchanges i can see (as i did then) your point regarding core icing. Although i keep several options open to the cause of the BA038 accident, the AAIB reports so far reveal no indications that engine icing is suspected. The AAIB specifically stated in the S3/2008 bulletin, released in May (after our exchange), that there was no evidence of core engine icing and that the reduction in thrust on both engines was the result of reduced fuel flow and all engine parameters after the thrust reduction were consistent with this.

To my knowledge, if an engine rollback was caused by core icing, EGT would have increased (with fuel flow required available). Quoting the article on "High Altitude Engine Flame-Outs":

"Incident investigators using data from DFDRs found that the uncommanded thrust reductions were manifested initially by a gradual decay in fan rotation speed and a final stabilization of the engine at a sub-idle operating condition. The engine speed decay was also associated with an increase of turbine gas temperature and a failure of the engine to respond to movement of the throttles/thrust levers. The term "rollback" has commonly been used to describe this condition."

The recorded engine parameters, according to the AAIB, do not show high EGT readings consistent with possible core icing. However, not ruling anything out before the cause has been substantiated by facts, could BA038 have flown anywhere near thunderstorm anvils along its route that day, possibly accumulating ice consistent with what has been described in the mentioned article? I assume the AAIB will have looked into that possibility?

I do not rule out your theory. Although the rollbacks occurred at low altitude, ice accretion could have commenced at high altitude near TOD, keeping compressor temperatures low enough during the CDA for more ice to accumulate at lower altitudes. If so, the recorded engine parameters revealing the contrary, will have to be explained.


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