HC, add to that no increase in MRGB temperature when the oil cooler bypass switch was finally activated after 77 seconds from the master caution annunciation, something that IMO should have been a memory requirement.
In the PF's defense there was clearly secondary indication missing information from the RFM on land immediately when the master caution alarm was activated i.e. no MRGB lube oil temperature increase should have been stated as a sign of loss of lube oil in the RFM and not just a reference in the PTM.
At 0948:32, there was continued reading of the procedure, stating that the temperature should increase following activation of the bypass. Shortly thereafter, the PNF mentioned that the oil pressure should stabilize or fluctuate in the range of 5 psi to 25 psi and that the temperature would slowly increase into the red zone. At this point, the PF pointed out that the MGB oil temperature did not increase following the activation of the bypass switch as indicated in the RFM. The PF then reiterated that he believed their indications were related to a sensor malfunction. The pilots did not discuss the fact that the oil temperature was not behaving as expected with the bypass activated.
So did the PF believe that 2 pressure sensors and the temperature sensor all failed at the same time? And if it was a pump failure why did the second pump not deliver pressure albeit churning? So now we have 2 failed pumps, 2 failed pressure sensors, and 1 failed temperature sensor in a A/C with no run-dry time.
A radio discussion began with one of the senior company pilots that had proceeded to the Cougar dispatch centre to see if the crew of CHI91 required any additional assistance. During that communication exchange, the PF indicated that he suspected they had experienced a pump failure. This assessment was based on the fact that while the oil pressure indicator was at zero, the oil temperature indication had not increased and was still indicating normal operating temperatures. It was also indicated that they were headed directly for the closest landfall, in the event that the situation would deteriorate. The pilot in the Cougar dispatch centre acknowledged the information and added that the temperature would increase if the MGB oil bypass switch was selected. The PF acknowledged. The pilot in the Cougar dispatch centre then suggested that they review the emergency descent and ditching checklist to ensure that they would be ready for that eventuality.
Why did the PF not discuss further the key issue regarding the lack of increase in temperature indication with the senior pilot at Cougar dispatch? He had already confirmed that the bypass switch had been activated.
The pilots misdiagnosed the emergency due to a lack of understanding of the MGB oil system and an over-reliance on prevalent expectations that a loss of oil would result in an increase in oil temperature. This led the pilots to incorrectly rely on MGB oil temperature as a secondary indication of an impending MGB failure.
To me the TSB should have went further on this key issue and stated that SAC had not included MRGB temperature indication not increasing with oil cooler bypass switch activated as a key secondary indication of MRGB lube oil loss and failure of the oil cooler bypass switch to prevent further oil loss thus requiring a land immediately condition. Surely the lube oil temperature reading ambient would have been observed during the initial MRGB certification trials during the true run-dry test?
The captain's fixation on reaching shore combined with the first officer's non-assertiveness prevented concerns about CHI91's flight profile from being incorporated into the captain's decision-making process. These breakdowns in crew resource management contributed to the selection of an unsafe flight profile
I don't agree with this statement, the PF had incomplete and falsely depicted information, the RFM was flawed and therefore so were the checklists and emergency procedures.
So I blame SAC, FAA and TC for causing so many fatalities. This is what I suspected all along, the TSB just confirmed it for me.
Safe flying
Max