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Old 11th Jan 2021, 07:55
  #170 (permalink)  
fdr
 
Join Date: Jun 2001
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infrequentflyer789

XL888T, the A320 event into the water south of Perpignan had more to do with attempting to conduct a flight test data point without following a test flight plan. The test point was missed in the upper air work and was added ad hoc without proper setup for system monitoring, which precluded the flight crew from detecting the faulty AOA probes. Had the test been conducted IAW the test plan, the error would have been detected early. With the decision taken hastily to complete the test point at a low level, and without reference to the procedure in the test plan, then the crew were left with just their wits to ascertain that the system was not behaving correctly. As it was, they slowed down and went straight through multiple conditions that were displaying incorrect system behavior. In the end, the stall event, roll instability, and thrust increase related THS trim error (THS did not stop trimming at the correct point in decel due to the AOA fault, failure to recognize that (checklist response to be noted....) oversight of "USE MANUAL TRIM" when the ELACs finally gave up the ghost... Not monitoring the AOA on the maint page.... etc.

It is human nature to shortcut processes and procedures, but any time that is done in an aircraft that is near an operational boundary, or thereafter can approach an absolute limit, it is necessary to ensure that the process is well thought out beforehand, and a full safety analysis conducted of each aspect of the plan. There is an assumption of goodness in functional check flights FCF's conducted for maintenance purposes, that they are just box-ticking, and that anyone can go do that, particularly if they are.... a training captain, an examiner, a manager, a [choose your position]. The hard truth is that FCFs have a disproportionately high catastrophic loss rate, and often that is the result of a lack of preparedness of the crew for what they are about to do. If the crew has not considered every test point as a unique hazard, then they are just filling the seats and not managing risk. You don't have to be Yaeger, or an NTPS, EPNER, ETPS, USNTPS, or USAFTPS graduate, but the crew need to know what steps are necessary to conduct a test flight appropriately, be able to read, and to know that when they deviate from the plan, they are potentially in a bad place, and better be on top of their Chuck Yaeger zen side on the day. Even then, the competent, well-trained crew can still mess up, where the task is considered inadequately, as in a Challenger loss, a GeeWhiz loss, an A330 loss, where on reflection the test points were not thought out fully.

FWIW, the baby Boeing is not a. bad little airplane and is generally honest. The rudder single control valve was not pretty, the wing was a cost-effective compromise to get enough CL out of it, but, it is generally honest. It stalls nicely enough, and the high-speed characteristics are OK, although watching the ailerons buzz between MMO and MD is not a pleasant part of its envelope. Boeing made an OK aircraft, and the majority of the losses speak to crew loss of SA up to the Max debacle. The type is over-represented in overruns of airports and as the methods to radically improve V speeds and reduce the risk are established, that should someday be resolved. It is not one of my favorite Boeings, but then dealing as an owner with TBC is enough to affect impressions of the type.
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