Thinking about Asiana flight 214, and anecdotal evidence of near misses on approach (stall) when autothrottle was believed to be active but was actually off, is it common to misunderstand the state of autothrottle, and is it easy to miss?
Answer by Thomas Zerbarini:
As you can see from your question in reference to the Asiana accident; yes it is possible for pilots to miss something. Although quite rare and unlikely it can happen. With improper training, distractions, complacency or other contributing factors errors are possible. That is why we train and re-train so much. It's why we have multiple pilots, checklists, flows, scans and many other mechanisms to establish checks-and-balances for safety.
Aviation Week did a good article summarizing the NTSB findings which included the main probable cause and the many contributing factors that caused the accident.
With these findings in mind, we can emphasis how important it is for pilots to be diligent and monitor the aircrafts performance and flight path at all times even when the auto-pilot is engaged. Now, professional pilots know this and it is engrained in us. Yet, complacency can be insidious which makes monitoring each other in the cockpit is so important.
Here is an image of a Boeing 777 Cockpit:
At the very top on the glare shield panel in the center is the Mode Control Panel MCP (auto-pilot panel). It looks like this:
On the MCP you'll notice on the left side the A/T (auto-throttle) switch light. This switch light is green when the auto-throttles are engaged. If you read the Aviation Week article I provided above you'll notice that the A/T system was engaged, so the green switch light would be green (on) and if the pilot did a quick scan would see that they were on. Due to the design of the system though, the A/T's were in FLCH "hold mode" and the low speed automatic response was inhibited. Thereby allowing the aircraft speed to deteriorate to a dangerously low speed. The fact that the pilot(s) did not recognize the dangerous low speed nor respond quickly enough is what the NTSB has highlighted as the primary blame for the accident.
Here is a great interactive (click on switches) website that describes the functions of the various controls on the MCP panel:
Thomas Zerbarini
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