Beware clear-air turbulence

Was hearing a lot of people saying that Singapore Airlines shouldn't have been running a meal service when it recently encountered severe turbulence resulting in one death from a heart attack and quite a few people in hospital including some severely injured. How has Singapore Airlines responded?

SIA will shortly put all-inclusive safety measures in place. Previously, only hot beverages and soup were prohibited from being served and service may continue at the crew's discretion. Meal service must now be totally stopped when the seatbelt sign is activated.

Similar to how airport security is sometimes described as security theatre, it seems to me that this might simultaneously be described as mostly being safety theatre (though nonetheless not a terrible policy to put in place). Would it have helped in this situation? According to the timeline on Wikipedia:

07:49:21 UTC
First trace of turbulence was first encountered
07:49:32 UTC
"one of the pilots called out that the fasten seatbelt signs had been turned on" (not sure if this means a cabin announcement but sounds like the passengers would have seen the seatbelt sign turn on and probably some audible notification of that).
07:49:40 UTC
-2.8G change in vertical acceleration over 0.6 seconds
07:49:41-45 UTC
Vertical acceleration changed to +3G over 4 seconds
07:50:05 UTC
Autopilot re-engaged (after manually flying for 21 seconds)
07:50:23 UTC
Autopilot finished returning the flight to the selected altitude.

i.e you basically have 19 seconds from the first trace of turbulence to things going completely haywire, (and the flight returned to "normal" in about a minute). Even if the flight attendants had immediately started running as fast as possible to lock down the meal carts as soon as the first trace of turbulence sit I'm pretty sure they wouldn't have made it. I'm not opposed to stopping meal service on planes during turbulence, but doubt it would have done much here.

The thing to be aware of is clear-air turbulence. Per the description:

Clear-air turbulence is usually impossible to detect with the naked eye and very difficult to detect with a conventional radar, with the result that it is difficult for aircraft pilots to detect and avoid it. However, it can be remotely detected with instruments that can measure turbulence with optical techniques, such as scintillometers, Doppler LIDARs, or N-slit interferometers.

I'm not quite clear from doing a little poking around just how those things work, but it doesn't seem like any of them are included on current-generation commercial aircraft (and I have no idea how difficult it might be to adapt those to use to improve turbulence detection either).

For consider this a suggestion that one bit of advice you'll usually be given when taking a flight, i.e. to keep your seatbelt fastened as much as possible throughout the flight, is good advice to take. 11 seconds to go from the first trace of turbulence to a signal to fasten your seatbelt doesn't seem to me like a particularly unreasonable response time by the pilots.

Only so much that can be done when something like that happens though.

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