There, there, don’t get too excited … sounds like a commercial for insurance, but that is exactly what a stick shaker system is. It is an alert to an unusual condition; more forceful than a call from the NFP, like a friendly poke in the arm giving the handing pilot additional awareness or, if necessary, a wakeup call.
As described earlier most SS systems alert at approx 1.1Vs, but with even earlier alerts for applied load factor (g) and high pitch rate, the latter features are available from alpha and alpha rate. Depending on aircraft type and SS system, the SS alert may be over sensitive to certain turbulence conditions, gusts, or even sideslip. Thus, providing recovery action is initiated there isn’t very much to get overexcited about, you still have 10% of stall speed as a margin.
We must wait for the details of this event, but bearing in mind that the certification and operational requirements of the aircraft require maneuvering close to the boundaries of alerting systems we should not be surprised if occasionally the limit is encountered. A max rate go-around could generate 1.25g, although most GAs are much less. This g level equates to an increase in the stall speed and corresponding SS speed to values not far from the normal GA speed Vref (1.3Vs) e.g for 100kt Vs x SQR 1.25g =111 kts. For a GPWS pull up crews should be taught to aim for 1.3 g, similar for ACAS until the maneuver is established. For a Windshear encounter crews are taught to fly ‘at’ but to respect the stick shake speed i.e. just short of an alert.
It would be disappointing for the industry if this crew were suspended for what appears to be a benign event; crews have enough stresses without the addition of such action. I detect an unhealthy trend in the industry where managers suspend pilots for the most minor of events (even good GAs); possible this is due to the continuing good safety record and there are fewer serious events to investigate. However this management attitude does little to maintain an open reporting and ‘just’ safety culture, nor does it encourage crews to fly near to limiting speeds when demanded by procedure or warranted by crew judgment.
Let us wait and see what actually happened during the GA.