I was told and teached how to recognise and avoid such an event. (and yes I did practice stall-recovery-procedures in many types)
Sorry, but 3 pairs of eyes could and should have seen/scanned/observed the (negative) speed-trend!
And as an instructor you know this kind of flights and (for me) you are more "on-the-ball".....just my few cents
testpanel, spot on!
Difference between the signs of an approaching stall versus symptoms of the full stall.
First sign of an approaching stall is decreasing airspeed, reduced control effectiveness and (often but not exclusively) high nose attitude.
This is all basic but perhaps we should also recall that whilst on approach in a swept wing jet transport the speed is below minimum drag speed. So if speed decreases, drag increases ergo more speed decrease! So even if approach power is selected you can't ignore a speed trend. And if the speed gets very low then full power will not overcome the high drag so you have to lower the nose to get some speed on but you need some height to so this.