forget, hello,
placard flap speed for flap 30 = 175kias & for flap 40 = 162kias ( b738ng)
boeing manual says: when flaps are set at 40, the TE flaps:
-retract to 30 if speed exceeds 163kias & re-extend when speed is reduced below 158kias. when flaps are set at 30, the TE flaps:
-retract to 25 if speed exceeds 176kias & re-extend when speed is reduced below 171kias. so in both cases a difference of 5 kts exist between retraction/extension, which may seem small. but when exceeding the placard speed the aircraft is still probably accelerating a bit & then to decelerate again about 5 knots, definitely requires pilot intervention & will take more than "momentarily" to achieve, so you will definitely take notice. those flaps just don't retract/extend as windshield wipers.
kind regards,
bm,
