Originally Posted by
flightleader
I should have mentioned that I only flew the B737 classic for 10 years but I had 8 split flaps. It seems that when selecting a lesser flap after the split would not retract the flap immediately. But it would move to the selected lesser flap setting without any split after 2-3 minutes. Maybe it won't work on NG.
According to the maintenance guys, improper greasing of the flap mechanism can cause flap splits.
If I remember correctly on the Classic flap asymmetry protection is provided by the detection of needle split on the actual gauge and a “sticky” needle could cause an asymmetry indication which prevents further flap movement. As someone else has mentioned, tapping the gauge could free the sticky needle and restore normal flap operation and this is something many 737 Classic pilots will have experienced as the engineers first fix upon landing! “Percussion engineering” at its finest. From the NG onwards, asymmetry detection is provided by the Flap Slat Electronic Unit FSEU.