Originally Posted by
procede
Where the comparison with the 747 flap system goes astray, is that the folding wing folds in the direction of the main force (up) where the track system folds in the direction of the wing cord (and down). The flap system thus needs less safety measures to stop it from extending or retracting due to aerodynamic forces.
A few points:
1. The wingtip only folds/unfolds on the ground. The flaps MUST extend and retract in flight.
2. The wingtips only have two positions. The flaps have multiple positions.
3. The wingtips each have four simple lock pins to lock them in place and are fail safe (if they fail, they fail locked). The flaps have multiple failure modes, and not all are fail safe.
4. The wingtips can fold/unfold assymetrically with no concern. The flaps MUST extend and retract symmetrically, requiring complex sensors and redundant controls to ensure this ALWAYS happens.
5. The wingtips each have a simple single rotary actuator. The flaps have multiple segments and multiple actuators
6. The wingtips have a very simple rotary motion. The flaps have a complex motion that includes translation and rotation.at constantly varying ratios which requires a complex track/link system.
7. The wingtips are structurally and aerodynamically simple and if one or both wingtips are lost in flight the aircraft remains fully controllable. The flaps are much more complex structurally and aerodynamically. Lose a flap in flight and you're screwed.
8. The wingtips only need to fold to taxi off the runway and/or fit into a gate, so the consequences of a failure to fold are minor and at most an annoyance. The flaps need to extend to land and the consequences of a failure to extend are much more serious.
9. The wingtips unfold on the ground before becoming airborne so if there's a problem you know about it well before you even commit to flight. The flaps retract AFTER takeoff and MUST retract to continue the flight. If they fail to retract the flight must be aborted.
10. There's more, but this will suffice.
I'll let the reader decide which system is "safer", "more complex", "requires more safety measures", etc