747 Flaps Secondary Mode

[tcasblue]

Hi,

Looking for clarification.

Just want to confirm that if the LED's have some sort of issue where they go into secondary mode, do the trailing edge flaps also go into secondary mode with the very slow movement. Also, under this scenario, do the trailing edge flaps go back into primary mode once the LED's are all fully extended.

Thanks

[MarkerInbound]

As I’m reading it, no.

“If a primary control failure occurs in either the inboard or mid span leading edge flap group, both groups switch to secondary mode. For all other flap groups, only the failed group operates in secondary mode.” It’s still “5 minutes to 5” because you won’t get the flaps 5 indication until all the LEDs are in position but the trailers will have been set for a while.

[tcasblue]

As I’m reading it, no.

“If a primary control failure occurs in either the inboard or mid span leading edge flap group, both groups switch to secondary mode. For all other flap groups, only the failed group operates in secondary mode.” It’s still “5 minutes to 5” because you won’t get the flaps 5 indication until all the LEDs are in position but the trailers will have been set for a while.

I have had trouble understanding that paragraph.

Looking at the FCOM section more closely, it appears that there are 8 groups of flaps. 6 are for LED's with three groups on each wing(inboard, mid-span, and outboard). There are two groups on the training edge(inboards and outboards).It appears if an inboard or mid-span goes to secondary mode, its symmetrical group on the other wing goes to secondary. Is that correct?

[bigduke6]

MI is correct. The TE flaps remain in primary mode and extend at the normal rate.

TB your last statement is correct. For LE flaps, the same flap group on the opposite wing also goes to secondary mode to try to prevent the rolling moment assocated with having them deploy quickly on one wing in normal mode and slowly on the other wing in secondary mode.