737 MAX Flight Crew Operations Manual
Flight Controls -
System Description
MN-FLT-OH-201
9.20.23
Flap Load Relief
Flap load relief protects the trailing edge flaps from excessive air loads. Flap load
relief is a function of the Flap Slat Electronic Unit (FSEU), which receives data
from the left Air Data Inertial Reference Unit (ADIRU). The left ADIRU is also
the source for the captain’s airspeed indication. When the captain’s indicated
airspeed is too high for the selected flap setting, flap load relief activates and
retracts the TE flaps to the next lower setting below the selected flap lever
position.
If the Captain’s airspeed is erroneously high, the flap load relief function can
activate and retract the flaps to the next lower setting from the flap detent selected
with the flap lever. In this case the desired flap position can be achieved by
selecting the next higher flap detent beyond the desired flap position. For example,
if the desired flap position is Flaps 30, select Flaps 40 and the flaps will extend to
the Flaps 30 position. This applies for all flap selections protected by flap load
relief.
When the flap load relief function activates, the FLAP lever does not move, but
the flap position indicator shows flap retraction and re–extension.
Flap load relief is available when flaps are selected to 10, 15,25,30, or 40. Flap
load relief is not available during alternate flap extension.
When the flaps are set at 40, the TE flaps:
• retract to 30 if airspeed exceeds 167 knots
• re–extend when airspeed is reduced below 162 knots.
When the flaps are set at 30, the TE flaps:
• retract to 25 if the airspeed exceeds 176 knots
• re–extend when airspeed is reduced below 171 knots.
When the flaps are set at 25, the TE flaps:
• retract to 15 if the airspeed exceeds 191 knots
• re–extend when airspeed is reduced below 186 knots.
When the flaps are set at 15, the TE flaps:
• retract to 10 if the airspeed exceeds 201 knots
• re–extend when airspeed is reduced below 196 knots.
When the flaps are set at 10, the TE flaps:
• retract to 5 if the airspeed exceeds 211 knots
• re–extend when airspeed is reduced below 206 knots.
March 1, 2021
