737 MAX Flight Crew Operations Manual
Flight Management, Navigation -
FMC Messages
MN-FLT-OH-201
11.60.13
ALERTING MESSAGE
CAUSE
CORRECTIVE ACTION
UNABLE YYY KTS AT
XXXXX
Next waypoint speed
restriction (speed YYY,
at waypoint XXXXX)
cannot be met.
Modify flight plan as
required.
Clear the message.
UNABLE REQD NAV
PERF–RNP
(U13 and later)
FMC actual navigation
performance is not
sufficient for the
displayed RNP.
1B402 - 1B786, 1B807 - 1J594
UNABLE REQD NAV
PERF-RNP
message will be
displayed if there is a
divergence between
IRU-L and IRU-R
inertial altitude, or
between IRS-L and
IRS-R inertial vertical
speed, when the aircraft
is on an RNP-AR
approach leg.
Refer to UNABLE
REQD NAV PERF-RNP
non-normal checklist in
the QRH.
Note: When on a
procedure or airway
without an RNP alerting
requirement, the FMC
Navigation Check
supplementary
procedure in SP11 can be
used to verify position.
1B402 - 1B786, 1B807 - 1J594
If a UNABLE REQD
NAV PERF-RNP is
shown during the
RNP-AR approach,
whether the lateral or
vertical RNP are
exceeded or not, do the
Go-Around and Missed
Approach Procedure
unless suitable visual
reference is established
and maintained.
March 1, 2021