There are two rules applicable to the 737-800 aircraft in order to conform to
trim requirements.
Rule 1: For a passenger count of 177 or less, Rows 3 and 4 are usually blocked off.
With average loads on the 737-800, trim problems may arise. However, to allow for free seating, balance limits are tighter in this system and, with certain load profiles, load planning is vital to ensure that limits are not exceeded and reloading required as a consequence. Accordingly Loading Rule 2 is often employed to ensure the flight remains within the trim limits.
There are two rules applicable to this aircraft in order to conform to
trim requirements.
Rule 1: For a passenger count of 177 or less, Rows 3 and 4 must be
blocked off at all times. (Rows 3 and 4 comprises 6 seats A-F incl.)
Some airlines’ policy is to block off rows 3 and 4.
Rule 2 allows the aft limits at ZFW and TOW balance units to be subtracted
by .4 units and added to the forward ZFW and TOW balance units for both
Scheduled and Charter flights PROVIDED (a) No passengers seated in the forward 6 rows and aft 4 seat rows, with a maximum of 132 passengers, or (b) 178 or more passengers carried.
This rule can be used in case “a” above as cabin crew will be able to direct
passengers away from restricted seats when the load is low.
It is helpful to think of these rules in terms of passenger capacity, as follows:
a.) Passenger load < 177..... Rows 3 & 4 should be blocked off at all times.
b.) Passenger load > 178.....all cabin seats may be used. Trim may be adjusted
by 0.4 units at either end if required.
c.) Passenger load < 132......Trim may be adjusted by 0.4 units at either end if
required, subject to front 6 and aft 4 seats being blocked off.
When the aircraft is well under it’s capacity, passenger seating is generally limited to the central part of the aircraft as to help insure the aircraft is within its operating C/G limits.