B-9 Page 2 of 4
MN-FLT-OH-201
Flight Crew Operations Manual Bulletin No. GOT-9 R1, Dated November 17, 2018 (continued)
In addition, operators have reported several situations when aborted engine starts
were needed in order to avoid exceeding the EGT start limit. These situations
occurred when the OAT was 40°C / 104°F and greater, and were not dependent
on a cold or warm engine. This situation is related to separation of the
Environmental Barrier Coating (EBC) in the engine core. When the EBC
separates, the clearance between the turbine and the engine core is increased and
therefore turbine efficiency is reduced. This reduction in turbine efficiency
increases the likelihood of exceeding EGT during engine starts.
EEC software 6.5 adjusts the logic for the engine Transient Bleed Valve (TBV)
schedule to reduce peak EGT during engine starts in both of the above
conditions. Installation of EEC software 6.5 is available via Service Bulletin 737-
73-1019. Airplanes equipped with EEC software version 6.5 or newer do not
need the procedures outlined in this bulletin.
Operating Instructions
In coordination with engine manufacturer CFM International, Boeing
recommends the following engine start procedure to be used when the OAT is
40°C / 104°F or greater.
Do the Engine Start Procedure except after the air conditioning PACK
switches are set to OFF, continue with:
ENGINE HYDRAULIC PUMP switches. .......................................... OFF
Start sequence............................................................................. Announce
Call “START ____ ENGINE”
ENGINE START switch .................................................................... GRD
Verify that the N2 RPM increases.
After MOTORING indication blanks, N1 rotation is seen, and N2 is at
maximum motoring and a minimum of 20% N2.
Note:
Maximum motoring occurs when N2 acceleration is less than
1% in approximately 5 seconds.
CAUTION:Do not apply rotational force when moving the engine
start lever.
Engine start lever.....................................................................IDLE detent
Continue with the Engine Start Procedure.
When the first engine is stable at idle, start the other engine using the same
procedures outlined above.
After both engines are stable at idle:
March 1, 2021
