CFM56-3 related:ATA 70-80 Powerplant chapters (excluding 78 Thrust Reversers)
CFM56-3 related:
1 - Borescope help: CFM56-3 HPC blades scaled 1:1 737-3/4/500
5 - Engine idle control, a clear explanation! 737-3/4/500
6
- Trimmen,
afstellen en controleren CFM56-3 (Dutch language)
737-3/4/500
7 - On-board balancing of fanblades. 737-ALL
10 - CFM56-3 sensor failure / system mis-rig guide 2, with illustrations. 737-3/4/500
14 - Transfer gearbox cracked mountings. 737-3/4/500
15 - CFM56-3 HPT blade and HPT nozzle pictures for borescope insp. help 737-3/4/500
16 - MEC trim sheets, for easy use when adjusting and testing the MEC. 737-3/4/500
17 - Relationship overview / calculator between different engine data (CFM56-3). 737-3/4/500
27 - CIT + T2 sensor test sheet, CIT sensor and T2 sensor testsheet. 737-3/4/500
28 - Idle control explained, -3 engine idle control system sheet. 737-3/4/500
29 - FANblade balance sheets, for fanblade registering, balancing and re-balancing purposes. 737-ALL
32 - Oil filter bypass lt flickering and egt counter flashing upon engine startup. 737-3/4/500
33 - Max power assurance check calculation file for 737 classic. 737-3/4/500
CFM56-7 related:
7 - On-board balancing of fanblades. 737-ALL
9 - CFM56-7 fanblade dovetail map: p/n, s/n and moment weight. 737-6/7/8/900
11 - Borescope help: CFM56-7 HPC blades scaled 1:1 737-6/7/8/900
13 - EGT indication problems CFM56-7 engines. 737-6/7/8/900
16 - ACCELL and MPA test NG tables, MPA and accell test tables. 737-6/7/8/900
18 - J-hook borescope inspection on CFM56-7: simplified procedure. 737-6/7/8/900
19 - Compressor and turbine pictures for borescope reference. 737-6/7/8/900
20 - Stage 1 booster vane assy outer shroud abradable coating damage. 737-6/7/8/900
21 - J-hook information page, for your J-hook inspection experience ! 737-6/7/8/900
22 - HMU partnumber matrix and EEC software info. 737-6/7/8/900
23 - New design Fan Blade Platform interchangeability. 737-6/7/8/900
24 - LPT frame coverplate oil leakage repair. 737-6/7/8/900
25 - AGB sealol assy replacement on IDG and fuelpump side. 737-6/7/8/900
26 - CFM56-7 static fluid leakages. 737-6/7/8/900
29 - FANblade balance sheets, for fanblade registering, balancing and re-balancing purposes. 737-ALL
30 - HMU schematic drawing for training only. 737-6/7/8/900
31 - Chip detector findings on cfm56-7. 737-6/7/8/900
33 - Max Power Assurance Check calculation file for 737 NG. 737-6/7/8/900
9- CFM56-7
fanblade dovetail map: p/n,
s/n and moment weight.
737-6/7/8/900
Sometimes it's difficult to find the correct numbers on the bottom of the fanblade dovetail. You may need them for balancing or administration purposes. The picture below explains the common used numbers on the blade and where they are printed. The other numbers are unknown for me so when somebody knows what they are, pls let me know.
13-
EGT
indication problems CFM56-7 engines.
737-6/7/8/900
As some of you know, the -7 engine has some EGT indication reliability issues. This is a known problem at the engine manufacturer, and they are working on a solution. During troubleshooting iaw FIM not all problems are found always.
If a fault message is found, check this message with previous occurences. Current solutions for the indication problems are:
Cleaning of the plugs (temp solution), and replacing the EGT harness.
14-Transfer
gearbox cracked mountings.
737-3/4/500
When you do an engine (general visual) inspection, pay attention to the mounting flanges of the transfer gearbox. It happened more than once that one or more of these mounting lugs where cracked. Also the bolt(s) can be broken. Some evidence of broken lugs, and therefore a TGB that can move a little, can be seen by oil traces coming from the driveshaft-coupling between the TGB and the AGB. Also metal parts found in the TGB/AGB chip detector (the fwd one) shows that damage occured and further investigation is necessary. See the 5 pictures below for more information.
18-J-hook
borescope inspection on CFM56-7: simplified procedure.
737-6/7/8/900
When performing CFM56-7B SB 72-0515 REV 3 (J-hook inspection or HPC stator-to-rotor contact), it can be difficult to make a decision based on the things you see through the borescope. The SB is very large and needs to be read several times to understand the contents. To make the inspections easier, this SB is now simplified in this document, together with some example photo's and clear explanations.
Link: SB 72-0515 J-hook inspection simplified
See also the dedicated
J-hook page in this chapter ! 
20-Stage
1 booster vane assy outer shroud abradable coating damage.
737-6/7/8/900
When you look in between the fanblades, through the first stage booster vanes of the LPC, you can see the outer shroud abradable coating. Especially at the 6 o'clock position you will certainly find damage to this coating. This damage looks like corroded aluminum, but it is a composite coating which is peeled and cracked, and may be missing untill certain limits. The damage starts at the 6 o'clock position and continues to the left and right side. The cause of this damage is not exactly known, but probably the damage starts when moisture accumulates at the lowest point, and when it freezes it will expand and therefore damage the coating. (If anyone has more info please let it know!) Many parts and chuncks are coming off. The inspection is stated in AMM 72-21-03 page 601 ff. There are the damage-limits of this outer shroud abradable coating. You can replace this splitter fairing on-wing iaw the same AMM chapter page 401 ff. See the pictures taken from such an assy, where the damage was present from the 3 o'clock till the 9 o'clock position. Note the many parts missing and the chunck of coating on the last picture.
23 - New
design Fan Blade Platform interchangeability.
737-6/7/8/900
Between the adjacent fan blades of the CFM56-7B engine, 24 Fan Blade Platforms, made of forged aluminum, are installed to provide an aerodynamic surface.
Recently, CFMI has introduced a new Fan Blade Platform design (p/n 340-001-814-0). The Fan Blade Platform design changes include:
-No life limitation
-New geometry with swaged bushings
-New material, aluminum 7449
-Shot-peening implementation
-Weight decrease (-36 grams)
-Bowl seal implementation on both sides (lip seal removed)
-No elastomer strips needed for weight balancing
The new Fan Blade Platform can be identified by a grey stripe on the aft edge of the platform surface (fwd looking aft).
Limited interchangeability;
The new design platforms weigh 36 gram less than the current design. Because of this mass difference, a single replacement of a current design platform (p/n 340-001-804-0, 340-001-805-0, 30-001-806-0, 340-001-809-0 of 340-001-810-0 ) by a new design
(p/n 340-001-814-0) will generate an unbalance equal to a momentweigth of approx 925 cm/g, which will result in engine fan vibration. Therefore, the current and new design platforms are only interchangeable as a complete set. However, to avoid any operational desruption due to lack of spares, the current design platforms can be replaced by the new design platforms only when installed in pairs (two platforms with the same reference, 180 'degrees apart).
Engine vibration levels must be within limits during the test run that has to be performed after this action. The new design Fan Blade Platforms are only one way interchangeable and can not be replaced by the current design platform.
This limited interchangeability information and the accomplishment instruction for Fan Blade Platform installation in pairs can be found in CFMI (CFM56-7B) SB 72-0353.
See pictures below for examples and differences between old and new design platforms.
24 - LPT
frame coverplate oil leakage repair.
737-6/7/8/900
When you find black burned oil spots on the inner aft side of the RH thrustreverser inner wall, and the hole on the oil tube on the turbine is covered with black coked oil deposits, you most probably have an oil leakage of your LPT frame oil inlet cover assembly. The oiltube itself is NOT leaking, but the leaking oil comes out of the hole above it , but it looks like the tube is leaking. In fact its a drain coming from the area under the oil inlet cover assembly. In this case, you have to remove the exhaust plug and sleeve, the cover plate and the oil inlet cover assy (looks like a crown).
Replace the o-ring and the gasket from this crown. See picture of this gasket, handle it very carefully it breaks even when you only look at it! Replace also other seals/gaskets on parts that where removed for access. See AMM 72-56-00 and IPC 72-56-01-01 for parts. Clean all coked areas, including this drainhole and the inner wall of the thrust reverser.
25 - AGB sealol assy replacement on IDG and
fuelpump side. 737-6/7/8/900
When you have oil leakage from the drivepad-drain of the IDG or fuelpump, most probably the sealol assy is leaking between the carbonseal and the mating surface of the rotating ring. When you want to solve the leakage, ALWAYS replace the complete sealol assy, replacing seperate parts is not correct and causes leakage again , not immediately, but after a few days of operating the aircraft.
The sealol assy is a matched assembly. If you mix components, oil leakage could occur again. See the caution in amm 72-60-00-400-802-F00 on page 2.
Even a rotating ring that looks very smooth and that looks not worn or polished can even cause a leak when not replaced.
When installing the rotating ring, make sure the notches are inserted in their respective openings on the drive shaft.
The picures below show a worn rotating ring and carbon seal. Note that the pictured seals where NOT a matched set as it should be. The carbon seal was only replaced 3 days before, but the rotating ring was not replaced.
The oil leakage can also be caused by deteriorated O-rings inside the carbon seal assy and rotating ring. This may be caused by the use of 2197 engine oil. This is still under investigation.
Improved O-rings (Viton GLT) are available in a sealol set p/n 305-115-709-0 as stated in CFM56-7B SB 72-0652. As a replacement set you can also use the magnetic set, p/n 305-102-301-0 or 305-102-303-0.
Sealol assy:
Removal AMM : 72-60-00-000-801-F00
Installation AMM: 72-60-00-400-802-F00
Fuelpump side (aft side AGB): IPC 72-63-00-03 item 90 p/n 305-115-704-0
IDG side (fwd side AGB): IPC 72-63-00-04 item 25 p/n 305-115-704-0
(Assy Package includes: carbon seal assy, rotating ring and O-ring p/n 649-393-130-0 (this O-ring goes INSIDE the rotating ring groove)
Further you need:
1x p/n J221P215 fuelpump shaft O-ring OR
1x p/n M83248-1-216 IDG shaft O-ring
1x p/n J221P034 O-ring around the carbon seal housing outside groove
26
- CFM56-7 static fluid leakages.
737-6/7/8/900
It
is frequently observed that fluid is dripping from an engine drain of a parked
737. This leakage occurs mainly when the engine has not operated for some time,
for instance after a hangar visit.
In most cases, static fluid leakages come from components such as the Hydro Mechanical Unit (HMU), High Pressure Turbine Air Case Cooling valve (HPTACC) valve or VBV/VSV actuators. Due to the stationary position of an O-ring or a carbon seal on a non rotating engine the fluid can seep through and spills on the ground via one of the drain lines. If one of the valves mentioned above has been tested during maintenance, the chance of static leakage is even greater. In particular Next Generation aircraft are more suspectible to this kind of leakages.
To
determine if a leakage is acceptable or not you must consult the tables in the
AMM 71-71-00 ‘Engine Vents
and Drains Inspection’ task. However, this task also tells to perform a
test run for 5 minutes in idle before performing a corrective action, if
necessary. If
the leakage continues after 5 minutes at idle and the leakage rate is more than
the serviceable limit, the source of the leakage must be repaired. But if the
leakage stops in less than 5 minutes at idle, no action is
required. This is because if the engine starts running the O-rings and carbon
seals will settle again, which may stop the leakage.
See
these AMM references:
737NG AMM 71-71-00-200-801-F00 2 (A) (2):
Leaks
from the drain can occur on an engine that does not operate or during an engine
start. These leaks are not
unusual, and may stop after the engine operates at minimum
idle for five (5) minutes.
And
737NG
AMM 71-71-00-200-801-F00 2 (E) (2):
NOTE: Leaks from the drain can occur on an engine that does not operate or during an engine start. These leaks are not abnormal, and may stop after the engine operates at idle power for 5 minutes.
30 - HMU
schematic drawing for training only.
737-6/7/8/900
HMU schematic drawing, to better understand the inside of this unit. For training purposes only !
31
- Chip
detector findings on cfm56-7.
737-6/7/8/900
When you find chunks of metal in your -7 engine magnetic chip detectors, don't panic right away. Checkout the amm 79-00-00-200-804-F00 and use the tool mentioned in this chapter. Toolnumber 856A2683G01, it's a CD-rom with pictures of parts you can find in the chip detectors.
More self-made detailed information about this subject will be published here in the future.
Due to copyright issues no official pictures of examples are published here.
32 -
Oil filter bypass lt flickering and egt counter flashing upon engine
startup.
737-3/4/500
737 classic with EFIS system: If
pilot reports about engine OIL FILTER BYPASS lite flickering and EGT DIGITAL
Counter Flashing upon initial start up of engine. Particularly it happens
when aircraft is parked for long time( about a night duration) in cold
environment.Do not worry just let the engine get warmed up and advise the
pilot to switch off the engine and then restart as per procedure.
I have faced it many times. Subsequent inspections regarding filter
condition and pressure switch and wiring check all found normal.The reason
of subject snag is as follows:
Aicraft parked in cold envirnment causes engine lubricating oil to
become dense and actuates the bypass switch momentarily off and on upon
engine start up. AMM states that EGT digital counter flashing is due to the
Flickering Oil Bypass Lite. Flashing stops as the oil filter bypass lite
becomes stable. Hense the only remedy to this PIREP is Restart of engine
after warm up.
regards Malik Javaid
33 -
Max
power assurance check calculation files for 737 classic and NG.
These 2 files you can use for calculating the EGT margin and %N2 margin for the CFM56-3 and - 7 engines used on the 737. The files are easy to fill-in and the results will be calculated accordingly. Note that you always use the AMM procedure to do this task, however any help by using these files is always a nice check to see if you're right. These files are made by Mr. Rob M. Many thanks for his input !
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MPA calculation file, for 737 classic (CFM56-3 engines). 737-3/4/500 |
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MPA calculation file, for 737 NG (CFM56-7 engines). 737-6/7/8/900 |