All of the information, photographs & schematics from this website and much more is now available in a 360 page printed book or in electronic format. Engine Description (Section 2 ). The CFM56-3 is a high bypass, dual rotor, axial flow turbofan engine. Basic engine specification are provided in Fig 1 and 2. The integrated fan and booster (low pressure turbine-LPC) is driven by a 4 stage low pressure turbine (LPT). A single stage high pressure turbine (HPT) drives the 9 stage high pressure compressor (HPC). The two rotors are mechanically independent of each other.
Air entering the engine are divided into a primary (inner) airstream and a secondary (outer) airstream (Fig3). After the primary airstream has been compressed by the LPC and HPC, combustion of the fuel in the annular combustion chamber increases the HPC discharge air velocity to drive the high and low pressure turbines. An accessory drive system off the N2 rotor drives engine and airplane accessory components. Engine Characteristics. 1. Trust Class for the CFM56-3B engine………. 22,100 LBS.
2. Type of engine……………………………. …. Axial Flow, Gas Turbine Turbofan. 3. Number and Type of Combustion Chamber….
One / Annular. 4.
Type of Compressor ………………………. ….
Two spool,13 stage compressor consisting of a 4 stage low pressure compressor (includes 1 stage fan) and a 9 stage high press compressor. 5.
Direction of Rotation (Both Rotors)…………. Clockwise (as viewed from the rear looking fwd). 6. Type of Turbine………………………………. 5 stage, split, consisting of a 1 stage high pressure turbine and a 4 stage low press. Turbine.
7. Engine Weight (Bare weight)…………………. 4290 pounds dry (approximate). (Eng. With QEC)……………. 5390 pounds (approximate). 8.
Engine length (with flame arrestor)……………114. 5 inches (approximate). Installed Engine Length (with inlet cowl)…. 192. 6 inches (approximate). 9. Engine diameter.
Largest diameter (without inlet cowl……… 87. 6 inches (approximate) Incl. Accessory gearbox). Largest diameter (with inlet cowl)………… 88. 4 inches (approximate). 10. Ignition system.
Ignition exciter and plug……………………… Two per engine. 11. Lubrication system…………………………….
Oil type (Class B [ type 2 ]). Min.
Eng. Oil Stating Temp -40C. 12.
Fuel system (fuel specification)……………. D1655- JET-A, -A1, -B, MIL-T-5624G JP-1,JP-4,JP-5, MIL-T-83133 JP-8. Operating Requirements (Section 3 ). Engine deterioration is directly related to engine hot section time/temperature (EGT) exposure.
Rapid temperature transients are also detrimental to hot sections part life. Therefore, to obtain maximum engine service life, time at takeoff / high thrust should be held to the practical minimum, and rapid throttle movements avoided during normal flight operations. Ratings, Restrictions and Power Management. Takeoff Rating-The Takeoff Rating is the certified rating or ratings defined in the regulatory agency Approved Airplane Flight Manual and is limited to 5 minutes.
The 5 minute limit applies to all operation above maximum continuous thrust. NOTE: The normal 5 minute takeoff time limit may be extended to 10 minutes for engine-out contingency if authorized by the regulatory agency Approved Airplane Flight Manual in the country of registration of the specific airplane (airplane registration) involved. If the 10 minute contingency time is utilized, the total operating time at takeoff thrust must be recorded in the flight log. CFM56-3B-2 Performance and Operating Limit.
100% N1= 5175 RPM. 100% N2 = 14460 RPM. Thrust Rating (lbs):. Takeoff, flat rated, ISA+15C: 22,100.
Max cont, flat rated, ISA+10C: 20,500. Max climb, flat rated, ISA+10C: 20,500. Max cruise, flat rated, ISA+10C: 19,193. Ground Operating Procedure (Section 4 ). Starting Notes. Starter air pressure lower than recommended may result in slow N2 acceleration and subsequent rpm hang-up.
Rapid EGT rise accompanied by slow N2 acceleration, hang-up or deceleration requires immediate start abort. These symptoms may indicate incorrect fuel scheduling, faulty instrumentation, engine damage, low starter pressure or excessive deterioration. The cause must be investigated as per the Aircraft Maintenance Manual, and corrected before further attempts to start. Starts with slow N2 acceleration from light-off to idle, accompanied by low EGT (lean fuel schedule), may be continued provided starter limits are not exceeded.
Starts in excess of 725 deg. C must be reported for corrective actions. Engine Shutdown. Engine Shutdown After Landing. Following high power operation, such as maximum reverse thrust during landing or maximum power assurance check, it is recommended that the engine be operated at, or near idle for 3 minutes prior to shutdown to thermally stabilize the engine hot section. If operational requirements dictate, the engine may be shut down with a one minute cooling period.
After shutdown, monitor EGT and engine rpm, to be sure that the temperature and rpm decrease, indicating fuel shutoff. Monitor EGT for indication of post shutdown fire. Note: After engine shutdown is complete and all rotation has ceased, EGT will normally increase due to temperature soak-back.
Flight Operating Procedure (Section 5 ). Setting of Takeoff Thrust. The desired thrust is obtained by setting the throttle to obtain the target N1 as determined from the Airplane Flight Manual performance data (or equivalent) for the applicable total air temperature, pressure altitude, engine bleed configuration and PMC status (on or off). During takeoff, engine instruments must be monitored to make sure that the engine limitations are not exceeded, e. - Exhaust Gas Temperature (EGT)…930 DEG C. - N1 and N2.
not to exceed allowable limits. - Oil pressure…min 13psi. At 85 % N2 normal range is between 18psig-65psig. At 90 % N2 normal range is between 21psig-72psig. At 95 % N2 normal range is between 24psig-80psig. Oil pressure is oil supply pressure measured relative to sump/vent pressure. Pressure surges may occur during cold soak.
sub zero temp starts and takeoff. Under these conditions, high oil pressure is acceptable. - If any overspeed or over-temperature has occurred, the duration and the highest RPM or EGT attained should be recorded as an engine discrepancy in the Aircraft Flight Report. Voluntary Shutdown In Flight. Retard throttle slowly and smoothly to idle.
NOTE: Gradual power reduction to idle during voluntary shutdown promotes thermal stabilization before fuel shutoff. Operate engine at idle for 3 mins if feasible. Airstart attempts may be made following a voluntary shutdown at any altitude and airspeed; however if the start cannot be achieved, establish flight conditions within the airstart envelope. Warning: Be prepared to abort the start if a rapid EGT rise occurs, approaching starting limits. -Light off normally occurs within 2 to 3 seconds after placing the fuel lever in the ON position. Observe same EGT, Fuel flow and RPM limits as for ground start.
-If the light-off does not occur within 30 seconds, abort the start by returning the fuel lever to the OFF position. Let the engine windmill for 30 seconds to purge the combustion section of residual fuel before attempting another start. -Starter off at 50 percent N2. -When the engine stabilized at idle N2. (a) Oil pressure…………Check. (b) Ignition off…………. Pilots discretion.
-It is recommended that the engine be stabilized at flight idle for 3 minutes prior to high power application following an airstart. Windmilling Restart Procedure.
Caution: Starter assist should be used if N2 is below 15 percent. If a windmill start must be attempted at less than 15 percent N2 because of starter unavailability, a Hung Start or Hot Start may result.
Increasing kias will increase windmill speed. Airstarts in most of the starting envelope require starter assist due to the low windmilling characteristics of the engine. RPM Hang-up During airstart. During airstarts at high altitudes and low airspeeds, rpm hang-up may be experienced after obtaining initial light-off and acceleration.
The hang-up is characterized as a stabilized engine speed lower than idle, with no response to throttle advancement and may be the result of either too rich or too lean fuel scheduling, low airspeed or excessive altitude. Operating Procedure For Abnormal Condition (Section 6 ). - If it is noted during a start procedure that a no light-off is indicated within 10 seconds after fuel is applied, the start procedure should be discontinued. -Before attempting a second start, dry motor the engine for 60 seconds for ground starts or windmill for 30 seconds for airstarts. Use alternate ignition system for second start attempt.
(Observe starter limitations). Note: CFM International does not supply the starter or thrust reverser for CFM56-3B-2 Engines on the 737-400 aircraft. The BOEING company will determine and supply the starter duty cycle limits, starter re-engagement limits, and starter air pressure requirements ,etc. which are compatible with the engine, for the 737-400 Aircraft Flight Manuals.
-If the second start attempt fails, no further start attempt should be made before the cause of the start failure has been determined and corrected (ground only). -If the failure to start is attributed to either ignition system, it should be recorded in the Aircraft Log, investigated and remedied at the earliest opportunity.
Unsatisfactory Starts. If a unsatisfactory start should occur, it will most likely be accompanied by one of the following conditions :.
Caution. THE EXHAUST GAS TEMPERATURE (EGT) HAS A DIRECT EFFECT ON THE SERVICE LIFE OF ENGINE HOT SECTION COMPONENTS. EXCESSIVE AND REPEATED HIGH EGT ENGINE OPERATION RESULTS IN PREMATURE ENGINE DETERIORATION.
A potential hot start is indicated by an abnormally rapid EGT rise after light-off. By monitoring fuel flow and EGT, a hot start can be anticipated before the 725 C limit is exceeded. Hot Starts may be caused by :. (a) Inadequate starter air pressure, resulting in N2 too low to provide sufficient compressor air flow. (b) Faulty starter valve action, preventing proper operation of starter, with same result as item (a). (c) Premature starter deactivation. (d) Incomplete purging of fuel in the combustion chamber from the previous start attempt.
(e) Foreign object damage (FOD) preventing sufficient engine acceleration and airflow. (f) Faulty pressurizing valve (hung open) resulting in fuel, under low pressure, puddling in the combustion chamber before light-off. (g) Faulty main engine control (MEC) resulting in incorrect start fuel scheduling.
(h) Incorrect scheduling of variable stator vanes (VSV). B. Hung Starts.
A hung start is identified by light-off followed by abnormally slow acceleration and rpm stabilization below idle. A hung start may be result of fuel scheduling being either too lean or too rich. A lean hung start is associated with low fuel flow and proportionally low EGT.
A rich condition can be recognized by a high fuel flow and an EGT rise which may tend to develop into an over-temperature condition and possible compressor stall. Hung Starts may be caused by :. (a) Starter air pressure too low to accelerate engine to self-sustaining speed. Exercise caution when operating an engine with oil pressure outside the normal pressure range. N2 (Core Engine) and N1 (Fan) Transitory Overspeed. The throttle must be retarded to reduce core engine speed below limits. Caution: All N2/N1 overspeed conditions must be reported for maintenance action.
The maximum speed attained and the duration of the overspeed condition should be recorded in the Aircraft Log. Speed range % --- Procedure. N2. 105. 1-106. 0 --- Normal operation to next landing.