M. Check reverse thrust detent (Ref 78-32-01 A/T).
N. Check takeoff thrust setting, and engine acceleration and deceleration. Engine bleed air off.
NOTE: After completion of a satisfactory trim run, the engine shall be checked at takeoff setting to ensure that takeoff thrust is available and to check for cushion between takeoff and full throttle thrust lever position. Normally takeoff thrust is obtained at part throttle; however, the amount of throttle required will change with ambient temperature.
(1)
Operate engine at idle rpm for 3 minutes.
(2)
Advance thrust lever to takeoff EPR target setting.
CAUTION: THERE IS NO THRUST LEVER STOP AT TAKEOFF RATING. DURING ENGINE OPERATION AT TAKEOFF RATING, EXHAUST GAS TEMPERATURE, Nl AND N2 RPM MUST BE CLOSELY MONITORED TO ENSURE THAT OPERATING LIMITATIONS ARE NOT EXCEEDED.
NOTE: If takeoff EPR is not attainable, recheck the target and check for satisfactory throttle rigging. If all of the engine parameters appear high when compared with another engine, recheck the target and check the Pt7 system for leaks. If all appears normal, repeat the engine trim procedure.
(3)
When engine has stabilized at takeoff setting (minimum of 30 seconds at takeoff) record full set of engine instrument readings (except vibration). Record EGT last.
(4)
Mark position of forward edge of thrust lever on control stand using grease pencil, tape, or other temporary marking method.
(5)
Retard thrust lever to idle position. Calculate 95% of takeoff N2.
(6)
After approximately 70 seconds at idle, advance thrust lever in 1 second or less from idle to takeoff mark on control stand determined in step (4) above.
NOTE: If engine has been operated at takeoff power for longer than 3 minutes, operate engine at idle for 3 to 5 minutes prior to performing engine acceleration time check.
(7)
Record engine acceleration time; time elapsed from initial advancement of thrust lever until engine has reached 95% of takeoff N2 rpm determined in step (5) above. Approximate acceleration time at sea level is between 5 and 6 seconds with engine bleed air off.
NOTE: Maximum acceleration time is subject to pressure altitude. Acceleration time stated above may be increased by 0.30 seconds for each 1000 feet increase in pressure altitude above sea level.
(8)
Stabilize at takeoff setting for 2 to 3 seconds, and decelerate engine to idle by retarding the thrust lever to idle in 1 second or less. Ensure that engine decelerates smoothly and stabilizes at idle rpm. Any flameout is cause of rejection of the fuel control.
NOTE: If fuel control is replaced, refer to 71-00, Power Plant - A/T for testing to be accomplished prior to continuing operational procedures.
(9)
If acceleration time exceeds 6.0 seconds at sea level, repeat above steps (6) thru (8) until three satisfactory accelerations and decelerations have been completed.
(10)
Normal acceleration time is 5 to 6 seconds at sea level. If average time for engines receiving three acceleration checks exceeds 6.0 seconds, it should be reported as an engine discrepancy and corrected before next takeoff.
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NOTE: Maximum acceleration time is subject to pressure altitude. Acceleration time stated above may be increased by 0.30 seconds for each 1000 feet increase in pressure altitude above sea level.
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O. Idle engine for 5 minutes and then shutdown.
P. Remove trim equipment from engine, cap Pt7 test fitting, and reinstall all tubing clamps removed to facilitate trimhead installation.
Q. Seal IDLE and MIL speed trimmers with approved sealing wax.
R. Remove, clean, and reinstall engine fuel and oil filter screens and elements. Change applicable screens and elements if necessary.
S. Check engine and engine-mounted accessories for fuel, oil, pneumatic, and hydraulic leaks.
T. Deleted
5. Restore Airplane to Normal Configuration
A. Install engine cowl panels (Ref 71-11-11 R/I).
B. Open ENG TRIM circuit breaker on panel P6.
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POWER PLANT (JT8D) TRIM DATA - MAINTENANCE PRACTICES
1. General
A. This section contains general instructions for use of power plant trim data to determine the target values needed for engine trimming and includes a trim table locator tabulation to enable fast location of the proper trim data for specific trim situations.
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