15.21 operation and monitoring Flashcards
what are the potential reasons for maintenance staff to operate a gas turbine engine?
Confirming a flight crew reported fault
Post-maintenance basic engine or aircraft system checkout
Deterioration of engine performance
Aircraft control linkage wear
Moving an aircraft from one maintenance location to another
To taxi-check an aircraft system
what must be done before beginning an engine ground run?
the aircraft technical logbook must be checked for any outstanding entries that would prevent the aircraft from being moved or the engine from being started
how do you prepare the aircraft for engine run up?
-It must be ensured that the undercarriage is down and locked.
-It needs to be checked that engine oil levels are satisfactory, all panels are secure and that there is sufficient fuel for the ground run.
-Intakes and exhausts must be inspected for foreign objects, damage, and freedom of rotation and that —–engine exhausts are clear.
-The aircraft must be positioned into the wind, chocks need to be fitted, brakes must be applied and it has to be ensured that the areas in front and behind the aircraft are clear of buildings, other aircraft etc. up to a distance of 10 metres (30 feet) in front of the engine intake and at a distance as specified in the maintenance manual behind the aircraft tail
what is possible when ground running engines?
trimming for imbalances
when can engine/ how much power be increased above idle and why?
only if absolutely necessary, it shorten engine life through heating and cooling
when measuring engine power what must be used as the datum?
the oldest engine
what precautions should be taken on shutdown?
operate at idle for 5 minutes for cool down to prevent rotor seizing
what indications about the engines are given to the cockpit?
Engine Pressure Ratio (EPR) (depending on engine type)
Rotor speed, N1 and N2 (and N3)
Fuel Flow (FF)
Exhaust Gas Temperature (EGT)
what is one of the most important parameters?
EGT as it indicates an overheat condition
how do centrifugal engines measure engine power?
by comparing RPM to jet pipe temperature
how do axial flow bypass engines measure power?
static ambient pressure vs exhaust gas pressure
what indicates the power generated by a turbo prop or turbo shaft engine?
torque monitoring systems
what can a torque monitoring system be used to measure in addition?
-Automatically operate the propeller feathering system.
-Assist in the automatic operation of a water injection system.
-Limit engine power output.
-Balance power output between engines on twin or multi-engine arrangements
how can torque on turboshaft/ turbo prop engines be shown in the cockpit?
Torque oil pressure (in psi)
Torque percentage
Sometimes a direct horse-power read-out
what are the common sensing elements for a torque sensing unit?
-Hydro-mechanical, which converts engine oil pressure to a torque signal.
-Electronic, which converts the twist of the power output shaft into a torque signal.
-Phase displacement, where a shaft consisting of 2 shafts, each with a phonic wheel. One shaft provides the reference signal and the second shaft is allowed to twist
