04 Thrust & Power Flashcards
Equation for thrust on a jet engine?
Force (Thrust) = mass x acceleration
Where do engines perform the worst?
High altitude, high humidity, high temperature.
Variation of turboject thrust with speed?
Ram effect?
As the airspeed increases the mass flow through the engine increases due to the ram effect.
Intake momentum drag?
Acceleration imparted to the air decreases as the speed increases.
Variation of jet thrust with altitude
Due to air density decrease
Thrust produced at different speeds for High and Low bypass engines?
3 limits of jet engines?
RPM limits
TGT limits
Thrust limits
Which ever limit is reached first will discate the meximum thrust.
Flat rated engine?
Ratings at cold air and warm air?
In cold air, engine is most likly to be restricted by RPM.
In warm air, engine likly to be limited by temperature.
Factors affecting mass and fuel flow? - Effect on Altitude?
Effect on Altitude - Air density decreases with increasing altitude. So less air going through engine therefore a lower fuel flow.
Factors affecting mass and fuel flow? - Effect on temperture
Drop in tempertaure causes an increase in density and an increase in airflow. At high temperatures the fuel flow is limited by the TGT and at low tempertaures by RPM/ Flat rating.
Propeller thrust?
Thrust depends on AoA, the faster you go the less thrust produced.
Angles on a propeller?
Optimum angle AoA is 4degrees. If the AoA reduces to 0 degrees, no power is produced.
Power avalaible - JET?
Power Available = Thrust x Velocity
Power Avaalible - Prop?
Both ends of the speed spectrum it drops beacuse of the reduced propeller efficiency.
The power required and drag curves?
Vmp is at the bottom of the power required curve.
Vmd is at the bottom of the drag curve.
Vmp?
Velocity minimum propulsion, maximum endurance speed. 0.76Vmd.
How can you you find Vmd from a power required curve?
Tangent to the power required curve is Vmd
