Chapter 7: Aircraft Systems Flashcards
Name 2 primary reciprocating engine designs.
spark ignition and compression ignition
Why do opposed-type engines have higher power-to-weight ratios ?
1) comparatively small, lightweight crankcase. 2) cylinder arrangement reduces the engines frontal area and allows streamlined installation that minimizes drag.
Why do two-stroke engines typically have higher power-to-weight ratios than four-stroke engines ?
there is a power stroke on each revolution of crankshaft.
Name the main parts of spark ignition reciprocating engine.
cylinders (valves, plugs, pistons), crankcase (crankshaft and connection rods), accessory housing (magnetos).
Why is a propeller twisted ?
To produce uniform thrust. Blade travels less near hub than tip.
Why is a fixed-pitch propeller used ?
Low-weight, simplicity, and low cost
List 2 types of fixed-pitch propellers.
Climb and Cruise.
Describe characteristics of a climb propeller.
Has a lower pitch, therefor less drag resulting in higher RPM and more horsepower capability which increases performance during takeoffs and climbs but decreases performance during cruising flight.
Describe the characteristics of a cruise propeller.
Has a higher pitch, therefore more drag, resulting in lower RPM and less horsepower capability, which decreases performance during takeoffs and climbs but increases efficiency during cruising flight.
What instrument indicates engine power on a fixed-pitch propeller ?
Tachometer
Why might the tach show the correct power output as the altitude increases ?
Power output depends on air density. Less air reduces power. As altitude increases, the throttle must be opened to maintain RPM.
Describe the characteristics of a constant-speed propeller.
A controllable-pitch propeller whose pitch is automatically varied in flight by a governor maintaining constant rpm despite varying air loads.
