Engine Exhaust and Reverser Systems Flashcards
How does a leak appear in an engine exhaust system?
It normally looks like a gray or black feather-shaped streak coming from a crack or form a location where components are not in perfect alignment.
How can you check a reciprocating engine exhaust system for leaks?
Pressurize the exhaust system with the discharge from a vacuum cleaner and wipe a soap solution over all joints and suspect areas. A leak will cause bubbles to form.
How do the components in the exhaust system of a turbocharged engine allow for expansion and contraction due to heat, and at the same time prevent leakage?
Bellows and ball joints prevent leakage while allowing contraction and expansion.
Should a turbocharged engine be started with the waste gate open or closed?
Open, so as much exhaust as possible will bypass the turbine.
What is the primary function of a reciprocating engine exhaust system?
Its main function is to dispose of the gases with complete safety to the airframe and the occupants of the aircraft. The exhaust system can perform many useful functions, but its first duty is to provide protection against the potentially destructive action of the exhaust gases.
What is a short stack exhaust system?
The short stat exhaust system utilizes open exhaust tubes with no mufflers. The short stack system is generally used on non-supercharged engines and low-powered engines where the noise level is not to objectionable.
How is exhaust flow different in a ducted fan turbine engine verses an unducted fan engine?
Ducted fan engines take the fan airflow and direct it through closed ducts along the engine. Then, it flows into a common exhaust nozzle. The core exhaust flow and the fan flow mix and glow from the engine through this mixed nozzle. The unducted fan has to nozzles, one for the fan airflow and one for the core airflow. These both flow to ambient air separate from each other and have separate nozzles.
What is the purpose of an augmentor on a reciprocating engine exhaust system?
The augmentors are designed to produce a venturi effect to draw an increased airflow over the engine to augment engine cooling.
How does a reciprocating engine muffler decrease engine noise?
Exhaust gases from the cylinders are combined into a common manifold that contains a section of exhaust where the volume increases (expansion chamber), slowing the gases down, diffusing the flow through internal baffles, and reducing the noise.
What is a jet aircraft hush kit?
A hush kit is an aerodynamic device that defuses the flow of exhaust from older turbojet engines, by reducing the noise caused by high-velocity jet exhaust.
Why are thrust reversers not normally used when the airplane is moving below approximately 60 knots?
There is a danger of recirculating the exhaust gases and of the engine ingesting foreign objects stirred up by the high-velocity gases.
What is a mechanical-blockage thrust reverser?
A thrust reverser that slides a pair of scoop-shaped doors aft and opens them so they block the rearward flow of gases and deflect the gases forward.
How does a cascade-type thrust reverser operate?
A portion of the fan cowl moves rearward, and a series of blocker doors deflect the fan discharge air through fan cascades that direct the discharge air forward. Ath the same time, blocker doors shut off the flow of gases from the core engine and deflect it though cascades that direct it forward.
