Questions and Answers
Detonation occurs in a reciprocating aircraft engine when:
Detonation may occur at high-power settings when:
If a pilot suspects that the engine (with a fixed-pitch propeller) is detonating during climb-out after takeoff, the initial corrective action to take would be to:
If the grade of fuel used in an aircraft engine is lower than specified for the engine, it will mostly likely cause:
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The uncontrolled firing of the fuel/air charge in advance of normal spark ignition is known as:
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Study Notes
Detonation in Aircraft Engines
- Detonation is defined as the explosion of the fuel/air mixture in the cylinders rather than a normal burn, causing a rapid downward force on the piston.
- Common causes include fouled spark plugs, defective wiring, or hot spots within the combustion chamber triggering premature ignition.
Detonation Under High-Power Settings
- Detonation can occur when the fuel mixture ignites instantaneously, leading to a lack of progressive burning.
- An excessively rich fuel mixture can also lead to explosive power gains, increasing the risk of detonation.
- Early ignition by hot carbon deposits in cylinders is a contributing factor.
Corrective Actions During Detonation
- During climb-out after takeoff, if engine detonation is suspected, the initial step is to lower the nose slightly to boost airspeed and reduce engine load.
- Engine detonation typically results from using poor quality fuel or excessive temperatures.
Impact of Fuel Grade on Engine Performance
- Utilizing a lower grade of fuel than specified for an engine is likely to induce detonation, as lower grades ignite at lower temperatures.
- Higher temperature engines that require a higher grade fuel may cause lower grade fuels to detonate.
Pre-Ignition Defined
- Pre-ignition occurs when the fuel ignites before normal spark ignition, often triggered by excessively hot components, such as exhaust valves or carbon particles.
- It is characterized by ignition in only a few cylinders, differentiating it from detonation, which affects all cylinders under similar conditions.
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Description
Test your knowledge on abnormal combustion in aircraft engines with these flashcards. Focus on concepts like detonation and the effects of ignition failure. Ideal for aviation mechanics and engineering students.