Critical engine

Question 1

How does p-factor effect the critical engine?

Answer 1

• Airplane flies at higher AOA with OEI
• This creates a p-factor effect on the operating engine (more thrust produced with the descending propeller blade)
• On a conventional twin, if the left engine fails the right engine produces more thrust at the higher AOA, this additional thrust acts much further from the aircrafts center of gravity causing a higher yawing moment
• Losing the left engine has a more negative effect than losing the right one in a conventional airplane

Question 2

How does accelerated slipstream effect the aircraft with the critical engine inoperative?

Answer 2

• Caused by additional thrust created by the operating engines descending propeller blade as a result of p-factor
• In a conventional twin, the left engine will produce accelerated airflow which creates additional lift that is very close to the aircrafts center of gravity having minimal impact on the rolling moment
• This accelerated slipstream passes closely to the rudder which improves rudder authority with more airflow hitting it
• If the left engine fails, the right engine produces an accelerated slipstream that creates additional lift farther from the aircrafts center of gravity adding more to the rolling moment(does not help rudder authority either with right engine operating)

Question 3

What is a critical engine?

Answer 3

The engine that if failed has the most adverse effects on the handling characteristics and performance of the aircraft

P-factor
Accelerated Slipstream
Spiraling Slipstream
Torque