Multi Engine Need To Know’s

Question 1

Absolute Ceiling

Answer 1

The density altitude beyond which no further climb is possible with both engines operating at maximum power

Question 2

Asymmetric Thrust

Answer 2

Uneven thrust created by the ascending and descending propeller blades. This condition also occurs when the thrust produced by the engines of a multi- engine airplane is uneven

Question 3

Critical Engine

Answer 3

The engine with the most adverse effect on controllability and climb performance of a multi-engine airplane if it were to fail

Question 4

Drift Down

Answer 4

The unavoidable descent due to the loss of an engine when above the single-engine absolute ceiling of an airplane

Question 5

Propeller Synchronization

Answer 5

Adjusting the propeller controls to operate the propellers in unison, eliminating the uncomfortable noise of two propellers operating at slightly different rates

Question 6

Service Ceiling

Answer 6

The maximum density altitude at which the airplane can produce a 100 FPM rate of climb with both engines operating. This ceiling assumes the aircraft is at the maximum gross weight, and in the clean configuration, if there was a single engine operating a requirement of 50FPM would only be needed in conditions that assume the critical engine isn’t operating

Question 7

Windmilling

Answer 7

The rotation of an aircraft propeller created by air flowing around it when the engine is not operating

Question 8

Zero Sideslip

Answer 8

A control technique used in following an engine failure in a multi-engine aircraft where the pilot maintains an attitude that minimizes drag, alleviating the sideslip of the airplane

Question 9

What is the acronym P.A.S.T used for?

Answer 9

P.A.S.T. is a memory aid and acronym that stands for four factors that cause conventional multi-engine aircraft with one engine inoperative to behave dangerously.

Question 10

What is the C in C.O.M.B.A.T.S?

Answer 10

Critical engine inoperative/cowl flaps open and windmilling

Question 11

What is the O in C.O.M.B.A.T.S?

Answer 11

OPERATING ENGINE AT FULL POWER

Question 12

What is the M in C.O.M.B.A.T.S?

Answer 12

MAXIMUM UNFAVORABLE WEIGHT

Question 13

What is the B in C.O.M.B.A.T.S?

Answer 13

BANK INTO OPERATING ENGINE BY 5°

Question 14

What is the A in C.O.M.B.A.T.S?

Answer 14

AFT-MOST CENTER OF GRAVITY (CG)

Question 15

What is the T in C.O.M.B.A.T.S?

Answer 15

TAKEOFF CONFIGURATION

Question 16

What is the S in C.O.M.B.A.T.S?

Answer 16

STANDARD TEMPERATURE DAY: TEMP & PRESSURE

Question 17

Explain takeoff configuration in combats?

Answer 17

Flaps are down and extended to create a high drag condition and simulate the conditions during takeoff. Gear, however, is not required to be down according to FAR 24.19(c)(5).

Question 18

Explain Aft CG in combats?

Answer 18

This criteria helps demonstrate the limits of rudder effectiveness and increases instability.
With the CG being so far aft (i.e. back towards the tail), the lever arm impact of rudder inputs to control yaw is reduced significantly. This helps place the plane’s performance on the edge of availability (yes, new word).

Question 19

Explain Bank in combats.

Answer 19

A crucial step in any single-engine flight, banking into the working engine helps reduce the side of the fuselage flying into the relative wind and decreasing performance. It’s a key part of directional control when losing an engine so they include it in the test.

Question 20

Explain maximum unfavorable weight in combats.

Answer 20

Usually maximum takeoff weight (MTOW). This is supported by the notion that all V speeds are computed at max gross weight unless specified otherwise in the POH. The term “most unfavorable weight” is interpreted in the context of performance rather than VMC.
This test intentionally degrades the power performance by taking off at max gross weight, challenging the operating engine’s capabilities. This approach helps identify the aircraft’s performance limitations.

Question 21

Explain the reason for operating at full engine power in combats?

Answer 21

With the critical engine at idle and windmilling, we now need our operating (i.e. working) engine at full power. This whole test is done to emulate one of the riskiest scenarios for losing an engine: at take off.

Question 22

The purpose of the COMBATS acronym?

Answer 22

helps you memorize the seven conditions that aircraft manufacturers must demonstrate in their twin engines planes during F.A.A. certification (VMC Factor FAA Demonstration, as required by 14 CFR 23.149).

A crucial aspect of this certification is determining minimum controllable airspeed, or VMC. This is the speed at which, under the following conditions, the plane will be uncontrollable if flown any slower than VMC.

Question 23

What is considered a light twin?

Answer 23

having a weight of 6,000lbs or less.