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Explain please for non-native speakers the difference between these engine (jet or piston) terms:

  • shut down
  • cut-off
  • cut down

I'm studying at a civil aviation university to become a pilot and a teacher told me "shut down" is used when you switch the engine off, "cut-off" is used when the engine electrical supply fails, and "cut down" is when you reduce throttle setting. But I'm not sure it's correct.

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    $\begingroup$ "Cut down" typically means "lower the speed", usually via a throttle. $\endgroup$
    – zymhan
    Commented May 26, 2019 at 11:53
  • $\begingroup$ I think we need more context. What University? What course of study? What is the language being spoken? (is there a translation problem?) $\endgroup$
    – Mike Sowsun
    Commented May 26, 2019 at 12:54
  • $\begingroup$ @MikeSowsun okay, check update. $\endgroup$
    – Nikita
    Commented May 26, 2019 at 13:12
  • $\begingroup$ @MikeSowsun I don't have text in which i found these phrases. $\endgroup$
    – Nikita
    Commented May 26, 2019 at 13:20
  • $\begingroup$ also consider the case of "engine fall off" $\endgroup$
    – quiet flyer
    Commented May 26, 2019 at 13:54

2 Answers 2

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To be specific:

Shutdown: To take a step or series a steps to stop the operation of a machine and put it into its normal inoperative state. A shut-down procedure may include cutting off fuel, closing valves, and turning off pumps, or may just be flipping a switch to OFF.

Cut-off: To interrupt (or a noun describing something that interrupts) the supply of something to a machine; fuel, water, electricity. Generally refers to closing of a valve or opening an electrical contactor or switch. On a piston engine, you have a mixture setting called "idle cut-off" that blocks flow of fuel at the carburetor. You might see a switch that opens a contactor to an electrical bus, for use in emergencies, labelled "Bus XXXX Cutoff".

Cut-down: I've been working in aviation in N America since 1975 and have never heard of this term as relating to operation of an engine (maybe in UK?). Normally if I see the word cut-down it's an adjective that describes something that has been physically altered to make it shorter or smaller. Like a cut-down vertical fin, or a cut-down antenna, or cut-down propeller blades. I'd be surprised if anybody on here has ever heard of the phrase "cut down power" as an instruction to reduce power, or thrust. You just say "reduce".

You DO sometimes hear the word "Cut" by itself as an instruction to go to idle or to remove power completely on an engine. A skydiving pilot may get an instruction to "Cut" when it's time for jumpers to exit. Some day when you are on a jet type course, one of the simulator sessions will include "V1 Cuts", where one engine is failed just as you are passing V1 (whereupon hilarity ensues the first time you do it). So in those cases, power is cut, but not "cut-down".

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  • $\begingroup$ I‘ve never heard „cut down“ in the UK either (other than in gardening and landscaping). Definitely not anywhere close to aircraft engine operation. $\endgroup$
    – Cpt Reynolds
    Commented May 26, 2019 at 19:31
  • $\begingroup$ Now it's clear, thx. $\endgroup$
    – Nikita
    Commented May 26, 2019 at 19:41
  • $\begingroup$ Is there a special phrase for a situation when engine stops working by itself in flight(not due to some malfunction, so it is possible to start it up again in flight)? $\endgroup$
    – Nikita
    Commented May 26, 2019 at 19:51
  • $\begingroup$ In-Flight Shutdown. In a jet say, there is often a dedicated procedure in the Quick Reference Handbook for shutting down and "securing" an engine, which could be discretionary or following a failure, and may be one procedure or separate procedures for each case. $\endgroup$
    – John K
    Commented May 27, 2019 at 1:10
  • $\begingroup$ For reducing power there is also a more specific alternative ‘retard’. $\endgroup$
    – Jan Hudec
    Commented May 27, 2019 at 18:10
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The FAA Airman's Information Manual essentially describes "Cut" as the same as "Shut Down". I have heard some refer to "Shut Down" as what is done during normal operations and according to normal operating procedures. While a "Cut" is when a problem exists which would necessitate such an immediate shut down that normal checklist protocols, such as a cool-down period, would be obviated.

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