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User 'Calphool' writes:

For example, in a real plane, if you jam the throttle forward too quickly, you can kill the engine or make it backfire. This may sound like a trivial detail, but people have died on takeoff because they never learned proper throttle technique.

  1. Why and how?
  2. What accidents were caused by mishandling of the throttle levers?
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    $\begingroup$ I think it's because airplane carburetors don't have accelerator pumps like automotive carbs do (or did, back when cars had carbs), so when the throttle opens quickly, allowing in more air, the mixture becomes too lean to sustain combustion. See e.g. en.wikipedia.org/wiki/Carburetor#Accelerator_pump fo rmore. $\endgroup$ – jamesqf Feb 25 '15 at 5:54
  • $\begingroup$ I am surprise that there is no electronic logic avoiding these kind of problems. I can't give you an answer. $\endgroup$ – Trebia Project. Feb 25 '15 at 6:56
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    $\begingroup$ I guess there is no single answer for all aircraft types. With an engine completely under the control of the FADEC this would not be a problem for instance. $\endgroup$ – mins Feb 25 '15 at 9:57
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    $\begingroup$ @jamesqf That depends on the engine/carb in question: All the Piper Cherokee family planes have accelerator pumps in the carburetor, but they still tell you not to slam the throttle around though. $\endgroup$ – voretaq7 Feb 25 '15 at 17:56
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    $\begingroup$ @jamesqf That's pretty common when the engine is cold (I've had it happen warm too but you have to be pretty ham-fisted, and really at that point you gotta ask yourself Why am I slamming the throttle around when the engine is warm?) The accelerator pump is why there are all those admonitions against pumping the throttle to prime the engine though: The fuel runs back down the carb throat and soaks your air filter, then the engine backfires and you have a weenie roast on the ramp :-/ $\endgroup$ – voretaq7 Feb 25 '15 at 21:14
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There are a few ways rough throttle handling on a propeller airplane can get you into trouble:

  • Gyroscopic yaw and torque: a rotating prop creates yaw 90 degrees to its spin which are offset by control inputs (mainly rudder), throttling up or down requires changes to these control inputs. Quick changes require bigger changes, slower changes give a pilot more time and allows smoother transitions. This isn't that big a consideration on lower-powered aircraft but it is on high-performance aircraft. In the first case that comes to mind an inexperienced P-51 pilot rammed full throttle in on a go-around and it flipped the aircraft on its back. At low airspeed it's possible there wasn't enough control authority to manage the forces even if he had been prepared for them
  • Pitch changes: most aircraft will have a pitch change when the throttle is increased or decreased, again quick changes require coarser changes in controls while slower changes mean smoother and better controlled inputs. Again more applicable to higher performance aircraft
  • Engine and carburetor: The engines in most light propeller-driven airplanes represent the pinnacle of 1950's technology. Fuel mixture, priming, and throttle control are all completely manual - there are no electronic systems to help smooth things out during throttle changes. Many airplane engine carburetors do not have an accelerator pump to shoot extra fuel to prevent the engine stalling during a quick throttle up. Given that an engine stall when airborne is a life-threatening emergency it's in your interest to make smooth, controlled changes

Although not usually a safety issue wear and tear is also a consideration. Smooth, gentle changes are better for the levers, plungers, and cables in the engine control system. Less wear and tear means better reliability and less costs.

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    $\begingroup$ I actually fly a C172SP with an IO-360 (fuel injected -- no carb). You can still kill the engine with aggressive throttle handling, even on a very modern 172. $\endgroup$ – Calphool Feb 25 '15 at 20:33
  • $\begingroup$ True, I had similar experiences in a fuel injected bulldog. It was still manual mixture control, there were no computers in there. $\endgroup$ – GdD Feb 26 '15 at 8:38
  • $\begingroup$ The first point however gives you more trouble in simulator than real life, because in simulator you don't have depth perception, vestibular system does not register turning and you don't have feel in the controls, all of which help judge proper correcting in real life. And yes, simulators (at least the good ones) do simulate gyroscopic, slip-stream and p-factor effects. $\endgroup$ – Jan Hudec Feb 26 '15 at 12:42
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This actually happened to me about two months ago.

On a very cold night, I went to do my night-currency (3 takeoffs and landings) in a Cessna SkyCatcher (C-162). The plane was hard to start due to the freezing temperatures, but eventually got it going. I did the normal run-up checks, took off, and did one loop around the pattern, coming back for a normal landing.

I made a full stop on the runway, reset the flaps, and pushed the throttle forward. The engine instantly died. I told the tower I was stuck on the runway, and he held up some other traffic that was looking to land.

Multiple attempts to get the engine restarted failed. Eventually, the FBO sent a tug out to pull me off the runway.

Later I talked to the Chief Pilot who was aware of the problem, and most frighteningly of all, said that it definitely could happen in the air. If I had decided I needed a go-around on short-final, and pushed the throttle too quickly, it may have killed the engine when I needed it most.

I do not think that I "jammed" the throttle forward, but I may have pushed a little aggressively. I will always be very gentle on my throttle from now on. But what concerns me is those times when you need power quickly (such as a go-around near the ground), you just may not have time to do a slow-and-easy acceleration.

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    $\begingroup$ I've never felt like I was jamming the throttle, but I've had a few backfires that tell me otherwise. :-) $\endgroup$ – Calphool Feb 25 '15 at 20:34
  • $\begingroup$ Just out of curiosity, what did your oil temp gauge read before you took off? You'd like to think that if it was in the green this kind of thing wouldn't happen, but that's probably wishful thinking. The big picture is always count to three as you're manipulating the throttle. Anything faster than that is probably risky. $\endgroup$ – Calphool Feb 25 '15 at 20:46
  • $\begingroup$ Because of the difficulty getting the engine started, I was careful to check everything during the run-up checks, so I know oil temp was green then. I suspect that when I slowed and then idled the engine on landing, it got too cold. However, I don't know the oil temp when I was stuck on the ground. $\endgroup$ – abelenky Feb 25 '15 at 20:56
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    $\begingroup$ Y'know, you're actually lucky that it croaked after landing during the ground roll. I've read about people advancing the throttle too fast, getting the engine into a "choking" kind of vibe, think it's going to resolve, but it actually doesn't and then end up doing an emergency landing off the end of the runway (if they're lucky). $\endgroup$ – Calphool Feb 25 '15 at 21:03
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    $\begingroup$ Perception of time is subjective, when someone has adrenaline going, or is simply busy fast actions don't seem that way. Perhaps training in a mental count using thousands or bananas (one one thousand, two one thousand) when moving the throttle would enforce more gentle changes. I'll try that next time. $\endgroup$ – GdD Feb 26 '15 at 8:42
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Straight from the FAA knowledge tests: Overly-aggressive throttle movements/RPM changes can lead to de-tuning of the crankshaft counterweights.

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