For various reasons (e.g. noise, fuel savings), some airlines allow single engine taxiing. Obviously, this produces an asymmetric thrust during the taxi. If the left engine is used, the aircraft always wants to steer to the right. How is this compensated? Do pilots use the tiller all the time to countersteer, or pedals, or brakes? Is there a possibility to "trim" the aircraft during taxiing?
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1$\begingroup$ There will be more force on the tiller (if the tiller has feedback), but if the tiller is straight the aircraft should go straight too. $\endgroup$– Ron BeyerCommented Jan 9, 2018 at 17:16
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2$\begingroup$ I find this question interesting. In about 1978 I shutdown my single engine recip for an exceptional long delay (about 15min). Later I received a reprimand from the control tower and was given a FAR that prohibits aircraft from shutting down an aircraft engine while maneuvering on an airport. I looked for this FAR for this answer but was unable to find it. Apparently their is a difference between jets or at least multi-engine aircraft. Or, the FAR's have changed. A google search showed multi-engine shutdown a common practice... $\endgroup$– jwzumwaltCommented Jan 9, 2018 at 17:38
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$\begingroup$ The nose wheel. $\endgroup$– Steve KuoCommented Jan 9, 2018 at 19:39
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3$\begingroup$ @jwzumwalt Logically there may be a difference for vehicles that require a ground power unit to restart their engines... Perhaps that might help refine your search. $\endgroup$– PerkinsCommented Jan 9, 2018 at 22:38
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2$\begingroup$ I once tried a single engine taxi with a Beechcraft King Air - a twin-turboprop - in X-Plane, it was uncontrollable. Is this a feature of twin-props or a fault in the simulation? $\endgroup$– ChristianCommented Jan 10, 2018 at 8:28
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2 Answers
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First off, the thrust asymmetry problem is far less pronounced in large jet aircraft as compared with light twin engine propeller driven aircraft. Secondly, taxi operations generally don’t use very much thrust, with the engines often at idle power during this process, only requiring brief bursts of moderate thrust to get the aircraft moving from standstill.
Taxiing small, light twins can be difficult in an OEI (One Engine Inoperative) scenario, in many cases being almost impossible to turn the airplane sharply toward the good engine. Sometimes pilots will simply turn the aircraft only towards the dead engine and perform a 270° turn toward the dead engine instead of attempting to turn the airplane toward the good engine, should a turn toward the good engine be required. Sometimes, as a loss of an engine becomes an emergency situation, a light twin pilot will sometime just shut down on the runway or on a turnoff, then just have the aircraft towed back as opposed to attempting to taxi it with an OEI.
Asymmetric thrust can also be used by light twin aircraft to perform even sharper turns at slow speeds, with the pilot simply advancing the throttle to the engine on the outside of the turn while leaving the throttle on the inside of the turn at idle. This can also be useful for maintaining directional control while taxiing, taking off and landing in strong crosswind conditions, since it requires less rudder input to correct.
answered Jan 9, 2018 at 18:38
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2$\begingroup$ Yes. OEI means One Engine Inoperative. $\endgroup$ Commented Jan 9, 2018 at 20:43
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Very little thrust is required to maintain a quite adequate taxi speed. So although a small of amount of yaw is produced, it is very easily compensated for by the use of nose-gear steering.
