How pilots taxi a twin-engine aircraft on one engine, control asymmetric thrust, protect brakes and systems, and know when a tow is safer.
Pilots taxi a twin-engine aircraft on one engine by using low thrust, nosewheel steering and, when necessary, differential braking to counter the yaw towards the stopped engine. They do so only when the aircraft flight manual and operator procedures permit it, after checking that steering, brakes and essential systems remain available.
When is single-engine taxiing used?
Single-engine taxiing is mainly used by transport aircraft to reduce fuel burn, emissions and engine running time during a long taxi. Operators may permit a delayed second-engine start before departure or the shutdown of one engine after landing.
In real-world aviation, this is a planned procedure rather than an improvised fuel-saving trick. It may be prohibited on steep slopes, contaminated surfaces, congested aprons or whenever weather, aircraft mass, tight turns or system requirements make two-engine operation safer.
Intentional one-engine taxiing is less common in light piston twins. Turboprops require particular attention to propeller condition, beta range and residual thrust; our guide to controlling a twin turboprop on the ground covers those type-specific considerations.
| Aircraft type | Main one-engine taxi concern |
|---|---|
| Piston twin | Limited steering authority, engine warm-up and the risk of overheating brakes while using excess power. |
| Turboprop | Propeller feathering, beta or reverse limitations, residual thrust and strong response to power changes. |
| Transport jet | Hydraulic, electrical and pneumatic availability, delayed-start timing and higher breakaway thrust. |
How do pilots maintain directional control?
At taxi speed, pilots counter asymmetric thrust primarily with nosewheel steering rather than aerodynamic rudder force. Rudder pedals may command the nosewheel on some aircraft, but the rudder itself has little effect until enough airflow passes over it.
With a wing-mounted engine stopped, the operating engine yaws the aircraft towards the dead-engine side. A turn towards that side can tighten quickly; a turn towards the live-engine side needs more steering effort. The pilot anticipates both rather than waiting for the nose to depart the taxi line.
- Release the brakes before adding power. Use only enough thrust to overcome inertia, then reduce it once the aircraft is rolling.
- Hold the centreline with nosewheel steering. Use the tiller or approved pedal-steering range smoothly instead of making abrupt corrections.
- Add differential braking only as required. Continuous brake pressure against high thrust creates rapid brake heating and wastes the fuel the procedure is meant to save.
- Slow before sharp turns. Avoid adding a large burst of power halfway through a turn, especially when turning towards the operating engine.
- Stop if steering authority is inadequate. Starting the other engine or requesting a tug is safer than forcing the turn with power and brake.
The underlying techniques are explained further in our practical account of how thrust, nosewheel steering and differential braking control taxi movement.
Which engine do pilots leave running?
The approved aircraft and operator procedure determines which engine remains running. The choice may depend on hydraulic pumps, generators, pneumatic supply, air conditioning, brake pressure, nosewheel steering and the direction of anticipated turns.
A pilot cannot assume that either engine is interchangeable on the ground. On some types, shutting down a particular engine changes steering assistance or requires an electric hydraulic pump; on others, the auxiliary power unit must remain available. The relevant system synoptic, pressure indications and checklist must confirm the required services before movement.
When must the second engine be started?
The second engine must be running, stable and fully checked before the point specified by the aircraft and operator procedure. Pilots allow enough time for engine stabilisation or warm-up and for starter limits, generator connection, hydraulics, bleed-air configuration, anti-ice and take-off checks.
The start is normally made on a low-workload, straight section of taxiway or while stopped. A rolling start is used only when the approved procedure permits it. Waiting until the holding point can cause rushed checks, block following traffic or leave insufficient warm-up time.
After landing, the selected engine is not shut down until the aircraft is clear of the runway and any required cooling period has elapsed. A normal take-off on one engine is not permitted; if the second engine cannot be started or does not pass its checks, the aircraft returns to the stand.
Can an aircraft taxi after an unexpected engine failure?
An aircraft may be controllable after an unexpected engine failure, but continued taxiing is not automatically safe. Fire warnings, fuel or oil leakage, a seized or damaged propeller, debris, lost hydraulics or unreliable brakes are reasons to stop and complete the abnormal checklist.
If the failure occurred in flight, engine securing and landing come first; we explain that sequence in our coverage of controlling and landing a twin after an engine failure. Once on the ground, the pilot in command may clear an active runway if control and systems are assured, but a tow is often the safer way to reach the stand.
ATC clearance only authorises ground movement; it does not confirm that the aircraft is technically safe to taxi. The aircraft flight manual, quick-reference checklist and operator standard procedures remain controlling.