Airbus A320 Pilots Routinely Shut Down One Engine During Taxi to Cut Fuel Use

On modern Airbus A320 family aircraft, it is increasingly common to see one engine completely shut down during taxi operations, a deliberate procedure adopted to cut fuel consumption on the ground. By operating only one engine while maneuvering on the taxiways from runway to gate or vice versa, airlines achieve meaningful reductions in fuel use and emissions at airports. Airbus has formally incorporated the single-engine taxi procedure as a standard operating method for crews.

This approach was initially an optional cost-saving tactic used mainly by ultra-low-cost carriers or during periods of airport congestion but has evolved into an industry-wide recommended practice. Airbus moved single-engine taxiing from supplementary guidance to the main standard operating procedures in its Flight Crew Operating Manual, fundamentally adjusting the manufacturer’s baseline for ground operations on the A320 family.

The rationale behind taxiing on a single engine centers on fuel efficiency. Aircraft engines like the CFM56 powerplants on the A320 are optimized for cruise flight and operate inefficiently at idle thrust levels typical on the ground. Running both engines at idle during taxi wastes substantial amounts of fuel, so shutting one down reduces this fuel burnout almost by half. Quantitatively, this corresponds to approximately 8.8 pounds (four kilograms) of jet fuel saved per minute of single-engine taxi time.

From a performance perspective, the A320’s engines produce ample thrust to propel the plane on the ground with just one engine running. The CFM56-5B generates 27,000 pounds (120 kilonewtons) of thrust at idle, enough to keep the aircraft moving at typical taxi speeds of 15 to 20 knots without difficulty. Pilots often need to apply brakes during single-engine taxi because idle thrust from just one engine is still sufficient to accelerate the aircraft on flat surfaces.

A technical hurdle emerged due to system demands such as electrical power, hydraulic pressure, and air conditioning usually supported by both engines and the auxiliary power unit (APU). The APU itself burns fuel, partially offsetting savings from single-engine taxi. However, a modification called Single Engine Taxi Without APU (SETWA) enables aircraft to operate the taxi without the APU running by powering fire detection and cabin systems solely through battery buses, amplifying fuel savings and carbon footprint improvement.

After landing, pilots cannot immediately shut down an engine because of thermal stress risks, notably rotor bow—a damage caused by rapid temperature changes in hot engine turbines. Instead, they follow regulated cooldown procedures before shutting down the second engine. This careful thermal management combined with coordinated systems design and operational changes has allowed single-engine taxi to become a safe, routine practice enhancing airport environmental sustainability.

This shift is part of broader efforts across the aviation industry to mitigate ground-level emissions and reduce operating costs. While cruise emissions remain the largest contributor to an aircraft’s environmental impact, cutting fuel use during ground operations adds up to significant savings when aggregated over thousands of flights. Single-engine taxiing is proving an effective lever, especially for short-haul carriers with significant ground time.

Airbus’s endorsement and standardization of this practice set a precedent followed by airlines worldwide, integrating single-engine taxi into their standard operating manuals. It reflects a growing trend of scrutinizing every phase of flight and ground handling for efficiency gains, reaffirming the aviation sector’s commitment to reducing its environmental footprint through operational innovation rather than waiting solely on technological leaps.

Introducing the SETWA upgrade further optimizes these benefits by allowing the APU to stay off during taxi, eliminating additional fuel consumption otherwise needed to maintain aircraft systems. This multi-layered approach to taxi operations demonstrates how careful systems engineering and operational policy changes can dovetail to produce tangible environmental and economic benefits for modern airliners.