EOTI: What you need to know about Engine-Out Taxi-In

Engine-Out Taxi-In (EOTI) is a fuel efficiency best practice that can be applied during the taxi-in phase, i.e. the taxi from the landing runway to the block. Another best practice called Engine-Out Taxi-Out happens during the taxi from the block to the takeoff runway; it will be described in a future blog article.

Its principle is to perform this taxi with one or several engines (in the case of four engine airplanes) shut down to save fuel.

To preserve engine life, it is however important to respect the engine cooldown time prescribed by the manufacturer before shutting down an engine. As a consequence, Engine-Out Taxi-In is only applicable when taxi-in duration is longer than engine cooldown time.

Figure 1: Engine-Out Taxi-In Best Practice

Wondering what are the typical fuel savings for shutting down one engine?

The chart below shows what are the typical fuel saved and the typical cooldown time, depending on the aircraft type:

Figure 2: Typical fuel saved and cooldown time, depending on the aircraft type

Keep in mind that the math of airlines' fuel efficiency consists in multiplying small quantities by big numbers. This means that even the last seconds count.

Let’s take the example of a very short taxi of 3 minutes and 45 seconds on an A320 or a B737 that have an engine cooldown time of 3 minutes. You might consider that these 45 seconds don’t make such a difference.

Yet these 45 seconds of single engine taxi represent 45 s x 4kg / min = 3kg on each flight. Now imagine you operate a mere 30,000 flights per year, the total saving would be 3 kg x 30,000 flights = 100,000 kg.

Applying Engine-Out Taxi In can represent challenges for pilots, mainly for the following reasons:

• An uphill taxiway (for example in Amsterdam-Schiphol airport) can make it unapplicable

• During the final turn, the fear of not having the right engine still on

• Overconsumption at the stops & go

• Runway crossings: engine should be shut down only after having crossed the runways, if any.

As a pilot, if you want to apply Engine-Out Taxi-In without compromising safety, here are some tips:

• First, check your airline guidance on how to perform Engine-Out Taxi-In and clear procedures that explain when to apply it or not.

• Ask for tangible facts about the feasibility conditions of the Engine-Out Taxi-In best practice at the different airports of your network. 

• Communicate regularly with the fuel operations team and all your doubts about the procedure and its safety considerations.

• Ask for a tool (such as a mobile app) which enables you to have a personal and confidential feedback on each of your flights and best practices.

If we take the example of Ukraine International Airlines: before using SkyBreathe® MyFuelCoach™, as can be seen in February 2017, less than 20% of Ukraine International Airlines’ pilots were using Engine-Out Taxi-In.

Using the mobile app, by October 2017, that had risen to nearly 80%:

Figure 3: Engine-out taxi in application from beginning of application
of SkyBreathe® MyFuelCoach™  application for pilots