StorkJet’s Tips #5 – How to reduce your engine maintenance cost with thrust reduction?

 

Take off and climb can be performed with full or reduced thrust. Let’s think about the consequences of using 100% thrust during take-off. Fuel consumption can even be lower in such a case because the optimum flight parameters are reached faster. However, higher power means hotter air flowing through the turbines and this, in turn, causes faster engine degradation. The cost of maintenance goes up and compared to the cost of a few kilograms saved fuel, 100 % thrust turns out less efficient. In addition, in the long term using full power, the deteriorated engine burns more fuel than before causing future flights more and more expensive over time. Therefore, it is worthy to use the most reduced thrust as possible.

The increased cost of maintenance generates a saving potential that can be converted into real savings by using reduced thrust. AdvancedAPM and FuelPro allow tracking the historical thrust reduction and detecting the group of flights that have not been optimized yet. Let’s see in more details how it is done and what exactly you can expect from having StorkJet’s software!

 

General benefits resulted from thrust reduction

 

When using higher thrust than required, the engine parts from the hot section wear out faster. Applying thrust reduction results in:

  • longer-term between two maintenance services, when the engine must be dismounted and precisely inspected,
  • parts renovation instead of premature, expensive material replacement.

 

The cost of service, parts repairment, and replacement during maintenance is about 5% of the airline’s total operating costs. By applying a severe thrust reduction policy, we can keep this contribution as low as possible.

 

Extending engine on-wing time

 

In the past, engines had to be dismounted and overhauled within the same periods, independently of their factual performance. It was happening regardless of thrust reduction that preserves rapid engine deterioration. Nowadays, it is ineffective to do it in such a way because the condition of the engine can be tracked almost in real-time thanks to built-in sensors. They measure key parameters such as the spool’s rotational speed, vibrations, temperatures, and pressures. Using AdvancedAPM, powered by machine learning models, the operator can observe how these parameters change over time due to deterioration. It supports the engineers in monitoring the signs of engine degradation that could require mechanic’s intervention. Because these symptoms can be postponed by frequently applied thrust reduction, as a result, the operator reduces the number of services by prolonging engine on-wing time (the interval between two next maintenance actions) and gains savings.

 

Keeping good performance of Life Limited Parts (LLPs)

 

The engines’ parts operational usage time is usually limited by the number of flight cycles. After this value, the part must be replaced. By applying thrust reduction systematically, operator:

  • increases the probability that the LLPs will withstand their designed number of cycles,
  • decreases the number of required performance restorations during its lifetime.

 

Below you can find how the engineers can track applying the thrust reduction policy using AdvancedAPM.

 

How is the thrust reduction converted into savings?

 

Thrust reduction saving potential evaluation is based on Severity Matrix (attached to the FHAs – Flight-Hour Agreements) provided by the lessors to the commercial aircraft owners. It translates the percentage of thrust reduction to the maintenance costs depending on flight leg and the type of environment (e.g., dusty regions deteriorate the engines faster). The maximum possible saving potential is the difference between the maintenance costs when the highest thrust reduction is used and the costs of full thrust. Using FuelPro the operator can track the actual potential based on the already performed flights.

The above chart represents the average saving potential for a single modern turbofan engine mounted on today’s medium-range narrow-body aircraft. Using the highest possible thrust reduction, the operator can save as much as 110 US dollars per flight. Let’s assume that there is a fleet, which size crosses 50 aircraft. The operator wants to improve the thrust reduction policy from 17% to 24% on average. Therefore, yearly above 600,000 US dollars can be saved (6$/flight * 100 000 flight/year).

As you can see, the following conclusions can be drawn from this – applying thrust reduction systematically not only helps reduce overhaul costs but also can bring a huge amount of savings because of increased engine life. In general, it keeps the good performance of your fleet in a long period of time.

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