The Great Engine Wash Debate!

In Fuel Efficiency, we try to operate light(est), (most) efficient aircraft in (the most) efficient ways. In this, the efficiency of the airframe-engine combination is one important pillar; the aerodynamic efficiency of the airframe and the propulsive efficiency of the engines are key drivers here.

Apart from discussions on surface (energy drag) and systems (energy bleed), one main topic will always be the maintenance of air & gas paths in an engine; these paths become less efficient over time which results in deteriorating performance of an engine as seen in various engine temperature indications and margins and higher in (specific) fuel consumption. Engines start to burn more fuel for the same thrust performance (resulting in higher costs and less range), or worse, start losing performance altogether.

Different engines age differently over time due to factors like design, usage, environment and maintenance inputs. Blades get dirty and lose aerodynamic efficiency. Soot and other deposits get everywhere, openings get partially or completely plugged, and so on. Exactly how these processes happen or what effects can be seen over time is available in the literature (one has to dig, though), but what is an apparent closely guarded secret is some method or form of metrics designed to predict how an engine is going to deteriorate over time, in a given environment, under a given usage.

True, most aircraft beam specific data reports which provide clues and form part of the aircraft health / engine health monitoring programs. In some cases this (limited) information is actually used to drive improvement programs as well, rather than being limited in use by the powerplant planning department only.

To counter performance (and safety) deterioration, aero-engines are cleaned (fan) and washed (core) from time to time. Various approaches exist: cold wash, warm wash, CO2, with or without detergent, and using different types of equipment from different suppliers. The cleaning interval (the time between cleanings) varies greatly from operator to operator, and can range from every A-check or less to once or twice per year. Cleanings mostly happen off-line during a maintenance break in flying or sometimes on-line during a turn-around.

To be able to put numbers (and more) into an engine type / environment / usage specific model would be a great step forward. I’m thinking of building such a model for use in my FE programs so that colleagues can have a benchmark in deciding what the best wash interval could be for their fleets.

So here’s my Big Ask:
If able, please share your observed experiences or practices in this post or, if preferred, in a PM. Types of engines, types of operation, use of thrust settings during take-off, average FH/FC numbers, wash and clean intervals and planning based on calendar/FC/FH or other, etc. The more information, the better. I’d appreciate input from operators, but also from OEMs of course.

I will use your information to help build the model and, once completed, I will share the model with you in return. I will also post an update with some benchmarking baselines.

Or… does such a model already exist?
I wouldn’t be surprised; surely OEMs will have developed something to base their PBH contracts on, right? 😉

In any case- many thanks in advance!

#APM #EngineHealth #EngineEfficiency #EngineWash #EngineCoreWash

One Reply to “The Great Engine Wash Debate!”

  1. Greetings !!
    I just gone through the post and saw an interesting plot of output loss vs fired hours.
    I observed that output loss delta ( pre and post wash )immediate after new/major OH engine is quite steep compared to successive washes. I understand 1st delta loss has many other dominant factors than only due to dirt / deposit. In true sense Ideally 1st delta plot should be in line ofsuccessive deltas plot to demonstrate comparable output loss due to cleanable deposits.
    Warm regards
    Kuldip Singh

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