Turbine Engine Hygiene

I have been playing in the helicopter industry now for the past 40-plus years, mainly as a turbine-engine tech rep. I say “playing” because this has been, and continues to be, a great career with a good part of the play-time troubleshooting engine issues with my fellow technicians and pilots. During these troubleshooting encounters, I have come to expect a few things.

I own all the broken engines. It’s true! Each phone call starts with, “Your engine is either low on power, won’t start, starts hot, is vibrating like a dog shaking off water or just made metal.”

I never get a call about a good-running engine.

At times, there is a large communications gap between us technicians and the helicopter pilot. The operations and maintenance manuals are not being used as often as they should.

Even though the keep-it-simple method should apply to all troubleshooting investigations, the tendency is to start the discussion with the most complicated part of the offending system.

The common goals here are a good-running engine that reaches the established time-between-overhaul (TBO) limit, controlling direct operating costs (DOC) – along with fewer troubleshooting conversations with me). The original equipment manufacturers, the engine overhaul agencies and the operator all share these same goals.

Looking holistically at the total support of the objectives to reach TBO and control of the DOC is akin to a three-legged stool, with each leg working synergistically to maintain support of those objectives. The supporting legs of this stool are the OEM, the engine overhaul agency and the operator.

OEMs have invested extensively in a bunch of technical improvements to keep their particular engine at the top of the heap when it comes to performance, reliability and controlling their part of the DOC formula.

Those overhauling the engine are also working hard to keep their percentage of the DOC in line with innovative repair schemes and reduced shop turnaround times. But, in keeping with our three-legged stool analogy, the owner/operator has a major effect on reaching TBO, which is dependent on how and where the engine is operated, as well as engine maintenance.

There are several things that fall into the operator’s area of responsibility for a lower DOC and TBO realization. However, following my own keep-it-simple method for troubleshooting, let’s discuss the most elementary maintenance practice that will have a positive effect on engine longevity and will control costs: engine hygiene.

Engine hygiene is the process of consistently washing compressor and turbine air foils with a gas-path cleaner and rinsing with pure, distilled water.

A “wash” is defined as introducing gas-path cleaner mixed with distilled water at a controlled flow rate into the inlet of the compressor with the engine rotating at a low percentage of its Ng/N1 speed. A wash should be implemented any time the engine has been subjected to an exorbitant amount of polluted air at a programmed maintenance event or when you are troubleshooting a trending low-power issue. A wash is always followed by a rinse, defined as using pure distilled water (less the gas-path cleaner) applied in the same manner as a wash.

Use distilled water because it is the only liquid substance that is devoid of any suspended elements. This advances its ability to efficiently and thoroughly attract and remove pollutants attached to the engine airfoils. Considering today’s worldwide air pollution, there is really no “clean” air anymore, so a rinse should be accomplished after the last flight of the day, every day that you fly.

These simple procedures will pay off in an overall lower DOC.

Think of turbine engine hygiene like brushing your teeth. You brush before you go to bed to remove the food particles accumulated during the day. If you wait until morning, the damage will be done. Same thing with your turbine engine: If you wait until morning before you rinse the engine, it is too late and the corrosion will have begun.

In the words of my dentist, “Only clean the ones you want to keep.” R&WI