EIGHT SIMPLE WAYS TO DECREASE THE LIFE OF A TURBINE ENGINE
Along with the fi re from the candles on my birthday cake making the “breaking news” from the Sky-Cam on all the local channels, the other thing that confi rmed I have gotten older is when I was asked for an opinion on helicopter turbine engine mainte- nance issues because I “have been doing this for such a long time.” I remember when I had long hair instead of longing to have hair, and an old guy told me to pay attention because time fl ies faster than you think. He was right. I don’t know when I became the old guy who “has been doing this for a long time” — but the calendar and a follicle-challenged head don’t lie. Now that we have established that I am now the old guy who has been doing this for a while, let’s see what maintenance issues I can share with you. Before I share my tribal knowledge, you should know that good maintenance requires a good informational foundation. First and foremost we should be more than casually familiar with the OEM’s operation and maintenance manuals (Ops & Maint manuals). Our companies spend a considerable amount of money keeping these manuals current and the OEMs have spent a considerable amount of time obtaining and printing this wealth of maintenance information in these manuals. Although tribal knowledge that is based upon our experiences and shared between us is good, it should be used in conjunction with and not instead of the instructions in the Ops & Maint manual. Next, another bit of advice for both you and your
pilot. Get to know your helicopter when it is operating as advertised. Learn and know the idle temp, and what happens to it when the bleed air accessories are utilized, anti-ice, cabin heat, and air operated particle separators. All helicopters have an acceptable vibration signature. Learn it before there is a report of a “hi-freq vibe.” We will discuss more about vibrations later. Knowing the engine oil pressure and temperature both at idle and during normal operation is another subject we will talk about in a bit. You both should know the N1/Ng rpm during normal fl ight operations. A change means something and requires investigation. Low oil pressure or high oil temperature will cause
bearings and gears to wear prematurely. If there is metal generation and it appears to be insignifi cant (based upon the Ops & Maint manual), keep the metal, record the engine time of occurrence and follow the Ops & Maint manual procedures. These are just some bits of tribal knowledge that we will expand on later.
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HelicopterMaintenanceMagazine.com August | September 2019
So here are the evil eight: PILOTS
HOT STARTS
EXCEEDING RECOMMENDED OPERATING TEMPERATURES
MIKE BRODERICK CONTRIBUTING AUTHOR
There are eight major maintenance issues. I call them
the evil eight. Any one of these evil eight will by itself infl ict
signifi cant harm upon the unsuspecting turbine engine, resulting in a reduction of its operational life. An attack by any combination of the evil eight will hasten the meeting of the turbine engine grim reaper (aka the turbine repair shop). As helicopter maintenance professionals, it is our job to recognize these eight operationally harmful events, and either prevent their occurrence or at least mitigate their activities.
CORROSION EROSION ENGINE VIBRATIONS METAL DEGENERATION ENGINE STALLS/SURGE
Surprised by this list? Good. Now that I have your complete attention, let’s examine these from our maintenance perspective. Where better to begin than with pilots?
PILOTS Pilots are at the top of the list when it comes to aff ect- ing the life of a turbine engine. From the moment they press the start button until the twist grip or throttle lever is moved to fuel cut off , even in the best of cir- cumstances, the pilot is using up the operational limits of the engine components and accessories. It is part of their job. Our job is to give them a safe helicopter so they can do their job. What are these limits? Engine life is based on a combination of fl ight hours and/or engine event cycles. Every engine OEM, based upon its research, calculates a limited number of fl ight hours and cycles to its engines. Each fl ight hour consumed moves the engine closer to a scheduled maintenance and/or overhaul event. Event cycles are separate from fl ight hours but calculated using the same research. An engine start where it reaches idle is considered an event cycle and the beginning of the hour’s time clock. Some engine OEMs also assign cycles or percentages of cycles based upon excursions into certain N1/Ng rpms. As I said earlier, in the best of circumstances the pilot is using up the assigned life
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