EXCEEDING RECOMMENDED
OPERATING TEMPERATURES Turbine temperature equates to available power. Too hot means diminished engine performance, an in- crease in fuel consumption and a decrease in engine life.
All right, so our pilot returns and reports that he ro she exceeded the temperature limits in fl ight. Once again this is when good relations between the pilot and maintenance come into play. If this was a happy running engine before the fl ight, then the pilot will have to help us with all the circumstances involved: did he or she try to lift too much or got into a tight spot and needed an arm full of collective to get out? is he or she working in a dusty, dirty environment? We need to know what he or she noticed before and after the exceedance. If the helicopter has an exceedance reporting system then you will have accurate numbers to work with. Performance degradation occurs most often over
time. If the pilot were in a normal fl ight mode and reports escalating temps compared to earlier fl ights, there is reason to suspect a problem. They are our BFFs when it comes to troubleshooting. 1.) How much have the temps increased?
2.) Has the N1/Ng changed over a period of time? a.) An increase in N1/Ng indicates a possible eroded or dirty compressor, malfunctioning bleed valve (sticking open), and/or an air leak in bleed air supported aircraft accessories.
b.) A decrease in N1/Ng indicates a possible eroded turbine section.
3.) Did the helicopter fl y through some rain, smoke or dust? a.) Rain could turn dirt in the particle separator to “mud” restricting the airfl ow.
b.) Smoke could coat the compressor blades with an oily residue and reduce its ability to compress the air properly.
c.) Dust can erode the compressor blades, once again compromising the compressor’s ability to perform eff ectively.
Sometimes we might need to go for a fl ight to get a better feel for the problem. Ok, so we have put the pilot in informational
download, gone for a maintenance check fl ight and referred to the Ops & Maint manual. The combination of this information will help guide our investigation. This is when restraint and a good
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troubleshooting plan come into play. We need to resist the temptation of going to the most diffi cult possible reason for the engine problem and begin removing engines and components. In trouble shooting use the K.I.S. method: “keep it simple.” Start with the easiest stuff fi rst. Begin with a check of the reporting system. In other words, we need to be sure that the aircraft instruments are giving us correct readings. We proceed to inspecting the engine’s systems depending upon those results.
CORROSION Corrosion prevention is strictly a maintenance responsibility. Keeping our helicopters clean inside and out should be de rigor in our maintenance routine. Frequent rinses for the airframe and engine, plus a regular wash of the internal components of the engine, make for a happy running engine and a well- functioning helicopter. The air that the engine ingests and the compressor blades beat into submission is then converted to kinetic energy to support the lift eff orts of the main rotor blades. This air is full of stuff just waiting to attack the helicopter as well as the vulnerable engine components. The purity of the water we use, as well
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