Are you using ECTM? You should be.
Engine Condition Trend Monitoring (ECTM) is a Pratt and Whitney-endorsed program by which PT6 Hot Section Inspection (HSI) intervals may be accomplished on an “as needed” basis instead of on an hourly basis. The first step in ECTM is recording all engine parameters when steady in cruise flight. Unless that raw data is then entered into the appropriate computer program that will print graphs of the three parameters being tracked (ITT, N1 or Ng, and Fuel Flow, abbreviated Wf), extending HSI times is not allowed. Additionally, if the data recording does not start soon enough after the previous HSI or contains gaps in which data was not recorded for too many hours, ECTM becomes invalid. Due to these constraints, very few if any non-commercial King Air operators use ECTM for the purpose of possibly extending their HSIs. That is fine with me. Afterall, if you’re flying only a hundred hours or less a year, do you want to go over 18 years without examining the engine’s innards?
So why did I write that you should be doing ECTM? I did so because ECTM has another, and perhaps more widely held, meaning: The recording of engine cruise parameters even though there is no intent to plot them on a graph nor use them for an HSI extension. In my opinion, the regular recording of engine parameters in cruise is quite important. Let me explain.
Memory can be a fickle thing and the older we are, the more fickle it becomes! For most of us, the ability to view, record, and store all of the engine parameters that ECTM tracks is an impossible task. “Let’s see … what was the RH Fuel Flow the last time I flew at FL250? How did it compare with the LH side? More? Less? By how much?”
On the other hand, if we have a written record of all engine parameters taken at least once per day while steady in cruise, memory is no longer required. We can merely look up the answers. Here’s an example of why that is useful.
A few years ago, the C90A that I manage for its owner developed a larger split in the ITT readings than I was used to seeing. The change was not large, a little less than 10° C if I recall correctly. Yet over a period of three or four flights the change never went away. It was definitely something different from what I had observed previously. I did a Flow Pack check – thinking that perhaps one side had become very weak, leaving more P3 air in the engine and hence making it run a bit cooler – but the packs seemed normal in all respects. By looking at the ECTM raw data records that I had been keeping, it became instantly obvious that the shift in ITT readings showed up on the first flight in which ECTM readings were recorded after our previous maintenance event in which Phase 3 and 4 inspections were done together. Back to the shop we went and in short order a relatively minor change in the ITT wiring harness was found and corrected.
Had we not had past readings to analyze, it would not have been obvious that this change came on suddenly following work at the last shop visit. In fact, the ITT change was so minor and all engine parameters were still well within limits that it would have been very easy to shrug our shoulders and merely accept the readings as normal.
Recently a King Air owner/pilot friend of mine had a shock when a badly deteriorated Hot Section was discovered during a routine Phase inspection. The maintenance personnel believed that the ITT was reading much lower than the correct value and hence the pilot had been running the engine much too hard and too hot … leading to the need for all new CT (Compressor Turbine) blades. There are 58 of those beauties and they aren’t cheap!
Unfortunately, my friend had not been recording ECTM readings in the past. Had that record existed I am positive it would have been obvious that the maintenance shop’s hypothesis was incorrect. If more power had suddenly been used due to a defective ITT reading, ECTM should have shown evidence of higher torque, more fuel flow, higher N1 speed and higher airspeed. Sadly, without written records, no firm argument could be made that using an incorrect, higher, power setting was not the cause of this expensive engine deterioration.
Some professional King Air training organizations provide a form for recording Engine Condition Trend Monitoring. If you have not yet added a version of that form to your flight records, please do so now. I suggest having a three-ring binder in the cockpit with one of its sections containing some ECTM forms. After leveling at your typical cruise altitude and setting power correctly based on the torque that the POH shows for your Pressure Altitude and Indicated Outside Air Temperature (IOAT) (see the section starting on page 159 of The King Air Book) let things stabilize for at least five minutes then fill out a line on the ECTM form. Do this for at least one flight per day and if you have a really long day with multiple flights, try to fill out a line at least every five hours or so. Taking the readings at any altitude is OK, but the results are usually more meaningful if you use the same altitude as often as practicable.
If you have no ECTM form available, email me at email@example.com, ask for one, and I will send my version to you.
Yes, there is a chance that the “work” of filling out the ECTM form will be for naught … never will an anomaly show up that can utilize the benefit of comparison between now and then. However, friends, I strongly believe that your effort will not be wasted. Instead, in 99% of cases, being able to compare accurately now and then is tremendously helpful. In the long run, it will almost assuredly save you some maintenance money.