SavvyAnalysis Puzzlers

Last week I heard an oldie but goodie. A couple of veteran pilots were talking to a new pilot about flying single engine planes over rough terrain at night. One of the high-timers said “If the engine quits, you pick a spot, turn on the landing light and if you don’t like what you see you turn it off again.” We all know the risks of flying, and the stats say that recurrent training and good maintenance help mitigate those risks. If we were – as the ad says, “stupid rich” – we’d have a team of mechanics check the airplane after every flight, like a Formula 1 team, and pronounce it ready for the next flight. The next best thing is to look at the engine data.  Usually in a puzzler we use an example where the data identified a problem and suggested a remedy. We’ll get to that, but before we do I want to spend a little time on questions we can’t answer, or won’t answer. Even if the team of mechanics performed their post-flight inspection and gave a thumbs-up, we’d still perform a thorough pre-flight inspection before yelling “Clear prop!” FAR 91.013 says we have to, […]

Spring training is about to wrap up, and opening day is almost here. Last week a friend and I made our annual pilgrimage to Glendale, AZ to immerse ourselves in baseball. Four games in 45 hours. At least in Arizona, spring training and GA are good neighbors. The White Sox/Dodger park is next to Glendale, the Reds/Indians park is next to Goodyear, Padres/Mariners is not far from Deer Valley, Giants/Rockies is across town near Scottsdale and Falcon. So not only do you get a baseball game, you get to watch the traffic pattern, and a little higher and further away are the constant arrivals and departures at Sky Harbor.  I know a little bit about baseball, my friend is a walking almanac and former baseball writer. We sat behind a lady keeping score – on paper in a spiral notebook – and I wondered if I could explain engine data analysis to her faster than she could explain the arcane symbols of scorekeeping to me. Her language has been around a lot longer than mine, but it’s interesting to think that in both cases, if you know the language, you can look at the data and recreate the event in […]

Flying is full of acronyms. GUMP, ADS-B, BFR, NTSB, ASRS, AOPA, EAA, NBAA, GA, WOXOF, NORDO, GPS, ILS, VOR, FARs, the 6 T’s – the list goes on. Add online chatting and texting and it’s almost TMI. In engine data analysis we have our own acronyms, and the last page of the Savvy analysis report form explains what they mean.  In this puzzler I want to cover GAMI, GIGO and FOD. Not actually GAMI the company – whose research and innovation gave a much-needed boost to GA when it needed one. GAMi as in spread – the calculation of mixture distribution determined by comparing the EGT peaks as fuel flow changes. GIGO stands for garbage in garbage out, and FOD is foreign object damage.  With GAMI sweeps, we get the most reliable results by beginning the test at 100º F rich of peak, then leaning to the onset of engine roughness, then richening back to the setting for 100º F ROP. We like to have a series of three such sweeps for reliable analysis. Here’s a set of sweeps with excellent pace, and consistent rich start points and lean end points. (The blue trace is fuel flow.) Now let’s zoom […]

 I’ve been looking at stock charts for a long time. I mean a REALLY long time – like before the Internet when they came in big bound books. I’ve also been reading music for a long time. So when the concept of engine data analysis came along, I found the concept familiar. In music, you find the prettiest notes in the middle of the instrument’s range. High notes, low notes and giant skips in pitch tend to stick out. The veteran stock chart watchers look for things like double bottoms, triple tops, breakouts, volume surges, price gaps, and compare that with everyday ordinary behavior. So what does any of this have to do with this month’s puzzler? Patterns and expectations. With engine data analysis, there are patterns we expect to see and when they’re not there we have to figure out why. What matters to a stock trader is not what the fundamentals say is supposed to happen to the price, but what buyers and sellers do with their money – and that’s what you see in the chart. In studying an orchestral score you look for melody, harmony, counterpoint and dynamics to determine what the sound will be. With engine data, we […]

Ronald Reagan used to say “Trust but Verify”. He was talking about Intercontinental Ballistic Missiles, but the philosophy works for data from engine data monitors, too. While we sit comfortably in the cockpit scanning the gauges, our data-gathering probes and cables are out there trying to work next to some hot metal in wind that qualifies as an F5 tornado. We give the data the benefit of the doubt, but sometimes the data makes us scratch our chins and look for a way to verify.  Normal, Bold, Hide and Isolate Just like snake oil salesmen don’t start their pitch with “Everything I’m about to say is !@#$%^&”, a failing probe or a loose connection will probably keep sending data and it’s up to us to separate truth from fiction. Let’s look at some examples. Take a look at the data from this IO-550-N. No, it’s not the new 3-cylinder version – we’ve set up the chart to display only the traces for EGT and CHT 1, 2, and 4. When you notice something unusual, it helps to isolate that trace, but it also helps to include a “normal” trace for comparison. If you haven’t used the chart tools, this might […]