SavvyAnalysis Puzzlers

For this back-to-school Puzzler I chose two very different scenarios. Let’s apply our analytical skills and see if we can solve them. First up is a normally aspirated SR-22 with a Continental IO-550-N. This is a test profile flight, with a series of GAMI sweeps followed by a lean-of-peak mag check. Here’s the whole flight, and the cyan trace is fuel flow. We’ll get to that giant purple spike in a bit, for now let’s start on the left. EGT 6 is high right out of the gate, stays high through the runup mag check, is lowest when FF drops into the 9 GPH range, and is high again after the tests. CHT 6 changes rank and direction of movement along with EGT 6, and that’s a characteristic of a clogged injector. Also notice that as the CHTs change cylinder 6 is always behind the pack. Slower to heat and slower to cool. If we zoom in on the GAMI sweeps, we can see that 6 is first to peak when FF leans, and last to peak when FF richens again. Also a characteristic of an injector clog. Back to the big picture, what else is going on? CHTs 1 and […]

While channel surfing recently I tuned into the opening scene of 12 Angry Men. It had been years since I had seen it, so I decided to give it a go. It’s not a flashy movie, it’s in black-and-white, and except for the final scene on the courthouse plaza, the movie takes place in one small jury room. The artistry of the movie is the story, the acting, the camera placement, and the editing. Henry Fonda leads a powerhouse cast trying to reach unanimous verdict in a murder case. On the first vote, 11 vote guilty and Henry votes not guilty. Spoiler alert: over the course of the movie Henry stands his ground, questions the evidence and one by one the other jurors re-think their positions and change their votes. In the end they all vote not guilty and go home. My uncle used to say about my aunt that she got most of her exercise by jumping to conclusions. We’ve all probably encountered a mechanic who heard a phrase or two and was immediately convinced of what was wrong with the airplane. Psychologists call it confirmation blindness — our tendency to accept evidence that supports our conclusion and reject evidence that doesn’t. […]

The web says that big data is a catch-all phrase for data sets that are so large that traditional processing applications are inadequate. Even though Savvy Analysis is just approaching its 3rd birthday, let’s call it a traditional processing application. On my last cross-country flight, my passenger was a web developer, and as we scanned for traffic, we brainstormed how the coming ADS-B rule might change engine data analysis. In the 1990s I enjoyed hearing Scott McNealy, one of the founders of Sun Microsystems, talk about smart appliances, and how a refrigerator equipped with wi-fi could monitor its systems, recognize the signs of an impending compressor failure, log onto the net, order the part, then schedule the service appointment – all without human intervention. So my friend and I tried to apply that to flying. Imagine scooting along an airway, and along with the real-time weather and real-time traffic, you have real-time engine data available. Obviously you have it already – a whole panel full – but in addition to each gauge displaying its own information, you would have a real-time graphic depiction of EGTs, CHTs, FF – all the information from your data monitor, on one screen. So when you perform […]

The comedians are fond of saying “timing is everything”. I think the quality of the material is pretty important, too, but I guess their point is that bad timing can ruin good material, and that comedy is a performance art. You might expect an article about timing from the analysis side of Savvy to be about mags, flame fronts, top dead center, and getting the most bang for the buck from your engine. This one, though, is suggestions from us about how to get the most bang for your buck out of SavvyAnalysis. When To Upload Flight Data First, let me remind you that all flight data uploaded to SavvyAnalysis is scanned for the EGT signature of a failing valve. That happens without you having to ask. If we see the pattern we will notify you. That’s true whether you’re a Savvy Maintenance client or a SavvyAnalysis Pro client. The FEVA scan has been at work for just under a year now, and we have spotted and reported the pattern to dozens of clients. So if you’re a client who only uploads flight test profiles and anomaly flights, but not normal everyday flights, hopefully the automatic FEVA analysis gives you […]

It’s wedding season. When my wife hosts a wedding shower, she organizes a game. She puts small kitchen items into brown paper lunch bags – one per bag – and ties a ribbon around each one. Each guest ties the ribbon around their neck and hangs a bag down their back. The other guests feel the bag and try to figure out what’s in it. They write down the answers, eventually all the bags are opened and someone wins. Part of me thinks this game is a remnant of a time when women were expected to know about kitchen gadgets and isn’t it a little archaic to be playing this in 2015? Maybe – but the women in the group who have earned MDs, PhDs, JDs and ATPs seem to have just as much fun with it as anyone else. I guess knowing about kitchen gadgets was just one more thing they learned on the road to liberation. I thought of this game recently because sometimes looking at engine data is like feeling the bag. You’re pretty sure of your conclusion, but you’d love to open the bag and know for sure. Fortunately this month’s Puzzler gives us two opportunities […]

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 […]