SavvyAnalysis Puzzlers

In most of the Northern Hemisphere it’s the time of year to think about icing. If your airplane is certified and equipped for FIKI – flight into known icing – an encounter with ice isn’t the emergency that it is for the rest of us. When an engine data probe fails in flight, most of us will just press on to our destination with the bad data and repair the probe as soon as possible. As I looked through this month’s data I saw a lot of cases where the pilot had bad or unreliable engine data before takeoff, and elected to launch anyway. One of them is mine. On a recent trip my JPI 830 showed a BAD PROBE alert, so I continued to my home airport, and a few days later I flew the airplane to the avionics shop which, fortunately, is only an eleven minute flight. Because the 830 is not a primary instrument, I decided I was absolved from FAR 91.213 – the rules governing in operative equipment and minimum equipment lists. I decided that placarding the 830 “Inoperative” would be stupid, since 90-something percent of it was reliable and useful. As confident as I was […]

I never had the guts to do it, but I sure thought about it more than once. Maybe you’ve done it or thought about it. You know – you’re in a mandatory meeting about some new company policy or initiative and the presenter is droning on from a pamphlet – or worse, a PowerPoint that you can read yourself – and the cliches and buzzwords start flying. Maybe it’s unique to your industry, or maybe it’s just general management and productivity cheerleading. The first participant to recognize five cliches in a row stands up and yells “Bingo!” – then more than likely goes back to his office, cleans out his desk and starts looking for a new job. Bingo Fuel has a specific meaning to Naval aviators who are down to the minimum fuel required to ensure a safe landing. My SavvyAnalysis colleague Paul Kortopates, who is Lead FAASTeam Representative and San Diego IMC Club CFI and Co-Coordinator, recently reminded civilian pilots that they should be saying “Minimum Fuel,” even though it’s not as cool as saying “Bingo.” Controllers JO 7110.65 and AIM 5-1-10 defines: “minimum fuel” indicates recognition by a pilot that his/her fuel supply has reached a state […]

Sometimes when I see something odd in real-time engine data during a flight, I can almost hear the voice of Vic Perrin saying “There is nothing wrong with your TV set. We are controlling transmission. We will control the numbers you see. You are about to experience the awe and mystery which reaches from the inner mind to – The Outer Limits.” If you too are a fan of the show – and yes I have the four double sided-DVD collection – you know that some of the plots didn’t require too much willing suspension of disbelief, but many did. Still, nothing on The Outer Limits could hurt your TV, or cost you a bunch of money, or maybe even threaten your life. Engine data might be telling you about something that could – or it could be a harmless distraction. Let’s see what we can learn from this month’s collection of data. Let’s warm up with data from a Cirrus SR 22 with a Continental IO-550 and data from an Avidyne with a 6 sec sample rate. My standard layout of EGTs on top, then CHTs, FF and Oil Temp. The issue is CHT 4. It had been high on […]

The Farmer’s Almanac says that the phrase Dog Days wasn’t originally about canines panting in the heat, it was about the appearance of Sirius the Dog Star and its reminder to ancient Egyptians about the annual flooding of the Nile. I like the dog days because a clear night sky gives you good views of Mars, Saturn, Jupiter, and if you stay up late enough you get a meteor shower for an encore. Ok, but it’s going to take a literary Lomcovák to connect this astronomical musing to engine data analysis, and here it comes. Patterns. Only the most astute of the ancient Egyptians would have noticed or remembered that Sirius was in the sky the last time the Nile flooded, too. And the time before that. It takes a while for a pattern to emerge and be recognized, and then you want evidence to support it or refute it. In previous Puzzlers we’ve seen examples of clogged injectors, weak and non-firing spark plugs, sticky valves, failed probes and other common patterns. Here’s one we haven’t seen in a while. This flight is from a Cirrus SR22 with a Continental IO-550-N and data from an Avidyne with a 6 sec […]

When guitar strings break there’s no lingering doubt. When an old-style incandescent light bulb fails you might get a bright flash before the darkness, or maybe just the darkness. Either way, no doubt. These are instant, unconditional failures. Then there are failures that are harder to recognize because they evolve over time, like an attitude indicator or DG spinning down after a vacuum pump failure. As I reviewed this month’s engine data looking for Puzzler candidates, I found some patterns that I hadn’t seen before. I’m always mindful that patterns are easy to spot in the luxury of post-flight analysis, and much harder to spot in real time. Someday soon, once we’ve updated our avionics to comply with the ADS-B deadline, I suspect we’ll have a device in the cockpit that can display cumulative data for the entire flight, not just the number of the moment. Or, maybe you’ll upload to Savvy Analysis in real time and have a fast enough web connection to display our page of your data as you fly. Meanwhile, let’s look at these patterns and remember that for the pilot, they were a series of constantly-updating numbers that got processed with all the other incoming information […]

Okay I’ll admit it. The first time someone showed me the selective attention video – the one where the gorilla walks through the teams passing basketballs – the setup was that there was a really nice prize if you could count the exact number of passes by the white team, and an even better prize if you could count the total passes by the white team and the black team. Being the competitive sort that I am, I wanted to win the even-better prize, so I fixed my concentration on shirts and basketballs and completely missed the guy in the gorilla suit. We have psychologist Bluma Zeigarnik and her research from about ninety years ago to thank for showing that we tend to focus on uncompleted or interrupted tasks better than completed tasks. Could this apply to your approach to processing engine data information while you fly? Let’s start this month with data from a Cessna Cardinal with a Lycoming O-360 engine and data from a JPI 700. Fuel flow is not logged, so EGTs on top, CHTs below that – with the red alert line at 400º F – and Oil Temp below that. It’s painful to look at […]

Last October I mentioned Eastern Airlines flight 401, which crashed into the Everglades in 1972 because all three crew members were fixated on a failed landing light. I first read about the importance of that flight, and so many others, by reading books and columns by Richard L. Collins, who we lost in April. I think I’ve read everything he wrote at least once. Before he installed an engine data monitor in his beloved P210, Collins saw the value in tracking engine parameters and printed up blank sheets for his lapboard. Here’s a screenshot from the 01:19 mark of his Engine Management video for Air Facts. Yeah, that CHT of 420-425º got my attention, too. I’m willing to give him the benefit of the doubt and suppose that it was the highest reading of the needle on an old Alcor one-at-a-time CHT gauge. And since this was pre-digital data gathering, it was pre-GAMI and pre-resurgence of LOP cruise, when TCM’s CHT redline of 460º was unchallenged. And I’m not positive these numbers are from N40RC – the P210. The higher oil pressure number from a few frames earlier suggests it might have been from the Lycoming engine in his Cardinal […]

Strong passwords, frequently changed passwords, biometric scans and two factor authentication are some of the technologies developed to keep information accessible to those who should have it, and away from those who shouldn’t. Every time I have to track down my phone to fetch a number and type it into a webpage, I remind myself what a small price that is compared to recovering from a data hack. When I train a new engine data analyst, we spend a lot of time on authenticating the data. Is it friend? – useful data that will help engine performance or diagnostics – or foe? – data that will distract and confuse and perhaps fixate. In the quiet of analysis we can usually find data to cross-reference and compare. That’s harder to do with a handful of airplane, but knowing what to look for makes it easier. While the majority of Savvy’s analysis work detects mixture distribution problems and weak spark plugs, we sometimes get data from unusual events. Let’s start with a static runup from a Cirrus SR22 with a Continental IO-550-N engine and data from an Avidyne with a 6 sec sample rate. EGT on top, FF and MAP below that, and oil […]

I just filled out my bracket for this month’s college basketball tournament. If you live outside the US, or you don’t follow sports, it’s an annual ritual where American sports fans try and guess which of 64 teams will win every game over the course of a few weeks. There’s always one upset of a favorite and there’s usually a small school that defies the odds. So while it’s remarkable how the teams with great coaches show up year after year, the bracket with all the favorites rarely wins. It’s the outliers that make it a challenge. Someone said piloting an airplane is hours of boredom punctuated by moments of sheer terror. I don’t see how anybody who has a handful of airplane could be bored. If you’re VFR there’s so much to look at – and look for – and if you’re IFR and bored you’re dangerous. Terror is defined as extreme fear, and I’d argue most pilots log recurrent training and review emergency procedures so that we don’t fall victim to extreme fear when something bad happens. Sully, Jim Lovell, Al Haines – that’s why they’re heroes. If you’ve successfully handled an in-flight emergency that could have harmed […]

Sometimes the data that I gather to write about has an obvious theme. Sometimes I sort of manhandle them into a common theme. This month, it’s more of a collection of independent cases. First up is data from a Cirrus SR22 with a Continental IO-550-N and data from an Avidyne with a 6 sec sample rate. What’s wrong with this test profile data? Nothing. Sometimes we get test profile data with GAMI sweeps that are too fast, or don’t start rich enough to define EGT peaks, or the mag check is too short or the fuel flow on the mag check wasn’t lean enough to unmask weak spark. So when I saw this excellent example of a test profile, I thought I should share it. What makes it great? The consistent rate of change of fuel flow in the sweeps and enough time on each mag with lean of peak fuel flow lets us draw reliable and meaningful conclusions. Our instructions for the mag check are one set of BOTH-L-BOTH-R-BOTH, and here we have another L and R. It’s not necessary, but it’s nice to have. Once quick note before moving on. My default setting is to display 4 charts […]

One of the most famous and inspirational sayings in aviation and aerospace is “failure is not an option.” If you like the Ron Howard movie Apollo 13, chances are you’d like the book – or the Audible version – about the American space program from the point of view of Mission Controller Gene Kranz. Despite the saying, we know that there are failures for owner-flown piston aircraft airplanes. We know that mechanical parts do fail, and we know that some failures are maintenance-induced. When they happen, we need to be able to recognize them, and hope we don’t need a roomful of brilliant and resourceful engineers to get us safely back to Earth. Let’s start 2018 with a scenario that was easy to solve, and would have been just as easy to keep from happening in the first place. Data is from a Piper Turbo Arrow III with a Continental TSIO-360 engine and data from a JPI 830 with a 2 sec sample rate. Some history — mixture sweeps showed a consistent GAMI spread of 0.9 – 1.1 GPH. That’s higher than we like to see for running 50º LOP in cruise. So the owner decided to install a set […]

by Paul Kortopates One of the more common turbo problems we see are erratic fluctuations in MAP. Below is a plot of MAP (the red trace) & Altitude (the yellow trace) of a Cirrus. Although the data is a bit coarse with a 6 sec data sampling rate, when zoomed in we could see MAP fluctuations as large as 2.5”. Looking at some recent past data in the next figure that shows MAP data from takeoff to 15,000’, we can see prior MAP data is actually quite stable as we would expect. The engine data we’re looking at above is from Tornado Alley SR22 Turbo Normalized IO-550. The SR22 TAT Turbo Normalizing System is diagramed in the next figure below, and consists of dual turbo chargers and dual wastegate actuators controlled by a single absolute pressure controller regulator. The absolute pressure controller (APC) continually monitors the turbocharger’s compressor output, also known as “upper deck pressure” (UDP) and regulates it through the wastegate. The APC attempts to maintain a constant UDP by controlling the two wastegate actuators. The wastegate actuators have a butterfly, much like a throttle butterfly, to control the amount of exhaust gas that is allowed to bypass the […]

In math, a conjecture is a statement you believe to be true based on observations. That sounds like something you could trust and act on. Webster’s says it’s an inference formed without proof or sufficient evidence. That sounds like conclusion jumping that you’d be inclined to dismiss. When we perform engine data analysis, we strive for the math interpretation of the word. It’s interesting that but for “ect” conjecture would be conjure, which is to evoke a spirit by means of magic or ritual. We hardly ever do that. Analysts have an advantage when we’re looking at the data – we know how it ends. As pilots watching the data develop in flight, we don’t have that luxury, and have to make decisions about the safety and wisdom of continued flight by observing the data and comparing it to what we’re seeing and feeling. You could adopt a stance to land at the closest airport whenever any stream of data looks suspicious. You’ll log more landings, but are you safer than the pilot who can diagnose suspicious data, look for corroboration or refutation in other data, and distinguish reliable signal from noise? Our hope is that these Puzzlers can help you […]

NTSB concluded that Eastern flight 401 crashed into the Everglades in 1972 because all three crew members were fixated on a failed landing light. The lemonade was aviation’s adoption of CRM. As valuable as trustworthy engine data can be for the success of a flight and the goal of engine longevity, bogus data can create an uneasy feeling, and could cause a pilot to fixate, or do something unwise or unsafe or unnecessary. I thought I would devote this Puzzler to unusual patterns in the data, with the hope that reviewing these without a handful of airplane hurtling through the sky will make it easier to diagnose scenarios like this and make good decisions in the air. First up is data from a Cirrus SR22 with a Continental IO-550-N using an Avidyne with a 6 sec sample rate. Fuel flow is displayed along with EGTs. From my point of view, data like this is worse than having no data at all. Let’s start on the top with EGT 5 – the green trace. Its first reading is high, about 600º higher than the others according to the Y-axis scale on the left. Then it becomes jumpy and erratic for the […]

Assume – yep, we all know what those letters stand for. I can’t speak for “u” but assuming has made an ass out of “me” more than once. There’s a fair amount of assuming attached to any endeavor, including engine data analysis. When the data looks good for all parameters, we assume that all sensors are working properly. Call it confirmation bias, but if all the specs look good, we’re not going to wonder if that’s because the failing sensors are masking a really serious issue and sending us data that throws us off the trail. If data looks good, I think we can safely assume that the engine’s in good shape and the sensors aren’t lying. When we see something that’s out of whack, it gets more complicated. I thought I would tackle a few of those in this months Puzzler. First up is data from a Cirrus SR22 with a Continental IO-550 and the Tornado Alley turbo mod, recorded by an Avidyne with a 6 sec sample rate. What’s causing EGT 3 to be low while CHT 3 is highest, sometimes by a little and sometimes more than that? Is there a clue in EGT 3 being low all […]

There’s a running gag in my family when a mechanical device isn’t performing properly. It takes three people. After the owner of the device has described the symptoms in detail to the other two people, they offer suggestions about what’s causing the problem. Once all those suggestions have been met with “yeah, we tried that” or some variant, the suggesters make eye contact, nod knowingly and together they say “Flux Capacitor.” In other words, we’re out of ideas. I hope your family has funnier gags. We’ll start this month with data from a Piper Turbo Saratoga with a Lycoming TIO-540 engine and a JPI 830 monitor with a 2 sec sample rate. EGT and Oil Pressure are on top – CHTs and MAP on bottom.  EGT 1 is the red trace on top and it’s clearly not performing well. MAP is the darker red trace on the bottom, but you can see that the other red trace – CHT 1 – corroborates reduced power output in cyl 1. CHT 6 – the blue trace – is a spark plug gasket probe, in case you were wondering why it’s so much lower than the others. So what’s causing this? Let’s look at the […]

I have written about this before, but not in two years, and with lots of new clients and a couple of new Savvy services in that time, it seemed like a good time for a biennial review. 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, degrees before 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 from SavvyAnalysis. When To Upload Flight Data Let me remind you that all flight data uploaded by Savvy Mx, Savvy QA and SavvyAnalysis Pro clients is scanned for the EGT signature of a failing valve. That happens without you having to ask. If the algorithm is triggered, we visually inspect the data and if we’re confident that the data is not bogus we will notify you. That’s true whether you’re an […]

One of the first steps of engine data analysis is evaluating the reliability of the data. In recent Puzzlers we’ve seen probes that didn’t fail spectacularly, they just kept sending data that was almost believable, and could – if you saw it in real-time, cause you to adjust your flight plan, or – if you saw it depicted later, cause you to question whether maintenance was needed. It’s a good mental challenge when we get one of those tricky sensors that appears to be telling little white lies, and we have to investigate other data for corroboration or contradiction. Just the same, we’re happy to see data where the sensor is trying to get us to believe a whopper we just can’t buy. Let’s start this month with data from a Cirrus SR22 with a Tornado Alley IO-550-TN and data from a Garmin Perspective with a 1 sec sample rate. EGTs are a little wobbly after engine start and through the taxi – that’s not unusual with a turbo. EGT 1 – the red trace – makes its first excursion to the downside just before power is applied and EGTs smooth out. Then it looks ok in the climb until […]

Flying is full of great and memorable sounds. I’ll never forget how quiet the cockpit was after lifting off for my first solo – compared to hours of hearing my CFI issue verbal corrections or way-to-gos. It was just the engine and the air. I can still remember the first time Rare Bear flew by at Reno with that giant P3 prop spinning at relatively low RPM – not only did you hear it, you could feel it in your solar plexus. And I still get a rush when I can hear three distinct wheel squeaks during landing – wish it happened more often. My airplane was built in 1974. Five years before that, Led Zeppelin released their second album, with Whole Lotta Love. It took a lot of guts for the first song on the first side to play for a while, then grind to a halt, throw tons of slap-echo on the vocal – hit two big chords and a drum fill, and jump back in for a big finish. It’s on several playlists of mine, and when I see engine data that looks like CHTs are hot because of baffles and seals – as opposed to running lean – […]

If there were a TV show where I could watch A&Ps, or just plain owners, swinging wrenches on airplanes, I’d probably watch. I’d at least give it a look. Ice Pilots and Flying Wild Alaska and Airplane Repo tend more toward the challenges of aviating and making a living than the challenge of torquing a nut you can’t reach, but once in a while you get a glimpse of the maintenance angle. So it was a joy when one day my channel surfing landed me on Wheeler Dealers, and I watched a wild-haired guy dismantle and rebuild a car. I have watched so many go in and out of their shop that I don’t remember what the first one was. I would usually watch until the end of the show when they sold the car and counted the money, but for me the fun was watching the action on the shop floor – what can he save? are there new parts available? is he really going to fab that? Having owned a Jensen-Healey in the ’70s, I already knew that there were proper British terms for hood and trunk – and we JH owners had our own colorful words for their quirky gearboxes and electrical systems […]

How can rational numbers be so irrational? Actually, upon examination what we discover is that there’s usually a perfectly logical explanation for why an engine parameter is displaying its pattern. Even the impossible jumps from a failing probe have a logical explanation behind them. Of course, that’s easy to say from the quiet comfort of an FBO, or your sofa at home – it’s another thing when you’re looking at the data in real time with a handful of airplane. Hopefully working through these Puzzlers can help you separate real anomalies from – let’s call it “fake news.” Let’s put our brains to work on some of this month’s puzzling data. First up is data from a Cirrus SR-22 with a normally aspirated Continental IO-550-N. Data is from an Avidyne with a 6 sec sample rate. All EGTs were logged, but I isolated EGT 3 so it would be easier to track along with CHT 3. Let’s stipulate that EGT 3 tracks normally with other EGTs and is right in the middle of the pack throughout the flight. The higher numbers for CHT 3 happen not long after engine start, and its heat profile is different from its neighbors – about 50º hotter […]

Someone sent me a link this week for a video of a controlled blast triggering an avalanche. That started me thinking about some of my favorite cinematic explosions: Denzel Washington blowing up an oil tanker in “The Equalizer”, Jeremy Renner’s adrenaline-addicted EOD character inside the kill zone in “The Hurt Locker”, pretty much any Bruce Willis, Stallone, Schwarzenegger or Michael Bay movie, Roy Scheider solving the shark problem in “Jaws”, the gas station in “The Birds”, the “Bridge Over the River Kwai”. “Skyfall” and Slim Pickens riding a missle into oblivion in “Dr. Strangelove.” Explosions are good IF they happen when and where we want them. And then there’s detonation. Normal Combustion It’s not fair to characterize the normal 4-cycle combustion event in our Continental and Lycoming engines as an explosion. Air and fuel arrive in the cylinder and wait until the spark plugs fire, typically 20-24º before top dead center. The fuel burns away from the spark until it’s gone; it takes about 6 milliseconds. At 2400 RPMs the crank is turning 40 times a second, so the next event is coming right up. While there’s fire in the hole, the piston is moving, and peak cylinder pressure occurs at about 15-20º after top dead […]

As we enter our 5th year of Savvy Analysis Pro, we have – as the guy on TV says – seen a thing or two in terms of the Savvy Test Profile. We decided it was time for an update, and I thought this month’s Puzzler would be an ideal time and place to review the changes. What didn’t change is the test is still a series of mixture sweeps and a lean-of-peak mag check. Let’s take them one at a time. Mixture Sweeps – aka GAMI sweeps The GAMI lean test is designed to measure mixture distribution, and is used to help diagnose incorrect fuel nozzle sizing, and dirty or clogged fuel nozzles. We compare the difference in fuel flow between where the leanest-running cylinder reaches peak EGT and where the richest-running cylinder reaches peak EGT. That difference (measured in gallons-per-hour) is called the “GAMI spread.” In our experience, the GAMI spread must be under 1 GPH for the engine to operate smoothly when lean-of-peak (LOP). For fuel-injected engines, the goal should be to reduce the GAMI spread to 0.5 GPH or less for optimum LOP operation. Begin the GAMI lean test procedure by setting up the airplane in normal cruise […]

Corroboration – evidence that supports a proposition that already has some supporting evidence – is an important component of engine data analysis. Corroboration can come from other data, or from the pilot who submits the analysis request. In analyzing the data, it helps us to have comments like “I thought the engine would shake itself right off the mounts” or “I heard a popping sound on the R mag but not on the L” or “Just after setting cruise power I noticed a surge in RPMs that lasted for about a minute, then never happened again” or “It was just as smooth on one mag as on both.” It also helps if you notice and report that a legacy gauge – CHT, fuel flow, manifold pressure, whatever it is – corroborates or disputes the data from the digital engine monitor. When probes go rogue and give us wacky readings, it helps to know that the steam-powered gauge didn’t flinch and showed a normal reading consistent with normal engine performance. Let’s look at some examples of recent data submitted for analysis. Here’s data from a Cirrus SR22 with a Continental IO-550-N and GAMIjectors. This is the one that arrived with the “right off the mounts” comment. […]