Everyone needs a reminder once in a while

It's easy for us to get used to our jobs and lose sight of how excited people can get about what we do. Sometimes we can just lose sight of how freaking cool our jobs are when we're stuck in a rut. Take for example, a recent 747 flight where we were stuck on the ground for a few hours.

We spent a total of four hours on the ground, more or less stuck on the airplane. A couple hours into the wait, while we were all ready to gouge our eyeballs out just so there was something to do, we invited some airport ops guys who were hanging around to come up and take a look at the airplane.

We ended up hosting about a dozen people, even an 8 year kid. They got to walk around the airplane, roam around the empty main cargo deck, and even hang out on the flight deck. We showed them all the information that's shown on the glass-cockpit displays. We showed them how the systems synoptics changed as pumps and air conditioning units were turned off and on. We answered all sorts of questions about how the airplane worked. Everyone had a blast.

The best part about it was that it was a great reminder of how cool our job can be, even when it starts to feel like a total drag. It was great to see people's faces light up when they walked past that mystical barrier, the flight deck door. Their first look at the displays and the view out the window caused nearly the same reaction from everyone, "Wow"! Thanks for the reminder.

Master Caution

Taking a little break from the seaplane adventure. On my last 737 flight, we were climbing through about 16,000 feet on the way up to FL410. It was a cloudy and cold day on the ground, about 3 degrees C at the surface, with a broken cloud layer from 4,000 to 8,000, and clear above. During the preflight walkaround inspection, we found a little bit of frost on the top portions of the engine nacelles that were still in the shade. The portions of the airplane in the intermittent sun, including the wing, were all clear, so we chose not to de-ice. Everything else on this glistening, low-time Boeing jet looked perfect. It was my leg so I made the takeoff, and as we climbed through 16,000 feet, the master caution lights suddenly illuminated, along with the ANTI-ICE light on my side.

Before continuing, a little background on alerting systems: The 737 was designed in the 1960s. As such, its alerting system is nowhere near as sophisticated as today's modern airliners with centralized displays that display text messages indicating system failures. Boeing calls this system EICAS, or Engine Indication and Crew Alerting System. Airbus calls this ECAM, Electronic Aircraft Centralized Monitoring. With these systems, when something fails, a master caution/warning light illuminates in front of each of the pilots, and a text message (EICAS message or ECAM message) describing the failure is shown on one of the forward displays. They simplify the alerting because they provide a single place to look to determine what systems are degraded or failed on the airplane. They also provide clear guidance to the pilots about which checklist is appropriate. The crew only has to look up the EICAS message in their Quick Reference Handbook (QRH) to find the correct checklist.

The 737 however, has a system that has been jokingly referred to as "distributed EICAS". This is because lights that describe the failures are scattered all around the flight deck, mostly on the overhead panel. It still uses the master caution lights on the glareshield in front of each of the pilots to alert them to a problem, but instead of a single display that shows EICAS messages, there are two rectangular annunciator panels, one in front of each pilot, informally referred to as "six-packs", that list general systems. There are six lights on each of the six-packs, one for each of the twelve systems. The six-pack on the Captain's side shows: Flight Controls, IRS, Fuel, Electrical, APU, Overheat/Detector. The six-pack on the First Officer's side shows: Anti-Ice, Hydraulic, Doors, Engine, Overhead, Air Conditioning. The intent of the six-packs is to direct the pilots' attention to the appropriate system on the overhead panel.

So when a hydraulic pump fails, for example, the pilots likely will not notice the hydraulic pump low pressure light illuminated on the overhead. So the Master Caution lights illuminate in front of each of the pilots, and the First Officer will see the Hydraulic light on the six-pack illuminated in front of him. This directs the crew to look up at the hydraulic portion of the overhead panel, where the additional lights indicate the status of the pumps. Sound complicated? It is, sort of, when compared to something like EICAS. If this were an airplane with EICAS (or the Airbus equivalent ECAM), like a 747-400, the crew would have seen the Master Caution lights and an EICAS message on a display that said something like HYD PRESS ENG 1. This is a 747-400 message that tells the crew that the engine #1 hydraulic pump has failed. Very straightforward and simple. There's really no need to even look at the overhead panel to confirm the failure.

When we got the Master Caution lights and the Anti-Ice six-pack light, a quick glance up at the overhead showed the L ALPHA VANE amber light illuminated. This indicated the heat to the left angle of attack sensor had failed. It wasn't going to be an immediate problem since we were climbing in the clear, and would stay out of the clouds until descending through about 8,000 feet on approach. I had the QRH on my side, so I handed it to the Captain so he could read the short checklist for the failure. It just said to avoid icing conditions, otherwise we could get erroneous flight instrument indications. We found that the circuit breaker for the left alpha vane heat had popped. After some discussion amongst ourselves and with an engineer, we decided it was safe to attempt one reset on the circuit breaker. A quick push in, and it popped again immediately. So much for that idea. Feel free to insert the standard joke here about using something to hold the circuit breaker in.

We completed our flight and started getting ready for the approach. The weather was the same as on departure, and there was no real way to completely avoid icing conditions. We decided that we would press on and minimize time in the clouds by descending quickly with the speedbrake once we were in the clouds. As we entered the clouds at around 8,000ft, I called for the engine anti-ice to be turned on. Within 1 minute, we started noticing a small buildup of ice on the windshield wiper and bolt. We had been cleared all the way down to 3,000ft, and I was descending with full speedbrake as planned.

As I watched the ice slowly building up, I paid particular attention to monitoring the flight instruments, comparing mine to the Captain's, to see if there were any discrepancies between them. It was as much for the obvious reason of the safety of flight, but also to satisfy my curiosity. We don't train for a frozen alpha vane in the simulator, and although I have some technical understanding of what SHOULD happen to the flight instruments, I've never actually seen it in person. I guess a small part of me was a little disappointed when we finally broke out of the clouds at 4,000ft with no abnormal indications at all.

I'm not going to wish that that happens again though. I think I'd rather try it in the simulator next time I get a chance.

The Two Humps

I strapped in with the 4-point harness while the instructor untied the rope, let it drop into the water, and patiently held on to the wing strut to keep the airplane from drifting away as I got myself set up. As far as casting off goes, this one would be fairly easy as there were no other seaplanes docked immediately next to us. The trick is to get the cockpit set up for engine start, so that when you cast off, you can jump immediately into the cockpit and start the engine. Until the engine's running, the seaplane is simply drifting and weathervaning, out of control. I learned that first-hand in a later lesson, when we were docked between two airplanes on a day with a 5-10kt wind. Complicating matters even more is that a seaplane does not have a very tight turn radius compared to a landplane. You don't have differential wheel brakes to help, so there's a special technique to get out of a tight space on a dock. More on that later.

Once I was ready, the instructor hopped in, I started the engine, and we were gone. It was surprising that we were moving probably 5kts even at idle, into a headwind. "This is going to be an interesting run-up," I thought. I did the after start checklist, closed the door, and headed out into the open lake. This was a warm sunny day, late afternoon, and many people had already gotten off work. It seemed that anybody who owned a boat all decided to come out the same time I decided to fly.

The run-up in a seaplane is decidedly different than one in a landplane. Sure all the same stuff gets checked: mags, carb heat, flight controls, and ammeter, but the fact that there are no brakes in a seaplane makes the run-up an order of magnitude more amusing. In a landplane, taxi into the run-up area, turn generally into the wind, set the parking brake, and occasionally look around during the procedure to ensure the brakes are holding and nobody is about to taxi into you. I never appreciated the wonderful simplicity of this procedure before. In a seaplane, while checking the mags at 1700rpm, carb heat, flight controls, and ammeter with one hand, the other hand is holding the stick all the way back to minimize water spray on the prop, the head is tilting left and right so that the eyeballs can look beyond the now very high nose, and the feet are responding to steer away from anything the eyeballs see. Oh, and don't forget to make sure the mag drop is within limits and smooth, but don't hit that jetski that just appeared out of nowhere!

With the run-up complete, two notches of flaps set, intentions announced over the radio, it was time for takeoff. Certainly the great thing about a seaplane is that without a clearly defined runway, it's up to the pilot to choose the preferred direction for takeoff, within reason. There are often restrictions due to noise abatement, boat traffic, terrain, and areas of rough water, but the float pilot still has more flexibility in taking off into the wind than a landplane pilot. For this takeoff, I had roughly 20-30 degrees of freedom. I pointed us more or less into the wind and raised the water rudders. This is a key point in the takeoff because once the water rudders are up, directional control is severely limited until takeoff power is applied so that the air rudder has sufficient control authority. Although the water rudders can always be quickly lowered again if you get into a bind, it's good practice to begin the takeoff roll as soon as possible after raising them, especially with a crosswind.

I held the control stick full aft again to raise the pitch attitude to minimize water spray on the prop, which causes significant erosion. I smoothly applied full power, and quite disconcertingly, the airplane immediately began to yaw left, even as I applied full right rudder. I was tempted to just pull the power to idle and end this madness, but my instructor assured me to keep applying power and I would quickly regain control. As I approached full power, the air rudder became effective and I was able to correct back to my original heading. Although it seemed like an eternity without any effective control authority, the airplane probably only turned about 10 degrees until I regained control, which in the middle of a fairly large lake seemed insignificant.

With full power, the Super Cub quickly accelerated to 15-20kts, and pitched up until the horizon was just visible above the glareshield, and then stabilized. This, I was told, was the first of two "humps". Following the instructions I was given in the briefing, I kept the stick full back, steering with the rudder, and waited for the airplane to accelerate more. After a few more seconds, the nose suddenly began pitching up even more until I had to lift my head up to still see the horizon, and then it stabilized again. This was the second "hump". I gently released some of the back pressure on the stick and allowed the nose to come down towards the horizon. "Lower....lower," was the guidance from the back seat. I very briefly had a flashback of a video in which I saw a amphibious floatplane land with its gear down, and violently flipped over onto its back. I wondered if pushing the nose too far down would have the same effect?

"You might have to push a bit....a little lower.....that's it....hold it right there," the instruction continued. What I saw now was similar to what I saw sitting in the airplane tied to the dock. Nearly level pitch attitude, maybe a couple degrees nose up. There was a noticeable increase in the acceleration rate as the nose came down into this "step attitude", which is the attitude that provides minimum water drag. The plane was more like a speedboat now, with the two floats barely skimming on top of the water, with very little metal actually in the water. I held the step attitude, and waited. Eventually, the ride smoothed out as the floats lifted free of the water and we climbed away.

I pitched for our climb speed, looked down and behind us at the water trailing off the float, the ropes flailing in the slipstream, and the wake we left behind. "This is going to be an adventure" I thought to myself.

"Don't take anything you don't want to end up at the bottom of the lake."

Those were the words of wisdom my seaplane instructor passed on as we walked down the dock to the Piper PA-18 Super Cub on floats for my first lesson. I put my hand in my pants pocket and cradled my iPhone, car keys, and wallet. "Fine time to be telling me" I thought, it was a long walk back to the car by now. I figured I'd take the chance this time since, as we approached the airplane, I realized there was a bigger threat of ME ending up at the bottom of the lake.

The airplane was bobbing gently in the water, right side tied loosely to the dock, with the occasional squeal of the metal float rubbing on the tires attached to the side of the dock. I stood back from the airplane a little, assessing the situation. Seaplane floats always seemed big and beefy to me, but standing there with the realization that I'd be walking along it, dodging wing struts, cables, foot steps, and doing a preflight made it look like a tightrope. I thought, if I can get through a preflight on this thing without falling in the water, it'll be a successful lesson. The right wing was hanging over the dock, high enough for me to occasionally forget that it's there, but still low enough for me to smack my head into it if I wasn't careful as it bobbed up and down in the wakes created by other floatplanes and boats passing by. I wondered how I was going to preflight the LEFT side of the airplane, but I couldn't concern myself with such details at the moment. Every plane I'd ever flown never moved when it was tied down to the ramp. This particular plane seemed like it was exempt from the laws of physics.

"The checklist is in there, go ahead and start the preflight" was the instruction. I hunched down a bit to get clear of the wing and stepped onto the float. Yowza! I could've sworn it felt like it was going to sink when I put my weight on it, now it's bobbing even more than before. I learned later that each one of the floats is required by FAR to provide 90% of the buoyancy of the max gross weight of the airplane, so there's a LOT of margin there. But that knowledge wouldn't have helped. My primitive illogical brain was trying to determine how this could possibly be safe if it reacted that much to me just stepping onto the float, and I'm by no means a big guy. I found the checklist, did all the cockpit set up items, grabbed the fuel sampler, and slid aft along the float so that I could grab the bilge pump out of the aft baggage compartment.

I stepped back onto the dock and crouched down by the aft end of the float where the water rudders are, one on each float. Seaweed, lots of it. It was caught on the rudders and the control cables and springs. "This time of year we get really bad weeds here. Make sure you clear that stuff off, otherwise it's going to jam the rudders." I pulled off every last bit of the crud and wiped my hands on my pants, wishing I had changed out of my work clothes.

Next, I had to pump out each of the watertight compartments in the float using the bilge pump, which looks like a bicycle pump, and requires more effort to work. The floats aren't perfectly watertight, and you'd expect to get some amount of water in there every day. For obvious reasons you want as little water in them as possible. I pumped each compartment until the pump spit out air, which for the most part didn't take very long, until I got to the one in the middle. I pumped, and pumped, and pumped, and pumped. Water kept coming out. I stopped to take a breath, and asked how much water was too much? "Depends how often you pump it. If you're getting that much after every 2 hr flight, that's probably too much. But I don't think that one's been pumped in a while." Good enough, I pumped a few more times and it finally emptied. I finished the rest of the compartments, and the rest of the right side of the airplane including the engine oil and fuel sampling. Nothing spectacular there. "Okay, let's turn it around so you can do the other side." This should be interesting.

There was a light breeze from the southwest, and the airplane was pointed roughly south on the dock. "Get a good grip on the elevator and just walk it along the dock, turning it. Make sure you're holding onto the frame so your hand doesn't punch through the fabric." This should be very interesting. Once the airplane was untied it got a mind of its own. Weathervaning tendency doesn't just occur when you're taxiing, or on a takeoff or landing roll. It's there all the time. And when an airplane is sitting free in water, it'll weathervane in the lightest breeze. Once it was untied, I could immediately feel it wanting to turn into the wind and drift away from the dock. I started pulling and turning but I was fighting nature, and losing. "Pull it back a little and pin the aft bulkhead of the float against one of the tires, then turn it around the float." I stopped for a second so my brain could process this instruction. I eyed the aft end of the float and how it met the tires hanging off the dock, constructing and then solving the geometry problem in my head. My high school geometry teacher would've been proud. I pulled the plane aft so the back end of the float stuck firmly on the edge of one of the tires, then I pulled the tail to the right, keeping aft pressure to keep the float pinned against the tire. The airplane pivoted fairly easily around the point where it touched the tire. Once it got going in the right direction, it was fairly easy to keep it going around, even with the breeze fighting me. Once I got it turned 90 degrees, I reluctantly let go of the right elevator, walked over to the left one, and continued turning it. For a brief moment, the plane was on its own, drifting in the water with nobody to guide it. I asked, "So, has anyone ever lost their grip on the airplane and let it drift out into the middle of the lake?" The answer: "Nope, and please don't be the first." Okay, no pressure. Once I had it swung around 180 degrees, I was shown how to tie it on a cleat, finished the preflight, and turned it back around. I had to be shown how to tie to a cleat again. I practiced it a couple times to try to drill it into my head. The only knots I know how to tie are my shoelaces and my tie, neither of which were appropriate for a seaplane. These were the first of many new skills I had to learn that bore no resemblance whatsoever to any piloting skills I'd learned in my previous 10 years of flying.

"This first time, go ahead and get strapped in, and I'll do the undocking so you can see how it's done." Okay, I thought, but how hard could that be? Famous last words...

to be continued

More coming...

Took a long break from posting, but more coming again soon. I have a good excuse though! I've been busy getting rated in the 747-400, getting a seaplane rating, doing a little 737 flying, and a whole lot of C208B flying. Lots of stories over the past year to come. Stay tuned...

The Glass Cockpit

Our Cessna Caravan is equipped with the Garmin G1000 avionics suite. It's often referred to as a "glass cockpit" because it replaces all the traditional round dial mechanical gauges with computerized information on three large format LCDs. If you clicked on the Garmin G1000 link above, you'll see the color displays that present all the information you would see on a traditional panel, and much more beyond that. Below them are four small round dial gauges used only as a backup if there were to be a complete failure of all three of the primary displays.

There's a mind-boggling amount of information presented to the pilot here. A single screen is capable of showing all six of the basic flight instruments, communication and navigation radios, navigation information, engine instruments, airplane systems information, moving map, flight plan, traffic, XM satellite weather, autopilot modes, wind vector, and alerting messages. Just ONE screen. Of course, that gets pretty busy on a single screen, so fortunately we have three.

The screen on the left is the pilot's Primary Flight Display (PFD). This is the one that collects the pilot's basic six-pack of flight instruments into one place: attitude indicator, airspeed, altitude, vertical speed, horizontal situation indicator (HSI), and the turn coordinator and ball. After putting all that on the one screen, there's still lots of space available. So along the top two corners, there's room for controlling the 2 communication radios and the 2 navigation radios. Between those two corners there are two rows of information, one that indicates the autopilot and flight director modes, and another with basic navigation information, track and distance to next waypoint. In the bottom corners, there's room for a small "inset" map on the left side (not shown) which is just a miniaturized version of the big map seen on the center display. On the right side there's room for an abbreviated version of the flight plan. The bottom of the screen has controls for the transponder, clock, and various configuration settings for that display.

The display in the middle is referred to as the Multi-Function Display (MFD). Hardware-wise, it's exactly the same as the PFD, and it can be made to show the same information as the PFD if the left screen failed. It shows all the engine, fuel, and systems information in a column along the left edge. The top edge contains information similar to what's on the top edge of the PFD, minus the autopilot information. But most of the screen is devoted to that nice big color moving map. Just about every kind of information that a pilot would want is shown on the map: Basic navigation information, topography, terrain, traffic, landmarks, roads, airspace, airports, waypoints, weather (either from your onboard weather radar or downloaded via the XM satellite weather feature), flight plan, and XM radio stations (seriously).

The PFD on the right for the copilot is essentially the same as that for the pilot.

All this information is a lot to take in, and learning how to use it all has proven to be the most time-consuming part of learning to fly the airplane. I don't have a vast amount of flying experience, but I've flown all sorts of piston singles and twins, and the Boeing 737. The Caravan flies pretty much like a single-engine Cessna. Not a big deal because aerodynamics are the fundamental principles behind how an airplane behaves in the air, and those don't change. But the way the avionics function isn't tied to any kind of fundamental principle, it's just based on what the manufacturer of the box wants to use. So you end up with vastly different interfaces and operating philosophies moving from one avionics manufacturer to another. I've been immersed in Boeing airplanes and their Flight Management Systems (FMS) and autopilots for years now, and having to learn the Garmin way has been a mild shock. It's helped that I did have a small amount of experience with Garmin several years ago, but it has still required a big paradigm shift.

We were actually given some fairly in-depth training solely for the Garmin G1000 as part of our training for the Caravan, and I'll write more about that in a later post.

175, 150, 125, 148, 27.5, 28.5, 24, 20, 11.7, 10/11/12, 1090, 765, 30/60/30/60/30/30, 20/120/20/120/20/60

Numbers numbers numbers! One of the great joys (insert sarcasm) of learning to fly a new airplane is memorizing numbers. Just about anything having to do with flying involves numbers, which need to be memorized because often times things are happening so fast that you just don't have enough time to go look them up. That old excuse "I don't know what it is, but I know where I can find it", won't work when it comes to these numbers. 

In a Cessna Caravan, a single-engine airplane, one of the most important numbers you should have in your head is the best glide airspeed. This is the speed at which, if your engine fails in-flight, you'll get the maximum glide range. Obviously, when you've been unwillingly turned into a glider due to an engine failure, you're going to want to maximize your glide range in order to maximize your options for landing sites. If you're lucky, you'll be able to find an airport within your gliding distance, or a road, an open field, golf course, etc.  So there you are fat, dumb, and happy cruising along at 15,000 feet and 150 kts over an 8,000-foot mountain range, when suddenly the high-pressure fuel pump, of which there's only one, decides to come apart. Now your heretofore ultra-reliable PT6A-114A turboprop engine has become a quarter-million dollar paperweight.

From the pilot's perspective, it won't be obvious what caused the failure. It's clear what didn't cause the failure though. Since there was no obnoxious aural warning, no sudden nasty bang,  and the engine flamed out, rather than rolling back to idle, we know that the engine's not on fire (good-although an engine on fire will typically keep running for a while), it didn't have some catastrophic mechanical failure that would preclude an attempt to restart it (maybe good), and it's not a Fuel Control Unit (FCU) malfunction (bad-because that one's easy to deal with and your engine will keep running).

Being a pilot of sound judgment, the first thing to do would be to fly the airplane. In this case, it would mean trimming the airplane (or using the autopilot) to start slowing to your best glide airspeed, 95 kts at max gross weight, decreasing by 8 kts per 1,250 lbs below max gross weight. This is important because with the airplane cruising at 150 kts with cruise power, the elevator is trimmed for that high airspeed and power setting. Once that thrust goes away, the airplane will naturally want to maintain its trimmed airspeed of 150 kts. Without thrust and without any input from the pilot, the airplane will pitch down and start a fairly rapid descent, right into that 8,000-foot mountain range. Simultaneously with trimming and slowing to 95kts, a turn would be started to get away from the mountains and start heading for the nearest airport or other suitable landing site.

This is where that 95kts becomes really important. A mountain range doesn't present a lot of options for landing an airplane. At an altitude of 15,000 feet, you're 7,000 feet above the mountains, which at the proper glide speed will allow you to glide approximately 15 nautical miles before hitting the terrain. That's a considerable distance, and it may just be enough for you to clear the mountain range completely. If you were to clear the mountain range completely, your 15,000 feet of altitude would allow you to glide 32 miles before reaching terrain at sea level. The chances are very good that you'll find a suitable landing site, or even an airport, within 32 miles of your current position. 

Okay, back to the story, things are happening fast. The instant the engine starts to lose power, the left hand is flying the airplane, slowing it to 95kts, turning away from the mountains and towards the nearest runway, and the right hand is pulling the power lever to idle, and then turning on the engine ignition. Oh wait, the ignition switch is on the left side of the panel, so let go of the flight controls to turn it on, or switch hands, grab the yoke with the right, and flip the ignition switch on with the left, then switch hands again. Push the power lever up with the right hand and see if the engine's accelerating with the ignition on. Nope. Check the engine instruments, is it still running at low idle? Or is it flamed out? If it's at low idle due to a FCU malfunction, the engine instruments should show Ng RPM of 48%, fuel flow of 80-110 pounds per hour (pph), and 500-600 degrees Interturbine Temperature (ITT). No time to look up those numbers either.

In this case the engine's not running, so it can't be a FCU malfunction, so there's no point in trying to use the Emergency Power Lever to control the engine. Time to attempt a restart, which I'll talk about in detail in another post. But for now, there's more numbers to recall. During a start, fuel should be introduced when Ng RPM reaches a minimum of 12%, and the engine instruments should show ignition within 10 seconds of introducing fuel, indicated by increasing ITT. If ignition doesn't occur after 10 seconds, the fuel must be cut off again as it's just pooling in the engine, a big hazard. After ignition, as ITT increases and the engine accelerates, the ITT must be monitored to ensure it doesn't exceed 1090 degrees C for more than 2 seconds, otherwise engine damage will occur. Finally, Ng RPM should stabilize at a minimum of 52% if the start is successful. All of this occurs in the span of several seconds, so there's no time to refer to your books.

While troubleshooting the engine, ATC needs to be informed of the situation so they can get other airplanes out of the way and possibly get search and rescue crews going, in case that airport is out of reach. Chances are that we're already in contact with them, but if not, we'd have to set an emergency code on the transponder, 7700, and change to the emergency radio frequency, 121.5 to make contact with somebody, both numbers that need to be pulled up quickly.

Getting closer to the runway, start thinking about extending the flaps. The Caravan has 3 flap settings, 10, 20, and 30 degrees. The maximum speeds for extension of each of those flap settings is 175, 150, and 125 kts. Since we're gliding at 95 kts already, those limit speeds won't be a problem. In preparation for touchdown, the speed needs to be reduced to a speed appropriate for a landing without engine power with the flaps fully extended, 80 kts. Be considerably faster than this on final, and the airplane will have to be much speed, float in the flare, and possibly overshoot your landing point. Hitting the ditch at the far end of the landing area is just as bad as hitting the ditch just before the landing area. Be much slower than this, and the airplane may hit hard as there isn't enough airspeed to get a good flare.

It takes a considerable amount of effort to cram all these numbers into your head since it's just rote memorization. Once crammed in there, they also tend to be the first things to fall out if you don't fly for a while. Which is why staying current is so important for pilots. There's so much information that needs to be crammed into your head and available on short notice, that you need to review frequently. Sure you could go flying without knowing the numbers. Happens all the time. Most of the time, you know just enough of the numbers that you need on a daily basis and that gets you by just fine. But then worst case, there may be a situation where if you don't pull them out of your head immediately, it can lead to airplane or engine damage, or getting stuck over a mountain range in a glider.

In case you're curious, here's an explanation for all those numbers in the title:

175 - Max operating speed

150 - Max speed flaps 20

125 - Max speed flaps full

148 - Maneuvering speed at 8750 lbs

27.5 - Bus volts when on the standby alternator

28.5 - Bus volts when on the main generator

24 - Minimum battery volts to start the engine on the battery

20 - Minimum battery volts to start the engine using an external power cart

11.7 - Minimum TKS fluid required for dispatch into known icing conditions

10/11/12 - Configuration for an instrument approach, 10 degrees flaps, 1100 torque, 120 kts

1090 - Maximum starting ITT

765 - Maximum climb ITT

30s/60s/30s/60s/30s/30min - Starter duty cycle limits on the battery

20s/120s/20s/120s/20s/60min - Starter duty cycle limits on the external power cart