BIG Differences Flying a Turboprop vs. Piston Aircraft

for each phase of flight here's how flying a turbo prop compares to Flying a piston aircraft I'm Charlie and I recently got checked out in the Kodiak 100 which is a 10 seat 750 horsepower turbine powered Bush aircraft it is an absolute blast the first thing you'll notice in the cockpit is that there are new levers to get used to and there are also some new engine instruments to become aware of and familiar with so we'll cover each of those and then I'll cover each phase of flight to explain practically what's different versus a piston first you'll notice that the throttle quadrant looks a little different than in your piston aircraft you have the fuel condition lever on the right the prop throttle and then the emergency power lever or EPL the two on the outside the fuel condition lever and the eepl those are new so let's look at those first the fuel condition lever is kind of like the mixture in a piston where it's controlling your fuel cut off but the big difference is you aren't going to be leaning it mid-flight like you would be in a piston you're mainly using it for cut off low idle and then high idle which I'll explain here in a minute it's kind of like setting the minimum amount of fuel the engine is getting now Engineers are probably going to hate this analogy but it's been memorable for me so stick with me I kind of think about the fuel condition lever sort of like a lawn mower or a leaf blower if you've ever noticed sometimes they have a little lever on there that has a turtle on one end and a rabbit on the other slow and fast and as you adjust that lever it's kind of adjusting the minimum throttle or the minimum idle speed of that engine and so as you release the throttle it's only going to go down to the minimum that you have set on that lever the fuel condition lever is kind of similar so when you're taxing around in low idle and then a lot of times checklist will call for when you're going onto the runway to move it into high idle you'll notice the engine spool up and so that's kind of the new minimum threshold because you've adjusted the fuel condition lever so that's kind of how I think about it then you also have a new lever called the eppl or emergency power lever your primary throttle lever uses kind of a hybrid mechanical and pneumatic system like air system to regulate the amount of fuel that goes to the engine and controls the power um now if that pneumatic system fails the engine will roll back back to idle or something near idle it's called a roll back and you can use the EPL instead to manually adjust the throttle because your normal Power lever doesn't work in that instance but the eepl is way more sensitive than your normal Power lever now mostly this lever just sits here though and it's only used in an emergency but I did want to explain it so now remaining are the throttle lever and your prop control now these will be familiar controls if you've ever flown a constant speed propeller airplane before like a Cessna 182 or something like like that however there are some new gauges to reference for these controls such as torque ITT NP and NG so let's cover each of these instruments so in a fixed pitch propeller you just have a tachometer showing you RPMs and then in a constant speed propeller aircraft you have manifold pressure and a tachometer well in the turbine there's a little bit more you still have a gauge showing you propeller RPMs but it's now instead labeled NP and manifold pressure is more or l BL replaced with torque and it but then you also have percent NG in there so what the heck do all of those mean well luckily they aren't as complicated as they sound let's walk through each of them starting with torque so torque is measured and displayed in foot pounds which is kind of a weird concept but if you imagine a 1ot long lever and you put one pound of pressure on the end of that lever the resulting twisting motion is one foot pound of torque now if you applied 2 lb of pressure on the end of that 1T lever that would be 2T lbs of torque 1 * too now if you made the lever 2T long instead of 1T long and you applied that same 2 lb of pressure you now have four foot lbs of torque it's basically just a combined measure of force and leverage so as you're adjusting the power lever one of the things that's going to move on your engine instruments is torque torque is kind of your primary power selection tool now you can use this for power settings similar to how you would manifold pressure on an approach for example when you're in the pattern 600 lb of torque for the Kodiak will keep you nice in level going in the pattern and then as you're descending 4 50 lbs or so usually puts you right on the Glide path and so you can you can use it to Peg your power settings you also want to make sure you don't over torque the engine which we'll talk about here in a minute but that's torque next is ITT which is inner turbine temperature it's basically the combustion gas temperature of the engine or how hot is the engine running it's not really your primary power indication but it's something you're referencing for power settings to make sure you don't over temp the engine in general down low you'll usually hit your torque limitation before you hit your temperature Li limitation but up high the opposite is true you'll usually reach your temperature limitation before a torque limitation and so this would be called you know temping out before you torque out or I'm temperature limited or I'm torque limited next is NP which gives you propeller RPMs if you flown a constant speed propeller before you'll be familiar with this concept basically once you give it enough throttle the propeller Governor will kick in and it'll end up capping or limiting the propeller RPMs just by controlling the angle of the propeller blade it's pretty cool so at that point you can instead control RPMs with the prop control lever now this might sound more confusing than it is I promise once you get used to it it's really really intuitive now I did an entire video just dedicated to Flying a constant speed propeller so if it's a New Concept for you or you need a refresher I'll put a link to that video down in the description and finally NG is your gas generator speed which references the rotation speed of the compressor section of the engine now this one's a little bit different than the other three engine instruments we just covered because this one isn't actually a fixed number it's actually displayed as a percentage and it's a percentage of the design maximum so for example in the Kodiak 100% NG represents 37,500 RPMs it's spinning really really fast so if they were to show this gauge as 36,000 RPMs out of 37,500 RPMs one that's a lot of numbers to show on there and two that would be kind of tough Computing for the pilot so instead it just shows it as a percentage so percent NG now you don't really use percentage NG to Peg power settings like you might with torque like I was discussing earlier on an approach however where NG becomes really really important is when you lose engine power so if all of a sudden you lose engine power that becomes your first scan looking at NG because if it stabilizes around some sort of idle that just tells you you had a roll back so you have a problem with your throttle like I talked about earlier that's where the EPL emergency power lever comes in but if it continues to go down and down and down to zero you know you lost the engine entirely so that's where it's a really helpful indication the other time you end up using it is on engine startup where once it's hit a minimum threshold that's when you can add fuel in the starting process and then once it's achieved a certain limit uh that's when you can actually disengage the starter which I'll cover here in just a second now if all of that sounds really overwhelming I promise it gets easier after just a few flights you'll definitely get the hang of it and practically speaking there's not a whole lot going on you're mainly just using torque as your primary power indication also mining it to not overtemp the engine and then your prop you're really only moving it as I'll discuss here in a second after takeoff and then right before landing and other than that it's honestly pretty simple so you'll get used to it don't be intimidated now that we've got a lay of the land that brings us to the engine start which is a lot different than in a piston in a piston you're priming it and starting it and waiting for the engine to turn over and Roar to life and sometimes it can be a little temperamental as you probably know where you're trying to find the right balance of fuel to give it and it might take several tries to get it just right but in a turbine it's different because there isn't an engine turnover moment but instead it's actually happening gradually and slowly coming to life and as a result it's actually a lot easier an instructor described it to me this way in a piston there's a lot to do but not a lot to watch or monitor but in a turbo prop there's not a lot to do but there is a lot to watch and monitor so let me explain so in a turbine at least in the Kodiak you turn on the auxiliary fuel pump and the igniters which kind of sound like the igniters of a gas stove or gas grill they're going click click click and then next you engage the starter and it's going to start spinning up the engine and slowly turning the prop at that point you're watching NG start to climb because that compressor section is spooling up and once you've achieved 14% NG there's enough air flowing through the engine that igniting fuel isn't going to overtemp it but if you add fuel before this point you could end up with a hot start which could really damage the engine so once you're at or above 14% NG you then take the fuel condition lever which is kind of like the mixture in a piston and you set it to low idle and then if you listen for it there's a really cool sound in the engine where you can hear it starting to introduce and ignite fuel it's kind of a pu sound and now that fuel has been introduced you keep the starter engaged because the engine is still spooling up this point it will be climbing because you've ignited the engine and fuel is being burned but the engine is still spooling up and it's giving it progressively more cooling air so you'll want to monitor it to make sure that you don't have a hot start where it's exceeding temperature limitations and then you're also continuing to monitor percent NG like you were at the beginning of the start to ensure that it's continuing to start up and spool up now if it doesn't and it stalls at a certain number you then have a hung start where the engine isn't fully starting now in either case a hot start or a start you'd cut the fuel and abort the starting process but assuming everything is looking healthy and normal in the Kodiak once you get to 52% NG you can disengage the starter and the engine is now running on its own so there's not a lot to do really but there is a lot to watch the great thing is that it is really simple and it's way less temperamental than starting a piston and nothing sounds cooler than that turbine engine slowly spooling up and the props starting to turn faster and faster and fuel getting into introduced and you can just hear this Beast coming to life H it's just [Music] awesome but in case that sounded like a lot I promise that it's far easier than it sounds so I want to show a clip from real life startup sequence here without my commentary so hopefully you can see there's actually not a whole lot to it okay ready if you are [Music] taxiing isn't much different except for the fact that you have forward du beta and reverse thrust beta is basically just in between forward and reverse where the propeller blade angle is effectively not generating any forward or reverse thrust and so you can kind of use it instead of Light breaking now makes a very noticeable sound when you're taxi around I don't I don't know why I just can't get enough of that I think it's awesome so if you hear a turbine taxing around and all of a sudden it goes from the that's beta one of the great things about flying a turboprop is that once the engine is started there are way less checks to do than in a piston there's no magnetos to check no carb heat that sort of thing so there's not really much of a runup there are obviously some pre-take-off checks and stuff but it's way more efficient and that's partly because once the engine is running as long as it has fuel it's probably going to keep running it's kind of like a gas grill or a gas stove where you need help lighting it but once it's lit you can kind of turn the igniter off and just keep giving it Fuel and it'll stay lit now it can flame out in heavy rain or ice and stuff in which case you might you might want to fly around with the igniters on so that way it can relight itself if it experiences a flame out but generally speaking it's pretty simple all of that to say your pre- takeoff checks are pretty simple and you are ready for takeoff pretty quickly after startup some control Towers might even expect or anticipate that you're going to be ready once reaching the runway and so that takes some getting used to so obviously never be rushed by a controller but that was a little bit of adjustment like my routine of flying a piston is you start up you get the weather you taxi down and you're you're just planning on let me find my little corner of the runup area so I can just take a breath and do the runup checks and all that and take as much time as I need turbo prop it's a little bit different and so that just takes a little bit getting used to and you're also burning a lot of fuel just sitting on the ground way more than you would be in a piston so you are trying to limit the amount of ramp time you have as well on takeoff everything is pretty much the same as a piston except you have to be careful not to over torque or overtemp the engine you can't just firewall the throttle like I'm used to on my 182 and just give it all it's got now I think some turbine engines might have torque limiters on it where this might not be the case now if you have experience with that please leave me a comment so I can learn from you but at least in the Kodiak it's kind of a balance between advancing the throttle quickly enough so you don't eat up a bunch of the runway but also not giving it too much throttle and over torquing or over temping it after takeoff the climb out is really easy in the Kodiak we just adjust adjust the propeller from 2200 RPMs down to 2,000 RPMs using that prop lever and then you basically just leave it there until you're on Final for landing so the rest of the way you're really only using the power lever it is really simple and once you get to cruise there's really not much to do other than selecting your power setting between torque and ITT based on the performance and the fuel burn you want just keep in mind though once you're up high you'll probably reach your it limitation before reaching a torque limitation like we discussed earlier this is where you might temp out before you torque out or say that you're temperature limited on how hard you can push the engine but that's a lot easier than it might sound you're basically just deciding how hard do I want to push the engine and then to make things even more simple there's no leaning or cow flaps or anything like that that you're used to in the Piston again you're really only touching the power lever the rest of the way until you're on Final once you're in The Descent or the approach there are two awesome parts of flying a turbo prop the first is that you don't have to worry about shock cooling the engine so you can go from Full bore to full idle and the engine doesn't care and the other thing is that you have a ton of drag at least in the Kodiak if and when you need it because once you pull the power back the prop Governor is also changing the blade angle to a really shallow bite to maintain your high RPMs and so the combined effect is both very little thrust and a ton of drag and so you can really slow down in a hurry before we get to The Landing a quick stat you might appreciate is that I've been tracking it lately and for every 1 minute of airplane Academy content or the video it it easily takes one to two hours of time to produce it between the planning the filming the editing Etc so a 15-minute video for example could easily take 30 hours to produce so if you have found this helpful or you enjoy it would you mind considering just hitting like or even subscribe to the channel that's the best way you can just give me a virtual fist bump and I really appreciate it but if you don't like the video don't do anything just keep watching Landing a turbo prop in my opinion takes a little more finesse than in a piston I've noticed you kind of have to find the right power setting where you don't have too much drag but you obviously don't have too much thrust either when you pull the engine to idle you obviously lose thrust but you're also gaining a lot of drag probably a lot more than you're used to in a piston and so if you go to idle at any point in the approach you're going to notice a ton of drag but it's kind of a fun challenge to get that power setting just right and then when you flare I personally have noticed a lot more left turning tendency in in the Kodiak than in my 182 I think it just has a lot more P Factor pulling it to the left there and so it is taking me a lot of Landings to to figure out how to anticipate that and not continually land left of center line but it's still something I'm getting used to and then once you touch down you get to do something really fun that you don't get to in a piston and that's putting the prop into either beta or even reverse and this helps you with your ground roll because you're no longer producing any forward thrust now reverse thrust is cool it sounds really cool by the book in the Kodiak it only decreases your ground roll by like 5% so it's nothing crazy and it can kick up a lot of dirt dirt and stuff that could get inhaled by the engine so for those reasons you might not use actual reverse thrust as much as you think but it sure is fun to use it um but you're definitely still using beta in every single Landing it's a no-brainer just to remove that forward thrust Vector once you land and you're taxing to the ramp and you're thinking hey how much fuel do we need one thing to get used to is that turboprop fuel is all in pounds that's kind of annoying to get used to cuz I'm just used to being gallon Centric but it's all in pounds the quick way is just to divide the pounds by roughly 6.7 and that'll get you gallons but if you don't have a phone handy with a calculator or something there is a quick shorthand that is really useful let's say you need 1,000 lb well you can drop that last digit which makes it 100 and then take half of that amount so half of 100 is 50 and then add those two together so 100 + 5050 is 150 gallons another example say you need 800 lb well you drop that last digit which gives you 80 take half of that half of 80 is 40 and add them together 80 + 40 is 120 gallons it's not perfectly accurate but it gets you pretty close I'm putting together a separate video talk about the training that I went through to get checked out in the Kodiak CU it was a blast and I wanted to be able to share it with others so once that's available it'll be here on the screen and until then I put another video on the screen that I think you might enjoy so either way I'll see you there my wife is staring at me like what are you doing trying to teach people how to start a turban

Channel: Airplane Academy

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Length: 18min 9sec (1089 seconds)

Published: Tue Mar 26 2024