What happens if an aircraft climbs too high?!

hi everybody welcome to mentor and yet another video podcast is always hope you're doing absolutely fantastic today on the video guys we're gonna be talking about why aircraft fly as high as they do what happens if they fly higher than they're supposed to do and what is coffin corner we're also gonna be talking about how to deal with both low-speed stall at high altitude and high speed stall at high altitude so make sure you stay tuned right guys this video is brought to you in cooperation with brilliant at org now brilliant org is a smart way for you to stay smart if you are among the 500 first ones who clicks this link below you'll get 20% off their annual fee but it's completely free to check him out and I highly recommend that you do so right guys so you would probably at one time or not the one that why the aircrafts fly as high as they do and why don't they fly higher than they do why don't they fly lower than they do and that's always there are some good reasoning for that okay so basically speaking you have to understand a little bit about aerodynamics and we're gonna talk to that about that in a second but there are three good reasons for aircraft staying as high as to do the first one and the most obvious one is economics okay the higher we fly the more economic it becomes and the quicker we fly and that has to do with the density of the air the actual amount of air molecules that fly off the wings okay while we at low altitude let's say that we're flying at 250 knots at 5,000 feet for example that means that a certain amount of air molecules are flowing over the wings and into our pitot tubes also those little tubes that are in the front of the aircraft and on the back of the fin that measures how many molecules the aircraft is actually flying into okay now as we climb higher it becomes the density of the air becomes lower and lower and lower it's less and less air basically but the aircraft still needs to fly at the same more or less the same indicated airspeed that's because the aircraft needs that amount of air to flow over the wings in order for it to be able to produce as much lift it need to keep it from stalling all right but if you are going to need get the same amount of air of the wings when there's less air available it means you need to fly faster and that is exactly what's happening so while the indicated airspeed at 5,000 feet might be 250 notes at 37 or 38 thousand feet which is where we tend to fly the indicated airspeed what we see on our airspeed indicator is still going to be about 250 knots but the true airspeed which is what the airspeed is when you count the density into it is going to be closer to 450 so almost twice as fast as the indicated airspeed and this is for the same amount of fuel all right the engines are still going at the same kind of our rpm so this this will now give you an idea of why we climb as high as we do so we'll go twice as fast the same amount of fuel and obviously that would bring you from A to B much quicker this is the reason why by flying aircraft this among if not the fastest mode of transport out there at the moment right so that's number one number two is passenger comfort so jet airliners tends to want to fly between about 35,000 feet up to about 42,000 feet that tends to be where we are the weather that you see all the weather around you tends to stay between ground level up to about 35,000 feet all the the rain clouds the turbulence all of that would be in that region so if we can climb higher than that it means that we can avoid most of the turbulence means a smoother ride for you quicker right from you from A to B right so that's what's that there will be some storm clouds and stuff that can go higher than that and also the ones that we need to avoid which I mentioned in a previous episode about flying into the storm but most of the weather will be below us there's also a third reason which a lot of people don't think about and that is safety basically the higher you are the more potential energy you have the more options you have in case something would happen so for office pilots if we're up at 37,000 feet and something happens to our engines for example or to any other system it means that we have plenty of time to deal with that problem until we're forced to land so in a worst case scenario if we would for example lose both of our engines for whatever reason volcanic ash and then the the 737 is and all of the modern aircraft or excellent lighters they will not fall like a rock down they will actually glide at a ratio of about one to well between 1 to 15 to 1 to 20 so that means for 1 meter dropped we go 15 or 17 meters forward okay so that means that if you're flying over mainland Europe like I am if you lose an engine at 37,000 feet you will have Airport within range it will give you a good 60 70 nautical miles in which you can find an airport and actually glide in and land that right so you have three very very good reasons for flying that high but if that's so good and if it's so economic to fly high why don't we fly higher than now here is where your aerodynamic knowledge comes in all right so I've already mentioned that's the true airspeed will in the will increase as the density of the air decreases all right the indicated airspeed will stay potentially more or less the same now the stall speed will be the same in relation to your indicated airspeed with altitude but it will increase with true airspeed so this means that as we're climbing higher you'll get closer and closer to your to your potential low speed all right low speed stall another thing that limits us from climbing higher and what the first thing I should mention is that the the real reason what we can't climb much higher than we do is because the engines will not have enough oxygen to breed all right the engines needs an oxygen to mix up with fuel molecules to burn to produce the thrust they need and as the density of the air keeps decreasing we'll so does the thrust of the engine so does the power of the engines so as we're up to when we're down on the ground for example they're extremely powerful but when we're up at 38,000 39,000 feet they produce just enough thrust to maintain our altitude and to give us a climb of 500 feet per minute when the engines cannot produce a climb of 550 minutes for jet aircraft that's considered our maximum operating altitude so that's one thing but the other thing is that as the air sorry as the the altitude increase so the temperature outside will drop okay so while you might be at a nice 20 degrees outside when you're boarding the aircraft on the ground when we're up to our or optimum altitude at 38,000 feet the outside temperature might be minus 50 minus 55 or even lower than that and something that also lowers when the temperature lowers is the speed of sound okay so the speed of sound will be constantly decreasing as the temperature decreases now this the true airspeed stall speed will increase as the altitude increases as you can see at one point or another those two will meet and when they meet this is what we call the coffin corner the cue corner okay this is where even if an aircraft is actually at that altitude if you go slower so if you decelerate you're getting too low speed stall if you accelerate you're going too high speed stall and the reason you into high speed stall is because an aircraft has something called a critical Mach number this is the Mach number at which the certain part of the of the aircraft go into supersonic speed so typically we will be flying at Mach numbers of 0.7 eight seven seven seven eight something that's about seven to seven percent of the speed of sound if we start to accelerate beyond that and we go over our maximum our Maki cleat and let's say that's a point mac point 81 for example what happens then is that the air that's being accelerated over the wings in order to produce a lift since the aircraft is now flying at point 81 81 percent of speed of sound that accelerated air might actually go faster than speed of sound and that would create shockwaves now those shockwaves will create an enormous amount of drag at certain part of the aircraft and they will also have the aerodynamic effect of moving the center of pressure us in where the lift is being taken out and wing backwards and those two things combined is going to give some really really nasty effects on an aircraft that's designed for subsonic and transonic flight so we are not allowed to go past the mcribs because and we can't go past the mic rate if we will go into supersonic flight with 100 aircraft Wow with one of our aircraft we might actually break the aircraft apart okay so these are some two or two very distinctive barriers that we cannot cross and when we're up there just in between that when we have only a few knots to high speed stall and only a few knots to low spin stall that is the coffin corner so what do we do then let's say that we are up there and we would for whatever reason get into a low speed situation well first of all the aircraft will warn us all right and it shouldn't if we don't go over our maximum altitude and we tend to fly at our optimum altitude that's about 600 feet below our maximum altitude that the aircraft will not need it shouldn't start to decelerate but if we that say we're not monitoring our instruments we're reading a newspaper or something and the outer total would fail at a low trusts setting well then the aircraft might start decelerating now as the aircraft start decelerating the drag increases so the slower you go the more trust you're going to need in order to pull yourselves out of it this is also very nasty part of the aerodynamics the aircraft will start warning us so it will start sending out messages on our FMC Mac sorry Buffett Alert it will start showing a blinking speed in the crater in yellow saying that we are approaching we're going past our 1.3 G limit towards low-speed stall it will start saying it verbally you'll hear speed low speed low from the from the aircraft and then eventually if we reach our barbers poles which is where our actual stall speed is calculated to be the aircraft will start shaking the control column which is called a stick shaker at that point or even before that point we can start experiencing buffett this is where the aircraft part of the aircraft starting to stall and when that does you will start feeling something like very intense turbulence right here whatever comes first to those so either the stick shaker or the buffett we need to react with a stall escape maneuver right so it's very very important that every pilot that gets trained understands what a stall looked like and how to get out of it and the way to get out of it there's only one good thing to do and that is to decrease the angle of attack all the wings okay so as the speed has been decreasing the aircraft would have pitched up in order to maintain the altitude that means that the angle between the the the air and the wing is has increased okay that needs to decrease in order for the stall to disappear so we need to get the nose down by the way the accident would air france of the atlantic i think it's at 447 this is what they did not do all right they'd never they never understood that they were in a low-speed stall and then having lowered the nose which is why they ended up tight they did okay so this is how dramatic it can be so what we do then when we get these warnings is that we disconnect any automatics that we have we make sure that the nose goes forward well actually push the nose forward we lower any speed brake that might be out shouldn't be out of this this point anyway and we we roll the aircraft wings level if it was in a turn so as the nose is coming down we have that under control we might need to use trim in order to get you know get the forces that we need to get the nose down then we gently put trust on and the reason that we're not getting the full thrust on immediately is because remember the 737 has engines mounted under the wings so if we would add thrust the wings the engines would then push forward and you'll get an upwards pitch moment and that might negate the push forward because we have so little aerodynamic control at this point this is why we can only add trust gently as the nose has already been dropped and you see the speeds coming up trust in order to get more speed and once the speed is back up on the controllable in the controllable regime generally over 200 knots 210 knots somewhere then gently gently start leveling the aircraft off and then potentially start to regain your altitude and the reason that you have to be really gentle at these altitude is because any fast movement will get you into a secondary stall because of the G loading on the wings if you pull too fast the G loading will make the air separate in the wings again and once again being stick shakily you'll see the Barba's pods come shooting up from below you and then you have to redo the same thing again so very very gently pull it backwards until it's level thrust is back up to climb trust and then climb back up again so we always exchange altitude for speed in the case of a little speed store all right this is what you are going to have to do if you instead get into a high speed stall so let's say that we come and we fly over the Alps and you go from a very warm air mass into a very cold air mass the change in density might change the air speed rapidly or you encounter turbulence or you get into a jet stream which are rapidly changing wind increases the air speed for you when the like it's the first thing that you will notice is that the clock will tell you that you're cleaning a latrine and the overspeed condition okay there is margins built in to this all right so it's not like yours you are going to go through your critical Mach number immediately but there is some small margins in there what you need to do then is we need to keep the autopilot not a totally engaged the trust should come back to to respond to this because the trust is trying to govern outside of of the Mac so the maximum speed and you race partial speed break okay if it's needed very important to make sure that the trust doesn't go all the way back to idle because if you have high altitude the air density is so low that if the aircraft sorry if the engines actually decelerate back to full idle if you want to trust to come back up again it's gonna take up to almost a minute to get to trust back again and that might be enough time for the aircraft to go from a high speed to a low speed situation so trust comes back to maybe some mid point very gently raise the speed brakes up to not full but partial speed break and the reason you have to be once again really really gentle with this is that you're in a high speed situation now if you suddenly raise the spoilers on the wings the air is going to accelerate over those spoilers and you might get shock waves over the speed the spoilers and if you get a shock wave on one side but not the other the aircraft might just roll over so very carefully brace them see that the speed is coming back into the normal controllable regime make sure the trust is up then lower the speed brake at the same rate as you put them up very gently back in okay you can in some extreme scenario override the outer total servos to just increase the speed of which the aircraft solidly the engines are or slowing down but generally that should not be needed okay so this is how you handle either a low-speed stall or a high-speed scenario okay and I hope that makes sense to you um this by the way guys as you can see now we're talking about we've started to talk a little bit more about some fairly advanced aerodynamics here we're talking about through air speed we're talking about critical Mach number things like this this is why your knowledge of mathematics and physics is gonna be so important okay I'm not just saying that it's because you need to understand this and their formulas that you need to to calculate in order to find your magic written order to find your stall speed and things like that this is why I am so happy that brilliant is the sponsor of this episode because brilliant they will teach you exactly these kind of things all right I use it myself in order to keep myself sharp and the way that I do it is I go in I go in to their website I find the course that I think is interesting for example physics of every day it's one of my favorites I find there may be something about the Coriolis effect and if you don't know what the Coriolis effect is this is then this is definitely something for you then they will tell me a little bit about it some overview information they will start to giving me some nuts to crack some problem-solving to do and I will try to solve it if I make a if I solve it then they will give me something harder if I don't solve it if I answer incorrectly well then they will give me a reason why that's wrong how to think about it how to solve the problem I'll be able to solve it and then I'll go on so you'll get increasingly better in in a fun way in a way that doesn't feel like school right so I highly recommend you to check it out the 501st of you who does this is gonna get 20% off their annual fee but it's low to start with but it's completely free to check it out if you have more questions around these guys or how we deal with certain maneuvers and things like that feel free to send them in here make sure that you have both subscribed and that you have clicked the notification belt so you know when I'm doing live stream for example had a great live stream the other day on Sunday with loads and loads of questions that were clarified so check into that every Sunday whenever I'm not working at least have an absolutely fantastic day guys and I will see [Music]

Channel: Mentour Pilot

Views: 1,162,507

Rating: 4.9085574 out of 5

Keywords: pilot, pilot life, how to become a pilot, pilot facts, aviation, aviation fact, landing, takeoff, stall, Boeing 737, Boeing 737 MAX, Boeing 787, Airbus, Airbus 320, Airbus 380, Concorde, stall escape, Aviation Youtuber, Mentour, Mentour pilot, Pilot Mentour, Fear of flying, fear of flight, Captain, First officer, flight scool, flight training, coffin corner, max ceiling, certified ceiling

Id: easH7ueBKXc

Length: 20min 7sec (1207 seconds)

Published: Fri Oct 12 2018