Honestly I think this video should have at least 10 times more "likes" than it actually has. One of the best explanations of "principles of flight"! Congratulations for this!
Very good vid. Brings together many aspects of aerodynamics which are often not explained as well as this. Several pilot videos do not explain Coffin Corner or the all-flying tailplane as simply as this.
@boldmethod. Thank you for this. This is ridiculously awesome, entertaining, not boring, interesting and I became a smarter pilot after watching this. The way you guys present and teach is very approachable and you make it easy to understand. Hope to see you guys Live again soon. Cheers from Miami! Gienne
That was awesome! More videos like this! Please, make some stuff about Stability & Control. Many thanks to your team for making such great educational videos!
Tremendous value as always guys! Thank you! Do you think you can do show on ATC phraseology? Some tips and tricks on how to respond as short and precise as possible maybe?
In regard to older jets, its not that they were unconcerned with fuel consumption or going fast. They had low-bypass engines which have poor efficacy at low airspeeds and so to achieve reasonable takeoff performance they had to oversize the engines compared to what is needed at cruise speed. High bypass engines have a reduced ideal operating speed range. So one type gets more effective at higher cruise speed and the other is decreasing in effectiveness. This is also why they emitted a lot of soot on takeoff and initial climb, they used water injection so they could operate at higher throttle settings without melting the turbine section. The cooling of water and higher fuel flow prevented complete combustion resulting in carbon particles.(But was only on takeoff and cooler combustion reduces NOx formation, so visually bad but environmentally neutral.) The water also added somewhat to the pounds per second being accelerated through the engine which is what jet thrust is all about, mass times change in velocity.
Amazing video with incredible explanation. This concept is so difficult to understand initially but your expansive discussion made it so much easier. This future pilot thanks you!!
Have you guys done the video on pressure waves yet? I’d be super curious to see that. By the way your explanation about the shockwave over the middle of the wing (at 19:15) doesn’t quite line up with the explanation provided by the call video made for naval aviator’s. In your video you seem to indicate that that shockwave is caused by the pressure changing from high to low but then you say that’s caused by the airspeed drop due to the shockwave..,so that’s like saying the egg caused the chicken but the chicken caused the egg. They both can’t cause each other. That’s super unclear. However, Navy video describes it perfectly and more importantly , it’s lucid and logical. It says that the shockwave above the wing builds up because of pressure waves radiating frontwards (toward leading edge) from the trailing edge of the wing…but they get backed up and can’t move forward any longer. That makes a lot more sense than your explanation. Perhaps that’s what you meant when you said “the pressure waves can’t keep up with the speed of the airfoil”? Well if so, then it seems like that shouldn’t be quickly glossed over. Understanding how the pressure waves back up, where they originate from, what causes them to backup and why, etc…all seems pretty important to having a correlational understanding of this topic. Anyway, just fyi in case that’s helpful/constructive feedback. Love your videos more than any other channel. Otherwise I wouldn’t take the time to comment. Look at this video at the 2:50 mark: ruclips.net/video/ugPJYJ-BKkU/видео.html. This explanation Is a lot more intuitive AND DIFFERENT than your explanation.
Great videoes, @boldmethod. I really enjoy following your videos and your great explanations. An idea to what a new subject could be is "aerodynamic center" .. No one seems to be able to explain that and it is almost impossible to figure out what the actual difference between that and center of pressure is and how to define and explain that term. Thank you again!
To answer the question about pressure past the shock wave changing instantly: it just does. IE, that is the nature of subsonic and supersonic flows. The shockwave isn't a causal force, it is a result. Shockwaves are phenomena that form at the boundary between subsonic and sonic or supersonic airflow. I find it not helpful to think of them as a "build up of pressure waves". They are simply the thing that forms at the boundary, whether the flow is increasing in velocity, or decreasing. We are "seeing" the change in air mass properties between supersonic and subsonic flow. Air in supersonic flow is compressible, air in subsonic flow is mostly not. The change is almost instantaneous, and a shockwave is what we call that 'instantaneous' change. Talking about oblique shocks and normal shocks (They are called normal because they form at right angles, or a normal angle, to the surface they are attached to.) is sorta misleading. They form for different reasons. Oblique shocks off the nose, for example, form because the air is 'moved' by the nose. But since it's moved at supersonic speed, the air behind it can't get out of the way fast enough, and a shockwave forms between the subsonic air before it, and the air that is moving out of the way of the nose at supersonic speed. In this type of oblique shock, the air is being compressed, and energy is imparted to it by the aircraft. Normal shocks are completely different. There is a pocket of air moving around the wing at supersonic speed. At some point, whether thats behind the wing, at the wing trailing edge, or some other place on the wing, the supersonic portion of flow must slow back down to subsonic. At the barrier of supersonic to subsonic flow, a shockwave will form. If you compare the characteristics of the air masses on either side of the shock, you will see that the air behind the shock is slower, less dense, and higher pressure, than in front, but overall has significantly less energy, because those changes happened "in" the shockwave, and required energy. The usual result is flow separation as the air doesn't have the energy to create enough pressure, at the required density and velocity, to overcome the pressure gradient on the wing. There's a lot more complexity, but when I shifted my mindset about shockwaves as phenomena instead of causal agents, it clicked.
Quick calculation of the Speed of sound in m/s = 20 x (SQRT(Temp in Kelvin). To get Kelvin add 273,3 to Deg in Celcius. Consequently a is 294,8 m/s at the tropopause, above it stays almost constant until about 20km afterwards the temp rises due to the ozon which absorbes energy from UV radiation of the sunlight.
There was an episode of The Flash where he ran around a track. When he reached the speed of sound they had this loud boom and said, "he just went faster than sound". But if he was running on a track the booms would be hitting them A LOT. That was kind of funny, I wonder how many science folks picked up on that.
you said when rolling to the left shock wave can form on left wing isn't the right wing (upper ) move faster in the air ? or as you said lift production also increases speed of air on the upper wing so why shock wave forms on the left or inner wing ?
I was wondering how mock and stuffy that actually worked thank you it's very useful could you make one on how aircraft can actually like a jet or something that can actually collide down to land like how landing actually works like it makes sense like you know coming down slowing down it's falling but how I don't get why pilots would have to speed up when they're landing when maybe one slow down.
In last video, I saw swept wing may stall starting from wing tip due to spanwise . In this video, Boeing 737 seems like have shock wave and flow separation from wing root. I am confused. Can you clarify for me. Thank you very much.
Just out of curiosity and this is from memory so I can be wrong, on the A320 for certification purposes, they had to fly at the service ceiling, use TOGA thrust and pitch the aircraft nose down to - 20 degrees to get some mach buffet and that was only for a limited time because soon they 'd be low enough to reach VMO instead.
Excellent explanation. Have gotten many fine points from watching Boldmethod content during my flight training. After the live presentation could we have a version without the six minute intro? Want to get right to the good stuff!
To answer the question about the pressure change at the shockwave. Think of a a line of identical planes all one minute apart and maintaining constant airspeed all flying into a narrow mountain pass that speeds up the wind, and that headwind at some point in the pass is equal or above the planes' true airspeed. As the first plane enters the incresing wind the ground speed slows, the second plane is still moving faster because it isn't in the pass yet so the linear separation between planes shrinks(the time separation is still one minute). Now at some point the first plane gets to the point where headwind equals airspeed and ground speed reaches zero, the next plane is still moving but in one minute it too will get to the zero groundspeed point as will every plane behind, thus all the planes will stack up on the same ground fix. This is what happens with a shockwave, pressure waves(sound) generated by areas near the trailing part of the wing move forward in subsonic flow,(from a wing surface frame of reference) getting closer together as the airflow speed is faster mid cord than at the trailing edge, until the pressure waves reach airflow moving at the speed of sound and then they can't move forward, stacking up into the peak pressure. I should also clarify that the sudden change in pressure is from low in the supersonic region to peak high at the front of the shock wave but then the pressure tapers from the peak toward a more normal pressure closer to the trailing edge.
Also this is why the shock wave initially forms around about the point of max lift/max thickness as this is the first point to go super sonic and then as airplane speed continues to increase the flow remains supersonic further and further back and so the shock wave moves further back. At an airplane speed mach 1.0 the zone of super sonic flow covers the whole upper surface and the shock wave will have moved all the way to the trailing edge, and a bow wave also forms. Important to note that there will still be a few areas of subsonic flow on the airplane up to about M1.1 or M1.2 so the trans sonic range is from critical mach about 0.8-0.9 to 1.2. Though minor compress-ability effects are significant from about M0.5 as far as overall aerodynamic design is concerned, this is considered subsonic as M1.0 is not exceeded locally anywhere on the aircraft and so no shock waves form.
ICE-T PCD (Pretty cool drink) (I)ndicated to calibrated - > Corrected for position (P) (C)alibrated to Equivalent -> Corrected for compressibility (C) (E)quivalent to True -> Corrected for density (temp+pressure) (D) Then GS is TAS + Wind :D
I can’t believe this video is free! Even at a flight school or college, not many people could explain this well. This is an awesome explanation!!
Honestly I think this video should have at least 10 times more "likes" than it actually has. One of the best explanations of "principles of flight"! Congratulations for this!
I fully agree with you.
Amazeballs! I am in shock and awe! Now I know why Concord has no Elevator, in the traditional sense.
Very good vid. Brings together many aspects of aerodynamics which are often not explained as well as this. Several pilot videos do not explain Coffin Corner or the all-flying tailplane as simply as this.
as an airline captain I truly give a high five to this channel every day!
THIS CHANNEL IS A TREASURE!
Your videos are exceptional! Thank you so much for such a clear explanation on these topics.
Incredibly valuable information. I really like how you present the topic and go into detail without it getting confusing, Alex. Much thanks!
@boldmethod. Thank you for this. This is ridiculously awesome, entertaining, not boring, interesting and I became a smarter pilot after watching this. The way you guys present and teach is very approachable and you make it easy to understand. Hope to see you guys Live again soon.
Cheers from Miami!
Gienne
That was awesome!
More videos like this!
Please, make some stuff about Stability & Control.
Many thanks to your team for making such great educational videos!
Tremendous value as always guys! Thank you!
Do you think you can do show on ATC phraseology? Some tips and tricks on how to respond as short and precise as possible maybe?
EXCELLENT Teacher, wow.... best I've heard on the subject.
This was amazingly informative. Boldmethod always impresses with delivery.
In regard to older jets, its not that they were unconcerned with fuel consumption or going fast. They had low-bypass engines which have poor efficacy at low airspeeds and so to achieve reasonable takeoff performance they had to oversize the engines compared to what is needed at cruise speed. High bypass engines have a reduced ideal operating speed range. So one type gets more effective at higher cruise speed and the other is decreasing in effectiveness.
This is also why they emitted a lot of soot on takeoff and initial climb, they used water injection so they could operate at higher throttle settings without melting the turbine section. The cooling of water and higher fuel flow prevented complete combustion resulting in carbon particles.(But was only on takeoff and cooler combustion reduces NOx formation, so visually bad but environmentally neutral.) The water also added somewhat to the pounds per second being accelerated through the engine which is what jet thrust is all about, mass times change in velocity.
I love this channel, excellent information!
Amazing video with incredible explanation. This concept is so difficult to understand initially but your expansive discussion made it so much easier. This future pilot thanks you!!
So well presented and well spoken. Love the videos
Thank you for making us better Pilots!!!
Have you guys done the video on pressure waves yet? I’d be super curious to see that. By the way your explanation about the shockwave over the middle of the wing (at 19:15) doesn’t quite line up with the explanation provided by the call video made for naval aviator’s. In your video you seem to indicate that that shockwave is caused by the pressure changing from high to low but then you say that’s caused by the airspeed drop due to the shockwave..,so that’s like saying the egg caused the chicken but the chicken caused the egg. They both can’t cause each other. That’s super unclear. However, Navy video describes it perfectly and more importantly , it’s lucid and logical. It says that the shockwave above the wing builds up because of pressure waves radiating frontwards (toward leading edge) from the trailing edge of the wing…but they get backed up and can’t move forward any longer. That makes a lot more sense than your explanation. Perhaps that’s what you meant when you said “the pressure waves can’t keep up with the speed of the airfoil”? Well if so, then it seems like that shouldn’t be quickly glossed over. Understanding how the pressure waves back up, where they originate from, what causes them to backup and why, etc…all seems pretty important to having a correlational understanding of this topic. Anyway, just fyi in case that’s helpful/constructive feedback. Love your videos more than any other channel. Otherwise I wouldn’t take the time to comment. Look at this video at the 2:50 mark: ruclips.net/video/ugPJYJ-BKkU/видео.html. This explanation Is a lot more intuitive AND DIFFERENT than your explanation.
Excellent info for FAA ATPCTP trainees.
Very good content. Thank you so much.
Great videoes, @boldmethod. I really enjoy following your videos and your great explanations.
An idea to what a new subject could be is "aerodynamic center" .. No one seems to be able to explain that and it is almost impossible to figure out what the actual difference between that and center of pressure is and how to define and explain that term. Thank you again!
Hello this was a great video, very informative and educational. Would love it if you guys could do a comprehensive video addressing ADS-B.
Great video and recent content!! keep up the good work!
Sound carries a lot further on a super cold day when the air is still, perhaps because the sound itself is traveling more efficiently.
To answer the question about pressure past the shock wave changing instantly: it just does. IE, that is the nature of subsonic and supersonic flows. The shockwave isn't a causal force, it is a result. Shockwaves are phenomena that form at the boundary between subsonic and sonic or supersonic airflow. I find it not helpful to think of them as a "build up of pressure waves". They are simply the thing that forms at the boundary, whether the flow is increasing in velocity, or decreasing. We are "seeing" the change in air mass properties between supersonic and subsonic flow. Air in supersonic flow is compressible, air in subsonic flow is mostly not. The change is almost instantaneous, and a shockwave is what we call that 'instantaneous' change.
Talking about oblique shocks and normal shocks (They are called normal because they form at right angles, or a normal angle, to the surface they are attached to.) is sorta misleading. They form for different reasons. Oblique shocks off the nose, for example, form because the air is 'moved' by the nose. But since it's moved at supersonic speed, the air behind it can't get out of the way fast enough, and a shockwave forms between the subsonic air before it, and the air that is moving out of the way of the nose at supersonic speed. In this type of oblique shock, the air is being compressed, and energy is imparted to it by the aircraft. Normal shocks are completely different. There is a pocket of air moving around the wing at supersonic speed. At some point, whether thats behind the wing, at the wing trailing edge, or some other place on the wing, the supersonic portion of flow must slow back down to subsonic. At the barrier of supersonic to subsonic flow, a shockwave will form. If you compare the characteristics of the air masses on either side of the shock, you will see that the air behind the shock is slower, less dense, and higher pressure, than in front, but overall has significantly less energy, because those changes happened "in" the shockwave, and required energy. The usual result is flow separation as the air doesn't have the energy to create enough pressure, at the required density and velocity, to overcome the pressure gradient on the wing. There's a lot more complexity, but when I shifted my mindset about shockwaves as phenomena instead of causal agents, it clicked.
Quick calculation of the Speed of sound in m/s = 20 x (SQRT(Temp in Kelvin). To get Kelvin add 273,3 to Deg in Celcius. Consequently a is 294,8 m/s at the tropopause, above it stays almost constant until about 20km afterwards the temp rises due to the ozon which absorbes energy from UV radiation of the sunlight.
There was an episode of The Flash where he ran around a track. When he reached the speed of sound they had this loud boom and said, "he just went faster than sound". But if he was running on a track the booms would be hitting them A LOT. That was kind of funny, I wonder how many science folks picked up on that.
Nice Job, Keep up the Good Work! Thank You for what you do
you said when rolling to the left shock wave can form on left wing
isn't the right wing (upper ) move faster in the air ? or as you said lift production also increases speed of air on the upper wing so why shock wave forms on the left or inner wing ?
Take a shot every time he says ‘essentially’ (JK, great video! Keep up the good work!)
Incredible video
I was wondering how mock and stuffy that actually worked thank you it's very useful could you make one on how aircraft can actually like a jet or something that can actually collide down to land like how landing actually works like it makes sense like you know coming down slowing down it's falling but how I don't get why pilots would have to speed up when they're landing when maybe one slow down.
Great video sir🔥🔥🔥😍keep it up..love from india👍
In last video, I saw swept wing may stall starting from wing tip due to spanwise . In this video, Boeing 737 seems like have shock wave and flow separation from wing root. I am confused. Can you clarify for me. Thank you very much.
Just out of curiosity and this is from memory so I can be wrong, on the A320 for certification purposes, they had to fly at the service ceiling, use TOGA thrust and pitch the aircraft nose down to - 20 degrees to get some mach buffet and that was only for a limited time because soon they 'd be low enough to reach VMO instead.
I'm a bit late, but it was worth to spend the time
Excellent
ah so what you're saying my piper warriors stabilator could possibly go supersonic hehe can't wait for my commercial oral.
See you in Florida.
Excellent explanation. Have gotten many fine points from watching Boldmethod content during my flight training. After the live presentation could we have a version without the six minute intro? Want to get right to the good stuff!
@45:00 that’s what was happening to P-38 Lightning’s
To answer the question about the pressure change at the shockwave. Think of a a line of identical planes all one minute apart and maintaining constant airspeed all flying into a narrow mountain pass that speeds up the wind, and that headwind at some point in the pass is equal or above the planes' true airspeed.
As the first plane enters the incresing wind the ground speed slows, the second plane is still moving faster because it isn't in the pass yet so the linear separation between planes shrinks(the time separation is still one minute). Now at some point the first plane gets to the point where headwind equals airspeed and ground speed reaches zero, the next plane is still moving but in one minute it too will get to the zero groundspeed point as will every plane behind, thus all the planes will stack up on the same ground fix. This is what happens with a shockwave, pressure waves(sound) generated by areas near the trailing part of the wing move forward in subsonic flow,(from a wing surface frame of reference) getting closer together as the airflow speed is faster mid cord than at the trailing edge, until the pressure waves reach airflow moving at the speed of sound and then they can't move forward, stacking up into the peak pressure. I should also clarify that the sudden change in pressure is from low in the supersonic region to peak high at the front of the shock wave but then the pressure tapers from the peak toward a more normal pressure closer to the trailing edge.
Also this is why the shock wave initially forms around about the point of max lift/max thickness as this is the first point to go super sonic and then as airplane speed continues to increase the flow remains supersonic further and further back and so the shock wave moves further back. At an airplane speed mach 1.0 the zone of super sonic flow covers the whole upper surface and the shock wave will have moved all the way to the trailing edge, and a bow wave also forms. Important to note that there will still be a few areas of subsonic flow on the airplane up to about M1.1 or M1.2
so the trans sonic range is from critical mach about 0.8-0.9 to 1.2.
Though minor compress-ability effects are significant from about M0.5 as far as overall aerodynamic design is concerned, this is considered subsonic as M1.0 is not exceeded locally anywhere on the aircraft and so no shock waves form.
next challenge for you explaining live: IAS -> CAS -> EAS ->TAS - >GS
ICE-T
PCD (Pretty cool drink)
(I)ndicated to calibrated - > Corrected for position (P)
(C)alibrated to Equivalent -> Corrected for compressibility (C)
(E)quivalent to True -> Corrected for density (temp+pressure) (D)
Then GS is TAS + Wind :D
I thin the Citation X is a good example of not wanting to go in to coffin corner...
So if an f-18 done a supersonic run at “sea level” at a temperature of -60c, would it be doing 654mph instead of 760ish?
I am the way and the truth.
Should be degrees kelvin, not degrees c, if a gas stops moving at that 0 degrees
Why is all your stuff free, it's insane
(Personal notes)
48:40 advantage of swept wing
John 14:6.
Hangman?..
Zzzzzzz.. ..