At angles of attack like this an airliner would stall very easily. The 787 wing would stall at an angle of 30 degrees. The plane would have been flying at speeds of around 200mph(more likely less) at this angle and speed the aircraft would be very susceptible to stalling? How is this even possible to perform this without stalling?
Source:youtube The a380 also performed this near vertical takeoff.
Source:Youtube
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4$\begingroup$ Please take a few minutes and search for your title before you crack open a duplicate question! :) $\endgroup$– egidCommented Oct 13, 2015 at 23:34
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1$\begingroup$ @ethan Don't believe everything (Edit: make that anything) you read on YouTube. Next you'll be telling us the Earth is flat. $\endgroup$– user11516Commented Oct 14, 2015 at 0:12
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$\begingroup$ @mins Yes you find many mountains topping 8,000 meters in the Himalayas mountain range. $\endgroup$– EthanCommented Oct 14, 2015 at 0:41
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1$\begingroup$ @Ethan I don't disbelieve the footage, but it's not a 'near-vertical' take-off. All the clips are shot from head-on or tail-on positions. There's no way to judge the actual angle accurately from that position. Look at the same take-off from the side and you'll find the actual climb angle is nothing like 90deg. $\endgroup$– user11516Commented Oct 14, 2015 at 0:50
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1$\begingroup$ You need to understand the difference between angle of attack and pitch angle. There is no way for you to know the AoA by looking at the photo. In essence, you would also need to know the speed and flight path. $\endgroup$– SimonCommented Oct 14, 2015 at 7:48
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2 Answers
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First of all, it was nowhere near vertical. It is basically an optical illusion created by the camera angle.
Second, and most importantly, what you are seeing is the pitch angle and not angle of attack.
As it can be readily seen from the following image, the angle of attack and pitch angle can be significantly different.
Image from What is Angle of Attack? by Boeing
Angle of attack (AOA) is the angle between the oncoming air or relative wind and a reference line (usually fuselage centerline or longitudinal axis in commercial aircraft) on the airplane or wing.
Pitch angle (attitude) is the angle between the longitudinal axis (where the airplane is pointed) and the horizon.
Flight path angle is the angle between the flight path vector (where the airplane is going) and the local atmosphere. In other words, it is the angle between the flight path vector and the horizon, as far as a commercial airliner is concerned.
When referenced to the atmosphere, the angle of attack (AOA) is the difference between pitch angle and flight path angle. Depending on the aircraft atitude, they can be very different. During climb, usually the pitch is increased at constant angle of attack.
For example, in a steep descent, an aircraft could reach very high angle of attack if the nose is below horizon. While flying upside down (not something that happens in an airliner, I might add) , both differ by around 180 $^{\circ}$.
So, the angle of attack in this takeoff is surely well below the stalling angle of 787.
answered Oct 13, 2015 at 23:17
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$\begingroup$ @mins You're right. Corrected the mistake. Actually, that is the pitch angle. The irony though. $\endgroup$ Commented Oct 13, 2015 at 23:44
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$\begingroup$ One other thing to note is that any aircraft can flu vertically - assuming it is travelling fast enough forwards, it can then pull up, it won't sustain that speed for long, trading momentum for altitude, it wouldn't be a normal takeoff, but it could look like one. This technique is used regularly at air shows $\endgroup$ Commented Oct 14, 2015 at 22:55
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The plane is likely extremely lightly loaded, and it is not flying at 30 degrees AoA. The angle the plane is making with the ground is very high, but the angle it makes with the freestream (i.e. the AoA) is probably still quite small (10-15 degrees at most, I'd expect).
