GordonD Posted September 17, 2015 Share Posted September 17, 2015 I know that the curved cross-section of an aircraft wing means that the airflow on top is moving faster than that below, resulting in a higher pressure underneath, which provides the lift so that the plane can fly. But then how can it fly upside-down? 1 Link to comment Share on other sites More sharing options...
Graham Boak Posted September 17, 2015 Share Posted September 17, 2015 Because it is not just the shape of the wing section, but the angle it makes with the airflow. This is called the angle of attack - the more nose up the more lift until the wing stalls. So an aircraft flying upside down has a rather inefficient aerofoil and so has to fly at a greater angle of attack to get the same lift. 5 Link to comment Share on other sites More sharing options...
GordonD Posted September 17, 2015 Author Share Posted September 17, 2015 I knew somebody here would know the answer. I didn't expect to get it in three minutes! Thanks, Graham. 2 Link to comment Share on other sites More sharing options...
noelh Posted September 17, 2015 Share Posted September 17, 2015 Yes indeed angle of attack I know that the curved cross-section of an aircraft wing means that the airflow on top is moving faster than that below, resulting in a higher pressure underneath, which provides the lift so that the plane can fly. But then how can it fly upside-down? Yes it's all about angle of attack. Almost any surface can produce lift if the angle of attack is sufficient. For example there are symmetrical wing cross sections, typically on aerobatic aircraft which works the same inverted, vertical or upright as long as the angle of attack to the oncoming airflow is correct. Another example of how lift can be produced is to put your hand out the window of a moving car. Hold it horizontally and it will remain steady, incline the palm slightly and it will tend to lift. Clearly it's not wise to do that while driving the car! But controversially your description of how lift is generated is incorrect! Don't feel bad because in fact exactly how lift is generated almost defies simple explanation. Despite the fact that this method of generating lift is that most often taught to new pilots. In fact this subject has generated more controversy than Luftwaffe colours or the interior colour of early Spitfires. There were many arguments between the proponents of the Bernoulli method of producing lift and Isaac Newton's theories. In reality it's a combination of both. Here's a webpage with some good examples including inverted flight. http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/airfoil.html All I know for sure is that it works. I've been flying for over 34 years and every time I look out at the wing I think. 'I have no idea how that plank like thing is keeping us in the air.'​ ​ 1 Link to comment Share on other sites More sharing options...
GordonD Posted September 17, 2015 Author Share Posted September 17, 2015 http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/airfoil.html Link to comment Share on other sites More sharing options...
Flankerman Posted September 17, 2015 Share Posted September 17, 2015 Another example of how lift can be produced is to put your hand out the window of a moving car. Hold it horizontally and it will remain steady, incline the palm slightly and it will tend to lift. Clearly it's not wise to do that while driving the car! Unless your indicators have failed - and you are turning right..... :whistle: Sorry..... I'll get my coat. Ken 1 Link to comment Share on other sites More sharing options...
heloman1 Posted September 17, 2015 Share Posted September 17, 2015 Remember Gordon, there are no silly questions, only silly answers. Colin 1 Link to comment Share on other sites More sharing options...
magwitch Posted September 18, 2015 Share Posted September 18, 2015 Because it is not just the shape of the wing section, but the angle it makes with the airflow. This is called the angle of attack - the more nose up the more lift until the wing stalls. So an aircraft flying upside down has a rather inefficient aerofoil and so has to fly at a greater angle of attack to get the same lift. Some aero focussed aircraft (eg Extra 300) have symmetrical wing profiles and only generate lift via AoA so their wings work equally well (or badly) in any orientation. Link to comment Share on other sites More sharing options...
bhouse Posted September 18, 2015 Share Posted September 18, 2015 The definitive answer can be found in the excellent BBC radio series Cabin Pressure. It's in the episode called "Abu Dhabi" and pops up throughout the episode. Although the audio recording is difficult to find online, the script is readily available. 2 Link to comment Share on other sites More sharing options...
Rick Brown Posted September 18, 2015 Share Posted September 18, 2015 I know that the curved cross-section of an aircraft wing means that the airflow on top is moving faster than that below, resulting in a higher pressure underneath, which provides the lift so that the plane can fly. But then how can it fly upside-down? Pure magic. Everyone knows planes can't really fly. It's an optical illusion. Rick. 1 Link to comment Share on other sites More sharing options...
GordonD Posted September 18, 2015 Author Share Posted September 18, 2015 The definitive answer can be found in the excellent BBC radio series Cabin Pressure. It's in the episode called "Abu Dhabi" and pops up throughout the episode. Although the audio recording is difficult to find online, the script is readily available. I have all the audio recordings, but listening to the first episode is not a good idea. Because then I'll feel compelled to listen to the second one, and then the third... Link to comment Share on other sites More sharing options...
bhouse Posted September 18, 2015 Share Posted September 18, 2015 I must admit to playing the entire box set on a drive from the UK to Italy. Twice. Pure comedy genius. Apparently John Finnemore's dad is a captain with Virgin. Link to comment Share on other sites More sharing options...
Max Headroom Posted September 18, 2015 Share Posted September 18, 2015 Remember Gordon, there are no silly questions, only silly answers. Colin 42 Trevor 1 Link to comment Share on other sites More sharing options...
noelh Posted September 20, 2015 Share Posted September 20, 2015 Actually this video provides the 'best' explanation of how lift is generated that I have ever seen. It starts about 3:30 into the video. But the video is worth watching in full for it's terrific insight into the life of an airline pilot. It was produced by the BBC in a series called 'People like us' which came out in 2001. ​ Link to comment Share on other sites More sharing options...
GordonD Posted September 20, 2015 Author Share Posted September 20, 2015 Just in case anybody didn't realise, this was an episode from a sitcom - a spoof on those fly-on-the-wall documentaries. The unseen presenter went round various places interviewing people about their jobs. I remember one set in a police station, where the fax machine had run out of paper and they asked another station if they could fax over some more... 2 Link to comment Share on other sites More sharing options...
noelh Posted September 20, 2015 Share Posted September 20, 2015 Don't spoil it. I was hoping they'd be sucked in. Link to comment Share on other sites More sharing options...
GordonD Posted September 20, 2015 Author Share Posted September 20, 2015 Link to comment Share on other sites More sharing options...
Andrew Jones Posted September 21, 2015 Share Posted September 21, 2015 This is how aircraft really fly , Al Murray " God does exist ". https://www.youtube.com/watch?v=i9q113rIwVo Andrew Link to comment Share on other sites More sharing options...
Alan P Posted September 21, 2015 Share Posted September 21, 2015 Just in case anybody didn't realise, this was an episode from a sitcom - a spoof on those fly-on-the-wall documentaries... It's still the most accurate portrayal of airline pilots I've ever seen 😊 Link to comment Share on other sites More sharing options...
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