Beside the Wing Photography that I posted the other day, I also recorded a video of the aircraft’s right wing during approach and landing. Unfortunately, it was taking forever to upload the video to youtube because the file size is too big (and I was too lazy to compress it). After several days and several failures due to bad internet connection, it was finally finished uploaded.
Since this video contains wing flap movement throughout approach and landing phase (and the activation of wing spoiler during braking), I thought that it might be a good idea to post this video also in this blog. Why is it a good idea? Because I can use it to explain the phases and procedure of an aircraft’s landing and the science behind it. So, here it is, a video of Garuda Indonesia’s B737-300’s right wing during approach and landing phase.
As you can see, after descend to a certain altitude for approach, the flaps (the moveable wing part at rear area) were extended and deflected. However, the flaps weren’t deflected to its full extent, yet. After the aircraft was close enough to the runway, the flaps were then fully extended and the aircraft slowly descended and then touched down. Right after the touch down, wing’s spoiler (the moveable wing part at the center area) was deployed while the engine’s thrust was reversed to slows the aircraft down (not shown). When it was slow enough, brakes were also applied to the landing gear to help stop the aircraft (also not shown).
The process of aircraft landing seems simple from the video. However, for every action done in the video, it has its scientific reasoning in it and in this post, I’m going to explain the reasoning behind it. I hope you understand, so, here it is:
Aircraft’s wings generate lift force porpotional to its airspeed, hence, faster speed means more lift. However, during landing phase, an aircraft must be approaching the runway as slow as possible because it needs to brake and stop after landing. Consequently, to compensate the loss of airspeed, wing’s flaps are deflected, causing wing’s chamber (and also its lift coefficient) to increase. This way, the wings will still be able to provide enough lift force for the aircraft although it is moving slower. Gradually, wing’s flaps are extended as the aircraft slows down until it reaches what so called approach speed and the wing’s flaps are fully extended. At this time, usually, the aircraft is already very close to the runway and it is ready to land.
During the airborne phase in an aircraft’s landing, the wing’s flaps are already fully extended while the aircraft will keep slowing down. Thus, to maintain the lift force, the aircraft’s nose is raised up. This way, wing’s angle of attack increases and causing increase in both lift force (which is needed to keep the aircraft fly) and drag force (which is desired because we want to slow the aircraft down). Then, comes the tricky part: touching down the aircraft.
In landing, aircraft’s altitude is decreased by slowing down the aircraft (Remember, lift force is proportional to airspeed). However, decreasing aircraft’s altitude for touch down must be done slowly or the aircraft will land hard. This is where pilot plays with both engine’s throttle and aircraft’s angle of attack to slowly bring the aircraft down. This process is actually very hard. I, myself, have tried landing several aircraft in X-Plane and only had a few successful landing. Mostly, I landed hard or I bounced back and flied up because I was being too careful.
After the aircraft touched down, wing’s spoilers are immediately deployed. This is done to distrupt airflows arond the wings, causing wings to no longer produce lift to avoid the aircraft flying back up again. On the other hand, the deployment of wing’s spoilers also help slow down the aircraft because it causes flow separation, hence increasing aircraft’s drag force.
During this ground phase, the aircraft needs to come into a full stop to finish its landing. However, because of its speed and massive mass, thrust reverser from aircraft’s engines is deployed first to further slows down the aircraft before brakes is applied to the landing gears. If the brakes are applied first, the landing gears may skid. Thus, a thrust reverser must be deployed first to further slows down the aircraft. After it reaches a certain speed, brakes may be applied to stop the aircraft and after the aircraft stop, the landing phase is technically completed. Later on, the aircraft usually taxis to apron to unload its cargo and passenger.
Fiuh… I think that’s all to tell you about the aircraft’s wings during approach and landing. I hope that I wrote it well so it is understandable for everyone (even for those who are not familiar with aerospace engineering). For the next time, I think I’m gonna make a video about aircraft’s wing during take-off. However, I don;t know when I will got on an aircraft again, so you better not get your hopes high. In the end, I hopes that this post is useful for you.