Sunday, 11 April 2010 07:29
Dear Capt Lim!
Firstly, thank you for taking the time to set up such a wonderful site! My greatest respect and admiration to you and your profession!
I am a classical musician and travel constantly - 90% of which is by air. I generally love flying but for some reason and sometime developed a bit of a minor "phobia" of turbulence. I will get straight to my points (questions) as most of turbulence related aspects are answered in your wonderful site.
1. Sometimes during the flight in good - cloudless weather conditions the airplane "hits" wind gusts... are they dangerous for the structure and do the pilots see it coming on the radars?
2. I recently took some flights on the 777-300ER and 757-300. During those "gusty" conditions and generally in turbulence, I noticed that apart from the obvious wing "bouncing" (I was sitting at the back and could look in to the whole forward section of the airplane) the actual fuselage was slightly bending up and down – especially more pronounced in 757-300...
Is it normal and is it safe?
Thank you a million in advance!!!
(Principal violinist of the Royal Opera House, Covent Garden, London)
Turbulence as you have mentioned in ‘good-cloudless weather conditions’ is known as clear air turbulence (CAT) - something which I have elaborated many times in my site. Quite often, pilots may be aware of them from their weather charts but at other times it is difficult to predict them. CAT cannot be seen on the radar as compared to turbulence associated with clouds.
As regards to the structural integrity of planes, I reproduce part of the 2 answers I have written on 2 articles in one magazine below:-
1. Turbulence and airplane structure
"Another air traveler was concerned about how the constant turbulence and the shaking of the planes might affect its body structure and perhaps compromise on passenger safety.
Well, strict airline guidelines dictate that when a plane is certified fit for carrying passengers, it must pass the stress test. For instance, at the planning and development stage of the Boeing 777, the wings were thoroughly tested to see if it could survive the strongest force that turbulence and bad handling could produce in the air or on the ground. During this particular test, the engineers wanted to see if the plane could take up to 150 percent of the strongest force that it could meet in flight before it broke up. They stressed the wings in a test rig and it only broke after it had bent 24 feet which was what they had predicted!* (*Sources: Boeing 777 Ultimate Wing Load Test)
This goes to show that the structure of the plane is incredibly strong. That is why the body of the Boeing 777 that crash-landed at the London Heathrow airport in 2008 was still reasonably intact when it impacted on the ground.
The launch of the Boeing 787 plane was delayed for two years because of structural issues. As you can see, the airline industry makes it imperative that the planes must be structurally sound before letting any passengers to fly in them."
"Turbulence continues to be the number one fear-trigger in flight. Most first time travelers would get a shock on the first encounter of turbulence which ranges from light, moderate to severe.
How do they basically feel like? Well, light turbulence or chops would manifest as some slight and rapid bumpiness. Moderate turbulence is light chops with greater intensity but with rapid bumps and chops. A severe one would cause the occupants to force against their seat belts and loose objects would be tossed about.
During turbulence, if you look outside the window, the wings would flex a bit and the engine may shake a little too on the pylon. Well, they are designed to do so. There is nothing to worry about as the wings would not snap nor would the engines drop off!"
I hope that answer your two queries.