I’ve had friends come back from vacations with harrowing stories about turbulence so bad they thought the wings were going to fall off. Of course, it didn’t happen, and it’s extremely unlikely that it could happen.

I came across this video this morning which is a 3:35 piece of the PBS series “21st Century Jet” about the 777 showing what kind of testing they did on the 777 wing.

As you can see, they bent that wing up more than 24 feet from level and only then did it break, at more than 150% of the strongest force that could expected in flight.

And this isn’t the only wing testing they do. They also flex the wings up and down for long periods of time to simulate sustained periods of turbulence.

I can’t believe that this has actually turned into such a huge thing.

The question of the month appears to be this. If you put an airplane on a treadmill and get it going really fast (working up a heck of a sweat, mind you), will it eventually take off?

Upgrade: Travel Better points out that David Pogue of the New York Times even picked this one up a few days ago (and that’s where this picture came from, though the headband addition was mine). So what’s the answer?

No, it won’t.

Now I’m amazed at how many conflicting opinions there are on this thing, because it seems very basic to me. Let’s say you get that treadmill humming in a really big gym (with no wind around) and the plane has full takeoff power going. Those wheels are racing on the treadmill, but it doesn’t matter what the wheels do here. Aircraft get lift from air passing over the wings, and in this case, there isn’t any.

If there’s no wind in the area and the plane isn’t moving through the air, then there will be no air passing over the wings. It’s that simple. Now if there happens to be a 200 knot headwind, you’re going to get airborne whether your engines are on or not, but I’m assuming that’s not part of the question here.

Ever wondered why airplanes take off on different runways at different times? Well, they always want to take off into the wind. The reason for that is once again that ground speed doesn’t matter – it’s airspeed that does.

For simplicity’s sake, let’s say you need 100 knots of airspeed to get off the ground (meaning the air is moving over your wings at 100 knots). If the wind is blowing 10 knots down the runway and you take off into it, you only need to be going 90 knots on the ground, because 90 knots plus the 10 knots that the air is already moving will get you where to need to be.

Conversely if you took off the other way, you would need to be going 110 knots because you’ve already got 10 knots at your back. Only when you get to 110 knots on the ground would you have 100 knots of airspeed.

On that treadmill, air is not moving over the wing at all so it’s not taking off.

Airline operations are no simple thing. Almost everyone has had that painful moment sitting in one airport with clear blue skies while being told that the flight is delayed due to weather . . . or crew . . . or maintenance . . . or, well, you get the idea. Though you may like to believe otherwise, the airline really isn’t lying to you. The operations are so complicated and interwoven that one small problem can have impacts far down the line. It’s very difficult to make changes to the entire schedule so that it becomes an orderly change.

Customers fly into Keflavik from the US/Canada overnight and arrive in the morning. Then they send the fleet to a variety of European destinations where they promptly turn around and come back to Keflavik in the afternoon. Finally, those planes head out to the US in the evening and start the whole thing over again.

US Airways announcement today that they’re adding winglets to their 757s made me think it’d be a good time to repost an old piece I wrote on winglets back on the PriceGrabber Airline Discussion Forums back on July 19. So, with a few updates, here it is . . .

Chances are good that if you’ve flown on a 737 or a 757 lately, you’ve seen some abnormally large pieces of metal sticking straight up off the end. These things, called winglets, look pretty funny if you’re not used to seeing them, but airlines are installing them like they’re going out of style. Why? Yup, you guessed it – they save fuel.

The real problem here is called a wingtip vortex. As airplanes fly through the sky, they obviously disturb the air. At the edge of the wing, drag is created becuase the shape causes the air to swirl around in a funnel shape. And when drag is created, it destroys efficiency.

Aircraft manufacturers realized that if you could reduce these disturbances, you could increase fuel efficiency and therefore range. Airbus was the first commercial manufacturer that I can recall to start tackling the problem with wingtip fences. These extend both above and below the wing and have been used on the A300/A310/A320 families. (A320 at left)

Boeing first got into the game with the 747-400 when it came out in the late 1980′s. They installed winglets, which just go above the wing (though most people use “winglet” as the generic term for wintip fences as well). These winglets weren’t very large, but they had the desired effect or reducing the amount of drag created in flight. Most recently, Boeing has moved toward the “raked wingtip” design. This is essentially a horizontal winglet. The 767-400 was the first Boeing aircraft to receive the raked wingtip, as shown at right.

Now, third parties have started to create after-market winglets that airlines can install themselves. The most popular of these is the Aviation Partners Boeing winglets for the 737s and now the 757s. They are blended, which means they curve directly into the end of the wing. These winglets may be really tall and funny looking, but they enable planes to fly further on each tank of gas. This is good for the environment, it saves money, and it extends the range of each plane, and that’s why US Airways is installing them now. It allows them to carry a full load year-round between Phoenix/Las Vegas and Hawai’i as well as from the East Coast to Europe.

So what’s the next evolution of winglets? Well, it may actually not involve winglets at all. Boeing has found ways to incorporate the drag-reducing technology into the wing itself. The new 787 has a pretty radical looking wing design, and the assumption is that winglets won’t be necessary. Look at this picture on the right to see the amazing curvature that you’ll find in the wing. This new wing along with other fuel saving features mean the 787 should see fuel savings around 30% over the 767 it replaces.