Tuesday, November 20, 2012

Air Brakes

One of the most impressive machines to ever fly during last century was the SBD Dauntless.  Flown by both the United States Navy and Marine Corps during World War II, this plane functionally did it all.  

If you needed a scout plane, it was prefect.  With an range of over 1,000 miles, huge chunks of the South Pacific could be covered with ease.

If you needed extra craft for combat air patrol, its nimble behavior and two sets of machine guns (one controlled by the pilot with the other set controlled by a back-seat gunner) would get you through in a pinch.

If you needed to plant a 1,000-pound bomb on the flight deck of an enemy aircraft carrier, this was the machine to do it.  Just ask the Japanese.   

From altitudes up to 12,000 feet, pilots, after staking out their prey, would push the plane into a dive of 70 degrees. That is damn near straight down.  Adjusting wing trims and applying solid training, bombs would be released from about 1,500 feet after a harrowing 30-second plummet. Yanking back on that stick like it could be the last thing he did (because it could be), the pilot was subjected to forces of five or six times the pull of gravity.  The rear seat gunner, who sat back-to-back with the pilot, recorded any hits as he was looking towards the rear of the plane.  Roaring away from the target at speeds of 275 mph while almost kissing the ocean waves, it was a straight shot home.  Basically, take the craziest, steepest roller coaster ride you have ever ridden, and you're not even close.

That 275 mph figure is pretty key.  Not 300 mph. Not 350 mph. Smooth and steady at 275.  This classic photograph shows why....

Take a look at the trailing edge of the wing.  Do you see those holes? No, they are not from gunfire.  They are called dive brakes.  Opened at the beginning of the dive, the plane's speed is limited as the holes induce drag. 

Airplanes also use what is a called an air brake. Instead of "breaking a dive", they introduce huge amounts of drag while the plane is in level flight or landing. 
 "Top Gun" really played up the role of the air brake.  The star of the movie, an F-14, was about to get shot down.  A secondary character, played by a complete lunatic, is flying the plane and pulls the brake.  The enemy plane rockets in front of said movie star, and the enemy gets shot down. 
Natalie and I were walking the park the other day.  Always trying to be keep my eye peeled for bird photos, I looked over my left shoulder and saw a Bald Eagle in level flight.  I have not preconceptions that I am cool here, but I think I saw him before he saw us. 
Pulling the camera from my hip like Doc Holliday would a six-shooter, I snagged some pictures.  During the exposures, the bird suddenly seemed to notice us and all forward progress basically stopped.  For a brief moment, this Bald Eagle was basically suspended in mid-air.
The images were mushed together in Photoshop.

Looking at the time stamp on the camera, I can tell you all five images were taken in less than one second  (my camera can shoot eight frames per second so this makes sense).

Viewing images #1 and #3 (from the left) one can clearly see the how the feet have left their "stowed" position and have been swung forward.  Looking at image #2 on the master copy I have on my computer, the legs are still forward - they were simply pointing straight at me when I took the image and are therefore hard to see here.
My point here might be this: airplanes and birds aren't so different.  Afterall, birds were the inspiration for planes in the first place.  I find it kind of cool how both flying machines have strategies for solving the same problem.
If the airplane needs to slow down, air brakes/dive brakes are deployed.
When a Bald Eagle needs to slow down, they do the same thing.
How cool.

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