Oh, All-Knowing One:
I live in the flight path of Lindbergh Field in South Park (I love saying that), and I was wondering. Sometimes planes will flash their lights when approaching. Is it because there is something in the way, trouble, or the pilot is just having fun? I need to know.
-- Truly caught in the headlights, South Park
What's that odd noise at the corner of First Avenue and Hawthorn just after planes fly about 100 feet overhead on their way to San Diego International Airport? At times it sounds like the planes are pulling 1000 feet of plastic wrap.
-- Coby Taylor, downtown
Dear Mr. Alice:
Why are airplane covers referenced to as hanger? You don't hang the planes in a hanger.
-- Sam, San Marcos
Here's another one that will outwit your spell checker. It's a hangar, Sam, not a hanger. Big difference. The difference between German and French, in fact. "Hanger," the thing your clothes fall off, is from German. Hangar, the thing in which you park your plane, is the French name for a building something like a carport. Before the mid-1800s, you'd put your horse-drawn carriage in it. But when the flight-crazed French began fiddling with gliders, I guess you left your carriage out in the rain and stowed your precious plane in the family hangar.
Before you get to the hangar, you have to land. I'm assuming here that our South Parker is caught in the big white lights ahead of the wings, on either side of the fuselage -- landing lights or obstruction lights. (All commercial airplanes have strobes and other flashing lights, but not all flash landing lights.) According to aviation ops and FAA staffers at Lindbergh, some pilots will flash the lights once their gear and flaps are down, as the plane descends on the final leg of the pattern. It just notifies the tower, other planes on a taxiway, birds, dogs, whoever, that the gear is down and tons of fast-moving metal are about to hit the runway. There's no federal regulation that they do this; it's airline policy. Some require it, some don't.
We took a swat at Cory's question before, but it's another one that seems to generate a lot of mail. Spent a couple of weeks quizzing aircraft engineers, wind-tunnel folks, all kinds of experts. All agreed that the incredible tornado wind that follows a plane is the air vortices caused by the pressure differential above the wings and under the wings. They also agreed that the crackling or whip-cracking sound must be the vortex winds interacting with something on the ground. The wind itself wouldn't be noisy. We'll put this out here one more time to see if we can shake loose a more precise answer.