Wondering: Who's flying the plane?

[tw]

From the Wall Street Journal, page 1 28 Dec 2001:

An empty plane took off by itself and flew 20 miles before crashing in California's rural Napa County. The two-seater Aeronca Champion had a starter system required the pilot to get out and hand-crank the engine.

It was obviously being flown by Ghost Writer. Word!

[MaggieL]

Many light aircraft will fly unassisted for quite some distance, as long as you're not fussy about where they go. When hand-propping, you're supposed to verify tha the throttle is not full-open, and that the tail is tied down and ideally that somone qualified is at the controls holding the brakes down.
There was a similar case with an airplane that had an electric starter (but a dead battery) a few years ago over at Northeast Philadelphia (PNE)....it made it all the way across the airport, through/over a fence and bounced off a passing school bus before fetching up against an apartment building.

[juju]

That's hilarious. :)

Something occurs to me...

Aren't planes usually tied down so this doesn't happen? My dad's Cessna was always pretty tied down. Why was the plane just sitting there?

Also, what kind of conditions need to occur for this to happen? Could it happen with a strong enough wind, or does the plane actually need to start itself up and go?

[MaggieL]

Light airplanes parked outdoors are tied down to keep them from blowing around. Airplanes about to be flown are not, and unfastening tie-downs is ordinarily a part of preflight. But when hand-propping an airplane you're going to fly alone, procedure usually calls for the tail tiedown to be left in place until after the engine is started and safely running at idle. Ideally, an airplane being handpropped has a pilot at the controls, but this isn't always possible.

With a strong enough wind, any aircraft will "fly" in the sense of becoming airborne. "Strong enough" is defined by a characteristic airspeed called the "stalling speed" or V sub S, which on the airplane I fly is 54 knots...in a 54 knot wind straight on the nose, the wings will generate enough areodynamic lift to pick the airplane up off its wheels, and drag will start pushing it in the direction of the wind, since the wheels are no longer creating friction with the ground. An Aeronca Champ has a stall speed around 36 knots, 33 if the flaps are down.

With high enough winds and low enough stall speed, wierd stuff can happen. Some ultralights have *very* low stall speeds; when an aircraft's stall speed is less that the current wind speed, it can hover, or fly backwards. I've seen this done.

When you start getting ino the realm of heavy multienegine aircraft, stall speeds go up into the hundreds of knots; only wheel chocks are required to secure such airplanes unless there's a tornado or hurricaine.

[tw]

Originally posted by MaggieL
An Aeronca Champ has a stall speed around 36 knots, 33 if the flaps are down.

That was the part I did not understand. A pilot just starting his plane would not yet have lowered his flaps. But since the speed difference is so little, then that would explain why a plane, probably without flaps, would have still been able to takeoff.

However, think about it for a minute. How did that plane know which way to turn for the runway? Spooky.

I'm telling you, it was Ghost Writer.

[MaggieL]

Originally posted by tw


However, think about it for a minute. How did that plane know which way to turn for the runway? Spooky.

Whatever makes you think it needed a runway? A fully-loaded Champ can clear a 50 foot obstacle from a standing start 500 feet away. This one didn't even have the weight of a pilot to cope with. They were always very much at home operating from unpaved grass strips.

So all it needed was full-throttle and 300 feet later it would have been airborne all by it's lonesome. No pilot, no runway, no worries.

What's the full load for a Champ? Just curious how airborne it could be at 300 feet. That seems pretty short (not saying it's wrong - just saying that it's pretty short).

[MaggieL]

Originally posted by dhamsaic
What's the full load for a Champ? Just curious how airborne it could be at 300 feet. That seems pretty short (not saying it's wrong - just saying that it's pretty short).

300 feet was a guess. But takeoff run at max gross of 1220 lbs (which would be least 170 pounds--the FAA standard person--heavier...probably more unless this guy had a *bunch* of baggage) in zero wind is 500 feet to clear a 50 foot obstacle (think "a four story building")...and I'll bet it wasn't a zero wind day. With nobody at the controls the aircraft would have weathercocked into a direct headwind, and bear in mind that with a 36 knot headwind (brisk but not impossible) the takeoff run is *zero* feet. :-) Empty weight of the aircraft is around 750lbs...the structure is doped fabric stretched over a wooden frame; it's basically a powered kite.

I'll always remeber my first solo takeoff...I'd been training in a Cessna 152 (max gross 1670 lbs, aluminum monocouque constuction) , and it took off like a rocket, with no instructor on board. Some STOL aircraft like to demonstrate takeoffs in the *width* of a runway, or from *inside* a hangar...and the Champ is a cousin to those designs.

[lisa]

Yes, I too remember my first solo and wondered how the plane could climb so fast and if I would be able to fly it because it acted so differently.

As for the tiedown and hand-proping, don't forget that some airports look down on people who start their planes IN the parking spot because of where the propwash goes -- they prefer the planes to be pulled out where, unfortunately, there are no tiedowns.

Ah, the world of trade-offs.

Wow. That's pretty impressive - only 750 pounds. I've never seen one, so I was figuring something more like my dad's Cessna. Wow.

So, then, how fast does the aircraft ascend? That is, once it has actually lifted off the ground, how far (feet) would it take the champ to rise, say, 200 feet? I realize that this is determined by how much the pilot is trying to "make it go up" - so we'll define it as "the hardest ascension without stressing the plane or being in danger". Is 300-500 feet unusually short for a private plane?

I found more information here:

http://www.geocities.com/CapeCanaver...52/champi.html

How much do these normally go for?

[MaggieL]

Originally posted by dhamsaic
Wow. That's pretty impressive - only 750 pounds. I've never seen one, so I was figuring something more like my dad's Cessna. Wow.

So, then, how fast does the aircraft ascend? That is, once it has actually lifted off the ground, how far (feet) would it take the champ to rise, say, 200 feet? I realize that this is determined by how much the pilot is trying to "make it go up" - so we'll define it as "the hardest ascension without stressing the plane or being in danger". Is 300-500 feet unusually short for a private plane?

Rate of climb in this situation would depend on a bunch of stuff, including what the trim was set for...hard to say. Going up 1000-1500 feet per minute with people on board is not at all unusual. When you ask "how far" rather than "how fast" you're asking "angle of climb", rather than "rate of climb", and angle depends on rate of climb and groundspeed, which in turn depends on airspeed and windspeed...as I pointed out with sufficient headwind, angles of climb of 90 degress (and more, in the "flying backwards" scenario. :-) ) are not impossible in some aircraft..
*Climbing* under power usually does not endager the airframe due to stress. (Although I remeber a high-performance takoff demonstration Lisa did once in my Cardinal that was quite a ride) Aerobatic manuvers once aloft (gaining speed by diving, ferinstance) are another story.