Thursday, December 19, 2013

Floating to the ground


Yesterday we saw a hard and heavy landing of a giant Airbus A380.  Smaller, lighter aircraft tend to have a different problem.  In the right conditions, once they get into ground effect they seem to 'float' - drift on down the runway, almost as if they want to stay in the air rather than land.  If they don't have a heavy load on board and have used up most of their fuel, it can be even worse.  (Miss D.'s light aircraft does the same thing - it's got excellent lift, and is very light, so when she's coming in after a flight with almost-empty tanks it's sometimes hard to persuade the plane to get down and stay down!)

As an example, here's a Bombardier Dash 8 commuter airliner of Flybe, a British regional airline, landing at an unidentified airport in high crosswind conditions.  Look how the pilot has to not only 'crab' into the wind, but work really hard to overcome ground effect and plant its wheels on terra firma.  I recommend watching it in full-screen mode.





I've flown in several Dash 8's and similar aircraft in the US, Europe and Africa.  All of them have exhibited that behavior when the winds are stronger than a gentle breeze.  Interesting how some aircraft designs do that, while others fall out of the sky with an ungainly 'thump!'.

Peter

6 comments:

Anonymous said...

The Dash 8-being descended from a long line of de Havilland Canada STOL aircraft, right back to the DHC-2 piston Beaver, just naturally wants to fly.

I've been rattling around eastern Canada this last week in the Q 400 version of the Dash 8.

I timed 3 take-off rolls. Fully loaded from a standing start, they were airborne with wheels up in 25 to 27 seconds.

Getting them down...well, they just don't want to. Too much fun up there :-)

Old NFO said...

That's why Navy and ex-Navy pilots PLANT the bird... Dump the lift and get er done...

On a Wing and a Whim said...

NFO - funny, on a crosswind day, so do I. Although I can't plant her too hard, or the tundra tires and landing gear squat and spring back, launching her back up into the sky.

I've never been excellent at those long, gentle landings where it greases on and the passenger never notices we've landed until they realize we're turning off the runway. Mine are more like "Um, should I take off again and fly halfway down the runway to my turnoff? I landed right at threshold and taxiing is going to take forever..." (Had a tower "suggest" I do that once or twice, to get me out of the way.)

Murphy's Law said...

Yeah, that's where I have the trouble in a crosswind...I'm floating and the wind is pushing me sideways towards the edge of the runway...and usually towards the Air Force's C-5A parking area on the downwind side of my home field.

I've learned to come in with a bit of power still on and 10 degrees of flap--or none at all--and once I'm over the numbers, chop the power, flare hard and drop it like a rock, ideally just on the mains first. It's a rough landing but I've still got control and I'm not fluttering around on the ground effect cushion.

On a Wing and a Whim said...

Oooh, flaps. I miss flaps. I slip. A lot. I can come in and slip her down to just over ground effect, let her level out, and then try to just run out of airspeed for a three-pointer about the same time as she meets the ground.

On the other hand, I stall at 28mph. STOL is what this plane was designed and modified to do, and she does it very, very well. I also miss your cruising speed, but I'm not trading my gal anytime soon.

Joe in PNG said...

Heavens, back when I was flying, I upgraded from Cessna 152/150's to the 172 after getting my licence. I was rather surprised at the ground effect float I'd get when landing.
Sadly, the money ran out before I could really master the beast. Kind of miss it, really.