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  #1  
Old December 27th 04, 08:48 PM
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Bob Moore wrote:
"Ramapriya" wrote
Sorry for being naive here Bob, but does touching down with the

nose
not pointed down the center of the airstrip, which is what I

presume
would happen if you touched down in the crab, bust the wheels?


Certainly not good for light general aviation aircraft, but the
Boeings seem to take it easily.


Unless you happen to be flying an Ercoupe, which is designed to land
crabbed in a crosswind. The gear is purposely beefed up for this
purpose. On most other GA aircraft, it's definitely not advisable.

On one of my very first lessons, I was on final following a Tomahawk
landing with a stiff crosswind. My instructor told me to watch the
Piper closely to see how the pilot corrected the crab just before
touchdown, to land the plane with the nose aligned with the runway.
Well, the (student) pilot didn't correct for the crosswind and touched
down while still in a crab. We watched the right gear leg fly off the
bottom of the wing and take out the right side of the horizontal
T-tail. The plane slid to a stop on it's right wing, with pieces of the
tail scattered over the runway. My instructor then informed me that I
had just learned a valuable lesson about crosswind landings at
relatively little expense to me.

John Galban=====N4BQ (PA28-180)

  #2  
Old December 26th 04, 04:29 AM
Morgans
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"Ramapriya" wrote in message
oups.com...
Bob Moore wrote:

the crab at the last second before touchdown. Boeing said
that if one was not comfortable doing that, just touchdown in
the crab. Of course autoland approaches always use the crab


Sorry for being naive here Bob, but does touching down with the nose
not pointed down the center of the airstrip, which is what I presume
would happen if you touched down in the crab, bust the wheels?


Think of it this way.

All that mass is moving straight down the runway, still pretty fast. It is
going to try to keep going straight pretty fast. The only thing to cause
enough stress on the gear to try to break the gear is the tires.

What happens when the tires first touch down? A big puff of smoke, as the
tires spin up to speed. Just a little bit of force involved to do that. It
would take a whole lot more force to make that big bird go sideways, right?
So what happens? The tires skid a bit sideways for a while, until the FO
(the captain wouldn't have screwed up by not kicking the crab out, right?
g ) wakes up and corrects to get the thing pointed straight down the
runway, right?

It has been my experience, from riding the heavy iron, that the combination
of a slightly low wing and kicking the crab out is what is used. I say that
only from observation, as it feels like one side hits, followed *very
quickly* by the other side landing. Sometimes, it does feel like you are
taking a quick ride towards the lights.
--
Jim ( I'm grading your landings, Captains) in NC :-)


  #3  
Old December 28th 04, 11:44 AM
David CL Francis
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On Sat, 25 Dec 2004 at 23:29:34 in message
, Morgans
wrote:

It has been my experience, from riding the heavy iron, that the combination
of a slightly low wing and kicking the crab out is what is used. I say that
only from observation, as it feels like one side hits, followed *very
quickly* by the other side landing. Sometimes, it does feel like you are
taking a quick ride towards the lights.


I have a little book that describes in detail a 747 flight from Toronto
to Heathrow. An autoland is carried out at Heathrow. It describes how,
in the first stages of the landing, the aircraft is aligned with the
runway in a crosswind by heading slightly into the cross wind. At 500 ft
to go the auto-pilot changes to 'runway align' and the wing is lowered
on one side and the rudder keeps the aircraft aligned with the runway. I
understand that the maximum autoland crosswind is 25 knots.
--
David CL Francis
  #4  
Old December 25th 04, 11:46 PM
G.R. Patterson III
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Ramapriya wrote:

1. Like there are crosswind landings, are there crosswind takeoffs too?
If yes, what's the procedure of takeoff?


Yes. The aileron on the upwind wing is raised as if you were banking the
aircraft in that direction. The aircraft is kept straight by use of rudder. The
nosewheel or tailwheel is usually kept down a bit longer for steering. With
light planes, flaps may be retracted so that the plane leaves the ground at a
higher speed than normal. Once the plane leaves the ground, the pilot adjusts
the controls to achieve co-ordinated flight.

2. In crosswind landings, it's recommended that one lands on only the
upwind wheel. Since this would almost always tilt the upwind wing
groundward, would there not be an engine strike? I'm especially
thinking of aircraft like the 737 and A320...


Yes. In aircraft with engines under the wing, the plane is usually landed by
either landing sideways and allowing the gear to kick it straight or (more
usually) coming in at an angle and kicking the aircraft in line with the runway
by using the rudder just before touchdown. This latter method is called the
"crab and kick" method. There are several old videos floating around of 747s
landing at Hong Kong's old airport. In one, the plane obviously touches down at
at least a 20 degree angle to the runway. The amount of smoke from the tires is
impressive. In another, the plane banks just before touching down and loses an
engine when the engine hits the pavement.

3. How to slip an aircraft sideward? I'm visualizing a situation on
final when a draft of air suddenly blows the aircraft a bit off-center
and when it might be a bit late to try and bank the craft to get it
back into proper alignment.


When you bank an aircraft and use the rudder to counter the yaw effect, it will
turn. If, however, you don't counter the yaw, it will slide sideways towards the
low wing. If you actually push the rudder in the opposite direction to enhance
yaw, the plane will fly sideways. This is a slip. One use for a slip is to keep
the plane lined up with the runway when a crosswind is trying to blow the plane
sideways. Another use is to increase the rate of descent if you're too high on
final.

The gusty wind situation you describe is usually handled by normal maneuvers
(such as a small S-turn) while using throttle to keep from touching down. In
extreme cases, the pilot aborts the landing and climbs back up to try again.
Slips are, however, one tool that a pilot can use to handle gusts, so it
wouldn't be unusual for a pilot to do so.

George Patterson
The desire for safety stands against every great and noble enterprise.
 




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