Simviation Forums

Goodmorning all...

Several commonly held truths for light aircraft that turn out to be myths.

Sometimes it seems impossible to work out just where a particular myth has come from-they just seem to pop up again and again passed on from one pilot to another like a mild cold.

MYTH:  It's better to have a gear up landing on a soft surface.
    This myth says that if you have to land an aeroplane gear up, it is better to land on a grass runway.  Not true.
    If you hit the grass hard (and there's a significant chance that you will) the aeroplane will dig into the dirt enough to suddenly stop your forward motion.  That 's dangerous for the people on board.
   On a hard surface, the vertical energy can be translated into horizontal energy, allowing the aeroplane to slide and decelerate slowly.
    A sudden stop on a soft surface like grass also has potential for much greater damage to the aeroplane.

MYTH:  Taking the weight off the nose-wheel on take-off prevents nose-wheel shimmy and wheel barrowing.
    There is no requirement to take the weight off the nose-wheel on a hard surface runway.  Nose-wheel shimmy is a serious airworthiness defect that should be endorsed in the maintenance release with the annotation that the aircraft is unairworthy.
    Although the action to minimise nose-wheel shimmy once it has occurred is to apply back elevator, continued operation can result in severe airframe damage.
    A specific technique involving a tail low lift-off at mimimum safe speed is required for soft or rough field operations and is usually described in the relevant POH.
    From the Cessna Aircraft Company, Wichita, Kansas USA:
"The recommended rotation speed varies from model to model, but the procedures are the same."  The POH state: Elevator control-lift nose wheel at 55kts.  Our company only supports the technique written in the appropriate operating handbook.
    As the airplane reaches take-off speed, gradually apply enough back pressure to raise the nose-wheel off the ground.
    Too much back pressure during the take-off may cause the aircraft to become prematurely airborne in ground effect.
    As to the possibility of "wheel -barrowing" during take -off, use of the recommended technique will prevent this."

MYTH:  During stall recovery, pick up a dropped wing with opposite rudder-not ailerons.
    This is just wrong.  This extract from the United States Air Force manual of primary flying gives the correct advice.
    The primary use of the rudder in stall recoveries is to maintain direction.  When the back pressure that has caused the stall is released, the stall is broken and the ailerons can be used to level the wings.
    This can be accomplished as the nose high attitude is being decreased.
    Put another way, use of the rudder must be limited to no more than is necessary to check the yaw.
    The wings are then leveled with aileron after flying speed has been regained.  If opposite rudder is used to deliberately raise the dropped wing there is a risk of inducing a spin in the opposite direction.

Some food for thought...    :)

Cheers...Happy Landings...Doug
   

MYTH:  It's better to have a gear up landing on a soft surface.

Only if the soft surface is water.

MYTH:  During stall recovery, pick up a dropped wing with opposite rudder-not ailerons.
    This is just wrong.  This extract from the United States Air Force manual of primary flying gives the correct advice.
    The primary use of the rudder in stall recoveries is to maintain direction.  When the back pressure that has caused the stall is released, the stall is broken and the ailerons can be used to level the wings.
    This can be accomplished as the nose high attitude is being decreased.
    Put another way, use of the rudder must be limited to no more than is necessary to check the yaw.
    The wings are then leveled with aileron after flying speed has been regained.  If opposite rudder is used to deliberately raise the dropped wing there is a risk of inducing a spin in the opposite direction.

Same with the RAF. Unstall the wing, roll with aileron then pitch back to the s&l attitude. The only time you'd use rudder would be to check an undemanded roll - normally centralising the controls is enough anyway.

Goodmorning Charlie...

The best reasoning for landing gear up on the grass in the event of a gear failure is when one gear won't come down.  If one is stuck, most pilots will opt to land completely gear up to avoid a potential cartwheel situation.  However other pilots have landed successfully with one gear up.  In an emergency, the handbook goes out the window, you can't write a guide for every type of emergency.  And in the end, it is up to the bonehead behind the yoke/stick.  He makes the decision, the rest of us just deal with it.

You may be preaching to the choir here, Doug...

First thing I thought of when you mentioned gear up on paved vs. non-paved: The pavement is very abrasive to the belly of the plane, but the friction is very uniform, compared to even the smoothest beach (which, being soft, will pile up unexpectedly). No rocks, stumps, etc. No abandoned plows, rakes, barbed wire, fence posts, logs, termite mounds... etc.

Then there's wet grass: if the ground is firm, even a prepared grass runway, you may not decelerate as soon as you'd like.

In fact, I'm thinking a nice, flat, firm mowed runway could be even worse, when wet, than long grass in a meadow or hayfield, which would wrap itself around the underside, etc. of the plane as it moves along, helping to slow you down.
 
If (when?) it ever happens to me, I hope I have a paved runway available. A long, wide one. With a firehouse and emergency medical services on the field.

If I have a good runway in front of me, I'd feel very hopeful  during any emergency.