Friday, November 10, 2017
Aborted Landings

 

 

Dynamic Rollover

We see all too often new pilots attempting to land when the aircraft is drifting with the wind. In gusty conditions this can mean that the aircraft touches down on its landing gear whilst translating.  The tendency is for a pilot to attempt to abort the landing at this stage, but sadly it is often way too late.  Once the aircraft touches down, the skid or point of contact, acts as a pivot.  By increasing rotor thrust in an attempt to take off again, you may introduce an undesirable consequence.  Because the aircraft rotor thrust vector is not vertical, the increase in thrust also brings with it an increase in the resultant horizontal vector, and along with it an increase in angular momentum.  This then acts around the pivot point and not the centre of gravity, and a Net Rotation is the result.  This can act on the aircraft alarmingly quickly and cause the aircraft to rotate to such an attitude that the rotors strike the surface.  What can we do to prevent this accident from happening?

Landing with No Drift

As we can see above, the first cause of the accident was landing with drift applied, and this effect can be experienced in any direction, because any point of contact can act as a pivot. The aircraft should be landed with zero drift velocity, and that will prevent there being a point of contact acting as a pivot.

Aborted Landing

At Flyby Technology we teach our students to abort any landing where there is significant drift on the aircraft, certainly before any part of the aircraft structure touches the surface.  If you apply power after a pivot has taken effect you increase the angular momentum, the result may be a Dynamic Rollover. Once the aircraft is in contact with the surface reduce the power completely to zero.  This will reduce the rotation from the horizontal component of rotor thrust.

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