Sink rate calculation

[acannata]

Dear friends,

how is the touchdown sink rate calculated in PS1?
Is it a mean value or an istantaneous one?
Thank you and best wishes of Merry Xmas and Happy New Year.

Aldo

[Hardy Heinlin]

Hi Aldo,

it's the aircraft's vertical speed right in that moment when the aircraft is touching  the ground.

Actually, "touching" is the wrong word because the act of ground contacting is of an infinitely short duration.

More precise:
... it's the aircraft's vertical speed right in that moment when the aircraft's status is changing from in-air to on-ground.

Actually, "changing" is the wrong word because the act of ground contacting is of an infinitely short duration.

Not better:
... it's the aircraft's vertical speed right in that moment when the aircraft has touched down.

"Has" is the wrong word because the touch down event is a math algorithm in the simulation program which is processed within one time frame. Within a frame the sim doesn't move. The sim universe is quantized. It doesn't matter if I write 2+4 or 4+2, either sequence leads to the sum of 6. The 6 is spit out at the end of the frame, no matter if the 4 "has" occured before the 2 or thereafter.

This ...

if alt <= ground then
- print V/S to instructor
- set ground mode
endif

... has the same effect as that:

if alt <= ground then
- set ground mode
- print V/S to instructor
endif


Cheers,

|-|ardy

[Will]

But there is a transition period from zero weight on the wheels, to full weight on the wheels, right?  At the instant that alt = ground, the plane has another 10-20" to settle as the bogeys rotate to horizontal and the struts and tires compress.  Is that meaningful?

[Hardy Heinlin]

Yes.

The full weight at the end would be meaningful for a touchdown g value. The V/S is then 0. Hence the V/S is taken at the very first touch.

[Hardy Heinlin]

In PSX there's also a nose gear sinkrate captured at the first nose gear touch:






|-|