# MSFSSimconnect Detecting Vertical Speed

#### Sandy505

I am in the process of writing my own flight log and along with incorporating the latest OFP from Navigraph, I've been able to hook into Simconnect and display the real-time vertical speed. However, what I need to get to is the ability to detect the vertical speed on landing. Looking at all the variable's available in the SDK, I can't see a clear way of doing that. Any ideas?

You'll need to run a calculation that relies on a sudden zero VS to indicate a landing. That should give you the figure you need to calculate the G rate. Pseudo-code:
Code:
``````while VS is negative and VS is not zero
store current VS
loop
if VS is zero
use store current VS to calculate the G force based on the vertical speed over that last X feet``````
One these might help:

So... a bit of interesting (read: time-wasting ) research later, it appears that the G-force experienced by the passengers (and crew) at touchdown varies by the length of time it takes the undercarriage oleos to achieve full compression. The formula is (initial velocity - final velocity) / (time x 9.81) where 9.81 m/s is the acceleration due to gravity. If an aircraft has an initial vertical velocity of 15m/s, a final vertical velocity of 0 m/s and the oleos take 1 second to compress fully, the calculation is (effectively)

7.5 / (1 x 9.81) = 0.765G

or if you want it in feet per second

25 / (1 x 32.18) = 0.765G

If the oleos take one half second to fully compress, then I hope you have a good chiropractor.

7.5 / (0.5 x 9.81) = 1.52G

Actually that sounds about right for a 'normal' re-association with the runway. Mind you, I did assume that the OP was leading on to logging the G-force at landing but knowing me, he probably wasn't