An interesting point was raised on another forum and it was answered by various. I then added to the answer to explain some anomalies that you can experience when landing out at different heights to what is recorded as Zero for Home Point.
I know regular flyers will probably already know this - but new owners may not realise the significance. This is ONLY for the Standard Phantom as it does not have VOS ...
OK ...
Standard auto land at Home Point :
The aircraft descends based only on barometric pressure and its recording of zero height. As it descends it nears the ground and just before touch down it slows to not land hard. This can be about 50cms to about 1m of ground depending on barometer ..
Auto land at point LOWER than Home Point :
Aircraft descends exactly same and slows as it approaches zero height. It is expecting to touch down but it doesn't. It continues to descend ... but it will continue to do it slow as it cannot change its zero setting and expectation to touch down. The fact it now has negative display of height means nothing to it.
Auto land at point HIGHER than Home Point :
Again we have same descend and aircraft expecting to approach ground zero and slow but if the new landing point is higher by similar or more than the original home point - the aircraft will not slow before touch down. Without the VOS system of the other Phantom models - it has no way to know ground is higher ... barometric pressure does not alter for this.
The last one of higher than home point is one I regularly encounter because of the rising ground to my house from the river bank.
I prefer to manually land anyway so its a technical point for me ... but worth passing on I think. New owners may not be aware of the limitation of the landing system in this, especially in the higher height point.
Cheers
Nigel
I know regular flyers will probably already know this - but new owners may not realise the significance. This is ONLY for the Standard Phantom as it does not have VOS ...
OK ...
Standard auto land at Home Point :
The aircraft descends based only on barometric pressure and its recording of zero height. As it descends it nears the ground and just before touch down it slows to not land hard. This can be about 50cms to about 1m of ground depending on barometer ..
Auto land at point LOWER than Home Point :
Aircraft descends exactly same and slows as it approaches zero height. It is expecting to touch down but it doesn't. It continues to descend ... but it will continue to do it slow as it cannot change its zero setting and expectation to touch down. The fact it now has negative display of height means nothing to it.
Auto land at point HIGHER than Home Point :
Again we have same descend and aircraft expecting to approach ground zero and slow but if the new landing point is higher by similar or more than the original home point - the aircraft will not slow before touch down. Without the VOS system of the other Phantom models - it has no way to know ground is higher ... barometric pressure does not alter for this.
The last one of higher than home point is one I regularly encounter because of the rising ground to my house from the river bank.
I prefer to manually land anyway so its a technical point for me ... but worth passing on I think. New owners may not be aware of the limitation of the landing system in this, especially in the higher height point.
Cheers
Nigel