Flying low and fast ...

[Dobmatt]

I've noticed my Inspire 1 Pro slowly lowering the altitude when flying fast, and slowly climbing back at stops. The vertical graph looks like a saw. This is particularly annoying and dangerous during very low passages a few meters above ground. Is it normal and should be compensated with throttle up?

 

[Alastair]

I've noticed my Inspire 1 Pro slowly lowering the altitude when flying fast, and slowly climbing back at stops. The vertical graph looks like a saw. This is particularly annoying and dangerous during very low passages a few meters above ground. Is it normal and should be compensated with throttle up?

Did you have the VPS set to off?

 

[Dobmatt]

Did you have the VPS set to off?

Indeed, I do.

 

[The Editor]

I've noticed my Inspire 1 Pro slowly lowering the altitude when flying fast, and slowly climbing back at stops. The vertical graph looks like a saw. This is particularly annoying and dangerous during very low passages a few meters above ground. Is it normal and should be compensated with throttle up?

Normal and yes, you need to compensate slightly with some throttle input.
All multirotors will loose lift with an acute angle of attack of the rotors - some more than others.
Although the flight controller will compensate to a degree it is not foolproof and some altitude loss is inevitable at high speed.
It's physics I'm afraid.

 

[Dobmatt]

Normal and yes, you need to compensate slightly with some throttle input.
All multirotors will loose lift with an acute angle of attack of the rotors - some more than others.
Although the flight controller will compensate toma degree it is not foolproof and some altitude loss is inevitable at high speed.
It's physics I'm afraid.

Thank you, Sir. I can sleep now in peace ...

 

[Harryscopic]

That's to be expected in ATTI mode, but not in P.

 

[Raphael Dahan]

I've noticed my Inspire 1 Pro slowly lowering the altitude when flying fast, and slowly climbing back at stops. The vertical graph looks like a saw. This is particularly annoying and dangerous during very low passages a few meters above ground. Is it normal and should be compensated with throttle up?

In a real helicopter, you push the stick forward,without pooling up the collective, you crash!!!

 

[lake_flyer]

That's to be expected in ATTI mode, but not in P.

No, it isn't:
In both Atti AND P-GPS the barometer assistance is active. Should make no difference. Inspire1's don't have a mode without barometer assistance. You need a manual copter to experience what it is to fly without barometer assistance. Good for practise by the way.

It's physics like the Editor says.

 

[lake_flyer]

In a real helicopter, you push the stick forward,without pooling up the collective, you crash!!!

so right

 

[lake_flyer]

1. Air pressure changes cause the vehicle to drift up or down by a couple of meters over longer period of time or for the altitude shown on the GCS to be inaccurate by a couple of meters including occasional negative altitudes (meaning altitudes below the home altitude).
2. Momentary altitude loss of 1m ~ 2m when the copter levels out after a high speed forward flight. This is caused by an aerodynamic effect which leads to a momentary low pressure bubble forming on the top of the copter where the flight controller is mounted which leads the altitude hold controller to believe it is climbing so it responds by descending.

from the web.....

 

[Harryscopic]

No, it isn't:
In both Atti AND P-GPS the barometer assistance is active. Should make no difference. Inspire1's don't have a mode without barometer assistance. You need a manual copter to experience what it is to fly without barometer assistance. Good for practise by the way.

It's physics like the Editor says.

I'm used to instinctively compensate when I fly other other quads manually. Physics are always there, can't blame that for a system's flaw. So the barometer assistance isn't assisting correctly all the time, even if because of that low pressure bubble. Sensor enclosure design, placement, firmware algorithm... whatever, I just hoped it was more advanced, that's all.

 

[lake_flyer]

It's good practise not to fly lower than say 12-15 feet. Lower than that is a risk because of the barometer and GPS inaccuracy. Fortunately we have VPS that kicks in at that level. But it is never safe to rely on it. Normally I have it switched off, as well as the self adaptive landing gear.

 

[seanmclean]

Physics yes, but with downward facing ultrasound it 'should' have the capacity to auto add throttle to maintain altitude fairly precisely.

 

[The Editor]

Physics yes, but with downward facing ultrasound it 'should' have the capacity to auto add throttle to maintain altitude fairly precisely.

But it's not facing down at high speed it is offset by around 35degrees due to the tilt of the aircraft and therefore has no reflection back to the transducers.
The frequency is not high enough to enable an update interval to be of any use at high speed.
Additionally the system was never designed for this function and was purely an aid for flying indoors to maintain positional accuracy when no GPS was available.