Geebax
First Officer
Australia
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rreed821 Posted at 2017-9-15 09:44
I have just come across this thread and gone through all the posts. The question I was seeking answered was "What is ATTI" ? And the reason for searching is quite simple, the DJI Manuals are very ordinary and lack technical thoroughness. In any technical documentation there is usually a glossary of terms to explain and provide a x-reference to abbreviations. I also went through the DJI GO manual with a search for ATTI and only found references to ATTI and attitude (flight attitude angle) but no definitions. You don't know if ATTI is an abbreviation or an acronym and the explanations should be in the manual. Somewhat disappointing and quite unprofessional in terms of technical writing that keywords or terms are not properly explained and that such important documents would be released by DJI.
The product is made in China, and it is what it is. How many products made in China can you name that have comprehensive, clear manuals?
But if you come here and ask the question, as long as you don't strike someone in a bad mood who wants to tell you to 'Read The Friggin Manual', you might get a good clear explanation.
So, as I am not in a crappy mood, I will give it a try: The aircraft has 3 modes of operation, P for Position Mode, A for Attitude Mode (or 'atti' mode) and F for Function mode.
The normal flight mode is P mode, selected by the switch on the RC unit. In this mode, all automatic navigation devices are active. But if the reception of the GPS receiver is poor for any reason, and the GPS system cannot get a decent positional fix, the aircraft will automatically switch to A mode. This is when the box bitch announces 'Warning, atti mode'. When this happens, the aircraft effectively shuts off all it's sophisticated positioning systems except the barometric height positioning mode. I have always suspected that the manual description of ATTI mode being 'attitude' mode, really is 'altitude' mode. Because that's all that is now controlled by the aircraft's control system. The aircraft is no longer held in position in space, all it will do is stay at the same height. But this also means it is completely at the mercy of any winds, and may simply drift away and disappear.
As a result of this, new pilots very frequently mistake this drifting away as the magic 'FLYAWAY' that they have heard about on dozens of forums, direct from the lips of other pilots who don't know what is happening either. But the truth is, it is not flying away, you are simply failing to control it. The trick that comes with experience, is to recognise this, and fly the aircraft back towards you and land it manually.
Instead, many new pilots just stand there in disbelief and watch their aircraft vanish from view, because they have not practised manual flying to deal with this occurrence. And the vast majority of them also panic and hit the Return To Home button, then watch in dismay as it does absolutely nothing. Why? Because the aircraft lost GPS reception, and without it, it cannot RTH, and it has no idea where home is.
Fortunately a total loss of GPS signals is very rare, and may be caused by momentary flying near to something that blocks the aircraft's view of the sky, so the GPS system signals 'loss of position' to the aircraft's automatic control system, meanwhile it sets about looking for return of the signal and then obtaining a new positional fix. Due to the nature of the GPS system, this may take some time, and the aircraft remains in ATTI mode while this is happening. This can often be quite long enough for the aircraft to drift out of sight.
As well as the loss of GPS reception, another component can trigger an automatic switch to ATTI mode, and that is a compass error. Despite what many think, a compass error does not usually occur because you flew near a hulking great lump of steel or iron, although if you got really, really close to it, that might happen. But if you were that close, you should be more concerned about hitting it. The compass error is more likely caused because when you took off on your flight you departed from an object that contained iron or steel. The most common suspect in this is concrete full of rebar, although some people think it is good to launch from the roof of a car (bad! Bad!).
Finally, there are several other errors that can cause the switch to ATTI, but they are relatively rare. Such as the mysterious 'Yaw Error' that is only really understood by Bigfoot, and also when a P4 decides that its dual compasses are in conflict with each other.
So, in summary, when you hear the box bitch yelling 'Warning, atti mode', take a look at your screen, as it should be displaying a warning as to what is causing the trouble. Whatever, stay calm and manually fly the aircraft back to you and land.
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