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What to do in emergency situations

BlowMyTello

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Hello, I've had my first flight with my Tello that somewhat tested my drone's limits yesterday.

I lost wifi connection at 17.5 meters off the ground. Naturally I panicked and tried to run closer to the drone to reengage control over wifi. I didn't recall if I opened my iOS app settings or not to confirm it's still connected to the drone, memory was a little fuzzy for this moment :p

Looking up I saw VPS was probably not working and it began drifting away. It was later that day when I came home that I read the manual again and found the gem about it's failsafe protection of landing 50 seconds if lost contact.


1644124629410.png




Anyway, I thought VPS was still going to work since I was flying over a basketball court outdoors (somewhat windy). So it was just me helplessly looking up praying it wouldn't drift to a neighbor's roof. Emergency stop and killing the engine is not an option for me on the TelloFPV app since it's way too high.

It started going lower and lower for some unknown reason to me at the time and suddenly flipped at 2-3 meters above ground and slammed on the basketball cemented floor upside down. 3 propellers flew out from the force and I spent a good 15 minutes in the hot sun scouring the grass and floor for propellers. It still turned on fine and flew as usual after. Thank god.


It then dawned on me that I'm probably missing some critical information from the manuals, so went back home to check out the manual.

1644125197039.png
Say what? So the youtube videos of users flying their tello at 30 meters, 20 meters are all flying completely manual on windless days?





Then there is this gem too :

1644125053474.png
But how is that users can still fly their drones over water in some videos ?






So to clear and get more knowledge on what to do to save our drones from dying, we would need to react fast and do the right thing.

What could I do in situations when I lose my wifi connection to the drone and it was hovering/drifting over somewhere I can't recover if it crashed?

So far I've scoured the forums for the answer and found these :

Points gathered from other posts in this forum (credits to various members and especially VollaTello :
Absolute Limit : 22 km/h gust in 30 meters on tello forum, but I personally had issue at 17.5 meters (no wifi extender)

  • RTH only climbs to minimum RTH altitude, but never descends for RTH (only when at home, it descends to 1.5m or lands depending on settings).
  • Landed on a roof but at an angle? Motors would only spin if you press takeoff but never fly up. You can still start flying when tilted to some degree but its a well kept secret: One-button start doesn't work, but you can use the CSC (both sticks in & down, in other words, push thumbsticks diagonally down. Left stick goes down right and Right Stick goes down left) to start the motors and then immediately apply max throttle to take off.
  • There is no override for takeoff with low battery (if tello crash landed on a roof you can't reach but positioned at an angle) , the flight controller doesn't allow that.
  • Max speed of your drone is always relative air speed, never speed over ground.
    • Means: Tello can fly ~8m/s (~28km/h).
    • With wind of 5m/s (~20km/h) your Tello will achieve :
      • 13m/s (~48km/h) over ground flying downwind (=with the wind), but only ....
      • 3m/s (~8km/h) flying upwind (=against the wind).

        At windspeed of 8m/s it will barely be able to hold its position at full throttle - and beyond that it's gone with the wind (time for an emergency landing....).
  • Tip to fly in strong wind : With prop guards off, sport mode, max attitude angle Tello can with do fine in a pretty stiff breeze. Don't fly higher than you have to (wind gets much stronger up there) but stay above 1.5m as Tello reduces attitude angles below that ( some ingenious ill-conceived safety feature ).
  • Almost Fly Away over the trees. | DJI Tello Drone Forum (tellopilots.com) Be advised If you want to fly over the trees. VPS will failed, and Tello will drift away, make sure you set your home position, and quickly press home button when it says VPS failed.

Anything else we should know?
 
Last edited:

volate!lo

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A few comments:
* The last point won't work. Once VPS fails the current position is no longer available, which means TelloFpv can't perform RTH.

* Forget flying over water. If it works OK then it's pure luck, nothing else. The only thing to make it work consitently is to fly high enough over 100% flat calm water with lots of debris / dirt / plants. That way the water looks and behaves like a normal static bottom.

* The wind speeds are a bit optimistic. Don't forget that the wind at 30m altitude is MUCH stronger then at the surface.

* Even downwind tello rarely exceeds 8-9m/s because that is what sport mode is limited to in the firmware

* If Wifi is lost Tello will typically come down after 50s. If It also looses VPS (for example over a field of green gras) then it may drift, and start the autolanding sooner but the drift and autolanding is typically stopped once a clear bottom pattern is visible for the VPS camera.
 
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BlowMyTello

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great and life saving points 👍🏻👍🏻

I guess the reason why there was excited discussions about (how fast it would take to restart wifi extenders) in the other thread was
because the only way to re establish connection to the tello when a wifi connection loss happens would be to turn on and off our wifi extenders and phone’s wifi connection, correct?

This would have to be within 50 seconds if it loses connection over some tree branches at the edge of a lake, then bye bye tello 😐

Here in southeast asia tellos cost four to five times more so it’s much more painful to lose one.
 

volate!lo

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Normally the extender should automatically re-establish the wifi connection and the app will automatically reconnect within 2 or 3 seconds.

But some extenders are quicker / more reliable to reconnect than others.
 
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