Point of no return
- Thread starter Sarah
- Start date
Brains and experience. too many variables, weather, battery conditions, pilots actions controlling the copter etc.
The point of no return is simply the moment when the battery will not have enough energy to hold the device in the air.
It only takes a little wisdom to calculate your trip with the return plus a little margin.
After the only point of no return on the road can be a tree that grew too fast during the ride.
It only takes a little wisdom to calculate your trip with the return plus a little margin.
After the only point of no return on the road can be a tree that grew too fast during the ride.
You would of been given ample warning before there was insufficient battery to sustain flight, in that time you should of taken appropriate steps to prevent the copter falling out of the sky. Doesn't matter if a tree was there or not you can still crash into it with a new fresh battery, a RTH set to sufficient height and familiarity with your surroundings should help, there are many factors to calculate, and keeping an eye on the battery capacity is important just in case of a sudden change.
- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
Well i thought there was some kind of flight envelope diagram.
Like this:
wind S 20km/h stable, alt 1000m, temp 25°, If drone is north of RC, 100M AGL
(PNR = Point of no return)
Like this:
wind S 20km/h stable, alt 1000m, temp 25°, If drone is north of RC, 100M AGL
(PNR = Point of no return)
| Distance / remaining battery | 200m | 400m | 600m | 800m | 1000m |
| 80% | OK | OK | OK | OK | manual RTH |
| 60% | OK | OK | OK | manual RTH | over PNR |
| 40% | OK | OK | manual RTH | over PNR | |
| 30% (First alert) | OK | manual RTH | over PNR | ||
| 20% | manual RTH | over PNR | |||
| 15% (auto RTH) | Over PNR | ||||
| 5% (auto land) |
arruntus
Premium Pilot
- Joined
- Aug 19, 2017
- Messages
- 1,851
- Reaction score
- 730
It can make sense yes, because the wind is the biggest handicap we have with respect to consumption. I fly at a distance of 2000 m (to say something) and at 50% I turn around and I have enough battery, NOOOOO. This doesn't work, if the wind is up my *** on the way, on the way back I have it in front of me, that is consumption going much less than on the way back. This is a very clear case, but the side wind also has to be taken into account and is much more difficult to calculate, since we do the calculation by "hand".
Since we have to do this calculation every time we fly, it's a good habit to always keep it in mind, even if we know that we're not going to fly the whole battery. That training, the experience, is what will determine success or failure, and failure .... we know what it means ..........
- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
arruntus
Premium Pilot
- Joined
- Aug 19, 2017
- Messages
- 1,851
- Reaction score
- 730
Bearing in mind that I started when there was no telemetry, when you only fly with the timer of the transmitter. Flying close you learned the total battery time and then extrapolated it to the flight time. Later, we received the voltage thanks to the telemetry. There weren't that many percent, there was either total voltage or voltage per cell. In fact I still calculate it the same way and that's why I have asked many times that in the GUI we have the possibility to change between % of remaining battery and cell voltage. For cell voltage is easier.
I know that the fully charged battery is 4.2V per cell. I know that it is recommended to stop flying with 3.7V per cell (although I usually stretch to 3.5) and always remembering that under no circumstances can go below 3V per cell because it would kill the battery.
Maximum distance, coverage check or whatever you want to call it. I want to fly as far as possible, return and land with the minimum battery. As soon as I start to fly I take into account the altitude and the speed and direction of the wind. I know that this is what most penalizes the battery. I advance in one direction and if I have the wind against me, depending on the speed of the wind that slows the drone, I fly up to 60% and turn around. That margin, with experience, after having done many flights, you do mental calculations that are very close to reality, is increased a little if the wind increases (keep in mind that the wind, we can not predict many times in real time). When I land I know how much I have left and I know if I have fallen short and could have flown more or arrived too close. The next time I stretch the "PNR" or I shorten it.
In the same way you can do the same, without endangering the battery, making many trips back and forth but shorter. Calculate at what voltage the drone is going to land and see if with the current circumstances you have fallen short. It doesn't have to be specific with trips, it can be by recording trees, calculating distances between two objects, etc. You learn that if each drone is different, how much it consumes and each time you lengthen it more, little by little, until you get to land with the voltage you are looking for. I go from this tree to the wall starting with 3.95V and I have to go back and land with 3.82. I land with less than 3.82 and I know that next time I have to be more conservative, I land with more? I have fallen short. In the end it's very simple, it's based on repetition, training, experience, whatever you want to call it.
I don't know if I've explained myself well, I find it difficult to explain this and especially in English, but in the end it's a game within the flight. In the beginning you have to make the effort to remember to do it every flight and then leaves alone. Of course when you start it's better to stay short and reduce the margin of "unforeseen". Many times you arrive with more battery power than calculated, and you change it because it is not worth taking off again (this bothers me a lot, quite limited is the time of flight already). There comes a time when you calculate it quite accurately.
This is my method, somebody probably has a better one, I'm all ears
I know that the fully charged battery is 4.2V per cell. I know that it is recommended to stop flying with 3.7V per cell (although I usually stretch to 3.5) and always remembering that under no circumstances can go below 3V per cell because it would kill the battery.
Maximum distance, coverage check or whatever you want to call it. I want to fly as far as possible, return and land with the minimum battery. As soon as I start to fly I take into account the altitude and the speed and direction of the wind. I know that this is what most penalizes the battery. I advance in one direction and if I have the wind against me, depending on the speed of the wind that slows the drone, I fly up to 60% and turn around. That margin, with experience, after having done many flights, you do mental calculations that are very close to reality, is increased a little if the wind increases (keep in mind that the wind, we can not predict many times in real time). When I land I know how much I have left and I know if I have fallen short and could have flown more or arrived too close. The next time I stretch the "PNR" or I shorten it.
In the same way you can do the same, without endangering the battery, making many trips back and forth but shorter. Calculate at what voltage the drone is going to land and see if with the current circumstances you have fallen short. It doesn't have to be specific with trips, it can be by recording trees, calculating distances between two objects, etc. You learn that if each drone is different, how much it consumes and each time you lengthen it more, little by little, until you get to land with the voltage you are looking for. I go from this tree to the wall starting with 3.95V and I have to go back and land with 3.82. I land with less than 3.82 and I know that next time I have to be more conservative, I land with more? I have fallen short. In the end it's very simple, it's based on repetition, training, experience, whatever you want to call it.
I don't know if I've explained myself well, I find it difficult to explain this and especially in English, but in the end it's a game within the flight. In the beginning you have to make the effort to remember to do it every flight and then leaves alone. Of course when you start it's better to stay short and reduce the margin of "unforeseen". Many times you arrive with more battery power than calculated, and you change it because it is not worth taking off again (this bothers me a lot, quite limited is the time of flight already). There comes a time when you calculate it quite accurately.
This is my method, somebody probably has a better one, I'm all ears
The chart above is pretty close.
You can do slightly better with the wind in your face.
The one time I got the 2nd battery warning, was because I returned at 100m alt and did not descend as it approached.
I used up the last power on the long straight down descent. The battery died right at touch down.
Now I descend during the last 100-150m of the return flight.
You can do slightly better with the wind in your face.
The one time I got the 2nd battery warning, was because I returned at 100m alt and did not descend as it approached.
I used up the last power on the long straight down descent. The battery died right at touch down.
Now I descend during the last 100-150m of the return flight.
Isn't half the chart illegal in distance and height for most countries?
arruntus
Premium Pilot
- Joined
- Aug 19, 2017
- Messages
- 1,851
- Reaction score
- 730
With an observer you can fly up to 1000m. The observer is placed 500 m from the home and extends the distance "his" 500 m making the 1000 m.
Not in the UK, and not 1000m altitude. That's disappeared from the regulations. How's an observer going to help at that height? There are very strict rules to it and not many areas you can do it, especially as a hobbyist.
Last edited:
- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
Height at 100m AGL is (almost) everywhere legal, distance of 1000m away from helipad is possible in VLOS with proper authorizations, in Switzerland provided someone is watching in VLOS, pilot may fly in FPV. Not sure if VLOS is allowed with binoculars.
But the point of this post is that if you go to 1000m, you should immediately return home. (depending of course of wind, air density, air temp, battery quality and flight speed)
"But the point of this post is that if you go to 1000m, you should immediately return home. "
This statement is unfounded. If we keep a flight log correctly, we realize that we can go further in flight time and distance. But wisdom always tells me when it's time to go home.
For example a flight over the dunes over a distance of 3970 meters with a maximum distance of 1380m made me consume only 55% of battery. Start at 17.2 volts, return to 15.1 volts is 3.78 volts / cell which correspond to about 45% of remaining battery.
In these conditions, I could still go a little way to get the battery down to 30%. 15% more would have given me about 1080 extra meters.
Wind 15 km / h and constant speed (steady drive perso).
This statement is unfounded. If we keep a flight log correctly, we realize that we can go further in flight time and distance. But wisdom always tells me when it's time to go home.
For example a flight over the dunes over a distance of 3970 meters with a maximum distance of 1380m made me consume only 55% of battery. Start at 17.2 volts, return to 15.1 volts is 3.78 volts / cell which correspond to about 45% of remaining battery.
In these conditions, I could still go a little way to get the battery down to 30%. 15% more would have given me about 1080 extra meters.
Wind 15 km / h and constant speed (steady drive perso).
arruntus
Premium Pilot
- Joined
- Aug 19, 2017
- Messages
- 1,851
- Reaction score
- 730
The observer, who is a person, how do we put him 500 m high? ?????
Distance in horizontal, in addition we have to have clear that although we want, the H520 can only go up to 500 m of height because it is limited to that maximum height from the first day.
It depends on the regulations, the European regulations that are going to come into force throughout the European Community, supposedly next year, are going to collect these types of flight. VLOS, BVLOS, EVLOS, etc. But I'm afraid that in the UK, with the issue of leaving Europe will not affect you and in the UK will continue with your own rules.
I always talk about professional regulations because there are no regulations, at least in my country, for amateurs, there are restrictions, but not regulations, which I neither understand nor agree with.
- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
Ok then my above chart is wrong for your conditions ( anyways it is just a sample for the post's sake.)
Your weather conditions wind 15km/h, what direction, drone altitude, air temperature, ground level altitude ?
I suppose these must be optimum to have 55% at return from a 1380m away flight, like: at sea level, temp 30°C and flying first upwind, max height 20m...
Correct ?
Take off from the top of a big dune, so full visibility to the sea and no obstacle in sight.
I specify Antenna 2.4ghz 8Dbi and video 5.8ghz 10Dbi.
I think I could have pushed the H520 further, but you have to be good sometimes.
For me, it gives me an idea of the capabilities of the H520 and the "theoretical" limit of its possible range.
On the distance, I had no radio interference and no video cutoff.
I specify Antenna 2.4ghz 8Dbi and video 5.8ghz 10Dbi.
I think I could have pushed the H520 further, but you have to be good sometimes.
For me, it gives me an idea of the capabilities of the H520 and the "theoretical" limit of its possible range.
On the distance, I had no radio interference and no video cutoff.
- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
The question is PNR, which does not mean the furthest possible distance the H520 could fly, but if at a given distance pilot should start RTH or not.
Anyways thank you for data, it can fly well at sea level, 16°C small wind, optimum conditions indeed !
You can easily help yourself with radio telemetry. What I do.
Knowing that the battery can easily hold 25 minutes of flight (I did once 32 minutes with a return to 15%), I do not hold now on a battery time of 20 minutes which is less tiring battery. I prefer to use two batteries and keep them longer.
Telemetry gives everything on the screen. The flight time since the beginning, the distance traveled and the most important the distance between the ST16s and the H520.
Now if we fly for 15 minutes and the distance displayed is 4000 meters, we know that for the remaining 5 minutes, we can still do between 1300 and 1400 meters.
A glance at the radio, distance between radio and h520, if the measurement given is less than this remaining distance, we can return serenely and we know that we have a battery reserve of 5 minutes still behind.
I'm working like this and since 2015, I have never lost a device, or have had a RTH or have it engaged.
There is no scientific measure that will give you the moment of the NRP.
The only help is telemetry on condition of not losing it.
After, there is the habit, the feeling and the conditions of flight.
Knowing that the battery can easily hold 25 minutes of flight (I did once 32 minutes with a return to 15%), I do not hold now on a battery time of 20 minutes which is less tiring battery. I prefer to use two batteries and keep them longer.
Telemetry gives everything on the screen. The flight time since the beginning, the distance traveled and the most important the distance between the ST16s and the H520.
Now if we fly for 15 minutes and the distance displayed is 4000 meters, we know that for the remaining 5 minutes, we can still do between 1300 and 1400 meters.
A glance at the radio, distance between radio and h520, if the measurement given is less than this remaining distance, we can return serenely and we know that we have a battery reserve of 5 minutes still behind.
I'm working like this and since 2015, I have never lost a device, or have had a RTH or have it engaged.
There is no scientific measure that will give you the moment of the NRP.
The only help is telemetry on condition of not losing it.
After, there is the habit, the feeling and the conditions of flight.
