Don't be deceived by calm wind

[Porto]

Maybe something like this. We could attach it to our MP, fly up and hover and check wind speed. Then we would know.

Long Range Wireless Wind Speed Meter | Scarlet Tech

Of course this is too big and I didn't search much but maybe there's something out here. Might be worth an invention opportunity.

Thanks for sharing and glad all ended well.

As Phlier wrote, Mavic has all the necessary equipment to show us wind direction and true airspeed. DJI should be able to incorporate those in the Go4.

Will I update my Go4 if DJI incorporated those info in its latest Go4? Probably not if it means I have to give up on Force FCC. I'd still rather do the usual flight precaution rather than having to lose FCC tx power.

 

[flightmike]

As Phlier wrote, Mavic has all the necessary equipment to show us wind direction and true airspeed. DJI should be able to incorporate those in the Go4.

Will I update my Go4 if DJI incorporated those info in its latest Go4? Probably not if it means I have to give up on Force FCC. I'd still rather do the usual flight precaution rather than having to lose FCC tx power.

Agree. That's why I thought an add on and non DJI.

 

[BigDuke6ixx]

As Phlier wrote, Mavic has all the necessary equipment to show us wind direction and true airspeed. DJI should be able to incorporate those in the Go4.

How can the Mavic measure airspeed? There's no pitot tube.

 

[Cut.Aussie]

The Mavic cannot measure wind speed or direction, it does not have the necessary hardware, it can ONLY estimate it. It can only calculate ground speed via GPS.

To calculate wind speed you have to have Pitot system and pressure sensor that is always facing direction of travel.

Wind speed is the the difference between airspeed and ground speed.

 

[Porto]

How can the Mavic measure airspeed? There's no pitot tube.

By estimating the ground speed and the motor power perhaps? I am not an engineer so I can't say much. In Sports Mode (with no parameter change), it will try to keep the Mavic at about 63kph. The motors will even only do 30% power if it has strong enough tailwind. I was thinking that by estimating the motor power output and the ground speed, the Mavic can estimate the wind speed?

 

[Big Fil]

By estimating the ground speed and the motor power perhaps? I am not an engineer so I can't say much. In Sports Mode (with no parameter change), it will try to keep the Mavic at about 63kph. The motors will even only do 30% power if it has strong enough tailwind. I was thinking that by estimating the motor power output and the ground speed, the Mavic can estimate the wind speed?

They could possibly provide a rough estimate but it'll never be accurate like a pilot tube. Reason being is that at different altitudes the amount of motor power will needed for a certain speed or even hover will be different at sea level as opposed to 10,000ft.

 

[BigDuke6ixx]

By estimating the ground speed and the motor power perhaps? I am not an engineer so I can't say much. In Sports Mode (with no parameter change), it will try to keep the Mavic at about 63kph. The motors will even only do 30% power if it has strong enough tailwind. I was thinking that by estimating the motor power output and the ground speed, the Mavic can estimate the wind speed?

In terms of airspeed, the only accurate way of measuring it is with a pitot system. Wind speed could be measured by letting the drone drift with the wind whereby the ground speed would equal the wind speed. Really you should know what the wind is doing anyway and airspeed isn't all that useful because our frame of reference is the ground and we don't have to worry about stalling.

 

[Phlier]

In terms of airspeed, the only accurate way of measuring it is with a pitot system. Wind speed could be measured by letting the drone drift with the wind whereby the ground speed would equal the wind speed. Really you should know what the wind is doing anyway and airspeed isn't all that useful because our frame of reference is the ground and we don't have to worry about stalling.

We're really "old school", you know that, BigDuke6ixx? And I'm not saying that like it's a *bad* thing. And of course, having a pitot/static system is a fantastic way of getting true airspeed, it isn't the only way. A simple look up table of drone tilt angle and motor speed will give you no wind ground speed, i.e., true airspeed. This would be dependent on the drone always flying as stock, as any configuration changes to weight, motors, props, add ons, etc. would nullify the lookup table values. But simple math of aircraft weight, thrust output at given rpms, and rotor plane angle will produce a performance chart look up table that would give accurate TAS values. Having TAS along with GPS gives all the goodies necessary to calculate accurate wind direction and velocity. Since the Mavic has a built in gyro that is capable of giving tilt angle, the only thing it needs is a lookup table. This would be pretty easy for some of the guys that are really into testing RC motors to create, as we'd need accurate thrust values for the motors across their power output range. Once that's obtained, all the other needed values for the math are cake. And the Mavic has a barometer in it to take care of the air density vs. prop rpm variable.

So yeah, the Mavic really does have all the necessary hardware in it to get us a pretty darn accurate TAS, it's just a matter of filling in a few holes in DJI's programming.

Every time I put up a post that disagrees with someone, I really feel bad about it... I don't want anyone to ever get the idea that I'm trying to start an argument with them, belittle them in anyway, or any other negative connotations. Nothing could be further from the truth. BigDuke, please don't feel like I'm trying to take you to task on this, my friend.

All of us old school pilots were brought up being taught that the only way you could get TAS was with a pitot/static system. Today's electronics and PFM have changed that a bit.

Happy flying, BigDuke6ixx!

 

[Gregp2016]

Hello, just to add one more tidbit of info, I found on occasion that my mavic would not get up to speed either. I found that turning off the obstacle avoidance would then allow the drone to get back up to speed. It seemed that possibility it was sensing maybe haze, the setting sun, etc, or something that caused it to activate. Once I turned it off the mavic when back up to 58kms no problem.
Just a thought.....

 

[Porto]

Hello, just to add one more tidbit of info, I found on occasion that my mavic would not get up to speed either. I found that turning off the obstacle avoidance would then allow the drone to get back up to speed. It seemed that possibility it was sensing maybe haze, the setting sun, etc, or something that caused it to activate. Once I turned it off the mavic when back up to 58kms no problem.
Just a thought.....

The reason is, with OA on the Mavic's tilt angle is 16 deg. With OA off the tilt angle is 25 deg (provided that you don't do parameter change).

If you fly low, I can understand that you may want to switch the OA on. But if you fly higher than anything surrounding the Mavic, it's better to switch it off. Having it on can lead to problem instead of benefit.

 

[BigDuke6ixx]

We're really "old school", you know that, BigDuke6ixx? And I'm not saying that like it's a *bad* thing. And of course, having a pitot/static system is a fantastic way of getting true airspeed, it isn't the only way. A simple look up table of drone tilt angle and motor speed will give you no wind ground speed, i.e., true airspeed. This would be dependent on the drone always flying as stock, as any configuration changes to weight, motors, props, add ons, etc. would nullify the lookup table values. But simple math of aircraft weight, thrust output at given rpms, and rotor plane angle will produce a performance chart look up table that would give accurate TAS values. Having TAS along with GPS gives all the goodies necessary to calculate accurate wind direction and velocity. Since the Mavic has a built in gyro that is capable of giving tilt angle, the only thing it needs is a lookup table. This would be pretty easy for some of the guys that are really into testing RC motors to create, as we'd need accurate thrust values for the motors across their power output range. Once that's obtained, all the other needed values for the math are cake. And the Mavic has a barometer in it to take care of the air density vs. prop rpm variable.

So yeah, the Mavic really does have all the necessary hardware in it to get us a pretty darn accurate TAS, it's just a matter of filling in a few holes in DJI's programming.

Every time I put up a post that disagrees with someone, I really feel bad about it... I don't want anyone to ever get the idea that I'm trying to start an argument with them, belittle them in anyway, or any other negative connotations. Nothing could be further from the truth. BigDuke, please don't feel like I'm trying to take you to task on this, my friend.

All of us old school pilots were brought up being taught that the only way you could get TAS was with a pitot/static system. Today's electronics and PFM have changed that a bit.

Happy flying, BigDuke6ixx!

Why do you want to know your airspeed?

 

[Phlier]

Why do you want to know your airspeed?

Having winds aloft information adds quite a few possibilities, including having the "you need to return home now" marker take into consideration the wind.

 

[BigDuke6ixx]

Having winds aloft information adds quite a few possibilities, including having the "you need to return home now" marker take into consideration the wind.

Well I never fly without due regard for the winds aloft. But why are people wanting airspeed?

 

[Phlier]

Well I never fly without due regard for the winds aloft. But why are people wanting airspeed?

Magnetic Heading, Magnetic Course, True Airspeed, and Ground Speed are needed to accurately calculate wind direction/velocity. That information can then be used to update the "return home now" information,etc, dynamically.

 

[oldcelt]

I'm new to the Mavic and based in the UK. Can you please tell be what UAV forecast is?
Also, what is "Safer Autoland"?
I wasn't aware that the tilt angle was shown on radar view as I have been flying with my iPhone 6S and with radar off because of screen space. I must try with my iPad Mini.

 

[CoolBreeze]

Haha English is not my first language, can't you tell?

Flying from the balcony, I can't get GPS to lock (edit: because of the roof). So, I have to fly it to an open space below my balcony to get GPS lock and to create a safe Home Point for RTH. So, the small plot of land is in front and below my balcony.

Usually if I still have enough battery remaining, I will simply hand catch the Mavic right at my balcony instead of let it actually land in the small plot of land below.

Thanks for sharing your story. Good reminder to always be vigilant.
I also launch/land from a deck. When landing on deck I fly in backwards to avoid front object sensing detecting wall. Not a fan of hand catching. I have same roof issue as you and on planned longer flights use yard as RTH point.
Glad your adrenaline flight turned out good.

 

[cderoche]

Porto, I had a very similar situation happen to me. The best thing we can do is remain calm, slow down that breathing which will slow down the heart rate. Which will then allow you to better think through what you need to do.

I flew out 3.6 miles with no apparent tail or cross winds but on RTH with around 60% battery left, and same as you with the OA turned off (except no tall buildings to worry about) I couldn't get more than 25-30 mph on the way back and can usually get almost 40mph. (mods) And you're correct, once that thing gets to 25% battery it drops faster. I had 1500ft left I believe and 10% critical forced landing kicked in. On my long distance flights I try to stay as low as possible and still get a signal, and once I RTH I try to drop lower and lower the whole way back as signal strength allows. Anyhow, I got home, with 0% battery left as I landed on my launch pad. I've got my contact info on mine just in case I have to visit a neighbor. After that 3 miles is my come back home max distance now.

My flight was largely over sugar cane fields and farm land in case anyone was wondering. With only the very last part over the neighborhood nearby.

 

[Kilrah]

How can the Mavic measure airspeed? There's no pitot tube.

All that's needed for an estimation is the the tilt angle which is obviously known and a calibration.

They could possibly provide a rough estimate but it'll never be accurate like a pilot tube. Reason being is that at different altitudes the amount of motor power will needed for a certain speed or even hover will be different at sea level as opposed to 10,000ft.

That could be factored in as well given altitude is known.

The Mavic already calculates wind direction and speed, they are in the detailed aircraft logs. Just not transmitted/displayed.

 

[Supercaliber]

Nice, adrenaline pumping flight! I swear that's the main reason I fly these things!

 

[Porto]

I'm new to the Mavic and based in the UK. Can you please tell be what UAV forecast is?
Also, what is "Safer Autoland"?
I wasn't aware that the tilt angle was shown on radar view as I have been flying with my iPhone 6S and with radar off because of screen space. I must try with my iPad Mini.

UAV Forecast is an app available for ios and android devices. It will provide you not only with current weather/satellite lock/cloud cover/etc.,but more importantly (for me) estimate of wind speed and gusts at various heights.

You can switch between radar and map view by clicking the small target sign on the top right of the map window. If we use a tablet instead of a phone, the radar is permanently displayed. However I prefer to fly Mavic with a phone instead of tablet as it keeps things compact.

As for Safer Auto Land, it refers to parameter changes that we are not allowed to discuss in this forum, especially the "how to" part. Please search for Digdat0 YouTube videos if you want to know more about the parameter changes.