Hover time aloft vs. flying time aloft. Why is hover time shorter?

[KI5RLL]

Hello,

Now that I finally am on a great forum with actual competent Mavic pilots and many very smart communicative people I see, I would like to read some new “why“ answers to this.
Yes I already have heard a couple explanations but on a new forum now, why does my Mavic Air 2 (before) and now my Mavic 3 fly for more minutes of battery time moving forward than only when it is just floating in position? I usually fly long distances and hold cruise around 30mph. But setting it at hover will draw down a battery faster than forward flight. Why is this?

 

[Rich QR]

It's the same with any rotorcraft. When in hover, the rotors are entirely in "dirty" air that is being pushed down by the rotors. When moving, at least part of the rotor is in "clean", undisturbed air that isn't already moving downward.

 

[kodiak]

The very short answer is translational lift. An important aerodynamic principle and entire books have been written about it. In a nutshell, when an airfoil is in forward flight it provides a slightly additional amount of lift thereby increasing efficiency. Hence slightly improved battery life in forward flight relative to a hover.

 

[AZDave]

Hello,

Now that I finally am on a great forum with actual competent Mavic pilots and many very smart communicative people I see, I would like to read some new “why“ answers to this.
Yes I already have heard a couple explanations but on a new forum now, why does my Mavic Air 2 (before) and now my Mavic 3 fly for more minutes of battery time moving forward than only when it is just floating in position? I usually fly long distances and hold cruise around 30mph. But setting it at hover will draw down a battery faster than forward flight. Why is this?

What is the percentage difference that you are seeing? I notice that you are a ham radio operator and I've sometimes wondered how long I could keep a vertical wire antenna in the air using my Mavic Air 2.

 

[Elthree]

I've always found it subtly amusing how DJI's description of the conditions for their "Max Hovering Time (no wind)" includes things like "constant flight speed of 32.4 kph". Well, is it hovering or is it not?

One would assume that hovering in a constant breeze would not harm the efficiency.

 

[Meta4]

I've always found it subtly amusing how DJI's description of the conditions for their "Max Hovering Time (no wind)" includes things like "constant flight speed of 32.4 kph". Well, is it hovering or is it not?

DJI put the asterisk on the wrong line.
The constant flight speed obviously belongs to Max Flight Time

One would assume that hovering in a constant breeze would not harm the efficiency.

To hold position in a constant breeze means the drone has to work harder than it would in still air.

 

[Elthree]

DJI put the asterisk on the wrong line.
The constant flight speed obviously belongs to Max Flight Time

That does make more sense.

To hold position in a constant breeze means the drone has to work harder than it would in still air.

Given the discussion above that forward motion is less work than hovering, what's the difference between moving forward over the ground, and "moving forward" in order to maintain position?

 

[cameracamel]

OK...... On the lighter side, Seeing we are talking about air, I have a question. Why do people only vanish into THIN air? You NEVER hear about people vanishing into thick air at sea level.....?

 

[Elthree]

OK...... On the lighter side, Seeing we are talking about air, I have a question. Why do people only vanish into THIN air? You NEVER hear about people vanishing into thick air at sea level.....?

Are you saying those are the ones we never hear about?

 

[KI5RLL]

What is the percentage difference that you are seeing? I notice that you are a ham radio operator and I've sometimes wondered how long I could keep a vertical wire antenna in the air using my Mavic Air 2.

—Radio—
Yes I am an FCC Element III radio operator, General Class. Plus I have other radio licenses also.
Not sure I understand what you are asking or wondering. Keeping a vertical antenna on your MA2. Yes vertical polarity is best propagation if transmitting or receiving if the controller/receiver is also vertical polarity.
Radio propagation is best when transmit and receive antenna are both same polarity (orientation). One horizontal and one vertical reduces propagation a great amount.
Is this for the actual MA2 itself? Consider that antenna length is a known formula calculation depending on frequency used. The frequency calculates the antenna length. Too long or too short an antenna for the freq. used can damage or kill the circuitry of the transmitter. It will reduce propagation and will cause very many problems.
That is a big part of radio study and exams.
Is a simple formula to calculate antenna length when you know the frequency used. Same for using a Yagi Uda. The math and science is well known and established.
If you want that math please let me know. If using a secondary antenna for a separate purpose yes you can calculate and make a proper antenna for that.
—Hover vs Flight—
I did not calculate a percentage as it always changes of course, but other pilots have kept some good metrics on it yes. And DJI mentions it (mentioned in thread by others here). Has been a topic of discussion on other forums for a while. I do understand still the cause but wanted to hear some smarter people here explain it. And list a few other causes.
Why?
I generally fly very long distances per flight (not radio long range but miles flown takeoff to landing.) I may hold a world record on the Mavic Air 2. No one on any forum has beat it. I still solicit a challenge but no takers.
So I am always learning and squeezing out more feet and miles for max distance flown. I made a long list of things to increase total miles flown.

 

[Lets Fly]

OK...... On the lighter side, Seeing we are talking about air, I have a question. Why do people only vanish into THIN air? You NEVER hear about people vanishing into thick air at sea level.....?

It's so much easier to vanish into thin air, in thick air you just can't move fast enough, but imagine have fast you could vanish in space.

 

[Drbobk]

DJI put the asterisk on the wrong line.
The constant flight speed obviously belongs to Max Flight Time

To hold position in a constant breeze means the drone has to work harder than it would in still air.

Why is holding position in a breeze different than flying forward at that same speed in still air?

 

[KI5RLL]

Why is holding position in a breeze different than flying forward at that same speed in still air?

Is it?
A hypothesis to make a theory to prove or disprove. Hmmm. Pretty easy to set up the conditions and see. Good assignment for someone.

 

[Lets Fly]

Why is holding position in a breeze different than flying forward at that same speed in still air?

Flying forward should make no difference.

 

[mobilehomer]

Just watch a video of a drone hovering. Then watch it flying forward.

 

[AZDave]

Just watch a video of a drone hovering. Then watch it flying forward.

If there is a steady breeze it's going to look the same hovering as if it was flying forward in calm air.

 

[mobilehomer]

If there is a steady breeze it's going to look the same hovering as if it was flying forward in calm air.

Nope. It will bounce around. Try it.

 

[AZDave]

Nope. It will bounce around. Try it.

Then it isn't a steady breeze. It's basic physics. If there is a steady breeze while hovering at the same wind speed as the drone would experience when flying, the drone would respond exactly the same. "Fresh air" in both cases. If you think otherwise, you should probably come up with some sort of explanation for why.

In practice, a breeze is almost never steady ... i.e., laminar flow and constant speed. Neither is "calm" air. You can visually discern "bouncing" much easier when the drone is in the same place than when it is moving.

 

[FLDave]

Nope. It will bounce around. Try it.

If it's bouncing then it's not a steady breeze.

 

[Meta4]

Given the discussion above that forward motion is less work than hovering, what's the difference between moving forward over the ground, and "moving forward" in order to maintain position?

The wording in the specs gives a clue.
For the Mavic 3, DJI say:

Max Flight Time (no wind) 46 minutes *
Max Hovering Time (no wind) 40 minutes *

* The flight time was measured in a controlled test environment. Specific test conditions are as follows: No wind, at sea level, constant flight speed of 32.4 kph, APAS off, AirSense off, camera parameters set to 1080p/24fps, video mode off, and flying from 100% battery to 0% battery. Results may vary depending on environment, usage scenario, and firmware version.

Perhaps if you could test in an environment with a steady, constant wind of 32.4 kph for 46 minutes you might get similar results.
But to properly achieve the testing conditions would be close to impossible.

But DJI was giving useful information to help gauge performance.
ie. Max hovering time vs max flying time.