Siehe auch: AntriebsTheorie, Einsteigertipps

Flight time of MikroKopters

The flight time depends on the following factors:

• Lipo capacity
• weight including payload
• Motor/propeller combination
• losses (wind, hovering or sportive flying,...)

To estimate the theoretical flight times of the Mikrokopters, there are these possibilities:

• use the curves of the sets below
• use the calculation software
• calculate it manually

how to read the curves

The curves were made with a software too by marc.

They use measured motor/propeller data.

Flight time vs. Lipo capacity

Here we see the curve "Flight time vs. Lipo capacity" of a Quadro XL

On the lower scale we see Lipo capacity and on the upper scale we see the flight time.

If we want to find out, what flight time we can get with a 6600 Lipo, we need to do the following:

• find the 6600 on the lower scale
• now we go up until we reach the curve
• on the left scale we see the corresponding flight time (almost 34minutes)

The curves are calculated with realistic Lipo-weights. They consider that higher capacity means higher weight.

You can also see on that curve, that the maximum capacity is 14.000mAh. That is the point where the additional Lipos-weights are negative for the flight time.

Flight time vs. Payload

Additional payloads reduce the flight time of course.

There are three curves. They depend on the flight style.

Slow hovering results in the longest flight time, because of low losses.

So if we want to find out what flight time we can expect with 500g payload, we have to read the curves as follows:

• search the payload on the lower scale [g]
• go up until you reach the curve you expect 'hovering', 'normal' or 'sportive'
• go left to read the flight time

In this excample the flight time is between 13 and 20 minutes depending on the flight style.

Theoretical calculation of the flight time

If you want to calculate the theoretical value, you can do it that way:

measure the total weight including battery

Example on a Hexa with ~2150g

--> 1000g Empty weight plus 1150g Lipos

Devide the value by 6 (because six engines) --> 358g per engine

Thrust per engine = Total weight / Number of Engines

reading the current from the table

Now we determine the current that the engine needs to hoover (more exactly: Input current of the BL controller) This one uses this characteristic:

(This characteristic applies to ROXXY2827-35 and MK2832-35 (formerly known as MK2832/52) on a 4S Lipo)

In the courve you can see 2,5A for about 358g

Means: Each engine requires 2.5A, to lift his part of the total weight.

There is a total current of 2.5 A * 6 = 15A.

Calculate the maximum flight time using the battery charge capacity

The Hexakopter has been used in this example with two 5000mAh-Lipos.

The formula is:

t (in Hours) = Lipo-capacity / Total current

t = 10Ah / 15A = 0,666h

• The time in minutes is:

t = 60 * 10 / 15 = 40 minute

Power consumption and other losses

The above-determined value is an ideal value that specifies the absolute limit.

You'd have to really consider:

• The thrust characteristic was measured with a 100% loaded LiPo. The thrust decreases slightly when the voltage drops in flight.

• Turbulence
• Losses due to regulations
• other losses (e.g. in cables, etc.)

For this reasons we estimate ~10% losses

So you have:

t = 90% * 60 minute * Lipo-capacity / Total current

t = 0,9 * 60 * 10 / 15 = 36 minute

Test of the theory

This we wanted to test pratically. And here is the Video of the test.

Software tool for estimating the flight time

The calculation can be done very easily with a tool from Marc:

http://forum.mikrokopter.de/topic-21052-1.html

Test at a time-of-competition

With the software-tool we calculated the following graphs:

So for the Hexa2 we calculated a flying time of about 35 minutes and for the Hexa-XL 40 minutes

We were able to validate this in practice:

(Video)

Weights and flight times of the (standard) MikroKopters

MikroKopter as Quadro

• with
• 4 Motors Roxxy2827-35
• 48cm
• Navi-GPS-MK3Mag
• GPS-cap
• Flexlander-L Landing Gear

weight 640g without Lipo

maximum (arithmetical) Flight times:

L4-ME

MikroKopter as Quadro XL

• with
• 4 Motors MK3538
• 56cm
• Navi-GPS-MK3Mag
• Flexlander-XL Landing gear

Weight 970g without Lipo

maximum (arithmetical) Flight times:

QuadroXL

MikroKopter as Hexa / Hexa2

• with
• 6 Motors
• 56cm
• Navi-GPS-MK3Mag
• Flexlander-XL Landing Gear

weight 1000g without Lipo

maximum (arithmetical) Flight times:

Hexa2

MikroKopter as Hexa-XL

• with

• 6 Motors MK3538

• 56cm
• Navi-GPS-MK3Mag
• Hilander-26 Landing Gear

weight 1600g without Lipo

maximum (arithmetical) Flight times:

Characteristic curve of the engines here: MK3538

HexaXL

MikroKopter as Okto / Okto2

• with
• 8 Motors
• 77cm
• Navi-GPS-MK3Mag
• Flexlander-XL Landing Gear

weight 1260g without Lipo

maximum (arithmetical) Flight times:

Okto

MikroKopter as Okto XL

• with

• 8 Motors MK3538

• 95cm
• Navi-GPS-MK3Mag
• Hilander-26 Landin gear

weight 1830g without Lipo

maximum (arithmetical) Flight times:

Okto XL

Weight of 4S-Lipos

Weight of 3S-Lipos

Be careful, the speed curve must have been taken with 3S (the curve of 2827-34 does not apply here)

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