1 hour 20 minutes
- APM 2.5 takes the world record for Multi-Copter Duration of Flight powered by a rechargeable battery. [note:  records also exist for hover that can occur indoors and take advantage of ground affect]

Flight Requirements:

- Distance > 1 kilometer

- Minimum elevation from ground the greater of 2 meters or two prop diameters (no ground affect)

- Lands within 50 meters of Launch

- Minimum of two way points > 0.25 km apart

- Altitude Climbs: Two climbs > 100 meters each

- Ends before voltage drops below recommended minimum level for recharging

- Flight over ground that does not vary more than + 20 meters in elevation

Actual Flight

- Distance: 1 - 2 km

- Min elevation 2 meters

- Ended at start

- Three way points with two 0.3 km apart

- Two climbs:  126 meters and 112 meters

- 13.06 volts left with 10 volt recommended minimum

- Ground + 10 meters

Time:  > 1hr and 20 minutes (81.43 minutes)


- Octa 2XQuad 6Up+2Dn (wanted to fly something novel that would show off the flexibility of APM 2.5)

- 3.18 kg AUW

- Li-Ion battery

Attached are the flight logs.  Later I'll provide:

o Video

o Earthview of flight

o Altitude gains

o Details of the copter (design and weights)

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Thank you for the excel file.

Send you a friend request.

It's working now.  Here is the file.  Only change what is in the purple cells.


Thanks Forrest,

Leave a comment on your page just now. Sorry for double post but below are some of the comment:

I'm planning to use the same motor MN3508 kv 380 with Li-ion 6s 18300 Mah batteries (2 x 3s in parallel). According to T-motor spec: with 15" prop it will generate 900 gram thrust and consume ~ 4 – 5 Amp.

My total AWG will be around 3.6Kg (will work more on lighter frame).

My questions if you may answer it:

  1. If the motor consume 5 A, is it safe to use this 18 awg cable on ESC to motor cable?
  2. Attach is calculate of flight time with formula ((Bat Capacity / Total Amp Consume)*60 Minutes) * 80% of battery capacity. Please advise on any miscalculation or others?

Many thanks in advance.


It will be slightly more efficient in net-lift when accounting for the additional frame weight required for the additoinal 1/2" or frame when using a 16" prop.  But 15" is fine.

Drawing 5 amps per motor at hover for 20amps total:  18 AWG is overkill but OK (optimal when drawing 1.5x hover).  20 AWG is optimal for wires between the power distribution and ESC and ESC to the motors between hover and normal flight speed.

Your ship duration calc:

- first see if you can decrease weight.

  ... save 20 grams and replace the PDB with a 3DR Power module and wire nuts.

  ... save 120 grams by bonding 1-ply x 1/8" carbon skin balsa core sandwich panels for the motor mounts

  ... save 210 grams by replacing the center plate with an engineered sandwich panel

 ...  save 90 grams by replacing the skid with pool noodle feet

 ...  save 54 grams by eliminating the 16mm clamp with aerospace adhesive


Remind me again.  Li-Ion or Li-Po?  If Li-Ion you need to engineer the C.  Li-Ion is about 1C. This is critical for a duration and distance calculation.

Your calculation accounts for:

- battery capacity

- amp rate

- % of the battery that can be used

That will result in a ballpark number.  So not bad.  But if you want to really nail it, you need to calculate:

- actual ship amp rate at speed and hover (using individual motor usage x 4 is not that accurate as the ship will not be 100% efficient; more like 90% efficient as the motors fight one another to maintain balance)

- the voltage drop of the battery when under load

- the resulting amp increase since volts x amps must equal watts

- the watt decrease through time since the ship becomes more efficient (takes slightly fewer watts to fly) as voltage drops

- the change in volts of the battery through discharge time and the proportional impact on amps through discharge time

- the non-linear drop in volts through discharge time as you approach the end (80% is only a guess)

 But your approach will give you the ballpark.  Well done.

Thanks for going through my calculation.

I manage to save some grams by replacing the CF round tube and clamp into aluminium square tube with inner ribs for more rigidity (hopefully). So no clamps and motor mount needed, just add nuts to lift the motor because the shaft is pressing to the tube:

Will try to cut the center plate weight also but playing with balsa perhaps not suitable for me right now, but what do you mean with "engineered sandwich panel"?

For the skid, will definitely try the pool noodle feet.

For the battery, I will use 2 unit Li-Ion battery in parallel from rangevideo.com link.

I assume it will generate 1C x 18.3A = 18.3A, my target hover will be 20A. Slightly over but the battery spec said it can deliver max 2C = 36.6A so not worried on that.

I will try to monitor the real amp consume when this bird is flying to get the real calculation on several condition (hover, fly, fly with wind, etc).

Interested to know, are you saying that forward flying will eventually more efficient than hover from your statement below: 

"- the watt decrease through time since the ship becomes more efficient (takes slightly fewer watts to fly) as voltage drops"

I'm using 80% battery capacity on the flight time calculation and using only 75% of flight time to estimate the travel distance assuming that forward flight will consume more Amp compare to hover.. CMIIW.. and also add ~ 15% from the published amp consumption from tiger motor website. 

Finally, just hopping that Tiger Motor is not lying on their motor amp consumption because all of this was based on their spec alone.

Anyone has calculation based on an experience with this motor real consumption?


- I'm planning to speed up to 15 m/s for flight mission, do you think the quad will be able to handle such speed?

- I will try this ESC Sunrise BLHELI Multi Series 20A 2-6S (include wires) to cut more weight, hopefully it will work with low rpm motor. What ESC do you use on the world record quad ?

Thanks again for your time to response this.. :)

Try to achieve about 0.6 C or so at hove.  Then you will have adequate margin for flying in difficult situations.

This is easy to achieve if you keep cutting weight.  For example,

- the metal screws would be best replace by nylon 4/40 screws from 


These will shear off before damage is done to the props, motors, and ESC.

- cut a hole in the Al arm under the motor for the motor axle and cotter pin

Go crazy on weight removal.  Rufous for example has all of the covers to electronic components removed.  For a commercial ship this is not advised, but then again neither are Aluminum arms.  so maybe consider this ship as a test platform and get the weight down so it flies at a lower C.  Then you can go to carbon arms and put the covers back on.

Do not use balsa wood for the motor mounts or anything else.  A sandwich panel has one ply of carbon on the top and bottom side of a balsa, Nomex, or cork core. Since you are currently using Al square tubes, you don't need sandwich panel motor mounts.  It would just add weight.

The ESC I used should be identified on the blog.

Keep me in touch with how this goes and the C that you are finally flying.  

Flight behavior:

- As the voltage drops, the watts to keep the ship in the air slightly decreases.

- But as voltage drops, the amps increase almost proportional to the V drop.

- As you transition from hover to moderate speed, the watts required to fly decrease.

- As you transition to fast speed, the watts required to fly will greatly increase to more than the watts to hover. 

Thanks for the nylon screws tips, first I think you must be crazy to use Nylon screws on Rufous but will try to find it locally since shipping from US to here will be tremendously expensive.

Since this quad were indeed to be "semi"-commercial so will stick on several gimmick part while still (as you said) go crazy with weight removal on i.e. center plate and landing skid.

Will keep posting the progress since I still waiting for several parts to arrive.

Hello guys,

I'm enjoying following your conversation. I provide you hereunder with an excel calc sheet from "EndofDays", which works really well to estimate your flight duration. The only parameter that you will not know before your first flight is "efficiency". After a first flight, in a given config, you will be able to calculate this parameter for your particular motor/prop/esc combo.

Once you have it, you can then use the calc sheet to calculate your flight duration by changing the AUW and/or battery capacity.

I also provide you with a blog I did a long time ago to explain how to make your balsa/CF sandwich panel, if it may be useful:





Hi Hugues,

I'm enjoying it also :)

Thanks for the excel file, may I know are you referring to the same motor (MN3508 KV380) on the efficiency and all calculation in the excel file?

Hi, this excel sheet is independent of the model/brand of your motors. The efficiency parameter (that you can set at any value) will "integrate" the actual equipment you use. At first you do not know what is the correct value of "efficiency" for your setup. This is why you have to make a first real flight and measure your flight duration; then you enter your setup on one of the lines of this excel sheet; you will get a wrong flight duration value; you then modify the efficiency cell until the flight duration matches with your measurement. You then have the efficiency value you can use for your motors/ESC you are using.

Using nylon screws works great attaching the motor to the motor firewall on the boom.  The prop however must be attached with AL screws or better and thread locked or you will have a prop motor separation.  

With a prop separation, the quad will never maintain level attitude with a power failure and severe frame damage will surely result.  If you can keep the motors and CF props on these endurance ships, and with a power failure of one motor, I've found that it maintains a level attitude during descent landing flat usually with little damage. The point is not to get too aggressive at saving weight at the prop to motor attach point.  I've never had a failure with four 5mm nylon screws motor to firewall lightly torqued.  In fact they have saved the CF props from damage on many occasions sheering at the right time.

The above comments are based upon experience over several controlled test flight crashes a few of which are available in the Don't Fly Like My Brother Wiki videos. 

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