It's official.  Guinness World Records validated the flight (see link under Flight 1).

Two flights were achieved to demonstrate that multi-rotor aircraft can stay in the air carrying a payload for a long period of time.  While 20 minute flights were considered long in 2014, these demonstration flights show that 1 hour flights can be the norm.  Imagine the increase in commercial applications when it is common for ships to stay in the air for an hour or more carrying different payloads.  It's just a matter of finding good rotors (Tiger), flight control electronics (3DR), batteries (Panasonic Li-Ion), ESCs, and removing unnecessary weight.  Once industry realizes the importance of performance, we will also see a jump in rotor and ESC net-lift efficiency (lift after it gets itself off the ground first).

Flight 1 – Guinness World Record for Longest Electric RC Multicopter Flight (Duration). Pending Guinness review.

  • Ship Name, Rufous
  • A hover that stays within view of the stationary video camera
  • 1 ½ hrs (97 minutes 23 seconds) on 8/21/2014 @ about 4 meters above open level ground (well above ground effect and without use of thermals or updrafts)
  • Hover, while not impressive nor useful, does require more energy than typical flight speeds and as such, a good first test.
  • Pixhawk Flight Log (Time, GPS, Altitude, Speed, Volts, Amps): Guinness Flight
  • Video of the Guinness record
  • Guinness Record Book

  • Time Lapse (GoPro) of the Guinness record.

  • Ship Secrets

Earth view of the hover breaking the world record.


The officials:  Michael Allen (expert in UAV flight control; Cloud Cap Technology), Brett Faike (UAV extraordinaire; teaches UAV tech at local schools; gave FPV demo after flight), Forrest (pilot in training), and Kirby Neumann-Rae (editor of the Hood River News).


Celebrating surpassing the old record of 80 minutes (ahhh ... hey pilot ... a little less champagne and eyes on the copter ... it's not time to prune the orchard yet!).  Bud, not shown, was taking photos.  Hope you got some champagne Bud!


Co-pilot, Dr Carie Frantz ... yes this amazing looking lass is single, is an unreal outdoor bad-ass, and has a great job in case you were wondering.  Thanks for keeping pops sane Carie.


Posting the final time (for the final application to Guinness, I requested that 4 seconds be taken off because some blades of grass were brushed prior to the ship finally giving up and setting down.  An interesting note on the battery:

o The Li-Ion batteries used are rechargeable (flight was on about the 8th recharge).

o Running Li-Ion batteries down to where the ship drops out of the sky does not hurt them if the ship mass and battery voltage is engineered to invoke that event before voltage runs down too low.

o A few days later, Flight 2 was made using the same battery pack with the ship carrying a camera (see Flight 2 next).

o Li-Ion are low C discharge (not 30 or 20 or 10 ... think about 1 C).  The chemical barrier will break down if amp draw is too high. This causes the ship to loose altitude.  And if there isn't enough altitude for the battery to recover, crash. As an example, using a 4S5P battery pack (about 15000mAh), Rufous hovers and flies at moderate speed at about 8 to 10 amps depending on payload and flight demand and does great even in moderate winds. Rufous has even flown 60 mph (97 kph) on the same Li-Ion battery pack. However, get up to 15+ amps turning a sharp high-speed corner and the battery chemical barrier locks up in about 2 seconds (yes I've had to rebuild a few times before I figured this out).  So caution.  Do the calculations.  Try to design a safe ship that stays in the air at 2x the amp usage at hover. 


Flight 2 – Performance demonstration flight (actual flight versus stationary while carrying a payloads)

  • Time aloft                                                                 goal of 1 ½ hr; so far 82.9 minutes
  • Distance traveled                                                       goal of 10 km; so far 14.4km (9 miles)
  • Elevation gain (cumulative)                                        goal 300 meters; so far 378 m (1242 ft)
  • Speed           (max)                                                   goal 18 m/s (40 mph); so far 9 m/s (20 mph)
  • Speed           (typical)                                                 so far 2.3 m/s (5 mph)
  • Payloads                                                                  GoPro Hero 3+ and 3DR Telemetry Module
  • Flight Log  (Time, GPS, Altitude, Speed, Volts, Amps)  Performance Flight
  • Video                                                                        coming soon

[note:  will try to beat 90 minutes carrying a camera when I get back from Sri Lanka]

Earth View showing the flight path of the performance demonstration over my orchard.

3689612811?profile=originalPhoto taken by Brett Faike, a local multi-copter flying legend, of the flight area (man-cave on left and princess palace on right).  He treated the witnesses of the Guinness record to FPV flights afterwards using two sets of goggles so we could "ride" along (keeping the ship within visual range and over my farm, of course).


Flight #2 (with camera and telemetry payloads), Elevation Profile.


Flight #2 (with camera and telemetry payloads), Watt Profile.


Flight #2 (with camera and telemetry payloads), Speed Profile.  The wind speeds were about 2 - 4 m/s from the north..


Flight Team

  • Design/Engineering                                 Forrest Frantz
  • EE/Flight Engineering                              Jim Frantz
  • Test                                                       Marty Frantz
  • Pilot                                                       Forrest Frantz
  • Copilot                                                   Carie Frantz


Acting Guinness Judges/Timers

  • KirbyKeumann-Rea             Hood River News                       Editor
  • Michael Allen                     Cloud Cap Technologies             Flight Control Software
  • Brett Faike                         Multi-Rotor Extraordinaire           Software Developer


Ship Summary:                                                                                1.65 kg (w/ camera & telemetry)

  • Frame                       Quad Carbon tube w/ open front for photography             62 g
  • Flight Controller         3DR Pixhawk + 3DR Power Module                               34 g
  • Motors                      T-Motor MN3508-29 380KV                                         328 g
  • Propellers                  T-Motor Carbon 16 x 5.4                                             116 g
  • ESC                          Afro 20A                                                                     31 g
  • Batteries                   Rechargeable Panasonic NCR18650B 4S5P                 930 g
  • Camera                    GoPRo Hero 3+                                                            76 g
  • Telemetry                 3DR Radio V2                                                               19 g
  • Wires & Misc           Long wires runs were magnetic wire                                54 g


Design Elements of Note

  • The electronics platform (EP) was eliminated to save weight (previous EP added 8 grams).  The battery doubled as the EP.  The flight controller (FC) was bonded directly to the battery, which was bonded directly to the frame.  The battery has a strong electro-magnetic field around it.  3DR deals with this issue by putting the sensitive elements, the GPS antenna and Magnometer, separate so it can be placed away from the battery.  In this case the GPS/Compass was bonded to the starboard-fore motor arm away from the battery.  This is a testimony to the excellent design of the FC as it did its job that close to a large battery.  Even though this worked, it is not recommended nor fully tested.
  • The ESC have their heat sinks removed.  To ensure cooling, the ESCs were placed directly under the tips of the propellers to get positive prop wash.  The loss in lift is much lower than the loss in weight.  To help protect from shorts, spray the ESC with electrical silicone.
  • Wiring in right sized.  The normal EE rule of 3% tolerated loss is put aside.  The rule is replaced by physics of electrical transmission.  A larger wire area cross-section  produces less heat that is measurable in watts.  And a larger wire area cross-section weighs more thus taking more watts to lift it.  Thus watt usage can be calculated for all wire sizes and thus optimized.  Some wire insulation is weak or can break down in sunlight.  Magnetic wire was used where possible.  But multi-wire strands are recommended to prevent wire breakage due to stress aging.
  • Li-Ion batteries are about 50% more efficient (watts hours/gram) than LiPo for multi-rotor flight.
  • Metal screws/nuts/washers replaced with nylon.  The only exception are the propeller screws which are aluminum.
  • Metal screws/nuts/washers and clamps replaced by bonded parts.
  • Gussets, screws/nuts/washers, and plates replaced by continuous masts and bonding.
  • Metal spacers replaced by short nylon spacers.
  • The most efficient propellers and motors were used – Tiger T-Motor.
  • Props and motors statically and then dynamically balanced.



Ship Performance:

  • Vibration Average Score               0.05 gs.
  • Stability Score:                            0.14 degrees.
  • Photography                                see test photos



Photo taken from tripod (baseline) with GoPro Hero 3+ at med 7m.


Photo taken from Rufous.  The camera was hard mounted, so now need to work on camera isolation that works.


Test Flight Highlights:  Prior to “Flight 1” the ship crashed three times. 

Crash 1 – Tried saving 2 grams by using Single Ply Carbon Skin Nomex core sandwich panels for motor mounts.  The Nomex core on one motor sheared causing a cascading event where all of the motors sheared.  Picture the ship moving away in an uncontrolled fashion with one motor suddenly floating away and quickly followed by the other three motors as the frame and battery kept flying in a deep descent.

Crash 2 – Really stupid piloting.  I cut power after a landing but forgot to disengage the motors (throttle lower left).  As I bent over the ship, my belly pressed the throttle to full and I got a face full.  Luckily wearing protective goggles and thick clothing.  Sometimes it takes a hard lesson to learn – always disengage the motors and the first thing one does when approaching the ship is to push the red button on the Pixhawk. 

Crash 3 – Had been suspicious of one motor mount bond (didn’t sand all surfaces on all the mounts).  The suspicions came true as one motor left the motor mast and the ship impaled itself into the lawn (photo below) after some high speed runs that loosened the faulty bond.  This crash broke one of the motor masts.  The motors are held on with nylon screws that are sized to shear off without harming the frame.  This works most of the time, but not this time.


Anyone interested in beating this record (the 100 minutes mark is itching to be broken), friend me and I'll gladly pass along what you need to do to satisfy Guinness.  I only ask that we are gentlemen and set records using engineering and piloting skill minimizing the use of ground lift (e.g., please avoid a hover off of a hot tar roof above a heated wall or on a side of a hill/ridge or in ground effect).  We want to show industry what is possible under normal flight conditions.  I also ask that you fully disclose your ship so we can all learn from what you achieved.  Thanks.

If you have any engineering questions, I'll will answer them below.

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  • MR60

    So you dropped the KV to something much less than 360?  Remember the number of windings (not that I want to try this)?

    Foxtech 5008 330KV has a 50 mm armature w/ 58 mm housing that might work for you.  But it could also use some machining on the much-to-heavy base and steel housing.  The 6mm axle also needs to be shortened along with the base.  Plus, unfortunately, there are 2 opposing set screws on the axle (the Chinese designers haven't figured that one out yet).  Oh well.

    Congrats again.  The rewinding was a major accomplishment, but must have made you feel really good when it flew for over 2 hours.

  • I find the RcTimer one of the (if not the one) most efficient motors freely available, considering Power/(Consumption*Weight) ratio. I would even go to 55 mm diameter for probably even more efficiency, but it's even harder development rather than just rewind the available motors.

    Regards rewinding - it was really a week of exausting evenings. After that I couldn't feel my touch balls. But after that the top thrust with 17x5 props (btw, theese are HK props) reduced from 3,5 kilo to 1,5 kilo and top current consumption from more than 15A to 8A on 6S cells. The wire used was 0,5mm enameled copper.

  • MR60

    Congrats ... time for me to relinquish the crown :-)

    It's interesting that you used RC Timer 5010 motors.  Was also going to look deeper into them to break the 2 to 3 hour level as I'd tested it earlier and the results were favorable.

    Can you point us in the right direction on the following details?

    - When you rewound the motors, same or different (wire size, number of windings, net effect of increasing or decreasing the KV)?

    - The prop manufacturer?

    Also like that you went with 6S versus 5S.  Runs a bit less efficient, but the ship can use more of the battery capacity.  Well done on that trade.

    Rewinding 8 motors ... you have moxy and guts!

    The rest I'll wait for your blog on details (frame, etc.).  Congrats again!

  • Hi Forrest!

    Thank for your appreciation!
    The copter is real, the flight is real, on youtube there are some part description, I just put it here once more:
    8 rotors 17x5 inch
    rewinded RcTimer 5010 motors
    LiIon battery 6S7P Panasonic NCR18650B cells
    KroozSD autopilot
    Custom developed 2 x 4ESC (SimonK based firmware)
    10mm carbon tubes concave frame

    Well, what I should say - making such a flight without a chair to sit on is really exausting.
    Also unlike the copter, not every camera and laptop can last for such long.
    Next days I'll try to prepare a blog post about the frame with some more photos.

    Best Regards,

  • MR60

    For those trying to set a duration record or finding ways to improve on the technology, the "122m 20s" video of a flight is a great example of what you need to do to document your flight for an open source community.

    What I liked:

    - People are trying to break the world duration record. This is how we improve the technology.

    - Open green field (no thermals) and flying mostly above ground effect.

    - OK video quality (a bit higher res would be perfect) along with a simple timer in the video view.

    - It's an octa versus a quad--a potential statement for duration craft if this is real.

    - It's concave versus flat--another potential statement for duration craft if this is real.

    - It's not a large battery for an octa--another potential statement for duration craft if this is real.

    - Lands at the same point of take-off (gutsy move to land on a box) so does not taking advantage of elevation loss.

    - It's in the air for 11 seconds before the clock is started (add that in)

    - If flies for a long time ... really cool.

    Suggestions for an open-source community (and or Guinness World Record):

    - A shadow that verifies the clock.  The shadow around the box is too small to discern and doesn't appear to move that much.  In two hours you will see a large change.  Fly near a tree or put a pole in the ground.  That makes the flight more convincing.

    - Close-up photos showing the ship batteries, propulsion system, and build.

    - Were the batteries rechargeable?  The baseline for a record is rechargeable.  Using non-rechargeable does not compare to that baseline.

    - Keep the ship in the screen (if it leaves view for a while that can cause doubt).  This can be difficult to do as you want a fairly close view of the ship flying but need to keep the ship in the view area.  In my videos, I shot from two angles and wish that I'd started one from a closeup (verifying what was part of the ship during the flight) and then after take-off widen the view and fix.

    - If the ship comes close to the ground (2 hours is a long time to keep the craft in one place), show that part of flight in regular speed so viewers can judge if it touches the ground.

    - In an open source community, share the details of the ship?

      ... motors/props/ESC

      ... batteries

      ... frame build

    I'm hoping that the 2-hour flight is real and not a trick (e.g., non-rechargeable batteries) and that the builder shares the build.  Doing so will save me about 8 months of work as I try for one more improvement to take rechargeable ships over the 2 to 3 hour mark.  With hope, I'm looking forward to more information.

    My suggestion to the author of the flight is WOW ... if this is real, please document and create a blog.

  • What do you think about this:

  • MR60

    Insightful and excellent in regard to the actual usable capacity of the battery.  Capacity of a given battery depends on:

    - Amp draw rate

    - Temperature of discharge

    - Temperature of charge

    - Watts required to keep the multi-copter in the air

    The only way that I know to estimate it is to charge the battery immediately after a flight and log it.  My logs show 14835 mAh immediately after the record flight.  What would have made it a higher capacity battery would have been to:

    - charge it at a higher temperature

    - fly when it was warmer

    - design the ship so that it didn't require as many watts so it could drain more of the battery more efficiently

  • Hi Forrest,

    I just finished reading through all of your articles/comment threads! As I've mentioned elsewhere, your articles and comments are incredible resources!!

    Just a quick question- I've read through everything twice and although its implied the battery used on Rufous had a capacity of 15000mAh, I couldn't find a place where you actually confirm that was the capacity used for the record. Was it a 15000mAh battery?


  • MR60

    I've crashed the Li-Ion many times, blown out ESCs, over done the C, and have yet to have a problem with the battery.  They don't flame out and they keep on taking a charge.  But I'm sure I will at some point in time.

    But, if you feel uncomfortable with Li-Ion and want to use Li-Mn, the read this to support you case.  It might be a good trade especially if you can't design your application to less than a 1C ship. 

  • I have a question regarding batteries:

    I'm relatively new to... well... everything drones, but I've been doing my best to read everything I can find and I've run into a question, that seems to be unanswered.  I've even dug through RCgroup and only found a few people responding to similar questions who, I think, may have misunderstood.

    Have you experimented with the new hybrid Li-Ion batteries?  Particularly the IMR type Li-Ion?  

    To give you an idea:

    ICR Li-Ion (What you use)

    NCR18650B 3400mah 44g 1C (4.8 A discharge max)

    (3.7V * 3.4A) / .044Kg = 286 W/Kg


    IMR Li-Ion

    Sony US18650NC1 2900mAh 2C~ (8A discharge max)

    (3.7V * 2.9A) / .044Kg = 243 W/Kg

    (Or even Sony VTC 5s with a 20A discharge max)

    Any opinion... or really anything at all would be a step forward for me.  I realize because of it's energy density it might not be the exact right battery for this exact application, but the IMRs are much more resilient and safe than ICRs.  However, these batteries are just miles ahead of a similar LiPo (150~W/Kg)... and yet I can find nothing about them in an R/C application.

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