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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  • Hi Forrest,

    Should I be worried about the li-ion lock-up when I only fly mission for mapping (no manual)?

  • MR60

    A note on Li-Ion Battery lock-up (exceeding the C rating) discussed in the blog just above the photo of the time keeping board.  The record was set using the same battery pack that had locked up twice before due to me being a bad pilot (doing high-g corners during test).  So lock-up doesn't seem to hurt these batteries as long as exceeding the C rating doesn't last long (the ship moderately descends out of the sky and crashes so it's not exceeding the C very long).

  • Thanks for letting me fly Rufous!!

    How did I get to fly Rufous? ... a quick background story - I am a software dev that became obsessed with multirotors a couple of years ago.  I started a small company called Hoverlabs in an effort to get multirotors into the middle school and high school classroom as a teaching tool since my obsession has taught me so much about math, enginerding, fabrication, computer science, physics, failure, and all that other good stuff.  The little reputation I've built for myself in the community got me an invitation to 'watch some guy fly a quadcopter' .... you can imagine my surprise when I showed up to watch Forrest (not just some guy) break the world record for longest flight time.  The efforts behind building Rufous are spectacular.... Forrest should sell tickets for tours of his man cave and experience the science behind the build.

    So, during a random visit to Forrest's man cave I got to take Rufous for a spin.  I've got to say that it doesn't quite fly like I expected.  I thought that it would be sluggish with batteries providing power at such a low discharge rate and with 16" props spinning rather slowly.  To my surprise it was amazingly nimble.  I suspect that the weight is a factor in it flying so well and of course the countless hours of balancing in the build.

    In summary, Rufous isn't just a world record breaking machine.  It's a totally capable quad that is fun to fly and I'm sure it has a place as a commercial vehicle.  Hats off to the Pixhawk for demonstrating a perfect loiter for an hour and a half.

  • 100KM

    Congrats Forrest.  Thanks for the great write up and open sharing of information.

    Frederic, I've also heard of these as shrouded propellers- again to distinguish from small, fast spinning ducted fans.  Thanks for the graphics.  Would you know if a slight expansion of the fairing exit diameter was tested for further thrust enhancement?  (only slight expansion to avoid separation)  An exhaust diffuser should trade velocity for pressure.  Of course all of this additional geometry needs to yield a net increase in thrust after accounting for the added weight.  Your numbers indicate it may be well worth it for a mostly hovering application.

  • Of course a link to this remarkable blog post belongs on the Testing UAV and UAS performance page. :-)

  • MR60

    Almost there.  Just did a flight with a GoPro and telemetry payload.  Close enough to 1 1/2 hours to know it's achievable (7 minutes short).

    Pretty funny start and ending.  At the start I got confused on direction after a few minutes of flight and had to set back down (so there went 3.5 minutes).  At the end, the main battery bullet connector popped loose, causing a premature landing (unknown how many minutes lost there).  Fortunately was getting prepped for landing and was over grass so the ship was undamaged. Glad it didn't happen at the mode altitude of the flight--50 meters.

    Will post a video of the hilarious start and end.  And also learned how not to mount a video camera (on floppy foam).

  • thanks for the link to translational lift. I will definitely try to understand where it comes from as it is not really intuitive

    for the fairing around the propeller ( I prefer that terminology because ducted fan triggers images of what we use in models of jets which is very different ) here is the result of a study that somebody in my airplane design club did to look at optimization of a full scale paraglider with an engine. the power of the engine is 1500W and the propeller is 40" diameter. the length of the fairing is around half the diameter of the propeller

    if you are hovering there is no translation 


    the propeller generates 10daN of thrust but the fairing generates a resulting lift of 24 daN. the problem with that is that as soon as there is translation the effect decreases very fast while the drag increases so it may even become an adverse effect. this is why it is not a good idea for a general purpose machine ( so that was not considered as a solution for the paraglider study )


    but here you are trying to do a record breaking machine that is just hovering so you are in the best case scenario. you can keep the large propellers for efficiency and just add the fairings to increase the actual total lift for a given power consumption

  • Hello brother, Pls post your parameters file and full telemetry log.

  • MR60

    Translational lift.  Thanks.  And I too believe your are correct that it also exists for multicopters.  Will try to determine if the speed range also holds true for our little guys or if something like Air-Speed / RPM is the actual constant across platforms.

  • 300km

    Hi Forrest, in a traditional helicopter it's called translational lift. I'm sure the same thing happens in multi rotors.

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