Forrest Frantz's Posts (2)

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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.

Read more…


1 hour 20 minutes - APM 2.5 takes the world record for Multi-Copter Duration of Flight powered by a rechargeable battery. [note: other records exist for hover]

Flight Requirements


To discriminate flight from hover:

o Fly the following land distance -

  - While flying at an elevation greater than 2.5 meters

  - Cover 2.5 kilometers of land or more using 50 or fewer GPS points

  - Where two or more of the way points are more than 250 meters apart

o Gain the following altitude -

  - Accumulate elevations gains of 250 meters

  - Consisting of individual continuous elevation gain runs of 25 meters or more

  - Where every one second period, the elevation gain is positive

o Lands within 50 meters of Launch (to even out the use of wind)

o Without using thermals or wind lift affect to gain lift (flat ground, etc).

o Generation of flight logs (GPS, time, and elevations)

o Certified or scientific method (full disclosure of the ship design)

Actual Flight


- Distance covered 2.551 km

- Min elevation 2.5 meters

- Ended at start (within 6.1 meters)

- A hundred waypoints with two waypoints 283 meters apart

- Two climbs of 126 meters and 112 meters with a total of continuous 25+ meter climbs of 515 meters.

- Flight over ground that was void of thermals and updrafts (level ground +/- 10 meters)

- Wind was none to slight

- Temperature was approximately -2C to 1C from start to end of flight

Record Established:  +1hr and 20 minutes (81.43 minutes)

Date:  November, 26 2013, 10AM

Flight Documentation:

Earth views of the flight:  This is the top view.  It's an important perspective for understanding the video.  The man-cave is the L shaped building at the bottom where the ship was brought up to the 2.5 floor window where the camera was located.  The camera is pointed north from the man-cave to the turn-around point of the second way point (top of earth view).  The third way-point was mid-left on the route back to the man-cave.


The south-west side profile of the flight.


Elevation profiles of the flight:  From Mission Planner, showing BarAlt R


Data imported to Excel and plotted.


Videos of the flight:  are compiled from 2754 time-stamped Canon stills taken every 2 seconds.  At a video rate of 20Hz, the videos are 40x actual speed.  Sometimes the copter goes outside the FOV of the camera (had to trade between showing detail and scene area).  The white box that is the most visible part of the copter is the thermal blanket on the battery.  If you lose track of the copter, watch where I am and the copter is usually 5 to 120 meters up.

Stage 0:  Shows the flight prep and takeoff location about 1/3rd the way between the mancave and way point 2.

Stage 1:  The octa

- is launched

- brought to the man-cave viewing window

- sent north on it's first slow 120 meter climb reaching the apex about .3km away

- reaches the second way point (near the lone fir tree at the end of the field)

- turn SE over the orchard fan towards way point three

- turns SW back towards the mancave

Stage 2:  The octa

- shows at the man-cave

- pauses near the launch site

- returns to way point 2

- returns to way point 3

- heads back to the man-cave

Stage 3: The octa

- shows back at the man-cave

- begins second 100+ meter climb

- returns to launch

- lands

- return copter to mancave

Note:  Suggestions would be appreciated on a camera system that:
- works for 2 hours at -5C without needing a battery change
- can take 2 hours of video without needing a card change
- can produce a video that can be condensed and shared
- can be worn on your head

Flight Logs:  See attached or

o 2013-11-26 11-41 187.kmz (earth view logs) real-time generated by APM

o 2013-11-26 11-41 187.log (gps and elevations) real-time generated by APM

o 2013-11-26 11-41 187.log.gpx

Certification:  Scientific method chosen where full disclosure of the ship architecture and flight conditions can be replicated. 

Multi-Copter Design

- Octa

- A novel rotor layout to demonstrate the flexibility of APM 2.5 (a regular quad is likely the most efficient for duration)

- A rotor layout that can be adapted for camera use (open front and rear)

- Thus, two connected side-by-side + oriented quads with 6 rotors up + 2 rotors down


Ship material list and weights were as follows:


ESCs are stripped of all insulation, painted with silicone, and put in the prop intake to cool.

The battery, 40 Panasonic Li-Ion combined into a 4S10P, had to be wrapped in PVDF foam (made prop clearance a bit fun; PVDF is a nontoxic fire certified foam) since it was -2C out (significant weight gain).  Even with the foam, the battery only produced about 80% of what it should in the summer.


Spot welded serial connection for the batteries.


Construction process: followed the blogs on carbon tube construction using braided carbon composite tubes, aerospace adhesive, and zip ties.  See following links.

Modification to APM Code:  APM is easily customize for any multi-copter rotor layout.  Documentation is available to explain the process.  The code below replaced the code for a V ("variant") octa.  The motors were numbered 1 to 8 going from left to right and then fore to aft.

        add_motor_raw(AP_MOTORS_MOT_1,  0.691, 0.522,  1.000, 1);
        add_motor_raw(AP_MOTORS_MOT_2, -0.691, 0.522, -1.000, 2);
        add_motor_raw(AP_MOTORS_MOT_3,  1.000, 0.000, -1.000, 3);
        add_motor_raw(AP_MOTORS_MOT_4,  0.382, 0.000, -1.000, 4);
        add_motor_raw(AP_MOTORS_MOT_5, -0.382, 0.000,  1.000, 5);
        add_motor_raw(AP_MOTORS_MOT_6, -1.000, 0.000,  1.000, 6);
        add_motor_raw(AP_MOTORS_MOT_7,  0.691,-0.522,  1.000, 7);
        add_motor_raw(AP_MOTORS_MOT_8, -0.691,-0.522, -1.000, 8);



o APM Development team

o Forrest Frantz (integration engineering, test, and pilot)

o James Frantz (electrical consulting and Scottsdale Foamie club)

o Leonard (math model)

o Hugues (motor suggestion)

o 3DR, T-Motor Company, Helibatics, SimonK, HobbyKing, Panasonic

o cptfrazz for setting such a high bar and use of Li-Ion

Purpose of the Record & the Challenge to Others

Please participate in the advancement of multi-copter technology by taking on the challenge of beating this world record. All that some of us ask is full disclosure of the ship so everyone can advance.  Multi-copters can be applied to many fields: inspection, conservation, and rescue to mention a few.  The faster we advance the technology, the more this amazing technology will be used, the more benefit society will accrue, and the more lives that will be saved. 

Read more…