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Wednesday, June 21, 2017

Cheerson CX 20 Suddenly Can't Fly

  1. Drone weighted down during the throttle calibration process; no fear of a flyaway with that hunk of rusty tube threaded through the landing skids.
Calibration of the throttle completed and the rotors now throttle up normally but after the session we check and find that throttle calibration may be required at the beginning of each flight now. 


CX20 not lifting off Posted by Rob Nielsen on February 20, 2015 at 2:15pm in QuadcoptersView Discussions I just got my CX20 yesterday, I have been reading up on all the details and quirks so I was ready for it's arrival. I did a complete inspection of the interior components (ensuring I had disconnected the magnetometer in the mast). Everything is secure and in it's proper position. all solder connections seem sound. APM and GPS are in place and secure (they are mounting the GPS on the opposite side from the USB now). I reassembled everything and reconnected the Mag. Checked the propellers for balance. By this tiem the stock battery on the stock charger was completely charged. I updated the firmware and made sure it knew where home is in the Mission Planner software, as well as did a full calibration of accelerometers, Mag and transmitter. Propellers on their proper arms. All set to go. Ok time to fly. I take the unit outside. connect the battery, switch on the TX. The system binds as it should. Everything seems good. I have a solid green (Sats visible). I unlock the motors and try to take off. the moment the throttle leaves the full off position, the motors kick in at moderate revs, not enough for liftoff but flattening the grass. The unit leans forward so i pull back on the cyclic (right stick) to compensate. As i rev to max throttle, there is not difference in the RPM of the motors. At 0 throttle it is off, at 1% and up it is at a fast idle, not enough to take off. If i move the cyclic, i can rock it side to side and front to back, but it doesn't have the power to liftoff. similar to and ICE with the choke applied. I have gone through every permutation of the calibration routines from the incorrect factory ones to the ones used by people who fly this unit successfully many times over. I tried the all at once ESC calibration but this seems to not be the APM that works with that method. The only thing I can think of is doing a manual 'one at a time' ESC calibration but at this moment I am waiting for word back from the supplier. I have been waiting for a while for this to show up and now I am waiting with the thing right in front of me. it's pretty frustrating as you can imagine. Great weather and I can't fly it. FPV and telemetry gear on the way for it. ARG! If anyone has some good suggestions, i am VERY eager to try them. Flying the little Walkera and the Syma is getting old.

Suffice to say that I have been having this very same problem and I could not have explained it any better myself. It has been a very frustrating series of experiences that I have been having ever since I became risky soul  by updating firmware for my drone using the Mission Planner Graphic User Interface (GUI). Those sessions left my Cheerson CX 20 with Throttle settings of 200 when the default value is 1000, rendering it incapable of flight. Several flip-overs later the USB port has been damaged will no longer talk to my computer so you can imagine how excited I was to discover this YouTube video which carefully explained how to re-calibrate the drones throttles using only the controller (transmitter). In my case I didn't even have to remove the blades; I simply slipped a heavy length of steel through the landing skids and carried out the procedure exactly as explained in the video.

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Saturday, June 3, 2017

Vought V-173 “Flying Pancake”






Weird But Worked! Vought V-173 “Flying Pancake” Flying Pancake

The Vought V-173 “Flying Pancake” was an American experimental test aircraft designed by Charles H. Zimmerman and was built as part of the Vought XF5U “Flying Flapjack” World War II United States Navy fighter aircraft program. Both the V-173 and the XF5U featured an rather unorthodox “all-wing” design consisting of flat, somewhat disk-shaped bodies (hence the name) serving as the lifting surface. Two piston engines buried in the body drove propellers located on the leading edge at the wing tips.
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The original prototype, designated the V-173, was built of wood and canvas and featured a conventional, fully symmetrical aerofoil section. Designed as a “proof-of-concept” prototype, the initial configuration V-173 was built as a lightweight test model powered by two 80 hp Continental A-80 engines turning F4U Corsair propellers.
These were later replaced by a pair of specially modified 16 ft 6 in three-bladed units. A tall, fixed main undercarriage combined with a small tailwheel gave the aircraft a 22° “nose-high” angle.




Ground testing of the V-173, c. 1942
Ground testing of the V-173, c. 1942

The disc wing design featured a low aspect ratio that overcame the built-in disadvantages of induced drag created at the wingtips with the large propellers actively cancelling the drag-causing tip vortices.
The propellers were arranged to rotate in the opposite direction to the tip vortices, allowing the aircraft to fly with a much smaller wing area. The small wing provided high maneuverability with greater structural strength.
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In January 1942, the Bureau of Aeronautics requested a proposal for two prototype aircraft of an experimental version of the V-173, known as the VS-135.
The development version, the Vought XF5U-1, was a larger aircraft with all-metal construction and was almost five times heavier than the first prototype.




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Diagram of the complicated powertrain

The first flight of the V-173 was on 23 November 1942 with Vought Chief Test Pilot Boone Guyton at the controls. The aircraft’s most significant problem concerned its complicated gearbox that routed power from the engines to its two long propeller shafts.
The gearbox produced unacceptable amounts of vibration in ground testing, delaying the aircraft’s first test flight for months.




Edited NACA image of of a Vought V-173 ("Flying Flapjack") undergoing testing in a wind tunnel.
NACA image of a Vought V-173 (“Flying Flapjack”) undergoing testing in a wind tunnel.

Flight testing of the V-173 went on through 1942 and 1943 with 190 flights, resulting in reports of UFOs from surprised Connecticut locals.




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Maiden flight, 1942

Charles Lindbergh piloted the V-173 during this time and found it surprisingly easy to handle and exhibiting impressive low-speed capabilities.
On one occasion, the V-173 was forced to make an emergency landing on a beach. As the pilot made his final approach, he noticed two bathers directly in his path. The pilot locked the aircraft’s brakes on landing, causing the aircraft to flip over onto its back.
Remarkably, the airframe proved so strong that neither the plane nor the pilot sustained any significant damage.




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V-173 upside down on the beach

The developmental V-173 made its last flight 31 March 1947. In 131.8 hours of flying over 190 flights, Zimmerman’s theory of a near-vertical takeoff- and landing-capable fighter had been proven.
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The V-173 is now part of the Smithsonian collection at the Paul E. Garber Preservation, Restoration, and Storage Facility in Silver Hill, Maryland.
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It was restored at the Vought Aircraft plant in Grand Prairie, Texas, as of April 2012 it is on loan to the Frontiers of Flight Museum in Dallas, Texas.
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