Baron’s Hobbies – Online Hobby Magazine

First Person Video Helicopter Flying

Posted on June 13, 2009 by aaronredbaron

First Person Video (FPV) flying has captured my fascination recently, and after my fixed wing experience with the Multiplex Twinstar came to an abrupt end, I decided it was time to step up to an FPV Helicopter. Flying by video with an airplane is challenging in a large part because the airplane is moving relatively fast, and maintaining your perspective can be tough. My thought was if I could set up a helicopter to have enough stability, I would be able to fly the model around with more control, slower, and have an easier time keeping my perspective. I fully expected hovering the helicopter to be the biggest challenge, so I enlisted the help of a stability device, the Captron Helicommand 3D.

Picking A Helicopter

For my FPV heli experiment, my trusty MSH Protos was chosen.  The Protos was picked for its light weight and precise controls, but I previously had the model set up very aggressive for 3D flying. I began with some simple changes to the rotor head; the paddle weights were reinstalled, and the Bell input was moved out on the Bell/Hiller mixing arm. The helicopter had been using a 6s 2600 mAh LiPo battery with a 15 tooth pinion to deliver wild power, but flight times were limited to 4 and half minutes. With an 18 tooth pinion and a 4s 4000 mAh LiPo, the headspeed is reduced and the flight time is increased by more than double ; taming the Protos and bringing the temps down on the motor at the same time. I installed and set up the Helicommand 3D and removed the tail gyro I had been using. This device is a 3 axis gyro system which takes care of the gyro for the tail, and also adds a gyro for each axis of the cyclic. Further improving its usefulness for FPV, the Helicommand is able to hold the model’s position (not altitude) within 2-3 meters of the ground. With the Helicommand’s help, it is practical to fly a heli by the video link close the ground; you only have to worry about the altitude once you have the system figured out.

Adding The Gizmos

Adding an On Screen Display(OSD) is a solution which provides helpful information in keeping the model close and safe. Battery data is provided, effectively giving the pilot a “fuel gauge.” A compass heading, return to home indicator, speed (actually ground speed), and altitude help the pilot keep perspective on where the model is in space.  To fly safely, the model must be kept within the practical operating range when operated by normal visual contact. If there is a problem, you must be able to safely bring the model back without the video link. The OSD also provides a line of sight and ground distance from the home position to the model, helping the pilot keep the model in close proximity. All of the instruments on my OSD, the RVOSD from range video, are GPS based, thus my altitude and speed readings are less accurate than a system which uses a pitot tube and static pressure sensor to get an accurate airspeed and alititude reading.

Where Is All Of This Going To Fit?

With all of my equipment figured out and removed from the carcass of the Twinstar, I needed a way to make room for the extra equipment on the little Protos. I chose to build a plywood tray with supports to mount it to the bottom of the frame. I was able to bolt the FPV tray to the frame where the landing gear normally mount, and then over sized Logo 600 landing gear were mounted on the bottom of the FPV tray. With the battery slung between the landing gear to lower the CG and thus further improve stability, I had room for the camera to mount on the battery tray. The tray worked out perfectly and provides room for my RVOSD, current sensor, a 3 cell 910mAh pack for the FPV goodies, and the video transmitter. A 6 line phone cable was sacrificed to make an extension cable for the GPS receiver. I chose  to mount it on the tail to give it a view of the sky clear of the carbon fiber rotor blades.

Success!

Everything worked out better than I could have hoped for on the FPV Protos, and my flying while on the video link has improved dramatically in the half a dozen flights I have flown. I now feel capable of flying the helicopter entirely by the video link, and I am excited to explore my system’s capabilities. Hovering is harder than anything else, and the Helicommand has proved to be indispensable. It is very difficult to judge altitude and decent rate; perhaps a different OSD system which uses a static pressure sensor and a better camera will improve these issues. The return to home indicator and compass are helpful, but they only work properly when the helicopter is flying forward. If it is moving backward or sideways in a hover, the compass and return to home indicator won’t point the right direction. It is important to keep the model within close operating range, such that it can be flown back without the video link by yourself or your spotter. Flying an FPV helicopter is remarkably challenging, but for experienced model helicopter pilots, it is possible to build a small, simple model with the features necessary for success time and time again.