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Sunday, May 31, 2009

Remote controlled flight

In my adventurous quest at being able to fly with my feet on the ground, I begin to understand the true fun of this hobby and how it stimulates the mind to understand the physics behind flight, and in the particular case of the helicopter how stable hovering and forward flight is possible.

Even though I have a flight stabilization unit onboard, I have diminuished its authority to almost zero so that most of the effort is left for the pilot behind the cyclic.

Flight simulator software greatly helps in ensuring that minimum training be taken before wrecking the real aircraft. It allows basic orientation skills and familiarization with the remote control to be achieved.

However, for full flying skills to be achieved, the simulator does not replace the real helicopter. Even the best simulator only offers a limited imitation of the behaviour of the real scenario. There are many more variables wich are very hard to simulate, and we find these in a real flight. Often a representation of our R/C model is not available, so we are forced to use a machine with closest similarity to our model. Sometimes it is no good enough.

Another aspect is the field of vision: in the simulation we are limited to a field of view of roughly 70º (depending on our distance to the screen, and its size and shape). In the real world, the field of view is of 180º (or more). So much more neck movement is necessary to keep track of the aircraft.

In the simulator there aren't many factors of distraction (unless you keep your IM client running in the background :)). In the real world there may be several elements of distraction, including people and animals (specially dogs).

Once the first steps of simulator training are completed (and we are comfortable with the transmitter, the control gymbals and orientation - make sure you can properly fly nose in and nose out without trouble), it is time for flying the real deal. A calm windless day and a place with a lot of space (more than 20 m x 20 m) and soft ground are essential for having the least ammount of surprises. At this stage training gear is essential if you don't want to break your blades all the time.

Safety cannot be disregarded and you must make sure there are no people walking around in your flying field. If you bring company along with you, make sure they are at least 10 feet behind you and stationary. It is never too much to remind that RC helicopter is the most dangerous model aircraft activity. Imagine these as airbourne lawn mowers. The spinning blades can easily chop off a finger or seriously cut a leg, not to mention the damage it can cause to the face.

While this blog post is not indented to be a exhaustive beginner manual for helicopter flight (you can find a lot of good documentation in the web regarding this), it is worth mentioning that the first training step is to achieve proper hovering skills. Do the best effort to maintain a steady position while hovering at one or two feet off the ground. When you first take off, you will notice the helicopter drifting to the left (or right in case of counter-clockwise rotating rotor head) even with the cyclic properly trimmed. This is the tail rotor propulsion, which is specially noticeable at low altitude. During takeoff you must compensate by applying some right cyclic.

The next move is the transition to forward flight. Here you must make sure you have a lot more available space, as you will easily achieve high speeds. In forward flight the helicopter behaviour is much more similar to that of an airplane. The cyclic behaves much closer to the ailerons and elevators of an airplane, and the anti-torque (or tail pitch) similarly to the rudder. While forward flight is somewhat easier, mistakes can however be much more costly. One aspect to consider is the distance: the further the helicopter is from the pilot, the harder it is to properly identify its attitude. Orientation mistakes become much more likely, so a lot of concentration is necessary to make sure the mistakes do not take place.

Here is a video I have taken with my onboard camera, showing some forward flight and a nice 60 feet climb: