Flight Controls
A pilot uses three controls to fly a helicopter:
the collective, the cyclic and
the pedals. The collective controls the magnitude of the thrust-vector generated by
the rotor disc. It thus controls the amount of lift. The collective is a lever
which is operated by the pilot's left hand. When the collective is pulled up, the
rotordisc generates more lift and vice versa. As more lift is produced, the engine
must deliver more power to the rotor disc, and,
therefore, the engine's throttle is placed at the end of the collective. This makes
it easier for the pilot to open the throttle
more when the collective is raised. All helicopters, at the very least, correlate the
throttle valve position to the position of the collective in order to reduce the pilot’s workload (by a device known as the 'correlator'). The pilot now only has
to make minor throttle adjustments.
Many models also come with a completely automated
throttle control (called the 'governor'). The end result, in both situations, should
be a near constant rotor RPM, within rather narrow upper
and lower limits (to prevent damage in the case of the former
and to prevent loss of lift in the case of the latter).
The cyclic controls the direction of the rotordisc thrust vector,
and is the pilot's direction control. It is positioned in front of the pilot’s seat
and is operated with the right hand. The helicopter will travel in the direction the cyclic is moved
to. The cyclic does its work by tilting the rotordisc in the desired direction.
Note that this will also result in a change in the helicopter’s
attitude!
The pedals control the amount of anti-torque rotor thrust, and are
therefore the helicopter’s yaw control. The pilot operates the pedals with his feet.
When the
left pedal is used, the nose will yaw to the left, and right pedal consequently
results in a right yaw. The effectiveness of the yaw control depends on the turning
direction. In one direction, the anti-torque rotor has to deliver less thrust in
order to let the engine's reactive torque turn the helicopter. In the opposite direction,
the anti-torque rotor has to increase its thrust to overcome the reactive force.
Note that in this situation, more power is required of the engine! This will result
in a loss of lift unless compensated for by a higher engine power setting (more
throttle).
From the previous example, it is clear that helicopter controls influence
each other. As a matter of fact, all three of the controls have an impact on each
other. It, therefore, requires some practice before a helicopter can be controlled
effectively.
Next topic >
Electrical System
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Cyclic & Collective
- The title of this book leads me to wonder what more it will teach me in addition to its content about these two, most frequently used, helicopter input controls. As it turns out, the answer is: a lot more. Of course, all of the obligatory subjects like basic physics, rotor aerodynamics and helicopter performance are dealt with as well, as are piston engine and basic helicopter manoeuvres. Yet the scope of this book is actually much wider than one might initially think.
Firstly, it is divided into a 'beginners’ and an 'advanced’ section. This means that the book can treat more complex concepts in depth, even though the focus in the first section is directed more towards newcomers to the field.
Secondly, subjects like turbine engines, multi-engine helicopters and autopilots are also examined. This is particularly helpful, since these topics are not usually covered in the majority of helicopter books aimed at this target audience.
Thirdly, the book deals with many things that you will not normally find in a text book: helicopter related experiences and a great deal of interesting detail. This is the sort of information that can only be provided if you have flown a lot of different helicopters and have been working in this industry for some time. What’s more, this tone is amplified by the consistently narrative style of the book.
- 536 pages
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Art of the Helicopter (Hardback)
- Well structured text that covers many technical aspects. It starts with an introduction to helicopters, followed by a treatment of
the technical background needed when studying them. Thereafter, dynamics, rotor systems, engines and transmission are explained in detail.
The book concludes with a section on performance and other types of rotorcraft. Its main asset is that the text is technically and
theoretically very accurate, and rather than mathematics, its focus is always on enabling the reader to achieve an understanding of
helicopters from a technical or engineering point of view. The more technically orientated reader will love this work.
- 416 pages
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Principles of Helicopter Flight (Paperback)
- If you are wondering how a helicopter flies, and really want to comprehend the process, you have no choice but to delve into
aerodynamics. This means not only understanding which forces play a role and the laws of physics, but also being able to put it all
together and apply your knowledge to a rotating system consisting of a number of rotor blades. This is a demanding task and requires
some very hard work. It is, undoubtedly, worth the effort though, and will help you to become a better pilot. There are many books out
there to help you with this task of exploring the principles of helicopter flight, but they tend to fall into two camps:
populist and taking a rather simplistic approach, or highly technical and assuming the reader has a degree in mathematics.
This book is different, because it clearly explains the principles of flight in a step by step way that is easy for most
readers to follow. Further benefits are that a lot of attention is paid to flight manoeuvres and operations, and every chapter
concludes with questions as a study aid.
- 320 pages
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