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Issue No 52, 4 December 2023
By: Anthony O. Ives
'Rocket Scientist' is often a term used to describe someone who is very clever even though its usually in a sarcastic way. However, the term is probably more related to rocket guidance more than rocket motors. Rocket vehicles are unstable and require a guidance system to keep them from flying all over the place much like a busted balloon. The term could also relate to the compliciated mathematics that is needed to calculate speeds and trajectories of spacecraft in orbits and interplanetary spaceflight. The rocket motor itself is quite simple a gas turbine engine is by far more complex.
Issue No 51, 20 November 2023
By: Anthony O. Ives
A ducted fan could be simply described as propeller inside a duct. Ducted fans give a number of performance benefits the most obvious being they reduce tip vortices at the fan blade tips. However, there are other advantages such as you can design the duct to give the flow characteristics you want upstream or downstream this means you may not need varible pitch blades. You can also use varible pitch guide vanes which are more or less stators instead of variable pitch fan blades which are more complex as they rotate and guide vanes do not.
Issue No 50, 6 November 2023
By: Anthony O. Ives
In the most simple terms integration is the reverse of differentiation, for example you should now be familar with the linear equation, therefore if you the known the rate of change of one varible against another variable, using integration you should be able return to the orginal linear equation if your rate of change is constant. However, another use for integration is that it can used to determine areas confined by a curve or set of curves. If you know the exact mathematical equation of the curve you can calculate an exact area if the equation is not known or is difficult to integrate then numerical integration can be used to estimate the area. Numerical integration can be performed using simpson's rule. For the present we will look at exact integration methods and look at simpson's rule in a later article.
Issue No 49, 23 October
By: Anthony O. Ives
Most commerical helicopters are powered by gas turbine engines because they have a higher thrust to weight ratio than piston engines. As piston engines become more powerful their increase in weight makes them impractical for aviation whereas gas turbine engines can produce a larger amount of power for less weight. However, the disadvantages of gas turbines is they have higher fuel consumption and they are more expensive to manufacture this is why piston engines are still used in light aircraft and helicopters.
Issue No 48, 16 October 2023
By: Anthony O. Ives
In a previous article I covered the linear equation and introduced gradient which is the rate of change of one variable against another variable. Differentiation is the process of determining the rate of change which is usually an exact process if the equation which relates one variable to another variable is known. If the equation is not known or is difficult to differentiate then numerical differentiation can be used to determine rate of change using discrete data. However this article will look exact differentiation methods and numerical methods will be introduced in a later article.
Rolling Take offs and Landings
Issue No 47, 9 October 2023
By: Anthony O. Ives
Rolling take offs and landings are considered an advanced operation for helicopters. They are usually neccessary if the helicopter is operating close to its maximum operating weight in a high density altitude (or low air density environment) where there is not enough power to hover before taking off or landing. Rolling landing can also be performed in emergencies such as in the case of a tail rotor pedal becoming stuck at a low power setting. However, this article will look at fixed wing aircraft take offs and landings and mainly the ground run segment, take off and landing do actually have air segment as well.
Issue No 46, 2 October 2023
By: Anthony O. Ives
In earlier articles range and endurance have been discussed as well as the various ratios that when they are a maximum give the best range and endurance. There are three ratios that are important for understanding aircraft performance, the first of course is obvious as it is lift to drag ratio the remaining consist of lift coefficient raised to 3/2 over drag coefficient and lift coefficient raised to 1/2 over drag coefficient. The ratios mainly apply to fixed wing aircraft where the ratio of lift coefficient raised to 1/2 over drag coefficient is only really applicable to jet powered aircraft as discussed in an earlier article. The maximum ratios are achieved at specific aircraft speeds so its important these speeds can be calculated also.
Issue No 45, 25 September 2023
By: Anthony O. Ives
A vector quantity is a quantity that has both magnitude and direction such as velocity. Velocity should be described with a direction for example when descriding wind conditions you usually say something like '10 knots north easterly'. A scalar quantity is a quantity that has no direction or none specified such a mass, volume, density, temperature, etc. While velocity is considered a vector, speed can be considered a scalar hence velocity can be defined as speed with direction. Examples of other vector properties are forces, distances even torque and moments can have direction but just not as obvious, so technically torque and moment can be specified as vectors.
Issue No 44, 18 September 2023
By: Anthony O. Ives
My knowledge of psychology is very limited and does not really extend beyond what I learned for the human performance pilot theory exams however, from my own experiences I have generally come across two attitudes to safety. One safety attitude is those nervious types like me who generally worry about everything and the other type who hopefully still do the safety checks but worry less about what could go wrong. No doubt the latter safety attitude can exist in the extreme of not worried about doing any safety checks but thankfully I never met anyone who is completely suicidal. If you are the type of person who likes extreme sports then you are probably going to be more relaxed about safety and just do your safety checks in an automatic way. In reality like most things there are probably advantages and disadvantages to both types of attitudes, like most things its important that you are aware of the advantages and disadvantages, then take steps get the most out of your advantages and finds ways to compensate for the disadvantages.
Issue No 43, 11 September 2023
By: Anthony O. Ives
Determinents are a set of numbers arranged in rows and columns similar to matrices with the exception that a determinent has to have the same number of rows and columns which is the same as square matrices. The number of rows and columns is the order of the determinent so therefore a 2nd order determinent will have 2 rows and 2 columns, a 3rd order determinent will have 3 rows and 3 columns, etc. Determinents like matrices can be any order but as they are generally used by computer to solve simultaneous equations therefore will be limited as to highest order of determinent due to computing resources. Matices and determinents are used by computers to solve other problems as well but their biggest application is probably solving simultaneous equations. Matrices will discussed in more detail in later articles.
Issue No 42, 4 September 2023
By: Anthony O. Ives
The thing I most like about gliders is that they are one of simplest aerodynamic flying machines you can make using wood, of course you could say a paraglider is simpler but building one seems more complex to me. Gliders rely on their very efficient aerodynamics and enviromental updrafts to stay airborne for as long as possible. The equations to calculate a glider's performance are also quite simple and can be easily derived from the equilbrium of all the forces acting on the glider. However, the gliding performance of a fixed wing powered aircraft can also be important as in the case of engine failure the aircraft should be able to glide safely back down to the surface.
Jet Aircraft Range and Endurance
Issue No 41, 28 August 2023
By: Anthony O. Ives
Range and endurance for jet powered aircraft is different from that for propeller powered and rotary wing aircraft. The difference is down to the fact that for jet powered aircraft fuel consumption is related to thrust. For propeller powered or rotary wing aircraft fuel consumption is related to power. While VTOL (Vertical Take Off Landing) aircraft powered directly by jet thrust do exist they are fairly rare and generally used for specialised military aircraft but with recent interest at the time of writing in advanced air mobility (AAM) some of the proposed designs for AAM such as the Lilium Jet might be considered a jet thrust powered aircraft.
Issue No 40, 21 August 2023
By: Anthony O. Ives
Simultaneous equations are encountered when you have a number of unknown properties for which there is at least the same number of conditions hence you have the same number number of equations as unknowns. For example if you have two unknowns you will need at least two equations to work them out, if its three unknowns then you will need at least three equations to work them out, and etc. Simultaneous equations are often the principle on which a lot of software is based that uses numerical methods such as FEA (Finite Element Analysis), CFD (Computational Fluid Dynamics), etc. Determinents, matrices are also methods by which a computer can be used to solve large number of simultaneous equations for large number of unknowns in numerical methods. However determinents and matrices will be looked at in future articles.
Learning to Fly RC Helicopters
Issue No 39, 14 August 2023
By: Anthony O. Ives
I intially learned to fly fixed wing RC aircraft because I was told it was easier than learning to fly RC helicopters. My experiences of learning to fly fixed wing RC aircraft were frustrating and it seemed to be neverending not to mention I was not having any fun. RC helicopters were also more expensive when I started learning to fly RC aircraft, but then with the introduction of Lipo batteries and small electric micro helicopters, flying helicopters became more accessible. I immediately enjoyed learning to fly helicopters even though it was probably not easy I never noticed because I was having more fun.
Issue No 38, 7 Aug 2023
By: Anthony O. Ives
Fear of flying is natural as you are taking a certain amount of risk by going up in an aircraft which means you are trusting your life to a lot things such as the aircraft structure, the aircraft engine, weather, etc. However, we all take a certain amount risk every day going about our business, things like walking down stairs involve risk, driving a car is the highest risk most us take in our daily lives. Driving a car is probably one of the most dangerous things that anyone can do arguably more dangerous than extreme sports or others activies that are percieved as very high risk such as skydiving. However, the main reason most people do not think of driving as dangerous is because its very familar and we do it everyday which is probably the main reason driving is dangerous.
Issue No 37, 31 July 2023
By: Anthony O. Ives
Quadratic equations were introduced previously as a 2nd order polynomial equation. So a polynomial equation is a general term used to describe equations such as cubic, quartic equations, etc where a cubic equation is a 3rd order polynomial and a quartic equation is a 4th order polynomial. A polynomial can be of any order from 1 to infinity such as where the order denotes the highest index term. General the higher the order of the polynomial the better it is at curve fitting.
Issue No 36, 24 July 2023
By: Anthony O. Ives
An eVTOL is an electric vertical take off and landing aircraft, a small scale UAV (Unmanned Air Vehicle) version is more or less a hybrid quadcopter and fixed wing UAV. The hybrid quadcopter and fixed wing UAV works well as the additional weight of having four electric motors for vertical flight as well as a separate larger motor for forward flight is fairly small. Compared to the complexity of a rotor tilting mechanicism which will probably not really save on the weight of the four motors for vertical flight given the simple design.
Trailing Vortex Drag: Drag produced by Lift
Issue No 35, 10 July 2023
By: Anthony O. Ives
Different types of drag has been looked at in some previous articles. This time we are looking at the main source of lift induced drag in fixed wing aircraft which is trailing vortex drag. Of course lift can cause increases in other types of drag due to changes in pressure distribution, etc. While trailing vortex drag is mainly associated with fixed wing aircraft the same effect causes an increase in helicopter rotor power known as induced power.
Issue No 34, 3 July 2023
By: Anthony O. Ives
Quadratic equations are 2nd order polynomial equations which can be used to solve higher order polynomial equations. In a future article general polynomial equations will be discussed in more detail. Quadratic equations have a wide range of applications and can be used to solve various mathematical problems with engineering applications. Quadratic equations have a formulae which allows you to find their roots precisely. A root of a polynomial is the value of the independent variable (the x variable) for which the dependent variable (the y varible) will be zero.
Attack of the Drones: Quadcopters
Issue No 33, 26 June 2023
By: Anthony O. Ives
Quadcopters, known by most people as drones have become increasingly popular since 2015. Quadcopters are especially popular with the general public who normally would not have an interest in aviation or model aircraft, as they are electronically stablised and hence you do not need to learn to fly them as with traditional model aircraft. People who fly traditional model aircraft often say that the drone was the worst invention as due to the ease of use and their popularity they have become nusiance and brought about a lot of additional rules that now apply to traditional model aircraft as well. However, quadcopters do have their advantages with their simple design they have made aerial photography available to most people and can perform other aerial tasks at a much lower cost.
Helicopter Translational Lift and Forward Flight
Issue No 32, 19 June 2023
By: Anthony O. Ives
Helicopter forward flight produces performance benefits as well as further complexities. As the helicopter transitions from hover to forward flight the required power for flight reduces due to a effect called translational lift which is usually experienced at a forward speed of around 15 knots. However, the rotor airflow becomes unsymmetrical with forward flight resulting in rolling action which must counteracted to some degree by the pilot.
Issue No 31, 12 June 2023
By: Anthony O. Ives
A previous article introduced the concept that it was not possible to take the square root of a negative number. However, the solution to this problem is quite simple you just use an imaginary number 'i' to represent the square root of a negative number and treat it like you would any unknown number. When imaginary numbers are combined with other numbers (known as real numbers) that are not imaginary numbers such as the type of ordinary numbers most people are familar with they are called complex numbers. Imaginary and complex numbers have important applications and a lot of technology would not be possible without them. For helicopters imaginary and complex numbers are needed for control and stability analysis as well as aircraft control systems, but beyond helicopters they are used for analysing alternating current, vibrations, etc.
Drawing Your Own Model Aircraft Plans
Issue No 30, 5 June 2023
By: Anthony O. Ives
Drawing plans for a small, lightweight model aircraft is fairly straightforward especially if its based on an existing full scale aircraft. However, the bigger, heavier your aircraft design becomes then the more the drawings plans for your aircraft becomes more complex requiring more detailed design analysis. Heavier aircraft also come with additional legal requirements, there are usually different legal requirements for different weights of aircraft, generally the heavier the aircraft the more legal requirements that are required. However, with the increase in popularity of drones (quadcopters) most aviation authorities have introduced some legal requirements even for the lightest of radio controlled aircraft so it is important that you always check the requirements of the aviation authority for the country you live in. A future article will discuss airworthiness requirements in more detail. Its a good idea to get some experence building model aircraft from plans before attempting to draw your own plans which will help you with some of the practical aspects of building model aircraft. A previous article discussed how to build a model aircraft from plans which may help you understand the practical issues you have to consider when building model aircraft.
Issue No 29, 29 May 2023
By: Anthony O. Ives
There are many ways of defining drag such lift dependent drag, profile drag, form drag, wave drag, etc. However, I always find it easier to remember drag by the typical things that cause drag such skin friction, separated flow, lift induced trailing vortices and shock waves for high speed flow. In this article I will discussing drag caused by mainly skin friction and separated flow. In future articles I will discuss drag caused lift induced trailing vortices and shock waves. For helicopters shock waves are not really a major concern apart from in rotor tip region where the flow can approach the speed of sound. Apart from shock waves most drag is caused by friction or viscosity maybe just not directly and as obviously usually because the process through which friction losses occur are induced by either separated or lift producing flow.
Intergers, Floating Numbers and Negative Numbers
Issue No 28, 22 May 2023
By: Anthony O. Ives
Intergers are whole numbers such as 1,2,3,4,5,.....120,....,etc. Floating numbers are which are not whole numbers such as 0.7, 2.5, 3.4, etc otherwise described as decimal numbers. Negative numbers are numbers less than zero such as -1,-2,-3,-4.....-120,.....,etc. Negative numbers in particular have a specific arithmetic in how they are added, subtracted, multiplied and divided. Floating or decimal numbers are really added, subtracted, multiplied and divided in the same way as intergers if you don't let the decimal point confuse you.
Building Model Aircraft from Plans
Issue No 27, 15 May 2023
By: Anthony O. Ives
Building model aircraft from plans was the one I miss about flying fixed wing aircraft. It is possible to build any shape of a fixed wing aircraft from wood. While I did not find flying fixed wing aircraft that enjoyable, I really prefer and have more fun flying helicopters it also took less time for me to learn to fly helicopters. However, I do enjoy making things out of wood, generally the great thing about wood is that you can almost make anything from it. The helicopter is the one exception while it is not impossible its just not really practical to make a helicopter from wood. So my sole interest in fixed wing aircraft is building them from wood and allowing me the work with wood, building something that is relevant to flight. However, in more recent times there is also the possibility that a fixed wing aircraft can be VTOL (Vertical Take Off and Landing) which is closer to how helicopters operate. The process of building model aircraft from plans can also be used even if you are building a helicopter from metal and composite materials, its just that a more complicated process will be needed to make the individual components.
Issue No 26, 8 May 2023
By: Anthony O. Ives
Vortex ring state is a dangerous flight condition which a helicopter can experience in a fully powered, low speed and high descent rate scenario. Vortex ring state reduces the efficiency of the helicopter's rotor to produce thrust resulting in an increasing descent rate, the natural response of the pilot to apply more power will worsen the condition causing higher rates of descent. When vortex ring state can be encountered can often be confusing for pilots as it is often associated with allowing the helicopter to descent too rapidly however autorotations with high rate descents do not generate the vortex ring state. Autorotations are a power off helicopter descent, vortex ring state is only possible in power on descents. 'Settling with Power' is another term used to refer to vortex ring state but the term can also refer to any condition where increasing helicopter engine power does not reduce the helicopter's descent such the engine not being able to generate enought power due to helicopter weight or environmental conditions such as temperature, altitude or humidity, etc.
Issue No 25, 1 May 2023
By: Anthony O. Ives
Issac Newton was an english physicist who discovered three principles that define a equilibrium, forces and motion. Apparently Issac Newton was due to go to Cambridge university but could not go immediately due the great plague and instead stayed at home and came up with his three laws. Chances are if had went to university when he was suppose to he would not have discovered these three laws.
Charging and Discharging of Batteries
Issue No 24, 24 April 2023
By: Anthony O. Ives
For simplicity in most cases it is assumed that batteries discharge and charge at a linear rate, that is the battery charges and discharges proportional to time. A simple example is if a battery takes 5 minutes to lose half of its charge then in 10 minutes it will be fully discharged, or in a charging scenario if it takes 1 hour to regain half of its charge then in 2 hours the battery will be fully charged. The above example assumes the charging and discharging current is constant which means it does not change with time. In reality, batteries charge and discharge in a way similar to the way a capacitor charges and discharges which is exponential relationship. A capacitor is an electronic component that is used in electrical circuits to hold charge.
Airfoil Lift Generation and Lift Coefficient
Issue No 23, 17 April 2023
By: Anthony O. Ives
Airfoil lift generation has been explained in different ways with some explanations not being completely correct. However, sometimes a simplified explanation is helpful if it makes it easier to remember a important concept this is particular true if you are learning the princples of flight for pilot training. Lift generation is not really easy to explain, in reality airfoils produce a vortex which then generates circulation around the airfoil. The circulation around the airfoil slows the airfoil on the lower surface of the airfoil while causing high speed airflow on upper surface. These differences in airfoil speeds on the upper and lower also produces a pressure difference between upper and lower surface which cause the airfoil to lift this principle is described by the bernoulli equation. The equation for lift equation is derived from vortex theory as in shown in most aerodynamics books.
Issue No 22, 3 April 2023
By: Anthony O. Ives
Pythargoras theorem enables you to determine the length of the remaining side of a right angle triangle if you already know the length of the other two sides. Pythargoras theorem is an important theorem of trigonometry. Like trigonometry it is important for a wide range of applications including engineering, vector analysis, navigation, architecture, etc. The distance formula for cartesian co-ordinates is also derived from pythargoras theorem. The distance is used in a wide range of applications including navigation and is very important for modern satelite navigation systems such as GPS Navstar.
Electric Motors and Speed Controllers (ESC)
Issue No 21, 27 March 2023
By: Anthony O. Ives
For RC aircraft electric motors have advanced a lot particularly with the introduction of brushless motors. Electric powered RC aircraft can achieve the same performance that previously would only have been possible with aircraft powered by internal combustion (IC) engines. A lot of the inprovement in performance of electric powered vehicles in general is due to the high power lithium batteries however, brushless motors have also improved the efficiency. Brushed motors generally generate more losses especially when the carbon brushes wear down however, brushless motors require a more complicated and hence expensive speed controller (ESC).
Issue No 20, 13 March 2023
By: Anthony O. Ives
There is a belief or maybe a myth that an engine failure in a helicopter means the helicopter falls out of the sky with certain death for its occupants. However, this is completely wrong engine failures in a helicopter are just as survivable as those in fixed wing aircraft, helicopter pilots and ethusiasts like me will tell you they are actually more survivable than one in a fixed wing aircraft. In the case of an engine failure in a helicopter, the helicopter is in theory capable of landing in a reasonably small area with very little forward motion, if the landing is done correctly the helicopter will not even get damaged. One the advantages of a helicopter is it can land anywhere the same applies in the case of an engine failure, a helicopter has a much better chance of finding a suitable landing area in an emergency. An engine failure or any emergency in a fixed wing aircraft presents a big problem because it has to essentially find a airstrip of some sort so usually most engine failures in fixed wing aircraft result in some damage to aircraft mainly due to need of fixed wing aircraft to maintain some forward motion and crashing into fences or rough ground. Engine failures in any aircraft are something that should be avoided that is why aircraft engines are required to be well maintained and pilots perform detailed checks all to reduce the chance of engine failures. The pilot should also monitor the engine instruments and plan the flight that they can get to a suitable landing site. Generally speaking engine failures in most modern aircraft are fairly rare. Helicopters land safely after an engine failure by entering autorotation which involves the pilot carrying out a series of actions to maintain rotor RPM. The golden rule to staying alive in helicopters is to maintain rotor RPM this applies always and not just in autorotation.
Four Codes for Solving Mathematics
Issue 19, 6 March 2023
By: Anthony O. Ives
If truth be told I don't really like computers and try to spend as little time as possible on them. I'd rather be flying, swimming, doing some other outdoor activity or building something. However, computers claim to make our lives easier if they do what they are suppose to. The thing that I enjoy doing the most of on a computer is programming especially solving mathematical problems. I have always liked mathematics its probably the only purely academic subject that I was ever good at. Computers open up the possibility of solving complex equations using numerical methods. Numerical methods use thousands, millions or more of simple arithmetic calcuations to solve complex equations that could not be solved in an exact way. In this article I am going to introduce you to four useful codes for solving mathematics and creating your own custom software. Most of the codes use tools that are freely available.
Issue 18, 27 February 2023
By: Anthony O. Ives
Electric power is being pushed as the future at least the time of writing that was the case. The argument is that its more environmental friendly primarily by reducing CO2 emissions. Whether you believe that argument does not really matter because political legislation at the present time is pushing us toward electric powered vehicles so it could be the case that we will come more dependent on electric power in the future. Electric power is also the most convenient way to power small UAVs. Batteries are one option for storing and delivering power to electric powered vehicles the other is fuel cells. Batteries and fuel cells are closely related in working principle.
Optium Aircraft Mission Designs
Issue 17, 20 February 2023
By: Anthony O. Ives
Each aircraft design is usually optimised for a specific mission. Military aircraft have a larger variety of missions than civilian aircraft. While I generally prefer to stay away from any involvement with military projects, military aircraft can be very interesting as they use the latest technology. Some of the latest technology in the civilian world were derived from military applications, so you may learn something that you can apply for peaceful means. Civilian aircraft will also be discussed and compared with military aircraft missions.
Helicopter Hover and Propeller Power Coefficent and Efficiency
Issue 16, 30 January 2023
By: Anthony O. Ives
In order to determine power required to turn a helicopter rotor a power coefficient can be calculated which is similar to thrust coefficient. The power required for a helicopter rotor is closely related to drag in the form of the drag polar equation. Propellers and helicopter rotors are very similar and generally use the same equations to calculate thrust and power. Efficiency is the amount of power that is usefully converted to thrust. Efficiency for propellers is propulsion efficiency, for helicopter rotors its hover efficiency. Both propulsion and hover efficiency are calculated slightly differently.
The linear equation, gradient and rate of change
Issue 15, 16 January 2023
By: Anthony O. Ives
The linear equation is a fundamental mathematical equation and concept. In reality most people use this concept all the time without knowing it when they estimate something based on an average value. The linear equation and linear relationship is simple to solve hence why in mathematics this terminology is used for any equation that has a solution. Unsolvable expressions are often referred to as non-linear, the Navier-Stokes equations (complicated equations which give a complete description of fluid mechanics, a future article will discuss them in more detail) are often referred to as non-linear. Ideally in mathematics various methods are applied to reduce complex relationships down to a principle linear equation but this is not always possible. The gradient is very easy to determine from a linear equation. The gradient often represents the rate of change between the two variables of the linear equation.
Issue 14, 2 January 2023
By: Anthony O. Ives
Radio Controlled (RC) model airplanes and helicopters are usually controlled by linkages to the control surfaces or swash plate respectively. The control linkage is moved by a servo, the servos are all connected to a radio receiver. The receiver receives control signal from transmitter. The RC transmitter usually has two control sticks which the operator uses to maneuver the aircraft if control is manual however modern commercial UAVs can also use automatic control. Both the transmitter and reciever need a power source such as a battery.
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