Lesson Seven – Procedure Turn

Learning Objectives

  • Be able to fly smooth left and right-hand procedure turns
  • Maintain a constant altitude throughout the manoeuvre
procedure-turn
procedure-turn

Procedure Turns

  • You will handle all take-off and landings

The procedure turn is a compulsory figure in the Bronze wings test.  It is designed so that the student pilot can demonstrate competent and accurate turning skills within a practical manoeuvre.

In real-life the procedure turn is as useful in model aviation as it is in full-size aviation.  It allows the pilot to fly a heading and then turn in the smallest possible area to return in the opposite direction along the same line.  This is particularly useful when trying to line up with the runway or a heading that will return you to the runway.

A procedure turn is made up of two turns:

  1. Fly along the runway centreline during a circuit
  2. At the end of the runway make a turn away from you through 90°
  3. Once this turn is complete, immediately make a turn through 270° in the opposite direction
  4. Exit the turn to fly along the runway centreline in the opposite direction to that from which you entered the manoeuvre

The key to the procedure turn is to make careful use of all controls to ensure the manoeuvre is flown at a constant altitude and that you enter and exit the pattern along the same line.

Lesson Six – Landing

Learning Objectives

  • Be able to land safely and under control
  • To fly ‘touch and go’ circuits
landing
landing

 

Landing

  • Your instructor will only intervene in an emergency

The art of landing an aircraft successfully take a bit of mastering as the key is to fly the aircraft to the ground and not into the ground!

Before starting your landing approach, be sure to let other pilots flying know what you are doing

By now you should have mastered the landing circuit and be able to fly the aircraft close to the ground along the runway centre line.  Once you have reached this point it is really just a matter of supporting the aircraft as the wing loses lift and it descends slowly to the ground.

  1. As you approach the runway close the throttle completely so the engine is only idling
  2. Only use the ailerons to keep the wings level, use the rudder to hold the aircraft straight along the runway
  3. As you cross the end of the runway – the threshold – you should be about 0.5 meters above the ground
  4. Try to hold the aircraft at this altitude by applying a little up-elevator – this is called flaring
  5. Only use enough elevator to support the nose of the aircraft, too much and you will start to climb and then stall
  6. As the aircraft slows further it will slowly descend the last 0.5 meters and touch down gently
  7. Use the rudder to keep the aircraft straight as it slows to a stop

Congratulations, if you are safely on the ground you have flown your first complete solo and there will probably be a lot of applause coming from behind you!

If at any time during the approach and landing you do not feel comfortable you can apply full power and climb back into the circuit.  Just because you have called a landing does not mean you have to land on that approach.

If you are going to abort your landing attempt call out ‘going around’ to let other pilots know what is happening

You will spend a lot of time practicing landing from different directions until you are comfortable with the approach and flare.  This is the time in the flight when your aircraft is at most risk of damage and it pays to be an expert at landing in all situations!

Touch and Go Circuits

Once you have mastered landing it becomes boring is every time you touch down you have to taxi back to the end of the runway to take-off again!

As you land the aircraft, immediately apply full power and let the aircraft pick up speed once more.  You can then take-off again within the length of the runway!

The important things to remember during touch and go circuits are:

  1. Let the aircraft build up enough speed to take-off as normal.  Do not let it ‘bounce’ back into the air too soon and cause a stall.
  2. Do you have enough room to speed up sufficiently to take-off?  If you do not then let the aircraft come to a stop.

Lesson Five – Landing Circuits

Learning Objectives

  • Be able to line up with the runway ready for landing
  • Recognise the correct time to begin descending in the circuit
  • Descend and slow the aircraft whilst turning safely towards the runway
approach
approach pattern for landing

 

Landing Circuits

  • You will handle take-off, your instructor will handle landings

There are two main components to the landing circuit and approach:

  1. The line-up with the runway
  2. The descent to the runway

You should practice the line-up first before you begin to worry about the descent.  This is easy to do and you should have it mastered already if you can fly smooth and accurate circuits in both directions.

Most landings are made on the main runway at the LMMAC field; that is the runway that runs left to right in front of the pilot’s box.  This is useful as we can use the electricity pylon directly in front of us as a guide when to begin our descent.

  1. At normal circuit height pull the throttle back to around 25% as you the aircraft passes over the top of the pylon
  2. Allow the model to lose height slowly, do not try to use elevator to force it down or hold the nose up
  3. If you are descending to quickly, apply a little power
  4. If you are descending to slowly, reduce power a little
  5. Once you flown past the end of the runway begin a slow wide turn onto your base leg
  6. Continue descending as you make another turn onto the runway centreline
  7. Let the aircraft continue descending towards the runway
  8. Once over the end of the runway, apply full power and climb the aircraft smoothly back up to circuit height – this is called going around

It will take some time for you to get used to your aircraft and how much throttle and space it needs to descend. Do not be tempted to push down on the elevator to lose height more quickly as this will cause the aircraft to speed up and you will not be able to land safely.

Most new pilots find that it is more difficult to judge the final turn once the aircraft is descending.  Practice this approach a lot until you have memorised the correct position and altitude for each stage of the approach.

Lesson Four – Take Off

Learning Objectives

  • Be able to hold a straight line on the runway during the take-off roll
  • Be able to take-off smoothly and climb safely to circuit altitude
img06
The first take off!

The Take-Off

  • Your instructor will handle all landings

Taking off with a model aircraft is really very easy, especially with a trainer aircraft as is will be designed to fly smoothly and to climb when certain airspeed is reached.

The most important aspect of the take-off is keeping the aircraft travelling in a straight line both on the runway and when it first becomes airborne.  For this reason we start this lesson by not taking-off!

Your instructor will let you keep control of the transmitter on the ground and ask you to taxi out onto the runway.

If another pilot is flying do not taxi out onto the runway until you are within the pilot’s box and have asked if the runway is clear for use – he may be about to land!

Once you are on the runway your instructor will ask you to taxi along the runway, using the rudder to keep the aircraft as straight as possible.  With each pass, try to get use a little more throttle so you can practice controlling the aircraft at take-off speed.

When you are ready, the instructor will ask you to line the aircraft up at the end of the runway pointing into wind.  Take-off is always made into wind so that we can get into the air at a slower ground speed and in a shorter distance.  Your instructor will explain the difference between air and ground speed as you are learning.

If another pilot is flying do not take-off until you have announced your intentions

  1. Once you are lined up and ready to go, increase throttle smoothly to full power
  2. Use the rudder to hold the aircraft straight as it gains speed
  3. Once the aircraft is about level with you on the runway, use a small amount of up-elevator to help the model ‘un-stick’ from the ground
  4. Keep full power applied and allow the aircraft to gain speed whilst climbing at around 20-30°
  5. Use the ailerons to keep the aircraft level as it climbs away from the runway
  6. Once you have reached a safe altitude begin to turn into the circuit, continuing to climb to circuit height
  7. Once at circuit altitude, pull back the throttle to maintain straight and level flight

You will find your trainer aircraft very easy to control on the ground and it will climb smoothly under full power.  The most important things to remember are to use rudder on the ground and aileron once airborne.

As most trainers are designed to climb under full power you may find you need little or no up elevator to climb to circuit height.  In fact, with some trainers you may need a little down elevator to stop the model from climbing to steeply!

Lesson Three – Stalling

Learning Outcomes

  • Have an understanding of what a stall is
  • Be able to recognise and react in a stall situation
  • Be able to avoid a stall

stall1 

Understanding the Stall

Look at the pictures above.  In the first image the wing has a smooth flow of air over its upper surface.  This smooth flow of air around the wing is what creates lift and keeps the aircraft in the air.

In the second picture we have started to pull the nose of the aircraft up.  This tilts the wing against the oncoming flow of air.  This is called changing the angle of attack of the wing.  As this happens the air flowing over the upper surface of the wing begins to lose its grip on the surface and does not follow the shape of the wing any more.  You may think this is what happens when we climb, but in actual fact in the climb we also increase thrust so the aircraft still penetrates the air as if it was travelling straight and level – as in the first picture.  A stall occurs when the nose is raised but we have insufficient power to climb.  In this situation the plane continues to fly straight and level only at a slower speed and with the nose raised.

In the third picture the wing is completely stalled.  The angle of attack is so great that air can no longer stick to the top surface of the wing and it breaks away, swirling around in small ‘eddies’.  When this happens the wing is no longer generating any lift and can no longer counteract the force of gravity, so the aircraft falls from the sky!

Reacting to a Stall

To learn to react to a stall your instructor will ask you to fly the following steps:

  1. Starting from a normal circuit, you will create a stall during the upwind leg
  2. At a safe height, close the throttle and start to pull back gently on the elevator to raise the nose a little
  3. Continue to raise the nose as the aircraft slows down
  4. Once a stall occurs the nose of the aircraft will drop sharply, keep the aircraft straight using the ailerons and centre the elevator
  5. Allow the nose to drop and apply full throttle
  6. As the aircraft gains speed, use the elevator to bring the nose up and regain straight and level flight
  7. Climb back to circuit altitude and continue to fly the circuit

This whole process will take no more than a few seconds and the aim is to keep the aircraft flying straight without dropping a wing and losing as little height as possible.

Avoiding the Stall

This lesson becomes important when you are flying slowly and close to the ground, i.e. just after take-off and just before landing.  Practice stalling at altitude so that you can recognise when you model is going to stall and how slowly you can fly before a stall occurs.

If you think a stall is going to happen, the methods to avoid it are simple:

  1. Let the nose drop a little back towards a level attitude
  2. Increase power

Practice flying close to a stall and then pulling out of it before the nose drops.  If you can recognise the signs and react before the stall occurs you should never be in danger of nose diving into the runway!

The Tip-Stall

A tip stall occurs when just one half of the wing stalls, causing the aircraft to tip violently to one side and enter a spiral-dive.  This occurs when an aircraft turns too tightly at too slow a speed, which most often when you are making the final turn towards the runway for landing.  For this reason you must always make sure that your slow turns are made as wide as possible with as little bank in the wing as possible – this will be covered in more detail when you learn to land.

Lesson Two – Figure '8'

Learning Objectives

  • Be able to fly accurate left & right-hand figure ‘8’ patterns
  • Maintain a constant altitude whilst flying in this pattern

figure-8 

Perfecting the Turns

  • Your instructor will handle take-off and landings

The figure ‘8’ pattern is not included in the Bronze Wings test but is a useful training tool as it will allow you to practice left and right-hand turns until you can make precise, constant level manoeuvres in any direction.  This pattern always starts and ends over the centreline of the runway with the crossover point in front of the pilot.

  1. From a normal circuit start an upwind leg over the centreline of the runway
  2. As you begin to fly up the runway, make a 90° turn away from you
  3. Once the aircraft is flying away from you, make a 90° turn back in the opposite direction of the first turn
  4. Continue turning through another 90° until you are flying back towards the end of the runway
  5. As you come around to face the runway continue to turn back onto the runway centreline but facing in the opposite direction to that from which you started the manoeuvre
  6. Instead of flying straight on, carry on turning away from yourself until you cross point 3 once more – completing the first 360° turn
  7. Now make a 180° turn to the left to come around and point back at the other end of the runway
  8. Complete the manoeuvre by flying the final 90° turn back onto the original runway heading
  9. Fly along the runway and continue into a normal circuit pattern

At first this simple pattern will seem nearly impossible to fly smoothly as the turns will be too tight, too loose or you will gain and lose a lot of altitude.  As you spend more time practicing however you will find that you must use a combination of aileron, elevator and throttle to fly an accurate figure ‘8’.

The most important thing to remember when flying the turns is that it is not simply a case of applying a certain amount of aileron and elevator and holding it there.  You would not turn a corner in your car this way and you do not turn an aircraft this way either!  Turning accurately requires you to master balancing the controls; making constant small adjustments to fly a nice smooth line.

Keep practicing this even once you have passed your Bronze Wings as it is the basis of flying every different type of radio control aircraft and every different kind of aerobatic manoeuvre!

Lesson One – Circuits

Learning Objectives

  • Be able to fly a square left & right-hand circuit of good size, shape and orientation
  • Maintain a constant altitude whilst flying in the circuit
  • Understand how control inputs effect the models flight attitude

Flying the Circuit

  • Your instructor will handle all take-off and landings

A circuit is the most basic pattern of flight used in all forms of aviation.  It is a rectangular flight-path, flown at a constant altitude with the upwind leg flown along the centreline of the runway and into wind.  It is designed and positioned like this so that other aircraft that are taking off or landing are able to do so safely without fear of colliding with another airborne aircraft.
Once your instructor has got the aircraft airborne and flying straight and level in the circuit he will hand you the controls on the downwind leg.  From here you will need to make a series of 90° turns to keep the aircraft in the circuit pattern.
Do not adjust the throttle at this point.  Concentrate on using aileron and elevator to make a smooth turn as follows:

  • Use aileron to bank the aircraft left or right.  Move your right thumb left to bank left and vice versa.
  • Use a small smooth movement to roll the wings about 20-30°, the aircraft will start to turn
  • Now, as the aircraft begins to turn, use small amounts of up elevator to keep the nose from dropping and keep a constant altitude throughout the turn
  • As you reach the end of the turn, use the ailerons to roll the wings level again

The use of elevator is important in the turn to maintain altitude.  Without it the nose will drop and the aircraft will start to dive in a spiral motion towards the ground.  Using the elevator like this is called ‘supporting the nose in the turn’.
Most circuits at the LMMAC field are made in an anti-clockwise direction but we will practice both.

Using the Throttle

As you become more proficient at flying the circuit pattern we will start to introduce throttle to control the altitude of the aircraft.
Most trainers are set up to have ‘positive stability’.  This means they are designed to fly, when correctly trimmed, straight and level at a set speed.  (Your instructor will get the plane flying like this before the lessons begin).  If this straight and level is disturbed by a control input, the aircraft will try to return to this straight and level state.  We can take advantage of this by using the throttle to force the aircraft to climb or descend.
If you feel the aircraft is descending in the circuit.  Move the throttle up by a couple of clicks, this will cause the nose of the aircraft to lift as the wing generates more life and climb slowly.  If the aircraft is climbing too high, reduce the throttle a little and let it descend slowly back down to the desired altitude.
Later on we will use this throttle control to help us climb after take-off and descend to the runway for landing.

i.c. to electric Conversion Table

This is quite simply as it says in the title.  I have put together a little chart that will show you how many watts of power you need from your motor to equal the power of your two-stroke motor…
Remember, to work out the watts we multiply the continuous current of the motor by the number of volts going in.  So when you look at this table, divide the number of watts by the battery you intend to use and that will tell you what sort of amps your motor is going to have to draw to get there.
Clear as mud?  On with the chart then…

2-Stroke Motor Size

Electric Equivalent (watts)

0.20 cu.in

300w

0.35 cu.in

500w

0.40 cu.in

750w

0.60 cu.in

975w

0.90 cu.in

1200w

1.20 cu.in

2250w

50cc

3750w

100cc

7311w

Hopefully this will give you some idea when it comes to choosing an electric motor for your model.

What about the Watts?

A lot of people are confused when they first get involved in electric flight as to which motor, speed controller, battery combination to use to power their model.  This is the first in a series of posts that will look at how to determine and choose the best power train for your electric model…
The first, and most useful, development in the world of electric flight are the manufacturers who actually label their motors with equivalent 2-stroke i.c. motor sizes.  The best know of these are the E-Flight Outrunner series, which stretch all the way from .10 size motors right up to a whopping 1.80 size unit!  They aren’t the cheapest on the market but are very high quality and certainly worth the bucks if you can afford it.  We’ll look at i.c. to electric conversions in another post.
However, if you are looking at building a custom power system, maybe from E-Bay or another online seller, then you will need to work it out for yourself.
The first thing we need to look at is what sort of model you are building and how much power you need to fly it…
With electric models, power is measured in ‘Watts’.  Effectively the more watts a motor can produce, the more thrust is generated at the propeller.  Different types of model have different power requirements, a slow flying trainer needs far less power than a balls-out 3D model.  To give a basic idea we use the following:
Trainer/Sports Model:     90W/lb
Powered Glider:    120W/lb
3D Model:    175-200W/lb
This is just a basic guide, a lot of my models are of the 3D type and so I aim for 200W/lb.  I have designed a couple of smaller sports models that have used 90W/lb and have flown very nicely.
You will notice that the figures given state watts per pound (lb).  You will need to look at the finished flying weight of your model and then work out the power from there.  For example, if your ARTF spitfire weights 3lb 8oz flying weight then you will require (90 x 3.5 =) 315 watts minimum from your motor to get a decent flying performance.
So how do you work out how much power a motor will give?
All motors will give you basic information in their advertisement (if they don’t then don’t go there).  This will hopefully include a ‘Continuous Current’ rating and a ‘Recommended Input Voltage’ – these are the two figures you want to look at.
Quite simply multiply one by the other, for example:
Motor Continous Current = 30A
Recommended Input = 11.1v
Therefore 30 x 11.1 = 333 watts
The 333 watts is what the motor will generate at full throttle and assumes you are using the recommended prop size and your lipo isn’t losing all of its charge when under load.  Therefore, always select your motor to give slightly more power than you need.  You don’t have to fly at full throttle the whole time and flying at lower throttle settings will give you a longer flight.  The only way to know for sure is to use a wattmeter when you have your set-up in the workshop – but that does’t help when you’re buying.
Have fun out there and drop me a line on the contact form if you want to ask an electric flight question…

Safety with LiPo batteries

With more and more people trying electric flight I thought I should include this article on the safe use of lithium polymer batteries…
This article is taken from the British Model Flying Assosciation, which can be found at www.bmfa.org

A guide to safe use of LiPo batteries

from the British Electric Flight Association.
Despite what a number of people may tell you Lithium Polymer (LiPo) batteries are not fundamentally unsafe, but they need to be treated with more care than NiCd or NiMH. If abused sufficiently LiPo cells can catch fire and this fire can be difficult to extinguish. The following precautions should help you enjoy using LiPo batteries without having a major incident.

General precautions:

  • The minimum safe discharge voltage is 2.5V per cell when under load, or 3.0V per cell when not on load.
  • When more than 2 cells in series are used, a controller with an adjustable cutout should be used and it should be set at or above 2.5V/cell.
  • Only charge LiPo batteries on a charger specifically design for LiPo batteries.
  • Always ensure you use the correct charging voltage for the cell count.
  • The maximum charge rate should be 1C, eg. 0.7A for a 700 mAh cell. For best charging, low charge rates should be used where possible.
  • Check the charge voltage (or cell count) and current a second time.
  • Never leave charging LiPo cells unattended (at any charge rate).
  • It is best to charge LiPo cells in an open space on a non-flammable surface (such as a brick or quarry tile) and away from flammable materials.
  • For long term storage it is recommended that cells are fully charged and then discharged to between 50% and 60% of their capacity.
  • Use connectors that can not be short circuited, or use silicon fuel tube to protect exposed connections.
  • Have a dry powder fire extinguisher or a bucket of dry sand within reach.

If a pack is involved in a crash or is otherwise damaged:

  • Remove the pack from the model.
  • Inspect the pack for damage to the wiring or connections.
  • If necessary, disassemble the pack and dispose of any damaged cells.

Disposal of LiPo batteries:

  • Put the pack in a safe open area and connect a moderate resistance across the cell terminals until the cell is completely discharged.
  • CAUTION: The pack may get extremely hot during the discharge.
  • Puncture the plastic envelope and immerse in salt water for several hours.
  • Place in your regular rubbish bin.

By Jan Bassett (BEFA)