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Straight & Level Flight Introduction to the Flying Forces We left the last lesson having just leveled the aircraft off .Before we continue with the lesson we have to really study hard the the four forces of flight how they work and how they are controlled. The pilot has to be able to control them so that he/she can fly the aircraft safely and correctly. This is your main bread and butter subject it is important you understand this. Remember There are four forces involved in the flying of an aircraft. These are Thrust, Drag. Lift and Weight. A change in any one of these forces will bring in changes in all the others. If Thrust (Power) is increased then this will be greater than Drag and the aircraft will accelerate. This will cause an increase in Lift . The aircraft will climb because lift is now greater than Weight. As Power is reduced, Drag will become greater and the aircraft will slow down.. Weight will become greater than Lift and the aircraft will and descend. When all these forces are equal then the aircraft is level and stable.
Remember Thrust and Drag oppose each other, Lift and Weight oppose each other. How is Lift produced ? Air flows over and under the wing. The wing shape makes air that flows over the top go faster. Because the air is travelling faster the pressure on the top of the wing is less than underneath. Therefore the aircraft has LIFT and rises. When I am level how do I stop the aircraft climbing when I accelerate ? By applying forward pressure on the joystick.
This Reduces the wing angle of attack and less lift is generated. (see
below) My arm is aching I have got to fly like this for 3 hours, can I do anything about it.? Yes, remember the Elevator Trimmer I told you about in the previous lesson ? Trim the aircraft , then release the forward pressure on the joystick. If you have trimmed the aircraft correctly you will be able to fly virtually hands off the aircraft will not climb or descend. if the nose pitches up or down you have not trimmed correctly. To Accelerate or Slow Down Remember PAT another procedure Power Attitude Trim Power adjust throttle power for your required speed Attitude Pitch the aircraft forward to reduce the angle of attack to prevent exceess lift Trim before you arm aches holding the joystick I now want to slow down to Circuit speed of 90 knots the Air Traffic Controller told me to stay at this height. How do I do that as when I slow down the aircraft descends ?. Remember the four forces of flight in the first paragraph? This is why the aircraft is going to descend. I am now going to give you my fix wizard it is called Increasing the Angle of Attack. The Angle of Attack The wing as we
know when flying level generates lift. If you tilt the wing up then for each
degree it tilts it will produce more lift. If you tilt it down then less lift
is produced. Hence the angle of attack is the angle the wing attacks the
airflow. What you are doing by pushing the stick forward when accelerating is to prevent the angle of attack from increasing, and producing extra lift for unwanted climbing. When you slow down you want extra lift to stay at the same height so you pull back on the stick to change the angle of attack on the wing to produce extra lift to compensate for less lift being produced as the aircraft speed drops. Caution if you allow the angle of attack to get to great the wing will stall . This is a total loss of lift and the aircraft drops like a stone. If you stall and allow the wing to drop the aircraft will spin. you will learn how to recover from this later without having to parachute. Cold air at sea level is more dense than a high level area. This factor should be taken into account on a hot day as air is less dense then a cold day. The more dense the air the better the lift. To Level the aircraft from a
climb it is Attitude ,Power, Trim. Flying is about applying PAT and APT correctly all the time. Whether Cessna or Jumbo , F16 or B2 bomber.
Check your Heading has not changed, and that your wings are level using the compass and artificial horizon. Check also the Turn and Balance Indicator on a regular basis. You do not want to get lost do you ? Especially if there is high ground in the area and you are in cloud. Changing speeds in the air and maintaining the correct height is one of the hardest things the pilot will learn. Watch your instruments. Practice makes perfect. Eventually it will become second nature to you. When you apply power the propeller will cause a slipstream of air to pass down the side of the aircraft. This air will hit the tail and cause the aircraft to yaw slightly. (Normally left on most aircraft depending which way the propeller turns) The pilot would correct this by applying rudder using the rudder pedals to correct it. The turn and bank indicator has a little ball in a spirit level type instrument the pilot should apply rudder depending on which side the ball is. When the ball is in the centre the aircraft is then said to be straight. The more power the more pressure you need to apply to the rudder. The less power the less pressure. This is where the rudder trim comes in useful. (Just like the elevator trim on the tail.) Use this device. (You do not want to land get out of the aircraft and fall over with a dead leg do you ?) Now practice flying a a heading of 290 accelerate to 110 knots. Then slow down again to 70 knots and accelerate again to 110 knots . The object of the exercise is to stay at the same height and stay on the same heading. Trim the aircraft . What you need to learn now are the various power settings for different airspeeds and different pitch angles. Experiment by flying at 90 knots and increasing to 110 knots without gaining or losing height. Then slow down again to 90 knots. Remember slowly pitch the angle of attack up and retrim or slowly pitch down and retrim. Once you know your power settings on the RPM gauge it will be easier for you. Once you have settled in the speed retrim and just make fine adjustments to the power and retrim. Learn also your pitch settings on the attitude indicator for different stages of flight . Learn the trim positions. Everytime you alter speed or pitch or throttle you have to retrim. The next lesson we will
discuss is descending.
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