Gardner Textbook Review Questions for Class #3

Transcription

1 ANSWERS to the Homework Questions Prep for Class #3. Do Not View this until all questions are answered. Use the following to correct or improve your answers. Correct or append your answers using another color pencil or pen or font. Do not erase incorrect answers line them out or use strike through so the incorrect data are still readable. Gardner Textbook Review Questions for Class #3 GL01-04 As altitude increases, the indicated airspeed at which a given airplane stalls in a particular configuration will A decrease as the true aispeed increases. B decrease as the true airspeed decreases. C remain the same regardless of altitude. Comment Almost Correct: True airspeed increases for a given indicated airspeed as altitude increases. Correct: As altitude increases, the density of air molecules decreases, this affects both the indicated airspeed and the stall speed in the same way. GL01-05 What causes an airplane (except a T-tail) to pitch nosedown when power is reduced and the controls are not adjusted? A The CG shifts forward when thust and drag are reduced. B The downwash on the elevators from the propeller slipstream is reduced and elevator effectiveness is reduced. C When thrust is reduced to less than weight, lift is also reduced and the wings can no longer suport the weight. Incorrect: Only relocating weight (e.g. moving something from the back seat to the front seat) can shift the center of gravity. Correct: The propeller slipstream makes additional wind across the tail, so the downward force on the elevator is reduced when power is reduced -- this pitches the nose down. On a T-tail, the elevator is up higher and up out of the propeller slipstream a bit more. Incorrect: Thrust balances drag, not weight Joseph J. Zubay 09/21/15 Page 1 of 8 Pages

2 GL01-06 What effect does increased load factor have on an airplane during an approach to a stall? A The airplane will stall at a higher airspeed. B The airplane will have a tendence to spin. C The airplane will have a tendency to yaw and roll as the stall is encountered. Correct: More load factor means more lift is needed from the wing, so a higher angle of attack is needed to provide this lift at any given airspeed. This results in the wing being closer to the critical angle of attack at all airspeeds. As the airplane is slowed, a greater angle of attack is required to maintain altitude. A lightly loaded wing can be slowed much more than a heavily loaded wing before it reaches the critical angle of attack. Incorrect: An airplane has no tendency to spin under any load factor condition until after it is stalled. GL01-07 What determines the longitudinal stability of an airplane? A The location of CG with respect to the center of lift. B The effectiveness of the horizontal stabilizer, rudder, and rudder trim tab. C The relationship of thrust and lift to weight and drag. Correct: As the CG moves forward, farther from the center of lift, the tail of the airplane is required to produce a larger down force (horizontal stabilizer & elevator or stabilator). This results in more longitudinal stability, (fore and aft tipping) because a minor change in airspeed caused by a small climb or descent will be quickly counteracted by the tail of the airplane which is operating at a high angle of attack. Incorrect: These relationships have nothing to do with stability Joseph J. Zubay 09/21/15 Page 2 of 8 Pages

3 GL01-10 In what flight condition is torque effect the greatest in a single engine airplane? A Low airspeed, high power, high angle of attack. B Low airspeed, low power, low angle of attack. C High airspeed, high power, high angle of attack GL01-12 As you maneuver an airplane you should realize that it can be stalled A only when the nose is high and the speed is low. B only when the airspeed decreases to the published stalling speed. C at any airspeed and in any attitude. Correct. Incorrect. Incorrect: High airspeed and power go together, but would be a low angle of attack. Correct: Stall comes from an excessive angle of attack (greater than the critical angle of attack which was designed into the airfoil), one can make that happen at any airspeed and at any aircraft attitude. GL01-13 To counteract the effect of torque in a conventional single-engine propeller driven airplane, a pilot would normally add: A Left rudder pressure during the takeoff roll and while climbing with full power. B Right ruder pressure when entering a glide from level cruising flight. C Right rudder pressure during the takeoff roll and while climbing with full power. Correct: Torque, like P-factor, wants to yaw the airplane towards the left, so right rudder corrects this yaw Joseph J. Zubay 09/21/15 Page 3 of 8 Pages

4 GL01-15 During a spin to the left, which wing(s) are stalled? A Both wings; in a well developed spin, the inside wing is fully stalled, and the outside wing is less stalled. B Neither wing is stalled. C Only the left wing is stalled. Correct: Both wings are stalled in a spin. Almost Correct: The left wing is more stalled -- but both wings are stalled. Additional Questions to prepare for Class #3 X301 What makes an airplane turn? A Application of the rudder in the desired direction. B The horizontal component of lift while in a bank. C Continued use of the rudder and ailerons throughout the turn. X302 In most airplanes, where is the Center of Gravity relative to the Center of Lift from the wings? A The CG and the center of lift are aligned, ideally. B The CG is behind (aft of) the center of lift C The CG is ahead (forward) of the center of lift. Incorrect: The rudder will yaw, (point the front of the plane left or right), in a particular direction, but pressing on the rudder alone results in a sideways motion of the plane, (a skid). Correct. Incorrect: In most turns, the ailerons and rudder are relaxed once the bank is entered. Correct: The CG, or balance point, of the plane is forward of the center of lift, this requires a downward-facing lift from the tail for the plane to fly level Joseph J. Zubay 09/21/15 Page 4 of 8 Pages

5 X303 Which way does the horizontal stabilizer provide lift and why? A Downward to bring the nose back to level by counter the main wing's lift that is being applied from behind (aft of) the CG. B Upward, to help keep the plane up in the air and hold up the tail. C Neutral, the stabilizer does not normally give lift, but only gives up and down control. Correct: The main wing's lift is applied aft of the CG which would pitch the tail up (nose down) if not counterbalanced by a downared lift from the tail. So the horizontal stabilizer needs to "press down" on the tail to keep the plane level. X304 Why is it desirable for the root of the wing to stall before the tip of the wing? A Because this allows the slowest possible stall speed, since the root of the wing carries less weight than the outer parts of the wing. B When the root of the wing stalls first, the pilot can feel Correct. the onset of the stall while the ailerons still have some control effect for roll, allowing better control while the pilot can correct the stall. C It's not, airplane designers go to great lengths to have the wing stall equally along its length to "get the most" out of the wing. Incorrect: Roll control is important even when lift is compromised by an aerodynamic stall Joseph J. Zubay 09/21/15 Page 5 of 8 Pages

6 X003 What is the height of the troposphere at the equator and at the poles? A. 50 miles at both the equator and the poles B. Higher at the warm equator, 55,000' to 65,000', lower at the cold poles: 25,000'-30,000'. C. Higher at the poles, 55,000' to 65,000', lower at the equator: 25,000'-30,000'. Correct: See AC 00-06A, pg 3, due to the uneven heating from the sun, the troposphere is higher at the warm equator and lower at the cold poles. X004 Compare the advice on pg 4, AC 00 06A, with the FAA rules (FAR (a)) about supplemental oxygen use when flying at 11,000 feet. A. Auxiliary oxygen is mandatory over 10,000'. B. Auxiliary oxygen is not required at 11,000' but may be a good idea, especially if one will be flying there for awhile. C. Auxiliary oxygen should be used over 10,000', but the pilot should watch for drowsiness from the oxygen. Correct: The regulations do not require supplemental oxygen at 11,000'. But it is a good idea to watch out for the signs of hypoxia, especially above 10,000', or even lower altitudes at night, we will cover this more a few sessions later Joseph J. Zubay 09/21/15 Page 6 of 8 Pages

7 Homework Questions to prepare for Class #3 1. There are three types of parasite drag: form drag, interference drag, and skin friction drag. Streamlining decreases form drag, and design features, such as wheel fairings and retractable landing gear, can reduce both form and interference drag. Skin friction drag can be minimized by eliminating protruding rivet heads, and employing a clean glossy flat finish to airplane surfaces. 2. Induced drag is caused by the creation of wingtip vortices formed as the wing is generating lift. As the air pressure differential between the upper and lower surfaces of the wing becomes greater with an increase in angle of attack, stronger vortices are formed and induced drag is increased. Since the wing is usually at a low angle of attack at high airspeeds, and a high angle of attack at low airspeeds, a relationship between induced drag and speed can be observed. Induced drag is inversely proportional to the square of the speed. 3. Less than one wingspan. 4. True. 5. For stall recovery: Decrease the angle of attack to less than the critical angel of attack. Smoothly apply maximum power. Once the airplane recovers, adjust the power as necessary while maintaining coordinated flight. 6. For spin recovery: Throttle to idle. Neutralize the ailerons. Determine the direction of rotation. Apply full opposite rudder. Briskly move elevator to neutral or a bit forward of neutral to assure the angle of attack (AOA) is less than the critical AOA. As rotation stops, neutralize the rudder. Gradually apply aft elevator (or stabilator) to return to level flight without exceeding the critical angel of attack. 7. Low airspeed, high power settings, and high angles of attack. 8. Left turning tendencies are usually corrected for by the designer/manufacturer, in part, by the offset vertical stabilizer, offset mounting of the power plant and the increased angle of incidence of the left wing. 9. When an airplane is banked, lift is comprised of two components a vertical component and a horizontal component. The airplane turns because the horizontal component of lift creates a force directed inward toward the center of the turn. 10. Decrease airspeed. 11. a. 59 knots. b. 66 knots. c.110 knots Joseph J. Zubay 09/21/15 Page 7 of 8 Pages

8 12. True 2014 Joseph J. Zubay 09/21/15 Page 8 of 8 Pages