1. Presented to: CFI Workshops By: The FAASTeam Date: January 1, 2012 Federal Aviation Administration Downloaded from www.avhf.com CFI Workshop 6 Core Topic 12 Airworthiness Limitations Where do they Really come from?

2. 2 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 You can’t beat the laws of Physics 1 June 2010, 1705 hrs, Anchorage, AK Pilot –age 33 –Commercial, single-engine land & sea –1718 hours TT, 81 hours make & model Phase of flight –Takeoff / climb out

3. 3 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 You can’t beat the laws of Physics Aircraft –Cessna 1976 U206F –Souls on board – 5 –Maximum allowable take off weight - 3,600 Lbs. –Empty weight – 2165.5 –Useful load – 1434.5 –Fuel, occupants, & cargo weight – 2092.7 Pilot’s estimate – 1,400 – 1,450 Lbs –Takeoff weight – 4258.2 658 over max & 3.95 – 8.22 In. aft of cg limit

4. 4 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 You can’t beat the laws of Physics http://dms.ntsb.gov/aviation/AccidentReports/v233vt4542baswfpmqymx q451/R07052011120000.pdf

5. 5 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Where do limitations Come From? Physics –Example: The maximum rate of climb that an airplane is capable of is governed by the forces on it. Wing area, power, and thrust all influence the rate of climb. –Violating limitations imposed by physics typically results in bent metal. Regulation –Establishes legal limitations based on the rules that the airplane was certified under. –Regulatory limitations are based on physics, but usually have a safety factor added. –Example: 23.65 says “Each normal, utility … must have a minimum climb gradient of at least 8.3 % for land planes or 6.7 % for seaplanes…… “ (at maximum gross weight)

6. 6 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 We’ll discuss: –Weight and c.g. limitations –Landing and Take off performance –Stall Speed –Airspeed limitations –Power Plant limitations –How Floats affect limits –How Skis affect limits

7. 7 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Airspeed Limits

8. Federal Aviation Administration 8 FAASTeam CFI Workshop 6 January 2012 Examples of Airspeed Limits -

9. Federal Aviation Administration 9 FAASTeam CFI Workshop 6 January 2012 Examples of Airspeed Limits Flaps Down Stall Speed (at gross weight) -

10. Federal Aviation Administration 10 FAASTeam CFI Workshop 6 January 2012 Examples of Airspeed Limits Flaps Up Stall Speed (at gross weight) Flaps Down Stall Speed (at gross weight) -

11. Federal Aviation Administration 11 FAASTeam CFI Workshop 6 January 2012 Examples of Airspeed Limits Flaps Up Stall Speed (at gross weight) Flaps Down Stall Speed (at gross weight) - Vne, Never Exceed

12. 12 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Flutter testing http://www.dfrc.nasa.gov/gallery/movie/PA-30/HTML/EM-0098-01.html

13. 13 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Flutter testing Tail Flutter Test.mov

14. 14 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 What’s the consequence of operating above VNE? A. Catastrophic airframe failure B. Unknown & untested C. Irreversable airframe stress VNE

15. Federal Aviation Administration 15 FAASTeam CFI Workshop 6 January 2012 Examples of Airspeed Limits Flaps Up Stall Speed (at gross weight) Flaps Down Stall Speed (at gross weight) - Vne, Never Exceed

16. Federal Aviation Administration 16 FAASTeam CFI Workshop 6 January 2012 Examples of Airspeed Limits Flaps Up Stall Speed (at gross weight) Flaps Down Stall Speed (at gross weight) Vf, Max Flap Extension Speed - Vne, Never Exceed

17. Federal Aviation Administration 17 FAASTeam CFI Workshop 6 January 2012 Examples of Airspeed Limits Flaps Up Stall Speed (at gross weight) Flaps Down Stall Speed (at gross weight) Vf, Max Flap Extension Speed - Vc, cruise speed Vne, Never Exceed

18. Federal Aviation Administration 18 FAASTeam CFI Workshop 6 January 2012 The Operating Envelope (V-n Diagram) n, g Speed, V o 1 Va, Maneuvering Speed Vne (red line) Vd (Dive Speed) 3.8 g (Normal category Gust Lines 50 fps gust 25 fps gust 10% safety margin Vc (bottom of Yellow arc) Stall Line Vne (red line)

19. 19 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 The Operating Envelope (V-n Diagram) n, g Speed, V o 1 Vd (Dive Speed) 3.8 g (Normal category) Vne (red line) 10% safety margin

20. 20 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 The Operating Envelope (V-n Diagram) n, g Speed, V o 1 Vne (red line) Vd (Dive Speed) 3.8 g (Normal category Gust Lines 50 fps gust 10% safety margin

21. 21 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 The Operating Envelope (V-n Diagram) n, g Speed, V o 1 Vne (red line) Vd (Dive Speed) 3.8 g (Normal category Gust Lines 50 fps gust 10% safety margin Vc (bottom of Yellow arc) 25 fps gust Stall Line

22. 22 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 The Operating Envelope (V-n Diagram) n, g Speed, V o 1 Vne (red line) Vd (Dive Speed) 3.8 g (Normal category Gust Lines 50 fps gust 10% safety margin Vc (bottom of Yellow arc) 25 fps gust Stall Line Va, Maneuvering Speed

23. 23 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Airspeed Limits V a is the design maneuvering airspeed at which the airplane will be able to do a limit maneuver without stalling. (3.8 g for normal category airplanes)

24. 24 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Airspeed Limits - True or False 1. The bottom of the Yellow arc is the airspeed above which the airplane is at risk of damage from a 50 fps gust. True and gusts in excess of 25 fps are common. 2. If the Air is turbulent, Slow down to below the yellow arc. Also true. Operating in the yellow arc with any turbulence is very stressful to the aircraft. 3. If an airplane has been flown in severe turbulence above V C, additional inspection should be conducted. That’s true damage associated with severe turbulence is common. 4. The installation of larger engines makes it less likely that a pilot will be able to fly well into the yellow arc. False – Larger engines make it easier to fly too fast for conditions

25. 25 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 5. Vne is set by structural considerations as well as flutter. That’s true. Vne is determined with respect to structural considerations as well as flutter. 6. Flutter is very sensitive to slop in control systems and to the balance of the control surfaces. The airplane is certified to V d which is 10% over V ne. This is also true. A light coating of frost was enough to cause aileron flutter on a CE – 210 in Virginia. The aileron was torn from the airframe but luckily the pilot was able to land successfully. If it had been tail flutter the outcome would have been much worse. 7. The ASI on most GA aircraft is accurate enough to operate right up to Vne. Maybe true maybe false. It depends on the health of your pitot/static system & ASI. The question is though – are you willing to bet your life on it? Airspeed Limits - True or False

26. 26 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 As gross weight decreases Va will: A. Decrease B.Remain the same C.Increase Extra Credit

27. 27 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Weight & Balance Limitations

28. 28 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 The forward C.G. limit is critical for: A. Nose wheel strength B.Ability to flare C.Stall recovery C.Tail strength Center of Gravity

29. 29 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012

30. 30 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Examples of Weight and Balance Limits Typically based on climb, strength Nose Gear limits, ability to flare, trim Tail gear structural limit, stick forces going to zero, spin resistance, longitudinal stability, can’t push fwd on balked landing Horizontal Tail Strength, Ability to flare, Nose Gear (Center of Gravity) (weight)

31. 31 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Weight Limits – True or False 1. Maximum gross weight is selected early in the design of most airplanes and the rest of the airplane is designed around that number. Yes – that’s true. 2. Exceeding maximum gross weight routinely can result in fatigue problems. You bet – exceeding max gross weight – even by a little bit will result in fatigue problems. As the fleet ages we’re seeing more of this. 3. Exceeding maximum gross weight results in lower climb rates and can result in structural failure. Well duh – of course we’re going to climb slower but the insidious thing is the possibility of structural failure. 4. When exceeding Max Gross Wt. Stall speed goes up, controllability can be reduced, ability to maneuver without entering an accelerated stall can be reduced. Yes this is all true when you exceed weight limits.

32. 32 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 5. Structural limits have a 1.5 margin of safety built into them for unexpected conditions, and to minimize the chances of having fatigue problems, not because you really wanted to carry that much stuff. See the second statement above (Exceeding maximum gross weight routinely can result in fatigue problems). The safety margin is there for a reason and the reason is not so you can overload by 50%. 6. Contrary to rumors, airplanes are not generally capable of taking a lot more than the required loads. (In many if not most cases, the existing gross weight limit is set because of a failure in the static test program. This is sobering. In many cases the max gross weight limit was set because the airframe came apart in static testing. Weight Limits – True or False

33. 33 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Forward c.g. limit The forward center of gravity limit (and the angled limit if present) are typically critical for: –Ability to flare during landing. –Ability of the horizontal tail to take the structural loads. –Nose gear loads. The installation of heavier engines often makes airplanes nose heavy and subject to violating the forward limit.

34. 34 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Aft C.G. Limit The aft center of gravity is usually critical for: –Spin recovery –Stick forces –Balked landing –Longitudinal and directional stability –Nose down trim –Tail Wheel Loads

35. 35 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Takeoff Performance Takeoff performance numbers are generated by an experienced flight test pilot with a lot of time in the airplane simulating an average pilot with a new engine. They are often optimistic with respect to what can be expected in the field. There is no Margin of Safety incorporated into the published takeoff numbers! AOPA recommends that pilots add 50% to published takeoff distances.

36. 36 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Can I get out of that strip with the moose??? Piano or other heavy object ………. Don’t Fly above Gross Weight!! Don’t guess – weigh it! Al Hikes Photo

37. 37 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Can I get out of that strip with the moose??? Example: PA-18-150 with stock prop –Flight manual says that the take off run is 200 ft (500 over 50’ obstacle) at 1750 lb. –What is the take off distance at 2000 lb? (I assume you have the one ton STC…..) WeightGround Run50’ Obstacle 1750200500 2000260650 Not including AOPA 1.5 safety factor

38. 38 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 WeightGround Run50’ Obstacle1.5 Safety Factor 1750200500300/750 2000260650390/975 Can I get out of that strip with the moose???

39. 39 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Take off wind issues Head winds decrease takeoff distances. For a head wind of 10 % of the take off speed, the take off distance will be reduced 19%. (Roughly) A tail wind of 10 % of the take off speed will increase your take off distance by 21%. A cross wind will increase your take off distance. (More drag from control surfaces and even a direct cross wind has a headwind component in the crab)

40. 40 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Tail Wind Example C-172 sea level 20 deg C short field, hard surface ground roll 980 ft. 51 knot lift off speed. Consider a 5 kt tail wind (10% of lift off speed) 980 x 1.21 = 1186 ft. Cessna handbook calculation is 10% for every 2 knots for the 172. That results in a distance of 1225 ft. A little more conservative than the Axioms of flight estimate.

41. 41 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Crosswind The maximum demonstrated cross wind component is?

42. 42 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Crosswind The maximum demonstrated cross wind component is: The highest cross wind component demonstrated during flight testing. –The ability to handle a cross wind is highly dependent on pilot and runway conditions. (Especially in gusty conditions) –There is a point at which the airplane runs out of available aileron and/or rudder deflection. –When the controls are at their stops, pilot ability no longer matters. –14 CFR part 23.233 requires that all airplanes be able to land in a cross wind up to.2 times flaps up stall speed. –For a C-172 the minimum required is 44 kts x.2 = 8.8 knots (The 172 exceeds the minimum required)

43. 43 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Discussion: What minimums do you set for your students? How do you teach them to evaluate their performance and adjust personal minimums to reflect their ability?

44. 44 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Alaskan Off-airport Operations Guide

45. 45 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 My Short Field Performance Aircraft ___________ Gross Weight ___________ Test Weight_________ Airfield ___________ Elevation ___________ Density Altitude ________ Wind Direction _______ Wind Speed _______ X Wind Component ______ Indicated Approach Speed ___________ Flap Setting ____________ Landing Distance _____________ Takeoff Flap Setting __________ Rotation Speed __________ Rotation Speed x.70 __________ Vx __________ Vy __________ Distance to Rotation __________ Distance to 50 feet AGL ___________

46. 46 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Engine Limitations

47. 47 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Engine Limitations RPM –Engine RPM limits are established to ensure that the engine will probably make TBO without catastrophic failure (Wear out before fracture) –Some flat pitch propellers are capable of exceeding the engine red line rpm during takeoff or climb. Allowing this to occur routinely can dramatically reduce the life of the engine or lead to premature catastrophic engine failure. –Yellow arc on Tachometer and “avoid continuous operation” ranges are usually present because of a vibration problem in the propeller engine combination. Poor TAC calibration can result in inadvertent operation in these ranges resulting in propeller failure or crankshaft failure.

48. 48 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Engine Limitations Temperature –Temperature limits are established to avoid break down of oil, excessive heat damage of internal parts (like pistons) or cracking due to thermal stresses. –There are often telltales on the engine that will indicate that an engine has been over temped. –While low temperature limits are not usually established, operating at low oil temperatures can result in poor oil flow through oil coolers, water contamination in the oil and resulting internal corrosion.

49. 49 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Some notes on Professionalism Walk the talk. Don’t let your students see you do anything you don’t want them to do in a week or so. Have your students brief on limitations before flight – don’t just hop in and go. If it’s not important to you it’s not important to your students.

50. 50 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Float Flying considerations Floats generally reduce the directional stability of an airplane in flight. As a result, many float installations require additional vertical tail area (i.e. ventral or dorsal fins) Additional drag created by the floats often means lower climb rates. This is reflected in the lower requirements for float planes. Sometimes the lower climb requirement is taken advantage of by increasing the maximum gross weight when float equipped. CAR 3 requires that the airplane remain afloat with 2 compartments flooded. (Not necessarily up right) Floats are rated by buoyancy. To get the maximum aircraft weight that a set of float will support take the float number (i.e. EDO 2000) and divide by.9. (EDO 2000 floats can support an aircraft weight of 2000/.9 = 2222 lb)

51. 51 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Ski Plane Considerations Take off performance under ideal conditions (hard packed snow/ice) are estimated to be 20% longer (C-180 manual) Take off distance is highly pilot technique dependant. Deep snow can make takeoff distance infinite…….. For ski installations, the maximum speed of the airplane, Vne, sometimes decreases due to ski dump and/or dynamic issues. Problems have been encountered with steel springs interacting with spring steel landing gears (i.e. Cessna and Citabria landing gears)

52. 52 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Questions?

53. 53 Federal Aviation Administration FAASTeam CFI Workshop #2 January 2011 QUIZ

54. 54 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 A. As long as the 10% margin of safety is not exceeded. B. Turbulence is no greater than moderate C. Neither A nor B Question 1 Flying above the red line is permissable:

55. 55 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 A. All control surfaces have been balanced. B. Turbulence is no greater than moderate C. No turbulence is present Question 2 Flying within the yellow arc is permissable as long as:

56. 56 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 A. Compromise stall recovery. B. Lighten pitch control forces C. Place greater stress on the nose wheel. Question 3 A forward center of gravity will:

57. 57 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 The aft C.G. limit is critical for: A.Tail wheel strength B.Spin recovery C.Nose wheel strength Question 4

58. 58 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Exceeding the max gross weight limit will: A.Improve takeoff and climb performance B.Cause undue stress to the aircraft C.Cause fatigue problems Question 5

59. 59 Federal Aviation Administration FAASTeam CFI Workshop #2 January 2011 NOW THE ANSWERS

60. 60 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 A. As long as the 10% margin of safety is not exceeded. B. Turbulence is no greater than moderate C. Neither A nor B Question 1 Flying above the red line is OK:

61. 61 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 A. All control surfaces have been balanced. B. Turbulence is no greater than moderate C. No turbulence is present Question 2 Flying within the yellow arc is OK as long as:

62. 62 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 A. Compromise stall recovery. B. Lighten pitch control forces C. Place greater stress on the nose wheel. Question 3 A forward center of gravity will:

63. 63 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 The aft C.G. limit is critical for: A.Tail wheel strength B.Spin recovery C.Nose wheel strength Question 4

64. 64 Federal Aviation Administration FAASTeam CFI Workshop 6 January 2012 Exceeding the max gross weight limit will: A.Improve takeoff and climb performance B.Cause undue stress to the aircraft C.Cause fatigue problems Question 5

65. 65 Federal Aviation Administration FAASTeam CFI Workshop #2 January 2011 END OF CFI WORKSHOP MODULE 6