1. Presented by Skip Seila FAASTeam Lead Rep.
Propellers - 101
Presented by
Skip Seila
FAASTeam Lead Rep.

2. The propeller, though most reliable, is still probably the single most neglected component on an aircraft.

3. What is really unusual?
Nope, not this
Not this, either
Hmmm. Give up?

4. What is highly unusual is the fact that the engine is still in the aircraft. In the majority of cases, this scenario will result in fatalities!

5. On takeoff, propeller tip speeds approach the speed of sound
On takeoff, propeller tip speeds approach the speed of sound. The blades must absorb not only the punishing vibration of the engine’s power pulses, but also vibration caused by the oncoming airstream. Centrifugal loads – those forces that try to pull the blade out of the hub – amount to 10 to 20 tons per blade.

6. The blades twist and flex
The blades twist and flex. The stresses imposed on the prop are more concentrated in the small areas that are nicked or cut. These nicks and scratches act as stress risers, which can weaken the blade enough to eventually cause blade failure.

7. Non-Feathering Constant Speed Propellers – McCauley “Threadless”
* Takes oil pressure to change pitch.
* If it has a large snap ring at the base of the blade – it is a “threadless”.
* Only lubricated
at overhaul.

8. Non-Feathering Constant Speed Propellers – McCauley “Threadless”
* The retainer (2 ea.) on the left are put in place on the blade and the blade is then allowed to drop down in place. The blade “play” is then removed by installing shims under the large snap ring.

9. Non-Feathering Constant Speed Propellers – McCauley “Threadless”
* To inspect. Place the blade in the vertical position and with your thumb and forefinger on the tip, check for fore & aft movement.
* Movement of 1/8 “ is acceptable.
* If movement exceeds 1/8”, do not remove the propeller. It is repaired right on the aircraft.
* Excessive movement is not critical to flight. It diminishes at the first rotation of the propeller and is purely psychological.

10. Non-Feathering Constant Speed Propellers – McCauley “Threadless”
* If it has a small allen screw in the middle of the hub, it probably is “oil filled”.
* The oil has a red dye in it to detect early cracking in the hub.
* In order to prevent unwanted red dye indications when no possibility of cracking exists, it is highly recommended to dynamically balance the aircraft.

11. Full-Feathering Constant Speed Propellers
Hartzell

12. Full-Feathering Constant Speed Propellers - Hartzell
* Lubricated at 100 hr.
or annual inspection
with Aeroshell 5.
* Attains pitch change on initial start from oil pressure from the governor.
* Lack of oil pressure will result in feathering.

13. Full-Feathering Constant Speed Propeller - Hartzell
* This shows the propeller reaching the low pitch stop.

14. Full-Feathering Constant Speed Propeller - Hartzell
* This shows the propeller at the feathering stop.

15. Full-Feathering Constant Speed Propellers - Hartzell
* Here’s a close up view of the feathering stop that shows the elongated slots and the spring that from inertia allows the propeller to feather.

16. Full-Feathering Constant Speed Propellers - Hartzell
* This view shows the propeller in the feather position. However, the spring had to be cut for us to demonstrate the actions of this propeller. Seeing this spring as it really is should remove any doubt that this propeller will feather!

17. Propellers for Turbine Aircraft
Hartzell

18. Hartzell Turbine Propeller
* Lubricated at
100 hr./annual
inspections
with Aeroshell 6.
* Lack of oil press.
will result
in feathering.

19. Turbo Propellers

20. Lightweight Turbine – 2nd Generation
* Hartzell Compact Aluminum Hub off a Piaggio Aircraft.
* Raysbeck Aircraft
STC’s

21. The M-T Propeller

28. M-T Care & Maintenance
* Do not file leading edge. It’s stainless steel. If it is damaged, have it replaced. If discolored or stained, use a scotch brite pad.
* Do not wash it but keep it well waxed. Auto wax is fine.
* Note that these bearings are lubricated at time of O/H only.

29. Propeller Governors

30. Propeller Governors * Simply put – it is a high pressure oil pump.
* An inertia flywheel maintains the setting that you made in the cockpit.

31. Propeller Governors
* Notice that the tear-drop arm has moved allowing the flywheel arms to come into play and regulate the oil pressure flow to the propeller and thus regulating the pitch of the propeller.
* IT’S AN OIL PUMP !

32. Propeller Care and Maintenance

33. Proper Care and Maintenance
* File the leading edges of the blades with a fine file. No rasp or coarse file!
* Do not use the shank of a screw driver for burrs. That only rolls the metal back in and does nothing to prevent further damage.
* Do not wash propeller. Wipe it clean and
finish with a clean oily rag.
Keep in mind that to pass overhaul requirements, blades are measured on width and thickness. Blades are expensive.

34. Proper Care and Maintenance
* Burrs or nicks (stress risers) on leading or trailing edges must be repaired by using the formula of 10X the depth of the damaged area to determine the necessary area required to be repaired.
* Start with a file, then emery cloth and then crocus cloth to remove all file marks

35. Proper Care and Maintenance
* Check to assure that the spinner is not touching the blades.
* Check that the flyweights (if installed) are not touching and damaging the spinner.
* Check for blade play at the tip by fore and aft movement, in and out movement and twist movement. Slight play is okay if the blade returns to it’s original position.
* Check for grease leaks.

36. Proper Care and Maintenance

37. Propeller Care and Maintenance

38. Proper Care and Maintenance
* To “store” your propeller properly after flight:
2 bladers – horizontally.
3 bladers – 2 up and 1 straight down.
4 bladers – 2 up and 2 down.
- Storage in this manner prevents rain or moisture from settling in the cavity at the base eliminating the opportunity for moisture to seep in and case corrosion or destroy the affectivity of any lubrication.

39. Proper Care and Maintenance
* Stay out of tall grass. It’s not a lawnmower.
* It’s not to be used as a tow bar. Do not use the
propeller tip to move the aircraft!
* Stay away from water puddles. Why? Ever notice the vortexing when running up over water? The blades are so thin that one tip may decide to go to one side while the other blade tip takes to the other side and now the prop is out of track. Avoid the vortex scenario. This can be real costly.

40. Proper Care and Maintenance
* Note: A.D Lycoming Engines
Change in definition of propeller strike or
sudden stoppage.
“(3) A sudden RPM drop while impacting water, tall grass, or similar yielding medium
where propeller damage is not normally
incurred.”

41. Overhaul Periods * Hartzell Service Letter-----HC-SL-61-61Y
“Propeller – Overhaul Periods and Service
Life Limits for Hartzell Propellers,
Governors, and Propeller Damper
Assembllies”.
* McCauley Service Bulletin SB137Y----”Revised
time between overhaul (TBO) specifications”.

42. Overhaul Periods * Notice there is no “recommended” in there anywhere.
* If you exceed or go past the TBO limits,
you are all alone with no back-up or
support.

43. Dynamic
Propeller
Balancing

44. Dynamic Propeller Balancing
* Understand Basics of Vibration
* Understand the Benefits of Balancing
* Understand Fundamentals of Dynamic Propeller Balancing

45. Dynamic Propeller Balancing Definition
For the purpose of Propeller Balance, vibration can be described as: “the unwanted, unproductive, cyclic oscillation of the propeller and engine assembly about its rotational axis.”
For the purpose of Propeller Balance, vibration can be described as the unwanted, unproductive, cyclic oscillation of the propeller and engine assembly about its rotational axis.

46. Dynamic Propeller Balancing
* Understand that any imbalance at the center of rotation amplifies itself as it travels out to the tip of the propeller. The tips being thin vibrate augmenting the vibration and also show a lose in efficiency.

47. Dynamic Propeller Balancing Vibration-Related Complaints
* Passenger complaints of noise in the cabin
* Cracked exhaust stacks and sheet metal
* Higher than normal occurrence of engine and prop oil leaks and light bulb failures
* Physical movement of airframe (buzz in the seat, yoke, rudder pedals)
* Malfunctioning or failed avionics

48. Dynamic Propeller Balancing How It Is Measured
* The vibration sensor generates a small voltage when the mass compresses the piezoelectric element. That voltage is proportional to the force being exerted on the element.

49. Dynamic Propeller Balancing How It Is Measured
* Engineering Units
Mils (0.001 inches) - displacement
IPS (Inches Per Second) - velocity
gs (equivalent gravities) - acceleration

50. Dynamic Propeller Balancing Equipment Required
* A device to collect vibration and phase data.
* A phase angle /speed sensing device
* A vibration sensing device
* Accessories: Cables, balance weights, hand tools.

51. Dynamic Propeller Balancing Data Collection & Processing
* The vibration sensor is installed on the engine as near the front bearing as possible. The Phototach is mounted on the cowling, behind the propeller. The reflective tape is applied to the back side of the target propeller blade in line with the Phototach beam. The mass is located by the relative occurrence of tach trigger and mass passage at the radial sensor location.

52. Dynamic Propeller Balancing The Balancing Process
* With the equipment installed and all previously installed trim weights (not static weights) removed, head the airplane into the wind (10 kts maximum) and begin the data collection.

53. Dynamic Propeller Balancing Data Collection & Processing
* As the heavy spot on the propeller passes the location of the vibration sensor, the sensor generates and sends an electrical pulse to the analyzer. The Reflective tape triggers a response as it passes the Phototach, which then sends an electrical signal to the analyzer.

54. Dynamic Propeller Balancing Data Collection & Processing
* When sufficient data has been collected, the process is stopped by the operator and the averaged data displayed on screen. Notice that you have the option to Retake the data if desired.

55. Dynamic Propeller Balancing Data Collection & Processing
* A solution is then provided by the instrument based on a stored influence coefficient or a calculated test weight. If required, the process is then repeated for refinement of the solution.

56. Dynamic Propeller Balancing The Balancing Process
* Where to place the weights
Test weights can be placed under the spinner retention screws. It may be necessary to use longer screws for the test weights. If doing so, account for the delta between the normal and the longer screw. Be sure you are measuring the angles in relation to the sensor or tape as you specified in the setup being used.

57. Dynamic Propeller Balancing The Balancing Process
Permanent weights may be installed under the flange or on the bulkhead. If installed under the flange, offset from spinner attaching screws by four times the diameter of the spinner screws.

58. Dynamic Propeller Balancing
* There is no difference in the propeller balance procedure for a radial engine, opposed engine, turboprop, geared, variable pitch, or fixed pitch propeller.

59. Dynamic Propeller Balancing
* Remember that dynamic balancing will prolong the life of the engine, propeller, airframe and avionics.
* Before dynamic balancing and right after propeller installation, it is best to put a few flight hours or good high end runs on it first. This will allow the blades to take their “set” and eliminate the need to re-do the balancing later on.

60. Dynamic Propeller Balancing
* Remember that when dynamic balancing you are balancing from the engine mounts forward.
* Dynamic balancing is not a “cure all”, as it can not compensate for gear doors that do not close properly, worn control surface rod ends, beta rings not exact, etc.
* It is becoming the professional opinion that all engines with propellers should be done.

61. Quick Question
* You spend countless hours, phone calls, referrals, and do whatever you feel necessary in selecting an overhaul facility for your engine. How much time do you take to select a propeller overhaul facility? All too often, not nearly enough and yet the ramifications can be extremely costly, if not deadly.

62. Safety Advisor Technology No.3
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PROPELLER SAFETY
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Safety Advisor Technology No.3

63. Thanks so much for your time and if you would like to contact me, please do so at skiptpa@aol.com