Fan Case Reinforcement in a Gas Turbine Jet Engine

• US 20080199301A1
• Filed: 09/20/2005
• Published: 08/21/2008
• Est. Priority Date: 09/23/2004
• Status: Active Grant

• Current Assignee: Carlton Forge Works
• Original Assignee: Carlton Forge Works
• Inventors: Cardarella Jr, L. James
• Granted Patent: US 8,454,298 B2
• Time in Patent Office: Days
• US Class Current: 415/9
• CPC Class Codes: F01D 21/045 special arrangements in stators or in rotors dealing with breaking-off of part of rotor
• CPC Class Codes: F02K 3/04 the plant including ducted fans, i.e. fans with high volume, low pressure outputs, for augmenting the jet thrust, e.g. of double-flow type
• CPC Class Codes: F02K 3/06 with front fan
• CPC Class Codes: F04D 25/16 Combinations of two or more pumps ; Producing two or more separate gas flows
• CPC Class Codes: F05D 2230/40 Heat treatment
• CPC Class Codes: F05D 2300/133 Titanium
• CPC Class Codes: F05D 2300/433 Polyamides, e.g. NYLON
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft
• CPC Class Codes: Y10T 29/4932 Turbomachine making
• CPC Class Codes: Y10T 29/49865 by temperature differential [e.g., shrink fit]

Abstract

Described is reinforcement of a fan case in a gas turbine jet engine. In one embodiment, a containment ring and a heat resistance ring are shrink interference fit on the inside diameter of the fan case, the containment ring where the large fan blades turn, and the heat resistance ring where heated air from backfiring heats up the fan case. In one example, the containment ring is made of a super alloy to provide added strength to the fan case should a fan blade break, containing the fan blade within the fan case. The heat resistance ring is made of titanium or other suitable material. Additionally, one or more stiffener rings may be shrink interference fit on the outside diameter of the fan case. The containment ring and stiffener rings can reduce the flight weight of the fan case and lower the material costs, while increasing the containment strength of the fan case. Other embodiments are described and claimed.

Claims

1. A method, comprising:

encircling an outer circumferential surface of one of a containment ring and a fan case of a gas turbine jet engine, using an inner circumferential surface of the other of the containment ring and the fan case of a gas turbine jet engine; and

applying radially compressive forces to said outer circumferential surface along the length of the circumference of said inner circumferential surface using said encircling inner circumferential surface.

2. The method of claim 1 wherein said radially compressive force applying includes shrink interference fitting said containment ring to said fan case.

3. The method of claim 1 wherein said radially compressive force applying includes seating said containment ring within a notch defined by said fan case and shaped to secure said containment ring against displacement in a direction longitudinal to said fan case.

4. The method of claim 1 wherein said fan case surrounds a fan adapted for rotation within said fan case along an axis of rotation to provide air intake and thrust, wherein said radially compressive forces are directed to a center located on said axis of rotation.

5. The method of claim 1 further comprising machining a containment ring notch circumferentially into an inner surface towards a front end of the fan case;

and wherein said encircling and applying includes seating said containment ring in said containment ring notch through a shrink interference fit.

6. The method of claim 1 further comprising machining a containment ring notch circumferentially into an outer surface towards a front end of the fan case;

and wherein said encircling and applying includes seating said containment ring in said containment ring notch through a shrink interference fit.

7. A method according to claim 5 wherein said machining further comprises machining said containment ring notch into said inner surface of the fan case in a first direction, wherein a plurality of grooves are formed and aligned on said inner surface in said first direction.

8. A method according to claim 7 further comprising:

prior to said notch machining, forging said containment ring in one piece; and

machining said containment ring to a predetermined shape to match with said containment ring notch.

9. A method according to claim 8 wherein said containment ring is forged from a containment material in one piece wherein said material is selected from the group consisting of steel, titanium, nickel-base super alloy.

10. A method according to claim 8 wherein said containment ring machining further comprises machining an outer surface of said containment ring in a second direction, wherein a plurality of grooves are formed and aligned on said outer surface in said second direction;

wherein when said inner surface of said containment ring notch and said outer surface of said containment ring are seated together, said plurality of grooves on said inner surface of said containment ring notch and said plurality of grooves on said outer surface of said containment ring align in a cross-hatch manner to each other, increasing the frictional forces between said containment ring notch and said containment ring and reducing the potential for spinning of said containment ring within said containment ring notch.

11. A method according to claim 8 further comprising:

spot welding said containment ring to said containment ring notch in at least one location to retard said containment ring from spinning in relation to said containment ring notch.

12. A method according to claim 8 further comprising:

bolting said containment ring to at least one flange secured to said containment ring notch to retard said containment ring from spinning in relation to said containment ring notch.

13. A method according to claim 8 wherein said containment ring machining further comprises machining said containment ring with a reverse taper, wherein a first outside diameter of said containment ring at a first point towards a front end is less than a second inside diameter of said containment ring at a second point away from said front end.

14. A method according to claim 5 wherein said machining further comprises machining said containment ring notch with a reverse taper, wherein a first inside diameter of the fan case at a first point of said containment ring notch towards said front end is less than a second inside diameter of the fan case at a second point of said containment ring notch located away from said front end.

15. A method according to claim 5 wherein said seating further comprises;

heating the fan case to cause an inside diameter of said containment ring notch to increase to a second diameter that is larger than an outside diameter of said containment ring at an ambient temperature;

positioning said containment ring in said containment ring notch; and

allowing the fan case to cool to said ambient temperature, causing said containment ring notch to want to decrease from said second diameter toward said inside diameter, but resisted from doing so by said outside diameter of said containment ring at said ambient temperature, giving rise to said shrink interference fit.

16. A method according to claim 5 wherein said seating further comprises:

heating the fan case to cause an inside diameter of said containment ring notch to increase to a second diameter;

cooling said containment ring to cause an outside diameter of said containment ring to decrease to a second diameter, wherein said second diameter of said containment ring is smaller than said second diameter of said containment ring notch;

positioning said containment ring in said containment ring notch; and

allowing the fan case to cool to an ambient temperature causing said containment ring notch to decrease from said second diameter toward said inside diameter, and allowing said containment ring to warm up to said ambient temperature causing said containment ring to increase toward said outside diameter, giving rise to said shrink interference fit.

17. A method according to claim 5 wherein said seating further comprises:

cooling said containment ring to cause an outside diameter of said containment ring to decrease toward a second diameter, wherein said second diameter of said containment ring is smaller than an inside diameter of said containment ring notch;

positioning said containment ring in said containment ring notch; and

allowing said containment ring to warm up to said ambient temperature causing said containment ring to increase toward said outside diameter, but resisted from doing so by said inside diameter of said containment ring notch at said ambient temperature, giving rise to said shrink interference fit.

18. A method according to claim 5 further comprising:

machining at least one stiffening ring notch circumferentially into a surface of the fan case; and

seating a stiffening ring in said at least one stiffening ring notch, wherein said stiffening ring resists the fan case from going oval under a load and temperature conditions experienced during operation of the gas turbine jet engine.

19. A method according to claim 18 wherein said stiffening ring notch is machined in an outer surface of the fan case and said seating said stiffener ring further comprises:

heating said stiffening ring to cause a first inside diameter of said stiffening ring to increase to a second inside diameter that is larger than an outside diameter of said at least one stiffening ring notch at an ambient temperature;

positioning said stiffening ring in said at least one stiffening ring notch; and

allowing said stiffening ring to cool to said ambient temperature, causing said stiffening ring to decrease from said second inside diameter toward said first inside diameter, but resisted from doing so by said outside diameter of said at least one stiffening ring notch, giving rise to said shrink interference fit.

20. The method of claim 1 wherein said fan case is made of a first material having a first containment strength and said containment ring is made of a second material having a second containment strength higher than that of the first material.

21. The method of claim 20 wherein said first material is aluminum and said second material is a nickel-based super alloy.

22. The method of claim 18 wherein said fan case is made of a first material having a first strength and said stiffener ring is made of a second material having a second strength higher than that of the first material.

23. The method of claim 22 wherein said first material is aluminum and said second material is a nickel-based super alloy.

24. An apparatus for use in a gas turbine jet engine, the apparatus comprising:

a fan case having a front end and an inner surface and an outer surface towards said front end of the fan case wherein one of said inner and outer surfaces defines a containment ring notch machined circumferentially into said one fan case surface; and

a containment ring adapted to be seated in said containment ring notch to provide radially compressive forces applied from one of said fan case and said containment ring to the other of said fan case and said containment ring.

25. The apparatus of claim 24, wherein said containment ring is adapted to be seated through a shrink interference fit.

26. The apparatus of claim 25 wherein said containment ring notch is machined circumferentially into said fan case inner surface towards a front end of the fan case.

27. The apparatus according to claim 24 wherein said containment ring is forged from a containment material in one piece and is machined to a predetermined shape and wherein said material is selected from the group consisting of steel, titanium, nickel-base super alloy.

28. The apparatus according to claim 26 wherein an outside diameter of said containment ring is slightly larger than an inside diameter of said containment ring notch at an ambient air temperature, and the fan case is heated to cause said inside diameter of said containment ring notch to increase to a second diameter that is larger than said outside diameter of said containment ring, enabling said containment ring to be positioned in said containment ring notch giving rise to said shrink interference fit when the fan case cools to said ambient temperature.

29. The apparatus according to claim 28 wherein said containment ring notch is machined with a reverse taper such that a first inside diameter of the fan case at a first point towards said front end is less than a second inside diameter of the fan case at a second point away from said front end, and further wherein said containment ring is machined circumferentially on its outside surface to match said reverse taper.

30. The apparatus according to claim 26 wherein an outside diameter of said containment ring is slightly larger than an inside diameter of said containment ring notch at an ambient air temperature, and the fan case is heated to cause said inside diameter of said containment ring notch to increase to a second diameter, and said containment ring is cooled to cause an outside diameter of said containment ring to decrease to a second diameter, wherein said second diameter of said containment ring is smaller than said second diameter of said containment ring notch, enabling said containment ring to be positioned in said containment ring notch giving rise to said shrink interference fit when the fan case cools and said containment ring warms up to said ambient temperature.

31. The apparatus according to claim 26 wherein an outside diameter of said containment ring is slightly larger than an inside diameter of said containment ring notch at an ambient air temperature, and said containment ring is cooled to cause an outside diameter of said containment ring to decrease to a second diameter, wherein said second diameter of said containment ring is smaller than an inside diameter of said containment ring notch, enabling said containment ring to be positioned in said containment ring notch giving rise to said shrink interference fit when said containment ring warms up to said ambient temperature.

32. The apparatus according to claim 26 further comprising:

a plurality of grooves aligned in a first direction on a machined inner surface of said containment ring notch; and

a plurality of grooves aligned in a second direction on a machined outer surface of said containment ring;

wherein when said inner surface of said containment ring notch and said outer surface of said containment ring are interference shrink fit together, said plurality of grooves on said inner surface of said containment ring notch and said plurality of grooves on said outer surface of said containment ring align in a cross-hatch manner to each other, increasing the frictional forces between said containment ring notch and said containment ring and reducing the potential for spinning of said containment ring within said containment ring notch.

33. The apparatus according to claim 24 further comprising:

a spot weld in at least one location welding said containment ring to said containment ring notch to prevent said containment ring from spinning in relation to said containment ring notch.

34. The apparatus according to claim 24 further comprising:

at least one flange secured to said containment ring notch, wherein said containment ring is bolted to said at least one flange to retard said containment ring from spinning in relation to said containment ring notch.

35. The apparatus according to claim 24 further comprising:

at least one stiffening ring notch machined circumferentially into a surface of the fan case; and

a stiffening ring seated in said at least one stiffening ring notch, wherein said stiffening ring is seated through a shrink interference fit, wherein said stiffening ring resists the fan case from going oval under a load and temperature conditions experienced during operation of the gas turbine jet engine.

36. The apparatus according to claim 35 wherein said stiffening ring is forged from aluminum in one piece.

37. The apparatus according to claim 24 wherein said stiffening ring notch is machined into an outer surface of the fan case and an inside diameter of said stiffening ring is slightly smaller than an outside diameter of said at least one stiffening ring notch at ambient air temperature, and said stiffening ring is heated to cause said inside diameter of said stiffening ring to increase toward a second diameter that is larger than said outside diameter of said at least one stiffening ring notch, enabling said stiffening ring to be positioned in said at least one stiffening ring notch giving rise to said shrink interference fit when said stiffening ring cools to said ambient temperature.

38. The apparatus according to claim 24 wherein the fan case is forged from one of steel, titanium, and aluminum.

39. The apparatus according to claim 24 wherein the fan case is manufactured from one of steel, titanium, and aluminum.

40. The apparatus according to claim 24 wherein the fan case is manufactured from a composite material.

41. The apparatus according to claim 40 wherein an outside diameter of said containment ring is slightly larger than an inside diameter of said containment ring notch at an ambient air temperature, and said containment ring is cooled to cause said outside diameter of said containment ring to decrease to a second diameter that is smaller than said inside diameter of said containment ring notch, enabling said containment ring to be positioned in said containment ring notch giving rise to an interference fit when said containment ring warms to said ambient temperature.

42. The apparatus of claim 24 wherein said fan case is made of a first material having a first containment strength and said containment ring is made of a second material having a second containment strength higher than that of the first material.

43. The apparatus of claim 42 wherein said first material is aluminum and said second material is a nickel-based super alloy.

44. The apparatus of claim 35 wherein said fan case is made of a first material having a first strength and said stiffener ring is made of a second material having a second strength higher than that of the first material.

45. The apparatus of claim 44 wherein said first material is aluminum and said second material is a nickel-based super alloy.

46. A method, comprising:

encircling an outer circumferential surface of a heat resistance ring using an inner circumferential surface of a fan case of a gas turbine jet engine; and

applying radially compressive forces to said outer circumferential surface along the length of the circumference of said inner circumferential surface using said encircling inner circumferential surface.

47. The method of claim 46 wherein said radially compressive force applying includes shrink interference fitting said heat resistance ring to said fan case.

48. The method of claim 46 wherein said radially compressive force applying includes seating said heat resistance ring within a notch defined by said fan case and shaped to secure said heat resistance ring against displacement in a direction longitudinal to said fan case.

49. The method of claim 46 wherein said fan case surrounds a fan adapted for rotation within said fan case along an axis of rotation wherein said radially compressive forces are directed to a center located on said axis of rotation.

50. The method of claim 46 further comprising:

machining a heat resistance ring notch circumferentially into an inner surface towards a middle of the fan case; and

seating said heat resistance ring in said heat resistance ring notch through a shrink interference fit.

51. A method according to claim 50 wherein said machining further comprises machining said heat resistance ring notch into said inner surface of the fan case in a first direction, wherein a plurality of grooves are formed and aligned on said inner surface in said first direction.

52. A method according to claim 51 further comprising:

prior to said machining, making said heat resistance ring from a titanium sheet material that is cut, bent into a cylindrical shape, and welded along a seam; and

forming said heat resistance ring to a predetermined shape to match with said heat resistance ring notch.

53. A method according to claim 51 further comprising:

prior to said machining, forging said heat resistance ring in one piece; and

machining said heat resistance ring to a predetermined shape to match with said heat resistance ring notch.

54. A method according to claim 53 wherein said heat resistance ring is forged from a one of titanium, steel, steel alloy, and aerospace super alloys in one piece.

55. A method according to claim 53 wherein said heat resistance ring machining further comprises machining an outer surface of said heat resistance ring in a second direction, wherein a plurality of grooves are formed and aligned on said outer surface in said second direction;

wherein when said inner surface of said heat resistance ring notch and said outer surface of said heat resistance ring are seated together, said plurality of grooves on said inner surface of said heat resistance ring notch and said plurality of grooves on said outer surface of said heat resistance ring align in a cross-hatch manner to each other, increasing the frictional forces between said heat resistance ring notch and said heat resistance ring and reducing the potential for spinning of said heat resistance ring within said heat resistance ring notch.

56. A method according to claim 53 further comprising spot welding said heat resistance ring to said heat resistance ring notch in at least one location to retard said heat resistance ring from spinning in relation to said heat resistance ring notch.

57. A method according to claim 53 further comprising bolting said heat resistance ring to at least one flange secured to said heat resistance ring notch to retard said heat resistance ring from spinning in relation to said heat resistance ring notch.

58. A method according to claim 47 wherein said seating further comprises:

heating the fan case to cause an inside diameter of said heat resistance ring notch to increase to a second diameter that is larger than an outside diameter of said heat resistance ring at an ambient temperature;

positioning said heat resistance ring in said heat resistance ring notch; and

allowing the fan case to cool to said ambient temperature, causing said heat resistance ring notch to decrease from said second diameter toward said inside diameter, but resisted from doing so by said outside diameter of said heat resistance ring at said ambient temperature, giving rise to said shrink interference fit.

59. A method according to claim 47 wherein said seating further comprises:

heating the fan case to cause an inside diameter of said heat resistance ring notch to increase to a second diameter;

cooling said heat resistance ring to cause an outside diameter of said heat resistance ring to decrease to a second diameter, wherein said second diameter of said heat resistance ring is smaller than said second diameter of said heat resistance ring notch;

positioning said heat resistance ring in said heat resistance ring notch; and

allowing the fan case to cool to an ambient temperature, causing said heat resistance ring notch to decrease from said second diameter toward said inside diameter, and allowing said heat resistance ring to warm up to said ambient temperature causing said heat resistance ring to increase toward said outside diameter, giving rise to said shrink interference fit.

60. A method according to claim 47 wherein said seating further comprises:

cooling said heat resistance ring to cause an outside diameter of said heat resistance ring to decrease to a second diameter, wherein said second diameter of said heat resistance ring is smaller than an inside diameter of said heat resistance ring notch;

positioning said heat resistance ring in said heat resistance ring notch; and

allowing said heat resistance ring to warm up to said ambient temperature causing said heat resistance ring to increase toward said outside diameter, but resisted from doing so by said inside diameter of said heat resistance ring notch at said ambient temperature, giving rise to said shrink interference fit.

61. The method of claim 46 wherein said fan case is made of a first material having a first heat resistance and said heat resistance ring is made of a second material having a second heat resistance higher than that of the first material.

62. The method of claim 61 wherein said first material is aluminum and said second material is titanium.

63. An apparatus for use in a gas turbine jet engine, the apparatus comprising:

a fan case having a middle portion having an inner surface which defines a heat resistance ring notch machined circumferentially into said fan case surface; and

a heat resistance ring adapted to be seated in said heat resistance ring notch to provide radially compressive forces applied from said fan case to said heat resistance ring.

64. The apparatus of claim 63, wherein said heat resistance ring is adapted to be seated through a shrink interference fit.

65. The apparatus according to claim 63 wherein said heat resistance ring is forged from a one of titanium, steel, steel alloy, and aerospace super alloys in one piece and machined to a predetermined shape.

66. The apparatus according to claim 63 wherein said heat resistance ring is made from one of titanium, steel, steel alloy, and aerospace super alloys sheet material that is cut, bent into a cylindrical shape, and welded along a seam and formed to a predetermined shape to match with said heat resistance ring notch.

67. The apparatus according to claim 64 wherein an outside diameter of said heat resistance ring is slightly larger than an inside diameter of said heat resistance ring notch at an ambient air temperature, and the fan case is heated to cause said inside diameter of said heat resistance ring notch to increase to a second diameter that is larger than said outside diameter of said heat resistance ring, enabling said heat resistance ring to be positioned in said heat resistance ring notch giving rise to said shrink interference fit when the fan case cools to said ambient temperature.

68. The apparatus according to claim 64 wherein an outside diameter of said heat resistance ring is slightly larger than an inside diameter of said heat resistance ring notch at an ambient air temperature, and the fan case is heated to cause said inside diameter of said heat resistance ring notch to increase to a second diameter, and said heat resistance ring is cooled to cause an outside diameter of said heat resistance ring to decrease to a second diameter, wherein said second diameter of said heat resistance ring is smaller than said second diameter of said heat resistance ring notch, enabling said heat resistance ring to be positioned in said heat resistance ring notch giving rise to said shrink interference fit when the fan case cools and said heat resistance ring warms up to said ambient temperature.

69. The apparatus according to claim 64 wherein an outside diameter of said heat resistance ring is slightly larger than an inside diameter of said heat resistance ring notch at an ambient air temperature, and said heat resistance ring is cooled to cause an outside diameter of said heat resistance ring to decrease to a second diameter that is smaller than said inside diameter of said heat resistance ring notch, enabling said heat resistance ring to be positioned in said heat resistance ring notch giving rise to said shrink interference fit when said heat resistance ring warms up to said ambient temperature.

70. The apparatus according to claim 63 further comprising:

a plurality of grooves aligned in a first direction on a machined inner surface of said heat resistance ring notch; and

a plurality of grooves aligned in a second direction on a machined outer surface of said heat resistance ring;

wherein when said inner surface of said heat resistance ring notch and said outer surface of said heat resistance ring are interference shrink fit together, said plurality of grooves on said inner surface of said heat resistance ring notch and said plurality of grooves on said outer surface of said heat resistance ring align in a cross-hatch manner to each other, increasing the frictional forces between said heat resistance ring notch and said heat resistance ring and reducing the potential for spinning of said heat resistance ring within said heat resistance ring notch.

71. The apparatus according to claim 63 further comprising:

a spot weld in at least one location for welding said heat resistance ring to said heat resistance ring notch to prevent said heat resistance ring from spinning in relation to said heat resistance ring notch.

72. The apparatus according to claim 63 further comprising:

at least one flange secured to said heat resistance ring notch, wherein said heat resistance ring is bolted to said at least one flange to prevent said heat resistance ring from spinning in relation to said heat resistance ring notch.

73. The apparatus according to claim 63 wherein the fan case is forged from aluminum.

74. The apparatus according to claim 63 wherein the fan case is manufactured from aluminum.

75. The apparatus according to claim 63 wherein the fan case is manufactured from a composite material.

76. The apparatus of claim 63 wherein said fan case is made of a first material having a first heat resistance and said heat resistance ring is made of a second material having a second heat resistance higher than that of the first material.

77. The apparatus of claim 76 wherein said first material is aluminum and said second material is titanium.

78. A gas turbine jet engine, comprising:

a fan case having an inner circumferential surface;

a turbine case having a turbine adapted to rotate along an axis of rotation within said fan case;

a fan having fan blades coupled to said turbine and adapted to rotate along an axis of rotation within said fan case; and

a containment ring having an outer circumferential surface, said containment ring being positioned around said fan to contain said fan blades in the event said fan blades become separated from said fan;

wherein said fan case is adapted to apply radially compressive forces to said outer circumferential surface of said containment ring, along the length of the circumference of said inner circumferential surface.

79. The engine according to claim 78 further comprising:

at least one flange secured to fan case, wherein said containment ring is bolted to said at least one flange to retard said containment ring from spinning in relation to said fan case.

80. The engine according to claim 79 further comprising:

at least one stiffening ring notch machined circumferentially into a surface of the fan case; and

a stiffening ring seated in said at least one stiffening ring notch, wherein said stiffening ring is seated through a shrink interference fit, wherein said stiffening ring resists the fan case from going oval under a load and temperature conditions experienced during operation of the gas turbine jet engine.

81. The engine of claim 78 wherein the fan case has a middle portion having an inner surface which defines a heat resistance ring notch machined circumferentially into said fan case surface, the engine further comprising a heat resistance ring adapted to be seated in said heat resistance ring notch to provide radially compressive forces applied from said fan case to said heat resistance ring.

82. The engine of claim 81, wherein said heat resistance ring is adapted to be seated through a shrink interference fit.

83. A method of retrofitting a gas turbine jet engine, comprising:

removing a fan case from the jet engine; and

installing a substitute fan case on said jet engine, wherein said substitute fan case has a containment ring seated in an inner circumferential surface of the substitute fan case through a shrink interference fit.

84. The method of claim 83 further comprising seating said containment ring in a circumferential notch of said inner circumferential surface of the substitute fan case through a shrink interference fit, prior to installing said substitute fan case.

85. A method of operating a gas turbine jet engine, comprising:

rotating a fan using a turbine within a fan case along an axis of rotation to provide air intake and thrust; and

applying radially compressive forces to an outer circumferential surface of one of a containment ring and the fan case using an inner circumferential surface of the other of the containment ring and the fan case encircling said outer circumferential surface, said radially compressive forces being applied along the length of the circumference of the inner circumferential surface and directed to a center positioned on said axis of rotation.

86. The method of claim 85 further comprising applying radially compressive forces to an outer circumferential surface of the fan case using an inner circumferential surface of a stiffener ring encircling said fan case outer circumferential surface.

87. The method of claim 85 further comprising applying radially compressive forces to an outer circumferential surface of a heat resistance ring using an inner circumferential surface of the fan case encircling said heat resistance ring outer circumferential surface.

88. An apparatus for use in a gas turbine jet engine, the apparatus comprising:

a fan case having a front end and an inner surface and an outer surface towards said front end of the fan case wherein said inner surface defines a containment ring notch machined circumferentially into said fan case inner surface and wherein said fan case outer surface defines at least one stiffening ring notch machined circumferentially into said outer surface of the fan case, wherein said fan case further has a middle portion having an inner surface which defines a heat resistance ring notch machined circumferentially into said fan case middle inner surface and wherein said fan case is made of a first material having a first containment strength and a first heat resistance;

a containment ring adapted to be seated in said containment ring notch to provide radially compressive forces applied from said fan case front inner surface to said containment ring wherein said containment ring is made of a second material having a second containment strength higher than that of the first material;

a stiffening ring adapted to be seated in said at least one stiffening ring notch to provide radially compressive forces applied from said stiffening ring to said fan case outer surface and wherein said stiffener ring is made of a material having a strength higher than that of the first material; and

a heat resistance ring adapted to be seated in said heat resistance ring notch to provide radially compressive forces applied from said fan case middle inner surface to said heat resistance ring and wherein said heat resistance ring is made of a third material having a second heat resistance higher than that of the first material.

89. The apparatus of claim 88 wherein said first material is aluminum, said second material is a nickel-based super alloy, said stiffener ring material is a nickel-based super alloy and said third material is titanium.