US4883240A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Aircraft propeller noise reduction
Assignee: General Electric Co
•
Filing: 1986-11-12
•
Granted: 1989-11-28
•
Expires: 2006-11-12
Abstract
Abstract In one form of the invention, a counterrotating pair of aircraft propellers produces noise in the form of a frequency-modulated carrier wave. The frequency modulation allows a designer to manipulate the energy spectrum of the noise in order to, for example, place much of the acoustic energy into inaudible frequency ranges.
Inventors
- 👤 Arthur P. Adamson
- 👤 Philip R. Gliebe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 17:25
CPC Classifications
B; B64; B64C; B64C11/00; B64D; B64D27/00; B64D27/02; B64D27/026; Y; Y10; Y10S; Y10S416/00; Y10S416/50
Claims Analysis
Total Claims: 46
Claim 1
Independent Claim
52 words
A counterrotating aircraft propeller set comprising: (a) a first propeller having N1 blades and (b) a second propeller having N2 blades wherein N1 and N2 are selected from the following group of numbers: 3, 5, 7, 9, 11, 13, 15, and 17 and wherein the difference between N1 and N2 is 2.
Claim 2
Dependent Claim
52 words
A counterrotating aircraft propeller set comprising: (a) a first propeller having N1 blades and (b) a second propeller having N2 blades wherein N1 and N2 are selected from the following group of numbers: 3, 5, 7, 9, 11, 13, 15, and 17 and wherein the difference between N1 and N2 is 2.
Claim 3
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: (a) a first propeller having 8 blades and (b) a second propeller having 11 blades.
Claim 4
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: (a) a first propeller having 8 blades and (b) a second propeller having 11 blades.
Claim 5
Dependent Claim
19 words
A counterrotating aircraft propeller set in which the blade crossings which are sequential in time are non-adjacent in space.
Claim 6
Dependent Claim
19 words
A counterrotating aircraft propeller set in which the blade crossings which are sequential in time are non-adjacent in space.
Claim 7
Dependent Claim
22 words
A counterrotating aircraft propeller pair in which the distance between sequential blade crossings is greater than the blade spacing on either propeller.
Claim 8
Dependent Claim
22 words
A counterrotating aircraft propeller pair in which the distance between sequential blade crossings is greater than the blade spacing on either propeller.
Claim 9
Dependent Claim
39 words
A counterrotating aircraft propeller set comprising: a first propeller having a first number of blades; and a second propeller having a second number of blades, in which the blade crossings which are sequential in time are non-adjacent in space.
Claim 10
Dependent Claim
39 words
A counterrotating aircraft propeller set comprising: a first propeller having a first number of blades; and a second propeller having a second number of blades, in which the blade crossings which are sequential in time are non-adjacent in space.
Claim 11
Dependent Claim
45 words
A counterrotating aircraft propeller set comprising: a first propeller having a first number of blades; and a second propeller having a second number of blades, in which the distance between the locations of sequential blade crossings is greater than the blade spacing on either propeller.
Claim 12
Dependent Claim
45 words
A counterrotating aircraft propeller set comprising: a first propeller having a first number of blades; and a second propeller having a second number of blades, in which the distance between the locations of sequential blade crossings is greater than the blade spacing on either propeller.
Claim 13
Independent Claim
79 words
A method of reducing the audible noise produced by a counterrotating aircraft propeller set having aft and fore propellers, comprising the step of: causing the locations of the blade crossings to rotate about an axis at a speed greater than the quantity: ##EQU5## in which N a and N f are the numbers of blades on the aft and fore propellers, respectively, and S a and S f are the rotational speeds of the aft and fore propellers, respectively.
Claim 14
Independent Claim
79 words
A method of reducing the audible noise produced by a counterrotating aircraft propeller set having aft and fore propellers, comprising the step of: causing the locations of the blade crossings to rotate about an axis at a speed greater than the quantity: ##EQU5## in which N a and N f are the numbers of blades on the aft and fore propellers, respectively, and S a and S f are the rotational speeds of the aft and fore propellers, respectively.
Claim 15
Independent Claim
95 words
A method of reducing audible noise produced by a counterrotating aircraft propeller set which produces a modulating phenomenon when a fore propeller blade crosses an aft propeller blade, such modulating phenomenon rotating about an axis, comprising the step of: causing the modulating phenomenon to rotate about the axis at a speed equal to or greater than the quantity: ##EQU6## in which N a and N f are the numbers of blades on the aft and fore propellers, respectively, and S a and S f are the rotational speeds of the aft and fore propellers, respectively.
Claim 16
Independent Claim
95 words
A method of reducing audible noise produced by a counterrotating aircraft propeller set which produces a modulating phenomenon when a fore propeller blade crosses an aft propeller blade, such modulating phenomenon rotating about an axis, comprising the step of: causing the modulating phenomenon to rotate about the axis at a speed equal to or greater than the quantity: ##EQU6## in which N a and N f are the numbers of blades on the aft and fore propellers, respectively, and S a and S f are the rotational speeds of the aft and fore propellers, respectively.
Claim 17
Dependent Claim
76 words
A counterrotating aircraft propeller set comprising: a first propeller having a first number of blades; and a second propeller having a second number of blades, in which the aircraft propeller set generates a far-field noise having a resultant component described by the following equation: P=sin (W.sub.c +M sin (W.sub.m t)), in which P represents pressure, W c represents a carrier frequency, M represents a modulation index, W m represents a modulation frequency, and t represents time.
Claim 18
Dependent Claim
76 words
A counterrotating aircraft propeller set comprising: a first propeller having a first number of blades; and a second propeller having a second number of blades, in which the aircraft propeller set generates a far-field noise having a resultant component described by the following equation: P=sin (W.sub.c +M sin (W.sub.m t)), in which P represents pressure, W c represents a carrier frequency, M represents a modulation index, W m represents a modulation frequency, and t represents time.
Claim 19
Dependent Claim
32 words
A counterrotating aircraft propeller set comprising: a first propeller having N1 blades; and a second propeller having N2 blades, in which N1 and N2 differ by 2 and have no common factors.
Claim 20
Dependent Claim
32 words
A counterrotating aircraft propeller set comprising: a first propeller having N1 blades; and a second propeller having N2 blades, in which N1 and N2 differ by 2 and have no common factors.
Claim 21
Dependent Claim
19 words
A counterrotating aircraft propeller set comprising: a first propeller having 7 blades; and a second propeller having 12 blades.
Claim 22
Dependent Claim
19 words
A counterrotating aircraft propeller set comprising: a first propeller having 7 blades; and a second propeller having 12 blades.
Claim 23
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: a first propeller having 8 blades; and a second propeller having 11 or 13 blades.
Claim 24
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: a first propeller having 8 blades; and a second propeller having 11 or 13 blades.
Claim 25
Dependent Claim
25 words
A counterrotating aircraft propeller set comprising: a first propeller having 5 blades; and a second propeller having 7, 8, 11, 12, 13, or 14 blades.
Claim 26
Dependent Claim
25 words
A counterrotating aircraft propeller set comprising: a first propeller having 5 blades; and a second propeller having 7, 8, 11, 12, 13, or 14 blades.
Claim 27
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: a first propeller having 6 blades; and a second propeller having 11 or 13 blades.
Claim 28
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: a first propeller having 6 blades; and a second propeller having 11 or 13 blades.
Claim 29
Dependent Claim
25 words
A counterrotating aircraft propeller set comprising: a first propeller having 7 blades; and a second propeller having 9, 10, 11, 12, 13, or 15 blades.
Claim 30
Dependent Claim
25 words
A counterrotating aircraft propeller set comprising: a first propeller having 7 blades; and a second propeller having 9, 10, 11, 12, 13, or 15 blades.
Claim 31
Dependent Claim
19 words
A counterrotating aircraft propeller set comprising: a first propeller having 8 blades; and a second propeller having 10 blades.
Claim 32
Dependent Claim
19 words
A counterrotating aircraft propeller set comprising: a first propeller having 8 blades; and a second propeller having 10 blades.
Claim 33
Dependent Claim
22 words
A counterrotating aircraft propeller set comprising: a first propeller having 8 blades; and a second propeller having 11, 13, or 14 blades.
Claim 34
Dependent Claim
22 words
A counterrotating aircraft propeller set comprising: a first propeller having 8 blades; and a second propeller having 11, 13, or 14 blades.
Claim 35
Dependent Claim
19 words
A counterrotating aircraft propeller set comprising: a first propeller having 8 blades; and a second propeller having 12 blades.
Claim 36
Dependent Claim
19 words
A counterrotating aircraft propeller set comprising: a first propeller having 8 blades; and a second propeller having 12 blades.
Claim 37
Dependent Claim
22 words
A counterrotating aircraft propeller set comprising: a first propeller having 9 blades; and a second propeller having 11, 13, or 14 blades.
Claim 38
Dependent Claim
22 words
A counterrotating aircraft propeller set comprising: a first propeller having 9 blades; and a second propeller having 11, 13, or 14 blades.
Claim 39
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: a first propeller having 10 blades; and a second propeller having 13 or 14 blades.
Claim 40
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: a first propeller having 10 blades; and a second propeller having 13 or 14 blades.
Claim 41
Dependent Claim
22 words
A counterrotating aircraft propeller set comprising: a first propeller having 11 blades; and a second propeller having 13, 14, or 15 blades.
Claim 42
Dependent Claim
22 words
A counterrotating aircraft propeller set comprising: a first propeller having 11 blades; and a second propeller having 13, 14, or 15 blades.
Claim 43
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: a first propeller having 13 blades; and a second propeller having 14 or 15 blades.
Claim 44
Dependent Claim
21 words
A counterrotating aircraft propeller set comprising: a first propeller having 13 blades; and a second propeller having 14 or 15 blades.
Claim 45
Dependent Claim
19 words
A counterrotating aircraft propeller set comprising: a first propeller having 14 blades; and a second propeller having 15 blades.
Claim 46
Dependent Claim
19 words
A counterrotating aircraft propeller set comprising: a first propeller having 14 blades; and a second propeller having 15 blades.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-11-27 | 1993-05-29 | 1993-11-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-11-27 | 1997-05-29 | 1997-11-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-11-27 | 2001-05-29 | 2001-11-28 | $7700.00 | Window Closed / Lapsed |