Thrust reversing system for counter rotating propellers
AssigneeThe Boeing Company
InventorFranklyn J. Davenport
Life of this patent
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Abstract
A method of creating thrust reversal for an engine having counter-rotating forward and rear propeller blades. The forward blades are set at a positive angle of attack to produce an orderly flow of air toward the rear blades. The rear blades are set at a negative angle of attack to produce reverse thrust. The net effect is that the thrust produced by the rear blades overbalances that of the forward blades to produce net thrust reversal.
Claims24
A method of operating an airplane engine to create reverse thrust where the engine has a counter rotating propeller assembly where there is a forward first set of first variable pitch propeller blades mounted for rotation on a first longitudinally aligned propeller axis, and a rear second set of second variable pitch propeller blades positioned behind, and adjacent to, said first set of propeller blades, and mounted for rotation about a second longitudinally aligned center propeller axis, under circumstances where said assembly is traveling in a forward direction at a forward velocity relative to ambient air, said method comprising:
- a. rotating said first set of first propeller blades about said first propeller axis in a first rotational direction with a first rotational velocity, and with pitch of the first propeller blades being set at a first pitch setting, a relative to said first rotational velocity and said forward velocity, so that said first blades have a positive angle of attack to produce a forward thrust;
- b. rotating said second set of second propeller blades about said second propeller axis in a second opposite rotational direction with a second rotational velocity, with pitch of the second propeller blades being set at a second pitch setting, relative to said second rotational velocity, said first rotational velocity, and said forward velocity so that said second blades have a negative angle of attack to produce a reverse thrust, with said reverse thrust countering said forward thrust so as to produce a net reverse thrust component.
A method of producing reverse thrust in a fluid medium from a counter rotating propeller assembly where there is a forward first set of first propeller blades mounted for rotation on a first longitudinally aligned propeller axis, and a rear second set of variable pitch second propeller blades positioned behind, and adjacent to, said first set of propeller blades, and mounted for rotation about a second longitudinally aligned center propeller axis, under circumstances where said assembly is traveling in a forward direction relative to ambient air at a forward velocity, said method comprising:
- a. rotating said first set of first propeller blades about said first propeller axis in a first rotational direction with a first rotational velocity, and with pitch of the first propeller blades being set at a first pitch setting, relative to said first rotational velocity and said forward velocity, so that said first blades have a positive angle of attack to produce a forward thrust;
- b. rotating said second set of second propeller blades about said second propeller axis in a second opposite rotational direction with a second rotational velocity compound, with pitch of the second propeller blades being set at a second pitch setting, relative to said second rotational velocity component and said forward velocity, so that said second blades have a negative angle of attack to produce a reverse thrust, with said reverse thrust countering said forward thrust so as to produce a net reverse thrust component.
Dependencies are inferred from the claim text.