System and method for improving transition lift-fan performance

Abstract

A system and method enabled to increase efficiency during a VTOL aircraft's transition. A VTOL aircraft enabled to operate multiple lift fans arranged into separately controllable groups, wherein the VTOL aircraft initially has vertical flight but transitions to horizontal flight. A first group of lift fans may be kept at full throttle, a second group of lift fans may be throttled to balance thrust and/or weight, and a third group of lift fans may be shut off.

We claim: 
     
         1 . A propulsion system for increasing efficiency during a vertical take off and landing (VTOL) aircraft's transition, comprising:
 a plurality of lift fans arranged into three or more separately controlled groups, wherein the plurality of lift fans are used to transition a VTOL aircraft between vertical flight and horizontal flight;   wherein a first group of lift fans is kept at full throttle during transition;   wherein a second group of lift fans is throttled to balance thrust during transition; and   wherein a third group of lift fans is shut off during transition.   
     
     
         2 . The system of  claim 1 , wherein at least one of the plurality of lift fans is throttled using one of the following throttling techniques: (i) varying the fan's RPM; (ii) varying fan's pitch; or (iii) combinations thereof. 
     
     
         3 . The system of  claim 1 , wherein the aircraft's pitch and roll are trimmed by throttling the second group of lift fans. 
     
     
         4 . The system of  claim 1 , wherein the aircraft has a disc loading of 50 lbs per square foot or less. 
     
     
         5 . The system of  claim 1 , wherein the shut-off lift-fans are covered after being shut down to decrease aerodynamic drag on the VTOL aircraft. 
     
     
         6 . The system of  claim 1 , wherein at least one of the plurality of lift fans has adjustable vanes to direct the fan exhaust flow aft, thereby providing thrust and reducing drag. 
     
     
         7 . The system of  claim 1 , wherein the plurality of lift fans comprises six or more lift fans. 
     
     
         8 . The system of  claim 1 , wherein the VTOL aircraft uses a hybrid of turbine and electric thrusting. 
     
     
         9 . A vertical take off and landing (VTOL) aircraft having an increased efficiency during vertical takeoff and landing transitions, comprising:
 a plurality of lift fans arranged into three or more separately controlled groups, wherein the plurality of lift fans are used to transition the VTOL aircraft between vertical flight and horizontal flight;   wherein a first group of lift fans is kept at full throttle during transition;   wherein a second group of lift fans is throttled to balance thrust during transition; and   wherein a third group of lift fans is shut off during transition.   
     
     
         10 . The aircraft of  claim 9 , wherein at least one of the plurality of lift fans is throttled using one of the following throttling techniques: (i) varying the fan's RPM; (ii) varying fan's pitch; or (iii) combinations thereof. 
     
     
         11 . The aircraft of  claim 9 , wherein the aircraft's pitch and roll are trimmed by throttling the second group of lift fans. 
     
     
         12 . The aircraft of  claim 9 , wherein the disc loading value is 50 lbs per square foot or less. 
     
     
         13 . The aircraft of  claim 9 , wherein the shut-off lift-fans are covered after being shut down to decrease aerodynamic drag on the VTOL aircraft. 
     
     
         14 . The aircraft of  claim 9 , wherein at least one of the plurality of lift fans has adjustable vanes to direct the fan exhaust flow aft, thereby providing thrust and reducing drag. 
     
     
         15 . The aircraft of  claim 9 , wherein the plurality of lift fans comprises six or more lift fans. 
     
     
         16 . The aircraft of  claim 9 , wherein the VTOL aircraft uses a hybrid of turbine and electric thrusting.