Methods for operating an air vehicle

Patent metadata

Field	Value
Publication number	US-2016347451-A1
Application number	US-201515113368-A
Country	US
Kind code	A1
Filing date	Jan 27, 2015
Priority date	Jan 28, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

Methods are provided for operating an air vehicle having fixed wings. Such methods include the step of providing an operating map of angle of attack associated with the fixed wings with Reynolds number, including conditions of separated flow over the fixed wings and conditions of attached flow over the fixed wings. Such methods also include the step of using the operating map for guidance, causing the air vehicle to operate at least within a low Reynolds numbers range corresponding to the operating map, such as to avoid or minimize risk of causing the air vehicle to operate at conditions of separated flow over the fixed wings.

First claim

1 . Method for operating an air vehicle having fixed wings, comprising:
(A) providing an operating map of angle of attack associated with the fixed wings with Reynolds number, including conditions of separated flow over the fixed wings and conditions of attached flow over the fixed wings; (B) using the operating map for guidance, causing the air vehicle to operate at least within a low Reynolds numbers range corresponding to the operating map, such as to avoid or minimize risk of causing the air vehicle to operate at conditions of separated flow over the fixed wings.

2 . Method according to claim 1 , wherein the operating map comprises:
a first operating region in said operating map comprising a plurality of first points therein, each said first point representing a respective first set of a respective said angle of attack and a respective said Reynolds number, said first operating region defining a first operating boundary comprising a first variation of a maximum Reynolds number limit with said angle of attack; a second operating region in said operating map comprising a plurality of second points therein, each said second point representing a respective second set of a respective said angle of attack and a respective said Reynolds number, said second operating region defining a second operating boundary comprising a second variation of a minimum Reynolds number limit with said angle of attack; a third operating region in said operating map extending between said first operating boundary and said second operating boundary, said third operating region comprising a plurality of third points therein, each said third point representing a respective third set of a respective said angle of attack and a respective said Reynolds number,
each said first point in said first region corresponding to conditions of separated flow over the fixed wings irrespective of whether or not the respective said first point was reached from any one of said third points;
each said second point in said second region corresponding to conditions of attached flow over the fixed wings irrespective of whether or not the respective said second point was reached from any one of said third points; and
each said third point in said third region corresponding to conditions of attached flow or to conditions of separated flow over the fixed wings, depending on whether the respective said third point was reached from any one of said second points or from any one of said first points, respectively;

3 . Method according to claim 2 , wherein step (B) comprises:
(b) causing the air vehicle to operate at a desired said third point by reaching the desired said third point from a first desired said second point.

4 . Method according to claim 3 , wherein prior to step (b) the air vehicle has nominally zero forward speed, the method comprising the step:
(c) causing the air vehicle to arrive at said desired second point from a nominal said first point corresponding to said nominally zero forward speed.

5 . Method according to claim 3 , particularly for operating the air vehicle to attain aerodynamic flight from conditions of nominally zero forward velocity, comprising the step:
(c) causing the air vehicle to arrive at said desired second point from a nominal said first point corresponding to said nominally zero forward speed.

6 . Method according to any one of claims 4 and 5 , wherein at said nominal first point, the air vehicle is on the ground.

7 . Method according to any one of claims 4 and 5 , wherein at said nominal first point, the air vehicle is supported by an external structure.

8 . Method according to any one of claims 4 to 7 , wherein step (c) comprises accelerating the air vehicle to attain a forward speed via a forward thrust generated by the air vehicle.

9 . Method according to any one of claims 4 to 7 , wherein step (c) comprises accelerating the air vehicle to attain a forward speed via an external acceleration structure.

10 . Method according to claim 9 , wherein said external acceleration structure comprises a catapult system.

11 . Method according to any one of claims 4 and 5 , wherein at said nominal first point, the air vehicle is in vectored flight, wherein a vertical vectored thrust generated by the air vehicle support the weight of the air vehicle.

12 . Method according to claim 11 , wherein step (c) comprises accelerating the air vehicle to attain a forward speed via a forward vectored thrust generated by the air vehicle.

13 . Method according to any one of claims 4 to 12 , wherein step (c) comprises applying a forward speed to the air vehicle while causing the air vehicle to adopt a respective said angle of attack for the wings having a non-positive value at least at said desired first point.

14 . Method according to claim 13 , comprising maintaining the respective said angle of attack for the wings at said non-positive value as said forward speed is increased to a first speed at which the lift generated by the wings is a first proportion of the weight of the air vehicle, and thereafter increasing the respective said angle of attack at said first speed until the air vehicle reaches said desired third point.

15 . Method according to claim 14 , wherein said first proportion is between 0.2 and 0.4 of the weight of the air vehicle, and further comprising subsequently concurrently increasing the speed and angle of attack to reach a second desired third point.

16 . Method according to claim 14 , wherein said first proportion is between 0.4 and 0.6 of the weight of the air vehicle, and further comprising subsequently increasing the angle of attack while concurrently maintaining constant speed to reach a second desired third point.

17 . Method according to any one of claims 4 to 12 , wherein step (c) comprises applying a forward speed to the air vehicle while causing the air vehicle to adopt a respective said angle of attack for the wings having a small positive value at least at said desired first point, and causing the air vehicle to reach said first desired second point by increasing air speed of the air vehicle.

18 . Method according to claim 17 , comprising maintaining the respective said angle of attack for the wings at said small positive value as said forward speed is increased to a first speed at which the lift generated by the wings is a first proportion of the weight of the air vehicle, and thereafter increasing the respective said angle of attack and said speed until the air vehicle reaches said desired third point.

19 . Method according to claim 18 , wherein said first proportion is between 0.2 and 0.4 of the weight of the air vehicle, and wherein said small positive value is between 1° and 5°.

20 . Method according to any one of claims 1 to 19 , wherein at said desired third point the respective said Reynolds numbers corresponds to a forward speed of the air vehicle not less than the stall speed of the air vehicle.

21 . Method according to any one of claims 1 to 20 , wherein at said desired third point the respective said Reynolds numbers is less than 450,000.

22 . Method according to any one of claims 1 to 21 , wherein at said desired third point the respective said Reynolds numbers is less than 700,000.

23 . Method according to any one of claims 1 to 22 , wherein at said desired third point the respective said Reynolds numbers is less than 600,000.

24 . Method according to any one of claims 1 t

Assignees

• Israel Aerospace Ind Ltd

Inventors

• Shepshelovich Michael
• Abramov Danny
• Klein Yonatan

Classifications

• B64U30/10

  Wings · CPC title

• B64U70/70

  Launching or landing using catapults, tracks or rails (launching from storage containers B64U70/50) · CPC title

• B64C2201/084

  Operations & Transport · mapped topic

• B64D43/02

  for indicating aircraft speed or stalling conditions · CPC title

• B64C15/12

  the power plant being tiltable · CPC title