Patent Description:
Angle of attack sensors with rotatable vanes are installed on sides of aircraft to measure the aircraft angle of attack, the angle between oncoming airflow and the aircraft zero line (a reference line of the aircraft, such as a chord of a wing of the aircraft). The angle of attack sensor is mounted to the aircraft such that the rotatable vane protrudes outside the aircraft and is exposed to oncoming airflow. Aerodynamic forces acting on the rotatable vane cause the vane to align with the direction of the oncoming airflow. Rotational position of the vane is sensed and used to determine the aircraft angle of attack.

Moisture and other contaminants can enter and move through the angle of attack sensor along with the oncoming airflow. Freezing water and pollutants can impede or interfere with the free rotation and aerodynamic characteristics of the vane, which can cause the angle of attack sensor to generate less accurate measurements. Angle of attack sensors are discloses in <CIT> and <CIT>.

An angle of attack sensor is provided as defined by claim <NUM>.

A vane shaft for an angle of attack sensor includes a body portion, a top portion connected to an end of the body portion, the top portion being configured to connect to a vane assembly, a bore extending through the body portion and the top portion, and a first vent hole extending through the body portion from the bore to an exterior surface of the vane shaft.

A method of directing airflow through an angle of attack sensor is provided as defined by claim <NUM>.

In general, the present disclosure describes an angle of attack sensor that has a vent hole in the vane shaft beneath a lip of the vane shaft seal and above the bearing to direct venting airflow through a center bore of the vane shaft and past the vane shaft seal, resulting in a sealed breathing path where the venting airflow bypasses the bearing. Consequently, the bearing is not subjected to contaminants and water in the airflow, preventing the bearing from freezing and increasing the life of the angle of attack sensor.

<FIG> is a partial cross-sectional view of angle of attack sensor <NUM>. Angle of attack sensor <NUM> includes faceplate <NUM>, housing <NUM>, mounting holes <NUM>, opening <NUM>, vane assembly <NUM> (including vane <NUM> and vane base <NUM>), annular gap <NUM>, vane shaft <NUM>, o-ring <NUM>, counterweight <NUM>, resolver <NUM>, and electronics <NUM>. Vane assembly <NUM>, counterweight <NUM>, and resolver <NUM> are not shown in cross-section in <FIG>.

Faceplate <NUM> is a faceplate of angle of attack sensor <NUM>. Faceplate <NUM> is positioned on and connected to housing <NUM>. Housing <NUM> is cylindrical with an annular sidewall between an open first end and a closed second end. Faceplate <NUM> is positioned on the open first end of housing <NUM> such that a portion of faceplate <NUM> extends within the open first end of housing <NUM>. Faceplate <NUM> is sealed to housing <NUM>. Mounting holes <NUM> extend through faceplate <NUM> from a first surface of faceplate <NUM> to a second surface of faceplate <NUM>. Mounting holes <NUM> are positioned near a periphery of faceplate <NUM>. Opening <NUM> is a circular opening at a center of faceplate <NUM>. Vane assembly <NUM> extends through opening <NUM> of faceplate <NUM>. Vane assembly <NUM> has vane <NUM> connected to vane base <NUM> at a first end of vane <NUM>. Vane base <NUM> is positioned in opening <NUM>. Annular gap <NUM> is adjacent vane base <NUM>. Annular gap <NUM> is a space that surrounds vane base <NUM>. As such, annular gap <NUM> is between vane base <NUM> and faceplate <NUM>. Consequently, annular gap <NUM> acts as a representation of the boundary between parts that rotate, such as vane <NUM> and vane base <NUM>, and parts that do not rotate, such as faceplate <NUM>. A first end of rotatable vane shaft <NUM> is connected to vane base <NUM>. Vane shaft <NUM> extends through faceplate <NUM> into and within housing <NUM>. O-ring <NUM> is positioned in a groove in the first end of vane shaft <NUM> such that o-ring <NUM> is between vane base <NUM> and the first end of vane shaft <NUM>. Counterweight <NUM> is mounted on the second end of vane shaft <NUM>. As such, vane base <NUM>, vane shaft <NUM>, and counterweight <NUM> are configured to rotate together. Resolver <NUM> is connected to vane shaft <NUM> via a resolver shaft. Resolver <NUM> is positioned within housing <NUM>. Electronics <NUM> are positioned adjacent resolver <NUM> and connected to resolver <NUM> within housing <NUM>.

Angle of attack sensors <NUM> are installed on the exterior of an aircraft and mounted to the aircraft via fasteners, such as screws or bolts, through mounting holes <NUM> on faceplate <NUM>. As a result, faceplate <NUM> is in line with with the skin of the aircraft and housing <NUM> extends within an interior of the aircraft. Vane <NUM> extends outside an exterior of aircraft and is exposed to oncoming airflow, causing vane <NUM> and vane base <NUM> of vane assembly <NUM> to rotate with respect to faceplate <NUM> via a series of bearings within angle of attack sensor <NUM>. Vane <NUM> rotates based on the angle the aircraft is flying at relative to the oncoming airflow. More specifically, vane <NUM> rotates to be parallel with oncoming airflow. Vane <NUM> causes vane base <NUM> to rotate, which causes rotation of vane shaft <NUM>. Rotation of vane shaft <NUM> is sensed by resolver <NUM> and used to measure the local angle of attack, or angle of the airflow relative to the fixed aircraft structure. O-ring <NUM> impedes water ingress between vane base <NUM> and vane shaft <NUM>. Counterweight <NUM> is mounted on vane shaft <NUM> to counterbalance vane <NUM>. Electronics <NUM> power electronic components of angle of attack sensor <NUM>, such as resolver <NUM>.

<FIG> is an enlarged partial cross-sectional view of a portion of angle of attack sensor <NUM>. <FIG> is an isometric view of vane shaft <NUM>. <FIG> is a side view of vane shaft <NUM>. <FIG> is a cross-sectional isometric view of vane shaft <NUM>. <FIG> will be discussed together. Angle of attack sensor <NUM> includes faceplate <NUM>, opening <NUM>, vane assembly <NUM> (including vane <NUM> and vane base <NUM>), annular gap <NUM>, vane shaft <NUM>, o-ring <NUM>, counterweight <NUM>, bearing <NUM>, and vane shaft seal <NUM> (which includes sealing element <NUM> having lip <NUM>). Vane shaft <NUM> includes first end <NUM>, second end <NUM>, body portion <NUM>, top portion <NUM>, bore <NUM>, interior surface <NUM>, exterior surface <NUM>, and vent holes 60A and 60B (shown in <FIG>).

Angle of attack sensor <NUM> has the same structure and function as angle of attack sensor <NUM> described in reference to <FIG>. Bearing <NUM> is positioned around vane shaft <NUM> such that bearing <NUM> surrounds vane shaft <NUM>. Vane shaft seal <NUM> is positioned around vane shaft <NUM> above bearing <NUM> such that vane shaft seal <NUM> surrounds vane shaft <NUM>. A bottom, or end, of vane shaft seal <NUM> contacts a top, or end, of bearing <NUM>. As such, vane shaft seal <NUM> is adjacent bearing <NUM> and between bearing <NUM> and vane assembly <NUM>. Vane shaft seal <NUM> is an annular seal. Vane shaft seal <NUM> has annular sealing element <NUM> with annular lip <NUM> in contact with vane shaft <NUM>. A top, or end, of lip <NUM> makes up a top, or end, of vane shaft seal <NUM>. Vane shaft seal <NUM> is a light seal. As such, lip <NUM> of sealing element <NUM> of vane shaft seal <NUM> contacts vane shaft <NUM> and seals against vane shaft <NUM>, but may also move away from vane shaft <NUM> due to airflow within angle of attack sensor <NUM>.

Vane shaft <NUM> has first end <NUM>, which is connected to vane base <NUM>, and second end <NUM>, which is within housing <NUM> and connected to counterweight <NUM>. Vane shaft <NUM> has body portion <NUM> and top portion <NUM> connected to body portion <NUM>. A first end of top portion <NUM> makes up first end <NUM> of vane shaft <NUM>, a second end of top portion <NUM> is connected to a first end of body portion <NUM>, and a second end of body portion <NUM> makes up second end <NUM> of vane shaft <NUM>. Body portion <NUM> is narrower than top portion <NUM>. Vane shaft seal <NUM> contacts body portion <NUM> of vane shaft <NUM>. Top portion <NUM> is connected to vane base <NUM>. Bore <NUM> is a passageway that extends through vane shaft <NUM> from first end <NUM> to second end <NUM> such that bore <NUM> extends through body portion <NUM> and top portion <NUM> of vane shaft <NUM>. Bore <NUM> is defined by interior surface <NUM>. Interior surface <NUM> is a surface at the inside, and primarily at the center, of vane shaft <NUM>. Exterior surface <NUM> is a surface at the outside of vane shaft <NUM>.

Vent hole 60A is at a first side of vane shaft <NUM> and vent hole 60B is at a second side of vane shaft <NUM>. In this embodiment, vent hole 60A is <NUM> degrees from vent hole 60B. In alternate embodiments, vent holes 60A and 60B may be any distance apart. Vent holes 60A and 60B extend through body portion <NUM> of vane shaft <NUM> from interior surface <NUM> to exterior surface <NUM>. As such, vent holes 60A and 60B are in fluid communication with bore <NUM> of vane shaft <NUM> and extend from bore <NUM> to exterior surface <NUM>. Vent holes 60A and 60B extend through body portion <NUM> of vane shaft <NUM> above bearing <NUM> and below lip <NUM> of sealing element <NUM> of vane shaft seal <NUM>, or adjacent top portion <NUM>, so that vent holes 60A and 60B are between bearing <NUM> and a top, or end, of vane shaft seal <NUM>. Vent holes 60A and 60B do not contact vane shaft seal <NUM>. In alternate embodiments, angle of attack sensor <NUM> may include one or more than two vent holes <NUM>. Body portion <NUM> may have other passageways extending from exterior surface <NUM> into bore <NUM>.

Bearing <NUM> supports rotation of vane shaft <NUM> within bearing <NUM>. Vane shaft seal <NUM> acts as a retainer for bearing <NUM>, keeping bearing <NUM> from backing out of angle of attack sensor <NUM>. Lip <NUM> of sealing element <NUM> of vane shaft seal <NUM> is positioned against vane shaft <NUM> to provide sealing at vane shaft <NUM>. Vane shaft seal <NUM> is a light seal so as to not restrict movement of vane shaft <NUM>, which would interfere with the functionality of angle of attack sensor <NUM>. Vane shaft seal <NUM> allows free rotation of vane assembly <NUM>. Because vane shaft seal <NUM> is a light seal, lip <NUM> will move away from vane shaft <NUM> to allow airflow to move past vane shaft seal <NUM>. As such, vane shaft seal <NUM> keeps most moisture from moving past vane shaft seal <NUM> while allowing airflow to move past vane shaft seal <NUM>.

Airflow moves in and out of angle of attack sensor <NUM> due to changes in pressure during ascent and descent of the aircraft. Airflow will enter angle of attack sensor <NUM> during descent and will evacuate angle of attack sensor <NUM> during ascent. As such, during descent of the aircraft, airflow enters angle of attack sensor <NUM> at annular gap <NUM>. Airflow travels through annular gap <NUM>, past vane shaft seal <NUM> between lip <NUM> of sealing element <NUM> and exterior surface <NUM> of vane shaft seal <NUM> to enter vent holes 60A and 60B, through vent holes 60A and 60B to enter bore <NUM>, and down through bore <NUM> of vane shaft <NUM>. During ascent of the aircraft, airflow travels up through bore <NUM> of vane shaft <NUM> to enter vent holes 60A and 60B, through vent holes 60A and 60B to exterior surface <NUM>, and past vane shaft seal <NUM> between lip <NUM> and exterior surface <NUM> of vane shaft <NUM>, and exits angle of attack sensor <NUM> through annular gap <NUM>. Thus, airflow is vented within angle of attack sensor <NUM> through vane shaft <NUM> and vane shaft seal <NUM>, bypassing bearing <NUM>. As airflow moves through bore <NUM> and vent holes 60A and 60B of vane shaft <NUM> and exits angle of attack sensor <NUM>, water and contaminants are also expelled from angle of attack sensor <NUM> through bore <NUM> and vent holes 60A and 60B along with the airflow.

Traditionally, a faceplate has vent holes that are exposed to oncoming airflow and provide a direct path from the oncoming airflow into an interior chamber of the angle of attack sensor to vent airflow into and out of the interior chamber of the angle of attack sensor. As a result, water and contaminants could easily enter the angle of attack sensor. Because angle of attack sensor <NUM> has vent holes 60A and 60B in vane shaft <NUM>, faceplate <NUM> does not have vent holes that are directly exposed to oncoming airflow and water. Vent holes 60A and 60B are protected from direct water spray by being below a top of vane shaft seal <NUM>. Thus, water is less likely to move into an interior chamber of housing <NUM> and damage electronics <NUM>.

Additionally, because vane shaft <NUM> has vent holes 60A and 60B positioned between bearing <NUM> and a top of vane shaft seal <NUM>, airflow moves into vent holes 60A and 60B and goes around bearing <NUM>. Airflow in angle of attack sensor <NUM> vents through vane shaft <NUM> and does not flow through bearing <NUM>, preventing water and contaminants in the airflow from traveling through bearing <NUM>. As a result, contaminants will not build up over time on bearing <NUM> and interfere with the ability of vane shaft <NUM> to freely rotate, which affects the performance of angle of attack sensor <NUM>. Additionally, the amount of water traveling through bearing <NUM> is reduced, which reduces the likelihood of vane shaft <NUM> freezing and being unable to freely rotate. As a result, angle of attack sensor <NUM> has greater reliability.

Further, because angle of attack sensor <NUM> has more than one vent hole 60A and 60B in vane shaft <NUM>, venting through vane shaft <NUM> can still occur even if a single vent hole 60A and 60B becomes plugged.

While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined by the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the scope as defined by the appended claims.

Claim 1:
An angle of attack sensor comprising:
a housing (<NUM>) having an open end and a closed end;
a faceplate (<NUM>) positioned on the open end of the housing, the faceplate having an opening;
a vane assembly (<NUM>) extending through the opening of the faceplate;
a vane shaft (<NUM>) connected to the vane assembly and extending within the housing, the vane shaft having a bore (<NUM>) extending through the vane shaft; and
a bearing (<NUM>) surrounding the vane shaft; and characterized by
an annular vane shaft seal (<NUM>) positioned around and surrounding the vane shaft adjacent the bearing, and including an annular sealing element (<NUM>) with an annular lip (<NUM>), the annular lip being configured to contact the vane shaft and seal against the vane shaft and configured to move away from the vane shaft due to airflow within the angle of attack sensor; and
a first vent hole (60A) extending from an interior surface of the vane shaft to an exterior surface of the vane shaft between the bearing and the lip of the sealing element of the vane shaft seal, the first vent hole being in fluid communication with the bore of the vane shaft.