Aircraft Angle-of-Attack Sensor Deflector Design
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Solution Overview
Problem
Angle-of-attack sensors on aircraft experience measurement errors due to sudden stall phenomena in transonic flows, leading to reduced safety as the flow becomes locally supersonic, causing errors in angle measurement, which existing swept canopies only delay but not prevent.
Innovation Solution
The incorporation of deflectors on the wind vane extending from the leading edge over part of the lower and/or upper surface, which straighten the flow and prevent sudden stalling, along with heating means for deflector and sensor association through thermal conduction to manage icing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If swept canopies are used to delay stall, then the risk of sudden stall is delayed, but the stall phenomenon is not canceled and measurement errors still occur
Solution Approach 1:
The wind vane is segmented into multiple functional zones: the base portion and the deflector portion. The deflector is divided into multiple deflector elements that can be independently positioned. This segmentation allows different portions to perform different functions - the base provides structural support while the deflectors actively manage flow separation to prevent stall.
Solution Approach 2:
Deflector elements are introduced as intermediary components between the base and the free stream. These deflectors act as mediators that redirect and control the flow field, preventing direct adverse interaction between the base and oncoming flow that would cause stall. The deflectors mediate the flow path to maintain attached flow over the base.
2Object-affected harmful factors
If protection is added to the wind vane base, then protection against supercooled water crystals and frost is provided, but a local protrusion is created that accelerates flow and causes vane stalling
Solution Approach 1:
The protective structure is segmented into the base and separate deflector elements. Rather than having a monolithic protective canopy that protrudes, the protection is divided into the base (which may have protective coatings or heating) and the deflectors (which manage flow). This segmentation eliminates the protrusion problem while maintaining protection capabilities.
Solution Approach 2:
The deflector elements serve as intermediaries that protect the base from direct exposure to harmful flow conditions and icing particles, while simultaneously managing the flow field to prevent stall. The deflectors mediate between the protected base and the free stream, allowing protection without protrusion-induced stall.
3Speed
If the wind vane operates in transonic flow, then it can function at high speeds, but local overspeed causes sudden stall phenomena
Solution Approach 1:
The deflector elements can be positioned at different angles and locations to dynamically adapt to varying flight conditions. The deflector configuration can be adjusted based on Mach number and angle of attack to maintain optimal flow attachment across the operating range, enabling stable operation from subsonic through transonic regimes.
Solution Approach 2:
The deflectors act as dynamic intermediaries that actively manage the transition to supersonic flow and prevent shock-induced separation. By positioning deflectors appropriately, the flow is gradually accelerated and managed through the transonic regime, preventing sudden stall phenomena that would otherwise occur at high speeds.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The deflector design effectively prevents sudden stalling of the wind vane, enhancing measurement accuracy and safety by maintaining flow stability and protecting against icing, thereby improving the reliability of angle-of-attack sensors in challenging aerodynamic conditions.
Implementation Method 1
The or each deflector is spaced from the base (12a) so that the flow passes in part between the base (12a) and the said deflector(s)... the deflectors act as flow straighteners and prevent the entire sensor canopy from suddenly stalling
Implementation Method 2
the means for heating the or each deflector are associated with the means for heating the sensor by thermal conduction
Data Source
AI summary
This angle-of-attack sensor, in particular for an aircraft, of the type including a sensor body (11) on which a wind vane (12) is mounted movable in rotation by a flow, is characterized in that the wind vane (12) includes at least one deflector (13, 14) extending from the leading edge of this wind vane over at least part of the intrados and/or extrados thereof.