New Development of an Air Data System

At the time Simtec develops a new air data system based on the know-how gained with version 4 and 5 that has the following main features:

• Highly integrated multi hole sensor
• Smart type sensor
• Measures static pressure, impact pressure, angle of attack angle of side-slip, temperature
• Interface to connect an external TAT-probe
• Heater for de-icing
• Drainage system
• Dual-power design
• ARINC 429 interface or RS-485 Full Duplex Interface
• Aviation grade static pressure transducer
• Continuous operation -55°C to 71°C, start-up down to -40°C
• Extremely low transport delay below 20ms (including pressure lag and update rate of 100Hz)

We expect to have a first prototype by the end of the year. Prototypes for the sensor electronics, heater, ARINC 429 interface and software do already exist. The design is optimized to get very accurate air data down to very low airspeed (important for smaller sized UAVs). The sensor range can be adapted to the customers requirements to get the best performance.

Please contact Simtec for technical and commercial details.

Overview

An Integrated Air Data System (IADS) of the 5-hole type has many advantages over a conventional air data systems. IADS integrates the pitot probe, static ports, temperature probe, angle of attack probe, angle of side-slip probe, transducers, electronics and air data computer into one unit. Due to nature of the 5-hole probe no moving parts are needed for the measurement of the flow angles.

All sensors are positioned close to the place of measurement and all sensor data is directly digitized. This enhances system accuracy, eliminates system lag and increases reliability. Furthermore installation and maintenance is greatly simplified. Complicate plumbing, wiring and drainage is not necessary. The whole system is easily replaceable. Digitized data is provided to other avionics systems via the ARINC 429, or RS-485 bus.

Due to the high integration the device is very compact, light-weight and easy to install. The system needs no static port on the fuselage, therefore maintenance to achieve high accuracy is greatly simplified (no surface measurement and skin waviness checks needed).

Aerodynamic Corrections

A key advantage of Simtec's integrated system is that the air data computer (ADC) is able to apply correction to the pitot and static measurements at high angle-of-attack and side-slip.

With a conventional pitot-static systems the sensed pressure values are correct at zero AoA and AoS only. The larger the angle - the larger the error. Errors in the order of 10% of qo at 20° pitch and yaw angles are possible (see below NACA diagram). Simtec's integrated system corrects dynamic and static pressure based on wind-tunnel calibration as a function of measured AoA and AoS.

Probe Configuration

The probe has a modular design. Various configurations are possible:

Classic L-shape configuration

L-Shape with long boom configuration

Boom configuration

Probe Heater and Anti-Icing Capability

The main features of the ADP-heater are:

• Active heater design
• Maximum power of 484 Watt
• Maximum temperature is controlled by main data processor
• Maximum temperature is configurable by software
• Heater current is measured and annunciated on ARINC
• Surge protection
• Power optimization possible

The maximum power consumption of 484 Watt is used only during short intervals or in a worst case scenario (max. ice at max airspeed). Normal average power consumption is between 60-120 Watt.