Optimization of Aerodynamic Pressure Measurement for Aero-Engine Flight Test Using Pressure Scanner Valves

Aiming at the contradictions between the large number of sensors required for measuring multiple flow path 

parameters of test aero-engines and the limited onboard space in flight tests, as well as the failure of airflow 

pressure measurement caused by water ingress and icing in pressure measurement lines during flight, a method 

using pressure scanner valves instead of traditional pressure sensors for engine airflow parameter measurement, 

coupled with reverse purging and heating of the pressure measurement lines, was proposed. Airborne adaptability 

design for the pressure scanner valve system, design of high-pressure gas reverse purging, heating and control, 

and flight test validation were carried out.

Test results show that the method using pressure scanner valves for airflow pressure measurement and their 

reverse purging/heating function can effectively resolve the contradiction between insufficient onboard space 

and the large number of installed sensors, while avoiding measurement invalidation due to water or ice in pressure

 lines during flight, ensuring effective measurement of test engine airflow parameters. This method holds 

good application value in aircraft flight testing.

With the rapid development of aero-engine technology, the number and types of parameters requiring testing 

during flight tests are increasing. A single engine in flight test requires collecting hundreds of aerodynamic pressure 

parameters, accounting for over 50% of the total test parameters.The current mainstream testing method of one 

sensor per channel leads to significant space occupation by sensors and cables, conflicting with the limited 

installation space on the carrier aircraft.

Furthermore, to evaluate engine performance in high-altitude environments characterized by low temperature, 

low pressure, and low oxygen, the carrier aircraft often needs to fly at altitudes of 11 km, where the ambient 

temperature can drop to -40 °C. When flying through clouds containing supercooled water droplets at sub-freezing 

temperatures, icing often occurs on aircraft wings and inside engines.

Simultaneously, as the air entering the pressure measurement lines has high moisture content and low temperature, 

and the lines lack heating or effective insulation, internal water accumulation and icing easily occur due to the low 

ambient temperature, blocking the lines and consequently affecting aerodynamic pressure parameter measurements.

Addressing the issue of numerous sensors and limited carrier aircraft installation space, using miniaturized 

measurement equipment that meets testing requirements is very significant for carrier aircraft modification and 

flight testing.

Gas pressure scanner valves are widely used in aero-engine ground tests and wind tunnel experiments due to 

their miniaturization, high measurement accuracy, multiple channels, and convenient data communication.Using 

miniaturized, integrated pressure scanner valves to replace traditional sensors for engine flow field parameter 

measurement solves the onboard space limitation during engine adaptation modification. Their reverse purging 

function addresses line blockage from water and ice. Adaptability analysis and design with onboard systems like 

the test and power systems were conducted based on the scanner valves' characteristics, and the design's 

effectiveness was verified through flight tests.

Figure 1

Airborne Adaptability Analysis and Design of the Pressure Scanner Valve System

As pressure scanner valves were used for the first time in aero-engine flight tests, facing airborne adaptability 

challenges, corresponding analysis and design were necessary.To improve the measurement accuracy of 

aerodynamic pressure parameters and ensure successful flight tests, adding reverse purging and heating functions 

to the pressure lines was proposed.

Figure 2

Conventional Function and Performance Suitability Analysis and Design

The scanner valve controller can connect up to 8 units of 64-channel or 32-channel valves, providing up to 512 

measurement channels. Compared to traditional sensors, integrating multiple sensors into one module significantly 

reduces the space occupied by measurement equipment.For onboard use, to avoid pressure loss and ensure data 

accuracy, measurement equipment should not be too far from measurement points. Pressure sensors are typically 

installed in test nacelles. Due to the reduced space requirement, pressure scanner valves can be installed within 

test nacelles.

Furthermore, the scanner valve accuracy is ±0.05%, significantly better than traditional pressure sensors, enhancing 

the accuracy of engine performance assessment.

Airborne Test System Adaptability Analysis and Design

In flight tests, critical pressure measurement data from the test engine usually needs integration into the airborne 

test system for synchronized acquisition, storage, parsing, and display alongside other onboard systems.Most 

pressure scanner valves can only send control commands (e.g., for calibration, purge) based on TCP protocol, 

while pressure data can be sent via UDP or TCP. The original airborne test system only supported receiving data

 packets via UDP protocol.To minimize impact, an adaptive design was made primarily through software, enabling 

the scanner valve controller to switch between TCP and UDP protocols.

Figure 3

Pressure Scanner Valve Control System Design

The installation location of control system components must be considered. The IPC, control software, and gas 

source valve operation require manual operation, necessitating their placement in the aircraft's technical bay.

Figure 4

The control system design includes supply pressure, supply temperature, operational mode, and control logic.

Supply Pressure Design

Unlike ground test beds, aircraft layout results in long gas flow paths, causing significant pressure loss.According 

to specifications, the minimum purge pressure should exceed the maximum input pressure.

Supply Temperature

Under the aircraft's environmental control system, the cockpit and technical bay temperatures are high, typically 

maintained around 20 °C. Placing the gas source system in the technical bay keeps the purge gas at a relatively

 high temperature.

Operational Mode Design

Control logic design relates to usage requirements. The pressure scanner valve utilizes three functions for different 

flight test needs: "Run," "Calibrate," and "Purge."

Figure 5

Control Logic Design

As the controller can only receive most control commands via TCP, and only the "Ground Mode" command via 

UDP, software must switch between TCP/UDP protocols.

Power Supply System Adaptability Analysis and Design

The aircraft provides 220 V AC and 28 V DC power. The pressure scanner valve system requires 18-36 V DC, 

which can be met.

Flight Test Validation

After completing the design and modification of the airborne test system, flight tests verified the effectiveness 

of the pressure scanner valve system design.

Figure shows the pressure measurement results at several points behind the engine turbine during two flight 

tests under the same flight and engine conditions.It can be seen that after the aircraft climbed through clouds, 

water entered some pressure lines. As the ambient temperature dropped below 0 °C, water droplets formed 

inside the pipes, severely leading to icing and line blockage.

This resulted in the pressure in blocked lines remaining at its original state after engine speed decrease, with 

measurement errors reaching 160% or more, rendering measurements invalid. In contrast, pressure in unblocked 

lines decreased with engine speed.In Test 2, after climbing through clouds, a 1-minute purge using the designed 

high-pressure, relatively high-temperature gas source and control system cleared blockages in the pressure lines, 

effectively ensuring measurement data accuracyarman.

Figure 6（a）

Figure 6（b）