1. Title of the invention

Improvised Instrumentation System Design for Airbrake Control Surface on Aircraft

2. Field of invention

This invention relates to the methodology of accurate and efficient position indication of airbrake system on aircraft.

3. Use of invention
This invention finds its applicability in the Precise and Intuitive position indication of the airbrake on any aircraft

4. Prior art

The two types of instrumentation methodologies were generally used:

• Micro strip gauge interfaced with discrete position sensor (micro switch).
• Electromechanical position indicator interfaced with the analog position sensor.

5. Draw backs of prior art

In micro strip gauge system, where airbrake position indicated by discrete magnetic indicator using strip gauge mechanism as IN and OUT, the extent of Air brake surface extension and retraction was not available and was unknown to pilots and ground crew during OUT indication.

In aircraft where Electro mechanical indicator were used for airbrake position indication, IN and OUT tolerance band was = 6 deg due to which airbrake in Fully IN and Fully OUT positions could not be indicated correctly. Also for given offset errors of the actuator, any incomplete retraction was displayed as IN providing erroneous data to pilots which is critical during landing and takeoff. Maintenance of Electro mechanical indicator is time and cost consuming. Synchronizing of indicator and sensor on aircraft for IN and OUT position was tedious and aircraft dependent to bring the pointer to IN and OUT bands. Fig:l Micro strip gauge indications

6. Comparison between prior art and present invention

The current design provides highly accurate cockpit indication of airbrake position with continuous position indication, IN and OUT indications which helps the ground crew for ground evaluation on ground before flight clearance. It also provides the on board indication to pilots

7. Aim of the invention

Aim of the invention is to provide an electronic instrumentation system in the aircraft for airbrake surface indication instead of using conventional magnetic strip indicator or electro-mechanical indicator.

8. Summary of the present invention

The Improvised Instrumentation System Design which is implemented on the trainer aircraft provides highly accurate data to the pilots and ground crew during ground evaluation and flight trials. Maintenance and calibration is not required. This scheme can be implemented for any flight control surfaces like Flaps, Elevators, Ailerons, Rudder or trims which require accurate position on the aircraft.

9. Brief description of drawings

Fig 1 Micro strip gauge indications
Fig 2 Electromechanical indicator
Fig 3 Detailed description of the air brake position system.
Fig 4 Extreme position indications
Fig 5 Design Implementation
Fig 6 to 9 Different Position Indications
Fig 10 Airbrake system performance recorded data

10. Statement of invention

This invented design provides highly accurate data regarding the position of the airbrake on the aircraft. This provides all the functionality of magnetic strip indicator for extreme IN & OUT positions and continuous indication of the position of Electromechanical Indicators. This design provides on board data which can be easily recorded for further analysis. It eliminates the ambiguity in displaying the extreme position and increased the accuracy of the system. Maintenance and calibration requirements are eliminated for airbrake system

11. Detailed description of invention

Instrumentation System Design - Schematic and LRUs:
Figure 3 provide the detailed description of the air brake position system. FIG 3 ; AIRBRAKE POSITION SYSTEM INDICATION

Micro switch installed on aircraft which is designed to provide 28V output to sensor processing unit when Air brake is moved from closed position. This discrete output replaces the strip gauge mechanism indication and provides the input for IN and OUT indications on Active matrix Liquid Crystal Display (AMLCD) to take care of the extreme position Indication without any ambiguity to the Fig:4 Extreme position indications pilots and ground crew.

The Position sensors with suitable output range and adjustable between 0 to 300 deg was selected. Experiment was carried out on position sensor with different excitation voltages and output of the position sensor was recorded. 5V excitation voltage was suitable since 5V excitation spare channel was available in SPU. The same was selected and position sensors was interfaced to SPU and performance found satisfactory in lab environment.

Implementation:

Both discrete and Continuous position input of air brake were considered for building the logic in SPU and AMLCD unit to accommodate for the display indication from 0 to 60 deg. The combined logic of discrete input from Micro switch and analog input from the Airbrake position sensor implemented in SPU and AMLCD is given below

Figure 5 : Design Implementation

Data Processing algorithms:

A set of data processing algorithms are implemented to process the data from the sensors. Bands are implemented on the extreme indication positions of the airbrake surface to offset the actuator tolerances.
• (0-2) deg - IN position, (2-58) deg - Intermediate position
• (58-60) deg - OUT position (To accommodate changes input due to aircraft vibration & sensor tolerance and etc.)
• (>60) deg - Out of range indication and etc (Ref: Fig 6- 9)
Step filters are implemented to avoid the jerkiness and fluctuation and ensure the smooth indication on the display. Failure of micro switch and analog sensor were taken care to indicate on the display.

Display Methodology:

The designed and implemented Airbrake position indication on AMLCD to provide the continuous positions as sensed by the SPU from the 0 to 60 deg from the airbrake position sensor between IN and OUT position of micro switch is as given below .

Fig 7: Analog voltage .Fig 8: Analog voltage Fig 9 Failure indication
not in sync with IN out of range (>60 deg) both Discrete and analog
indication (0-2 deg) for OUT indication output

Performance of the Instrumentation System:

The data from both the discrete and analog sensors are acquired during the flight trials and analysed. The following figure shows the consistency in the performance of the system and the data is found to be of better accuracy when compared to the earlier instrumentation systems. Accuracy: 1 deg

Fig 12: Airbrake Discrete and Analog output after standardization and synchronization with IN and OUT position

Name of the Applicant: Hindustan Aeronautics Limited, ARDC division. Application No.:

12 Drawings & worked examples
Fig-1 to Fig 10 attached in the along with detailed description to airbrake system.

Claims

1. The Improvised Instrumentation System design provides accurate data and efficient indication to pilots and ground crew for flight trials and ground evaluation.

2. Accurate IN and OUT indication to the pilots eliminating the ambiguity in airbrake surface position at extreme ends.

3. This scheme can be implemented for other flight controls surfaces for position indication on aircraft.

4. Standardization made easy for ground evaluation and flight trials.

5. This design can be implemented on any aircraft irrespective of type of the aircraft.

6. Position data can be easily sent & recorded on any format like 1553 and ARINC429