# Presentation: 235615

## QUALITY OF FLIGHT RECORDER DATA Filtered / Under sampled  Data and Post Processing Errors/Limitations

- SAE TOPTEC Vehicle Recorder Symposium
- June 4-5 , 2003
- Alexandria, VA

## Overview 

- Affects on Data Quality With Filtered Data and  Regulatory non-compliance;
- Affects on Quality of Recorded Data When Source is Under Sampled and Regulatory non-compliance;
- Problems Associated with Post Processing
- 	No Regulatory Requirements.

## Filtered FDR Data Background 

- Use of  Filtered Data as Input to FDR Identified in Early 90’s on Boeing 757&767
- NTSB Recommendations - Eliminate filter
- FDR FAR’s Revised in 1997 to Require Accuracy Under Static & Dynamic Conditions.
- Original FAA Survey – No Filtered Data
- Crash of American Airlines Flight 587
- AIRBUS Aircraft (A 300 & A310)Fitted with SDAC Supplying Filtered Flight Control Data to FDR

## FDR System ConfigurationA300 Flight Controls

- Flt. Cont.
-  Surface Sensor

**SDAC**
- ___   1____
- 1+0.434_ _*p *_ _
- _8 Hz output_

- DFDAU
- Flight Controls
- 2 Hz Sample Rate

**FDR**

- Flt. Cont.
-  Input Sensor

- Analog
- ARINC 429
- ARINC 573/717

## Determination of Flight Controls Sensor Characteristics

- Conducted Bench Test to Define Filter
- Conducted Aircraft Ground Test On AAL A300
- Determine Characteristics of Rudder Surface Sensor
- Determine Characteristics of Rudder Pedal Sensor
- Determine Relationship of Rudder Surface and Pedal Data

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## Problems With Filtered Data

- Filtering removes high frequency component of data that may not be fully recoverable;
- Highly dynamic parameters (e.g., flight controls) will be distorted by filtering;
- Filtering will introduce data latency that may vary as a function of sensor activity.

## Record Rate Higher than the Source Update Rate (Background)

- UK Air Accident Investigation Branch first identified existence of repetitious FDR data during Sept. 01, EMB-145, accident investigation.
- Recommendations (2002-01 thru 04), which call for:
- CTA of Brazil to determine nature and extent of anomalies, correct anomalies on existing and future A/C and demonstrate FDR data time history faithfully recorded.
- CAA UK ensure FDR installations meet regulations
- CTA alert other authorities of problem.
- CAA ensure other UK reg. A/C do not have similar problem.

## NTSB - Repetitious FDR data on Regional Jets

- NTSB review of the Regional Jet FDR data revealed similar problems on Dornier 328, Canadair CL-600 and EMB 135 and 145s.
- Recommendations (A-03-15 and A-03-16)
- Require aircraft to be modified to meet FAR sampling rate, accuracy and range requirements.
- FAA surveys fleet to determine if problem exists on other aircraft.

## Under Sampled Data FDR Data

## RJ FDR Recording Systems

-         (Simplified Block Diagram)

- FDAU
- Function
*Multiplex Inputs*
*Into ARINC 573/717*
*Serial Data Stream*
*Sampling Rate*
*8/sec.*

**FDR**

- Triaxial
- Accel.

- Analog.
-  Sensor

- Analog
- ARINC 429
- ARINC 573/717

**LRU**
*ADC*
*Internal *
*Sampling*
*Output Update *
*Rate.*

**DCU **
**Function**
*ADC*
*Internal *
*Sampling 10/sec*
*Output Update *
*Rate 5/sec.*

**DATA CONCENTRATOR UNIT**

## Data Latency & Repeat Values

## Evolution of DCU 5 Hz Signal

## Comparison of Original 20 Hz DCU 5Hz and FDAU 8Hz Data

## Original, 5 Hz DCU and 8 Hz (FDAU)(Expanded Time Scale)

## Problems When Data Source is Updated at Slower Rate than the Record Rate

- Data does not meet minimum FAR sampling rate requirements.
- Data may not meet accuracy requirements under certain conditions;
- Data latency (variable)
- Repetitious data point must be identified and removed

## Processing of Recorded Data

- Ground Readout Facility Validation
- Invalid Readout Software can lead to invalid conclusions
- Certification of FOQA/MOQA Ground Readout Systems??
- FDR System Documentation Standard
- Advisory Circular 20-141, FRCS
- Vendor Documentation
- Aircraft Manufacturer Documentation.