FTS Telemetry Requirements Under Part 450

What Data You Must Capture, Store, and Be Able to Reproduce

Flight Termination Systems generate data throughout their lifecycle—from component acceptance testing through flight operations.

Under Part 450, this data isn't just a byproduct of operations; it's regulatory evidence that your FTS performed as designed and that your compliance demonstration remains valid.

This article details the telemetry and data requirements for FTS under Part 450, with particular attention to what data you must capture, how long you must retain it, and what format requirements apply.

The Regulatory Foundation

Part 450 Subpart C establishes performance-based requirements for flight safety systems.

Section 450.143 addresses Flight Safety System (FSS) requirements broadly, while the recently published AC 450.143-1 provides detailed guidance on design, test, and documentation requirements for Flight Termination Systems specifically.

The FSS comprises two major subsystems: the Flight Termination System (FTS) and the Range Tracking System (RTS).

Both generate telemetry data that must be captured, processed, and retained.

FTS Telemetry: What Must Be Captured

Pre-Flight Data

Before launch, FTS telemetry verification confirms system readiness.

Required pre-flight telemetry typically includes:

Command receiver signal strength and decoder status
Safe and Arm device state (safe, armed, or intermediate)
Battery voltage and current for all FTS power sources
Ordnance firing circuit continuity
Antenna pattern verification (where applicable)
System Built-In Test (BIT) results

This data establishes the baseline system state and confirms that all FTS components are functioning within specified parameters prior to launch commit.

In-Flight Data

During flight, continuous telemetry monitoring provides real-time system status and supports post-flight analysis.

Critical in-flight telemetry parameters include:

Command receiver AGC (Automatic Gain Control) levels—indicates received signal strength and potential link margin issues
Decoder lock status—confirms valid command signal reception
Battery voltage profiles—verifies power system performance under flight loads
Safe and Arm device status throughout powered flight
Fault indications or anomaly flags
Temperature data for thermally-sensitive components

Sample rates must be sufficient to capture transient events.

For parameters like receiver AGC, sample rates of 10 Hz or higher are typical to capture dynamic link conditions during vehicle maneuvers.

Termination Event Data (If Applicable)

If a termination command is issued—whether commanded or autonomous—additional data requirements apply:

Time-stamped record of termination command transmission
Confirmation of command receipt (if telemetry link survives)
Safe and Arm transition timing
Firing circuit activation sequence
Vehicle breakup indicators (acceleration discontinuities, loss of telemetry)

Range Tracking System Data

The RTS provides vehicle position, velocity, and time data used for flight safety analysis in real-time and for post-flight reconstruction.

Required RTS data includes:

Position (latitude, longitude, altitude) at defined sample rates
Velocity components (typically ECI or ECEF reference frame)
Time tags synchronized to a common reference (typically GPS time or UTC)
Tracking source identification (GPS, radar, optical, or blended)
Data quality metrics (dilution of precision, track status)

Position accuracy requirements derive from your flight safety analysis—specifically, what tracking uncertainty was assumed in your hazard analysis and whether actual performance met those assumptions.

The Flight Termination System Report (FTSR)

AC 450.143-1 defines the FTSR as the primary document through which FTS approval is obtained.

The FTSR consolidates system descriptions, analysis results, design data, reliability data, test data, and telemetry data into a single submission.

Key FTSR sections relevant to telemetry:

System description including telemetry interface architecture
Telemetry parameter list with measurement ranges, accuracy, and sample rates
Data format specifications (PCM frame structure, word assignments)
Test data demonstrating telemetry system performance
Calibration data for engineering unit conversion

FRACAS Integration

The Failure Reporting and Corrective Action System (FRACAS) provides closed-loop tracking of anomalies identified through telemetry data.

AC 450.143-1 references FRACAS as a method to manage test deviations and non-conformances.

A compliant FRACAS for FTS telemetry should:

Capture anomalies identified during pre-flight telemetry verification, in-flight monitoring, and post-flight analysis
Track root cause analysis and corrective actions to closure
Maintain traceability between anomaly reports, corrective actions, and affected hardware
Feed reliability data back into FTS reliability predictions
Support trend analysis across multiple flights

Data Retention Requirements

Part 450 requires licensees to maintain records necessary to verify compliance.

For FTS telemetry, this includes:

Raw telemetry data from each flight (typically retained for license duration plus three years)
Processed data products used for compliance verification
Calibration data necessary to interpret raw telemetry
Test data from component and system-level qualification and acceptance testing
FRACAS records for any anomalies

Data format matters for long-term retention. Proprietary formats may become unreadable as software evolves.

Consider archiving both native formats and standardized exports (e.g., CSV, HDF5) with sufficient metadata to reconstruct the original data products.

Practical Recommendations

Build your telemetry architecture with regulatory requirements in mind from the start.

Define your telemetry parameter list based on what you need to demonstrate compliance, not just what's convenient to measure.

Implement automated data quality checks that flag potential issues before post-flight analysis.

Establish clear data custody procedures that maintain chain of custody for regulatory evidence.

The operators who struggle with FTS telemetry requirements are those who treat data management as an afterthought.

Under Part 450's performance-based regime, your data is your evidence. Treat it accordingly.