What
is Telemetry
INTRODUCTION
The South African Air Force's Test Flight and
Development Centre (TFDC) at Bredasdorp, conducts the major portion of experimental and
Research & Development flight test work in the RSA.
The strategic positioning of TFDC with a
large volume of airspace, allowing for flexibility during flight testing, as well as its
capabilities and facilities are the envy of many foreign Aerospace Companies.
TFDC was officially established on 10 August
1975 at AFB Waterkloof. With the entry of the RSA into the Aerospace Industry and the
establishment of the sophisticated technical facilities of the Overberg Test Range (OTB) for the space programme, TFDC was relocated in the Overberg in 1987
and has during the past 23 years, with a relatively small work force, flown approximately
30 000 flying hours and conducted more than 2 000 flight test programs.

An Aerial view of TFDC with the main runway in the foreground
(10 000ft) and the secondary runway in the background. (Photo: TFDC photographic
section)
CAPABILITIES
General
The scope of the projects at TFDC, vary from
short to long duration, low to high cost, moderate to high technology, and low to high
risk. Some of the tasks currently include the qualification of the locally developed
maritime surveillance suite, the locally developed electronic warfare suite, performance
tests, flutter tests and various smart weapons.
Denel's Overberg Test Range also plays an
important part in the conduct of flight test trials. Accurate spatial positioning, optical
and radar tracking of airborne targets is provided. Cine-theodolites are located
throughout the test range for visual tracking of aircraft and released stores, while the
laser track mount and Doppler tracking radar's are used for accurate multi-target
tracking.
Product Support
To ensure proper support and the highest
possible success rate the capabilities and skill of technical telemetry personnel plays an
important role. Furthermore the dependability and availability of the telemetry equipment
utilized during the flight test is considered as equally important.
To ensure the latter, TFDC has adopted the
Product Support Supplier (PSS) concept for the maintenance, support and operation of the
telemetry ground station and maintenance of approximately 50% of the airborne telemetry
equipment. Reunert Defense Logistics (RDL) is presently contracted as the PSS for the
telemetry system at TFDC.
TFDC has, during 1997, launched an active
program to improve the TM data acquisition capability by providing the state-of-the-art
equipment including data processing, data displays and to meet future test programs.
The TM data acquisition system improvement program includes the planned procurement of
equipment to replace old or obsolete equipment and equipment for system checkout and
verification.
The telemetry ground station, due to the
earlier weapons boycott, comprises equipment from various suppliers.
The present capability of the ground station includes reception of telemetry data
in P-band and/or S-band.In both bands, a dual receiver approach with diversity combining
is utilised. For the P-band frequencies, Microdyne and ATNE equipment are used with manual
tracking and for S-band ATNE receivers and diversity combiner in conjunction with a
1.5 meter parabolic dish antennae capable of auto tracking. In the S-band the
capability also exists to relay video data from an aircraft that is often used during
release clearances and providing the client with a visual of what is happening with his
product.
The upgrade process for the ground station
includes processing and display of 1553 format data and new more advanced data recorders
to name but two. It must be mentioned that any change to the ground system is always
measured against the total telemetry system, meaning that compatibility and synergy with
the rest of the telemetry system must always remain.
Airborne Telemetry
The flight test instrumentation section at
TFDC is responsible for the design, installation and maintenance of all telemetry related
tasks and onboard installations.
This section is also in the process of
upgrading certain equipment, which include new data recorders and development of a
"miniature" telemetry strap-on pack that utilises a processor for first level
processing and accumulation of required data. The main objective of this development is a
decrease in weight and installation time and an increase in capability.
This concept has been in existence since the
early 80's.What is however significant is the fact that TFDC is moving in a direction that
is vital in flight testing, namely, more cost-effective means of data collection.
The onboard telemetry section is also
supported by a comprehensive and highly skilled R&D section who is responsible for the
design and manufacture of all electronic circuitry required for signal conditioning and
display requirements.
Data Reduction
The facility responsible for data reduction
and real-time processing and display of telemetry data received a mayor boost a few years
ago with the acquisition of an OS90 system. Apart from its vast processing power it also
extended TFDC's capability to display real-time telemetry data to the customer giving him
visibility of what is happening with his product and thus making him part of the total
process.
The telemetry ground station and the OS90 in
the data reduction room is linked via fiber optics to ensure proper high speed transfer of
data from the receivers to the processor for real time data processing and display.
To ensure availability as well as
supportability, TFDC has signed a back-to-back contract with L3 Communications that
includes notification and correction of software bugs as well as any configuration
changes/redundancy of components.
APPROACH TO FLIGHT TESTING
Flight Test Safety
The hazardous nature of flight testing places
a high premium on safety of flight. To ensure that all flight tests are conducted
with the safety as a key factor, TFDC uses a System Safety Specialist to manage the flight
test safety aspect as a systems engineering process. This ensures that all possible
negative influences on the safe conduct of a flight test is eliminated or at least made
visible.
By utilising this approach and taking into
account the exploratory nature of the flight test task, TFDC has managed to achieve
impressive flight safety statistics with extremely low flight test incident rates.
Flight Test Management Process
Director System Integrity, via the Staff
Officer Test Flying (SOTF), functionally controls TFDC. This in effect results that all
flight testing conducted by TFDC is tasked by SOTF. At TFDC the scheduling of the tasks
are managed by the Flight Test Director. During a trials management meeting, which is held
once a week, all tasks are concepted, prioritised and task leaders appointed. It is the
responsibility of the task leader to ensure that the rest of the process is executed with
the flight test report as the end result. To achieve this, there are various steps that
must be followed to ensure success.
Figure
1 gives a broad outline of the process.
To ensure that the total process is optimised
and cost effective, TFDC management believes in innovative thinking. This approach can be
explained as follows:
In order to survive in today's marketplace,
an organisation and that includes TFDC, must above all, be successful in innovation. By
innovation in flight testing it is meant the ability to create new ideas that are
critically judged, modified and then finally used to establish new and better approaches,
methods, or devices.
Having said this it is also important to keep
in mind that for instance to get from point A to point B one can use a VW or a Cadillac,
meaning that care must be taken that when something is good enough it should be
implemented and used. Remember that 'best' is the enemy of 'good'.