All testing of avionics and weapons systems requires that the tester prove the performance of the system under test by measuring its performance against some known quantity. This known quantity falls under the heading 'truth data,' or time, space, position information, affectionately known as TSPI. The concept is slightly different from the testing accomplished on the vehicle side of the house. In loads testing for example, the tester relies on instrumented parameters to determine the 'true' bending and torsion on a member. The accuracy of the result depends entirely on the accuracy of the instrumentation system. The tester in this case is measuring the truth and comparing this answer to the predicted results. In avionics and weapons system testing, we still collect instrumented parameters such as latitude, longitude, and altitude, but we compare them to an outside reference, a truth. This truth is generated by calibrated reference systems such as cinetheodolites or an on-board global positioning system (GPS). It is important that our truth system be accurate enough to measure the expected performance of the system under test. Unfortunately, all too often testers use whatever TSPI system is available without considering the impact on the results of the test. In some cases, highly accurate avionics systems are being measured by TSPI systems that are not as accurate as the system under test! This chapter discusses what systems are available, how the results can be improved upon, and defines a common-sense approach for identifying required test assets.

The flight testing of communications systems is avionics flight testing in its most basic form, but it does illustrate many of the common factors seen in the more complex systems. The testing of communication systems occurs more often than one would expect. Radios are often upgraded, which requires a flight test program, but these upgrades may be many years apart. What occurs on a more frequent basis is the relocation of antennas or the installation of stores or other obstructions that may affect communications. Some flight testing may be required to ensure that no degradation of communications due to these modifications has occurred. Radios, because they transmit as well as receive radio frequency (RF) energy, are also key players in electromagnetic interference/electromagnetic compatibility (EMI/EMC) testing. This testing is addressed later in this chapter.

The part 23/25 in the title of this section refers to Federal Aviation Administration (FAA) and European Aviation Safety Administration (EASA) (formerly Joint Aviation Administration) definitions of aircraft types. Part 23 aircraft are defined as normal, utility, acrobatic, and commuter category airplanes; part 25 defines transport category airplanes. The discussions in this section are applicable to part 27 (utility helicopters) and part 29 (transport helicopters) as well as military installations. The systems in this section have, for the most part, been developed for the general and commercial aviation market, or mandated for use by the state authorities. The emphasis is on compliance with the applicable certification requirements and sometimes spent on the civil certification process, its history, and a review of the types of documents that you will need to reference. The discussion continues with hardware, software, and safety considerations and the requirements for each. Controls and displays and human factors, which are considerations for all test plans,were discussed in detail and documents to assist in the test planning process will be identified. The systems which are covered include weather radar, global positioning system (GPS) civil certifications, reduced vertical separation minima (RVSM), terrain awareness warning systems (TAWSs), traffic alert and collision avoidance systems (TCASs), flight management systems (FMSs), landing systems, autopilots, and integrated navigation systems.

Radar evaluation is perhaps one of the most exhaustive, complex, and challenging types of testing that the flight test engineer will encounter. As with all other avionics and weapons systems, it is imperative that the evaluator possess a basic knowledge of radar and an indepth knowledge of the system under test. The purpose of this section is not to repeat what is contained in the aforementioned references. Radar theory is covered only to make the test procedures understandable. This section will review radar fundamentals, identify radar modes of operation, examine the methods of test for these modes, and address any special test considerations.

In this chapter we will discuss the system aspects of weapons integration. The chapter is not concerned with loads, flutter, captive carry, or station clearance issues, although they will be touched upon during the discussions. As usual, there are some references that are available to the evaluator, and these will be quoted where necessary.