The trials instruction

The TI is the main output from the planning phase and is the document used to authorize and control the trial. In the TI is contained all the information that a senior person in the trials organization needs to be able to understand what is being planned and allows him or her to approve the trial. Thus the document needs to define the test methods, test procedures, and test conditions that will be used. The test methods and procedures are often standard and only require a reference to other documents which define them. The test conditions, on the other hand, always require careful thought as these vary with the trial being made. It is not simply a case of defining the target conditions for the trial but rather a range of permissible values of variables is defined so that the trial can proceed even if the exact desired conditions are not present. The TI also details the trials programme including such aspects as the size of increments in control parameters between successive tests and the criteria for progressing to the next test or phase. A key element of the TI is a section which details the safety precautions that will be taken. This safety section comes mainly from the risk assessment which is also included in the document so that the authorizing officer can ensure that the process has been conducted correctly.

1.2.3.1 Sortie planning

Each sortie in a test programme requires careful planning to ensure that the flight follows a safe progression and that the maximum amount of high quality data is gathered in the flight time available. Where possible tests are conducted concurrently, for example, information on flight control positions and engine bay temperatures can be gathered during level flight performance tests. This clearly requires careful liaison between the different parts of a flight test organization if they are all involved in the same trial. The individual test points are organized such that successive points can be achieved quickly. The principle is that no flight time is wasted. It is better to have too many test points in a sortie plan than too few but the plan still needs to be reasonable and achievable. The possible effects of weather are considered as well so that tests are organized into high level and low level sorties to ensure that time is not wasted if the cloud base is low. For each sortie the go/no go criteria is decided upon at the planning stage, for example, this might be a minimum light level or a maximum wind strength. Part of the sortie planning procedure is to produce a written flight brief, which will be used during the pre-flight briefing to ensure that all trials participants are fully prepared. Included in this brief will be the flight safety points, priorities, limitations, go/no go criteria, possible alternate tests, criteria for stopping the tests, and responsibili­ties of individual participants.

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