This article addresses airworthiness function flights from the controller’s point of view. It is intended to give background knowledge about the specifics, expected crew and aircraft behaviour and to outline best practices for providing air traffic service (ATS) to such flights. The guidance provided shall not take precedence over applicable local procedures. It must be remembered that an airworthiness function flight is a non-routine activity (e.g. higher risk of incident, non-standard behaviour, etc.) and, as such, requires special consideration of the associated risks. The controller’s interference (issuing instructions and clearances, requesting reports, etc.) should be kept to a reasonable minimum to allow the crew to conduct their tasks properly. This is not a higher priority flight, however, and it is not supposed to disturb normal traffic flow. Therefore, proper coordination and timely dissemination of relevant information to concerned parties is essential for its safe and successful completion.
What to Expect
The following profiles are to be anticipated for aircraft undertaking airworthiness function flights:
Requests to use blocks of altitude rather than fixed flight levels;
Non-standard route (orbiting, zigzagging, etc.);
Steeper climb and descent than is typical for the aircraft type;
Requests for navigational assistance (vectoring) to release the crew from the navigation workload;
Various types of equipment failures, intentional flight system/components deactivation due testing, are much more likely to occur than during scheduled flights.
Provision of ATS
The following tips on providing ATS to airworthiness function flights are not to be considered exhaustive and shall not take precedence over local procedures:
Communication with the flight should be kept to the minimum required for safety of flight unless otherwise requested by the crew. Workload on such flights is higher than normal and interruptions may cause the need to re-fly a part of the flight.
Crew’s intentions should be clarified in as much detail as possible, preferably before take-off. In general, the crew is supposed to contact air traffic control before start up to discuss the conduct of the flight. If this does not happen, the controller should verify flight crew intentions as soon as practicable.
Extra caution should be exercised during position handover/takeover – make sure the relieving controller is fully aware of the situation and crew intent;
Try to accommodate flight crew requests. If this is not possible, an alternative clearance should be negotiated with the flight crew.
Normal operations are not to be hindered by the presence of an airworthiness function flight. In the case that traffic congestion is expected, that information is to be relayed to the flight crew. If the traffic situation does not permit adequate flexibility to accommodate the flight (i.e. meeting flight objectives), it would be better to re-schedule.
Some weather phenomena, in particular turbulence and CBs, may make it impossible to achieve the requirements of an airworthiness function flight. Therefore, the crew should be informed if there is a forecast for weather deterioration or if the aircraft is flying to an area with adverse weather.
If possible, increased separation parameters should be used. This would serve as a buffer in case of an emergency (which is considered more likely to occur on such a flight) or in case of miscommunication between the crew and the controller (e.g. if the aircraft performs a sudden and unexpected manoeuvre).
If the flight is conducted in the vicinity of an aerodrome, the appropriate ground staff should be notified. This would increase their situational awareness and possibly save time in the event of an emergency. Adjacent ATS units and sectors should also be notified, especially if part of the flight takes place near the boundary.
In the case that the crew requests vectoring, a couple of things are to be considered:
The aircraft should not be vectored too far from the destination aerodrome;
Conducting airworthiness function flights above prohibited areas or activated danger, temporary segregated and temporary reserved areas should be avoided whenever possible. Due to the flights’ specific nature (e.g. stall protection testing, engine shut down and restart etc.) there is a possibility that the crew may not be able to maintain level flight and the requirement for an emergency descent is also possible. These factors might lead to airspace infringement. If it is necessary to perform a flight or a part of it above such areas, the crew should be informed about the nature of the area (danger, prohibited, etc.) and its lateral and vertical limits. If applicable, the airspace user should be notified about the flight and appropriate coordination and other potential actions should be considered (e.g. temporary interruption of the activity in the danger/restricted area in case of an emergency descent).
Conducting an airworthiness function flight within a temporary restricted (TRA) or a temporary segregated area (TSA) does not generally demand much of the controller’s attention. Nevertheless, there are some issues to be considered:
The risk of an emergency remains higher the risks associated to normal operations;
Extra attention should be paid to flights below the TSA/TRA lower limit, as the airworthiness function flight might unexpectedly descend, leaving the reserved airspace.