There is no universal definition of an 'Air Display' - which may alternatively be described as a 'Flying Display' - but one example of a statutory definition of the sort widely used is "any flying activity deliberately performed for the purpose of providing an exhibition or entertainment at an advertised event open to the public".
Whilst air safety is about the safety of both those in an aircraft and those on the ground, the usual absence of passengers except as volunteers means that the emphasis in the case of air display safety is very much on the safety of those on the ground. Whilst this is to some extent dependent on the way a display aircraft is required to be maintained and flown, it is also affected by the way in which the freedom to mount air displays is constrained. This summary will be concerned almost entirely with civil air display safety.
Air displays may be subject to safety regulation by either civil or military authorities depending on the location of a display and the identity of the organising agency. In both cases a risk-based approach is required. In the case of civil air displays, the ultimately responsible regulator may elect to devolve the oversight of applicable regulations - and sometimes also their detailed formulation - to approved persons or organisations with requisite experience. Such persons would be likely to be regularly and directly involved in air displays in either a professional or voluntary capacity. A display may be an event in itself or may take place as part of another event which may or may not be an 'Air Show'.
This will usually be an aerodrome to which normal aircraft access will have been temporarily restricted and the spectators confined to a specific area of that aerodrome which provides appropriate viewing of the display. A display will often take place in association with an Air Show but does not need to and an air display may take place at any approved location.
In respect of location, it is usual for any air display to require explicit permission from or on behalf of the applicable aviation regulatory authority. It is also usually necessary for the overall 'technical' responsibility for any air display to be vested in a named individual who, for the purposes of such responsibility at a specific event, will typically be accorded a title of or equivalent to 'Flying Display Director' (FDD). It is usual for relevant experience commensurate with such a role to be required for such a position. For a complex or extensive display, a Committee made up of appropriately qualified/experienced members may be formed to assist the FDD in the discharge of their responsibilities. The individual appointed as FDD will usually be expected to ensure that the risks arising from display aircraft in flight both within the display area and in its vicinity are appropriately mitigated. The UK AAIB has estimated that in the UK, "65% of display accidents involved (a single aircraft) crashing outside the area controlled by the organisers of the display" so the need to liaise with non-aviation authorities which have general responsibility for public safety is clear.
In respect of the direct risk if any display aircraft follows an unexpected/unanticipated flight path, the pilot of any civil or military aircraft taking part in a display will usually be required to hold a specific personal authority which is often called a 'Display Authorisation' or DA. Explicit requirements for the issue and retention of such authorisations are usually promulgated. The overall risk inherent in a display and the appropriate mitigation of that risk will usually be directly related to the type of aircraft involved, the extent to which display by that aircraft involves aerobatic or formation manoeuvres and the competence of the pilot, particularly with respect to their experience in terms of both its relevance and recency.
Risk Assessment and Mitigation
As in any other area of aviation, a formalised and fully-documented process of hazard identification, risk assessment and risk mitigation is usually mandated. The possibility of injury to spectators and uninvolved third parties in the event of an aircraft accident during a display will usually need to be assessed separately. Even though the mitigation of risk to each of these two groups will be derived from the nature of each approved 'Display Item' - a display sequence flown by a particular aircraft or group of aircraft - it is likely to be based on rather different considerations. One of the most obvious weaknesses of risk management has often been the failure of the designated FDD to ensure that they have sufficient prior knowledge of exactly what each 'Display Item' will consist of. Risk assessment and mitigation at air displays held under military regulations or in respect of military aircraft featuring in civil air display often appear to have more rigorous requirements than are imposed by civil safety regulators but this reflects the greater risk involved in the display of high performance military aircraft and also reflects the fact that all the pilots involved are not only professional with relevant experience but will almost always have been selected from within such a group on the basis of above average competence.
Most air display accidents result from either loss of control or mid air collision and very few involve fatalities except to the pilots involved. However, the fact that accidents involving civil air display aircraft involving death or serious injury to spectators or uninvolved third parties have sometimes appeared to be relatively rare has sometimes been seen to have engendered complacency in both safety regulators eager to delegate responsibility to those directly involved in displays who themselves have become complacent about risk too. For example, after a long period in which only display pilots or volunteer passengers were killed in air display accidents, a 'wake up call' came in the UK in 2015 when 11 people in vehicles on a busy road near an aerodrome at which an approved flying display was taking place were killed when the authorised pilot of a display aircraft lost control of his aircraft after breaching conditions inherent in the display approval and crashed.
The increasing tendency during the past 50 years for increasingly high performance military jet aircraft to appear on civil aircraft registers following fleet retirement from military service has introduced a new and sometimes overlooked complexity into civil air display risk assessment and mitigation. It was no surprise to many that the multi-fatality UK air display accident in 2015 involved such an aircraft.
Airworthiness of Display Aircraft
Although in the now distant past, un-airworthy aircraft were a significant cause of air display accidents, this is not the case today. However, airworthiness contributory factors are still sometimes identified in air display accident investigations and appear to be most often encountered when relatively few of an older aircraft type remain and/or aircraft are operated under a 'Permit to Fly' regime or similar regime which is less restrictive than the full requirement for issue of airworthiness certification.
Shared Situational Awareness
It is vital that all parties involved in air display activity have a shared situational awareness which should be coordinated by the FDD. These parties include the pilots taking part, the affected ATC and/or FIS units, personnel responsible for spectator control and relevant agencies directly responsible for public safety both in and outside the aerodrome or other designated display area. Of critical importance to all is an understanding of the approved 'display line' along which display aircraft will orient their manoeuvre(s). This will determine the proximity of both spectators and uninvolved third parties to risk from display aircraft and where a display is taking place at an aerodrome, will almost always be along a runway. Many civil and military agencies/organisations responsible for risk management have established requirements for minimum distances between the display line and the (parallel) crowd line. These are dependent on the nature of each aircraft, the speeds at which it will be flown and the degree to which any aerobatic flight manoeuvres will feature.
Although it does not have as its primary purpose the creation of shared situational awareness, the process of Pre Display Briefing of all who will be involved, which is in its own right a critical enabler of operational safety, is an important part of this. Once in possession of all the necessary information and having satisfied themselves that risk mitigation is adequate, a FDD should be expected to provide a written briefing to all parties, followed up by verbal briefings - conducted face-to-face or by telephone - on the day of the event in good time before it begins.
Monitoring Civil Air Display Risk
Being confident that safety regulatory requirements are adequate will depend on the extent to which achieved civil air display safety standards are understood. As with all other areas of aviation, this will depend on a combination of effective direct oversight and the recording and analysis of all operational safety-related occurrences. Over -dependence on the independent investigation of fatal accidents alone is likely to mean that opportunities to address risk management deficiencies which could have prevented such accidents have been missed. The UK AAIB Investigation into the multi-fatality UK air display accident in 2015 mentioned earlier has identified considerable evidence of failure to report display safety occurrences appropriately or at all, including pre 2015 occurrences featuring both the crash pilot and the (annual) air display at which the crash occurred. The importance of occurrence reporting in the explicit case of air display flying warrants a strong emphasis given that the extent of the community with real insight into risk, especially in the case of display aerobatic flight, is extremely limited. This importance is further heightened by the high proportion of 'human factor' causation found in air display crashes coupled with the absence of crash-proof data recorders in the majority of the aircraft which take part in such displays. However, there is also evidence that Safety Recommendations issued as the result of independent investigations of air show crashes have not always been accepted and, rather more worryingly, have been notified by the recipient as accepted and then the necessary action has not followed.
Comparative Safety Statistics
There appear to be few if any published regulatory targets which define an acceptable level of safety for civil flying displays. In parallel with this, little attempt appears to have been made to compare accident rates between display flying and GA flying in the same country or to compare display accident rates between countries which have a significant number of such approved displays annually (235 appears to be a typical figure for the recent past in the UK) as a basis for monitoring regulatory effectiveness. However, the investigation into the 2015 display accident in Shoreham UK did examine available data. Over a 10 year period, the data was found to show a rate of 1.5 fatal accidents per 100,000 hours in UK GA overall but, using the assumption that the average duration of a display item is 8 minutes, that the Display fatal accident rate in the same period was 456 fatal accidents per 100,000 hours. A rough comparison between the number of Display Items per fatal display accident showed that the US figure (5600) was approaching twice the UK one (2960).
Whether an Air Display is risk-managed by the military or civil authorities, it is a matter entirely within National competence, even in the case of EU Member States. The degree to which civil pilot competency and display oversight are outsourced to the potentially rather isolated 'display community' through a combination of the use of approvals of competent persons and some residual direct oversight varies considerably. For example, every approved display in the USA is attended by a member of the regulatory staff whereas in the UK only a small sample (as low as 1.4% of the 281 displays approved in 2014) are attended by a CAA representative.
Some examples of freely published Guidance Material are provided in 'Further Reading' below but it must be remembered that all Guidance Material is produced in the context of a specific national application and must therefore be interpreted accordingly.