A USAF Thunderbird pilot ejected one-eighths of a second before impact with the ground after realising that he had used the wrong altitude gate at the apex of a split-S manoeuvre during a display at the Mountain Home Air Force Base, Idaho, USA Open Day airshow in 2003.

The Fickleness of Human Judgement in the Low Level Display Area

Posted on 02 August 2015 by Des Barker

Display Flying Business
Display flying has not only become big business worldwide, but as in any theatre production in London's West Endor on New York's Broadway, it is also a major entertainment and spectator pastime. In the United Kingdom, particularly, it is interesting to note that airshows are rated as the second largest spectator sport after football and in the United States, such high-flying events are second only to Major League baseball as America's favourite family event, even ahead of NASCAR auto racing. Airshows are also one of the most hazardous and each year, aerobatic pilots are killed while displaying their aircraft at airshows and commercial demonstrations.

Display Flying Arena
There is no doubt that the most hazardous flight environment after actual combat operations, is the low-level aerobatic display arena. Based on the fact that God did not design man to fly and that it was man's desire to capture the romanticism of soaring from birds that led man into the third dimension - one for which we are ill equipped - man remains but a two dimensional creature.

The Weakest Link in the Safety Chain
Statistical analyses reveal that the human remains the weakest link in the display safety chain. Interestingly, in a review of a random sample of the 150 airshow accidents since 1952, as much as 80% were attributable to pilot judgement error, while mechanical causes such as engine failure and structural failure accounted for only 17% with weather making up the remaining 3%. Judgement error, subdivided into accident classifications such as Flight-Into-Terrain, Mid-Air Collisions, Loss of Control and Wheels-up landings remains a reality for all display pilots.

With rapid advances in technology, human physiology has been challenged to the limit and compensation by the human bodily processes has been hard pressed to cope. Extremely high closure rates of 1,500 kilometres per hour during head-on passes and high rates of descent by high performance jet aircraft as they pass the vertical downline 270º point at 30,000 ft/minute, test the pilot's anticipation and judgement of linear closure to the maximum.

Normal accelerations of +9g/-6g and extremely high roll rates of greater than 360deg/sec, impose huge demands on the human physiology and the ability to anticipate rates of angular change - all this while operating at low-level. This physiological shortcoming, coupled to the human's relatively slow reaction times makes it difficult for the human to make quick, consistent and repeatable decisions under pressure and imposes huge demands on decision making and anticipation. The only way therefore to survive in the modern low-level display environment is through expert knowledge and regular practice while complying with the safety regulations imposed by authorities.

Safety Statistics
However, all is not gloom and doom. Aviators the world over have been displaying aircraft safely to the public since the start of aviation and the risks inherent in display flying for the professional display pilot are not much more than for driving a car along the N1 highway. In fact, display flying remains one of the most popular and safest sport types practiced; this is primarily due to professional planning by airshow organisers in the main, the realisation by display pilots to remain absolutely professional and also the stringent requirements placed on display pilots within the realm of airshow flying. To quote the old clique', "if you want a perfect display flying safety record, you must stop all display flying". Due to the popularity of this sport worldwide, there is, of course, no real possibility of this happening.

Airshow accidents are nothing new. In fact, Orville Wright was involved with the first ever display accident in 1908 in which his passenger, Lt Thomas Selfridge was killed and since then, the causal factors of airshow accidents have remained consistent. Of particular interest was that in all 150 airshow accidents analysed, the aircraft were all flown by highly experienced pilots; there were no 'sprogs' cleared to display the aircraft.

The Fickleness of Human Judgement
They had all complied with regulations and had been authorised by competent Display Authorisation Officers. There was no negligence, no attempt at 'hot dogging' or blatant disregard of the rules. Their displays were professionally conducted - their only mistake was the fallibility of human judgement in making consistently accurate judgement calls - for which in 66% of the accidents, the end results were catastrophic and only 33% survived the airshow crashes. The display pilots were not only high time pilots, but in many cases were highly experienced test pilots or even professional airshow pilots. To be sure though, the one common denominator was that they were all highly experienced pilots.

In considering the medium in which airshows are flown, the sinister effects of density altitude, particularly critical in the 'hot and high' South African conditions, are well known to South African display pilots, particularly those flying with formation aerobatic teams. The example of the Trislander accident at Lanseria during the Africa Aerospace 1977 and the Hungarian MiG 29 in July 1998 when a Hungarian fighter pilot died when he crashed during a media preview a few days before the Kecskemet Airshow, bear blunt testimony to the insidious nature of density altitude.

In this particular case, the prevailing atmospheric conditions were rather extreme, a very hot and dry day with the outside air temperature of 35ºC. The pilot had performed low-level manoeuvres directly after takeoff, and then entered a left-hand turn for a low-level, high-speed pass. In the turn however, he realized that he had lost airspeed and height and then selected full throttle and then afterburner. Even the powerful RD-33 was unable to generate sufficient thrust to accelerate from the backside of the drag curve. A Hungarian MiG-29 instructor told television reporters that "the engine didn't produce enough power because of the density altitude".

In the case of the Trislander accident, company test pilot Peter Phillips demonstrated the aircraft on a hot, summer's afternoon. The airfield elevation at Lanseria is approximately 5,000 feet and with a prevailing temperature on the day of the accident at 30ºC, the density altitude was approximately 8,500 ft. Amongst other manoeuvres, a loop was included in the demonstration sequence. During the practice sessions it was evident to the pilot that the density altitude was critical to aircraft performance and the safe accomplishment of the manoeuvre. As it turned out, the sequence progressively lost energy with the result that at the apex of the loop, the aircraft was too low resulting in insufficient height to safely affect the recovery pull-out. It was estimated by reliable sources that the proverbial 'another 50 ft' might have been sufficient to avoid impact with the ground directly in front of show centre. The mandatory requirement for display pilots to meet their safety gate's requirements remains essential for display pilots and that at any stage of any manoeuvre, the display pilot must have an escape planned in the event of a judgement error or technical failure.

During the planning phase, the topography must be studied comprehensively and the 'lay of the land' plotted out in an effort to identify potential obstructions, hazards to the flight path and any interaction topography may have with maintaining the display line. This includes consideration of the effects of orographic turbulence generated by adjacent mountainous features and also the effects of density altitude, particularly critical for formation aerobatic teams. There are many aerial display teams who have their home bases at or near sea-level and often arrive at an airshow location without having had much time for rehearsals only to find that the 5,000 ft elevation of the new display location generates density altitudes in excess of 8,000 feet - the reputation of the team could be severely jeopardised by not being able to accommodate the increased power required for the increased density altitude, embarrassing at the least.

Making an error of judgement is not the sole domain or copyright of a certain individual, group or category of pilots. There is no display pilot that has survived the airshow circuit that cannot tell of 'close shaves' - most pilots have had incidents in which their own skill and judgement had let them down during their display careers which, but for the grace of 'Higher Authority', would have killed them. In the high threat environment of the low-level display arena, the use of the term 'pilot error' is not really considered appropriate and the term 'human error' seems to be more semantically correct. Unfortunately, the term 'pilot error' implies negligence whereas the term 'human error', more accurately captures the realities of display flying errors caused by the fallibility of the pilot to judge, estimate and anticipate accurately and consistently.

The inverted ribbon-cut went wrong when the pilot misjudged the clearance between his aircraft and nearby obstructions. He fortunately survived the accident after suffering serious injury. (Jurgis Kairys)

Heads of State often make mistakes or poor decisions, top surgeons have been known to amputate the wrong body part, general managers of international companies have caused the collapse of companies while accountants have made calculation errors ending in bankruptcy or the loss of millions of dollars. The bottom line is that every human is generally a weak decision maker, especially under stress. In the flight display realm, such stress may best be exemplified by 'life-threatening' factors like finding oneself at the top of a low-level, vertical manoeuvre with insufficient height or airspeed to complete the manoeuvre, or an excessively large 'nose-drop' while performing a low level aileron roll.

In some professions, one is able to hide or even cover up mistakes. However, in display flying, it may well be the irrevocable 'point of no return' that has been passed; there is no second chance. No excuse or hastily prepared political statement can put the record straight or negate the disastrous effects of an aircraft accident at a flight demonstration or airshow; the public outcry similar to that in the United Kingdom during June 2001 following a spate of three accidents, cannot be wished away. Two accidents at Biggin Hill and one at Paris over three consecutive days in June 2001, provided the "nightmare scenario" for the airshow world. But airshow accidents happen even to the most professional aerobatic teams such as the USN Blue Angels, USAF Thunderbirds, RAF Red Arrows and the Canadian Air Force Snowbirds, not to mention air forces and general aviation professionals worldwide, have all suffered losses due to accidents.

A Thunderbird's pilot incorrectly climbed to 1,670 feet AGL instead of 2,500 feet before initiating the pull-down to the Split-S manoeuvre. The pilot apparently flew by mistake to the MSL altitude used when practicing the manoeuvre at his home base, Nellis AFB in Nevada, which is 1,000 feet lower than the Idaho field elevation. The pilot ejected just eight-tenths of a second before impact, 140 ft above ground level, in full view of the 85,000 crowd. The pilot suffered minor injuries but the F-16, valued at $20.4 million, was destroyed.

The concern is that "errors of judgement" are not made on purpose but almost invariably result in an aircraft accident with, our without loss of life - there is no "second chance", there is not another opportunity to stop and then start all over again - like other professionals that would get an opportunity to maybe start a new career. Nevertheless, the fact of the matter is that statistically, approximately 67% of all aviation accidents, military and civilian, are caused by human performance errors. The display pilot community has not escaped these damning statistics, and the case studies presented in this book are particularly indicative of the fallibility of the human. Approximately 79% of all airshow accidents are attributable to MAN in one form or the other. The difference of 12% between general aviation's 67% and airshow accidents' 79% is indicative of the increased hazards existing within the low-level display arena. The remaining 21% being attributable to 'mechanical' and 'environmental' factors.

Historically, the safety statistics of airshow and aerial demonstration accidents are relatively disappointing, but considering the dynamics of manoeuvring an aircraft at very low level, this is not surprising. Although no accurate figures are available for display and demonstration accidents since the start of aviation, from random statistics available since 1952, more than 401 lives have been lost and more than 673 people injured in at least 118 random airshow accidents at a cost of more than 1 billion dollars in aircraft. In the final analysis, a display accident, excluding mechanical failures and environmental effects of course, can only be blamed on "human error", whether it be pilot's response/reaction time, anticipation, technique or situational awareness - these are the weak spots in the human physiology. It is essential for display pilots to be made aware of their shortcomings in this regard and for training to focus on strengthening the deficiencies - however, it is not possible to completely eliminate such deficiencies in the human physiology, the best we can hope for is to reduce the error margin through training.

The irony of air display crashes is that the pilots involved are professionals and in most cases, have a considerable amount of experience. Experience ranges from highly experienced combat fighter pilots, highly experienced test and demonstration pilots and world aerobatic champions to professional airshow pilots with more years and more hours experience than most people care to remember. Charlie Hillard, 58, who was killed in a Sea-Fury accident in 1996 at the Lakeland Fun 'n Sun, had logged 42 years and more than 15,000 hours of flight time. Wayne Handley, a former Naval Aviator, aerobatic champion, 'ag' pilot and aerobatic instructor amassed a phenomenal 25,000 hours of manoeuvring time in his 43-year aviation career before being injured in an airshow accident flying an Oracle Turbo Raven at the California International Airshow in 1999. His aerobatic ability earned him the title of California Unlimited Aerobatic Champion, not once, but three times. In April 1999 flying a G-202 he increased his own world record for inverted flat spins to seventy-eight turns. In 1996 he was presented the Bill Barber Award for Showmanship and in 1997 the Art Scholl Memorial Showmanship Award, two of the most prestigious awards in the airshow industry.

Most, if not all pilots displaying an aircraft in public are very experienced pilots, but accidents happen, for whatever reason. In the military, display pilots must have a significant amount of experience on type. However, on privately owned aircraft, the regulatory stipulations are less severe and demonstration pilots may not necessarily have many hours on type. The fact that they own the aircraft and have the necessary licence to demonstrate an aircraft, does not mean that they are totally 'au fait' their acquisitions, in fact, they may, in all probability be slightly short on the experience necessary to provide a low-level aerobatics display.

A display pilot doesn't just make an error, there is always some mitigating factor, some contributory cause that seduces the pilot's natural instincts, his peripheral cues, that overwhelms his information processing powers or anticipation, ultimately causing judgement errors. The challenge to improve airshow safety lies in an awareness to educate display pilots with respect to their, and the human's fallibility in decision making, anticipation, response, discipline and training.

Ever since the Wright Brothers' first successful powered flight at Kittyhawk 100 years ago, it was accepted that all flying would involve an element of risk, but in the world of display flying, a risk even more critical. With the growth of display and demonstration flying since then, those risks have multiplied as pilots and aircraft have been flown to, and often beyond, their respective limits. The number of hours flown annually at flight demonstrations and airshows is an insignificant percentage compared with the total hours flown worldwide. Although no accurate consolidated statistical data exists on international airshow accident rates, it is evident that the number of airshow accidents makes the accident rate for display flying excessive when measured against the universal norm of number of accidents per 10,000 flying hours. It can therefore be concluded that display flying in its various forms can be a hazardous activity for the pilots, the spectators and the public alike.

There are however, many successful display pilots that have survived the airshow circuit in spite of the inherent dangers - their survival can be attributed to concentrated focus on complying with the regulations in force and each pilot's own strict personal professional creed. The threats imposed by the low-level displays are ever present and there is no means to rid display flying of such hazards - there is only one way to alleviate the effects of the threats, and that is through knowledge, self-discipline and the development of practiced skills. Even then, there can be no guarantee that accidents will not occur.

Visitors to airshows will usually be treated to some truly memorable flying and because it is so polished, it is all too easy to forget the degree of skill needed to demonstrate an aircraft effectively. Pilots have to think carefully about showing off their aircraft to the best possible advantage while always being aware of the risks to safety. Altitude restrictions, the crowd line, residential areas, local schools and hospitals - everything must be considered and all this while being subjected to heavy doses of negative and positive 'g' and very high accelerations; analogous to being blasted off the pad at Cape Canaveral every few seconds in some cases. Whether it is a highly dynamic high-g display, displaying a heavy transport within the confines of a small display area, or even a competition aerobatic display, one thing is for certain, the skills required are world class. So, the next time you watch an airshow, remember that you're witnessing some of the world's best pilots at work, the aeronautical equivalent of the Olympic Games, a Broadway Show or a Festival Hall concert - all rolled into one.

"Any pilot, given the task of providing a display for the public, should set out to thrill the ignorant, impress the knowledgeable, and frighten no one". - Squadron Leader Ian Dick, former leader of the Red Arrows

To avoid the pitfalls of display flying, the pilot must focus with concentrated determination on the regulations and on one's own strict personal professional creed in order to find the tough narrow compromise between a conservative