Michael Slack’s Comments to NTSB re: Air Race and Air Show Safety
The following comments are submitted to the National Transportation Safety Board (“NTSB” or “Board”) pursuant to its invitation for public comments in connection with the hearing conducted on Air Race and Air Show Safety, January 10, 2012. Specifically, these comments relate to issues relevant to the Reno Air Race disaster (“Reno crash”) of September 16, 2011.
The undersigned is an attorney, aerospace engineer and active pilot currently representing several spectators injured in the Reno crash. These comments are based upon evidence and testimony presented during the January 10, 2012 hearing, prior investigations conducted by the NTSB as well as interviews with spectators and persons associated with race teams and information in the public domain.
The Reno Air Races are conducted on a closed ovoid course, defined by pylons, where multiple aircraft race together in a “first to finish” fashion. The basic concept is similar to oval track auto racing. In contrast, the Red Bull Air Race Series features single aircraft flying around a closed pylon course and the order of finish is determined by fastest time around the course.
The Reno crash presents a number of safety issues or risk areas for spectators and race pilots that are worthy of the Board’s attention. In summary, the basic risk areas include:
1) Spectator exposure – the risk that spectators could be involved in a mishap involving race participants;
2) Aircraft fitness – the risk that an aircraft could experience structural failure or loss of control when being operated at race airspeeds;
3) Pilot fitness – the risk that a pilot could become incapacitated and unable to operate the aircraft controls; and
4) Aircraft collisions – the risk that aircraft flying in close formation could come in contact.
The Reno crash sequence, while still under investigation, appears to have initiated after an elevator trim tab on a highly modified P-51 separated from the aircraft causing the aircraft to go out of control. The pilot was apparently incapacitated during the resulting sequence of events and was unable to regain control of the aircraft before crashing into an area occupied by spectators.
The NTSB’s Preliminary Report on the Reno crash describes the crash sequence as follows, “The airplane had completed several laps and was in a steep left turn towards the home pylon when, according to photographic evidence, the airplane suddenly banked momentarily to the left before banking to the right, turning away from the race course, and pitching to a steep nose-high attitude. After roll and pitch variations, the airplane descended in an extremely nose-low attitude and collided with the ground in the box seat area near the center of the grandstand seating area.”
At the time of the incipient event, the kinetic energy of the impaired aircraft was directed generally toward the spectator seating area, which is situated near the home pylon. A diagram of the race course submitted by the Reno Air Race Association illustrates that, on each lap, the energy of multiple aircraft converging on the home pylon is generally directed at the spectator seating areas. Therefore, any incident during the race that results in the loss of control of one or more race aircraft converging on the home pylon poses a serious risk of harm to spectators.
There are several historical examples of aircraft racing at Reno involving a loss of control. Documented loss-of-control situations at the Reno Air Races have occurred following engine failures, collisions involving other aircraft and structural failures.
Prior to 2011, at least two (2) race aircraft have experienced documented structural failures with resulting loss of control while racing. In 1998, a modified P-51 lost a left trim tab resulting in a high-g loss of control un-commanded upward pitch. The pilot managed to regain control after becoming unconscious and landed the aircraft (http://www.warbird.com/voodoo.html). In 1999, another modified P-51 experienced rudder flutter resulting in a catastrophic airframe failure.
Because control was regained by the pilot in the 1998 incident, no one was injured. The 1999 incident occurred just after the aircraft had begun its turn past Pylon 1, directing its energy away from the spectators. However, the resulting structural failure produced a complete loss of control and the aircraft impacted the ground approximately one mile east of the airport, and the wreckage debris was spread over a half-mile northeasterly path. Media reports stated that one person on the ground was injured, a home was damaged and power was knocked out in the neighborhood where the plane crashed. This incident underscores the distance that an impaired, uncontrolled race aircraft can travel after loss of control.
The obvious consequence of the race course layout and spectator viewing areas at Reno, when the litany of loss-of-control incidents at Reno is considered, is that spectators have long been and will continue to be at risk if an aircraft loses control when the energy of the racing aircraft is directed towards the spectator area. The fact that the race organizers have not taken the initiative to modify the race course and relocate the spectator areas to segregate spectators from the energy of the racing aircraft is surprising given the prior incidents. Had the 1999 incident occurred while the plane was converging on the home pylon, it is very likely that a mass disaster involving spectators and the public would have resulted.
A review of the incidents that have occurred at the Reno Air Races over the years seems to substantiate the conclusion that an uncontrolled race aircraft poses the greatest risk to spectators. The 1999 incident illustrates that this risk extends to populated areas proximate to the Reno racing venue. Mitigating or eliminating loss-of-control scenarios or confining the consequences to an area void of spectators or the public would therefore seem to greatly reduce the likelihood of another tragedy like that which occurred in 2011.
The testimony and evidence provided by the International Council of Air Shows and various air show performers is that air show aircraft are confined to a defined area or “box” and that area is offset from the spectators by an appropriate distance relative to the energy associated with the performing aircraft. The performing aircraft is also required to conduct its maneuvers parallel to spectators with no energy directed toward the spectator area while the performing aircraft is airborne. Consequently, the air show community has not experienced any spectator casualties since these criteria were adopted. Adopting a similar approach to energy management and segregation of spectators from the airborne aircraft would appear to present a significant risk mitigation opportunity for the Reno Air Races.
The incidents in 1998, 1999 and 2011 all involved structural failures on highly modified P-51 aircraft participating in the Unlimited class. Unlimited class aircraft operate at very high airspeeds, often exceeding 500 mph. The website for the Galloping Ghost, the aircraft that crashed in 2011, describes the aircraft as “heavily race modified” with a maximum airspeed of 550 mph at 5,000 mean sea level (http://www.leewardairranch.com/racing/galloping-ghost-specs). Persons familiar with the modifications to the Galloping Ghost have indicated that the elevator trim system, among other aircraft systems, had been extensively modified.
The Galloping Ghost, like most of the other Unlimited class aircraft, was highly modified from its original design and performance specifications. Such aircraft operate at very high airspeeds, resulting in very high dynamic pressure and aerodynamic loads. The inertial loads or acceleration forces (often referred to in “g’s”) imposed on the structures due to maneuvering are also significant.
Conversations with persons who possess extensive race and aircraft support experience with the Reno Air Races reveal rather perfunctory maintenance-style aircraft inspections with little or no substantive attention paid to evaluating the effect of aircraft modifications on static and dynamic structural integrity or the aircraft’s stability and control characteristics. This lack of attention to the cumulative effect of modifications on the structural integrity of race aircraft is borne out by the history of structural failures at the Reno Air Races.
Since a structural failure of a control surface or other critical aircraft structure is likely to produce an uncontrollable aircraft, mitigating the risks associated with the Reno Air Race format would suggest implementation of more rigorous substantiation requirements, similar to the procedures described by the Red Bull racing representative. The substantiation requirements should assess static, dynamic and aeroelastic characteristics of the modified aircraft and produce at least a 99% or greater probability that no critical structural failure will occur within the airspeed range of a given race class.
The 1998 incident bears very strong similarities to the 2011 Reno crash. The primary, and tragic, difference is that the 1998 pilot regained consciousness and control of the aircraft and landed safely. Both pilots obviously experienced very significant positive acceleration forces after the trim tabs failed. The altitude gained by both aircraft immediately after the tab failure substantiates the high positive acceleration forces. The aircraft reaction and resulting acceleration forces were confirmed by the pilot of the 1998 aircraft.
Aside from the risk of high acceleration forces imposed after a mishap or event, the race pilots experience sustained high accelerations while racing. The exposure of pylon-racing pilots to sustained and extremely demanding flight conditions was recognized by the organizers of the Red Bull series and their testimony revealed that special fitness criteria and screening were implemented at the initial pilot screening level as well as before races.
Given the rather obvious implications that pilot fitness has for maintaining aircraft control, more rigorous pilot fitness criteria should be developed by the Reno Air Race organizers to ensure that race pilots can retain control during races or in the event of an unexpected high g event.
Aircraft Collisions/Multiple Aircraft
The history of incidents at the Reno Air Races includes instances when loss of control was caused by race aircraft colliding (http://check-six.com/RTSMishapList.htm). At the Reno Air Races, aircraft are raced in multi-aircraft heats. The proximity of the aircraft, the course and the speeds involved make the likelihood of an in-flight collision very significant. Once a collision occurs, the resulting probability of a loss of control by one or more of the involved aircraft is high. The history of collisions at Reno substantiates this conclusion.
There is no risk of aircraft-to-aircraft collisions associated with the Red Bull format since there is only one aircraft on the course at a time. Thus, the extent to which collisions contribute to loss-of-control scenarios has been eliminated in the Red Bull format.
There is no apparent risk rationale utilized by the Reno Air Race organizers to determine how many aircraft should be racing in a given heat within a certain class of aircraft or at various airspeeds. A thorough risk assessment of the multiple-aircraft collision scenarios, where risk is assessed as a function of number of aircraft in a heat, would seem to yield important safety information that could mitigate the risk of collisions and a resulting loss of control.
1) Direct the Federal Aviation Administration to require the Reno Air Race Association, if not done voluntarily and sufficiently by the race organizers, to submit a revised course and spectator layout that segregates spectators and those not directly participating in the race from the energy of converging aircraft. The scheme adopted by the International Council of Air Shows, which orients spectators away from and parallel to the energy of performing aircraft, has resulted in no spectator injuries or deaths since being adopted.
2) Direct the Federal Aviation Administration to require the Reno Air Race Association, if not done voluntarily and sufficiently by the race organizers, to develop stricter and more comprehensive standards for determining the structural integrity and controllability of aircraft which operate at higher airspeeds. As a minimum, modified aircraft seeking to compete in the Unlimited class should receive an engineering assessment of fitness before being permitted to participate.
3) Direct the Federal Aviation Administration to require the Reno Air Race Association, if not done voluntarily and sufficiently by the race organizers, to develop stricter and more comprehensive standards for pilot fitness, including criteria that would ensure that race pilots are capable of operating the aircraft at extreme levels of momentary, very high acceleration forces and sustained levels of racing acceleration forces.
4) Direct the Federal Aviation Administration to require the Reno Air Race Association, if not done voluntarily and sufficiently by the race organizers, to prepare a risk model showing the levels of risk associated with different numbers of aircraft participating in race heats.
Slack Davis Sanger, L.L.P.
Michael L. Slack
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