Documentation:FIB book/Driver Crash Protection System in Formula 1: HALO

What is a Halo?

Halo Structure

The halo protection device was made mandatory in 2018 by the Fédération Internationale de l'Automobile (FIA), which is the governing body of the Formula series racing. This implementation followed the fatal accidents of Jules Bianchi after suffering severe head injury in the 2014 Japanese Grand Prix . This incident raised concerns over the lack of head protection found in open-cockpit vehicles.

The halo is a three-pronged T-shaped tubular structure attached to the car's chassis, also known as skeleton . Designed to protect drivers' heads, it prevents head and neck trauma by shielding against large debris, collisions with stationary objects, flying cars, car-to-car and car-to-environment impacts, and other external objects. These were designed to withstand the weight of a London double-decker bus . Teams are allowed to make cosmetic changes to the device as long as the structural performance remains unaffected.

Epidemiological Context

Due to the nature of motor-racing, Formula One (F1) and the FIA have worked to ensure the safety of the driver alongside the pursuit for extreme speed. The implementation of Armco barriers (metal guard rails intended to gradually slow vehicle speed upon contact), fire-resistant clothing and car seats, safe refuelling, the flag signalling code, and emergency aid vehicles are just some of the developments made for driver safety throughout the decades . But between the years are tragic accidents and crashes that motivate engineers and researchers to improve the safety of the racer through design changes.

The number one cause of fatalities during motor-races are head and neck injuries, and according to Lokkila , they represent 24 out of 52 F1 driver deaths over a span of 65 years (pp. 8). Being crushed by their car or violently ejected contributed to 9 deaths. After the implementation of Head and Neck Support (HANS) devices in the early 2000s, as well as other improvements to head and neck protection, death from neck and head-related injuries went from causing half to one third of all F1 fatalities in the 2010s. The most recent death of 25-year-old F1 driver Jules Bianchi in 2015 drove improvements to ensure the driver’s safety and protection from fatal head and neck injuries in the event that their car slid under another vehicle . Due to privacy concerns more specific data on individual driver's medical information is hidden by the FIA.

In “Cervical spine injury in rollover crashes: Anthropometry, excursion, roof deformation, and ATD prediction” , they state that “[w]hile rollover crashes are rare, approximately one third of vehicle occupant fatalities occur in rollover crashes [as the m]ost severe-to-fatal injuries resulting from rollover crashes occur in the head or neck region, due to head and neck interaction with the roof during the crash." To avoid additional drivers being injured in similar fashion, the cockpit of open motorsport vehicles must be protected as well as reinforced in a manner similar to a roll cage for closed cockpit motorsport vehicles. This protection would eventually come in the form of the halo device.

Technical Regulations

FIA Standard 8869-2018

This standard outlines requirements of additional frontal protection halos for the Formula One, Formula Two and Formula E series. In these championship leagues, the halo structure must be 7.0kg +0.05kg, -0.15kg and produced in Titanium Alloy Ti6Al4V Grade 5 (Section 4.2). The halo must undergo two quasi-static tests in which a 125kN load is applied in both. In the first test, the structure must not fail and deflection must be less than 17.5mm. Additionally, there must be less than 3mm of permanent deformation after the load is released for one minute (Section 6.1). For the second test, there must be no structural failure and deflection must not be greater than 45mm before the load is applied. The minimum energy absorbed during the test must be 7kJ (Section 6.2). Keeping the material, design and weight consistent throughout all race vehicles is important in ensuring a uniform level of safety.

Article 275 - 2021 Formula 3 Regional Technical Regulations

Article 275, Section 15.2 outlines the following: “The secondary roll structure, which is not considered part of the survival cell, must be positioned symmetrically about the car centre plane with its front fixing axis 975mm forward of the plane C-C and 650mm above the reference plane. The mounting faces for the rearward fixings must lie on a plane parallel to and 685mm above the reference plane.” Furthermore, Section 17.3 outlines the four static load tests that the halo must pass, in which the peak load is reached within three minutes and withheld for five seconds with no failure. Specific load requirements include 116kN downward and 46kN rearward at one position, 93kN inward and 83kN rearward at another, 150kN upward on two forward fasteners of the rear attachment or 75kN separately on each fastener, and 88kN upward and rearward on the front attachment, ensuring the halo can withstand loads in all directions. During the latter three tests, the survival cell may be supported on the condition that the strength of the halo is not increased. These tests ensure the roll structure's durability and compliance with FIA F3 safety regulations. This is crucial in ensuring that the halo can reliably protect drivers from major crash forces, while also maintaining design uniformity and test integrity.

Previous Work

The implementation of the halo as a mandatory safety mechanism in all future racing vehicles was based on a dynamic model created by the FIA. This model was developed based on 40 real accident reports from previous lethal and non-lethal crashes. The data from these was used to model 3 collision types: collision between two vehicles, contact between the car and the surrounding environment, and collisions with vehicles and debris . This model was used to conclude the impact of a halo on the survival rate of the driver which the FIA reported to be a 17% theoretical increase in survival rate based solely on the presence of the halo . However, these studies and accident reports themselves have never been published and have only been subject to internal peer review.

Jadhav independently carried out a Finite Element Analysis on an isolated halo which was subject to modal, dynamic, and static loading. The conditions applied to the halo were those established in the FIA’s regulatory standards. This study differs from that performed by the FIA in that it considers a collision against a concrete wall in its dynamic loading scenario and does not consider vehicle-to-vehicle collisions directly. This study concluded that all loads were permissible in accordance with the material properties, and thus the halo would not fail.

In a slightly more complex study, Shendge also developed an FEA model for the halo with a larger scope, which considers the attachment points as well as the use of multi-material construction. This study employed loading conditions 25% harsher than those established by the FIA. Despite this margin of safety, Shendge et al. concluded that the halo can manage loading without failure . This study also found a maximum deformation of 19.5mm at the center of the halo, which falls within the permissible limits and still allows enough space to stop a collision with the driver’s head.

The most in-depth available study performed on the halo is that of Cherukara & Yeddu, who considered the fasteners used in halos as well as the impact of welded joints in the particular alloy prescribed by the FIA. The aim of this study was to replicate the FIA’s standards as closely as possible so all loading, construction, and failure criteria were as required. Like Jadhav and Shendge, this study concluded that static forces and strains experienced by the halo fell within material and FIA standards. However, this study differs in the case of dynamic loading, finding that a total failure of the halo would occur at the welded joints in the case of a collision against a steel wall , highlighting the importance of fabrication as well as the large impact that modelling assumptions can have on a study’s conclusions.

Challenges and Controversies

The halo safety device since installed has been acknowledged as a breakthrough in driver protection in high speed racing, yet its implementation, effectiveness and aerodynamic nature remain up for debate. While the existing literature provides some insight into the biomechanics and structural performance there are still certain gaps, transparency issues and competing perspectives that highlight the need of continued research.

Visibility

There are also visibility concerns with the halo due to its vertical and horizontal bars. The problem here was that while there was extensive testing performed to confirm that the halo protected the driver from crashes, the effect of the halo on the driver during overtaking was not tested before it was introduced . Upon testing of the halo device by tracking the muscle activity of one of the authors, who was an amateur racing driver, it was found that during overtaking, there was an increase in the fatigue rates and workloads of the sternocleidomastoid and cervical erector spinae. With these results, it was inferred that the driver was forced to bypass the central pillar from his line of sight. Hence, this causes fundamental visibility problems while driving.

Aerodynamic Performance

It also has an impact on aerodynamics by affecting the flow of mass into the intake manifold, and therefore the power developed by the engine. The halo changes the airflow around the car and to the engine air intake, as well as the rear wing . These are negative effects on the air supply to the engine. Upon comparing race car designs before and after the introduction of the halo device, it was observed that the design of the air intake and the rear wing has not been updated to keep up with the installation of the halo. In addition, due to the location at which the halo is installed, airflow is directed away from the engine. Hence, engine performance is at a less than ideal level. So, it is important to keep this issue in mind so that future designs can take this into account and be designed in such a way that the impact on aerodynamics can be reduced.

Testing Methods: Limitations

Another issue is that most of the studies cited use Finite Element Analysis(FEA) in order to facilitate testing. While this is very useful, the drawback of this method is that it relies on idealized conditions which may not very accurately reflect real-world conditions such as multiple car crashes. Another example is that it relies on idealized material properties. However, in the real world, the carbon fiber and titanium materials that are used in the halo device have a probability of performing unpredictably under certain impact conditions. Hence, due the lack of real crash data, FEA predictions cannot be used completely accurately.

Alternative designs

There are also alternatives to the halo that were considered for installation to F1 cars. One such device was the Aeroscreen developed by RedBull advanced technologies was claimed to have similar impact protection with better driver visibility. In addition to not being aesthetically pleasing, the halo changed the makeup of F1 cars due to drivers not feeling like the cars were of the open cockpit model. The Aeroscreen, however, was more pleasing visually and had some functional differences, such as being heavier than the halo and having better driver visibility. It had a thinner middle bar and projected higher above the driver than the halo . While the halo was selected for F1, the Aeroscreen is now in use for IndyCars.

Future Research

While the halo safety device has improved driver protection and has increased the chances of survival from a crash by about 17% , ongoing research is essential to further build on the design, performance and functionality. Several potential key areas warrant further investigation to optimize the halo cockpit protection system.

Material Innovations

Halo at Formula 1 Exhibition, London

The latest halo designs are made of Grade 5 titanium and weigh about 9 kilograms, and the earliest variant weighs about 7 kilograms . Grade 5 titanium is usually used in the aerospace industry for its high strength and stiffness as compared to its weight.

Further research could explore other materials, such as alloys or composites, that may provide a higher strength-to-weight ratio, reducing the weight further. This would improve vehicle performance and potentially minimize aerodynamic impact.

Aerodynamic Performance

Investigating the aerodynamics of this safety device remains important. Future studies could focus on minimizing drag and maximizing performance and safety.

Recently, a computational fluid dynamics study on the 2019 halo model revealed that the halo device had an impact on downforce on the rear wing, directly affecting wheel traction and stability at high speeds , reinforcing the need for further research in aerodynamic performance.

Driver Visibility Enhancement

The 2019 model of the halo was found to increase fatigue and workload on the sternocleidomastoid and cervical erector spinae muscles due to the driver’s posture adapted as a result of the vision restriction from the halo , highlighting the need for further research on visibility loss due to the Halo.

In addition, some concerns have been raised since the introduction of the halo in 2017 regarding visibility obstruction, particularly in corners or low-angle viewing scenarios. Future research could target modified design options for the halo, increasing driver visibility without compromising crash protection.