Tech Draft: Explaining F1 Technical Directive on porpoising

formula 1 cars porposiing td f1

In many ways the 2022 Formula 1 season has lived up to most expectations and much of the field has enjoyed a much closer competitive balance, but the earlier stanza to the new era of technical definition was defined by a phenomenon that many of the teams did not anticipate, so much so that it required the intervention of the FIA – the return of porpoising.

In June of this year Formula 1’s governing body, the FIA, announced in the aftermath of the Azerbaijan Grand Prix, that it intended to issue a technical directive to more closely scrutinise planks and skids in terms of their design and observed wear, and to define a metric based on a car’s vertical acceleration to give a quantitative limit for an acceptable level of bouncing.

Triggering the TD was because many of the competitors were significantly impacted by the ground effect induced porpoising phenomenon and unreasonably violent floor strikes with the ground due to the need for significantly higher spring rates in comparison to those used in more recent years

Thanks to the FIA’s willingness to provide Grand Prix 247 with a copy of the current revision of the technical directive, TD039 Aerodynamic Oscillations and Car Grounding Issue E which was issued on September 26 and came into effect at the Belgian Grand Prix I can provide a synopsis of the TD so that our readers might better understand the reasons for its issue, and its content.

Before analysing the TD it is important that I acknowledge that TD039 is covered by a note stating that the document is strictly private and confidential and for the exclusive use of the FIA, the F1 Teams and the PU Manufacturers, and for that reason I will not be including copied extracts from the document, nor will I be posting any links to an uploaded copy of it.

Preamble to porpoising issue

porpoising formula 1 porpoise f1 ferrari gif

The porpoising preamble begins by noting that following the circulation of an earlier revision, teams had shown the FIA central plank designs that they felt would have clearly contravened the regulations and that as a result Issue E sought to provide clarity and to address the issues of plank designated hole positioning, the requirement for linear elastic behaviour around the periphery of these holes, and the criteria for thickness measurement where no skid is present on the central floor designated hole periphery.

Also noted was that part of the measures implemented by TD039 will involve change to the Technical Regulations (TR) Article 3.15.8.a Central Floor Flexibility.

Acknowledged was that the phenomenon of porpoising, combined with low ride heights and minimal rake has been a noted characteristic of the new generation of F1 cars and that it had become increasingly apparent that excessive bouncing and/or bottoming was leading to driver pain, headaches, and loss of concentration, and that it had the potential to cause high speed accidents.

Further, the TD concluded that car excessive bouncing and/or bottoming may deem a team’s car to be of a dangerous construction, and that under TR Article 1.3, and Article 10.2 of the Sporting Code the Stewards may disqualify any such vehicle.

Whilst it was noted that it was the team’s responsibility to ensure that their cars were always safe the TD laid out its intention to introduce a stricter application of TR Articles 3.15.8.a, 3.15.6, 3.15.2, and 3.5.9.e relating to forward and central floor flexibility, and skid and plank deflection and wear measurement. Porpoising was easily deemed to be unsafe with long-term potential negative effects for F1 drivers’ health.

Plank and Skid Stiffness and Wear

porpoising Does the wood plank still exist in 2022? : r/formula1

So that the Aerodynamic Oscillation Metric (AOM) that will be discussed further on could be seen to be fair and equitable to all cars it was deemed that it was important that the floor stiffness at the three positions described in TR 3.15.8.a be equivalent between on all cars, and that significant deformations over and above 2mm would be considered as contrived to achieve significantly lower ride height, and consequently an indirect aerodynamic gain.

Insofar as the regions used to verify thickness of the plank and skids it was considered that these would be where the vertical stiffness was to be highest, that the test load for this was to be nominally linear elastic, and that the stiffness above that load described in TR 3.15.8.a will be a minimum of 15kN/mm, and therefore nominally solid.

Additionally, the FIA discussed that there was the intention to propose to the World Motorsport Council change to the same TR article 3.15.8.a to achieve the objectives of introducing further load and deflection tests to the plank.

Greater detail was provided in defining the acceptable limits of minimum thickness for the plank as per TR 3.5.9.e in the precisely placed holes defined by RV-PLANK, the plank reference volume defined in TR Article 39.

Aerodynamic Oscillation Metric

FIA standing firm on porpoising and flexi-floors action at Spa : PlanetF1

Surprisingly enough the metric defined by TD039 isn’t overly complicated and it a fairly simple summation function of the vertical acceleration signal collected from the external accelerometer defined in TR 8.10.2 which lies close to the cars centre of gravity, the circuit centreline length, and the signal sample time, and it is dimensionally expressed as millijoules per kilogram per 100 kilometres (mJ/kg/100km).

The limiting vale of the metric was defined as 100mJ/kg/100km, and it was stated that this value was to be revised over time as more data was collected and the sample set had increased.

The absolute value of the accelerometer signal was to be clipped to 7g to mitigate the contribution of extreme acceleration peaks that are typically associated with isolated road surface anomalies such, as bumps and surface transitions.

Excluded from the calculation of the metric were the first two laps after the start or restart of a race (or sprint), in/out laps, time spent behind the Safety Car or Virtual Safety Car, and any laps on wet or intermediate tyres.

Exceeding the Metric and it’s evolution

TD039 was quite clear in that any car which collected a mean metric that exceeded the limit was to be reported to the Stewards with the recommendation that they be excluded from the resulting classification, however for 2022 up to two instances per driver where the collected metric mean had exceeded the limit by no more than 20% was to be accepted without reporting to the Stewards.

The FIA conceded that the metric primarily addressed the issue of bottoming or ground strike, and not the issue of aerodynamic oscillations, and that more analysis would be needed over time to capture additional terms to address these oscillations so long as they are proven to cause driver discomfort.

Nevertheless, the FIA also iterated that they expected driving F1 cars to be a physical exercise and that their aim was not to be providing a “smooth ride”.