Why did Russell activate his DRS in a non-designated zone at the Bahrain Grand Prix?

After George Russell salvaged a second-place finish despite suffering a brake-by-wire failure at last Sunday's Bahrain Grand Prix, Mercedes has begun its investigation of the failures.

George Russell qualified second, but started from third place at the Bahrain Grand Prix after receiving a grid drop penalty for a sporting infringement from his team.

The British driver made up a place at the start, and managed to hold on to this position until the chequered flag fell in Sakhir. However, he was under investigation after a possible DRS infringement during the latter stages of the race in Bahrain.

The Mercedes driver was managing a number of bizarre electrical gremlins from the middle part of the race. It emerged during the 57-lap race that he once pressed the team radio button which also opened the DRS on his Mercedes F1 car.

This took place outside the designated DRS zone and thus would normally contravene the rules. The incident was investigated, and the stewards elected not to penalize Russell which meant that he could keep his second-place finish at the Bahrain International Circuit.

Reflecting on the issues, Mercedes press chief Bradley Lord said: “Probably from the TV broadcast it sounded like [the fault began in] the final 10 laps. Actually, it was from about half-distance that we had the first sign of a problem.”

“We’ve just arrived back in the factory with about 10 different suitcases of parts and items that we’re bringing back including a pretty frazzled and sort of charred-looking FOM timing transponder and then some other bits of kit as well related to the brake-by-wire system. So we haven’t got root causes yet.”

The issue became apparent when Russell's name plummeted down the order after the safety car interruption.

“George’s name just plummeted down the time sheets and we were thinking okay, no, he’s still on track, he’s still talking on the radio so there’s a timing issue here rather than something else.

“That also had as a knock-on effect as, if you lose the timing transponder, you lose the part of the car that interacts with the mechanism so for activating DRS, for knowing whether you’re within a second or another car it’s within a second of you. We therefore had to resort to a back-up system. We talked to the FIA, we get permission to do that, and then George was effectively operating the DRS in manual mode.”

Another problem developed on Russell’s car around the same time. Lord continued: “We started to have a separate but parallel problem with the brake-by-wire. That’s the electronics that determine the braking force between front and the rear brakes, but particularly on the rear brakes.

"There’s a chunk of braking that is done by the MGU-K – the electric motor on the engine – and then a chunk done by the hydraulic braking system.

“When we go into what we call passive mode you’re just relying on those hydraulic brakes. But it changes the car’s behaviour under braking and ultimately it’s very, very difficult to run the car like that because you’re losing a lot of braking force and you ultimately overheat those much smaller hydraulic rear brakes.

“So George was battling with that. We had to do what’s called a default change for him so that he could toggle in and out of that brake-by-wire when it went to passive and put it back in the active mode in those last 10 laps. I think over those last 10 laps he was making between 20 and 30 changes to that setting as he was also driving, hitting his braking points and keeping first Leclerc and then ultimately Lando behind him as well.”

“We didn’t know what further knock-on effects it might have. The big fear was that it would knock out the dashboard completely so the whole steering wheel display.

Mercedes feared that the dashboard will completely misfunction in the dying stages of the race, but the team was ready to use back-up systems that would have enabled Russell to continue to drive.

“If that happens, we can continue driving because there are failsafe and back-up systems in the car that mean we can still change gear, we can still use the DRS and we can still use the radio. We have a back-up radio system in the car that isn’t located on the steering wheel. It’s a button down in the cockpit. That button, as it turns out, is also the manual backup for the DRS if that fails.

Russell had been investigated after the race for using his drag reduction system in a zone where it is not permitted. The Briton ultimately escaped any sanction for the 'illegal' use of DRS as he closed the system immediately after the activation and he also lifted after that in order to lose at least the amount of time he had gained with the DRS.

“So George was cycling through a practice to go to the back-up radio just in case it was needed, pressed that back-up radio button and inadvertently on the back straight also opened the DRS, because it does the two things at the same time. He realised it within an instant, braked, closed the DRS and continued. That’s when we heard him come on the radio.

“That was what the stewards looked at and investigated and ultimately decided there was no further action for it after the race. It’s what made his drive ultimately so impressive not just to have the mental bandwidth to cope with that but also to be doing the driving, making no mistakes, fending off Lando, keeping Leclerc out of striking distance as well. It was a really incredible performance.”