The basic idea of all the events is that a number of models (up to three) fly together, aiming to complete a given number of laps before any of the others. The model is also required to make multiple pit stops during the race, where it is refueled, the engine restarted, and the model re-launched. This is the job of the pit crew. There are rules describing how the pilots must walk around each other, and how to pass (harder than one might think, as each model is on the end of a pair of control lines and travelling as fast as 140 mph). Pit stops require that the model be refueled and restarted - which can be a problem with a very hot racing engines. The best FAI Team Race pit stops take around 2–3 seconds for the pilot to cut the motor and land, allowing the pit-man to catch the model which only moments ago was flying at , fill the tank with 7cc of model fuel from a pressurized tank, adjust the engine mixture and compression if needed, restart, and relaunch the model. Combat is an event where to two pilots "dogfight" for cuts on their opponent's streamer. Models are fast and highly maneuverable flying-wings, which chase each other around the sky at speeds in excess of . Despite deliberate mid-airs being banned, the carnage rate is high, and pilots commonly bring 10 or more models to a competition. Combat is a highly tactical event, requiring great teamwork between a pilot and his two mechanics. F2D combat - the international class for combat - is most popular in Russia and Europe, where some countries have professional or semi-professional teams. Russia and the former Soviet countries are currently the main producers of world-class equipment for this sport, including engines. Their combination of the latest engineering and design, with exotic metallurgy and experience, results in combat engines which reliably turn 32,000 rpm, and can be restarted easily in the event of a crash. Requiring lightning-fast reflexes, combat has frequently been used as a training-ground and/or hobby for many commercial and military pilots (citation needed). Navy carrier is an event where semi-scale models of real naval aircraft are flown. The event replicates the requirements of full-scale carrier aircraft, which need high speed for combat performance, and low speeds and toughness for safe carrier landings. Takeoff and landing are from a simulated aircraft carrier deck, with arrestor wires. The aim of the flight is to complete a number of fast laps, flown as quickly as possible, followed by a number of slow laps, flown as slowly as possible.