We took a look at spec racing twice in 2019 when spec FPV drone racing was only seen on the Drone Racing League and at very few events. At the beginning of 2024, there are four recognized spec classes with more being developed at different size classes. MultiGP officially hosts championship events for Freedom Spec and Street League. MultiGP chapters locally host events for Tiny Trainer and the Underground Whoop League. In this article, we will talk about those four classes and include links to videos from those races!
Open VS Spec Racing
Open class races let pilots compete with (almost) any drone they bring. Pilots have the ability to perfect their FPV drone so it meets their style of racing perfectly. While there are some “unbeatable” motor-prop-battery selections, there is room for development and innovation. Most of the drone races you attend will be open class.
Spec racing requires pilots to meet a certain set of requirements to be allowed to compete in an event. The race director(s) strictly enforce these requirements to prevent anyone from getting an unfair advantage. Racing is a test of pilot ability, since there is much less variation between aircraft. The fastest pilots usually have the fastest racing lines that they consistently follow. Spec races also tend to be easier to watch (because of LEDs) for spectators.
Underground Whoop League
This is a relatively new spec that is being developed that uses 75mm frames. When HDZero made the Whoop VTX, pilots started converting their builds to HD video systems. While their video got sharper, the added weight took them out of the running for a podium position. This spec lets pilots use heavier video systems and levels the playing field with a custom firmware.
My whoop here is almost spec legal, it needs a larger frame and some LEDs. The firmware was a breeze to install! To help get to weight, I may upgrade to the HDZero Nano90 for even less video latency!
The minimum requirements for this spec are
- You must use motors from the approved list
- You must use RPM limiter firmware
- You must use Gemfan 1610 biblade props
- You must use a 75mm frame from the approved list
- You must have LEDs on your drone
- You must use a 1s 450mAh battery (max charge 4.35v)
- You must use an “X” configuration
- The weight (including battery) must be between 40 and 45g
The official website has the motor list, frame list, instructions for firmware installation, and instructions for LEDs. To find events in this class you can go to the official discord server to get build tips, and notifications about upcoming races
Tiny Trainer
When Even “HeadsUp” Turner joined the Drone Racing League he was looking for a smaller version of the Racer 4 that would let him practice in the comfort of his backyard. Enter the FlyFive33 Tiny Trainer, which is a powerful 3” racing drone. It is modeled to fly like the DRL Racer 4, and look just as cool! Races in this spec can be held both indoors and outdoors.
The minimum requirements for this spec are:
- You must use the official Tiny Trainer V1/V2 frame (no modifying the arms)
- You must use the Tiny Turner 1404 4533kv motors
- You must use HQ HeadsUp Tiny props
- You must use a 3s battery (max charge 4.35 volts per cell)
- Maximum weight of the battery is 50g
- The FPV drone must weigh at least 160g
- You must have at least eight addressable LEDs onboard
One of the biggest events in this class is the annual MultiGP Ice Storm race in Milwaukee. Pilots compete for one of the largest prize purses in MultiGP. If building a drone this small is intimidating, Five33 offers prebuilt bind-and-fly options for purchase on their website.
My Tiny Trainer is “well loved” and has gone relatively unchanged since I built it about two years ago. Despite all the times I have crashed, the frame and motors are still intact! For pilots who build a V2 Tiny Trainer you get the benefit of replaceable arms, compared to the uni-body V1 frame. To increase durability I printed some arm guards that Haku3d designed. The guards help keep the ends of the arm from delaminating in collisions with the ground
Freedom Spec
Freedom spec was pioneered by Evan “HeadsUp” Turner and Shawn “shames” Ames, and has gone through some small changes since its inception. This spec gives racers the most freedom with their parts selection and has a huge perk… ALMOST EVERY OPEN CLASS FPV DRONE IS FREEDOM SPEC LEGAL!!! In fact, the winner of the 2020 MultiGP Championship only needed to change his battery to pass the spec check.
The minimum requirements for this spec are:
- 533g Minimum weight (with battery)
- You must use the RPM Limiter Betaflight firmware
- You must use Five22 Headsup 2207 1960kv motors
- This may change due to advances in the Betaflight RPM limiter
- You must use HQ R38 Headsup props
- You must have 3 or more LEDs
- You must use a 6s battery
- You must use a BLHeli32 or AM32 ESC
Pilots can expect tight races, with a focus on consistency between heats. Even though everyone is on 6s, the RPM limiter keeps competition fair. My favorite part about this spec is the ability to use my open class racers to compete – all I have to do is turn the RPM limiter off in betaflight. The official website has the full rules, and you can find races on the MultiGP website.
My Five33 Midmount frame here, almost meets the spec requirements. I use the Champion Edition motors which are higher KV than what is allowed. But I have heard rumors that Champions Edition motors will be added to the rules this season… we will see!
Fortunately I use MR30 connectors, so all I have to do is unplug the non-spec motors, plug in the right ones, and swap props! The RPM limit can be enabled in the OSD menu, and I am already at the required weight.
Street League
This spec was based on the DRL Racer 4 that you may have seen on TV. The FPV drones are heavier, slower, and have LEDs all over them to be easily seen by other racers and spectators. Due to the large size, races at this spec only happen between spring and fall.
One of the coolest parts of Street league is a new feature called boost mode! When activated, pilots get a temporary boost in the maximum RPM so that their drone goes faster. It is just like using a mushroom in Mario Kart. Pilots can choose when to use this mode, and may even try to get a last second burst of speed right at the finish line!
The minimum requirements for this spec are:
- The FPV drone must weigh at least 1280g (including battery)
- You must use either Gemfan 7043 or HQ 7x4x3 props
- You must use a 5s 2200mAh battery (max charge 4.25 volts per cell)
- You must use an open source frame
- You must have LEDs from multiple angles
- You must use a motor from the approved list
- You must use the custom firmware
The race directors regularly conduct spec-checks between heats, so any attempt to skirt a rule will be caught! You can still compete in the event, but your heat time will be disqualified… and you get a unique role on the official Discord server! Here is a link to the official rule book, with the firmware you need to be Street Legal – https://streetleague.io/spec/
My Street League FPV drone is a Project399 Practice Rig. I built it back in 2019 and have not broken a single arm! When it comes to durability, this frame is in a class of its own. I even heard that someone was using it to chase drift cars, and wound up getting run over. The frame was unharmed, and only needed new props to get flying again!
Not only is it spec compliant, when I use standard Betaflight without the RPM limiter, this is an absolute monster on the track. Its heavier weight and slower acceleration forces me to learn efficient (momentum conserving) lines on the track.
One of the most popular frames is the SpeedSourceFPV Super 70. This frame has been on the podium at almost all of the big Street League races last season. The frame’s creator also partnered with former DRL Pilot, MannyHimself, to develop motors tailored for spec racing. I really like how this frame protects the battery with the upper aero canopy, and keeps the flight stack protected by the steel mid plates.
The Future
I keep talking about the RPM Limiter in Betaflight, which actively monitors the RPM of motors and dynamically limits their speed. This allows anyone to play with max speeds and develop their own spec. Pilots near you may come to agree on a set of rules that level the playing field. One of my favorite examples of this is where the pilots change their RPM limit by X% based on their finishing order. The first place pilot will have more of a limit than the last place pilot, when the finishing order changes, the limits change too!