SMI Air Force One Supplemental Braking System

The SMI Air Force One remains a solid choice for RVers who flat tow and want a portable, non-invasive supplemental braking solution.

4.2

HitchHaven score4.2 out of 5 · our editorial rating

Proportional braking technology that mimics motorhome brake pressure
Portable design requires no permanent modifications to towed vehicle
Breakaway switch included for safety compliance in all 50 states
Works with vehicles equipped with power brakes
Quick-connect air hose and coiled breakaway cable
Compatible with vehicles having at least 8 inches of brake pedal travel

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Overview Specs Pros & cons Full review Related

The verdict

The SMI Air Force One remains a solid choice for RVers who flat tow and want a portable, non-invasive supplemental braking solution. Its proportional braking system offers smoother stops than many fixed-ratio alternatives, and the lack of permanent modification appeals to those who swap towed vehicles or want to preserve resale value. While setup takes some practice and the pump noise bothers a few users, the overall safety and compliance benefits make it a worthwhile investment for frequent towers.

Spec plate

Braking Type: Proportional vacuum-assisted
Installation: Portable, non-permanent
Compatibility: Vehicles with 8+ inches brake pedal travel
Breakaway System: Included, battery-powered
Monitor Display: In-cab LED indicator light

Pros & cons

What we like

Truly proportional braking reduces jerking and improves towed vehicle control
No drilling or permanent installation required on the toad vehicle
Easy to transfer between different towed vehicles
Meets braking laws in all states requiring supplemental brakes
Reasonably priced compared to in-vehicle hydraulic systems
Setup and breakdown is quick once you learn the routine

What to watch

Initial setup and learning curve can be confusing for first-time users
Vacuum pump can be noisy during operation
Not compatible with vehicles lacking sufficient brake pedal travel
Requires manual hookup and removal every time you tow
Monitor box wiring can be tricky to route into some dashboards
Occasional false breakaway triggers reported by some users

Full review

The SMI Air Force One supplemental braking system is a trusted solution for RV owners who tow a dinghy vehicle behind their motorhome and need a reliable, DOT and RVIA compliant way to activate the towed vehicle's brakes in sync with the motorhome. Designed and manufactured by Stay-In-Play / SMI, this proportional braking system monitors the motorhome's deceleration and air pressure changes, then applies corresponding braking force to the towed car, truck, or SUV through a direct connection to the vehicle's existing brake pedal and power booster. Because it ties into the air brake system commonly found on diesel pusher motorhomes and larger Class A coaches, it is specifically engineered for towing setups where traditional proportional or inertia based brake controllers are not compatible, filling a critical niche for owners of air brake equipped motorhomes.

What sets the Air Force One apart is its ability to deliver true proportional braking rather than a simple on off response, meaning the towed vehicle brakes with an intensity that mirrors the motorhome's own braking effort. This results in smoother, safer stops, reduced wear on the motorhome's brakes, and less strain on the tow bar and hitch components since the dinghy is actively helping to slow the combined rig rather than simply being dragged along. The system is designed for permanent installation in the towed vehicle, with minimal visible hardware and no bulky proportional pump or reservoir units sitting on the floorboard, which keeps the interior of the towed car clean and functional for everyday driving when it's not being towed.

For RV and camper accessory shoppers, the SMI Air Force One is particularly valued for its straightforward breakaway system integration, its compatibility with a wide range of popular dinghy towing vehicles, and its reputation for durability over years of highway towing. It includes the core components needed for installation, such as the actuator bracket, monitor, and wiring harness, and is typically installed by a qualified RV technician familiar with air brake interfacing. Because it was purpose built for motorhomes running air brakes rather than hydraulic systems, it remains a go to supplemental braking choice for full time RVers and serious weekend travelers who tow their vehicle frequently and want a dependable, low maintenance braking link between coach and dinghy.

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