iFlight AOS 3.5 EVO O3 4S HD

BNF Copters

Brand

Version	4S
Frame Design	X-Frame
Size	3.5"
Style	Cinewhoop
VTX	DJI O3 Air Unit
Weight	320g

The iFlight AOS 3.5 EVO is a high-performance 3.5-inch freestyle drone that utilizes Chris Rosser’s famous vibration-damping frame design. Equipped with the DJI O3 Air Unit and XING 1504 motors, it delivers a power-to-weight ratio that rivals full-sized 5-inch quads. It’s engineered to be extremely responsive and smooth, offering 4K/60fps recording in a platform that stays under the 250g limit with a 4S 850mAh battery.

Prices & Deals

Last Updated: 06.08.2025

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Product Description

The iFlight AOS 3.5 EVO O3 4S HD is a masterpiece of resonance-engineering, designed specifically to bring 5-inch freestyle performance to a sub-250g package. Using topology-optimized frame technology, it eliminates the vibrations that typically plague small quads, resulting in some of the cleanest digital footage possible without needing a separate action camera.

Topology Optimized Frame: The AOS 3.5 EVO frame is designed using computer simulation to ensure that resonance frequencies are kept away from the flight controller's operation. This results in an incredibly "quiet" electrical environment, allowing for higher PID gains and less filtering.
O3 Vibration Isolation: Features a dedicated camera cage that protects the DJI O3 lens while providing mechanical isolation. This ensures that the RockSteady and GyroFlow stabilization work without the "jello" effect.
XING 1504 Performance: The 3100KV motors are specifically sized for 3.5-inch props on 4S. They offer more torque and authority than typical 1404 motors, making the drone feel "locked-in" during aggressive maneuvers.
Sub-250g Versatility: This drone is designed to be fully legal in many regions without registration. Even with the heavy O3 Air Unit, it stays under 250g All-Up Weight (AUW) when paired with a 550mAh to 850mAh 4S LiPo.
H-Frame View: The frame geometry ensures a 155° wide-angle view with no propellers in the frame, providing a truly immersive cinematic experience.

Technical Specifications:

Wheelbase: 162mm
Weight: ~197g (without battery) / ~280g (with 850mAh 4S)
FC & ESC: BLITZ F7 AIO (or BLITZ Whoop F7 AIO)
Motors: XING 1504 3100KV
Propellers: HQ D-T90MM (3.5 inch)
Video System: DJI O3 Air Unit
Max Speed: 110 km/h
Max Hover Time: ~12 mins (No load, 850mAh)

Pilot's Reality Check:

Durability Trade-off: To stay under 250g while using the heavy O3 unit, the frame uses thinner carbon in some areas compared to a 5-inch tank. While the 4mm arms are tough, it won't survive a full-speed concrete impact as well as a dedicated 5-inch basher.
Battery Selection: To stay strictly under the 250g legal limit, you must use a 4S 550mAh to 650mAh battery. Using an 850mAh or 1050mAh will push you over the 250g mark, which may require registration depending on your local laws.

Flyer's POV: Flying the AOS 3.5 EVO is a "purity" experience. It has a unique "snap" to its movements that you just don't get with 5-inch quads. Because it's so quiet and vibration-free, it feels like it's sliding on ice. You can throw it into tight gaps and perform complex freestyle tricks with total precision. The lack of prop-in-view combined with the 4K O3 footage makes you feel like you're flying a professional cinema rig that fits in the palm of your hand.

📦 Package contains

1 * AOS 3.5 EVO 4S HD BNF (Pre-built & Tuned)
2 * HQ D-T90MM 3.5" Propellers (Pairs)
2 * Battery Anti-slip Pads
2 * Battery Straps
1 * Screw Bag (Spare hardware)

🤔 Frequently Asked Questions

Is it really under 250 grams?
Yes, but it is tight. To stay under the 250g legal limit, you generally need to use a 4S 650mAh to 750mAh LiPo. If you step up to an 850mAh or 1050mAh battery for longer flight times, the total takeoff weight (AUW) will typically land between 270g and 320g.
What makes the EVO different from the previous version?
The "EVO" update specifically redesigned the camera cage and frame to be compatible with the DJI O3 Air Unit. It includes reinforced camera plates that protect the lens while ensuring no propellers are visible in your 4K footage, even at the O3’s widest 155° FOV.
Does it handle like a 5-inch drone?
Surprisingly, yes. The AOS 3.5 was designed based on "disc loading" physics to mimic the feel of a full-sized 5-inch freestyle quad. It has more "inertia" and "pop" than a standard 3-inch drone, making it capable of technical freestyle tricks that smaller whoops can't pull off.
Why are the arms shaped like triangles?
This is the AOS Truss Design. Unlike flat carbon fiber plates that can vibrate like a tuning fork, the truss structure is incredibly stiff. This allows you to run higher PID gains and lower filtering in Betaflight, resulting in a much more connected and responsive flight feel.
4S vs. 6S version?
The 4S version (using 3100KV motors) is the most common for the 3.5-inch size as it balances weight and power perfectly for sub-250g goals. A 6S version exists for those who want maximum "punch," but it requires smaller, higher-voltage batteries that are sometimes harder to find in this weight class.