Coaxial Helicopters

Videos Below:

Vehi-Cross

Falcon 8913

7708-Flier 7

UDI-805

UDI-802

SH-6025

Syma s107

MJX T34

MJX F39

MJX F27

MJX T38

These coaxial helicopters have counter-rotating blades which provides very stable hover and easy, predictable flight. The 3ch models have limited movement authority due to the horizontal tail motor lifting or dropping the tail for movement. 4ch models are somewhat better due to swashplate which tilts the bottom rotor in the direction of flight. With few exceptions, none handle much, if any, wind and are good only for orientation training or very relaxing flight. These are in order of my owning them. I no longer have any of these coaxial helicopters.

Solo 210a

The Syma s107 is the 3ch coaxial helicopter that many people start out with. Inexpensive, mostly good quality, extremely stable and easy to fly, it provides a great introduction to rc helis. Parts are readily available also, which gives you a chance to try basic repairs.

The s107 is tame but rock solid. Watch out for low quality copies.

The UDI-802 3ch is similar to the s107 in design and flight characteristics but with a different style canopy. Build quality is average. The first one I received was doa, the second one worked well. I went on a campaign to collect yellow helicopters and this one flys very well. Parts are available but less common.

The San Huan SH-6025 is a tiny coaxial with somewhat twitchy controls. Parts are available but more difficult to find. Once you get the hang of this one it buzzes around quite nicely. The head and blade grips break easily.

The UDI-805 3ch is a design variation of the UDI-805 and shares decent build quality and tame, predictable flight characteristics. I bought it because it is yellow. I think it looks the best in this class.

The 7708-Flier 7 is an unusual design and is actually a pseudo 4ch. Motors on the wings provide aileron-type tilt to move sideways. There is a front spotlight and running lights on the wings. A turbo button provides a surprising burst of speed. Parts are not directly available which teaches you be resourceful to modify other parts when needed. This was a favourite except for one issue - incorrect wiring caused the sideways movement in the opposite direction to stick inputs.

The 8913 was my first real 4ch heli, with a swashplate and links to tilt the lower rotor blades in the desired direction of travel. Unfortunatley build quality was very poor, transmitter controls had to be rewired to work in the proper direction, and the motor power was much too high to provide secure control. The parts were used to build higher performing hybrids from several models. This was good fun and good practice but is not recommended.

This is supposed to beable to drive along the ground and fly through the air, but it does neither very well. The two wing fans provide movement and turn on or off as needed to turn. Handling is flakey, no stabilizing gyro is present, and build quality very poor. Not recommended.

MJX F28

The MJX-F27 full 4ch (with swashplate attached to lower blades) was my first good quality 4ch heli. Construction is sturdy and crash resistance is excellent, parts are readily available. Flight characteristics are very stable hover and predictable controls. Even the lcd transmitter works well. It is capable of outdoor flight in a very light breeze. The only negative is the F27 is quite heavy for its size.

The 4ch MJX-F28 is a larger version of the F27. Again good build quality and predictable and easy flight controls. The transmitter added a larger lcd screen with more adjustments. Indoor flight is pretty good but outdoors the slightest breeze stops it dead. The 3.7v power system is inadequate for a heli of this size and weight.

The 3ch MJX-T38 is a very durable and powerful little heli. Due to its additional power, it is not quite as easy to fly. But the quicker handling and sturdy construction, in my opinion, make it stand out in this class.

MJX T23

The MJX-T34 was my first larger 3ch coaxial, about 21" long. It has the usual sturdy build but was a very tame flyer, which made it useless outdoors, while being too large for indoors.

The large (23") 3ch MJX-T23 was my second attempt to have a large helicopter. It had excellent build quality and also very good power. It could fly outdoors on a relatively calm day and was large enough to see at a distance. However, any wind gust would take it away or cause loss of control. It was much too large for indoor flight as it would blow everything around the room. A stable heli.

I changed the canopy and tried various blades of all sizes to improve outdoor flight. Although I had some success, it was still limited to calm days outdoors.

The 4ch F39 was very large at 24", with good build quality and decent power. Adding the 4th (aileron) channel improves its handling and outdoor capability. However, by this time it was clear to me that if I wanted to extend my outdoor flying beyond calm days, a fixed pitch single rotor would be necessary. The small Solo Pro 260a and large MJX-F45 fit the bill quite nicely. See other reviews.

At this point I already owned a Solo Pro 260a single rotor fixed pitch and added this coaxial version to my collection, along with a better transmitter (NE-24TX) that would fly both. This Nine Eagles Solo 210a is a ultra light full 4ch coaxial. Although power was very good, it was so light that it could get out of sorts quite easily. It also suffered from a flimsy flybar. So I changed out the shaft, blades and flybar from a NE Bravo III.

This is the final result along with the added yellow Nine Eagles Flash canopy. Also shown is the Solo Pro 260a fixed pitch (my first single rotor) and the NE-24TX.

The HuanQi HQ-852 is a super fun larger coaxial with lots of power and speed. It is very easiy to exceed the flight limits of a coaxial. Thankfully, parts are inexpensive and, due to its larger size, repairs are straight forward.

Specs:

Length - 395mm

Rotor - 334mm dia

Battery - 7.4v 2s 800mah

Weight - 242gr

The areas on the HQ-852 which break most frequently are the extremely brittle blades, which snap at the slightest hit, and the tall main shaft which bends at high speed impacts. If flown 'normally', only the blades are an issue. Tougher replacement blades can be found but are hit and miss for quality.

Recommended spare parts are: