O.S. GT15HZ: New Gas Engine

O.S. GT15HZ: New Gas Engine

Many years ago we tried using Zenoah gas engines in our helicopters, but there were several problems we could not overcome. First, they were not designed to be used in helicopters. Rather, they were designed for some type of commercial operation, such as powering a small blower. This meant they were unbalanced, so they had to sent away for balancing before we could even think of giving them a try. And, since they were designed for blowers, they could not be mounted in a standard helicopter, so designs had to be developed to specifically handle their size and mounting limitations. And, even if all these complications were addressed, then they failed to produce the needed power for anything but hovering and gentle forward flight.

Now the popular manufacturer for OS engines has decided to tackle all these problems, and to give us a gas engine that is specifically designed for our use. The OS GT15HZ gas engine was developed to be ideal for sport, 3D and scale pilots, and it fits most 90 size helis with minor modifications. It also uses the reliable and easy to adjust  O.S. Walbro pumper carburetor for consistent performance regardless of attitude, altitude, or fuel level, while the IG-05 ignition module is designed specifically for helis and is compatible with a wide range of battery chemistries including NiCd NiMH, LiPo and Life packs.

OS does offer the E-4051 standard muffer for use with the GT15HZ, but the polished aluminum PowerBoost pipe has been expressly designed for this engine, and can extract the full performance of the GT15HZ while producing stable and reliable gas engine operation.

Here are some of the engines statistics:

Displacement: 0.912 cu in (14.95cc) – Bore: 1.091″ (27.7mm) – Stroke: 0.976″ (24.8mm) – Practical RPM: 2,000 – 16,000 – Output: 2.76hp @ 14,000 RPM – Weight: Engine, 26.4oz (748g) IG-05 Ignition Module, 3.2oz (92g) with Power Boost Pipe and  7oz (198g) with E-4051 Muffler5oz (144g) – Gasoline/Oil Mix: 25:1

I’ll be converting one of my 90 size helicopters to take the GT15HZ, and will report back on its performance and flight characteristics. And, if you beat me too it, let me know how your works in your helicopter, and your detailed impressions.

Updated: July 21, 2015 — 9:18 AM


  1. Hi Paul, I know a few guys from my club who have change from Zenoah, they two had issues.

  2. I’s sorry I didn’t see your comment until now. You mentioned two issues. What are they and how were they handled?

  3. I think Anthony meant they had issues with the Zenoah. But maybe not. Can’t imagine OS would put something out without thinking it through. Looking forward to your review.

  4. The Century Zenoah Engines G23 and G26 are pretty good with the electronic ignition. I have the Radikal G30 with a G26 it flies so solid. The engine feels dependable if you get them set up correctly and put a temperature gauge on it so you don’t over heat it. There’s some video of someone doing 3D with a Radikal G30 also.
    I do However like the OS 15HZ but the heat was ripping them apart in the past – will try the new version GT15HZ II WITH POWERBOOST PIPE 15 HZ

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