[dan1000]

I love my 1974 T337G (pressurized), and am looking for ways to improve the climb segment of my flights. If any of you are flying on higher horsepower than my Riley-intercooled TSIO-360's (225hp, I believe), I'd love to learn about your experiences in upgrading or operating. The search button has reported that some people are operating TSIO-520-NB's, though there are questions about handing their extra weight.

Why am I interested in climbing faster? The aircraft is fast enough in cruise, but a typical MGTOW climb from sea level to 13,500 ft is about 25 minutes, and to 17,500 feet would increase that to about 33 minutes. This all happens at 120kts in an attempt to hold CHT under 400 degrees. However, it's often ISA+20 here in SoCal, so I'm frequently pouring several GPH of unburned fuel out the exhaust to keep below 400. So that's an *average* climb rate of around 550fpm or a little less if going up to the flight levels.

Doubling that to an average of 1000fpm, while increasing the IAS from 120 to 150kts would cut time-to-climb by 5 - 7 minutes per flight, and would also leave more of the flight occurring at cruise speed rather than climb speed. On a 2 hour flight, this might cut time aloft by 12 minutes, increasing block speed by 10% overall.

Best of all, it seems that safety margins improve with an increase in HP in a number of ways: Reduced take-off runs, massively improved initial climb (therefore much less time spent below the altitude needed to safely maneuver for a landing in event of an emergency after take-off), massively improved single-engine climb performance at all altitudes, and (if cruise speeds are kept the same) much lower percentage output of the engines throughout most of their lives (longevity). And if one does open up those throttles in cruise, perhaps a further 10% reduction in block time might become available, though at a cost of fuel consumption. Still, turning a 2 hour flight into a 1h36 flight can be attractive sometimes.

So: Do any of you have experience with higher HP engines? We've all "read about" and "heard about" such things, but I'd love to hear from someone who is flying a higher-HP Skymaster, to learn how it worked out.

The things that seem most important to me are:

- Is anyone here actually flying Skymasters with engines upgraded from TSIO-360 to something else? Or could perhaps introduce me to someone who is doing so?

- Bigger engines are heavier, and (if pushed) need more fuel. How is the reduction in useful load handled?

- Is anyone actually flying with a MGTOW greater than 4,700 lbs? I'd love to learn how that was accomplished, and how it has worked out. Or are all the wingtips and extensions one reads about basically just a "good idea" that never really came to fruition?

- How has the increased HP helped / hurt the aircraft's usefulness?

- Are there other ways to improve the climb performance (other than by offloading fuel or people)?

I love my P337, and whenever I think about upgrading to a 340A, 414A, or 421C, I remember that the reason I chose a Skymaster is that it's docile, forgiving, safe. I know I can increase performance by changing to a different model. But then I'm into much more recurrent training. Plus, the 400 series isn't going to qualify for BasicMed, which is an issue for me (the 340A would).

Thanks

Dan