Climb Monster Ch 2


Active Member
Oct 25, 2020
Columbia SC
YG4 Air Command Tandem
Total Flight Time
800 hrs
2023 marks the eleventh year now since I built and have been running a 145HP Yamaha Genesis 4-stroke (YG4) on Ora Cook's original 1995 Air Command tandem.
It took a while for this old fart (69) to get comfortable climbing with that much power, even with a mild 2.58:1 PSRU, as I started flying at a late age ~2006 and was well past my prime and any need for thrills beyond just plain, old, flying gyros.

Switching to 2.72:1 (proto Hy-Vo PSRU) added a new dimension but before I really got into climbing with that I rolled the bitch over on the beach taking off from a tidal island, got pretty fed up with you-know-what and she sat in a hangar from 2016-19 before taking a deep breath, ignoring the trolls, and getting back in the air again. Since then I've been running a 2.72:1 Arrow PSRU with 68" 3-blade Warp Drive at 8.5° tip pitch allowed 9200 ERPM/ 2842 PRPM.

Conventional wisdom puts it that a 68" prop should turn 2850 PRPM for maximum efficiency. But what the heck, at just 77% Mach howzabout let's just u-n-me de-pitch the prop about 7/10ths degree and see what happens to a climb already well-documented to be a good, solid 1500 FPM sustained for at least 700' at 1800' MSL adjusted at 90°F, OK?

Yesterday CUB AWAS reported 1800' AMSL, 31°C so I climbed in, took a warm up lap, did a T&G and took the Garmin Etrex home to DL the data.

Now I'd already exercised the Gunslinger with the new pitch settings a tick over 7.5° last week, and it FELT like I was climbing steeper yet the GPS results were really no better than realized @ 8.5° tip, while losing 5 mph at normal cruise ERPM 7500-8000. Disappointing.

But yesterday's results were better, encouraging a further pitch reduction to increase HP to the week perhaps? Compare previous prop speed WKSHT next, to the latest, with climb results, following.

Prop Speed WKSHT 2.png
Here is yesterday's WKSHT with 7.7° prop tip pitch and the resultant data:
Prop Speed WKSHT 3.png
And here is the accompanying GPS climb data:
Gunslinger Climb WKSHT 230724.png

This is the previous report from Bensen Days 2023, for comparison:
Gunslinger Climb Wksht 230325 Bensen Days A.png

I don't think I took a breath during yesterday's climb...until I rolled out at the top. IAS never went below 50-55 MPH, after I get accustomed to the new settings will be climb steeper...I'll run some more tests and see what the right IAS is for optimal climb performance, but everyone has always told me to shoot for 45 MPH.

So...does this qualify as a flying adventure? My knuckles were white for about 20-30 seconds...but, then, ah'm jest a late-start pilot lookin' down t'uther sahd o' mah hill of life, Suzie.

There's a 165HP YG4 settin' in the hangar with a CLT Air Command tandem begging attention which don't weigh no mo than this 570# climb monster.

And the one flying now could stand to lose 18# of SS Yamaha stock sled muffler weight to become even lighter...but it looks and sounds so good ah hates ta make that change.

Final note: Yesterday's work was recorded with 1 hour of fuel aboard, so there's another 20# to lose w/o so much as pulling a wrench outta the the travel bag, the extra oil bottle for 200 mile CROSS COUNTRY trips (yes, YG4s DO travel cross country, and they HAVE BEEN since 2013...), hell I could even leave the radio on the ground LOL.

I carry a portable Garmin Etrex for recording this data, it velcro-straps to my thigh. Anyone and everyone is welcome to borrow it whenever you see me at a fly in or at my airport CUB to determine their own climb info.

Happy flying, ya'll!