os.91fx ringed on a YAK 54 (63" span) wanting to learn hover / torque roll, which props are recommended. i have 14x4 / 14x6 / 15x6 / 16x6. appreciate advise...thx

16x6 is too much, usually used for a 120 2C or the YS110, a 14x4 is good for a 72/82 4C, 14x6 for a 82 4C or 61 2C. A 15x6 is nice to start with for sport flying. If you are looking at 3Ding then try a 15x4W or even a 16x4W.

APC 15x4w is what you need to start with, then experiment from there.

-Deleted-

My testing has shown the best prop on a .91FX for ultimate thrust is APC 15x6 (should turn around 10,500, if I remember right, and pull about 12 pounds). A little less thrust but instant spool is SK wood 15x6-my choice for 3D on a 8+ pound plane. It sounds like you have plenty of motor for the plane and don’t need the best thrust? If you are around 7 pounds RTF and have a good running 91FX, anything from a 13x6 to 15x6 will work. I have not found a thrust benefit to 4 pitch props 16 inches or larger. I did have a 16x5 wood that worked well a SA100 and FL330.

Tianci is right; load the .91FX with anything more than a 15x6 and it falls on its face.

Please delete