Master Airscrew 9×4
9×4×2 · air · measured geometry
Chord and twist are the UIUC digitization. Camber, thickness and the two-blade count are PropShaper lofting defaults, not measurements, and this prop is not in the BEMT validation gate. The hub starts as a conventional M5 and is yours to change.
Not a validation case. Loading this blade does not mean the solver has been checked against it. Use the measured table and the model as two sources.
Open this prop in the studio →
What the wind tunnel says
These figures are computed from the UIUC file, not from PropShaper's solver. Static thrust is T = CT ρ n² D⁴ and power is P = CP ρ n³ D⁵, with ρ = 1.225 kg/m³ (ISA sea level) and n in revolutions per second. Figure of merit is CT3/2 / (√2 CP), the hovering-rotor definition. On this Volume 1 set it runs about 0.30–0.64. A helicopter near 0.75 is the wrong comparison.
- Static at 5,952 rpm: CT 0.0774, CP 0.0301, figure of merit 0.51.
- That coefficient is 260 gf and 22 W on one prop at sea level.
- Geometric pitch speed at that rpm is 36 km/h. That is where axial angle of attack would be zero. It is not a recommended cruise speed.
- Best measured efficiency is 54% at J = 0.35, 6,894 rpm (CT 0.0411, CP 0.0262). Peak efficiency is at low advance ratio, the hover and slow-flight side of this data.
Static measurement
ma_9x4_static_rd0894.txt. J = 0, so efficiency is not defined. Figure of merit is the hover number.
| rpm | CT | CP | FoM |
|---|---|---|---|
| 2985 | 0.0641 | 0.0311 | 0.37 |
| 3313 | 0.0685 | 0.0316 | 0.40 |
| 3558 | 0.0693 | 0.0309 | 0.42 |
| 3793 | 0.0710 | 0.0310 | 0.43 |
| 4072 | 0.0724 | 0.0308 | 0.45 |
| 4357 | 0.0735 | 0.0306 | 0.46 |
| 4634 | 0.0740 | 0.0304 | 0.47 |
| 4898 | 0.0752 | 0.0304 | 0.48 |
| 5134 | 0.0758 | 0.0303 | 0.49 |
| 5418 | 0.0761 | 0.0301 | 0.49 |
| 5682 | 0.0769 | 0.0301 | 0.50 |
| 5952 | 0.0774 | 0.0301 | 0.51 |
| 6228 | 0.0779 | 0.0301 | 0.51 |
| 6490 | 0.0783 | 0.0299 | 0.52 |
| 6756 | 0.0783 | 0.0298 | 0.52 |
| 7007 | 0.0788 | 0.0298 | 0.52 |
Forward flight, one run
The run whose rpm is nearest 5,952 is shown in full. ma_9x4_rd0897_6014.txt. Other runs are linked under it. Advance ratio J = V / (n D).
| J | CT | CP | η |
|---|---|---|---|
| 0.106 | 0.0711 | 0.0310 | 24% |
| 0.133 | 0.0686 | 0.0310 | 30% |
| 0.162 | 0.0655 | 0.0309 | 34% |
| 0.185 | 0.0627 | 0.0306 | 38% |
| 0.216 | 0.0586 | 0.0301 | 42% |
| 0.242 | 0.0545 | 0.0294 | 45% |
| 0.269 | 0.0506 | 0.0287 | 47% |
| 0.292 | 0.0471 | 0.0280 | 49% |
| 0.320 | 0.0421 | 0.0268 | 50% |
| 0.352 | 0.0366 | 0.0253 | 51% |
| 0.375 | 0.0324 | 0.0240 | 51% |
| 0.400 | 0.0278 | 0.0225 | 49% |
| 0.423 | 0.0232 | 0.0209 | 47% |
| 0.454 | 0.0165 | 0.0184 | 41% |
| 0.478 | 0.0117 | 0.0165 | 34% |
| 0.507 | 0.0056 | 0.0136 | 21% |
| 0.538 | -0.0013 | 0.0104 | -7% |
Other measured rpm
| rpm | best η | at J | file |
|---|---|---|---|
| 4001 | 42% | 0.327 | ma_9x4_rd0895_4001.txt |
| 5010 | 47% | 0.319 | ma_9x4_rd0896_5010.txt |
| 6014 | 51% | 0.352 | ma_9x4_rd0897_6014.txt |
| 6894 | 54% | 0.346 | ma_9x4_rd0898_6894.txt |
| 6922 | 54% | 0.391 | ma_9x4_rd0899_6922.txt |
Geometry the studio loads
r/R, chord/radius and twist from ma_9x4_geom.txt. The geometry file does not record blade count. This commercial prop is loaded as two blades, which matches the three props the solver is checked against. Camber and thickness are PropShaper lofting defaults (slow-flyer families cambered, others near 2% camber), not the manufacturer's section. The hub starts as a conventional M5. Change it to your motor.
| r/R | c/R | twist deg |
|---|---|---|
| 0.15 | 0.153 | 30.18 |
| 0.20 | 0.148 | 32.66 |
| 0.25 | 0.149 | 31.47 |
| 0.30 | 0.154 | 26.99 |
| 0.35 | 0.159 | 23.27 |
| 0.40 | 0.161 | 21.06 |
| 0.45 | 0.161 | 19.25 |
| 0.50 | 0.161 | 17.60 |
| 0.55 | 0.160 | 16.14 |
| 0.60 | 0.158 | 14.96 |
| 0.65 | 0.154 | 13.83 |
| 0.70 | 0.149 | 12.99 |
| 0.75 | 0.143 | 12.28 |
| 0.80 | 0.135 | 11.69 |
| 0.85 | 0.127 | 10.92 |
| 0.90 | 0.118 | 10.17 |
| 0.95 | 0.105 | 9.28 |
| 1.00 | 0.091 | 8.38 |
Sources
- UIUC Propeller Database, Volume 1, version 3, compiled by Gavin Ananda, 3 February 2015. Files were fetched 2026-10-09.
- Brandt, J. B., and Selig, M. S., “Propeller Performance Data at Low Reynolds Numbers,” 49th AIAA Aerospace Sciences Meeting, AIAA Paper 2011-1255, January 2011. PDF.
- Brandt, J. B., “Small-Scale Propeller Performance at Low Speeds,” M.S. Thesis, University of Illinois at Urbana-Champaign, 2005. The Volume 1 page says these online files include a wind-tunnel correction that post-dates the thesis, and that the online files should be used rather than the thesis tables. Thesis · correction note.