Shaun, to make comparisons more complicated yet, Kim Prout's Europa,
at time of CAFE test, had the aftermarket piston mod (alleged 92HP,
but who knows). He found more performance improvement in the 2-blade
constant-speed Whirlwind -- in general true for 2-blade in cruise,
better having controllable pitch.
At 100% power, I compute approx. 8% greater velocity for 914 vs 912.
"Approx" because Hoerner says it most closely relates to only wing
efficiency, which varies, not total drag of A/C. I don't understand
that, but he should know. :-) A Europa could thus come out a bit
higher.
Regards,
Fred F.
> I reread the CAFE report on Kim Prout's N111EU, as it's often offered up as
> the gold standard
> in performance.
> ALT=8K RPM=5200 PROP RPM=2286 WEIGHT=1293 LBS CAS=136.1 MPH TAS=153.6
> MPH/133.5 KTS
> ALT=8K RPM=5400 PROP RPM=2374 WEIGHT=1294 LBS CAS=138.0 MPH TAS=155.7
> MPH/135.4 KTS
> ALT=8K RPM=5500 PROP RPM=2416 WEIGHT=1294 LBS CAS=138.7 MPH TAS=156.5
> MPH/136 KTS
>
> ALT=1K RPM=5800* PROP RPM=2548 WEIGHT=1270 LBS CAS=169.1 MPH TAS=171.9
> MPH/149.2 KTS
> *not stated
>
> Jim and Augustene report 142kts (is that CAS or TAS?) /6000ft/ 5300 RPM.
> That's full cruise RPM for the 914, I think.
> 5500 is full cruise RPM for the 912 Kim uses.
> HP at altitude: 914: 100HP (turbo!) 912: 78*0.8=63 1.58 speed should
> be proportional to cube? root of power.
> All other things equal, the 914 should be about 15% faster than the 912.
> I will assume that Jim is reporting CAS and use a 1.14 CAS/TAS factor ( off
> somewhat ) to get TAS=162.5 MPH.
> Jim is about 4% faster than Kim.
> Kim must be using aeronautical drag grease.
>
> Shaun
|