F1 Evo -Final performance assessment 24 May 2005

Hello!

I’m excited to tell you all that the Evo wing is finalized in its format, and I have some data that I can confidently say is reliable, and applicable to the production wing. More data will be obtained as more flights are flown on the prototype ship, and as customer-built EVO's are finished, but it’s safe to say that the stall speed is still lower than what the standard wing delivers by a significant margin. Our pitot/static system does not measure reliably at such angles of attack, so I will have to resort to flying next to a local Piper J3 to get better measurements.

Yes, the stall is slower than all available RVs in the area, so those cannot be used to measure the speeds. I would guess it is 4-5MPH slower than a local RV8 that is very well constructed and clean.

But now I suppose you want to know how FAST it is? Well, I saw some complaints regarding speeds some manufacturers are claiming for their ships, and the writer suggested that 75% at 8000’MSL would be a good standard measurement for all manufacturers to list. Well, I can come close to that – I can get enough manifold pressure to get about 68% out of my engine, and at that setting (23.5”/2300RPM/12.5GPH, lean of peak) the factory demo ship will give a TAS of 207KT. I measured the speed with the GPS in 3 directions (TruTrak autopilot was doing the flying), and 207 was the average. I slowed the engine to 2100RPM (about 60%) and re-leaned to 11.5GPH, again, lean of peak – still had the throttle wide open – and the ship slowed to 201KT TAS. Ground temp was 72F, so temps were a bit above standard.

*In changing the wings on Ole 84, we also did some engine mods (a top overhaul, with a compression increase to 9.5:1) -- estimated HP of the engine is now 290 -- about 30HP more than stock. So, comparisons of before/after speeds are slightly skewed by the engine. I would estimate a 10KT speed increase if one were to simply change the wings on an existing ship, and make no engine changes at the same time.

In another test, while flying to Sun-n-Fun in April 2005, I saw forecast winds of 55-60KTS at 15000MSL on my planned travel day. I loaded my baggage and some handouts for the show, set up the O2 bottle, and off we went at 0640 local. After climbing up, I saw ground speeds of 265KT along the route, and the fellas at Flight Watch confirmed wind speeds of 60KT at my altitude. Thus, it seems that the ship holds 200+KT TAS to at least 15,500MSL…but I’d need a better heater, or warmer clothing, to fly those altitudes on a regular basis.

Power setting at that altitude was about 17”MP/2400RPM/9.8GPH, and temps were fine. It took me 3.5 hrs flight time to get from Taylor Texas to Zephyrhills FL. Not bad, I’d say!

And now you want to know ‘how she feels’? Well, I have a bit of time in a Beechcraft Debonair, and the Evo has a similar personality; very stable, even in turbulence; a good ride (you don’t have to worry about hitting the canopy too much), and it’s very smooth and responsive. Controls remain light thru 200KIAS, and are still good at 240KIAS. The standard wing ships start out a bit lighter on the ailerons, and the control forces of the two types cross at about 140KIAS ; the standard wing ships keep getting heavier from that point until they are VERY heavy at 240KIAS, but the Evo doesn’t ‘load up’ in the same manner. Pitch forces are a bit lighter to start with, but I will still fine tune that area on my ship to see if I can make the pitch match the ailerons better without making the pitch too light when the ship is loaded for cross-country (this change will be an option for all existing ships, and will be standard on production kits soon). If this mod is a worthwhile improvement, I will let you know how to do it on your ship as well.

Roll rate:The roll is a bit slower than the standard wing – but about the same as any of the RV series, which is great for spirited flying. The engineers tell me I can increase the aileron deflection a bit since we removed most of the camber, and this will be done to see if the roll rate can be increased -- without making the ailerons feel too heavy. Everything is a compromise, and we will have adjustable settings in the production ships to allow owners to tune their individual ships’ control forces, and response, to their liking.

CG range: As the tapered wing has a smaller MAC, the CG envelope is naturally narrower too. In practical applications, an example would be: if the std wing ship would carry 100LBS in the baggage area in a certain pilot/passenger/fuel loading condition, the Evo would safely carry ~70-75lbs. That’s still a good capacity!

I’ll keep going with flying and data acquisition, and submitting reports as I get reliable data points. I can’t wait till Reno ‘05 comes around – I want to see how the modified wing compares with the as-delivered wing used in 2004 – and those speeds were 15MPH faster than the standard style wing gave us in 2003! I’d guess that Ole 84 is about 17KT faster now, judging from the speed test sheets I have from all the test flights flown since the plane first flew in 2003, but I won’t suggest that my data is as reliable as it would be if a trained test plot flew the tests. I do think it gives a good indication of the capabilities of an average F1 Evo – certainly cleaned up versions will be faster, and I intend to test that theory too!

Cheers!
Mark