Changing the subject> When is the serial number assigned to kit-built airplanes, and is this the date of airplane? Is it when the kit leaves the factory, first flight, or when it is assigned a registration?

My guess is serial number is a misnomer: airplane n might take six years to build, while n+1 might take six months. Construction time for expensive kits that involve a lot of assistance probably varies less than simpler kits, but models evolve.

Is there a master list of options for the Evo which could be used to compare two Evos? I understand experimental airplanes will vary much more than those certified.

Ashley

Lancair assigns the serial when it leaves the factory. I don't know about the "model year", I'm not sure that's a meaningful term in the homebuilt world.
Indeed. Recently coming out of the build shops are Evos with serials in the high 60s while #9, a true "home built", first flew just last month.
No. There is a short list of factory options on the Lancair website but each build shop also offers their own.

Serial numbers are assigned by the manufacturer in order. The "date" of an airplane is determined by the year the airworthiness certificate is assigned.

There are lots of criticisms of this test report and it reeks of confirmation bias.

But, what caught my eye is that the prop without the boots looks bigger diameter. So I printed the pictures of the booted and non booted props and then took measurements. Using the spinner backplate diameter as a constant, the non booted prop is 3.5% larger diameter. This is too much variation to be accounted for by measurement inaccuracy. Also, if you take a good look at the photos, it does seem larger.

See for yourself.


The change in prop diameter would dominate the test.

Other things that should raise concerns:

10% less power took 15% less fuel. How so? They must have monkeyed with the mixture to do that which they never discuss.

Their charts say the booted props is about 8% less power. But that doesn't produce 5% speed drop, that is only 2.6% speed drop. They don't seem to know the power versus speed relationship.

The booted picture is middle of the day, high sun. Non booted picture is late in the day, evening sun. Might have been cooler then when the engine can produce more power.

You can easily get a 5% variation in speed just from mixture, trim, weights, lift, winds (affecting lift), technique, etc.

You believe what you want to believe. If you pay the money for this prop, and you believe it is working, then you got what you paid for.

Mike C.

There are lots of criticisms of this test report and it reeks of confirmation bias.

But, what caught my eye is that the prop without the boots looks bigger diameter. So I printed the pictures of the booted and non booted props and then took measurements. Using the spinner backplate diameter as a constant, the non booted prop is 3.5% larger diameter. This is too much variation to be accounted for by measurement inaccuracy. Also, if you take a good look at the photos, it does seem larger.

See for yourself.


The change in prop diameter would dominate the test.

Other things that should raise concerns:

10% less power took 15% less fuel. How so? They must have monkeyed with the mixture to do that which they never discuss.

Their charts say the booted props is about 8% less power. But that doesn't produce 5% speed drop, that is only 2.6% speed drop. They don't seem to know the power versus speed relationship.

The booted picture is middle of the day, high sun. Non booted picture is late in the day, evening sun. Might have been cooler then when the engine can produce more power.

You can easily get a 5% variation in speed just from mixture, trim, weights, lift, winds (affecting lift), technique, etc.

You believe what you want to believe. If you pay the money for this prop, and you believe it is working, then you got what you paid for.

Mike C.

But, what caught my eye is that the prop without the boots looks bigger diameter. So I printed the pictures of the booted and non booted props and then took measurements. Using the spinner backplate diameter as a constant, the non booted prop is 3.5% larger diameter. This is too much variation to be accounted for by measurement inaccuracy. Also, if you take a good look at the photos, it does seem larger.
Mike C.

Using width of cowl, I get the non booted prop is 4% larger.

This is comparing the ratio of prop blade length to cowl width which negates the issue of the photographer being closer or further.

This agrees reasonably well with the prior measurement using the spinner backplate as reference (+3.5%).

Measurements in both cases taken off printouts (same printer) using calipers to the 0.001" resolution. I was measuring the top blade.

Perhaps it is some sort of perspective issue in the photos but they don't seem to be taken from wildly different places. The only reason I thought to check this is because it looked different in size just by eye.

Mike C.

Using width of cowl, I get the non booted prop is 4% larger.

This is comparing the ratio of prop blade length to cowl width which negates the issue of the photographer being closer or further.

This agrees reasonably well with the prior measurement using the spinner backplate as reference (+3.5%).

Measurements in both cases taken off printouts (same printer) using calipers to the 0.001" resolution. I was measuring the top blade.

Perhaps it is some sort of perspective issue in the photos but they don't seem to be taken from wildly different places. The only reason I thought to check this is because it looked different in size just by eye.

Mike C.

I apologize in advance to contributing to the thread drift, but a couple of comments with respect to Mike Ciholas' criticism of the Villinger data,

I don't have performance charts for the M20K 231 turbocharged (the test airplane), but the normally aspirated J model shows a predicted TAS of 165 kts at 75% power and 155 kts at 65% power at 6000 ft. Fuel flow is 12.2 and 10.8 gal/hr respectively. Bob Kromer notes TAS of ~163 kts at 8500 ft for the turbo. Unless I'm missing something, Villagers numbers don't seem out of the ordinary, taking into account that this is not a true "apples to apples" comparison. I would note that 75% power going to 65% power is more than a 10% power reduction, although it is 10 percentage points.

It appears the angles of the two photographs are different; absent a tripod and the airplane in exactly the same position, it's really hard to conclude the props are of different lengths. They state they used the same model prop. It's possible they're of different lengths, but one would think they'd mention it (of course one might be wrong...).

They note the flights were 3 hrs apart, and also state OAT 14.7 C, 1012 QNH, altitude 6000 ft., full fuel and 1 pilot. Maybe this is in fact not the case. Of course if you choose not to believe their test conditions as stated, that also represents a confirmation bias.

There is ample room for critical review and skepticism. Knowing that the fuel flow settings were the same is certainly important. They report IAS. Reporting GS based on the average of four legs flown at 90 degrees would give accurate TAS. How reproducible are the data (their data is for one flight in 2010)? Are other planes using this prop, and are there accurate data comparing a range of flights over a range of data points (conditions). With respect to Gerry's airplane, what could he expect to see at roughtly twice the speed and at 28,000 ft or so.

It's possible that the test conditions favored their prop, or that the data are misrepresented. Since scientists are data driven, it might be more appropriate to focus on the paucity of data points (n=1, essentially), rather than invoke deliberate misrepresentation. Nevertheless, it's interesting, and Gerry may find it worthwhile to pursue and obtain more data.

On a separate note Gerry, your plane looks tremendously exciting. We look forward to seeing it at Sun-n-Fun; it should be easy to spot! Do you have any performance numbers from the flights so far?

I think the perspective may be at issue with the way you are measuring. Try imagining the prop as a triangle and averaging the length of the sides to come up with a prop 'size'. Or, using your length of blade measure at least average the 3. You'll only need a ruler to 0.001 meter resolution...

The only reason I jumped in was a previous life understanding measurement variation, along with previously watching the Brain Games show you referenced.

Sorry for the thread drift Gerry. I think I've said it before in this thread, but awesome plane! Any chance you'll take it to OSH?

Unfortunately I don't think it will make Sun N Fun... They had a converter box fail that sends engine data to the Garmin and they were hunting down the issue for some time until they realized the box had failed. They are supposed to call me this morning to talk. I'm sure they will tell me there isn't enough time to finish everything, which is understandable with what little time is left. It's disappointing but it happens.

In regards to the Villinger test. I read that NASA had performed similar tests and had similar results but couldn't make a prop survivable that had internal deicing technology. I'm going to try my best to see if there isn't any information out there on the subject.

Well, I spoke with RDD this afternoon and they still feel confident the plane will make it to Sun N Fun! I look forward to flying it there!

Also, they confirmed that there is inefficiency on propellers, especially MT props since the deice heating element comes up the prop shaft further than on a Hartzell. Said anywhere around an 8kts gain on an Evo for example is absolutely possible, but also said gains will vary based on prop and plane combinations.

Just received word that the plane is flying today. Everything seems to be going well. They plan to fly it for 5 hours working toward the 40 needed to fly off during phase 1 flight.

Oh man, I don't know how you are getting any sleep!

Who said I was!?