Low test numbers on Standard Cirrus, what could it be?

If you want another set of data, take a look at this video I made of
the Open Cirrus. All the instruments were calibrated, you can see the
30 sec digital averager on the panel top, the timer on the lower left
with the altimeter will give you a timed measurement, and the Winter
on the left is a 2 min averager. This flight is on OLC if you want
the GPS data.

I don't have time to comment on you results, except to say reread the
Johnson and Bikel articles on test measurement.

http://www.youtube.com/user/aerodyne.../2/GJLeuUYbWdM

aerodyne

On Aug 11, 10:53*am, aerodyne wrote:
If you want another set of data, take a look at this video I made of
the Open Cirrus. *All the instruments were calibrated, you can see the
30 sec digital averager on the panel top, the timer on the lower left
with the altimeter will give you a timed measurement, and the Winter
on the left is a 2 min averager. *This flight is on OLC if you want
the GPS data.

I don't have time to comment on you results, except to say reread the
Johnson and Bikel articles on test measurement.

*http://www.youtube.com/user/aerodyne.../2/GJLeuUYbWdM

aerodyne

Thanks, interesting video. I just uploaded my video in two parts.
I'm pretty sure I collected the data correctly. Here is part 1.

http://www.youtube.com/watch?v=MgzhZDN_9RY

Here is part 2.

http://www.youtube.com/watch?v=Ic4DNgox7MA

I find the Excel spreadsheets hard to understand. There is one called
Performance.xls that is a blank. More homework I guess.

.... Aaron

If anyone's interested in attempting to figure out, or give feedback
on my glide video, I'd be interested in comments. As I mentioned, the
numbers were not good.

http://www.youtube.com/watch?v=MgzhZDN_9RY

Here is part 2.

http://www.youtube.com/watch?v=Ic4DNgox7MA


.... Aaron

On Aug 12, 6:14*am, akiley wrote:
If anyone's interested in attempting to figure out, or give feedback
on my glide video, I'd be interested in comments. *As I mentioned, the
numbers were not good.

http://www.youtube.com/watch?v=MgzhZDN_9RY

Here is part 2.

http://www.youtube.com/watch?v=Ic4DNgox7MA

... Aaron

Errors in your ASI could account for a good chunk of your problems.
Have you tried a calibration with another known source? With the
knowledge of air density, you can calculate true airspeed and
indicated airspeed from your GPS data.

As others have also mentioned, you don't need much vertical air
movement to screw things up either.


Mike

On Friday, August 12, 2011 10:58:58 AM UTC-4, Mike the Strike wrote:

Errors in your ASI could account for a good chunk of your problems.

The ASI in the Standard Cirrus uses static air from underneath the wings. That will produce some error. (Dick Johnson mentions this in one of the test reports, I think.)

Your data points are all below expectation, though, so the more likely explanation would be error from other factors. I don't know about yours, but the gelcoat on my Std Cirrus looks pretty rough in some places. Also, if you look at other people's measurements, you'll notice quite an error, so multiple takes are necessary to get more reliable results.

PS.: Have you tried to put tape on the underside of your wing? I hear that'll give you 5 L/D points! ;-)

It's been a while since we last heard about the turbulators project. Would be interesting to hear any updates.

Ramy

I think we may do more tests this fall. Was just at Williams Soaring Center renting there excellent ships, an ASW27 and 24. The air was very stable and I had high tows to 8000 over the mountains. I also now have a Colibrii II logger so I may have more accurate altitudes compared to GPS only. I may just look at segments in SeeYou and work out the performance using altitude lost over time. This takes wind out of the equasion. I will do the same for flights I have done in the Standard Cirrus if I have some resonable segments. But we had an amazing season in Michigan so most of that data will be totally polluted by volitile air.

Since I did a range of speeds with the older Cirrus tests, it seems I should have found reasonable performance at ONE of the speeds. BTW, Our Cirrus finish looks excellent to me.

.... Aaron