Phoenix gliding performance

[Eric Greenwell]

I asked Jim Lee (in an email) if the polar we have was calculated, or based on measurements, and if he knew of any comparison flights with similar performance gliders. He had a pretty good answer:

Both. The polar was originally calculated by the factory, and then modified by measurements (see "data").

I have flown several glide comparisons with the Lambada, Blanik L23, and Pipistrel Taurus. Lambada glides were done for a Phoenix altitude loss of 3000' at 50, 60, 70, and 80kts. Difference in altitude loss of the Lambada at these speeds were (from my memory) 150', 200', 500', and 800'. Blanik glides were unscheduled glides in the vicinity of Seminole Lake Gliderport where I noticed better glide performance of the Phoenix. Taurus comparison was one on one out and return. The Taurus would beat me in glide and then I would catch up in climb. We returned to the gliderport together after an hour flight.

My noodling with the polar suggested the Phoenix was at least as good as the Ka-6, unless it was very weak, and better if it was strong (much higher wing loading). Since my first glider, many years ago, was a Ka-6, and I got my Diamond Badge in it, I thought that was more than adequate performance for my soaring and travel plans. I'm glad to see the polar is based actual measurements, and confirmed with comparison flights.

[Ed Adib]

Hi Eric,

We have a Phoenix on order. I have downloaded the manual but there is almost nothing in it about soaring performance. Is there another source for that? How can one get the polars for the glider? Was your manual different or more complete that the on on line?

Thanks.

Ed

PS. After I wrote the post, I found the polars in the knowlegebase section.

I asked Jim Lee (in an email) if the polar we have was calculated, or based on measurements, and if he knew of any comparison flights with similar performance gliders. He had a pretty good answer:

Both. The polar was originally calculated by the factory, and then modified by measurements (see "data").

I have flown several glide comparisons with the Lambada, Blanik L23, and Pipistrel Taurus. Lambada glides were done for a Phoenix altitude loss of 3000' at 50, 60, 70, and 80kts. Difference in altitude loss of the Lambada at these speeds were (from my memory) 150', 200', 500', and 800'. Blanik glides were unscheduled glides in the vicinity of Seminole Lake Gliderport where I noticed better glide performance of the Phoenix. Taurus comparison was one on one out and return. The Taurus would beat me in glide and then I would catch up in climb. We returned to the gliderport together after an hour flight.

My noodling with the polar suggested the Phoenix was at least as good as the Ka-6, unless it was very weak, and better if it was strong (much higher wing loading). Since my first glider, many years ago, was a Ka-6, and I got my Diamond Badge in it, I thought that was more than adequate performance for my soaring and travel plans. I'm glad to see the polar is based actual measurements, and confirmed with comparison flights.

Edited September 7, 2013 by Ed Adib

[Eric Greenwell]

Hi Ed,

Finding the files isn't obvious at first, but I'm glad you did. I don't have a manual yet, and glider isn't due until the end of the year. I've looked at a couple manuals, including one from Russ Owen's glider that he picked up in Feb. 2013, and none address soaring. For now, we'll have to depend on reports from Russ, Jim, and other owners that have done significant soaring in it.

What would also be useful is comparison flights with similar performance gliders, such as the Ka-6, PW-5, Ximango, perhaps the Carat, to give us a better idea of it's capablities. That would help us determine best thermalling speeds and flap settings, too.

[kd6veb]

Hi Gang

I spent a little time nearly 2 years ago on the published Phoenix polars. To obtain the best L/D for the glider draw a tangent to the polar curve from the origin. With both sets of polars that I had then the best L/D for the 15 meter wings came out at 28.5 and for the short wings 22. I checked those results with reviewing long glides of IGS files with SeeYou on a PC. I found pretty good agreement overall.

My perception is that the most touring motor gliders have best L/Ds between 25 and 30 and that the Phoenix is as high performance as any touring motor glider. We do give up performance because of side by side seating. fixed undercarriage and a non retractable prop. The disadvantage compared to a high performance glider is that you have to spend more time climbing to make up for your increased sink rate. That's one of the reasons I have purchased a DG1001M. Glide is 46 compared with 28.5. An XC to the Whites can be done in a significantly shorter time than with a Phoenix. Regardless at this time I am keeping the Phoenix which I enjoy immensely as a high performance power plane and a glider as I commute between San Jose, CA and Minden NV.

Dave

[Ed Adib]

Hi Eric & kd, Thanks for your comments. Very helpful. The polars I found have m/s for vertical speed & km/h for airspeed. It's kind of a headache to convert to knots for both but guess I have to get the calculator out! Was hoping for a better LD than 28.5/1 but guess that was too optimistic. A while back I almost bought a Stemme but I was warned by some owners against high maintenance issues. One of them said you almost need two because there is a good chance one of them is in the shop at any given time! Also looked at Ximango's but the wing folding process scared me off! The Phoenix became desirable due to its relative simplicity, less weight & CF construction.

[Barry.h]

I know this is a very old thread ... but can anyone point me to where I can find the polar curve of either the Phoenix or the Sundancer/Lambada? I would like to set this up in XCSoar - so the data for that would be even better!!