All Activity

Hi TC and All, Sounds like a challenge so I will try to take this on. And I will speak for Ed as best I can and he can chime in as warranted. Ed and I have been as insistent as is possible to be. And we have been worn down by the lack of responses or discussion from the 2 past and current Phoenix manufacturers. Most of what I know about aerodynamics and composite structures comes from my aeronautical engineering background at the University of Colorado, my work on a composite stealth aircraft at the Raspet Flight Lab at Mississippi State University, independent study, and gleaned information from the sailplane industry. Ok, maybe some YouTube videos as well. My understanding of the Phoenix aircraft comes from being the US agent for Phoenix s.r.o., test flying every Phoenix I sold including flutter testing, multiple trips to the Phoenix factory where I worked side by side with the fabricators, and exhaustive conversations with Martin Stepanek, Pavel Urban and Mirek Kabrt at Vanessa (who did engineering work and CZ certification for the Phoenix and the VL3). Flight testing of every Phoenix that I sold proved that IN SMOOTH AIR there is no flutter on any control surface up to 150kts. HOWEVER, during attempts to excite flutter by sharp raps on the control stick or rudder pedal, mild flutter could be induced as low as 135kts on the rudder (during the pull up with a positive angle of attack while decelerating). Once this was found, no further flutter excitation tests were performed above this speed. Phoenix Air s.r.o. built a Phoenix with sensors embedded in the wings, fuselage, rudder, and elevator. The Phoenix was suspended on cables, and vibrators were used to establish a flutter speed. They found the need to add counterweights to the elevator, but none to the rudder. I strongly disputed this finding. Phoenix Air subsequently starting building elevators with outboard "horns" as counterbalanced elevators. During my ongoing production Phoenix flight testing I was now able to excite flutter on the new elevator at 130kts whereas the "old" non-balanced elevator would not flutter at any speed. I reported this finding to Martin and again urged counterbalancing the rudder. I have followed up with Pure Flight and JMB with this concern. I have seen the photo of the JMB "solution" to rudder flutter. I have never seen or heard of any device such as this but I don't dispute that this is an existing device on other aircraft that I don't know about. But it certainly does not exist within the current sailplane designs. Sailplanes use lead counterbalance weights ahead of the hinge line on the spine of the control surface. (If there is not room for enough lead, such as with Dick Butler's Concordia, a heavy metal - tungsten, is used). My Jonker JS1 and my Binder EB29R both have lead counterbalanced rudders. And the maintenance manuals dictate the weight range of the rudder ahead of the hinge line and the moment arm permissible. In the case of a repair or painting, the rudder must be reweighed with it hinged on the hinge line and a scale on the trailing edge. These numbers are documented in the manual. We have not been given this information which leads me to suspect that the counterbalanced weight of the rudder has never been an item of concern from the factories. And it should be. Barry Hendy reported in August following a trip to the factory that "The consultants explained that their testing had identified a flutter mode that was possible in the existing design. My understanding is that it is a multimodal interaction of the rudder and the tortional twist of the T-tail. The prime solution is to add mass balance to the rudder. They have a new rudder design that was fitted to their test aircraft and they were expecting to begin testing soon. (That was late May). The overall weight has not changed but it has mass balance down the front of the spine. There was discussion about the spring-loaded tension of the rudder pedals being a possible factor and there is a design for a closed-loop rudder cable system. They were undecided if this was necessary and would be part of the solution." Well, what says the factory now? As an LSRM, I am legally allowed to remove the rudder and add counterbalance weights to the rudder as per a factory bulletin. It will be easy to do and is the correct response to address rudder flutter. Also, the Phoenix is very nose heavy. It is actually at the front end of the CG range as it comes from the factory. I have added a 35 lb car battery to the baggage area of my Phoenix to provide lots of engine off power and to shift the CG more to the rear. It flies and thermals much better that way. Adding lead counterbalance weights to the rudder will actually help that situation too. An additional inquiry should be made to the attachment of the rudder cables to the rudder. This is via swaged cable thimbles onto a bolt. There is some play at this attachment which can also produce flutter. For now, as always, it is imperative that your feet on the rudder pedals produce the resistance to flutter, especially at speeds above 120kts IN THE CONVECTIVE LAYER which produces the turbulence which can excite the rudder into flutter. And never use the autopilot in the convective layer because as the plane enters lift, the autopilot drops the nose and you are above Vne in a flash. As far as I know, there has been no testing regarding flutter when the zig zag tape has been applied to the rudder. Consequently, I will not add the zig zag tape to my rudder until I see the factory data. Even then, I will reproduce my own flight testing to prove that it does not have a negative effect. As to a speed reduction bulletin, as far as I know, JMB has still not gone through any ASTM approval process and is not a recognized LSA manufacturer by the FAA. Therefore, they have no authority to issue any bulletin regarding the Phoenix. Finally, as I said before, I have not heard of the gizmo that JMB proposes to add as flutter protection. That's right, gizmo, gadget, contrivance: I intend those to be derogatory words in place of much stronger words that I could use to show my disdain for JMB and their lack of timeliness and common industry standards in attacking this issue. Not to mention their utter failure to communicate with their loyal Phoenix owners around the world. Long live the Phoenix! Jim Lee

Sorry to ask this out loud but why are there not more insistent questions about this? JMB, Ed, JIm: I know you monitor this board. Answer the question.... Tom

Try this one.. I loaded it from my google drive. Andrea Clauss in France will have the rudder linkage installed he told me as he will fly to JMB with his Phoenix. He can tell us all how this goes.

Thanks Alan, This picture did load for me. I am guessing all of us would appreciate more information about the modification . Tom

Tom There is nothing official from JMB yet on the fix. Alan

I inserted the picture again. It works for me when I open the PHNX forum.

Allen, The picture did not load for me. Is there any official info available from JMB? Tom

Andreas Claus sent this photo to me. He will have this mechanism installed at JMB - Phoenix in the next few days. This is one of the means aimed to fix the rudder flutter issue. Some of the older models may also need the tail reinforcement as well I was told.

I have 1978 SF25E with worn brake shoes. I obtained new shoes a few years ago, but when I tried to fit them, they were a few mm too big. What are the diameters of the two different drums?

It’s on again! 2025 is shaping up as a great season. https://www.weglide.org/flight/889901 Here is an explainer: and todays flight

I am back for my 3rd season chasing the morning glory cloud. It is shaping up as a great year with some good prospects still to come. if you want to know more about the Morning Glory I made this intro video. And this was today’s flight. https://www.weglide.org/flight/889901 it is not often you see a Phoenix at the top of the WeGlide daily best list! I beat the Stemme!

I can ship only to the US.

Hello Bob, Sounds like a great idea. I have both planes and a TMG and my Sinus is my favorite by far. I would get on hangar lists today as it takes a while and these planes should not live outside if it can be avoided. We have a flight school in Monterey and are located at Salinas Airport KSNS. We have a Pipistrel Sinus that is in rental. www.soarmontereybay.com Nick at Soar Paso www.soarpaso.com is closer and has a Virus glider. Happy to help you out when you get to that point. Once you have a LSA license adding sport Glider is very easy, no checkride required just fly with CFI to proficiency and then get a proficiency check from another CFI. let me know if we can help. Clinton

Hello BobG here. Wanted to get some advice on my plans to Touring motor glider flying. Would appreciate any input. 1st Thoughts: a. SLA Cert.: Planning to get Sport Light Aircraft certification (private pilot licensing eventually), in year at nearby airport in Camarillo California (or other nearby), to learn basic skills, build flight hours and absorb knowledge, etc. It is close an only 30 minutes away, and logistically very doable. b. Glider Lessons: Subsequently, lessons, after completing SLA certification, and learn additional knowledge for soaring. In Palmdale (Llano) 90 minutes away. 3 hrs. drive is limiting. c. TMG. Subsequently, purchase a used Touring Motor Glider (TMG). Used 10-15 years, affordable - e.g., Pipistrel Sinus, Phoenix, Grob, Stemme, other. Fly out Camarillo, or other. Background 1. Hang Gliding. Started Hang gliding 20 years ago (dozen+ lessons; tandem) in Los Angeles . Loved it but Risk-Reward too high and left hang gliding before leaping off mountain alone. 2. Soaring. Did Glider rides instead, as I loved the feeling of flight, but 90 minute ride each way (Palmdale, Llano, CA). Soaring at Llano regularly, can be alot of driving. 3. TMG. Upon SLA certificate, glider lessons and enough flight hours, knowledge and skill then buy my used TMG. 4. TMG/Local. Final - Fly my TMG out of a local Southern California regional airport (Camarillo, etc); along with Tie down there. Summary It would seem that if I earn my SLA certificate (or private pilot), learn glider profiency (or whatever reg's require), I could fly a TMG into nearby mountain ranges (same as Palmdale nearby mountains) and even local desert, and return to local regional airport. I am also a little surprised not more pilot do this. I would appreciate any input. Thank you in advance. BobG

Seems like the rails are the most vulnerable to breakage and you can order them separately. Regardless, I bet it flys just fine now that you know how precious they are 😜.

Omg! $500 with shipping and tariff.

Thanks all. After some consideration, I am comfortable to use the Odyssey PC-625 AGM battery. And my battery switch has either/or/both positions.

Because you have an LSA, you have lots of great options battery options. Two options are the certified batteries made by EarthX and Concorde. Those companies paid untold sums to get their products legal to be on Part 23 aircraft and they are priced as such to make their money back. Since you cleverly bought and fly a aircraft that has been made to ASTM standards instead of Part 23, you have many more options. These standards have been shown to result in no loss of safety and are why the LSAs have been expanded under MOSAIC. I use two AGM batteries. We'll save the advantages of an aft CG for another thread.

My vents are made by Mecaplex (name is printed very subtly on the top and bottom rail) and can be purchased on wingsandwheels.com Bring your sense of humor. The prices have gone up considerably since a year ago.

I changed to 2 x Lithium a while back. Yes, lithium drops off quickly (not instantly) when flat, but for the same size and much less weight you get a lot more capacity. I mainly wanted more capacity for extended soaring. DONT CUT CORNERS. I assume you have seen video of lithium (iron) batteries burning. Only use aviation grade which address all (?) the safety issues. I used EarthX, I think they are the leaders and are certified in many aircraft. There is a Letter of Authority floating around from Jim Lee's days providing the authority to make the change. (we are LSA remember!) EarthX say they are fine with your old regulator, but I changed to a better regulator set to lithium voltages. I think you might get more charge in, but check with EarthX. It soundes like you have 2 batteries now. How are they wired/switched? I have mine separated; one for avionics and one for the engine, so if I do run the avionics low (has happened a few times) I always have the starter battery. And if the starter battery dies, I can switch the avionics (bigger) in to start the engine. Since I changed I don't get any brown-out reboots of the avionics when starting, much longer soaring time with all the avionics and plenty of starting grunt.

the small vents that flip in and out.