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#11
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On Apr 20, 12:05*am, Darryl Ramm wrote:
On Apr 19, 3:53*pm, wrote: On Apr 19, 1:51*pm, wrote: I've have a Cambridge 302 in my glider. *I have the setting at 0% since I have the total energy probe fed into it, along with the pitot tube and static port. *The te tube is split just behind the cockpit as recommended. *The static and pitot are split or "t'd" behind the instrument panel. When I push hard forward to increase airspeed.....the cambridge VSI goes up to 10knots positive. Then when I pull back to bleed off airspeed.....the VSI goes down to 10 knots negative. The manual says to increase the % , but doesn't say how much. Another option is to not use the te tube and put it at 100%. The te probe in my glider is located about 6 feet behind the wing spar on the top of the fuselage. *It's not the conventional spot on the rudder. Any thoughts? *Recommendations? Scott, Go to screen 10 on the CAI 302 and note *the indicated airspeed. *You may have the Pitot & static switched. *Which mode are you in when this happens climb or Cruise? At TE probe requires that the Compensation be set at 0%. *The Probe supplies the Compensation. Richardwww.craggyaero.com And that was a clever suggestion - pitot and static swapped and the 302 in cruise mode and configured to be a super netto or netto vario so the indicator relies on the airspeed.... Note to Scott - the altimeter display on the 302 home screen has nothing to do with the static plumbing, it senses cockpit ambient pressure, so is cannot help debug this question. So try what Richard suggests. Darryl If that turns out not to be the problem a simple pressure check for leaks is in order. 9B |
#12
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On Apr 20, 7:52*am, wrote:
On Apr 20, 12:05*am, Darryl Ramm wrote: On Apr 19, 3:53*pm, wrote: On Apr 19, 1:51*pm, wrote: I've have a Cambridge 302 in my glider. *I have the setting at 0% since I have the total energy probe fed into it, along with the pitot tube and static port. *The te tube is split just behind the cockpit as recommended. *The static and pitot are split or "t'd" behind the instrument panel. When I push hard forward to increase airspeed.....the cambridge VSI goes up to 10knots positive. Then when I pull back to bleed off airspeed.....the VSI goes down to 10 knots negative. The manual says to increase the % , but doesn't say how much. Another option is to not use the te tube and put it at 100%. The te probe in my glider is located about 6 feet behind the wing spar on the top of the fuselage. *It's not the conventional spot on the rudder. Any thoughts? *Recommendations? Scott, Go to screen 10 on the CAI 302 and note *the indicated airspeed. *You may have the Pitot & static switched. *Which mode are you in when this happens climb or Cruise? At TE probe requires that the Compensation be set at 0%. *The Probe supplies the Compensation. Richardwww.craggyaero.com And that was a clever suggestion - pitot and static swapped and the 302 in cruise mode and configured to be a super netto or netto vario so the indicator relies on the airspeed.... Note to Scott - the altimeter display on the 302 home screen has nothing to do with the static plumbing, it senses cockpit ambient pressure, so is cannot help debug this question. So try what Richard suggests. Darryl If that turns out not to be the problem a simple pressure check for leaks is in order. 9B- Hide quoted text - - Show quoted text - The pitot/static lines are correct. There is no leaks in the system. All the lines and capacities are brand new now. The Airspeed on page ten indicates correctly. It's within a couple knots of the mechanical airspeed indicator adjacent to the cambridge. My question is, how much %? The manual address this issue by stating..."increase the % if this is happening".....but doesn't say just how much. I guess I can just try 10%, then 20%, then 30% and so forth. But would much rather have a more educated attempt at setting this the right way. |
#13
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In addition to good advice from others, I'd start by taking the
mechanical vario off the system. The 302 is very fussy about sharing lines with other instruments, and flow-based varios in particular. Get the 302 working right on its own, then see if you can add the other one back without making the 302 work worse. Also leak check the pitot and static too. I had weird 302 problems twice that came down to leaks in the ASI and ASI tubing. John Cochrane |
#14
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On Apr 20, 6:38*am, wrote:
On Apr 20, 7:52*am, wrote: On Apr 20, 12:05*am, Darryl Ramm wrote: On Apr 19, 3:53*pm, wrote: On Apr 19, 1:51*pm, wrote: I've have a Cambridge 302 in my glider. *I have the setting at 0% since I have the total energy probe fed into it, along with the pitot tube and static port. *The te tube is split just behind the cockpit as recommended. *The static and pitot are split or "t'd" behind the instrument panel. When I push hard forward to increase airspeed.....the cambridge VSI goes up to 10knots positive. Then when I pull back to bleed off airspeed.....the VSI goes down to 10 knots negative. The manual says to increase the % , but doesn't say how much. Another option is to not use the te tube and put it at 100%. The te probe in my glider is located about 6 feet behind the wing spar on the top of the fuselage. *It's not the conventional spot on the rudder. Any thoughts? *Recommendations? Scott, Go to screen 10 on the CAI 302 and note *the indicated airspeed. *You may have the Pitot & static switched. *Which mode are you in when this happens climb or Cruise? At TE probe requires that the Compensation be set at 0%. *The Probe supplies the Compensation. Richardwww.craggyaero.com And that was a clever suggestion - pitot and static swapped and the 302 in cruise mode and configured to be a super netto or netto vario so the indicator relies on the airspeed.... Note to Scott - the altimeter display on the 302 home screen has nothing to do with the static plumbing, it senses cockpit ambient pressure, so is cannot help debug this question. So try what Richard suggests. Darryl If that turns out not to be the problem a simple pressure check for leaks is in order. 9B- Hide quoted text - - Show quoted text - The pitot/static lines are correct. *There is no leaks in the system. All the lines and capacities are brand new now. The Airspeed on page ten indicates correctly. *It's within a couple knots of the mechanical airspeed indicator adjacent to the cambridge. My question is, how much %? *The manual address this issue by stating..."increase the % if this is happening".....but doesn't say just how much. I guess I can just try 10%, then 20%, then 30% and so forth. *But would much rather have a more educated attempt at setting this the right way. Electronic adjustment to TE compensation when I've tried it is a few percent at most. TE probes should work very well. What you are describing sounded like a significant problem, not something you tweek electronic compensation to a TE for. You seem to be confident you don't have any problems - you know you have no leaks - you have done a leak-down test on all the lines? All your mechanical varios work correctly right? They show climb etc. when they readings and readings match (and they have separate capacities T-ing off behind the seat... if they don't match then that might help show if one of the varios themselves are leaking etc.)... Have somebody else check your work. Try the static line at 100% compensation. If that does not work send the 302 to Cambridge for repair or try swapping with another to see if that works. Darryl |
#15
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On Apr 19, 1:51*pm, wrote:
When I push hard forward to increase airspeed.....the cambridge VSI goes up to 10knots positive. Then when I pull back to bleed off airspeed.....the VSI goes down to 10 knots negative. To answer you question directly - I don't believe you can fix the problem you describe with electronic compensation. Here's why: If I remember correctly an uncompensated vario reads climb when you bleed off airspeed and sink when you accelerate. This is because with static pressure only as the pressure source (no compensation) your vario will indicate the altitude change irrespective of any associated change in kinetic energy. Your description reads like the opposite, or OVER-compensation. I believe there also is an effect from the initial drag of adding lift in a pullup (and presumably the opposite from reducing lift in a push- over maneuver). That causes the uncompensated vario to show some small altitude loss at the very beginning of a hard pullup (think of the glider "mushing" a bit when you pull hard). This means that on a hard pullup the vario would read momentarily down by 1 knot or so, then read up until the speed stabilizes - all in still air, of course. Putting this second effect aside for now, a pullup from 100 knots down to 60 knots will gain you about 250 feet in about 10 seconds - depending on the steepness of the pullup. That translates to 15 knots average climb rate. You will see more climb rate early in the pullup than at the end. If you were reporting 10 knots of positive climb rate on a pullup then it would lead me to believe that you are getting little or no total energy compensation and you should set the CAI 302 to 70% or so. This has two problems: First, you are reporting behavior that indicates 70%+ OVER-compensation, not under. Second, I'd be hard- pressed to recommend to someone that they put that much electronic compensation on top of a TE probe since you are likely masking a big problem. Finally, you are asking for a specific answer to an insufficiently defined problem. Without knowing the pullup profile the fact that you are showing 10 knots on the vario doesn't really give enough information to know how to set your instrument. I generated an answer by assuming a profile - but I don't really know what kind of pullup you used to generate this result. The glider matters too, but my analysis ignores this detail in favor a of a simple energy conversion relationship. Hope that's helpful. 9B |
#16
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On Apr 20, 9:09*am, wrote:
On Apr 19, 1:51*pm, wrote: I generated an answer by assuming a profile - but I don't really know what kind of pullup you used to generate this result. The glider matters too, but my analysis ignores this detail in favor a of a simple energy conversion relationship. Oh, and I generated an answer also based on the assumption that your vario is behaving in a manner opposite to what you described - unless I missed something in college physics. 9B |
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