If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
|
#1
|
|||
|
|||
Winter mechanical vario reading high
Last year my Winter mechanical variometer may have read a bit
high, but not very much. Today however, on my first flight of the year, the vario appeared to read 400 feet high in the air and about 75 feet high on the ground. With the vario reading 400 feet per minute up, the altimiter wasn't doing anything and the Cambridge electric vario was reading zero sink. I've searched the r.a.s. archives and found the advice about zeroing the needle using the adjustment under the faceplate and putting a trace of nail polish on the needle to weigh it down. Do these seem like appropriate repairs for this problem? Can anyone speculate on why the vario might read so much higher in the air than on the ground? Is there a plumbing problem I should look for to explain this? Thanks for any ideas. Alan |
#2
|
|||
|
|||
Winter mechanical vario reading high
Mine--(57mm) reads zero on the ground, but about 2 kt high in the air,
compared to a S-Nav. Yes I understand the "relative netto" thing, but this occurs while thermaling at 48-52 kt in a DG800B, with the pneumatic switch on "TE probe". In addition, the Winter is faster in response than the S-Nav with the Cambridge set on "fast" (1 sec). The DG factory installation has very short leads off a "Y" to the S-Nav and Winter, but they are on separate flasks--both 0.45l, with fairly long leads. I'm guessing a very small leak in the Winter. I have just removed it and will test tomorrow. I thought it was just me! -- Hartley Falbaum "Alan Meyer" wrote in message ... Last year my Winter mechanical variometer may have read a bit high, but not very much. Today however, on my first flight of the year, the vario appeared to read 400 feet high in the air and about 75 feet high on the ground. With the vario reading 400 feet per minute up, the altimiter wasn't doing anything and the Cambridge electric vario was reading zero sink. I've searched the r.a.s. archives and found the advice about zeroing the needle using the adjustment under the faceplate and putting a trace of nail polish on the needle to weigh it down. Do these seem like appropriate repairs for this problem? Can anyone speculate on why the vario might read so much higher in the air than on the ground? Is there a plumbing problem I should look for to explain this? Thanks for any ideas. Alan |
#3
|
|||
|
|||
Winter mechanical vario reading high
Hartley,
Could you elaborate a bit on this explanation? I would think that a leak would lead to a reduced response in all modes - showing a reading closer to zero than should be, whether going up or going down. I wouldn't expect a consistent up indication - but maybe I'm not thinking about it correctly. Thanks. Incidentally, regarding the alternative explanations, my plane is a 1966 era Libelle H301. The loss of flourescent paint seems possible on a 40 year old plane, but I'm surprised to find the effect so marked in just one year out of 40. Alan "HL Falbaum" wrote in message news Mine--(57mm) reads zero on the ground, but about 2 kt high in the air, compared to a S-Nav. Yes I understand the "relative netto" thing, but this occurs while thermaling at 48-52 kt in a DG800B, with the pneumatic switch on "TE probe". In addition, the Winter is faster in response than the S-Nav with the Cambridge set on "fast" (1 sec). The DG factory installation has very short leads off a "Y" to the S-Nav and Winter, but they are on separate flasks--both 0.45l, with fairly long leads. I'm guessing a very small leak in the Winter. I have just removed it and will test tomorrow. I thought it was just me! -- Hartley Falbaum "Alan Meyer" wrote in message ... Last year my Winter mechanical variometer may have read a bit high, but not very much. Today however, on my first flight of the year, the vario appeared to read 400 feet high in the air and about 75 feet high on the ground. With the vario reading 400 feet per minute up, the altimiter wasn't doing anything and the Cambridge electric vario was reading zero sink. I've searched the r.a.s. archives and found the advice about zeroing the needle using the adjustment under the faceplate and putting a trace of nail polish on the needle to weigh it down. Do these seem like appropriate repairs for this problem? Can anyone speculate on why the vario might read so much higher in the air than on the ground? Is there a plumbing problem I should look for to explain this? Thanks for any ideas. Alan |
#4
|
|||
|
|||
Winter mechanical vario reading high
Alan Meyer wrote:
Last year my Winter mechanical variometer may have read a bit high, but not very much. Today however, on my first flight of the year, the vario appeared to read 400 feet high in the air and about 75 feet high on the ground. With the vario reading 400 feet per minute up, the altimiter wasn't doing anything and the Cambridge electric vario was reading zero sink. I've searched the r.a.s. archives and found the advice about zeroing the needle using the adjustment under the faceplate and putting a trace of nail polish on the needle to weigh it down. Do these seem like appropriate repairs for this problem? Can anyone speculate on why the vario might read so much higher in the air than on the ground? Is there a plumbing problem I should look for to explain this? Thanks for any ideas. Alan I cannot explain 325 the 400 F/M error in the air but I think that I can explain 75 F/M of it. Previous posts on RAS may have explained this already so if this is repetitious, my apologies. The fluorescent material on the needle which allows it to be visible at night, emits particles and over the years, loses mass. It therefore eventually reads high. (I have never seen one read low on the ground but it may be possible). There is an adjusting screw behind the glass and has enough range for one or two adjustments before it requires more fluorescent paint to put it back into range. Paul |
#5
|
|||
|
|||
Winter mechanical vario reading high
Pneumatic total energy relies on applying a partial
vacuum (proportional to airspeed) on the static side of the vario. If you have a leak on the flask side, then the partial vacuum results in a flow through the vario and apparent climb. A leak on the total energy side would just result in poor compensation. You also mention long plumbing to the flask, this adds to the total volume on the flask side and can make the vario over read both lift and sink. At 03:18 10 April 2006, Alan Meyer wrote: Hartley, Could you elaborate a bit on this explanation? I would think that a leak would lead to a reduced response in all modes - showing a reading closer to zero than should be, whether going up or going down. I wouldn't expect a consistent up indication - but maybe I'm not thinking about it correctly. Thanks. Incidentally, regarding the alternative explanations, my plane is a 1966 era Libelle H301. The loss of flourescent paint seems possible on a 40 year old plane, but I'm surprised to find the effect so marked in just one year out of 40. Alan 'HL Falbaum' wrote in message news Mine--(57mm) reads zero on the ground, but about 2 kt high in the air, compared to a S-Nav. Yes I understand the 'relative netto' thing, but this occurs while thermaling at 48-52 kt in a DG800B, with the pneumatic switch on 'TE probe'. In addition, the Winter is faster in response than the S-Nav with the Cambridge set on 'fast' (1 sec). The DG factory installation has very short leads off a 'Y' to the S-Nav and Winter, but they are on separate flasks--both 0.45l, with fairly long leads. I'm guessing a very small leak in the Winter. I have just removed it and will test tomorrow. I thought it was just me! -- Hartley Falbaum 'Alan Meyer' wrote in message ... Last year my Winter mechanical variometer may have read a bit high, but not very much. Today however, on my first flight of the year, the vario appeared to read 400 feet high in the air and about 75 feet high on the ground. With the vario reading 400 feet per minute up, the altimiter wasn't doing anything and the Cambridge electric vario was reading zero sink. I've searched the r.a.s. archives and found the advice about zeroing the needle using the adjustment under the faceplate and putting a trace of nail polish on the needle to weigh it down. Do these seem like appropriate repairs for this problem? Can anyone speculate on why the vario might read so much higher in the air than on the ground? Is there a plumbing problem I should look for to explain this? Thanks for any ideas. Alan |
#6
|
|||
|
|||
Winter mechanical vario reading high
Cause is leak on the capacitiy side of the vario.
If you have the varios in series, the likely cause will bea leak on the sensor board of the Cambridge. Otherwise, just replace the tubing between the capacity and the Winter- it's probably hard as a rock. Good Luck UH |
#7
|
|||
|
|||
Winter mechanical vario reading high
Found it!
The vinyl tubing is 8+ years old, and leaking at both ends of the flask tube. The fit looked only slightly less than tight. The tube was not hard as a rock but firmer than new tubing. The S-Nav and Winter are paralllel, not series. Cutting off the vario end of the tube reduced, but did not eliminate the leak. Then cutting off the flask end eliminated the rest of the leak. Testing the vario alone proved it was leak free. Thanks UH. - Hartley Falbaum "KF" wrote in message oups.com... Cause is leak on the capacitiy side of the vario. If you have the varios in series, the likely cause will bea leak on the sensor board of the Cambridge. Otherwise, just replace the tubing between the capacity and the Winter- it's probably hard as a rock. Good Luck UH |
#8
|
|||
|
|||
Winter mechanical vario reading high
The TE head generates a low pressure at the sensor holes on the back of the
tube, so that if there is a leak in the system on the flask side of the Winter vario, then it appears to me that the TE pressure will draw air out even whilst the glider is holding a steady height. Hence, Winter vario reads up. Change tubing downstream of the vario and change the flask for one you have confidence is leak free - best is a replacement flask of the same kind. Fly the glider again. If the problem persists this may suggest the leak is with the Winter vario. Flasks can have leaks and tubing can fracture or be old and not sealing at the barbs on the vario or flask connections. The ground problem is either due to needle out of balance or needle zero setting error I would suggest. These are actually two seperate problems. I suggest that the adjustment under the faceplate is provided to adjust the zero needle position as controlled by zeroing springs and after the needle is balanced. The problem is usually a needle balance problem. Fix a balance problem by use of paint on the needle. See my posting at the end of the thread on this topic which appeared starting 27 March 2006. For completeness I will repeat he The factors a 1. The state of balance of the needle about the pivot - as affected by the balance state of the needle. 2. The influence of zero setting springs - as affected by the serated ring exposed under the little cover at the vario face centre (as with Winter varios). When we find that the vario at rest has the needle away from zero (with Winter variometers usually 0.5 to 1 kt up due loss of solvents from the white paint, and with PZL ofen down due ?? to luminescent paint absoring and holding moisture??), what result do we want from our efforts to correct it? I would suggest we want the outcome to be that the vario needle at rest sits at zero both with the vario in both upright and inverted (ie rolled 180 degrees about the needle shaft axis) positions. At rest hold the vario upright and note the needle position, and then hold it inverted and note the needle position. From that information you can get an idea as to whether it is a problem of needle balance (1 above) or zero setting (2 above), or a mix of the two. For example a needle out of balance of + 1 knot upright will show -1 knot with vario inverted. Mostly it is a matter of 1 above. In the case of 1, fixing it by using the zero setting springs via the serated ring will zero the needle with variometer upright but not inverted! If it is a needle balance problem then you need to fix the needle balance, not alter the zeroing springs. If you fix the needle balance, then the needle will not respond to accelerations during pullups, gusts, etc which is a better outcome. I use paint placed close to the needle pivot because so little is needed to produce balance. I use a broken hacksaw blade ground to length (and using the plain edge not the serrated edge) to engage the ring and facilitate its removal and reinstallation. Rather than fit the blade element to a piece of timber to create a tool, I put the blade element in a bench vise and hold the vario down onto the blade element. Then you get precise control of the undoing and particularly the doing up force/torque. Don't give the job to your local club member-gorrilla! I welcome any contribution to improving the understanding presented above. Cheers Roger Druce "Alan Meyer" wrote in message ... Last year my Winter mechanical variometer may have read a bit high, but not very much. Today however, on my first flight of the year, the vario appeared to read 400 feet high in the air and about 75 feet high on the ground. With the vario reading 400 feet per minute up, the altimiter wasn't doing anything and the Cambridge electric vario was reading zero sink. I've searched the r.a.s. archives and found the advice about zeroing the needle using the adjustment under the faceplate and putting a trace of nail polish on the needle to weigh it down. Do these seem like appropriate repairs for this problem? Can anyone speculate on why the vario might read so much higher in the air than on the ground? Is there a plumbing problem I should look for to explain this? Thanks for any ideas. Alan |
#9
|
|||
|
|||
Winter mechanical vario reading high
Roger Druce wrote: The TE head generates a low pressure at the sensor holes on the back of the tube, so that if there is a leak in the system on the flask side of the Winter vario, then it appears to me that the TE pressure will draw air out even whilst the glider is holding a steady height. Hence, Winter vario reads up. Change tubing downstream of the vario and change the flask for one you have confidence is leak free - best is a replacement flask of the same kind. Fly the glider again. If the problem persists this may suggest the leak is with the Winter vario. Flasks can have leaks and tubing can fracture or be old and not sealing at the barbs on the vario or flask connections. The ground problem is either due to needle out of balance or needle zero setting error I would suggest. These are actually two seperate problems. I suggest that the adjustment under the faceplate is provided to adjust the zero needle position as controlled by zeroing springs and after the needle is balanced. The problem is usually a needle balance problem. Fix a balance problem by use of paint on the needle. See my posting at the end of the thread on this topic which appeared starting 27 March 2006. For completeness I will repeat he The factors a 1. The state of balance of the needle about the pivot - as affected by the balance state of the needle. 2. The influence of zero setting springs - as affected by the serated ring exposed under the little cover at the vario face centre (as with Winter varios). When we find that the vario at rest has the needle away from zero (with Winter variometers usually 0.5 to 1 kt up due loss of solvents from the white paint, and with PZL ofen down due ?? to luminescent paint absoring and holding moisture??), what result do we want from our efforts to correct it? I would suggest we want the outcome to be that the vario needle at rest sits at zero both with the vario in both upright and inverted (ie rolled 180 degrees about the needle shaft axis) positions. At rest hold the vario upright and note the needle position, and then hold it inverted and note the needle position. From that information you can get an idea as to whether it is a problem of needle balance (1 above) or zero setting (2 above), or a mix of the two. For example a needle out of balance of + 1 knot upright will show -1 knot with vario inverted. Mostly it is a matter of 1 above. In the case of 1, fixing it by using the zero setting springs via the serated ring will zero the needle with variometer upright but not inverted! If it is a needle balance problem then you need to fix the needle balance, not alter the zeroing springs. If you fix the needle balance, then the needle will not respond to accelerations during pullups, gusts, etc which is a better outcome. I use paint placed close to the needle pivot because so little is needed to produce balance. I use a broken hacksaw blade ground to length (and using the plain edge not the serrated edge) to engage the ring and facilitate its removal and reinstallation. Rather than fit the blade element to a piece of timber to create a tool, I put the blade element in a bench vise and hold the vario down onto the blade element. Then you get precise control of the undoing and particularly the doing up force/torque. Don't give the job to your local club member-gorrilla! I welcome any contribution to improving the understanding presented above. Cheers Roger Druce "Alan Meyer" wrote in message ... Last year my Winter mechanical variometer may have read a bit high, but not very much. Today however, on my first flight of the year, the vario appeared to read 400 feet high in the air and about 75 feet high on the ground. With the vario reading 400 feet per minute up, the altimiter wasn't doing anything and the Cambridge electric vario was reading zero sink. I've searched the r.a.s. archives and found the advice about zeroing the needle using the adjustment under the faceplate and putting a trace of nail polish on the needle to weigh it down. Do these seem like appropriate repairs for this problem? Can anyone speculate on why the vario might read so much higher in the air than on the ground? Is there a plumbing problem I should look for to explain this? Thanks for any ideas. Alan Hi About 5 years ago I sent my vario and airspeed to Winter. Everything came back as new. Cost about $100 for each instrument including shipping. Best deal IMO. December is probably the best time of year to use this solution S6 |
#10
|
|||
|
|||
Winter mechanical vario reading high
Hi,
You are assuming the identified problem is real. It could be something else. You are using this problem so you can use the solution you have. Adding paint is just convenient. Send it to Winter. S6 |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
I want to build the most EVIL plane EVER !!! | Eliot Coweye | Home Built | 237 | February 13th 06 03:55 AM |
Most reliable homebuilt helicopter? | tom pettit | Home Built | 35 | September 29th 05 02:24 PM |
Mini-500 Accident Analysis | Dennis Fetters | Rotorcraft | 16 | September 3rd 05 11:35 AM |
high copper reading in oil analysis | [email protected] | Owning | 1 | March 26th 04 03:32 PM |
Vario time constants | Bill Daniels | Soaring | 3 | January 20th 04 03:18 PM |