Interesting story for anyone who flies IFR in a single!
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This video reviews both dry and wet vacuum pumps. It may be of some interest.
M
http://www.youtube.com/watch?v=pJC0SScgQyw
M
http://www.youtube.com/watch?v=pJC0SScgQyw
Grandpa Aerotart
This article in the latest Aviation Consumer is interesting...and is what led me to see what kind of vac pump is installed in my Bonanza.
In free markets—or so the theory goes—good products rise to the top like cream and bad products are weeded out and tossed aside to wither and die. In the real world, it’s messier than that, thus we have VHS instead of BetaMax, PCs dominate Macs and the overwhelming majority of airplanes have failure-prone dry vacuum pumps instead of bulletproof wet pumps. What happened here? The precise details seem to be lost to the sands of time but the short version is this: Dry pumps appeared in the mid-1960s, they were substantially cheaper than wet pumps and by the time owners realized how unreliable dry pumps were, the aircraft manufacturers had established them as the defacto standard. And because the OEMs could get away with that, the two wet pump manufacturers—Pesco and Garwin—got out of the wet pump business and eventually disappeared entirely.
In the interim, owners who have always preferred wet pumps over dry pumps have simply retained them, finding shops to overhaul them or in many cases, just letting them perk merrily along without so much as a friendly swipe from a 9/16th-inch wrench. That sort of thing gives some mechanics the willies, but vacuum is vacuum and owners are understandably reluctant to fix what ain’t busted. As far as we know, there’s only one manufacturer of new wet pumps, the Airwolf Filter Corp., an Ohio-based company best known for add-on aircraft oil filter systems and, lately, wet vacuum pumps. At least one company we know of, Airpower, overhauls Pesco and Garwin pumps and markets these through Aircraft Spruce and Specialty. A third company, M-20 Turbos, made a run at the wet pump market with overhauls and a proposed new wet pump, but the company informed us recently that it’s no longer in the pump business.
Buy Or Not?
The economic ascendancy of dry pumps complicates the wet-pump purchase decision for most owners. Diehard owners of wet pumps tell us they’re not interested in converting to dry pumps. But having suffered through multiple failures, many owners of dry pumps are contemplating a walk on the wet side. But it’s not so simple. Any airplanes manufactured after the demise of wet pumps—early to mid-1960s—are usually approved only for dry pumps, so even though a wet design will bolt to the same accessory pad, the installation wouldn’t be legal without an STC. For any owners interested in converting, Airwolf has a long approved model list (AML) for virtually everything flying. As attractive as wet pumps are and even though Airwolf makes the conversion process easy, we suspect many owners pass on wet pumps because of the hassle and cost. It’s just easier to buy a rebuilt Rapco or a Tempest, bolt it on and go flying. At $1599, the Airwolf pump is nearly six times more expensive than the price-leader Rapco overhauls and more than four times as much as top-of-the-line Tempest dry pumps. Moreover, dedicated air/oil
Airwolf’s pump is an improved derivative of the original Pesco, found in thousands of light aircraft.
Separators for the wet pump are must-have equipment and if you don’t have one installed, plan on another $400. Bottom line: Budget $2200 to $2400 to convert from a dry pump to a wet pump. But realistically, wet pumps appear to be so reliable and durable that most owners may never have to replace or even overhaul one. Airwolf, for example, offers a generous 2000-hour/10-year warranty.
How They Work
Wet pumps have such a superior service reputation over dry pumps that you’d assume that they’re radically different in design. In fact, they aren’t. And a better description of a wet pump may be "oil misted" rather than wet, since they are anything but submerged in oil.
As shown in the photos at left, wet pumps and dry pumps share a fundamental design similarity. Both pump or compress air by spinning blades or vanes inside a sealed bore. Both types also use graphite for the vanes, but at this juncture, the two designs diverge.
A wet pump’s vanes are three times thicker than those found in the typical dry pump and they’re composed of a softer graphite. While the dry pump’s vanes bear and seal against a polished bore inside the pump, they run dry, relying on powdered graphite from the wear process for lubrication.
Wet pumps, on the other hand, are lubricated by a light misting of oil metered into the pump through accessory case inlets. In addition to lubing the vane-to-bore contact surface, the light oil film also seals better, which improves pumping efficiency. In the Airwolf pump, the vanes seal against a cast iron insert, a material that naturally contains embedded graphite, further reducing friction.
In part, this is why wet pumps are more durable. But there’s more to the story. Wet pumps are more robustly made than are dry pumps, which accounts for their higher prices. Note that the Airwolf pump has a heavy, precision machined rotor which rotates on a pair of ball bearings, one sealed and one constanly lubricated by engine oil.
Airwolf Pump
Airwolf sent us two pumps for trials, one of which arrived disassembled so we could examine its innards. We were impressed with the overhaul quality of the machine work on this product. The pump body is machined from a single billet of 6061 aluminum and nicely anodized a striking gold color. The body, end cap and sleeve seem to be similarly well machined for perfect fits.
Airwolf’s John Kochy told us the company’s pump is a direct descendent of the original Pesco pump, whose plant was in Bedford, Ohio, near Airwolf’s Middlefield, Ohio headquarters. He makes no claims about reinventing the wheel.
"Our specialty is not inventing something from scratch, "Kochy told us, "but making something better." Those improvements include the billet body rather the original cast aluminum, plus a handful of minor proprietary changes Kochy declines to reveal. He explains that the largest challenge in building a wet pump—which drives cost upward—is the requirement to hold exceptionally tight mechanical tolerances. For example, all of the clearances in the pump are in the 0.0001 to 0.0003 inch range. "It would be a lot easier if we could open those tolerances up, but if we do, we lose performance." (This leads us to wonder how efficient overhauled pumps are compared to Airwolf’s new models, but the company doing the overhauls didn’t respond to our queries.)
Trying It
From our previous test of pumps, we know that all of the dry pumps and Sigma-Tek’s new Aeon piston pump deliver adequate vacuum through the entire RPM range, although their output falls off at idle speed. (See Aviation Consumer April 2007 for the full report.) We wondered how the wet pump would compare.
The Airwolf clearly moves more air than the dry pumps do, probably due to the oily seal between the vane bearing surfaces and the inner bore of the pump. As the lowest possible idle our pump motor could deliver—about 600 RPM—and lower than the typical engine would be idled, the pump was easily delivering 3 CFM at over 5 inches of mercury. At these low RPMs, dry vane pumps typically deliver marginal vacuum, although the Aeon pump did better. We weren’t surprised that the Airwolf pump was working harder to deliver more vacuum. Our DC test motor drew 9.9 amps when running the dry pump, but nearly 25 amps when the Airwolf pump was running. Apart from high cost, one glaring weakness of wet pumps is their reputation for spewing oil, which finds its way onto the belly of the airplane. The OEMs used this as a selling point in the conversion from wet to dry pumps. And while it’s true wet pumps are messier than dry pumps, we think the argument is overstated. In running the wet pump on our test stand, we placed a sheet of clean white paper in front of the exhaust vent and collected a barely detectable misting of oil. The exhaust smells warm and oily, but it’s hardly spewing oil. (Admitedly, it might exhaust more if the pump were being oiled by engine oil.) Airwolf’s Kochy told us the pump consumes less than 3 cc’s of oil every 10 minutes, which equates to 0.02 quart per hour. That may vary with installation—some owners do complain about an excessively oily belly—but a properly installed air/oil separator catches most of the oil. Just know this: A small number of owners still report serious oil issues.
Conclusion
We have no reservation in saying that a wet vacuum pump is right for every airplane—it’s just better technology than the dry pump. But it’s not right for every owner, chiefly because of cost. We think an owner who flies a Cessna 172 or a Piper 180 50 hours a year and never ventures into IMC is better off retaining a dry pump and replacing it as necessary with an overhauled Rapco pump, the value leader in dry pumps.
But for hardcore IFR pilots or those who worry about dry pump failures—and it’s a question of when, not if, a dry pump will fail—a wet pump is as close to a lifetime component as any of us are likely to get. Backing up instruments is always a risk tradeoff. The belt-and -suspender approach is costly and not always necessary for owners on a budget. We think wet pumps are reliable enough to install in lieu of any other kind of backup, such as electric gyros or electrically driven backup vacuum pumps.
In the interim, owners who have always preferred wet pumps over dry pumps have simply retained them, finding shops to overhaul them or in many cases, just letting them perk merrily along without so much as a friendly swipe from a 9/16th-inch wrench. That sort of thing gives some mechanics the willies, but vacuum is vacuum and owners are understandably reluctant to fix what ain’t busted. As far as we know, there’s only one manufacturer of new wet pumps, the Airwolf Filter Corp., an Ohio-based company best known for add-on aircraft oil filter systems and, lately, wet vacuum pumps. At least one company we know of, Airpower, overhauls Pesco and Garwin pumps and markets these through Aircraft Spruce and Specialty. A third company, M-20 Turbos, made a run at the wet pump market with overhauls and a proposed new wet pump, but the company informed us recently that it’s no longer in the pump business.
Buy Or Not?
The economic ascendancy of dry pumps complicates the wet-pump purchase decision for most owners. Diehard owners of wet pumps tell us they’re not interested in converting to dry pumps. But having suffered through multiple failures, many owners of dry pumps are contemplating a walk on the wet side. But it’s not so simple. Any airplanes manufactured after the demise of wet pumps—early to mid-1960s—are usually approved only for dry pumps, so even though a wet design will bolt to the same accessory pad, the installation wouldn’t be legal without an STC. For any owners interested in converting, Airwolf has a long approved model list (AML) for virtually everything flying. As attractive as wet pumps are and even though Airwolf makes the conversion process easy, we suspect many owners pass on wet pumps because of the hassle and cost. It’s just easier to buy a rebuilt Rapco or a Tempest, bolt it on and go flying. At $1599, the Airwolf pump is nearly six times more expensive than the price-leader Rapco overhauls and more than four times as much as top-of-the-line Tempest dry pumps. Moreover, dedicated air/oil
Airwolf’s pump is an improved derivative of the original Pesco, found in thousands of light aircraft.
Separators for the wet pump are must-have equipment and if you don’t have one installed, plan on another $400. Bottom line: Budget $2200 to $2400 to convert from a dry pump to a wet pump. But realistically, wet pumps appear to be so reliable and durable that most owners may never have to replace or even overhaul one. Airwolf, for example, offers a generous 2000-hour/10-year warranty.
How They Work
Wet pumps have such a superior service reputation over dry pumps that you’d assume that they’re radically different in design. In fact, they aren’t. And a better description of a wet pump may be "oil misted" rather than wet, since they are anything but submerged in oil.
As shown in the photos at left, wet pumps and dry pumps share a fundamental design similarity. Both pump or compress air by spinning blades or vanes inside a sealed bore. Both types also use graphite for the vanes, but at this juncture, the two designs diverge.
A wet pump’s vanes are three times thicker than those found in the typical dry pump and they’re composed of a softer graphite. While the dry pump’s vanes bear and seal against a polished bore inside the pump, they run dry, relying on powdered graphite from the wear process for lubrication.
Wet pumps, on the other hand, are lubricated by a light misting of oil metered into the pump through accessory case inlets. In addition to lubing the vane-to-bore contact surface, the light oil film also seals better, which improves pumping efficiency. In the Airwolf pump, the vanes seal against a cast iron insert, a material that naturally contains embedded graphite, further reducing friction.
In part, this is why wet pumps are more durable. But there’s more to the story. Wet pumps are more robustly made than are dry pumps, which accounts for their higher prices. Note that the Airwolf pump has a heavy, precision machined rotor which rotates on a pair of ball bearings, one sealed and one constanly lubricated by engine oil.
Airwolf Pump
Airwolf sent us two pumps for trials, one of which arrived disassembled so we could examine its innards. We were impressed with the overhaul quality of the machine work on this product. The pump body is machined from a single billet of 6061 aluminum and nicely anodized a striking gold color. The body, end cap and sleeve seem to be similarly well machined for perfect fits.
Airwolf’s John Kochy told us the company’s pump is a direct descendent of the original Pesco pump, whose plant was in Bedford, Ohio, near Airwolf’s Middlefield, Ohio headquarters. He makes no claims about reinventing the wheel.
"Our specialty is not inventing something from scratch, "Kochy told us, "but making something better." Those improvements include the billet body rather the original cast aluminum, plus a handful of minor proprietary changes Kochy declines to reveal. He explains that the largest challenge in building a wet pump—which drives cost upward—is the requirement to hold exceptionally tight mechanical tolerances. For example, all of the clearances in the pump are in the 0.0001 to 0.0003 inch range. "It would be a lot easier if we could open those tolerances up, but if we do, we lose performance." (This leads us to wonder how efficient overhauled pumps are compared to Airwolf’s new models, but the company doing the overhauls didn’t respond to our queries.)
Trying It
From our previous test of pumps, we know that all of the dry pumps and Sigma-Tek’s new Aeon piston pump deliver adequate vacuum through the entire RPM range, although their output falls off at idle speed. (See Aviation Consumer April 2007 for the full report.) We wondered how the wet pump would compare.
The Airwolf clearly moves more air than the dry pumps do, probably due to the oily seal between the vane bearing surfaces and the inner bore of the pump. As the lowest possible idle our pump motor could deliver—about 600 RPM—and lower than the typical engine would be idled, the pump was easily delivering 3 CFM at over 5 inches of mercury. At these low RPMs, dry vane pumps typically deliver marginal vacuum, although the Aeon pump did better. We weren’t surprised that the Airwolf pump was working harder to deliver more vacuum. Our DC test motor drew 9.9 amps when running the dry pump, but nearly 25 amps when the Airwolf pump was running. Apart from high cost, one glaring weakness of wet pumps is their reputation for spewing oil, which finds its way onto the belly of the airplane. The OEMs used this as a selling point in the conversion from wet to dry pumps. And while it’s true wet pumps are messier than dry pumps, we think the argument is overstated. In running the wet pump on our test stand, we placed a sheet of clean white paper in front of the exhaust vent and collected a barely detectable misting of oil. The exhaust smells warm and oily, but it’s hardly spewing oil. (Admitedly, it might exhaust more if the pump were being oiled by engine oil.) Airwolf’s Kochy told us the pump consumes less than 3 cc’s of oil every 10 minutes, which equates to 0.02 quart per hour. That may vary with installation—some owners do complain about an excessively oily belly—but a properly installed air/oil separator catches most of the oil. Just know this: A small number of owners still report serious oil issues.
Conclusion
We have no reservation in saying that a wet vacuum pump is right for every airplane—it’s just better technology than the dry pump. But it’s not right for every owner, chiefly because of cost. We think an owner who flies a Cessna 172 or a Piper 180 50 hours a year and never ventures into IMC is better off retaining a dry pump and replacing it as necessary with an overhauled Rapco pump, the value leader in dry pumps.
But for hardcore IFR pilots or those who worry about dry pump failures—and it’s a question of when, not if, a dry pump will fail—a wet pump is as close to a lifetime component as any of us are likely to get. Backing up instruments is always a risk tradeoff. The belt-and -suspender approach is costly and not always necessary for owners on a budget. We think wet pumps are reliable enough to install in lieu of any other kind of backup, such as electric gyros or electrically driven backup vacuum pumps.
Watched a wealthy businessman pilot practicing IFR in an Elite Synthetic Trainer. He flew beaut ILS's and wonderful holding patterns on the autopilot. Even his hand flying with a flight director was spot on. After all, isn't that what a flight director is for - to make instrument flying easier because there are less instruments to scan? It was suggested to him perhaps he should also practice hand-flying on limited panel - in other words no artificial horizon. He disagreed saying his aircraft (a new sophisticated single) never needed such manoeuvres.
A few minutes later an instructor quietly failed the artifical horizon without the pilot being aware of anything gone wrong. It took less than 45 seconds for the graveyard spiral to occur and the bloke didn't have a clue what was going on - nor how to recover on instruments. He was more pissed off with the instructor for failing the AH than with himself for his lack of skills.
Moral of the story? If you can afford the money to practice instrument flying on a synthetic trainer, make sure the money is well spent by improving your skills on limited panel flying. One dark night you may need to use those skills to save your life.
A few minutes later an instructor quietly failed the artifical horizon without the pilot being aware of anything gone wrong. It took less than 45 seconds for the graveyard spiral to occur and the bloke didn't have a clue what was going on - nor how to recover on instruments. He was more pissed off with the instructor for failing the AH than with himself for his lack of skills.
Moral of the story? If you can afford the money to practice instrument flying on a synthetic trainer, make sure the money is well spent by improving your skills on limited panel flying. One dark night you may need to use those skills to save your life.
Thread Starter
Good one Chuck!
We can always rely on you to have ALL the info!
Centaurus - I'll second that! However, if you can afford to own and operate a new sophisticated aeroplane, why bother with a simulator (unless its full motion). Go fly the aeroplane. My Instructor/ATO really works me over!
Dr
We can always rely on you to have ALL the info!
Centaurus - I'll second that! However, if you can afford to own and operate a new sophisticated aeroplane, why bother with a simulator (unless its full motion). Go fly the aeroplane. My Instructor/ATO really works me over!
Dr
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One option that has not been presented is installing a standby electric vac pump. One aircraft in our fleet has one and it is a great thing to have for peace of mind. Activated by a flick switch and hey presto - vac restored. Every so often we give it a run for internal lubrication even while the engine driven pump is operating (will boost the suction reading a bit when on line - also audibly a bit noisy). I think for a SE IFR aircraft it is money well spent. In FTDK's case when your engine pump desides to quit at least you have an instant backup which will at least get you out of trouble until you get home for maintenance! 
Thread Starter
Capt - for the same money (from my enquiries) you can install a wet vac pump and pretty much eliminate the issue. I have a lecky AH so I already have instant backup.
Has anyone tried simulated IFR on the flight instrument display on a Garmin GPSMap 296?
Dr
Has anyone tried simulated IFR on the flight instrument display on a Garmin GPSMap 296?
Dr
Thread Starter
'Since the 1970s, when cheaper dry pumps were introduced, they have been made with thin, brittle carbon vanes which usually break before 500 hours. Dirt in the line, solvents, water, reverse propeller rotation from backfiring or even backing the prop by hand - all can cause catastrophic disintegration of the vanes.'
Did you know this?
I didn't until told by a LAME a couple of years ago!
Dr
Did you know this?
I didn't until told by a LAME a couple of years ago!
Dr
When you live....
Standby VAC pump
Great in theory but my only experience with a loss of primary instruments was the AH itself dying and the standby VAC pump didn't do anything to contribute to the situation.
On the downside, it was my first IFR trip after being let loose with a rating.
On the plus-side, I'd emerged from the clouds less than 30 seconds earlier.
UTR
On the downside, it was my first IFR trip after being let loose with a rating.
On the plus-side, I'd emerged from the clouds less than 30 seconds earlier.
UTR
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FTDK and others, how often should you change a standard vac pump - IFR or otherwise?
No so long back I bought an IFR single with a vac pump that had over 1200 hours on it, working perfectly, with both the owner and his LAME saying it was pefectly safe and legal. I changed it. Some LAME's seem to say if its working its OK, others say 500hrs no matter what, others say 500 hours unless its the Tempest type and you can check its not worn beyond limits.
Another of my aircraft had a stanby electric vac pump - probably only ever ran for about half an hour. One Australian Cessna dealer said both vac pumps were fine and signed out a new 100 hrly. Another (whom I had the misfortune to 'visit' immediately after same 100hrly) said the aircraft was illegally maintained and both must be changed immediately because they could find no record of either being changed during the last 500hours.
Yeah yeah yeah, it depends, its a matter of interpretation, its whether you are working to Shed 5 or manufacturers scheme etc etc - so who knows?
On related matter, I now have an aircraft with one of those standby vac thingys that works on manifold pressure. It seems to work quite well, but are they any good when the real thing happens and will George keep going?
No so long back I bought an IFR single with a vac pump that had over 1200 hours on it, working perfectly, with both the owner and his LAME saying it was pefectly safe and legal. I changed it. Some LAME's seem to say if its working its OK, others say 500hrs no matter what, others say 500 hours unless its the Tempest type and you can check its not worn beyond limits.
Another of my aircraft had a stanby electric vac pump - probably only ever ran for about half an hour. One Australian Cessna dealer said both vac pumps were fine and signed out a new 100 hrly. Another (whom I had the misfortune to 'visit' immediately after same 100hrly) said the aircraft was illegally maintained and both must be changed immediately because they could find no record of either being changed during the last 500hours.
Yeah yeah yeah, it depends, its a matter of interpretation, its whether you are working to Shed 5 or manufacturers scheme etc etc - so who knows?
On related matter, I now have an aircraft with one of those standby vac thingys that works on manifold pressure. It seems to work quite well, but are they any good when the real thing happens and will George keep going?
Thread Starter
Dunno Wheeler!
Maybe there is a LAME sticks his head in here can shed some light on it. I have had the FTDK for close on 500 hrs and it hasn't come up so far. My LAME is a stickler for "by the book".
But I got a new one today !!!!!!!
You gotta love VFR. Sitting round YATN waiting for the fog to lift. Can't get over the cloud without going into IMC so spiral down through a hole north of Tully and down the Hinchinbrook Channel at 800' with the terrain alert in the GNS430 going ga ga!
Dr
Maybe there is a LAME sticks his head in here can shed some light on it. I have had the FTDK for close on 500 hrs and it hasn't come up so far. My LAME is a stickler for "by the book".
But I got a new one today !!!!!!!
You gotta love VFR. Sitting round YATN waiting for the fog to lift. Can't get over the cloud without going into IMC so spiral down through a hole north of Tully and down the Hinchinbrook Channel at 800' with the terrain alert in the GNS430 going ga ga!
Dr
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'backing the prop by hand...can cause catastrophic disintegration of the vanes.' -I back the prop(s) by hand every pre-flight (to check the blades), never had a vac pump fail on me since I was a student pilot.
Maybe good luck rather than good management, but I reckon this one can be added to the huge list of Old Wives Tales that pervades aviation.
Btw, there's two mounting pads on the back of the donk, why not put on TWO cheap and nasty vac pumps? (Oh no! Twice the chance of a pump failure!)
Maybe good luck rather than good management, but I reckon this one can be added to the huge list of Old Wives Tales that pervades aviation.
Btw, there's two mounting pads on the back of the donk, why not put on TWO cheap and nasty vac pumps? (Oh no! Twice the chance of a pump failure!)
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FTDK - sounds like you had fun! Those times are hard to beat.
I dunno either. I believe there was case a few years back of a crash where the cause was deemed to be vac pump failure(?). Case was lost because it was found that the component had not been changed according to manufacturer's recommendations. Maybe its perfectly OK not to change a vac pump - unless you crash? - Just shows how rediculous our regulator can be?
I dunno either. I believe there was case a few years back of a crash where the cause was deemed to be vac pump failure(?). Case was lost because it was found that the component had not been changed according to manufacturer's recommendations. Maybe its perfectly OK not to change a vac pump - unless you crash? - Just shows how rediculous our regulator can be?
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"Has anyone tried simulated IFR on the flight instrument display on a Garmin GPSMap 296?"
Hey forky have a look at the US Flying magazine website (www.flyingmag.com), Richard L Collins has written an article about using a 2/3/496 garmin for last ditch back up. It makes for interesting reading, he seems to be of the opinion that it isn't that useful unless you had made an effort to practice it and even then the update rates (1sec or so) made keeping the wings level quite a task with reacting to longer trends being the only option. I think it is in the latest edition but you may have to have to do a bit of a search for it.
The Comet
Hey forky have a look at the US Flying magazine website (www.flyingmag.com), Richard L Collins has written an article about using a 2/3/496 garmin for last ditch back up. It makes for interesting reading, he seems to be of the opinion that it isn't that useful unless you had made an effort to practice it and even then the update rates (1sec or so) made keeping the wings level quite a task with reacting to longer trends being the only option. I think it is in the latest edition but you may have to have to do a bit of a search for it.
The Comet
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Wet Pumps
MJH/Chimbu - fantastic info... those guys at Aviation Consumer do a brilliant job.
A couple of things though - Just looked at Spruce/Chief etc and the cost of the Airwolf is about US$1600. I guess if your plane is certified with a dry pump you would need an STC and they seem to be a fairly substantial piece of kit so guess they would weigh a bit more and maybe need to ajdust the w and b schedule a little? Wet pumps would obviously be a much better option and with 2000hour 10 year life virtually eliminate the worry of those crappy dry pumps - but which are only about A$350. You could get a few dry pumps change them at recommended 500 hours and still be better off (financially), which is probably why the manufacturers changed to them in the first place.
A couple of things though - Just looked at Spruce/Chief etc and the cost of the Airwolf is about US$1600. I guess if your plane is certified with a dry pump you would need an STC and they seem to be a fairly substantial piece of kit so guess they would weigh a bit more and maybe need to ajdust the w and b schedule a little? Wet pumps would obviously be a much better option and with 2000hour 10 year life virtually eliminate the worry of those crappy dry pumps - but which are only about A$350. You could get a few dry pumps change them at recommended 500 hours and still be better off (financially), which is probably why the manufacturers changed to them in the first place.
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FTDK - Service letter Number 66 from Parker Airbourne dated 31 Jan 07 model numbers 211 to 216, 241, 242, 441, 442 which are more commonly fitted to Bonanzas. The pumps are stickered by Parker as not to be overhauled but companies such as RAPCO have been overhauling them and putting them back into the market. Organisation recommended Tempest ($500, manufacturer says 1000 hour life) as a dry pump, but wet as being the best of the best.
but I reckon this one can be added to the huge list of Old Wives Tales that pervades aviation.
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Forkie.......Gotta luv VFR
I do, and when faced with a heap of time over the top, I turned around and went coastal......got me five hours in a FTDK!......where is the downside there?
Nothing like flying at FL-Tree Tops occasionally!
J
I do, and when faced with a heap of time over the top, I turned around and went coastal......got me five hours in a FTDK!......where is the downside there?
Nothing like flying at FL-Tree Tops occasionally!
J