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Wet Vacuum Pumps: Reliable, Durable

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, its 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.

Aviation Consumer Staff
Verified

In fr

ee 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, its 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

Wet Vaccum Pump

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 aint 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 its 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 theyre 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 its 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 wouldnt 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. Its 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

Aviation Consumer Staff