Ovation Standby Vacuum Pump

[Greg_D]

The standby vacuum pump in my Ovations's tail cone isn't working.  The motor spins, but the pump must have crapped out.  The parts manual calls for a 212CW pump, but the installed unit is a Sigmatek 1U128 unit.  I don't think the Sigmateks can be rebuilt.  They are also $599 new.  Does anyone see an issue with replacing the Sigmatek with a much less expensive 212CW unit?

[Piloto]

Before replacing the pump verify that the transfer valve is switching to the aux. pump. If you have a vacuum cleaner at hand disconnect the aux. pump inlet line from the pump and connect to it the vacuum cleaner. Turn on the vac. cleaner and the aux. vacuum switch to see if you get any vacuum reading. If you do not get any vacuum indication suspect the transfer valve or the vac. line.

 

Jose 

[N601RX]

It may have just sheared the plastic drive coupling between the motor and pump

[Greg_D]

Well today, the engine driven pump went out too.  That one was because of a sheared plastic coupling.  I'll try the vacuum cleaner on the aux pump inlet and see what I get.  The aux pump looks like it's turning, but there doesn't seem to be any suction at the pump opening.

[Guest]

Greg,

Can you see if the drive shaft of the standby pump is turning? If memory is still good the pump is driven by a 1/8" stainless shaft.

There are several a small set screws on the coupling between the motor and the pump, they do come loose.

In some installations the pump discharge is used to cool the electric motor. Turn it on and feel for air blowing through the motor. This would confirm pump operation.

I think that the Sigma tek pump is bi directional, likely why someone installed it.

Sounds like you're buying at least one pump.

Clarence

[Greg_D]

I took the standby pump out of the plane to take a look today.  Someone had assembled the pump using silicone as a sealant.  The pump would spin, but was extremely difficult to turn by hand.  I took the end off the pump and found that the silicone had worked it's way into the pump chamber, causing the pump vanes to bind in their slots in the rotor.  I ordered a new 212CW pump today.  I sure am glad I found this while on the ground!

[jetdriven]

We saw this last month on an O2.  Someone installed a new pump in the standby and used grease to get the nipple in the hose. This grease made its way into the vacuum pump and ruined it. It only ran a half hour at most.

[Guest]

More examples of excellent work!!

Clarence

[carusoam]

How many hours get collected by the back-up?

I test it, turn it off, wait for another day, repeat... An hour or two per year.

Best regards,

-a-

[Greg_D]

The pump was installed about 10 years ago.  It was a replacement for the original engine mounted backup.  I'm not sure about the previous owner, but I test ran it for a minute or so on every flight where IMC was a consideration.  It ran for about an hour continuously after the primary pump failed.  I was worried that the goo would make its way into the motor since the exhaust on the pump discharges into the electric motor for cooling. We didn't see any indication of the mess in the discharge fitting, so I think I'm OK.

 

Interestingly, the little book that came with the backup pump says to always leave it running.  I've never done that.  I guess they want to sell more pumps.