vacuum pumps

[Bob Cook]

Not much as been said about vacuum pumps.

I lost ANOTHER vacuum pump deploying the boots last weekend... just when you need them the most!

Seem to lose them under 500 hrs (replaced 3 in last two years).

Any recommendations on mfgr? rebuilt vrs new? Anyone have same problem?

Bob

[Kevin B]

Bob try this might work for you
Kevin B
SNF's Most Significant: Aero Advantage Dual Vacuum Pump
We often write about interesting items we've come across at shows. We also will bring you many more really cool things, found at the show; but right now, we don't want to wait with this proclamation:

The most-significant new item seen at Sun 'n Fun was the Aero Advantage Dual Vacuum Pump.

The pump, which should be STC'd and PMA'd by this Fall, contains two separate rotor systems. It has a single inlet, and a single outlet, and is thus "transparent" to the aircraft. It requires no switching, and is thus "transparent" to the pilot, as well.

The vacuum pump, which is assembled in Texas, is slightly bigger than the standard unit: it's about 2" longer, and weighs a pound and a quarter more; but it provides redundancy to run your vacuum instruments.

The pump has additional features that make it a good idea: its output is rpm-related; it won't lose vacuum, as you rev up the engine. The rotors are pinned to the single-piece driveshaft (no couplings) with shear pins, that are designed to break, without doing damage to the driveshaft (and thus to the other side's functionality). [The driveshaft, of course, has a neck-down at the driven end, so a total failure won't damage the rest of your engine --ed.]

It uses a fail-safe internal valving, so that, in the event of one side's failure, your instruments will continue to work as though nothing happened. The only thing you'll notice will be a little red light.

When you fire up your aircraft, two little red diodes light up, to tell you that both vacuum pumps (in the one housing) are doing their jobs. The lights go out momentarily, as you pass through about 1200 rpm -- they're on at <3.5" Hg. (You don't want little red lights to be constantly "on," in your cockpit.) Should something go wrong with one part of the pump, its corresponding little red light would then go on, telling you that you're now down to one system (as you were, before you installed this pump). For reference, at 2700rpm, the Aero Advantage pump moves about 12 cfm.

Deliveries for Experimentals will start just before Oshkosh. The company is taking orders, at $695, for the pump -- that price is expected to cover orders taken now. The pump will be the same; it will come with, or without, the pedigree, depending on how soon you need it...

FMI: www.AeroAdvantage.com

[Mark Hislop]

I'd be surprised if this pump would be suitable for planes with boots. On the 337, they require a larger vacuum pump for booted aircraft than the same plane without boots. I would imagine that it might be difficult to get the new pumps approved.

Mark

[Kevin B]

Mark you may be right. I know the pump is now STC'D but I don't know for what models. It was just a suggestion.

[WebMaster]

Since I don't have my books with me, this week, it would be interesting to know what the booted planes require for volume and pressure. I seem to remember from annual that the boots take 8 psi, but that is from a very foggy memory. It's in the service manual, on checking boots.

[Bob Cook]

Hi Larry

I will look it up, however, I do know they are larger and thus more expensive than the standard pump. The last one was around 800 dollars plus installation. They do not seem to last for some reason.

Bob

[WebMaster]

If I remember correctly, the booted 210's have/had the same problem with quicker failure of the vacuum pumps.
Keeps you on your toes. hate that.
I mean, why can't most of the parts on a plane, especially the critical ones, last more than a couple of years?? Maybe because we accept it?
If the power steering pump on a mercedes failed every 3 years, there would be people screaming for a fix.

[bawb]

Just to be sure, verify the accuracy of the suction gauge. I had a 206 with a long history of premature pump and gyro instrument failures. First thing I did was put a hand-held vacuum pump on the suction gauge. When the hand-held read about 9 inches the suction gauge showed five. Previous mechanics had just cranked up the regulator to compensate for an apparent low vacuum problem. So the vacuum pump had been working it's heart out and the instruments were spinning up like mad.

Most people know to replace the hoses at pump time because of vane debris heading for the vacuum instruments.

Some pumps simply get too hot in particular installations resulting in consistent premature failure. A shroud and cooling duct can sometimes be fitted to eliminate that problem.

Parts to overhaul a tired but not destroyed pump can be bought for between $70-180. Once the pump is on the bench, it doesn't take long at all to overhaul one. A preemptive overhaul at 350 hours might be more convenient than a failure and replacement on the road.

Bawb

[Bob Cook]

BAWB

I check the guage by alternately starting and stopping the engines per the SB. The "FLAG" popped, however, the guage still read 5.5. The shuttle valve is always a source of concern.

All hoses replaced two years ago. I know it is the pump. I was told that overhauls do not last... guess that may be the question. I rather doubt there are any new pumps or alternatives at this point.

Thanks for the suggestion. I am going ahead and change out the pump. I have been looking for a 2in standby AI but they are out of this world for price (BGG type). Mags and vac pumps should be relegated to museums.

Bob

[Kevin McDole]

Originally posted by Bob Cook I have been looking for a 2in standby AI but they are out of this world for price (BGG type). Mags and vac pumps should be relegated to museums.

Agreed. If the Vacuum pumps don't kill you, the mags will get you.

Here's a radical idea … I was reading an old issue of IFR (November 1998) and it had an interesting article about how Hal Shevers had been trying to convince the FAA since 1991 to allow GA to replace their Turn Coordinators with a backup electrical AI. After 6 years, the FAA said it wasn’t important enough to get acted on now.

Some points from this story are:

1) If your Turn Coordinator is not needed for you autopilot, then replace it with a 2.25” T&B, and put a backup electrically operated AI where the Turn Coordinator was. The RC Allen electical AI's were something like $1600. I have no idea with the replacement T&B costs, but it has to be cheaper than the peanut AI's.

2) Or alternately, they made the argument, that on a case-by-case basis, your local FSDO may approve simply removing the Turn Coordinator and replacing it with the electrical AI. However, this was a crapshoot in 1998, so it can’t possibly be any easier in today’s climate to pull this off.

[Bob Cook]

Kevin

The AI is used for the AP. I have a 2 1/4 T&B. Room is the problem. There are some other alternatives coming along and echoflight will be offering a AI display using a seperate sensor. Midwest makes one as well......... even Garmin is offering a "form" of display in the new GPS.

Soon VACUUM AI's will be a thing of the past. The electronic gyro or rate "platform" and resultant cost has been the hangup. In the meantime the vacuum pump will continue to drive the boots and AI

I think you can replace an T&B with an electrical horizon with authorization.

I now have my moving map in my scan which is an early predictor for an AI failure ...... heaven forbid. I caught an HSI failure that way before ATC caught the problem. This occured shortly after takeoff on the climb. I continued on destination without a problem.

Bob

[Dale Campbell]

I have a friend that lives in Alaska that installed a Emergancy Vacuum sorce on his Lycoming engine. It was a cable operated valve on the intake manifold plus a hose and a tee in parallel to the vacuum pump, that he could operated from the cockpit. If the pump failed he could open the valve & keep the vacuum intsruments working until he got back on the ground and thats what it is all about.

[Bob Cook]

Dale

Rather hard to do when you have a turbo and positive pressure in the manifold <G>

Rather doubt you could get this approved on any AC....

Bob

[Dale Campbell]

BOB
I guess your right on turbo models. My ship is normally asperated.
Thats the price you pay to fly high.

[Dale Campbell]

Years ago they did not use vacuum pumps. I can remember the old cubs & stinsons had a cone shapped device on the side of fusalage that created a vacuum source with no moving parts to worry about. I think you can still get them. They would not work on the ground before take off. That would work once you got air born for emergancy use only.