C170B Vacuum Pumps

[Jeff Matthews]

I've got an alternator that will take a piggyback vacuum pump, though I've decided not to install it--no room in a 170A panel for enough stuff to make it really useful without hacking it up.

The alternator was built up of Nippondenso parts, and was rated at 50 amps. Tiny little thing, about the size of the one on my Tercel. Took an Airborne pump. The voltage regulator was straight off a Nippondenso alternator, but wired up to go on the firewall where the NAPA regulator normally sits. The alternator was also available without the pump drive, in which case the regulator sat on the back of the unit.

It looked like a well-thought-out installation, and came with some documentation about torque absorbed, etc., and a couple of 337's for previous installations. As I recall it had a necked-down spline drive so a vacuum pump failure couldn't take out the gears. With the pump it came pretty close to the firewall, and there was a dishpan available to alleviate that problem.

It was built by a fellow name of Stan Bedford, who made trailer hitches for a living dba Universal Tow-All. He was working on an STC, but dropped it in frustration several years ago. I haven't got his address here, but I can probably find it if someone's interested.

JM

[zero.one.victor]

Jimmie M emailed me an ebay link which got me to thinking. Has anyone installed an O-300D right-angle starter on a C-145 or O-300A? Apparently these right-angle adapters have a vacuum-pad on them, at least the one on ebay does. In the photo, it looks like the angle adapter has the same bolt pattern where it attaches to the accesory case.
You'd have to buy a starter, vacuum pump, and right-angle adapter, plus wire up a starter button, but then you'd have a factory-standard vacuum pump set-up.
You could sell off the old pull starter & starter clutch for a little something to help defray the costs.

Eric

[blueldr]

Eric,
In order to change over to an angle drive starter you would have to split the crankcases to remove the starter pinon shaft used with the pull starter and install the bushing used with the angle drive system. This would require a complete engine tear down. Hardly a minor job for the average pilot owner.

[zero.one.victor]

Thanks for the onfo, Blue, I didn't know about that. The B&C push-button starter also requires removal of the pinion shaft. I think they give you directions on cutting it off in place. Don't know anything about the bushing you mention, as I've never looked close at the innards of a D engine, or at the Continental book section on them.
It was just a thought, figured it was worth some discussion anyway.

Eric

[GAHorn]

TCM has a SIL (Service Instruction Letter) or SB which addresses the conversion of one engine model to another such as you mentioned Eric. Basically, installing the accessory case of a D onto an A engine is what you are suggesting, and I suspect TCM would approve of it under that SIL/SB. (Sorry not to have that number in my head.) I once converted an IO-520-D to an A engine, and all it required was an IA equipped with a Form 337, the SIL/SB and following the engine differences specifications issued by TCM,...then re-striking the engine data tag: IO-520-D CA. (Converted to A) per the TCM instructions.
FYI- although we all think of the O-300-D as being the engine with the angle-starter adaptor, a little-known trivia factoid is....that the C engine actually introduced that change in the latter serial numbers (via a mod-status change) and TCM, concerned about confusion issues, decided upon an engine designation change and utilized that starter on ALL D engines.

[cessna170bdriver]

...Basically, installing the accessory case of a D onto an A engine is what you are suggesting, and I suspect TCM would approve of it under that SIL/SB. (Sorry not to have that number in my head.)...

I ran across this topic while doing a search for any posts on the SVS standby vacuum systems (I've had an SVSIII for many years, and it works quite well). There was an AD issued on the unit some time back and I was just checking to see if there was any more info here.

Anyway, it interests me that there might be an SIL or SB from TCM addressing changing one engine model to another. I looked into installing the right angle starter drive and vacuum pump on my O-300A when I last overhauled it in the late 80's. I had all of the parts except for the pump, but when I checked with my mechanic on the paperwork end of it, he said that the change would require a field approval, and the Atlanta FSDO wasn't doing any field approvals at the time. (In retrospect, I think the mechanic just didn't want to mess with it.)

Now that I'm about to overhaul that engine again, I'd like to revist the possibility of putting a wet pump on it. George, can you find that SIL or SB number for me? I'm not positive it will apply in this case because, strictly speaking, the engine will not be fully converted to a "D" as it will still have the crankshaft with the eight-bolt propeller flange.

Thanks in advance for any help you are able to offer,
Miles

[blueldr]

Miles,
How many inches of vacuum will your SVS give when you're crossing the Sierras at a MEA of 9,000ft.? If you reduce the throttle far enough to provide 4 inches of vacuum, will the airplane maintain altitude?

[Bruce Fenstermacher]

Miles
The TCM SB your looking for is in the MX library right here.
Since you would have the eight bolt crank I believe you would be converting your engine to the "C" configuration George spoke of.

http://cessna170.org/phpBB2/viewtopic.php?t=2303

[cessna170bdriver]

Bruce, thanks for the info, I'll check it out. I guess I could have done a better job in my search.

Dick,

Anybody crossing the Sierras IFR in a stock 170 would need to have his/her sanity checked. I installed the SVS more as a way to spool up the gyros before departure rather than as a backup system. Back in Mississippi it was nice to have it taking off on those "clear and one" days. Also, I may be all wet, but I feel like its easier on the gyros if they are up to speed while you're bumping along on the ground. The SVS is also handy on approaches to be able to slow down to a reasonable speed and not be blasting around fast enough for the venturis to work.

I've never used the SVS at 9000 ft, other than the testing required for the installation. I think everyone here knows what the result would be: At 9000 ft you have 21 inches MP at full throttle. Thake 4 inches off of that to run the gyros, and you're probably coming down, or at least doing some very slow flying. In an actual IFR emergency you would back off the throttle long enough to "spool up" the gyros (Precise Flight's terminology), then go back to full throttle, repeating the process as necessary.

Miles

[GAHorn]

Actually, Bruce (and Miles) the C engine also used the same 6-bolt crank as the D engine. Therefore, Miles, since you are a TIC170A member, you should send Velvet $75 and Ronnie Massicot will send you his STC to install your C or D engine in your 170.

[cessna170bdriver]

George,

If, as you say, the O-300C engine also had a 6-bolt propeller flange, then there is no model that Continental produced that would cover my proposed configuration. My question is whether or not I could use this particular service bulletin as "approved data" in a case where I would install the accessory case and starter drive from a C or D engine on my O-300A AND retain the 8-bolt crankshaft. The way I read the SB is that it covers converting one engine dash letter configuration to another, not mixing and matching. I don't want a vacuum pump bad enough to also buy another crankshaft and propeller (or another engine for that matter). If my current crankshaft won't pass inspection, then that is another story...

Miles

[GAHorn]

I've not seen any documentation to support this, but I've been told that TCM will approve 8-bolt cranks in later engines, and 6-bolt cranks in earlier engines. IF that is so,...and if it can be obtained in writing, then that info should make it easier to convert to a C or D, and use an A crank in an O-300. While it may not be "approved" data....it would likely fall under "acceptable" data. Visit with TCM and your FSDO about it. Good luck. (As for me, I like simple, reliable, venturis.)

[lowNslow]

Miles, I just got an AD for the SVS system. I don't have one installed, but if you didn't get it look for AD 2005-11-05 or:
http://www.thevacsource.com/pdfs.php

Something about failed shuttle control valves.

[cessna170bdriver]

Karl,

I just got that AD too. That is what started me looking for more info. My SVSIII has had an AD for several years now. As best as I can tell, this latest one adds a couple of other models to the list. At each annual I have to test the shuttle valve and the shutoff valve. It's really no big deal. So far, mine has worked fine (installed in the early 1990's).

Reading the info at the link you posted (FAAese translated to English) I see that there is an Alternate Method of Compliance (AMOC) to eliminate the recurring inspection where, if I have a late enough serial number, all I have to do is download a new Flight Manual Supplement and a new Installation Report and put them in the airplane and make a logbook entry. If the system is before a certain serial number, I would have to buy parts to upgrade to the latest model, perform a flight test, submit a new 337, yada, yada, yada. As soon as the NPRM was issued for this latest AD, Precise Flight raised the price of the parts from $195 to well over $300.

I was just checking here to see if anyone has has any real problems that might warrant the new parts (or, more likely, warrant trashing the whole thing). It sounds like no one else admits to having one, so in the absence of any real data, and if my sytem is to old to upgrade via paperwork only, I'll just keep doing the recurring inspection.

Miles

[GAHorn]

OR...you could just... K I S S



(hint: venturis)