I took my plane to the avionics shop where they declared the autopilot DOA, removed it and shipped it to Megit for repairs (I should get it back next week). They also found the electric trim auto pilot disconnect switch defective. They ordered one from Cirrus and will install it when the autopilot comes back. They said that the GPS 1 not sending glide slope information to the Sandel during preflight checks is normal and that the manual is wrong saying that it should.
I then taxied to the Cirrus service center to have some other repairs done (it has been almost 3 weeks since I was there last). When I turned on the master switches I did see the red vacuum light, the yellow aux vacuum light, or hear the aux vacuum. I had a new repair to aid to the list of items for the service center. It seems that the vacuum sensor on the engine driven fuel pump failed. This means that if the engine driven vacuum pump fails not only will you not get a vacuum light, but you will not be able start the backup vacuum pump. The entire manifold has to be replaced. I asked him to wire out the sensor so I would be able to use the backup unit if the primary failed. He said he couldn’t do that since it was against maintenance practices. He put everything back the way it was and the sensor started working (until it fails again). It seems there should some way to manually turn on the backup pump, since a redundant vacuum system is useless if the single point of failure sensor fails.
The CHT works a better now after they installed it on the #2 cylinder where the maintenance manual says it should be instead of on #3 where the factory had it.
We also noticed that the cowling was poorly finished because you could see and feel the fiberglass hatch pattern where they did not use enough resin during construction. I won’t complain about this. They have a full time job just repairing critical components and don’t have time for quality of finish.
If a single system goes wrong twice in a short period of time, like a vacuum pump or an HSI, then a third replacement should not be accepted. The problem is almost certainly not the part that is failing - something else in the plane is killing it. You should insist that the root of the problem is fixed, rather than the failed part mindlessly replaced yet again.This will get really interesting when the planes suffering these multiple failures come out of warranty.
That would usually be sound advice, but the experience of at least some people with, e.g. the Century HSI is that after they get enough replacements, they finally get one that works. And the faults usually tend to be different. The HSI failures seem to suggest either bad quality control at the factory, or, as Century has suggested, mishandling during shipping (except that I would call that inadequate packaging.)
On vacuum pumps, you are probably right, but nobody has yet been able to find a cause for the high failure rate of the Airborne vacuum pumps on the IO-360ES, in spite of some exhaustive testing. I know that Continental has done extensive vibration and temperature testing on at least one aircraft, and finally swapped the entire engine out to test it back at the factory. They still could not find any explanation for the 7 or 8 vacuum pump failures on that engine in 500 hours. The new engine has only done about 50 hours so far, so it’s too soon to say if the problem is fixed.
So far, even on planes out of warranty, the vacuum pumps are being replaced by Airborne at their expense, and the HSI faults seem to fall into the infant mortality time-frame, so I don’t think warranty has been an issue. Same with the Garmin gear - we had three transponders fail early on, but the last one has been fine.
I can’t help believing that the vacuum pump issue is somehow heat related. I realize that my own experience is a “sample of one”, but I replaced the vacuum pump three times over the summer, then flew all winter with no problem. That makes two winters with no issues, one summer with 3 failures. I’m really expecting to see failures again as things warm up now.
As a counterpoint to the Century HSI failure rate… my own HSI has been rock solid since day one… so far so good (490 hours).
There was a post some time ago on the high rpm the pump is running on. I thought that this was the reason for so many failures and that a slightly reduced engine rpm cured the problem. Hein
Mike,
my service center (General Enterprises, Holland) is VERY sure that it is a cooling problem of the vacuum pump, and they found a way to cool it better. Contact Rob van Doorn at GE.
We’ve lost three pumps in about 300 hours. Several months ago I asked COPA Response to inquire about any efforts at the factory to find the root cause of the vacuum pump failures. We’ve never gotten a response, and I suspect they have bigger fish to fry at the moment.
Our mechanic is pretty sure the problem is heat, and has applied for an STC to put a cooling shroud over the pump. Since we’re moving into the warm part of the year, I’ll let you know how it does. We’ve also installed the slotted lower cowl plate, and hope that pulls some additional heat out of the engine compartment.
Several months ago I asked COPA Response to inquire about any efforts at the factory to find the root cause of the vacuum pump failures. We’ve never gotten a response, and I suspect they have bigger fish to fry at the moment.
Hi Michael,
Not sure who you mean that hs “bigger fish to fry at the moment” - I suspect you mean Cirrus. (We at Response! have NO fish to fry… we just take the questions we get, and try to get answers!) Perhaps that’s true of Cirrus to some extent, although they do seem to grind (slowly) at getting us the answers.
In this case, we still don’t have any real answers to add to the personal emails I sent you in response to your posts. We’ve discussed it with the company several times, though, and Cirrus undertook to actually analyze the failure rates. The last time we spoke about the issue (last week), Customer Service told us that they had completed their analysis, and concluded that while there are many instances of “infant mortality” of vacuum pumps, there are also many instances of vacuum pumps lasting very well; and that overall, the instance of vacuum pump failures is almost exactly in line with the failure rate across the G.A. industry.
I haven’t seen the numbers yet - when I get them, I’ll publish them. FWIW, my own experience (and impression) matches yours – they fail too often, and there must be a REASON for it. However, at this point, it seems that Cirrus feels that we’re simply seeing normal failure rates.
Have no idea how this compares to GA as a whole etc. One oddity is that hours 0-200 for my airplane included a lot of VERY hot weather operation. Almost no hot weather operation since I’ve been on the east coast. I know that’s not exacty the temperature question you’ve been considering, but it then makes me mildly surprised that the second pump lasted only half as long as the first one.
Could it be a combination of heat and RPM? Would climbing at 2600 RPM on hot days help? Interesting that the SR20, with its tendency to run hot is the same plane that seems to have vacuum failures. Maybe relevant, and maybe I’m adding two and two to get five.
Actually Mike, it looks like Cirrus has decided to deal with the vacuum problem but just getting rid of it. The new version SR20 will be all electric like the SR22. This seems to indicate that they feel this approach is a better option because the pumps keep failing.
I do feel a bit uncomfortable placing all the instrument options in the electric category. At least if you have an electrical problem NOW, the vacuum instruments still work.
Brian
Have no idea how this compares to GA as a whole etc. One oddity is that hours 0-200 for my airplane included a lot of VERY hot weather operation. Almost no hot weather operation since I’ve been on the east coast. I know that’s not exacty the temperature question you’ve been considering, but it then makes me mildly surprised that the second pump lasted only half as long as the first one.
Jim,
Speaking strictly as an individual here (i.e. not at all for COPA or Response!), I feel that there must be a reason or combination of reasons for these failures – perhaps a clue that we haven’t paid enough attention to is precisely the fact that some airplanes actually have very FEW failures.
Some of the possible culprits:
Temperature
RPM
Pressure on the end of the pump drive shaft
Poor quality pump
Crud in the system from a previous failure, exascerbating future installations (lines blow out, filters changed, etc. when new unit put in?
The last one is what makes me wonder about pumps that are more reliable - is it just a case of the A&P doing a better job?
Again, I don’t mean to imply any knowledge or authority - stricly my own musings.
Interesting that the SR20, with its tendency to run hot is the same plane that seems to have vacuum failures.
Andy,
When you said “the SR20 … is the same plane that seems to have vacuum failures”, I’m not sure if you were contrasting it to the SR22 or to the GA fleet as a whole.
Obviously one would expect infinitely more vacuum failures in the SR20 than the SR22. [;)]
I do feel a bit uncomfortable placing all the instrument options in the electric category. At least if you have an electrical problem NOW, the vacuum instruments still work.
Brian,
Completely agree; I love the systems diversity of having separate vacuum and electrical systems. However, as I just wrote in an email, “…from a design viewpoint, it comes at a pretty high price. We pay for two vacuum pumps, an electric motor, a bunch of plumbing, and all the effects that adding complexity has on overall reliability and weight… just to drive one Attitude Indicator. So, I feel that we are certainly losing some systems diversity, but that perhaps the “right” way to compensate for it is to have an emergency battery source for the AI, just as we do now for the TC…”
I realize that some SR20s have a vacuum-driven HSI, too, but my understanding is that there are only a few of those. In an case, I will discuss the battery-backup idea with a few people, because to me it makes sense.
For me personally, after experiencing a variety of in-flight failures in 27 years’ worth of flying, I need the security blanket of portable, battery operated equipment as a backup, no matter how the systems of the airplane are designed. Right now, that translates into a Yaesu handheld radio (with an external antenna plug that lets it connect to my COM1 antenna), and a Garmin 295 GPS. Since I presently do have a vacuum-driven AI, I’ve stayed away from the cost of something like a MicroEFIS, but I suspect that one lies in my not-too-distant future. It’s been too long with no new toys.
Steve, I wasn’t especially clear in my point. What I meant is that the SR20 seems to run hotter than other planes (in general) and that the SR20 seems to have more vacuum failures than other planes (in general), and maybe there’s an association.
By the way, I’ll join the crowd in saying good work in a difficult situation.
Wasn’t backwards rotation also discussed at one point as a possible vacuum pump killer, or was that an alternator killer? (E.g., moving the prop in the wrong direction when ground handling.)
Mike, Gordon, thanks for the diagnostics. I’ll see what the AirWays people say when they look at the failed pump. From the user perspective, I don’t think I’ve ever turned the prop backwards, and my RPM procedure is: 2700 for the first minute or two after takeoff and for some enroute climbs, 2500 the rest of the time. So we’ll see. Having not owned other planes, I don’t know how the pump lifespan in the Cirrus compares to fleet averages.
Mike, some of those issues (well all of them actually) have been extensively explored on at least one plane which was having vacuum pumps last < 100 hrs. It had the pump drive replaced, the entire vacuum system plumbing replaced, both vacuum instruments replaced, in-flight and ground monitoring of pump temperature and vibration levels - all within normal limits. None of the work made any difference to the failure rate. Latterly the entire engine has been replaced to allow the old one to be studied by Continental at the factory - still nothing to point the finger at - the new engine has only done 50 hours, so it’s too soon to tell if it has made any difference.
The same Airborne pumps on other aircraft will last 500-800 hours.
My theory? A combination of RPM and temperature extremes that, while possibly each within specified limits for the pump, together stress the pump leading to premature failure. Solution? perhaps the cooling shroud proposed by some will help, or else try a different brand of pump - there are several others on the market, the Sigma-Tek in particular does not have the restriction on direction of rotation. In the meantime, Airborne keeps replacing them under warranty, so what to do??
Wasn’t backwards rotation also discussed at one point as a possible vacuum pump killer, or was that an alternator killer? (E.g., moving the prop in the wrong direction when ground handling.)
Gordon,
Quite right - I forgot about that one. It is indeed the vacuum pump that is susceptible to that particular form of mishandling. [I can’t think of any reason the alternator would object, though.]
The reason for the vulnerability is fairly clear in the attached photo of the innards of one of my failed pumps - those “vanes” are made of graphite, if I remember correctly. When they are turning in the correct direction (clockwise in the photo), they constantly “hone” themselves to the right shape so that they seal to the wall of the chamber at the right phase of the rotation. But turn them the wrong way, and they may catch and snap. At least, that’s my understanding.