Bravoman Posted December 9, 2014 Report Posted December 9, 2014 Just replaced my primary vacuum pump which failed in imc a couple weeks ago. My plane is a 98 with about 1030 hrs. From looking at logs it appears this was the original pump. Kind of surprises me that it could last 15 some years. I was curious about what others have experienced in terms of pump longevity? Also, my backup has only been used about 5 hrs. They have a Hobbs type meter so you can tell how much usage it's had. It works fine but I was considering replacing the original backup due to age and lack of use(I try to exercise a backup at least once monthly to keep the juices flowing but it is clear that the prior owners didn't do this which adds to my concern) as a prophylactic measure. Would hate to need the backup and have it not work. I have an aspen PFD but am still not totally comfortable having that as my only AI in the clag. So question is would it be overkill and waste of money to replace the backup pump? Regards, Frank Quote
rbridges Posted December 9, 2014 Report Posted December 9, 2014 I'm interested to hear what people say. My backup pump hasn't been used much, but it's pretty old. I just replaced my primary and it had around 900hrs. the new tempest is warranted for 1300 hours. Quote
N201MKTurbo Posted December 9, 2014 Report Posted December 9, 2014 my backup and main are the same. when the main went out I moved the backup to the engine and put the new one on the backup. It has been working just fine. I don't see any parts in the pump that would deteriorate with age. Quote
FloridaMan Posted December 9, 2014 Report Posted December 9, 2014 Mine was 17 years old and had 1400+ hours on it when it failed. Oddly enough, it was the Airborne model that was supposed to have been replaced due to an AD or SB regarding failure. It was shortly after I purchased the airplane and I think that the highly experienced previous owner may have been to credit with its long life -- and then a kid like me gets it and it lasts three months. edit: oh crap; I just realized this was the Bravo forum. Quote
Marauder Posted December 9, 2014 Report Posted December 9, 2014 These pumps have been hit or miss with me. The one I have in there now has 700 hours on it. But I have seen a couple fail below 500 hours. I am not familiar with how the backup works on the Bravo. But with 3 backups (2 vacuum & 1 electric - with battery) you should be fine. It might not be a bad idea to stagger the vacuum pump replacements. Quote
Marauder Posted December 9, 2014 Report Posted December 9, 2014 Or you could go to a wet pump Are they still available? Quote
carqwik Posted December 9, 2014 Report Posted December 9, 2014 I'd say "overkill" given that you have the Aspen (works on electricity), a standy-by AI which runs off your primary vacuum pump, and then the stand-by pump which still works and is lightly used. Given that the Bravo has two batteries, I'd be more concerned about the health of your alternators and batteries first, the age/use of the primary vacuum pump second, and last the back-up pump. IIRC, one problem with the back up pump is that you have to pull the throttle to idle before engaging the stand-by pump in flight.... Quote
FlyDave Posted December 9, 2014 Report Posted December 9, 2014 I have a logbook entry from October of 2005 that states "Removed failed engine driven standby vacuum pump. Installed Mooney provided and approved electric motor driven standby vacuum pump retrofit kit ....." I didn't know the original was an engine driven backup vacuum pump. So my backup was new in 2005 and now has around 450 hours on it. My primary was replaced at the same time so it has around 450 hours on it as well. I think exercising it on a regular basis is a good idea - I'll add it to my repertoire. My KI-256 failed 9 days ago is in for rebuild right now. It's the only vacuum driven device left in my panel. But it only lasted 330 hours since the last rebuild. I like the idea of having an AI that is independent of the electrical system (even thought I have 2 alternators and 2 batteries) but having it fail every 350 hours is kind of crazy. Hopefully I'll get more than 330 hours out of the rebuild by Bob Bramble at AeroLab. Quote
FBCK Posted December 9, 2014 Report Posted December 9, 2014 My vacuum pump failed at 180 hours and four years old this summer. I'm about to put the new Avidyne IFD 540 in my plane and I was thinking about having the avonics show take out my ADF at the same time and putting a Dynon D2 in as a backup. I currently dont have a backup, any thoughts on this. Quote
carusoam Posted December 9, 2014 Report Posted December 9, 2014 Vacuum pumps have carbon blades... They wear easily and break easily if something isn't right. They don't oxidize unless you light them on fire. My back-up pump is driven by an electric motor in the tail. It got exercised a few days ago while I was at the hangar. It's 20 years old going strong... The IFR world is slowly going electronic with second generators, second batteries, and back-up batteries in the electronic HSI. Make sure your check list is updated to test all the b/u systems before blasting off into IMC... My thoughts, -a- Quote
Releew Posted December 10, 2014 Report Posted December 10, 2014 My pump failed right at 500 hours. I saw a lineman turn the prop backwards and literally on the next flight it failed. Some mechanics claim fact, others myth...... The vanes are designed to rotate in ONE direction in a very tight tolerance. Has anyone else heard of pumps failing based on physically turning the prop backwards??? Rick Quote
Bravoman Posted December 10, 2014 Author Report Posted December 10, 2014 Vacuum pumps have carbon blades... They wear easily and break easily if something isn't right. They don't oxidize unless you light them on fire. My back-up pump is driven by an electric motor in the tail. It got exercised a few days ago while I was at the hangar. It's 20 years old going strong... The IFR world is slowly going electronic with second generators, second batteries, and back-up batteries in the electronic HSI. Make sure your check list is updated to test all the b/u systems before blasting off into IMC... My thoughts, -a- I agree wholeheartedly. I am getting much more conscious of the risks attendant to IFR operations. That's why I posed the original question about the backup pump. I have recently also replaced both batteries and have similar concerns about the alternators which are also original. I guess one has to factor in the improbability of both failing simultaneously, but 15 years seems like a long time on these wear items, and lack of use of the backup has to take its toll as well. 1 Quote
carusoam Posted December 10, 2014 Report Posted December 10, 2014 Rick, Part of primary training was to not turn the prop backwards. The school must have lost a pump or two.. Turning a pump backwards is not supposed to be damaging, but... The blade materials are so brittle it doesn't take much to break them. Under normal conditions, the blades are going to wear with a slight angle to them. If they are operated going the other direction, it is possible to deflect, and catch on the now sharpened and now leading edge. Hopefully you can picture what's in my mind! I would avoid turning it backwards if possible, and be mindful when starting the engine to avoid having the prop bounce backwards. Best regards, -a- Quote
N201MKTurbo Posted December 10, 2014 Report Posted December 10, 2014 Some pumps have straight vanes some have angled vanes. All the pumps with CC or CCW in the part numbers have angled vanes. I always disassemble my dead pumps to see what went wrong. I have a rebuild kit from 25 years ago, I haven't found a dead pump yet that could be rebuilt. They are all worn or cracked beyond usability. The failure is almost always caused by the slots wearing to the point where the warn vanes cock sideways and get jammed in the cavity. When this happens, it cracks the carbon hub and usually cracks the body of the pump. And about a microsecond later the shear coupling shears. I can't see a new pump breaking by turning the prop backwards, but I can see a warn pump on the verge of failure getting jammed up by turning it backwards. 1 Quote
gjkirsch Posted December 10, 2014 Report Posted December 10, 2014 As a preventive measure, I change out the primary pump after 500 hours. I am assuming you have the backup electric driven pump (in the tailcone) and not the original back up pump mounted on the engine. The engine driven pumps are not recommended as they have a histroy of failing when engaged. (You are supposed to reduce power before engaging the back up pump to minimize the torque of full power). So if you are in IMC, and you loose the primary, you might already be out of sorts, now you have to remember to reduce power. As part of your preflight, you should engage the backup and verify by sound and the panel light that it works. I have never replaced one of the electric units as they never gotten more than an hour or so a year of use. I have had three planes with them and used them in two. The last plane had the backup engine driven pump and I had it replaced. Quote
Bravoman Posted December 11, 2014 Author Report Posted December 11, 2014 As a preventive measure, I change out the primary pump after 500 hours. I am assuming you have the backup electric driven pump (in the tailcone) and not the original back up pump mounted on the engine. The engine driven pumps are not recommended as they have a histroy of failing when engaged. (You are supposed to reduce power before engaging the back up pump to minimize the torque of full power). So if you are in IMC, and you loose the primary, you might already be out of sorts, now you have to remember to reduce power. As part of your preflight, you should engage the backup and verify by sound and the panel light that it works. I have never replaced one of the electric units as they never gotten more than an hour or so a year of use. I have had three planes with them and used them in two. The last plane had the backup engine driven pump and I had it replaced. That's a good question. I think whatever backup pump I have is original but I am going to double check the logs. I take it if it is original it is engine driven? Quote
carusoam Posted December 11, 2014 Report Posted December 11, 2014 If you have an electric b/u pump there is a switch on the panel near the fuel pump for it.... The motor and pump would be in the tail, forward of Battery 1. Long Bodies would want it put in the tail for improved W&B... In place of Charlie weights... Best regards, -a- Quote
Bravoman Posted December 11, 2014 Author Report Posted December 11, 2014 Yes, the switch is along side the fuel pump, stdby alt, pitot &prop heat etc. so must be electric. I guess if it comes on without engine running it is electric. 1 Quote
carusoam Posted December 11, 2014 Report Posted December 11, 2014 You will hear it run when the engine is quiet... And see the vacuum gauge in the green as well. Best regards, -a- Quote
N201MKTurbo Posted December 11, 2014 Report Posted December 11, 2014 My pump went out a while back and I had to limp home for six hours with the standby electric pump. It blew the circuit breaker after 5 min. I waited till the gyros started to get sloppy and then turned it back on. It blew again after about 10 min. I reset it again and it ran without incident for the rest of the trip. The bottom line is you should exercise the electric pump a bit more then is recommended. BTW I was VFR, but I like my autopilot, so I like having the gyros working. Quote
ryoder Posted December 13, 2014 Report Posted December 13, 2014 I was never told not to turn the prop backwards. This is news to ne, thanks carusoam. Quote
rbridges Posted December 13, 2014 Report Posted December 13, 2014 I was never told not to turn the prop backwards. This is news to ne, thanks carusoam. I've seen people argue about it both ways. I don't know if it matters, but I don't turn my prop backwards just in case. Quote
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