(Dual) Vacuum Pump Failure

Radar Contact

Radar Contact

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Kevin
I don't post most of my weekly videos here but I thought this one would be good for discussion and Jaime gives a shout out to POA's own @kayoh190 :)

When I first bought the plane it had a fairly original 6 pack. The primary AI was vacuum driven and the autopilot ran off that. The back up was a 40+ year old turn and bank indicator that even in level flight just toggled back and forth left and right of center. I was a relatively early adopter of the G5 and then had the G5 HSI installed and recently the IFD550 (with AHRS).

A couple weeks ago enroute to our Gulf Coast Swing vacation I experienced a dual vacuum pump failure. I was on an IFR flight plan but was VMC. Unbeknownst at the time, my surface de-ice switch became faulty and that resulted in an un-commanded full inflate of the boots with no deflating allowed. My pumps were staggered in years and hours but the lowest time one was about 4-5 years and maybe 300 hours or so. Shortly after this happened, my pumps failed within 10 minutes of each other. If this would have happened a few years ago while IMC, it would have been a full blown emergency for me with the old T&B that I had.

I guess I have a few thoughts about this. 1) I love the new affordable tech that has made our cockpits safer. 2) If you don't have advantage of this in the plane you fly IMC, make sure your backup (T&B, Turn coordinator, etc) is up to the challenge if called upon to help keep you upright. 3) Whatever equipment you have on your plane, make sure you are comfy with partial panel and fully understand how it all operates.

In the end this was fairly tame and after speaking with my mechanic, we were able to continue our trip legally.

 
From my root-cause analysis background, I have to ask - in dual vac pump setups, could there be any upstream issue that could trash both pumps almost simultaneously? That’s too odd a coincidence to be random, though not impossible.
 
It doesn't sound like you experienced independent probabilities of identical component failure, which is the subtext of your claim. Sounds like your boots blew both pumps in succession because that awesome "certified" orphaned electric subcomponent failed in the wrong position.

I'm more interested to hear what Textron wants for that certified switch.
 
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Radar Contact said:
I don't post most of my weekly videos here but I thought this one would be good for discussion and Jaime gives a shout out to POA's own @kayoh190
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Hahaha! I was just thinking about you guys while down in Jacksonville the other day. We were being vectored around for the RNAV and broke out from the overcast as the controller brought us down to 3000'. We were on a base at this point and mentioned that we had the airport in sight if it helps. The controller comes back half laughing, "You guys want the visual???"

Apparently our reputation isn't just limited to ORD! :p
 
Radar Contact said:
In the end this was fairly tame and after speaking with my mechanic, we were able to continue our trip legally.
Click to expand...
So you deferred both vacuum pumps and the boots under 91.213. Tell us about that process?

Also, pulling the CB for the boots didn’t deflate them?
 
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Reason 892,714,365,219 that I don't miss the old gauges at all, and love the new glass cockpits. Two primary screens, and if both faith, a backup is still available. Another thread is active right now talking about how expensive new planes are, and I agree they are, but also these new planes have a panel that I couldn't even dream of when I started flying in my ancient old plane...that alone to me is worth a lot more money when buying. These glass cockpits seem to be not just a lot better, but also significantly more reliable.
 
Shuswap BC said:
Reason 892,714,365,219 that I don't miss the old gauges at all, and love the new glass cockpits. Two primary screens, and if both faith, a backup is still available. Another thread is active right now talking about how expensive new planes are, and I agree they are, but also these new planes have a panel that I couldn't even dream of when I started flying in my ancient old plane...that alone to me is worth a lot more money when buying. These glass cockpits seem to be not just a lot better, but also significantly more reliable.
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Even if you have all the fancy new instruments you’re typically going to have vacuum pump(s) if you want deice boots.

The Malibu I fly doesn’t have a single mechanical instrument in it anywhere, not even a compass. Yet it has a vacuum pump to run the pressurization and deice, and will continue to need to be cared for. Sounds like the OP is in a similar position.
 
mondtster said:
Even if you have all the fancy new instruments you’re typically going to have vacuum pump(s) if you want deice boots.

The Malibu I fly doesn’t have a single mechanical instrument in it anywhere, not even a compass. Yet it has a vacuum pump to run the pressurization and deice, and will continue to need to be cared for. Sounds like the OP is in a similar position.
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Ive never owned or flown a pressurized plane, so I am not familiar with how those systems work. How does the vacuum pump factor into the pressurization system? I thought the turbocharger was the necessary accessory for pressurized hulls. Is the vacuum pump needed for the control system, or something like that?
 
GRG55 said:
Ive never owned or flown a pressurized plane, so I am not familiar with how those systems work. How does the vacuum pump factor into the pressurization system? I thought the turbocharger was the necessary accessory for pressurized hulls. Is the vacuum pump needed for the control system, or something like that?
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You’re correct. The turbos provide the air to pressurize the cabin but the outflow valve is controlled/actuated by vacuum from the vacuum pump. The airplane I fly on a regular basis is a 2016 with a G1000 system in it which has the pressurization control built into it so I was shocked to discover that the outflow valve was still pneumatically controlled rather than electrically. I suspect this is a case of a legacy design being used with a modernized user interface.
 
mondtster said:
You’re correct. The turbos provide the air to pressurize the cabin but the outflow valve is controlled/actuated by vacuum from the vacuum pump. The airplane I fly on a regular basis is a 2016 with a G1000 system in it which has the pressurization control built into it so I was shocked to discover that the outflow valve was still pneumatically controlled rather than electrically. I suspect this is a case of a legacy design being used with a modernized user interface.
Click to expand...

Thanks for the clarification. I didn't know that.

But it raises an interesting question. A friend of mine with a Malibu once told me there are two outflow valves (presumably so if one fails there is no chance of overpressuring the hull?). But if there is only one engine-driven vacuum pump perhaps the redundancy in that system is less than what one might anticipate?

Edit added: I believe he has an auxiliary electric vacuum pump in the plane, so perhaps that is covered with adequate redundancy after all...

Radar Contact said:
I don't post most of my weekly videos here but I thought this one would be good for discussion and Jaime gives a shout out to POA's own @kayoh190 :)

When I first bought the plane it had a fairly original 6 pack. The primary AI was vacuum driven and the autopilot ran off that. The back up was a 40+ year old turn and bank indicator that even in level flight just toggled back and forth left and right of center. I was a relatively early adopter of the G5 and then had the G5 HSI installed and recently the IFD550 (with AHRS).

A couple weeks ago enroute to our Gulf Coast Swing vacation I experienced a dual vacuum pump failure. I was on an IFR flight plan but was VMC. Unbeknownst at the time, my surface de-ice switch became faulty and that resulted in an un-commanded full inflate of the boots with no deflating allowed. My pumps were staggered in years and hours but the lowest time one was about 4-5 years and maybe 300 hours or so. Shortly after this happened, my pumps failed within 10 minutes of each other. If this would have happened a few years ago while IMC, it would have been a full blown emergency for me with the old T&B that I had.

I guess I have a few thoughts about this. 1) I love the new affordable tech that has made our cockpits safer. 2) If you don't have advantage of this in the plane you fly IMC, make sure your backup (T&B, Turn coordinator, etc) is up to the challenge if called upon to help keep you upright. 3) Whatever equipment you have on your plane, make sure you are comfy with partial panel and fully understand how it all operates.

In the end this was fairly tame and after speaking with my mechanic, we were able to continue our trip legally.
Click to expand...

Wow.
I'm going to have to study my boot system more closely. This is not a failure mode, taking out both pumps in quick succession, I would have anticipated.
Thanks for posting!
 
GRG55 said:
Thanks for the clarification. I didn't know that.

But it raises an interesting question. A friend of mine with a Malibu once told me there are two outflow valves (presumably so if one fails there is no chance of overpressuring the hull?). But if there is only one engine-driven vacuum pump perhaps the redundancy in that system is less than what one might anticipate?
Click to expand...

The second valve you’re referring to is the safety valve. They’re usually set slightly higher than the normal operating pressure and will open if the outflow valve somehow fails to regulate the cabin pressure and it goes high. The ones I’ve seen were not vacuum controlled and were there as a safety pressure relief not as something that would normally actuate.

When the vacuum pump fails the cabin won’t pressurize so it is in a relatively safe condition. I suppose if it happened at high altitude there would be some risk but with the G1000 there will be all sorts of alarms going off and since the airplane ceiling is capped at 25000 feet the time of useful consciousness isn’t terrible.
 
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Glad everything turned out ok. I’m a hold out on new tech, sure vacuum pumps fail but as more and more glass panels make their way to market the stories of them failing are starting to add up. Granted most of the time it’s a glitch that sometimes returns fairly quickly and sometimes returns after a master cycle, but sometimes not at all. Until the fleet gets more hours I’ll hang onto my old trusty vacuum pump for now.

At the Venture flyin two guys said their G3X went all red X mode while on an approach. One came back almost immediately, the other had to go missed, cycle his master switch Which restored everything. Several local G5 adopters have had instances of their G5 ****ting off, or freezing up.
 
Grum.Man said:
Glad everything turned out ok. I’m a hold out on new tech, sure vacuum pumps fail but as more and more glass panels make their way to market the stories of them failing are starting to add up. Granted most of the time it’s a glitch that sometimes returns fairly quickly and sometimes returns after a master cycle, but sometimes not at all. Until the fleet gets more hours I’ll hang onto my old trusty vacuum pump for now...
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I am in the same camp. I like true redundancy, but appreciate for light aircraft there's both a lack of need (day VFR pleasure planes such as my Husky, which the original owner filled with waaaay too much unnecessary panel stuff) and practical limits to how much.

The display on my JPI engine monitor went south and I had to remove it and send to California to have repaired. Fortunately it's not a certified replacement for the factory gauges, or the plane would have been grounded for a couple of weeks. Not something I would prefer on the wrong end of a cross country journey.

Dual G5's are interesting as they can cover for each other, and even if both fail you can get the plane home VFR if necessary. But the single glass screens that "do everything" bother the hell out of this old school boy.
 
hindsight2020 said:
It doesn't sound like you experienced independent probabilities of identical component failure, which is the subtext of your claim. Sounds like your boots blew both pumps in succession because that awesome "certified" orphaned electric subcomponent failed in the wrong position.

I'm more interested to hear what Textron wants for that certified switch.
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While it's true the switch failed and that indeed caused both separate vacuum pumps to fail, the result was still a dual vacuum pump failure. I didn't find out about the switch until well after the flight and after I made the video. If someone made a post about their twin engine failure/dead sticking a 310 to the ground and it was later found to be caused by a mis-fueling event, I'd be fine with the discussion/title about a "dual engine failure". :) I wasn't trying to be misleading, just wanted to spread the word to other de-ice boot owners about this failure mode I had never heard of.

I'll report back on the switch when they send me the bill.
 
MauleSkinner said:
So you deferred both vacuum pumps and the boots under 91.213. Tell us about that process?

Also, pulling the CB for the boots didn’t deflate them?
Click to expand...
As to the first part, it's kind of long and I'll try to write that process up when I have more time.

Reference the CB, no it doesn't deflate them completely. They require a bit of suction to keep them tight against the wing.
 
GRG55 said:
Wow.
I'm going to have to study my boot system more closely. This is not a failure mode, taking out both pumps in quick succession, I would have anticipated.
Thanks for posting!
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Me either! That is why I wanted to spread the word to other de-ice boot drivers out there. I feel like I'm pretty good about studying/learning the systems and while 20 years of flying isn't a ton...I'm not exactly a rookie and I had never heard of or thought about this failure mode before.
 
Grum.Man said:
Glad everything turned out ok. I’m a hold out on new tech, sure vacuum pumps fail but as more and more glass panels make their way to market the stories of them failing are starting to add up. Granted most of the time it’s a glitch that sometimes returns fairly quickly and sometimes returns after a master cycle, but sometimes not at all. Until the fleet gets more hours I’ll hang onto my old trusty vacuum pump for now.
Click to expand...
I don't blame people for holding out or not wanting to spend that kind of cash on their panels. This was more of a thought exercise of even dual systems have failure modes and make sure you're ready for them. For me, I would have needed to overhaul/replace my old T&B to be prepared for this failure or it would have gotten real bad quickly IMC.

I legally could have gotten rid of my vacuum AI but I wanted it for redundancy reasons...even with dual independent G5's. Like you bring up...I'm not certain we have enough years/hours behind these things to fully know/understand all their possible failure modes.
 
GRG55 said:
Edit added: I believe he has an auxiliary electric vacuum pump in the plane, so perhaps that is covered with adequate redundancy after all...
Click to expand...

In response to your edit, without knowing what model year and configuration your friends Malibu is, it is hard to say if the aux pump would drive the boots and/or pressurization. My maintenance and flight experience with these airplanes is limited to two; one really old one and one really new one. The old one is Continental powered and has an Aspen upgrade in it so minimal vacuum demand. It has two pumps but despite having two of them apparently only one of them drives the pressurization. Theirs failed this past spring and I had to help a fellow mechanic troubleshoot the problem. The complaint was “no pressurization”.
 
MauleSkinner said:
I was thinking along the lines of dealing with the boot problem before the pumps failed.
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Understand and you are 100% correct. Being that I was cruising along VMC and for sure didn't active the boots it just wasn't in my scan to see that they were inflated. I was toying with the TAS indication page on the IFD and noticed that my TAS seemed to be a couple knots slower than usual and that is when I noticed them. They are now in my scan and I will pay closer attention in hopes that if this ever happens again I can pull the CB prior to losing the pumps.
 
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