AI problems

[Rykymus]

So, I had an AI failure a couple years ago, and replaced the AI with a new one. Then, about a year later, I started seeing a problem with the AI where whenever I climbed above around 8k MSL, the AI started showing a downward pitch that increased as I continued to climb. When I would come back down below 8k, it would go back to normal. My A/P found a crack in the manifold that joins the engine-driven and electrical vacuum pumps to the line that feeds the AI. Repaired that, all was good.

Fast forward to last week (about a year later). I go to move my plane back to the airport closer to me, because I haven't flown it in over two months. The AI wasn't working at all. Looked completely dead. (VFR flight, and my new A/P is at the field close to home.) Shortly after takeoff, the AI starts showing signs of life, and by the time I'm entering the pattern at my destination (about 30 mins after initial engine start) the AI is working normally again.

I suspect the same problem. When they replaced the manifold, they bypassed the bad manifold (marking the elec vacuum pump inop) so that I could fly in the interim. I'm thinking of doing the same now, as a method of diagnosing the issue. My plane is due for its annual at end of May, and I don't really want to take it down now.

Any thoughts?

 

[Radar Contact]

I don't have any experience or thoughts about your current AI problems. I will say that if I was you, I wouldn't spend any more money on them. I have a G5 AI that has been awesome over the past year. If I was you, I would think about going with either a Garmin or Aspen replacement. Whatever you decide, good luck on getting that fixed. One of the worst feelings flying IMC is questioning your AI.

 

[denverpilot]

Does this airplane have a vacuum gauge?

 

[Capt. Geoffrey Thorpe]

Does this airplane have a vacuum gauge?

That would be the first thing to look at - does it suck?
Does turning on the electric pump fix a lack of suck?
When was the last time the filters in the system were changed?
Have you been doing a lot of barrel rolls?

 

[Rykymus]

Vacuum gauge reads in norm with no change when switching to electric pump

 

[Capt. Geoffrey Thorpe]

If you got suck but no AI then it seems to me that you either have a blockage upstream of the AI, or the AI has gone bad (seems more likely if it eventually spun up). But, I ain't no A&P so, by definition, I am wrong.

FWIW: Smoking in the airplane ain't good for gyro bearings - another reason to quit.

 

[arnoha]

I don't have any experience or thoughts about your current AI problems. I will say that if I was you, I wouldn't spend any more money on them. I have a G5 AI that has been awesome over the past year. If I was you, I would think about going with either a Garmin or Aspen replacement. Whatever you decide, good luck on getting that fixed. One of the worst feelings flying IMC is questioning your AI.

I agree with this. After replacing/overhauling all the gyros in my plane, I'm done with that. In July, G5s go in. I did the math...it hurts up front, but if you keep the plane through one engine overhaul cycle, it pays back easily. (Simple version of the math: lose a vacuum gyro about every 500-1000 hours. About $2000 to fix each time. That's around $8000 with a 2000 hour TBO. About $10K to put in the G5s. Factor in the added value to the plane, and you're ahead.)

 

[AggieMike88]

@Rykymus .... if you need any of your vacuum gyro instruments overhauled, I can highly recommend a repair station in Lewisville, TX. They have done work for our club, had a fast turn around, reasonable price, and we are very happy with the results.

 

[mtuomi]

(Simple version of the math: lose a vacuum gyro about every 500-1000 hours. About $2000 to fix each time. That's around $8000 with a 2000 hour TBO. About $10K to put in the G5s. Factor in the added value to the plane, and you're ahead.)

More like 500-800 to fix. You're off by a factor of 3 or 4.

 

[James331]

I agree with this. After replacing/overhauling all the gyros in my plane, I'm done with that. In July, G5s go in. I did the math...it hurts up front, but if you keep the plane through one engine overhaul cycle, it pays back easily. (Simple version of the math: lose a vacuum gyro about every 500-1000 hours. About $2000 to fix each time. That's around $8000 with a 2000 hour TBO. About $10K to put in the G5s. Factor in the added value to the plane, and you're ahead.)

It shouldn't cost near 2k to OH a normal vacuum AI, and you'll never get avionics value back, at least for what the stuff goes for new nowadays.

Simply put, the G5 is a great add on, but don't try to blow smoke in it saving money, it's something you get because you want it.

 

[arnoha]

It shouldn't cost near 2k to OH a normal vacuum AI, and you'll never get avionics value back, at least for what the stuff goes for new nowadays.

Simply put, the G5 is a great add on, but don't try to blow smoke in it saving money, it's something you get because you want it.

So...it cost me $1150 to put in an overhauled AI. The plane was down for three days, costing me about $200 per day in lost revenue. OK, $1850. That's close enough to $2k.

Also, that's the second time the AI has failed over the last 800 hours.

The heading indicator has failed once, costing roughly the same.

The turn coordinator (admittedly, the G5 does not replace this) has failed three times. Yeah, so two failures were due to it being broken out of the box, but it still speaks to the cost and unreliability of gyro-based instruments.

 

[James331]

So...it cost me $1150 to put in an overhauled AI. The plane was down for three days, costing me about $200 per day in lost revenue. OK, $1850. That's close enough to $2k.

Getting it overhauled is less than $500

And your out of service time doesn't really count.

 

[arnoha]

Getting it overhauled is less than $500

And your out of service time doesn't really count.

Where you are and your equipment may be $500, but that's not true here. Labor rates are higher. The equipment is newer. Overnight freight and sales tax take bite, too.

How does it not count? That's money out of my pocket.

 

[James331]

Where you are and your equipment may be $500, but that's not true here. Labor rates are higher. The equipment is newer. Overnight freight and sales tax take bite, too.

How does it not count? That's money out of my pocket.

You're getting it repaired in CA?

I forget the name of the shop, I know Jessie has mentioned them a few times too, but it's just remove the AI and ship out, it gets OHed, sent back and reinstalled, no in state tax for the OH, and swapping a AI shouldn't take a AP much time at all, from your profile pic you're in a 172, so it's nothing fancy just a normal GA vac AI like in most any other plane right?

As far as out of service time, that's a whole nother topic.


But the figures you mentioned are exactly why I decided to pay a broker and sell my last plane in CA vs selling it myself over here.

 

[arnoha]

You're getting it repaired in CA?

I forget the name of the shop, I know Jessie has mentioned them a few times too, but it's just remove the AI and ship out, it gets OHed, sent back and reinstalled, no in state tax for the OH, and swapping a AI shouldn't take a AP much time at all, from your profile pic you're in a 172, so it's nothing fancy just a normal GA vac AI like in most any other plane right?

As far as out of service time, that's a whole nother topic.

But the figures you mentioned are exactly why I decided to pay a broker and sell my last plane in CA vs selling it myself over here.

They were repaired in CA. Well, not really repaired, as that would have taken a very long time. Instead, it was a swap for a yellow tag. As far as CA is concerned, that's no longer pure labor. Now I'm buying something. Waiting to get my same instrument back doesn't make sense, as it just takes too long. I think I was charged two hours labor, so about $250. Another item I forgot is the shop markup on the parts, too.

Yeah, I could do it cheaper on paper. Have it actually overhauled, instead of a core swap. Buy my own parts, so that I'm not charged a markup. Not pay for overnight shipping. Not have someone else manage my plane. Doesn't make sense to do any of that, though. The more of that, the less flying the plane does.

 

[James331]

They were repaired in CA. Well, not really repaired, as that would have taken a very long time. Instead, it was a swap for a yellow tag. As far as CA is concerned, that's no longer pure labor. Now I'm buying something. Waiting to get my same instrument back doesn't make sense, as it just takes too long. I think I was charged two hours labor, so about $250. Another item I forgot is the shop markup on the parts, too.

Yeah, I could do it cheaper on paper. Have it actually overhauled, instead of a core swap. Buy my own parts, so that I'm not charged a markup. Not pay for overnight shipping. Not have someone else manage my plane. Doesn't make sense to do any of that, though. The more of that, the less flying the plane does.

True, however it works out best for your P&L sheet, one size does not always fit all


Just curious, how are you working your 172? Lease back? Photo? Etc

 

[arnoha]

True, however it works out best for your P&L sheet, one size does not always fit all


Just curious, how are you working your 172? Lease back? Photo? Etc

Leaseback. When it's flying, it flies. At $155/hour wet and assuming no major downtime, in excess of 60 hours per month in good weather is common. Bad months where the airplane flies are around 30 hours (bad weather, short months, February is a killer). But nothing kills hours faster than AOG. Not only are those days gone, but the renters get spooked. They either believe it's a bad plane or they don't trust that it will be available for when it's booked. They run away fast and don't come back if you start cancelling their bookings. Hours in the next month or two also go down until they forget. (If you read about my thread about the three weeks it spent down for a fuel gauge needle falling off...that was driving me batsht crazy.)

I did get one good break: The club had a tie-down open up right next the club's back door onto the ramp. Yeah, not having to walk out into the regular tie-downs (I was on S row at PAO before.) made a difference, too. Convenience drives up hours as well. (Other weird stuff did, too... When on S row, my tiedown was under a streetlamp. That drove up night hours.)

All the SP's at PAO fly like that, for the most part. This despite the fact that there are 21 SP at my club alone and 30 at the airport available for rent.

 

[mtuomi]

They were repaired in CA. Well, not really repaired, as that would have taken a very long time. Instead, it was a swap for a yellow tag. As far as CA is concerned, that's no longer pure labor. Now I'm buying something. Waiting to get my same instrument back doesn't make sense, as it just takes too long. I think I was charged two hours labor, so about $250. Another item I forgot is the shop markup on the parts, too.

Yeah, I could do it cheaper on paper. Have it actually overhauled, instead of a core swap. Buy my own parts, so that I'm not charged a markup. Not pay for overnight shipping. Not have someone else manage my plane. Doesn't make sense to do any of that, though. The more of that, the less flying the plane does.

I'm actively following your blog, and I keep noticing that you are being taken to the cleaners all the time with very high markups and poor airplane management.
Based on my own ownership experience, I would argue the plane sits less AOG with an active owner. Whether it's worth it or not, depends on how much you value your time. To me it was half the fun of ownership.

btw. You're not counting the 30-60 days AOG in lost revenue with the G5 install - avionics installations never go 100% as planned.

Out of curiosity - why do you ground the plane with a failed AI? Would it make more sense to offer it to renters with a slight discount during that time - it's not needed on most bay area flying anyway?

 

[arnoha]

I'm actively following your blog, and I keep noticing that you are being taken to the cleaners all the time with very high markups and poor airplane management.
Based on my own ownership experience, I would argue the plane sits less AOG with an active owner. Whether it's worth it or not, depends on how much you value your time. To me it was half the fun of ownership.

btw. You're not counting the 30-60 days AOG in lost revenue with the G5 install - avionics installations never go 100% as planned.

Out of curiosity - why do you ground the plane with a failed AI? Would it make more sense to offer it to renters with a slight discount during that time - it's not needed on most bay area flying anyway?

Heh, you are correct about not counting that time. I should have included that. It's currently stated to be three weeks, so taking that at face value, it's about $3000. So, good catch.

The blog is not as actively maintained as I'd like. I need to remember to add more pictures. That's on my list of things to do.

Honestly, the plane is usually AOG because of me, as opposed to the other way around. I have to learn some lessons the hard way...I had that happen with the fuel senders the first time around. I insisted on delaying the repair and getting the CiES senders, as I was so frustrated with the constant repair of the Rochester ones. That put the plane down two weeks while I futzed around trying to get the senders and the fuel gauge. In the end, unable to get it to happen fast enough, I finally caved and put in a new Rochester sender and put the CiES senders o the shelf.

Same this time around, but I was more determined. I actively worked the problem to get the damn CiES senders in even harder and it still took three weeks. Oddly, it would have been cheaper to put in the ridiculously overpriced Rochester/Cessna fuel gauge back in. Cheapest would have been an Aerospace Logic FL202 to the stock senders. That part is stocked by Aircraft Spruce, unlike the FL202D I installed and had to have shipped from Canada.

There have been other cases where my involvement and inexperience has delayed everything. I'm trying to learn to move at an aviation pace, but it's so much slower than I'm used to and it drives me nuts. Things that should be fast just aren't and unexpected things are quick. I can get just about any Cessna part tomorrow but other stuff takes a week! (Engine monitor, month and a half for parts delivery. WTF??)

As for why grounded with a failed AI...depends on the club and their insurance. Our club has really low insurance rates given the high safety record (tarnished lately by stupid stuff on the ground), and this is one of those items. The rates here were $2000 per year lower than the last club I left.

Overall, I'd love to be highly involved with the plane. But I just can't. Two kids. Full-time job. It means I get milked for cash at times because I don't have the time or energy to fight it. So, I take the projects that make sense for me to be involved in. The panel redo. The fuel senders. But leave most of the mundane to the shop to handle.

Could I do it better and cheaper? Probably. Do I like owning a plane well enough to keep doing it? Yeah, but ask me again next year...