Bravo Squawk Sheets

[johnggreen]

Bravo Owners,

When I asked that Bravo owners be given their own section in Mooneyspace, my goal was simple and obvious; to have a forum that specifically addressed Bravo maintenance and operation issues.  I have been very pleased with the results.  We have certainly had a sharing of info that has been beneficial to date. 

The most interesting thing to me is that there has been no deluge of issues, and certainly we haven't turned up any achilles heal of the airplane.  As I have learned in my seven years of ownership, the Bravo is a very reasonable plane to operate and fly from every aspect.  This reality flies in the face of the "aviation urban myths" about Bravo maintenance issues.  The Bravo is straight forward with all operational/maintenance pertaining to its "systems".  I think it fairly states the operationg of the Bravo to simply point out that it has lots of systems and dual everything.  Every system, be it turbocharging, oxygen, TKS, dual alternators, dual vacuum systems, speed brakes. extensive avionics (for most airplanes) etc.  It does share some quirky systems common to all Mooneys, the landing gear donuts and flying tail to mention two.

Forgive my wordiness, but I think the point I was addressing is valid; Bravo maintenance is nothing special or unusual, or particularly unique compared to a M20C or V tailed Bonanza.  The systems simply create a lot of areas to maintain.

Since the opening of this Bravo section, I have had an idea and would like the input of other Bravo owners.  I would propose that each of us review our logs and note any "special" maintenance issues that we have had to address.  We could simply list each and every item addressed and truthfully that would not really be a big task.  It would be interesting, for instance, to see how often we change tires, replace donuts, etc., but I also think that each of us will probably uncover items that are not everyday issues that we could high light for other owners.

Personally, starting sometime this week, I'm going to go through my logs and list every single item of maintenance ever performed on my airplane.

Think about this and offer suggestions, or just start listing your own log entities.

I would suggest that you create a document that you can attach and email.  I would offer to receive them and compile a"master" list of items that Bravo owners address.  From this, we may find a few items that we would each want our mechanics to eyeball at annual time.

This may be an excellent start for a "new", updated article on the Bravo by the Aviation Consumer.  I suspect the would love for someone to do the leg work for another article.  In fact, I'll contact them about exactly that.

What are your thoughts?

Jgreen

[Awful_Charlie]

I see the previous owner of mine got through 3 turbos in less than 1200 hours.  One of these was due to 'ice damage' and prior to the Mooney mod to the air filter assembly.

He also suffered from lots of batteries, but there is no note as to the fix, as the current ones I am using are 4 and 6 years old, but I do maintain them with a battery minder in the two years I've owned it.

Maybe he made extensive use of the speed brakes, as they were frequently removed for servicing, repair or overhaul.  I use them occasionally, but prefer to plan my descents so I don't need them (not always easy for me when I return from the east, as I have to lose 5000' in 20nm, but don't suffer that from my usual return from the west or north)

While under warranty it got new engine instruments, an intercom, fuel tank senders, fuel pump.  Since then there has been another fuel pump, a cowl flap motor, starter, gyro overhaul.  Other than that, it seems fairly GA generic - lot of plugs, filters and oil, occasional vacuum pump.  Coming up soon I've got the O2 cylinder replacement and regulator overhaul, and possibly an engine - there is a thread in this forum about that

Ben

[johnggreen]

Ben,

If you get a chance, put that chronologically and with engine hours in a document and attach it to an email to me.  The replacement of turbos would indicate that the previous owner wasn't allowing the turbo to cool down before shut down.

My airplane, for the hours of use, 1000, may be a little low on replacement of wear items like you noted.  I fly 3+ hour cross country almost exclusively.  Not much start up, shut down, landings etc.

Good info and hopefully you will have time to detail it.

Jgreen

[Skywarrior]

The replacement of turbos would indicate that the previous owner wasn't allowing the turbo to cool down before shut down.

There are a lot of people who poo-poo that idea. Then again, maybe you're right. In any case, mine is always cooled down by the time I get to my hangar.

I would bet that the more-significant reason is simply running the thing too hot inflight. If you're running high power at high altitude, you need to have your mixture around 200 ROP if you can't run LOP.

Chuck M.

[johnggreen]

Chuck,

I'm with you as I just posted on another Bravo thread.  I think the cool down is beneficial but don't want to belabor or argue the point.

Now, as to the "squawk sheet".

It was raining today, thank Heavens, so I stayed at home and took care of business on the phone and computer.  I also pulled my Bravo logs and detailed every significant entry of maintenance the airplane has had in 1000 hrs of operation.

I did not include "adjustments" or Service Bulletins etc.  We all have that.  I put in everything that broke, as well as replacement of most wear items.

Overall, I was pretty impressed with how little has been done to the airplane.  A lot of the replacement of wear items was premature, but that's me.  I try to learn the MTBF, mean time between failure, of all wearable items and replace them at about 75% of the MTBF.

Four things stood out.  Now, remember, that I bought the airplane when it was four years old and had 400 hours on the hobbs.  Of the things that stood out, all all started before my ownership.  Two were never fully satisfied until after I owned the airplane.

The first item is that the airplane initially went through batteries about every two years.  I actually think this may have been the owner's fault for not using #1 and #2 on alternate flights.  Then, apparantly, he didn't understand to check to be sure the fuse on the trickle charge between the systems wasn't blown.  That fuse is a weak spot, but at least a simple weak spot to deal with.  Also, take note that there is one light in the cabin that will stay on when the master is off.  It's right at your left hand and easy to bump on.  it will kill a battery in about three days.

Secondly, the TKS system leaked.  It was "worked on" at least three times before I got the airplane.  When it started leaking on me, rather badly during a cross country, when I got home I pulled the belly to see for myself.  I called the company and they PDF'ed me a diagram of the system and were very helpful with figuring out the problem.  The problem was that the shops that had worked on it before, including a MSC, did not use the correct parts.  It was nothing but leaking fittings, but the fittings are not generic.  Only factory parts will work and must be installed with special factory supplied swedges; which cost about $120 for each size.  I fixed it, took it to my shop, not a MSC, and went over all I had learned.  They inspected my work and signed it off.  I gave them the tools for the swedges.

Third.  The airplane had three master cylinders installed before I got it.  I had troulbe too.  The MSC "fixed" it to no avail.  It was soon after that I started using my old shop.  Kevin Rushing worked on it, got the system properly bled, which is a chore, and the brakes have worked perfectly now for over 400 hours.  We did put on new brake pads at 768 hours. 

Finally, the right tank started leaking at about 200 hours.  It was repaired three times, once by a shop in St. Louis, and twice by the MSC, one as a pre-buy and once after my ownership.  It started leaking again.  This time, my shop, resealed the tank, apparantly correctly, and I've had no further issues.

I did replace #2 cylinder at 879 hours.  It was a worn valve guide and most likely this was the result of a manufacturing defect.  No big deal.

I will also note that the speed brakes have been rebuilt twice.  It seems that comes about every 500 hours.

Everything else is run of the mill.

To date, considering the number of systems this airplane carries, it has been a very reliable and "relatively" economical aircraft to own.

Jgreen

 

 

[Awful_Charlie]

John

I'll have to get the log books from the hangar and go through them again, as the spreadsheet I have put together so far only lists the highlights (eg "Turbo replaced") and not any reason, but I remember one of them was marked "due to ice damage".  They are however an hour away, and I'm off the the UK the coming weekend, so you won't see a spreadsheet for a couple of weeks at best.  I also remember there was a repair to the port wing flap area due to corrosion at some point.

Most of my flying is 2hr+ trips too, but with the occasional short trip to keep regular usage, or when customs requirements mean I need to make an intermediate stop (such as going to the UK this weekend).  I'm a bit sceptical about the turbo cool down requirement too - I can see it might be more beneficial if you have been doing circuits, but after a long descent everything is nice and cool on touchdown.  The JPI sees the CHTs rise after landing, but my suspicion is that for the turbo, it is probably the oil temperature on exit of the turbo that is critical - the reasons I have seen given for doing the cool down relate to oil coking on the turbo shaft.  As the turbo is a large lump of metal, with cooling provided by the surrounding air, the induction and the oil, my take is that the induction housing is cooled quite quickly at low power settings (cold air in, no compression required), the exhaust side is directly related to the EGTs/TIT, but the centre section (which is quite a lot of mass) is only cooled by the oil flow, and getting the heat out of here is more difficult due to the small oil flow through it, but some will be done by conduction to either side.

I too had TKS leaks, one or two of which required new fittings, but the majority were due to loose untions (and no safetys) or in a couple of cases, because plastic tape had been used in an attempt to seal them!  I've got the system tight now, but did have to replace one wing panel last year as it had internal damage (I bought it like that), which of course meant yet another TKS filter too (why on earth are these so expensive?).  Cost to fix the leaks was trivial, just a lot of my time, and a once over by my A&P.

I monitor component lives too, but am less generous when it comes to TBO replacement - depending on what it is, I might replace it at the following annual (o2 cyllinder expires in November, I'll replace it in the 2013 annual), or just get the part in and put it on the shelf (my primary vac pump has 870 hours on it, I have a new one on the hangar) - it depends on how critical the part is to despatch and flight safety (for instance I have a spare pitot heater/head in the hangar)

Compared to the 1968 Arrow I ran for 10+ years, maintenance is more expensive, but then it didn't carry many of the systems the Bravo does, and was nowhere near as capable (which was the reason to change - when I moved to Switzerland I needed something with FIKI and turbo capability), but running a 40 year old airframe also provided its challenges.

Ben

[johnggreen]

Ben,

I too have always understood that the turbo cool down issue was oil related.  At any rate, it is almost never an issue as my TIT's stabilize in less than a minute.

I think it will be very interesting if we can collate maintenace data on at least a handful of Bravos.  If we see a particular issue pop up numerous times, then it gives us a heads up as to what to watch.

Today, I had my TIT probe replaced as I suspected I was getting slightly lower readings.  It was definitely corroded.  The first one was replaced at 400 hrs. and this one had 600 which is toooooo long.  Had I been in the habit of using higher power settings, I would have been running my engine on the brink of the limit of temps.  Thankfully, I don't.  In fact, my customary use of lower power settings is probably why I didn't notice the worn TIT probe sooner.

It must be a different world flying in Europe, but certainly interesting considering some of the scenery.  I think my wife and I are coming over before too long, probably to Paris.  We'll keep in touch and maybe we could fly over, or train over, for lunch one day.

Take care.

Jgreen

[Awful_Charlie]

John

I've not forgotten this, just seem to have vastly underestimated to time required!  I've got a fair amount done, and will continue to get through it.  If you're desperate, you can have where it is so far, but there will be more to come in due course.

If you happen to be in Europe, let me know, it's always good to meet other Mooniacs (Paris is about 4-5 hours away on the train from here, GA airports near Paris aren't that near to the centre)

Ben

[johnggreen]

Ben,

No rush.  I was able to compile my "squawk sheet" in less than an hour.  I'm not speaking of normal maintenance, what I see as beneficial is what the airplane experienced as "Mean Time Between Failure" of wear related items (turbos, mags, vacuum pumps etc.) and failures that may not be easily detected or expected (like exhaust cracks or engine mount failures/cracks).

One thing that made mine easy was that my logs are "neat".  I didn't have any instances where the shop made a lot of useless entries so as to justify a larger shop bill; something that I have seen many times in my flying career.  Also, almost all my entries were typed from computer entries so I didn't have to try to read the hand writing of a gramatically challenged mechanic.  No insult intended to mechanics by that.

When you get and outline it, you may find it pretty simple.  In fact, if you will give me an email address, I'll send you my list.

Jgreen

[carqwik]

My understanding of the five minute cool down for the turbos has to do with the bearings in the turbocharger itself and is unrelated to the oil temp or CHTs.  Turbo chargers run at very high RPMs when a lot of boost is required at higher altitudes...and the entire unit gets hot (like glowing orange).  When you come back to earth, the bearings still remain hot and the goal of the cool down is to keep oil moving past the bearings to wick away heat so at shut down the bearings don't "coke" the oil. 

I will not claim to have first hand knowledge of this - but I practice the five minute cool down which is usually a combined time of taxi plus idle.

[Awful_Charlie]

On the turbo cool down item, Kelly themselves recommend 'an additional 2 minutes after taxi' (see http://www.kellyaerospace.com/articles/KA_Turbocharger.pdf ) but I fail to see how such a generic instruction can be valid when they don't differentiate between parking just off the runway (or what about landing at an altiport, when it takes full power to taxi to the top of the runway?!), or a protracted taxi to a remote stand.  I normally just taxi in, check all the temps, shut down the lights & avionics, complete the paperwork, and if that seems to all be done within a minute or two of landing, maybe give it another 30 seconds.  Thing is, I'll only know that it wasn't long enough when I get a coked turbo!

[johnggreen]

As for cool down.

My TIT's fall over 150 degrees from the point that I stop and go to full idle.  My CHT's are usually stabilized during taxi, and I don't see any change after going to full idle at the parking spot.  An aircraft engine has multiple areas of heat; the turbo being probably the hottest.  We have no guage to measure turbo temp, only the temps of the exhaust gases entering the turbo.

I have used the same mechanic shop for 10 years and have developed a good deal of faith in them.  The owner, Kevin, is a very experienced fellow but not highly opinionated.  Ask a question and he'll give you parameters; not "Well, this is the way it is."  Kevin watches his customers and the way they handle their engines.  He will make suggestions, but if you don't want to take it he will let you have it your way without comment and fix what you break.  He has, over the years, made several comments to me about different airplanes, the maintenance required by them, and the way they are "handled" by the owner/operator.  He sees a very high correlation to turbo issues related to cool down.  And again, if you don't want to do it, he will gladly replace your turbo and make the required exhaust repairs every few hundred hours.

Frankly, this is the way I look at it.  The manufacturer built the engine and the mechanic deals with its problems.  They see it everyday.  I trust both of them with my life everytime I crank my engine and I will rely on their educated and experienced opinions.  I don't care how other pilots and owners manage their engines.  The supposed ownership of an airplane (we don't always know for sure on this site) and the access to a computer, hardly qualifies them to lecture me on how to manage my engine.  

Jgreen