The Bravo: One Capable Airplane

[KSMooniac]

Don, I'm a bit confused about your history on the Rocket.  Did you have it overhauled by a shop in Florida and it wouldn't run well LOP despite GAMIjectors, and after 50 hrs you pulled all the jugs?  Were they ECI cylinders from the overhaul that had the problems, or did you replace them with new ECI cylinders?

Sounds like a happy one now, and I expect you'll have a long, efficient service life with it.

[donshapansky]

I bought the Rocket in FL with 50 SMOH, I think it took over a year to get to 50 hrs so looking back I think corrosion started then. I bought the aircraft in June 2008 and flew it until March 2010 rolling up 750 hrs all the while fighting oil analysis issues that indicated wear problems then finally exhibiting the traits mentioned.

I installed the GAMI's on the way home from FL after purchase and never could get it run acceptably smooth or keep the TIT in range. new EDI's were installed at the major OH. There was no need to replace the cylinders just fix the corrosion issues that were done with a cylinder overhaul, new pistons, rings, valve guides, valves, springs, retainers etc. etc.

I think it will live a long time now, but it indicates that LOP requires a healthy engine to make it a pleasant operational experience.

[KSMooniac]

Quote: donshapansky

I think it will live a long time now, but it indicates that LOP requires a healthy engine to make it a pleasant operational experience.

[jetdriven]

A LOP mag check or induction leak test will uncover problems long before the ROP method will (IE, an overheated and ruined cylinder)

[aviatoreb]

Quote: jetdriven

A LOP mag check or induction leak test will uncover problems long before the ROP method will (IE, an overheated and ruined cylinder)

[Jvancecpa]

No.  Do an in flight mag check.  It is explained well on the the BeechTalk website.  

[KSMooniac]

In a nutshell, while established in LOP cruise you simply do a mag check just like the typical pre-takeoff check.  The difference is that while producing cruise power with a LOP mixture setting, this is a much "harder" test of the ignition system and if you have any weaknesses in a mag, harness or plug then they will be exposed much earlier than they would under a conventional low-power mag check on the ground.

One major caveat though is if you switch to a single mag and your engine shuts down, DO NOT SWITCH BACK TO BOTH immediately.  The engine will be pumping air and fuel due to the windmilling prop, and this unburned mixture will migrate to the exhaust and can lead to a yard sale of your exhaust system.  If the engine quits, move the mixture to ICO so that no more fuel will be pushed into the cylinders and exhaust, wait for a couple of seconds, switch back to both, and then slowly enrichen the mixture until it starts firing again.

[jetdriven]

Thanks for covering that, Scott.  A LOP mag check in flight is not a normal operation for me, and although safe, needs to be briefed and all "what if" situations covered.   I pull the throttle back to between halfway and 1/3rd if recovering from a bad LOP mag check or running a tank dry to prevent overspeeding the prop when the engine comes back online.

It really is no big deal to perform, and it will tell you if you have a plug with high resistance  (over 5K ohms on those Champions) or an ignition lead breaking down. It will also tell you if you have split mag timing too.

[Parker_Woodruff]

Quote: KSMooniac

 

One major caveat though is if you switch to a single mag and your engine shuts down, DO NOT SWITCH BACK TO BOTH immediately.  The engine will be pumping air and fuel due to the windmilling prop, and this unburned mixture will migrate to the exhaust and can lead to a yard sale of your exhaust system.

[Steve Dawson]

Resurrecting this old post, Great info from John Green, Scot, Andy and everyone about the details of running the Bravo. I just tried a the power settings that John mentioned here and another one of his posts with almost the same results. It's taken awhile to get the plane rigged properly but now it's flying straight and close to the same speeds with the power settings shown he described. I had the engine balanced (.3 ifs @2300 RPM) and it still has a bit of a vibration at 2300 RPM when flying so I may replace the engine Lord mounts and see if that helps, but I'm very happy with all the great info in these old posts.  

[LANCECASPER]

1 hour ago, Steve Dawson said:

Resurrecting this old post, Great info from John Green, Scot, Andy and everyone about the details of running the Bravo. I just tried a the power settings that John mentioned here and another one of his posts with almost the same results. It's taken awhile to get the plane rigged properly but now it's flying straight and close to the same speeds with the power settings shown he described. I had the engine balanced (.3 ifs @2300 RPM) and it still has a bit of a vibration at 2300 RPM when flying so I may replace the engine Lord mounts and see if that helps, but I'm very happy with all the great info in these old posts.  

You may already have fine wire Tempest plugs, but if not that would be my first suggestion. It certainly helped the last Bravo I owned run smoothly. You mentioned you "had the engine balanced" - are you referring to the prop?

[Steve Dawson]

Thanks for the information on the Tempest fine wires. They're next on the list for the next thing to do. I have a tank reseal booked for this month so I'm watching my budget for now. Hopefully this will work because I didn't want to go through changing the engine mounts yet. Just out of curiosity, after you installed the fine wires, did you notice a difference in RPM drop when doing a mag check?

It was a dynamic engine/prop balance done so technically it was the prop that had the weights and the engine wasn't touched. 

[carusoam]

@johnggreen really liked his Bravo….

And spent a fair amount effort detailing trying to run it LOP…

Hard to run it LOP… when you prefer flying fast….   
 

So…. I sent John a ping… to see if he is still MS connected!

Best regards,

-a-

[Rick Junkin]

Here's some JPI 830 data from my flight from Gatlinburg to Alton IL yesterday that shows some real numbers for a Bravo running 2200/30, 13.7gph and 40 degrees LOP at 8,000 feet.  This power setting consistently yields an indicated airspeed of 143kts which gives me 180KTAS+/- in the mid to upper teens but the westerly winds at altitude yesterday were horrendous so I settled for 160KTAS at 8K. My #5 CHT is from a ring probe and reads 50 degrees lower than the OEM gauge, so add 50 to the #5 CHT value.

For reference I have GAMIs with a spread of 0.3gph at peak, Tempest fine wires (URHB32S) and a dynamically balanced prop/engine. This power setting is very smooth, much quieter and I believe less fatiguing. I'm meticulous with my maintenance and so far it is really paying off for me.

Cheers,
Rick

[Steve Dawson]

Impressive Rick,

When did you install the fine wires and did they help with getting your engine to run LOP and run smooth? 

[Rick Junkin]

15 minutes ago, Steve Dawson said:

Impressive Rick,

When did you install the fine wires and did they help with getting your engine to run LOP and run smooth? 

The airplane had Champion massives and stock Lycoming injector nozzles when I bought it in 2016. I had a GAMI spread of about 0.7gph and was able to run about 20 degrees lean of peak but it wasn’t terribly smooth. It would run uncomfortably  rougher as I continued to lean past 20 degrees LOP. I installed the fine wires about 6 months later.
 

I immediately found the engine started easier and ran smoother but it wasn’t until I installed and tuned the GAMIs (4 iterations of injector swaps) that I was happy with how the engine was running with a 0.3gph spread. I am able to lean the engine to about 100 degrees LOP with it still running smoothly and then it starts to stumble from too lean a mixture. 50 degrees LOP is the point of diminishing return and only required for “higher” power settings. With my settings of 2200/30, 20 degrees LOP is plenty but I found I can run 40 degrees LOP with minimal speed loss and save a little more gas and keep the cylinders about 10 degrees cooler.

Cooler is better. Within reason of course.

Cheers,
Rick

[Steve Dawson]

Thanks Rick, very helpful 

[Steve Dawson]

Update on my Bravo and the vibration problem, I just had the engine mounts replaced with new Lord mounts and now theres quite a positive difference.  It's actually very smooth throughout all the engine RPM ranges. When the shop replaced the previous mounts they were found to be askew in the engine mount so that the rubber didn't fit properly in the mount and we also found the engine mount bolt was loose.  

Flew from FXE up to GSP and tried the range of RPM's from 2200 to 2550 and it feels great now. 

 

[carusoam]

Great follow up Steve!

Let’s see if @BDPetersen is around…

He was thinking about changing out some engine donuts while he was in there…. 

Best regards,

-a-

[BDPetersen]

It’s an opportunity I may take. I perceive a hint of sag that could be fixed. Lord vs Barry?

[Tommooney]

What is typical lifespan of engine mounts? I'm pushing 20 years .

Thanks

Tom

[carusoam]

11 hours ago, Tommooney said:

What is typical lifespan of engine mounts? I'm pushing 20 years .

Thanks

Tom

There are so many variables involved….

From heat, and compression, to being soaked in oil…. How much they get used engine hours…

They are designed to get replaced at engine OH….

 

At 100hrs every year… 20 years is getting long in the tooth…

 

Often changed out when sag is measurable… or opportunity arises…

 

pp thoughts only, not a mechanic…

-a-

[Steve Dawson]

From what I've read and heard Berry mounts aren't approved for Bravo's/TLS's and I believe there's an SB on them as well as it being stated in the service manual. 

[Rick Junkin]

1 hour ago, Steve Dawson said:

From what I've read and heard Berry mounts aren't approved for Bravo's/TLS's and I believe there's an SB on them as well as it being stated in the service manual. 

Uh oh, I guess I missed that. I had Barry isolators J-9613-82HA BARRY MOUNT installed on my Bravo last December. I'll look for it, but can you  @Steve Dawson point me to the references you're using? I thought I had done my research and determined these were what I needed but I'm open to education. thanks in advance!

Cheers,
Rick

[Rick Junkin]

Here's an excerpt from the original TLS Service Manual, section 71-20-00, pertaining to the engine mount isolators.

Summary is Barry mounts were not used in production (this detail is included in the updated service manual for the M20M DX/GX) but Lord or Barry isolators can be used as long as you don't mix components from both manufacturers.

I clipped the original service manual because it contains the Barry component part numbers in italics. The Barry components are referenced in the updated manual but for some reason the italicized component part numbers fell out of the update and aren't in the text. J-9613-82 is the Lord kit number, J-9613-82HA is the Barry kit number. You need 4 of these kits for a complete installation.

 

Here's a portion of the recommended Overhaul and Replacement Schedule showing engine isolator replacement recommended at 10 years. Keep in mind these are recommendations, not requirements.

Cheers,
Rick

Edited June 3, 2022 by Junkman
Added recommended Overhaul and Replacement schedule from maintenance manual.