Maintenance costs on Bravos

[dzeleski]

2 minutes ago, hazek said:

@donkaye, MCFI Could you maybe point out some of the gotchas that one might miss? Being based in Europe I have no clue who could be a reliable expert on the Bravo available to me. The instructor who signed me off is a captain on a 747, with extensive knowledge in general and also his own high performance light aircraft but I admit not Bravo specialist, and he was willing to sing me off. I must have displayed some competency. But you are right, I don't know what I don't know. So please, if you have any advice I'd happily receive it.

I own a J not a Bravo but ill bite. You own an airplane that is exceptionally capable, its also exceptionally capable of killing you. If you have not started your IR please do, once you do Dons comments will probably make a bit more sense. The first 10 hours of IR training could/will save your life if that airplane gets you into a situation you were not expecting.

The comment for me that sticks out is saying that a 172 isnt that different then a Bravo. They both have wings, but thats about as similar as you are gonna get IMO.

[hazek]

34 minutes ago, dzeleski said:

The comment for me that sticks out is saying that a 172 isnt that different then a Bravo. They both have wings, but thats about as similar as you are gonna get IMO.

I didn't make a comment like that, now did I?

Edited April 21 by hazek
missing words

[PT20J]

One area of confusion with LOP operations seems to be sorting out theory from technique.

What makes the engine go is pressure from combustion in the cylinders doing work on the pistons. For a given power (say 65% of rated power) the BMEP (Brake Mean Effective Pressure - the average cylinder pressure) is going to be the same independent of fuel/air ratio. The primary advantage of LOP is that it is more efficient - less fuel is burned per horsepower produced (this has the beneficial side effect of extracting more heat from the chemical combustion process as useful work so that less heat is rejected to the cylinder head). 

However, for the same MAP (manifold absolute pressure), more power (that is, greater BMEP) is available ROP than LOP. Another way of looking at it is that more MAP is required to develop the same power LOP than ROP. If you increase the MAP (airflow) LOP then the fuel flow must increase to maintain the same fuel/air ratio.

How you do all this is a matter of technique of which there are several.

[Ragsf15e]

I’m planning on flying my 252 this week. I will post a picture of the g3x at 65% lop and 65% rop by the book and we can all see what the difference in TAS and/or temps are.  From my experience, the TAS will be the same and the CHTs will be lower for LOP.  TIT will be higher.

[PT20J]

21 minutes ago, Ragsf15e said:

I’m planning on flying my 252 this week. I will post a picture of the g3x at 65% lop and 65% rop by the book and we can all see what the difference in TAS and/or temps are.  From my experience, the TAS will be the same and the CHTs will be lower for LOP.  TIT will be higher.

The G3X %power indication seems pretty accurate LOP but may overestimate power ROP. 

The best way to be sure you have the same power LOP and ROP is have the same airspeed since the airplane doesn’t care how the power is produced. 

[Rick Junkin]

46 minutes ago, Ragsf15e said:

I’m planning on flying my 252 this week. I will post a picture of the g3x at 65% lop and 65% rop by the book and we can all see what the difference in TAS and/or temps are.  From my experience, the TAS will be the same and the CHTs will be lower for LOP.  TIT will be higher.

Those will be good data points, thanks!

In the Bravo community we have the issue of the POH not speaking in terms of % power. Actually this is a non-issue as far as general aircraft operation; it only becomes an issue when we want to do something like the comparison you are about to do with pre-determined power parameters. Then we have to get into the charts in the Lycoming manual and do the calculations, because it doesn’t speak directly to % power either. Not a big deal, just requires some chart reading and math.

The other way for us to do it is to set LOP power, see what airspeed it gives us, and then go ROP and search for the power setting that results in the same airspeed. Using this method requires no book work.

[Rick Junkin]

3 hours ago, PT20J said:

The best way to be sure you have the same power LOP and ROP is have the same airspeed since the airplane doesn’t care how the power is produced. 

3 hours ago, Rick Junkin said:

The other way for us to do it is to set LOP power, see what airspeed it gives us, and then go ROP and search for the power setting that results in the same airspeed. Using this method requires no book work.

Haha! Great minds and all that.

[dzeleski]

9 hours ago, hazek said:

But back to the topic. I'm on my first year of ownership. Well, co-owernship. I have no idea yet what the costs are, especially since it seems like the plane has been neglected for non essential things and has many little squawks that need fixing, not to mention it could do with a facelift in all areas. As for flying it as a low time, VFR only for now, pilot, as everyone says, if you can fly by the numbers, have a precise plan how to manage the engine and the speed, it's ok. In the beginning one can also just simply fly a bit less efficient and slow down much sooner before entering a traffic pattern and then it's not much different than flying a C172. Still a bit faster of course, but with gear down at 20" I'm usually at about 100kt which is perfectly manageable speed for VFR traffic patterns. I started with about 160TT and have now 40h on it and I find it perfectly manageable to fly and I consider myself safe. I also didn't need some extensive training to get checked out, only a couple of hours. But I did spend a lot of time reading about the plane and flying an Ovation in a sim at home to get a feel for timings before.

 

1 hour ago, hazek said:

I didn't make a comment like that, now did I?

You did. See the bold underlined text above.

[Rick Junkin]

13 minutes ago, PT20J said:

The G3X %power indication seems pretty accurate LOP but may overestimate power ROP.

Hmm. Mine appears opposite that, where LOP %HP is overestimated by the G3X. I set the LOP fuel flow that yields 70% and the G3X shows 73%. I haven’t experimented with ROP settings yet.

[PT20J]

9 minutes ago, Rick Junkin said:

Hmm. Mine appears opposite that, where LOP %HP is overestimated by the G3X. I set the LOP fuel flow that yields 70% and the G3X shows 73%. I haven’t experimented with ROP settings yet.

To be honest, I really don’t pay that much attention to it. George Braly told me that he thinks that all the engine monitors %power indications are inaccurate (except, of course, the proprietary one he developed for Cirrus for the Perspective )

[hazek]

13 minutes ago, dzeleski said:

You did. See the bold underlined text above.

I'm glad we cleared up the fact that you said:

1 hour ago, dzeleski said:

The comment for me that sticks out is saying that a 172 isnt that different then a Bravo.

And what I actually said is:

13 minutes ago, dzeleski said:

In the beginning one can also just simply fly a bit less efficient and slow down much sooner before entering a traffic pattern and then it's not much different than flying a C172.

Btw as you can see by my reaction, I don't like it when people misrepresent my words.

Edited April 21 by hazek

[Rick Junkin]

1 minute ago, PT20J said:

To be honest, I really don’t pay that much attention to it. George Braly told me that he thinks that all the engine monitors %power indications are inaccurate (except, of course, the proprietary one he developed for Cirrus for the Perspective )

I’m with you. I’m a simpleton when it comes to power management. I did the research and experimentation to find a cruise power setting I like and that’s the one I use. The numbers are always the same for the most part and it takes less brain bytes to plan and manage. 

[Pinecone]

4 hours ago, hazek said:

If this was a response to me, then I think you are mistaken. Yes, obviously if you increase fuel flow while LOP, you would get more power. But you would also get higher EGTs and higher TIT, which could be higher than desired. At some power setting, these temperatures would simply be too high. So, there’s a clear limit to how much power you can achieve while operating LOP and still keep temperatures within safe limits. This is only feasible with a turbocharged engine, as without a turbo, typically at cruising levels there isn’t enough air available—adding more fuel would just push the engine back to the ROP side once higher up.

However, the big mixture pull doesn’t address the issue of higher temperatures. Its sole purpose is to reduce the time spent at peak cylinder pressures—that’s what the technique is designed for. By definition, LOP means operating lean of peak EGT. If we increase FF, the peak EGT will absolutely rise. This means that, in absolute terms, a relative setting like 35°F LOP will result in a higher absolute temperature than it would at a lower power setting, no matter how you reach that LOP point. Since going further lean of peak EGT than about 50°F is impractical—due to inefficiency and the engine likely running too roughly—we’re limited in how high our LOP power setting can go while keeping temperatures in the green. Whether you use the big mixture pull or another method, there’s an LOP power cap beyond which the engine runs too hot for the turbo and exhaust system.

If you increase the fuel flow from a given setting, you will be running less LOP or even move into ROP, so you also have to increase manifold pressure to keep the same amount of LOP.

The point I was making about the BMP was that you do not spend enough time in the range of peak EGT to see the full effect, so the temps don't rise as much as if you did a slow lean to peak.

How LOP you can go depends on your engine and fuel injectors and such.  But once LOP, power is based on fuel flow.  Nothing else.

I can run 29.5 inches or 32 inches, both at 10.1 GPH and get the same speed.  But the 32 inches is more LOP so low CHTs, but possibly higher EGT due to the slower burn rate.

[Pinecone]

3 hours ago, PT20J said:

To be honest, I really don’t pay that much attention to it. George Braly told me that he thinks that all the engine monitors %power indications are inaccurate (except, of course, the proprietary one he developed for Cirrus for the Perspective )

My JPI 830, when LOP, used 13.7 HP per GPH to give % power.

ROP is a real crap shoot about how they figure that out.

[donkaye, MCFI]

On 4/21/2025 at 8:36 AM, hazek said:

@donkaye, MCFI Could you maybe point out some of the gotchas that one might miss? Being based in Europe I have no clue who could be a reliable expert on the Bravo available to me. The instructor who signed me off is a captain on a 747, with extensive knowledge in general and also his own high performance light aircraft but I admit not Bravo specialist, and he was willing to sing me off. I must have displayed some competency. But you are right, I don't know what I don't know. So please, if you have any advice I'd happily receive it.

Questions to ask yourself: 1. What control is primary in any phase of flight?  2. Can I maintain airspeed within 1 or 2 knots in all phases of flight; level, climb, descent using the answer to question 1?  3.  Am I as attentive to slope management as I am to airspeed during landings?  3. Do I understand mixture control management during all phases of flight including on the ground?  4.  Do I understand the most effective use of the speed brakes?  5.  Can I smoothly execute a go-around from a bounced landing or understand the energy management of the M20M to know when I can land after a bounce?  6.  Can I easily handle crosswinds of 20-25 knots and the methods used to be able to safely land in crosswinds in excess of those?  7.  Can I efficiently slow the plane down from 160 knots to 75 knots over a 5 mile distance on an instrument approach without harming the engine?  8. Do I understand my avionics and autopilot so well that it never surprises me?  These are just a few questions off the top of my head that, if answered in the affirmative, make the proficient Bravo pilot.  This is not experience gained over a couple of hours of transition training.

[hazek]

10 hours ago, donkaye, MCFI said:

These are just a few questions off the top of my head

Thanks. Got almost all covered but yes I need more crosswind practice.

When I say I got them covered I mean I at least have the theoretical knowledge, of course practical knowledge is what I am building now and no training can really provide that in the scope needed to really be good at everything. For example I use flysto to track my landings to make sure I'm within good parameters for my approaches as well as rollouts. As for engine management, I've learned quite a few tricks already, for example I close the cowl flaps in cruise before I reduce the throttle from cruise climb to cruise setting, seems to reduce the cooling rate in the moment of power reduction. I also go mixture full rich already slowly right after gear down to spread out the cooling in the final approach. I used to do it on final or on base which combined with reduced throttle again resulted in a lot of cooling all at once. I trim religiously, most of the time I can let go and the airplane will keep the speed. And I've read and reread the KFC150 manual and I have a good grasp on what it can do and how although I barely use it right now as I try to handfly as much as possible in order to gain more handflying skills with the plane becoming better at keeping heading/alt. GTN650 I was very familiar with from before as all our club's planes have it. Plus I use the sim app on my ipad to refresh my knowledge from time to time. And well the six pack is the six pack. I built my own checklist so I went through the procedures for all phases with a fine tooth comb several times. I have a pretty good grasp on various emergencies and on the various systems and how they could break. I religiously check my engine monitor data after flights, to make sure I manage the engine well. The biggest fear I have is a gear up landing and somehow ruining the engine or the turbo and exhaust. I've done a few go around already, I always maintained good control and I religiously refresh the procedure before every landing in my landing briefing. I'm well aware of the nose up surprise, the need to trim nose down immediately, and the need for a lot of right rudder. I like the 5 C's mnemonic, but I've adapted it for the bravo: Cram, Check (that prop and mixture are full forward, speedbrake off, boost pump on), Clean, Cool, Call. I've slightly bounced a few times and always had a nice landing afterwards, I know how to hold the nose and wait for it to settle or when the bounce is high enough to go around.

I plan to take an UPRT course soon. My biggest fear is what I don't know that I don't know. I try hard to learn from accidents and be safe. My biggest weakness is overcontrolling. I'm now religiously forcing myself and reminding myself to not touch the elevator in mid day bumps down low and I force myself to make slight gentle pressure inputs for corrections especially during landing. It's a work in progress. I don't know what else I could be taught other than crosswind practice but I'm very open to suggestions. Very much so.

[Ragsf15e]

On 4/21/2025 at 9:55 AM, Rick Junkin said:

Those will be good data points, thanks!

In the Bravo community we have the issue of the POH not speaking in terms of % power. Actually this is a non-issue as far as general aircraft operation; it only becomes an issue when we want to do something like the comparison you are about to do with pre-determined power parameters. Then we have to get into the charts in the Lycoming manual and do the calculations, because it doesn’t speak directly to % power either. Not a big deal, just requires some chart reading and math.

The other way for us to do it is to set LOP power, see what airspeed it gives us, and then go ROP and search for the power setting that results in the same airspeed. Using this method requires no book work.

Ok, here we go!!  The first one is POH 65% power setting which also matches up with the TCM operating manual for 65%.  It’s at 11.3gph or peak tit.  I wasn’t quite at peak tit at 11.3, but speed was the same either way.  I let it settle between each change…

POH 65%:

second one is using the “key number” of 50 for 65% and setting 100 rich of peak on the first egt to peak.  Hmmm, same speed, more gas.

100 ROP “key number 65%”:

Last one is lean of peak, 10.4ff for my 220hp engine.  This is ~30 lean of peak on the last cylinder to peak.  Hmmm, same speed, less fuel (~10% less than poh), cooler chts!

30 Lean of Peak:

speeds are all within a knot!  Up to you if you want 10.4gph or 12.4gph.