Lop Bravo

[Cruiser]

Gentleman,

 

I have just stumbled in to the Mooney site, and in this thread alone read some pretty alarming things, like running a Turbo 550 at 100ROP etc.

 

I am happy to hang around and help as best I can, but we need to have a mindset of moving past old wives tales and working with data backed facts.

 

......snip

 

 

 

Hi David and welcome to MooneySpace.

 

I will take you up on the offer to help and here is your first test at least for me.........

Many talk about the "red box" and "50°F ROP is the worst place to run" even APS suggests the "big pull" to avoid it for even a few seconds (an ominous statement in itself). 

The Cruise Power Settings and Fuel Flow chart in my POH  states "Best Power is 50°F Rich of Peak" and provides the MPxRPM and FF setting by altitude and temperature for this power setting. 

Now, for the question.

Specifically what bad things are going to happen to my engine if I operate it at the factory recommended setting?

Please be specific, I don't understand "it will blow up" or "you will burn it up"

Facts and data would be helpful. I am not asking for a free class or detailed explanations just what are the results.

 

respectfully,

[David Brown]

Wow, thanks for the great welcome. It is 10.15pm here and a big weekend, so rather than waste my day doing work tomorrow, I will come back here and answer some questions as best I can. Besides…work can wait surely!

 

Just remember APS is not the day job, in fact it is not even a proposition for profit, so anything we do here in Australia or anything I offer or suggest in attending a class is not motivated by profit.

 

Having just had a ding dong battle on another forum where some folk want everything for free, the welcome here is nice to see.

 

Have a good Sunday, be back tomorrow/later today. Nitey nite 

[David Brown]

OK, half the day is gone, and I am just getting to this thread! Let me see if I can help answer a few questions for you guys. Just remember I have no vested interest in saying this……Sign up for the next APS class, it will open your eyes to not just knowing something, but better than that, understanding a whole range of things. Knowing a thing often applies to one thing specifically but understanding a whole range of things allows you to work out for yourself any specific thing.

 

 

 

Welcome David!  While 100ROP may not be "optimal" (an expression Walt is fond of) for the TIO-540, I don't think it is necessarily alarming if you're running modest power settings (<70%)... 

 That would be about fair, closer to 70% we would suggest more like 125 or so ROP, but lets remind ourselves these are rubbery numbers and conceptual, there is no knife edge. What was alarming was some statements earlier in this thread where running up around 27" and just rich of peak.

 

Nothing like that is going to kill your engine any time soon, but if pressure and temperature are the enemies of strength and longevity, then one has to assume that avoiding that while still getting the job done means you will keep doing the job longer and with less stress on the engine.

 

 

Hi David and welcome to MooneySpace.

 

I will take you up on the offer to help and here is your first test at least for me.........

Many talk about the "red box" and "50°F ROP is the worst place to run" even APS suggests the "big pull" to avoid it for even a few seconds (an ominous statement in itself). 

The Cruise Power Settings and Fuel Flow chart in my POH  states "Best Power is 50°F Rich of Peak" and provides the MPxRPM and FF setting by altitude and temperature for this power setting. 

Now, for the question.

Specifically what bad things are going to happen to my engine if I operate it at the factory recommended setting?

Please be specific, I don't understand "it will blow up" or "you will burn it up"

Facts and data would be helpful. I am not asking for a free class or detailed explanations just what are the results.

 

respectfully,

Tom,

You are most welcome. 50dF ROP is possibly best described as the least optimal place to run, so lets look at why and do so at various power settings. At full power this is where detonation is most likely to occur. Not easily achieved I might add with a NA engine, but with a Turbo it is. Run the CHT/IAT/Oil temps up and or some lower grade fuel, and away you go. But nobody seriously sets out to do that.

 

In the cruise what do we get? Well it is not quite Best power, that despite what your book says is around 75dF but we are splitting hairs a little here. I am at a loss as to why it got the name best power, it suggests best as in the perfect place, or most optimal, but what it really means is the point where peak power is obtained for that given MP&RPM.

 

The reason APS recommends the big pul is that many folk would sit there watching the LEAN FIND function on their EMS and slowly watch each cylinder peak. This is sub optimal on a number of fronts and produces negative results, and high CHT's especially in TN/TC engines at high power. It was not because you would crater your engine in a minute or less. So do not read too much into this. A BMP is just a much better way to do things. Once there let things cool off even more and if you want to accurately set a give XXdF LOP sneak up to peak on the lean side. This way you will find out where peak EGT is without running the CHT's up and reducing volumetric efficiency.

 

So what bad things are going to happen at 50dF ROP. Well none if the power is low enough. but it is neither the most power and assuming at 70+% power nor is it rich enough to keep the ICP and CHT at a level we think is optimal for long service life. If you want better efficiency a LOP power setting will be better. If you are at 60% power, and you want the most power possible 75dF is a good place to be.

 

For a given power, look at the following and see which has the best outcome.

 

And when you consider how that peak pressure works with CHT from the next graph

 

………it all starts making sense.

 

So if we are to keep the Internal Cylinder Pressures under control and within the designers desired operating parameters, we can do this at varying powers by either running Rich of Peak, and sufficiently so, or by running lean of peak, and again sufficiently so.

 

Just note that 1/BSFC is dependent on the power produced, that brown line moves depending on the % power made. So at 80+% it is  peaking in the 60-80dF LOP range and when at very low powers such as  60-65% it is more around 10-20dF LOP. Again…fuzzy edges here, no knife edges.

 

Have a play around with this link here http://www.advancedpilot.com/redbox.html This was posted up after one of the students down here in Australia asked how best to demonstrate this to the young commercial pilots that worked in her charter company. It is a great tool and one we use in class. On the lower graphic, grab the knob with the mouse pointer and set the power setting.

 

Last of all, as you can see from the BLACK HP curve if you start out at say 75% power on the rich side of peak and then lean out past peak, the power falls away and by the time you get to an optimal LOP setting you have lost about 10% power, or in other words you will be around 65-67%. So when you start at 75% (ROP settings) and you think that means 40dF LOP, well you should anticipate being about 65% so thus you actually wanted about 10-20dF LOP. This explains why some people end up being so far LOP that they suffer big speed losses. The other is from volumetric efficiency loss as mentioned above…..but lets save that for another day. 

 

 

So while you respectfully asked and not wanting a lesson for free, and I appreciate that (too many freeloaders out there) the reason we stress doing the course is that a 2.5 day laid out in perfect teaching order course is hard to wrap up in one post on the internet. It just can't be done. But get along to the next one, I might be back over there again if the planets align. 

 

Hope that helps!

[jlunseth]

One footnote.  If you do the big mixture pull so you are over on the lean side, and then you want to use your engine monitor to find where peak is and adjust back to a setting which is certain number of degrees lean of peak, the way to do that - from the lean side now, not from the rich side - is to find peak from the lean side using the ROP lean find function, not the LOP lean find function.  I repeat, if you are on the lean side already, you would use the ROP lean function to find peak.  The reason you would use the ROP lean function from the lean side, is that the ROP lean function finds the first cylinder to peak.  The LOP lean function finds the last cyclinder to peak.  And you want to use the peak of the cylinder that is closest to peak.  If you are already on the lean side and looking for peak from the lean side, that will be the first cylinder to peak, which is what the ROP lean function of the engine monitor will tell you.

 

The engine monitor does not know whether you are on the rich side or the lean side when it starts the test.  All it wants to know is whether you want it to tell you which is the first cylinder to peak (ROP function) or which is the last cylinder to peak (LOP function).

 

If you use the BMP to get over on the lean side and then use the LOP function to find peak and lean back to a setting of "x" degrees lean of peak, you would be using for your set point, the cylinder furthest from peak, not the cylinder closest to peak.  And since there is going to be some variation between the cylinders, that could mean that the cylinder closest to peak is actually at peak, or even slightly over on the rich side of peak.

 

You can also use the monitor's LOP function by not doing the BMP and leaning over from the rich side, in which case the monitor will correctly call out the last cylinder to peak.  Best not to dally when doing that, but you won't blow your engine either. 

[David Brown]

Ahhhh….GOOD POINT! 

 

And this is why we suggest to our students that apart from helping you do a GAMI spread test in the cockpit, the lean find functions are basically useless and a waste of time. OK that is harsh, but you get my point.

 

Some crankier engines this is not always easy but once you know which is the richest cylinder just follow that one and watch the raw data.

 

Otherwise if you really feel the need, as described above is the way to do it from the lean side.

 

See the problem with internet forums, you can never seem to get everything you need into a post…..sometimes even a whole thread! 

[Shadrach]

David, I too set power by what I know to be true at WOT. The cyl is richest (#2) for LOP ops and the cyl that is leanest (#3) for ROP ops.  The potential issue with using just the two known cylinders is that some have found that those values change at partial throttle. Have you ever seen an example of spreads and richest and leanest cylinders changing with partial throttle? I have never tried so I cannot say where my engine is at partial throttle... I never set cruise at partial throttle so it matters not to me.

[David Brown]

Gooday Ross,

 

I rarely use partial throttle, it is against the law! 

 

And yes some Lycomings are a bit random day to day, and in particular my IO540, however it is not as random as you might think. And when one has pretty closely matched F/A ratios it is possible to have any one of them peak just prior to the other, the fact still remains that they are all so close together, it really matters not.

 

So we are now talking about micro-management.

 

But your observation is valid that some play nicer than others.

[donkaye, MCFI]

I had GAMIs installed in ADA.  Jean Paul flew with me to establish the GAMI spread.  It ended up at about .3 or .4.  With the mags I had at the time I was able to fly LOP, but still at only 1 power setting.  It was a while ago so I only remember that 2200 RPM worked and nothing higher.  MP didn't make much difference as expected LOP.  After a mag change, I was never able to run LOP again.  The timing was double checked and it was correct.  The TIT would peak go down and with continued leaning start up again.  It became  a process in futility.  I know of one only Bravo engine that has successfully run LOP.  I do not recommend it with the turbocharged TIO540AF!B engine.  I've had my plane now for 21 years and am at 1,000 hours on the second engine.  The first one was exchanged for a reman at 2,300 hours.  We ran it over TBO because the Bravo conversion was done at 1,300 hours.  I now run ROP at between 1600 and 1625 TIT.  This gives 19 gal/hr for the first hour and 18 gal/hr thereafter at 29/2400 or 75% power.  Into the wind I will run up to 31/2400 or 80% power.  Run any higher power settings and expect to buy a new engine before TBO.  Cylinder #1 runs the hottest and I haven't been able to get it much below 400°F at 17,000 in the summertime by trailing the cowl flaps a bit.

 

Don Kaye, MCFI

[David Brown]

Don, I have heard these things before, and to be fair the engine is the problem not the science, and I am sure you understand that.

 

So what changed with the mag change?

 

Tell me do you remember what happened as far as any changes in typical EGT and CHT say during taxi or during a full rich climb? Anything you remember or have data on from the days before and after the mag change.

 

John-Paul is a great guy, but I doubt it was his aura that left with the mags   But perhaps it was!

 

If it was possible once, it is possible again. But I do confess like the Aerostar folk, some a cranky sons of Beech's!      is the Beech word bad here?

[mike_elliott]

David, while I don't have anywhere near the time Don has in a Bravo, I have found his numbers to be spot on. I am a LOP'er also in my IO360, but never could quite get the bravo's to satisfactorily run LOP, granted most were with "stock" injectors. I often speculated it could possibly be the mags not consistently firing at the correct time at altitude and current ICP's, possibly explaining Don's observation when his mags were changed. And yes, the "B" word is civil people try to avoid using in public. Its a cultural thing   Oh, and thanks for jumping on the forum. Verifiable data is always appreciated

[donkaye, MCFI]

By far the Advanced Pilot Training Course was one of the most valuable courses I have ever taken.  There just isn't enough basic engine management training in the usual curriculum of pilot training.  The TIO540AF1B engine now costs $61,000 for a reman.  While LOP operations are great for the Continental and even the non turbocharged Lycomings, I am not going to spend any more time trying to figure out how it might be done on my engine after the amount of time I spent on it in the past.  No one including the GAMi folks have a good handle on it.  It could be the pressurized Slick Mags with their lousy plastic gears creating the issue.  Anyway, yes, I do believe in the physics of it.

 

Right now I'm waiting patiently to get my airplane back from the avionics shop where it has been for the past loooong 4 months.  Luckily, I've still been doing a lot of cross country flying helping people who have recently purchased Mooneys learn to fly them.  There finally seems to be an uptick in the number of people buying these airplanes.

[KSMooniac]

I'm sure glad you're staying busy with new Mooney owners!  Hopefully that is a sign of more good things to come...

 

Are Bendix mags an option on the Bravo engine?  Do you recall which plugs you were running before and after the change?

[aviatoreb]

 

Right now I'm waiting patiently to get my airplane back from the avionics shop where it has been for the past loooong 4 months.  Luckily, I've still been doing a lot of cross country flying helping people who have recently purchased Mooneys learn to fly them.  There finally seems to be an uptick in the number of people buying these airplanes.

 

That's a long time without your bird.  Lucky you that you get to fly with other people's Mooneys and get paid for it!

 

Great to hear of the uptick in the market!

 

You even helped me fly my Mooney and you might not even know it!  I purchased your landing video when I first purchased my Mooney 3 years ago during my transition, and I just watched the sight picture every day for like a month on your video until it was very familiar.  It really helped.  Great video!  Thanks!  (I recommend it to everyone!)

[carqwik]

I think my plane is a clone of Don's...almost all the same power/rpm settings and fuel flows...except my hot cylinder is #6 which also runs close to 400 CHT in cruise.  All of the others run between 340 and 380 or so.  Also only run ROP right around 1600-1625 or so on the TIT...now on my third probe.

[David Brown]

Lets widen the discussion out a bit, and some or none of this may help, but hey it might be finn all the same.

 

Slick Vs Bendix, well, you know the saying, "I would rather have timed out Bendix than a new slick!" But all jokes aside, there is not likely to be an issue there. However, my reason for asking about changes in EGT and CHT after the changes, is because the magneto timing and the internal timing of a magnet matter. A retarded timing setup will be less desirable when trying to run LOP, however you do not want excessive advance especially in a turbo. What I would be checking is that the timing is accurately set, and just because the A&P says so is not in my experience good enough.

 

Buy your own or buy it for your mechanic if he does not have one. http://www.ritesystem.net

 

How about a check list and every item is worth checking carefully.

 

1. Timing is actually as required…..double check!

2. Spark Plugs, gapped to 0.016-0.018" and check for resistance under 5000ohms.

3. Turbo owners, think carefully about replacing any Champion fine wires with either Champion or Tempest massive electrodes, or Tempest Fin Wires.

4. Ensure all plug wires and contacts are clean and in good condition.

4. Ensure all intake plumbing is leak free. This is very important, and even more so for NA engines and Lycomings are known to leak like a sieve!!

5. then if you can go the GAMI route. And follow the path of getting the F/A ratio's correct.

6. Often getting a RPM that works for you is trial and error, and even the N/A engines suffer this a little. 2400-2500 often works although personally I do not have a lot of experience with all the Turbo Lycomings, but some I have flown are no trouble at all.

7. If TIT is an issue check timing! Often a lower RPM helps, and if you get set up at say 29"/2400 and 80dF LOP, add back some MP of a couple of inches afterwards.

8. If you are going to run ROP, do so Rich enough!!

 

The Red Box Green Box is summarised as follows;

 

 

Red Box = No Fly Zone

• • At and below about 60% power, there is no red box. Put the mixture wherever you want it. 
• • At about 65% power or so, 100ºF ROP to Peak. 
• • At about 70%, 125ºF ROP to 25ºF LOP. 
• • At about 75%, 180ºF ROP to 40ºF LOP. 
• • At about 80%, 200ºF ROP to 60ºF LOP. 

 

 

 

 

Outside the Box

• • At 65% power, use richer than 100 ROP, or leaner than peak EGT. 
• • At 70%, use richer than 125ºF ROP, or leaner than 25ºF LOP. 
• • At 75%, use richer than 180ºF ROP, or leaner than 40ºF LOP. 
• • At 80%, use richer than 200ºF ROP, or leaner than 60ºF LOP. 

 

 

 

Don, that is an interesting observation you have made. We firmly believe that the future with upcoming unleaded Avgas will be brighter for GA. There are a lot of people who are sitting on their hands and this is part of the slow down. Until there is confidence that the higher HP and Turbo aircraft have a fuel for the future, growth will naturally be negative. I can assure you that the future in respect of fuel is very bright indeed. 

 

The good thing is that if you are seeing growth, Mooney are going to produce again, Piper are going OK, Cirrus are selling, Beech could do well if they just got their act together……there is half a chance!

 

Don I appreciate the accolades for the APS classes, you are 100% correct in that as pilots or engineers there is a huge gap in education and what is education is half wrong! Keep promoting it, I have no vested interest in the USA apart from the fact the course is something I am passionate about. Any Mooney owners down under, well you can keep your eye out for the next one we run down here!

 

Any questions……keep 'em coming.

[donkaye, MCFI]

I'm sure glad you're staying busy with new Mooney owners!  Hopefully that is a sign of more good things to come...

 

Are Bendix mags an option on the Bravo engine?  Do you recall which plugs you were running before and after the change?

 

Same plug type, I didn't change them, RHB37E

[carusoam]

And the price on the website is $150. Not bad for what it does....

Best regards,

-a-