TSIO 360 leaning questions.

[Old Akro]

In the past, the engines that I have run LOP have not had LOP prohibited by the engine operators manual. Using the Deakin / APS leaning techniques were not in conflict with the engine operators manual.

However, the CMI TSIO360 engine operators manual specifically prohibits LOP operation. Yet, anecdotally many Seneca II, Mooney 231 and Tirbo Arrow drivers run LOP successfully. I hoping for a comment by Jaba or JD or Walter on this.

Also, there is a thread on the Beechtalk forum about leaning solely according to TIT where George Brayley says that leaning according to TIT is fine and that EGT's are not that important for leaning of turbocharhed engines. However an APS branded seminar delivered to the EAA (by I think Mike Busch - available on the EAA website) condemned leaning by TIT. I can't see any reason why you wouldn't lean by TIT. Surely TIT and EGT have a direct relationship? The numbers might be different, but the curves should be the same shape?

My third question is leaning in the climb. The engine operators manual and the POH say to climb full rich. This is a pretty frightening fuel flow rate. I assume this is for cylinder cooling. But, I climb at 75% power and Carson speed (117 kts for the Seneca) not Best rate speed (89 kts). So, can I lean to best power settings as long as the CHT is within limits?

Out of curiosity, I overlaid the mixture / power graphs of the TSIO 360 and its normally aspirated brother. I was surprised at how different all 3 curves are (best econ, best power and full rich). Best economy and best power are not too different below about 80% power (the TSIO version uses a bit more), but full rich figure is about 50% higher. Is this just to provide fuel cooling? And shouldn't the turbo version be more efficient?

[Jabawocky]

Akro,

Send me a scanned or PDF of your POH first of all.

Second,
However an APS branded seminar delivered to the EAA (by I think Mike Busch - available on the EAA website) condemned leaning by TIT.

I highly doubt that would or could ever happen. It may be theoretically possible, but not likely.

Q3 well if you climb full rated power, full rich is the go. If you de-rate the climb power adjust the fuel flow accordingly.

As for the difference in fuel flow, two reasons. First for high powers the detonation margin and IAT/CDT requires a bit more, secondly the compression ratio of the TC is lower thus the fuel used per HP is always going to be higher, all things otherwise being equal.

Send me the POH, we can talk later.:ok:

And I will post back later too, or JD or WA might drop in. I am setting up for APS class in Perth......if you are quick......:}

[Old Akro]

Jaba

This is the EAA video, but I wrongly remembered one of the logos, so I may have done you a dis-service. Because its branded Savvy Aviator, I'm presuming its Mike Busch.

EAA Video Player - Your Source for Aviation Videos (http://www.eaavideo.org/video.aspx?v=2534345030001)

I think I have a pdf copy of the engine operators manual. I'll email it. Enjoy Perth.

[jdeakin]

Old Akro,
In the past, the engines that I have run LOP have not had LOP prohibited by the engine operators manual. Using the Deakin / APS leaning techniques were not in conflict with the engine operators manual.First, let me gently take issue your "Deakin / APS" comment. While I love the attribution, and I wish I could take credit, t'ain't so. Nor is it an "APS method" as we didn't invent it. The method has been described in the literature since as far back as Lindbergh's flight across the Atlantic. (I know you know this, but for historical purposes I feel compelled to mention it.)

Post WWII, the airlines re-discovered it, and put it to good use, as well described in "BASIC THEORY OF OPERATION," a 32-page booklet given to all pilots, flight engineers, and mechanics at American Airlines, along with very clear MANDATES similar to "YOU WILL OPERATE THIS WAY." Other airlines and the military got the idea, and the result was about 400,000,000 engine hours of operation on the R-3350 and R-2800. That was directly responsible for those engines going from a TBO of about 400 hours, to 3,600 hours. It was still improving when those wonderful engines were rudely knocked out by the jets, with their stinky fuel and awful screech. :yuk: ;)

But those engines had BMEP instrumentation, which shows the crew TORQUE directly (with a simple conversion to BHP) in real time. Move any lever (Throttle, Prop, Mixture, Carb Heat) and watch the BMEP needle move right along with it.

We lost that with the "flat" engines, for there is no "Nose Case Reduction Gearing" with the big "floating" ring gear of a big radial, not even on the geared flat engines. Additionally, there are lubrication issues on the Radials that don't apply to "flats," but otherwise, the parts of the engine that are involved in THE COMBUSTION EVENT use the same principles, the same metallurgy and the same processes. For that matter, they are identical in all four-stroke, gasoline engines.

However, the CMI TSIO360 engine operators manual specifically prohibits LOP operation.Really? Does it say, "NO LOP OPERATION" in the LIMITATIONS section? It would be the first time I've ever seen that in any manual. There ARE POHs that say very specifically, "DO NOT CRUISE ROP," which would be the way to do it, if that's the intent.

What happened here is that the engine manufacturers and the industry discovered very early on that the "flat" engines will simply not run LOP, they shake too much! EVERYONE thought it due to an imbalance of AIR! Instead of fixing the problem, they stuck various notes into the documentation, with varying language from "Cabin Comfort" to "Undesirable Roughness," and over the decades it became accepted, and the lean side of the power curves were forgotten, and became "THE FORBIDDEN ZONE."

It's laughable now, but it took George Braly to discover it was THE FUEL that was unbalanced, and to develop the solution, which opened up the entire chart, and others had developed the "Engine Monitor," which made it clear to the average pilot. But we've still got those engine manuals first written in the forties, fifties and later with the original waffle-language, which will never go away. CASA making any claim otherwise simply makes them idiots.

That they do, and you fine folks must follow their idiotic rules is beyond reasoning, and I cannot address it.

Also, there is a thread on the Beechtalk forum about leaning solely according to TIT where George Braly says that leaning according to TIT is fine and that EGT's are not that important for leaning of turbocharhed engines. Absolutely true. It has the additional advantage of keeping you out of trouble with TIT limits, which are far more important than EGT, which have NO LIMITS (except for malfunctions.)

However an APS branded seminar delivered to the EAA (by I think Mike Busch - available on the EAA website) condemned leaning by TIT.As pointed out, there is no connection between APS and Savvy. I've known Mike for more than 35 years, and normally he puts out much better than average information, but on some of it, he's simply out to lunch.

I can't see any reason why you wouldn't lean by TIT. Surely TIT and EGT have a direct relationship? The numbers might be different, but the curves should be the same shape?
Good thinking. What's more, you're correct. :)

My third question is leaning in the climb. The engine operators manual and the POH say to climb full rich. This is a pretty frightening fuel flow rate. I assume this is for cylinder cooling. But, I climb at 75% power and Carson speed (117 kts for the Seneca) not Best rate speed (89 kts). So, can I lean to best power settings as long as the CHT is within limits?
Not on most engines, which is one area where Busch goes seriously wrong. He's a HUGE man, and the only airplane he'll fit in is his own Cessna 310q, with TSIO-520s. It's probably the only airplane he's flown. That airplane has a peculiar setup, which makes it possible to use 400℉ CHT as the limit. I think it's a wonderful airplane, but it is NOT the model to use for THIS purpose. It MAY work - for you.

But with your engine, I'd suggest you use MAX RATED POWER, as listed in the LIMITATIONs Section, not the "how to fly" textual material. If there is no time limit on TAKEOFF POWER, use it! You'll get higher (and cooler) sooner, and spend less time. The engine is good for it - at full rich. You should see EGT around 1300℉ in the climb if your engine is properly set up. Which brings us to:

Out of curiosity, I overlaid the mixture / power graphs of the TSIO 360 and its normally aspirated brother. I was surprised at how different all 3 curves are (best econ, best power and full rich). Best economy and best power are not too different below about 80% power (the TSIO version uses a bit more), but full rich figure is about 50% higher. Is this just to provide fuel cooling? And shouldn't the turbo version be more efficient?Good thinking, again. It's just for cooling. And turbos are not generally more efficient, they are meant to give you more power, higher, with very little penalty in efficiency.

How big can messages be in PPrune, anyway? :)

Best...
John Deakin

[Old Akro]

John

Thanks for the reply. I appreciate the effort.

Firstly, let me repeat my apology for mis-attributing the EAA presentation to APS. Its what happens when I work from memory.

Next, one of my trivial issues relates to the efficiency of Turbo's. If they aren't more efficient why do basically all modern European engines use them? They should be getting benefit from entropy. In my comments about the TSIO 360 vs the IO 360 I forgot the compression ratio difference. The IO 360 will have greater thermodynamic efficiency because of the higher compression ratio, but I would have thought that the better volumetric efficiency of the turbo - especially with such a crappy inlet manifold - would have more than compensated.

I understand your point about climbing at full power, but I'm having trouble getting over decades of habit. And I'm re-reading your article " Those fire breathing turbo's - part 4" . This article relates to the turbo normalised automatic waste gate TSIO 550. But the TSIO 360 generates so little boost that it can nearly be regarded as turbo normalised (the boost is certainly kidstuff compared with automotive turbo's). And it has a fixed wastegate - which really just means I have to do more work with the levers. Most of the time the engine operates with about atmospheric manifiold pressure (ie 28 - 32 inches). The TSIO 550 & 360 also seem to share the same design building blocks - although I make this assessment without much facts.

Back to the climb. Your article suggests WOT, which I can't do and remain below the 40 inch limit. But the TSIO is rated for continuous power at 40 inches, so I can run at that. You advocate full fine, but (like the your preference in the Bo) I prefer to run 2400 or 2500 rather than full fine (2575). It just feels less hectic.

If I climb at 40 inches and 2500 rpm, (from memory) I think the fuel flows will be above the "full rich" line in the engine operators manual. If I reduce mixture a little (once again from memory) I think the TIT will be maybe as low as 1100. In your article you are suggesting leaning to 1290 TIT below 10,000 ft. So, with the caveat of CHT limits, can I lean further to 1290 TIT?

I can generally climb with lower CHT than I get in cruise (especially in the flight levels). I don't expect CHT to be much of an issue.

Both Piper and CMI list 75% (31.5 / 2474) power as maximum recommended climb power, while 100% power (40 / 2575) is a continuous rating.

I'm a fan of Carson speeds. So I'd like to climb at 117 - 120 kIAS, not the best rate 89 KIAS or the Piper suggested 102 KIAS cruise climb. Once I've got the airplane cleaned up and sorted, 75% gives me a fairly solid 500 fpm through to the flight levels, which I've thought was good enough.

Now we get to the cruise.

Based on Carson's work, about 60% power should be optimal for the Seneca cruise. But, I'm growing to like the speed of about 65%. So far, I see bugger all actual fuel flow difference between 60 & 65%, but I do see a speed difference. For me this will typically be about 28 / 2400 at 8 - 10,000 ft. The 3 blade props seem to like 2400 rpm.

The Piper POH Normal Procedures section refers to the engine operators book for leaning. The CMI OM says to lean according to the power table & fuel flow figures. I truly find this bizzare.

But, the fuel flow / power graph that we are supposed to use as a leaning reference says:

" Continuous operation at fuel flows leaner than 25degF rich of peak TIT is prohibited for all conditions"

I know you will talk about the only mandatory part of the POH being the limitations section, but that is a pretty explicit statement.

In previous aircraft I have flown (mainly IO-540's) I can run a LOP regime that you would approve of (did you notice I avoided saying APS method?), without being in conflict with the engine operators manual. I don't like being in direct conflict with the engine operators manual.

So, I typically cruise at 65% power and 25 degF ROP. Its not what you teach, but at that power setting its not going to hurt and its consistent with the book. Typically this is about 1575 - 1625 TIT depending on the day. Frequently I find peak is about 1650 TIT (maybe 1625 - 1675). But, it uses a lot more fuel than it ought and has higher fuel rates than the CMI best economy table. I have a suspicion that the best economy table might actually be LOP, but CMI aren't admitting it.

In part I'm looking for courage to try "the big pull" and get to maybe 50 TIT LOP.

The TSIO 360 is a relatively uncommon engine that frequently has service difficulties and is typically excluded from the general advice articles. So, I'm being tentative.

Thanks for your interest in helping.

[RatsoreA]

Keep this one going... I am watching this one carefully! I am a little shocked to see how differently my Seneca (III, TSIO-360KB) runs compared to OA's...

I climb, full rich, at 35/25, at 117kts (thanks for that mate!) and get about 500-700 fpm well into the FLs, and never trouble the CHT's above about 300.

When are you heading to Sydney next, OA?

[43Inches]

Not sure how uncommon you'd call the TSIO 360, there was about 2500 turbo Seneca produced from the Seneca II onwards, plus all the single engine turbo aircraft variations that have used it. I've found the operational problems with them have revolved around the installation especially ancillaries. The Seneca II with EB was pretty good, the Seneca V with the RB was horrible, the III and IV were ok. The V also had density controllers and other nice automatic controls for the turbo, I think the latter IVs had this as well.

We used a 110kt climb in the V, and the earlier models the 100-105 got you up nice and quickly, 117kt sounds like it would work well.

I'd be interested to see what fuel burns vs speed you could get from a Seneca II with LOP ops. These were very misunderstood aircraft that could offer a very cheap twin both in purchase and operating cost. The two blade one we had was light, could carry 5 adults with bags and cruised around 170ktas at about 65%. I don't think the 3 blades, like the Seminole ones had any benefit due to the low power output, the III onward had more power with 220hp so it was more justified.

When we operated the Vs the engineers didn't like the recommended procedure of leaning to peak and requested we lean 100' ROP.

[Walter Atkinson]

Old Akro:

1) We do not recommend WOT for the climb on the TC'd engines. Only the TN and NA engines. We recommend that you use the top of the green MP as outlined in the POH for your aircraft and climb full rich. The 1300dF target is for non-TC'd engines. Your engine's Target should be around 1150-1200dF, so you;r not very far off as it is. Were I flying your aircraft and wanting to treat it kindly, i would leave it full rich at the climb power setting.

2) Using the max RPM is easier on the engine than a reduced RPM. The thetaPP is later and the peak pressures are lower at higher RPMs… all good things. The differences between 2700 and 2500 are small, so I do agree that it is a minor issue.

3) Cruise is a different matter. The POH recommendations to limit cruise power are based on being ROP and they make sense in that condition. If one operates LOP in cruise much higher power settings are fine since they result in lower peak pressures, wider detonation margins (not really a factor) and cooler CHTs. All of these are positive factors along with the cleaner running combustion chamber.

4) "Continuous operation at fuel flows leaner than 25degF rich of peak TIT is prohibited for all conditions" is a good recommendation for ROP back when everyone ran ROP only. It does not apply to LOP.

5) 25dF ROP is the mixture where the exhaust valves run the hottest. If that's your objective, then that's your mixture!

[Old Akro]

Walter. Thankyou. I think the time you & John put into responding is fantastic.

But, inevitably, I have more questions:

1. The 1300dF target is for non-TC'd engines. Your engine's Target should be around 1150-1200dF, so your not very far off as it is

John Deaking article " Those Fore Breathing Turbo's - part 4" which is Pelican's perch #34 says:

TATurbo says, for climb, rich of peak EGT (ROP), with their turbo installation, use the mixture, and:
Below 10,000 feet MSL, adjust the Turbine Inlet Temperature (TIT) to about 1290°F.
Above 10,000 feet MSL, adjust the TIT to about 1270°F.
Above 17,000 feet MSL, adjust the TIT to about 1250°F

In fact, I suspect that pilots could just use 1250°F during ROP climbs, with very little "cost."

This concept of a "Target TIT" works very well in a very wide variety of turbocharged engines, not just the normalized versions.

He goes on to make further references to leaning the TSIO 550 by reference to TIT. This is where I got both the idea and the numbers, so please explain.

Part of my problem, is that there are a number of versions of full rich for the TSIO 360. This is why I am looking for a better reference. The variations I have are:

1. Actual full rich on the aircraft. This frequently has higher fuel flows that the "Max Allowable - full rich" line on the fuel flow vs BHP graph in the CMI OM
2. Full rich as defined by the " Max allowable - full rich" line on the fuel flow vs BHP graph in the CMI OM. I will need to lean to get to this figure.
3. Rich by TIT - any guideline of climbing by TIT (even your suggested 1100 - 1200) will require a degree of leaning.

If I look at the fuel flow vs BHP graph for the TSIO 360 - KB engine of the Seneca III as a proxy then I get 2 more full rich figures;
4. "Recommended Full Rich" when I overlay the TSIO 360 EB graph, this is a higher fuel flow than " Max allowable - full rich" for that engine.
5. The TSIO 360 KB engine has an additional line labelled " Approximate Full rich"

At 200 Hp (40 / 2575) these 5 different " full rich" conditions show a variation of about 10 litres / hr (about 11%).

I will check later today, but from memory the procedure to set fuel pressure is the same for all variations of the TSIO 360, which makes the variation in the full rich curve between engines as more curious.

I also find it curious that " full rich" changes across the TSIO-360 series. At 200 Hp it varies from the TSIO 360 AB at 110 lbs/hr to the TSIO 360 EB at 140 lbs/hr. This makes me think that " full rich" is a notional concept.

At the CMI Recommended climb power of 75% (150 Hp) the difference between these full rich figures is 14 litres per hour - or about 25%.

[Old Akro]

We recommend that you use the top of the green MP as outlined in the POH for your aircraft and climb full rich.

Intuitively, I agree. Certainly in a NA or TN engine there are volumetric efficiency benefits from WOT.

But, I like the graphs in the CMI OM - especially the older ones which are not straight lines and look like they were hand drawn from empirical data.

The TSIO 360 EB graph (which I believe is the same engine as the TSIO 360 KB, but with a lower redline RPM - 2575 rpm vs 2800 rpm) is pretty interesting when you hand draw the KB curves on the top. It looks like someone took the EB curves and made them into straight lines for the KB.

On the EB graph the fuel flow rate goes hyperbolic from about 90% power. If I run the power settings that most guys use - 35/2500 this is about 86% of the rated 200 Hp (40/2575) but has a fuel flow of 113 lb/hr vs 140 lb/hr for full power. That's a 19% reduction in fuel consumption for a 14% reduction in power.

So, wouldn't it make sense to climb at 35/2500 (86%) or 35/2575 (88%)??

Interestingly, the KB engine has a note for power settings in the range 150 Hp to 180 Hp which allows leaning to TIT 1525 degF conditional upon CHT < 420F & Oil Temp < 200F. I think this would lean the engine to the best power line, which seems too lean to me.

[Lumps]

There is a course you could do that'd answer all these questions, plus many, many more

[Jabawocky]

Akro,

Johns article comments expressly refer to a TNIO550 or 520 with TN being the operative. The MP is 30" (+/- a bit) and not the same as your 38" so as Walter has commented, the fuel flow and BSFC is going to be much higher, and he means much higher. To have a lower compression means higher EGT, but with the much higher MP and a need to maintain a detonation margin this means a much higher fuel flow per HP, or a higher BSFC at takeoff powers.

Still in Perth, and not able to dedicate hard numbers but the fuel flow will be rather high at takeoff. I see your conundrum.

Perhaps JD or Walter will get an answer sooner but I need some sleep right now.....will study the manuals you sent me and see what we can come up with. :ok:

[dubbleyew eight]

I have read that there are lots of engines fitted with turbo's for no other reason than they are very effective exhaust silencers.

[Walter Atkinson]

Old Acro, et. al.:

1) John's series on "Those Fire breathing Turbos" was aimed at the TNs.

2) I made a late-night error in my post to you earlier. Your TC Target TIT should be in the 1350-1400dF range. Lower CR gives higher EGT/TIT values. That should bring your numbers closer.

Please accept my apologies for the error. Brain fart late at night.

[Old Akro]

Walter, once again thanks

So, I'm planning to try this instead of my old 75% cruise climb.

35"/2575. This will be about 90% power - full fine and 5" back from the top of the green. However, it a) gives some headroom to max MP which can be easily exceeded and b) by the CMI graph puts me in a more efficient BSFC area.

I'm going to set about the CMI KB " full Rich" flow (70 litres/hr), then check the TIT and lean further to 1250 degF TIT - 1300 degF TIT (with the caveat's about CHT).

Cruise is more interesting.

I have never been able to achieve the CMI fuel flows. I have a deep suspicion that despite their "prohibition" on fuel flows leaner than 25 degF ROP TIT that in fact the economy fuel flows that they publish are maybe 25 degF LOP TIT.

This would explain why I can't get there, because I stop at 1650 degF TIT. Getting to LOP requires going though the 1650 TIT limit.

I couldn't sleep last night and was fooling around in the NASA Langley library. There is nearly nothing those guys didn't research in the seventies. Including running a TSIO 540 with hydrogen injection. UNFKNBLVBL. They hung a hydrogen generator out in the slipstream. But they made some baseline measurements on pure AVGAS that are informative.

There's also a paper on a TSIO 360 with oxygen injection to reduce exhaust emissions. But unfortunately, they only tables emissions data, not engine operating conditions.

But, particularly the Lyc TSIO 540 graphs helped me understand the behavior of TIT better. So my plan is to try 65% power and do what CMI say and lean to a fuel flow and see what happens. I think maybe it might go through peak TIT to 25 - 50 degF TIT LOP. In which case its probably a pretty good place to be.

[Tinstaafl]

Where did you get the Lyc TSIO-540 graphs?

[Old Akro]

This is the hydrogen injection paper, and I think I remembered wrong and they used a Duke. Titled "Ultralean combustion in General Aviation Piston Engines" dated 1979!!

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800013943.pdf

There was also another interesting paper on cooling air inlet design by Miley Owens & Lawrence

There is also a paper by Gerald Slusher of NASA which looks at exhaust gas temperatures at various locations, exhaust component temperatures and engine vibration levels. I got some interesting points about the variation of exhaust gas temperature, but I needs a serious read.

There is also some papers from Lycoming & Continental engineers that aren't available on line that I have requested.

[Walter Atkinson]

Old Acro:

**I'm going to set about the CMI KB " full Rich" flow (70 litres/hr), then check the TIT and lean further to 1250 degF TIT - 1300 degF TIT (with the caveat's about CHT). **

That should give you plenty of "head room" on the Red Box, ROP. Should work fine.

**I have never been able to achieve the CMI fuel flows. I have a deep suspicion that despite their "prohibition" on fuel flows leaner than 25 degF ROP TIT that in fact the economy fuel flows that they publish are maybe 25 degF LOP TIT.**

The POH Best Economy FFs will probably be either AT peak TIT or at 40dF LOP. If they are interested in TRUE Best Economy, it will be at 40dF LOP where the engineering graphs say it is. If they are hedging their bet about balanced F:A ratios and rough running, the number will likely be at peak. It will be interesting to find that out.

**This would explain why I can't get there, because I stop at 1650 degF TIT. Getting to LOP requires going though the 1650 TIT limit. **

The TIT limit is often misunderstood -- it is not an instantaneous limit. It is a limit for continuous ops at max rotor speed at 1650dF, which would likely only occur at critical altitude. This seldom the case, so there is a buffer built in. You can safely exceed the limit for the time it takes to find peak and reset the mixture either ROP or LOP. Most POHs list this a five-minute period.

[Old Akro]

Thanks Walter

I'm just reading the proceedings of a symposium on piston aircraft engines from 1976. Both CMI & Lycoming did work with 80% power climbs at best power mixture settings. This regime seemed to work well, but tHeir main concern seems to be that cooling airflow is not reliably good enough. Specifically to the TSIO 360 that I'm interested in Continenta says that the engine needs 5.5 inches of water pressure drop across the engine rather than the common 4 or less.

This work seems to have been in response to a NASA sponsored project to look at emissions. More power to NASA!

The frustrating thing, us that it looks like the engineers at both Continental & Lycoming knew what to do to improve the engines, but it never happened.

I presume the product liability crisis and FAA regulatatory compliance made it too hard / too expensive.

I was also interested in another paper which experimented with what it called a " dog house" or air box which fitted on top of the engine to do away with baffles. This seems to be an outstanding idea and I'm surprised it hasn't been more widely adopted - or even that someone hasn't STC'd something.

They were also doing work on better injectors. Another paper has in service photos of injector " spray" patterns of a range of injectors. The CMI injectors really are just a dribble. In the seventies, they had a plan to make it better. But 40 years later nothing has happened.

Really, we run aircraft engines sub optimally because of either cooling limitations or cylinder to cylinder mixture variations. Both of which could be fixed easily if the regulatory environment allowed it.

[43Inches]

The TIT limit is often misunderstood -- it is not an instantaneous limit. It is a limit for continuous ops at max rotor speed at 1650dF, which would likely only occur at critical altitude. This seldom the case, so there is a buffer built in. You can safely exceed the limit for the time it takes to find peak and reset the mixture either ROP or LOP. Most POHs list this a five-minute period.

I can't say I understand how the limit is set in place but the PA31-350 leaning technique for LOP is quite specific to not exceed 1650F. It states if 1650F is reached prior to peak then reduce manifold pressure until a 75F drop in EGT then lean through peak if possible until 50-100F LOP, increase MP again not exceeding 1650F and lean mixture further to 1625F. Taking care to remain smooth operation all the while.

All the turbine aircraft I've flown it gets pretty serious if you exceed the maximum TIT limit at any stage of flight for any length of time.

I agree with most of the stuff regarding the LOP stuff but the 1650F in the Chieftain is listed as a red line limitation. The Seneca II also lists 1650F as a red line limitation, havn't got a III manual at hand to check that on the KB. Had to give the engine manual away with the aircraft so don't have access to it any more.

Don't mind the argument for LOP stuff but it will take a lot of convincing to take the needle through a limitation.

[RatsoreA]

I have the PA-34-220T (III) manual in PDF format if you want it. I am flying it this weekend, and will be recording everything very carefully for a comparison.

[Old Akro]

Don't mind the argument for LOP stuff but it will take a lot of convincing to take the needle through a limitation.

2 issues:
1) I'm planning to try leaning to the graph fuel flow. Thus it will go straight through peak before it has any time to react.
2) Exactly how accurate do you think the TIT gauges are? I've calibrated ours at 50 degF intervals. Standard the gauges would be lucky to be +/- 25 degF and probably worse. They are not cold juction compensated either, which means their readings are affected by ambient temperature. This probably adds another +/- 20 degF. So, I think you can afford to take the 1650 degF limit with a grain of salt.

[Old Akro]

Rats

My suspicion is (which is supported by Walters post) is that peak TIT is maybe 25 degF LOP EGT. I also suspect that the best economy line in the engine operators manual (do you want a pdf copy?) is maybe 25 degF LOP TIT (50degF LOP EGT).

Comparing the graphs of the different variant TSIO engines is pretty interesting. The best economy line is pretty much the same for all engines, but full rich varies quite a lot. I wonder if the best econ line is a proper engineering line (probably 1.05 lambda) but the full rich figure has some "political" element with less objective limits.

The CMI Operators manual says to lean to the fuel flow numbers, so I thought I'd try that and see what TIT I get.

[jdeakin]

"43Inches" Said:
All the turbine aircraft I've flown it gets pretty serious if you exceed the maximum TIT limit at any stage of flight for any length of time.From one old jet transport manual I have:

Takeoff 915℃ (Redline and 5 minutes max)
Max Continuous 875℃
Max Climb 875℃
Max Cruise 875℃

There's a wide variation among jet engines, depending on probe location, metallurgy, Engine maker, etc. But one thing is common, a high limit for takeoff for some very short period of time (2 to 10 minutes), followed by a series of limits anywhere between 40℃ and 100℃ lower. Some have slightly different numbers for this "series," some are all the same, as above.

They are for slightly different reasons than most of the Limitations in the Recip world. For example, if you operate a recip AT the redline (often 460℉/238℃) the chances of reaching TBO are slim to non-existent, for the engine will "meltdown" first. In the jet engine, operating at redline will cause "stress creep," which will cause the turbine blades to stretch, and the tips to rub against the case, and result in abnormal wear over TIME.

The result in jets is a limit good for some small number of minutes for each takeoff (redline) and a lesser limit for the rest of the time. The promise is that if you obey both limits, your jet engine will last for 20,000 hours or more between overhauls. And they routinely do! There are often further limits on turbine speeds, where they are critical (N1, N2, N3). Modest excursions beyond the REDLINE are handled with a simple inspection (almost invariably returned to service), and larger excursions will trigger replacement of parts. I've never heard of an engine failure due to this, but I suppose there are examples, in extreme cases.

In general, the LIMITS on recips are a little "different." Historically, they (CHT) are set at the maximum structural limits, with strong recommendations to operate well below those limits. Exceptions for the big radials, which have a METO power, and some "flat" engines with real performance (TIO-540-J2DB, for example).

Now, when they started hanging little turbos on "flat" engines, they did not want to install "Turbo RPM" guages, and they wanted "simple." So, they chose a "limit" approximating the "Max Cruise" setting (or less), and came up with "Max TIT." Garrett (most turbos) makes it explicit in their manuals, saying that the "MAX TIT LIMIT" is permissible CONTINUOUSLY for the life of the turbo, AT maximum load (which is max RPM.)

(Note there is no such thing as a "limit" on EGT, as that's more a function of the timing and flame front speed and NOT a measure of "Combustion Temperature.")

The Garrett manuals go on to say, "MAX TIT may be exceeded for purposes of determining peak, or for testing purposes for short periods of time."

Sounds a lot like "Max Cruise" with an unspecified additional margin for 2 to 5 minutes, to me.

I'm quite content to USE the "TIT limit" (usually 1650℉/899℃) for normal cruise, all day long, and to exceed it for determining peak, or setting LOP, etc.

A further note about turbos with Inconel rotors, with limits of 1750℉/955℃. All above also applies to them, BUT airframe makers "abuse the privilege" by installing cheap, lightweight exhaust tubing. It may be "good enough" for the 1650 limit, but NOT NICE for the 1750 limit!

Best...
John Deakin

[43Inches]

Sounds reasonable, but it still is a red line figure under limitations. The only marking on the Jets and T-props for red line would be the maximum never exceed. The others would mark the start of a caution range possibly, although the ones I've flown have just had a red line at maximum never exceed and memory items for max continuous, take-off etc... There were also transient power fluctuation numbers that allowed excess rotational forces but never beyond max ITT. It is interesting to note that maximum ITT limits on the jets/jetprops work out about the same at around 1600-1700F.

On another problem, on some Seneca II I've seen skin just aft of the cowl flaps and exhaust that seems to be rippled and warped. The way the exhaust is ducted through the cowl flaps seems to point to this area and looks on the surface like heat damage. Ours never seemed to do this but we were conservative with EGTs etc... Not sure what caused it on these other machines though.

[Old Akro]

Every Seneca II I've looked at has a discoloured panel with a degree of buckling. The exhaust basically points right at it. LOP or not, I reckon there is enough exhaust temp to do it.

[43Inches]

I should point out my issue is not with LOP, I'm pretty much sold on the concept. Just possible consequences of high EGT in these aircraft not being limited to the turbine issues.

Does the problem still occur in the III and IV, I can't recall seeing it in those or the V, although the V has a vastly different nacelle and engine set up.

[Jabawocky]

By the way gents, if you want to avoid the TIT peaks for extended time, provided you have good GAMI spreads then use the APS Big Mixture Pull. Sit fat dumb and happy for a few minutes while CHTs cool off and then and only then if you are really inquisitive sneak up from the lean side (the least harmful way) and find the first to peak. This should only take 15-20 seconds at most, and then roll back to your nominal 60-80dF LOP.

You will have seen TIT above 1650 for only a few seconds, and frankly the turbine itself will have hardly noticed at all. Think about it in real terms, it is not so scary then.

Ratso and I might go for a play one day ...what ya say? :ok: If he ever gets his baby back up here.:sad:

[Walter Atkinson]

For the record, in almost all installations, the EGT as the gas exits the end of the exhaust pipe is lot hotter in a NA airplane than in a turbo. Think on that for a bit and posit and answer as to why.

[Old Akro]

The energy that drives the turbine has to come from somewhere!! Expanding the gas causes a temperature drop, just like spraying paint from a can.

There are papers at the moment on new automotive turbochargers to withstand TIT's of over 1050 degC = 1920 degF. Interestingly, the difficult part is housing metallurgy, not the turbine.

[Old Akro]

Sit fat dumb and happy for a few minutes

I can sit fat dumb and happy for much longer than that.

[Jabawocky]

I can sit fat dumb and happy for much longer than that.

You and Deakin must be related :ok:

Walter, that is messing with their heads :}

[Jabawocky]

Old Akro,

Been able to spare only a few minutes on this, and I am sorry but the last few weeks I have been very time challenged.....:sad:

If I was going to come up with a formula that might work, I would be aiming for 35-36" / 2450 or there abouts that is smooth, and around 40dF LOP which if my guessometrics are close enough should give you around 75% power on about 41-42 LPH.

If I get a chance to do this with the backward Aerostar, I will do a lower power say 26"/2450 GAMI lean test first to verify we have a conforming engine, and then give it a try. Some Turbo engines do not play as nice as others at higher MP.

If we can get some good data I am sure one of us will report back.

:ok:


PS: I must confess that my Seneca experience is limited to teaching an experienced CFI how to hot start one.....(no, not kidding, I am serious)

[RatsoreA]

Yes, Jaba and I will be doing some experimentation in the III on Sunday afternoon... Hopefully, OA, any benefits will translate well across to your II.

Maybe this was just for later aircraft (III, IV, V) but mine seems to have a thicker stainless panel directly behind the exhaust, in contrast to the rest of the panels behind the engine and underside of the wing. No buckling at all. Pretty dirty though!

[Old Akro]

Maybe this was just for later aircraft (III, IV, V) but mine seems to have a thicker stainless panel directly behind the exhaust, in contrast to the rest of the panels behind the engine and underside of the wing. No buckling at all.

I believe its common to replace that panel.

I'm hoping to have a fly on Sunday too.

[Old Akro]

I must confess that my Seneca experience is limited to teaching an experienced CFI how to hot start one.

:ugh:

I used to occasionally have difficulty with hot starts in the Lance (IO 540) - although it might have had something to do with a failing magneto, but never the Seneca. Its easy. And if you have trouble with one engine, there's a whole other engine to try while you let the first one rest!!

[RatsoreA]

I've always found the Seneca engine one of the easiest to start... If it's cold, flood it, if it's hot, mix to rich, give it 1/4 throttle and hit the switch!

[Old Akro]

If it's cold, flood it, if it's hot, mix to rich, give it 1/4 throttle and hit the switch

And if that doesn't work - flood it.

The answer to nearly any start problem is to flood it! I've gotten into trouble flooding Lyc's. But never the TSIO 360. BTW, a Pitts with no electrics and a metal prop is a bugger when you flood its injected Lyc.

[yr right]

Biggest proplem with that engine is the induction

[Walter Atkinson]

While flooded hot starts do seem to work for some engines, remember that it carries the very real risk of a fire. More than a few aircraft have been lost to that indiscretion. Just because it has worked without a fire for many attempts does not assure that the next attempt will not burn the aircraft to the ground. For that reason, I no longer use the method--EVER.

Be careful out there!

[Old Akro]

While flooded hot starts do seem to work for some engines, remember that it carries the very real risk of a fire.

Most twin owners would like that. Insurance value is attractive compared with the market. :E

[jdeakin]

Walter said:
While flooded hot starts do seem to work for some engines, remember that it carries the very real risk of a fire. More than a few aircraft have been lost to that indiscretion. Just because it has worked without a fire for many attempts does not assure that the next attempt will not burn the aircraft to the ground. For that reason, I no longer use the method--EVER.Adding to your excellent post, I'd like to point out that the "flooded start" is a widespread technique that almost always works, and proponents will invariably shout down the nay-sayers (like you and me), ending up with something like "I've been doing it for 150 years, and I've never had a fire!"

Not so.

Induction fires are very common with flooded starts, but are very seldom detected, being buried deep in the engine, and they are sucked harmlessly into the engine - where there is supposed to be fire. That's more or less harmless, and the reason SOME manuals have a note.

But consider the case where, for whatever reason, it doesn't work, and you pause for a bit to consider your options. You may have a puddle of fuel under the engine in the cowl, or on the ramp, or puddled in the induction manifold, and depending on a lot of things, it may or may not light off. Even if it does, you may still be lucky, and avoid further complications. There may not be enough fuel, there may not be the precipitating spark, or you may go ahead and crank again, sucking it into the engine, totally unaware of how close to disaster you might have been.

I learned this lesson early. In about 1956 (I was about 17), I was flying a Lambert 90A Monocoupe (antique, even then) and had stopped in Venice, Florida for some reason, and jumped right back in the airplane to start it up again. I flubbed the start, and stopped to give it a chance to air out.

I heard a cry of "FIRE!" and looked to see where the call had come from, never dreaming of the reality. Someone about 100 yards away, and he was pointing directly at ME! Still dim-witted, I looked to the other side, and there was no one there. I opened the door and looked under the airplane, and sure enough, there was a merry little fire, just beginning to reach the greasy belly of the fabric covered airplane. I jumped out and pushed the airplane about 20 feet backwards, and luckily, there was no damage.

It was a HOT Florida day, with a ramp that was hot enough to fry eggs. The overflow converted to vapor very quickly, which created perfect conditions for the tiny backfire I'd had to light it off.

A very respected and senior airman burned up his airplane from a similar event a few years back, and barely got out. He was alone in the airplane. What if he'd had the wife and kids on board?

Mercifully, the wrong circumstances don't happen often.

Best...
John Deakin

[rutan around]

Walter and John are absolutely correct. DON'T do it. I was taught that method and it worked fairly well for 20 years when suddenly.............

I was starting a heat soaked IO 520 at Fitzroy Crossing and it was being cantankerous so I stopped the starting procedure ,flooded it a bit more and then continued using the starter. It did a small backfire and the fuel guy got real excited. He grabbed the extinguisher and poured foam into the engine compartment.

The fire started in the inlet manifold and the backfire ignited the fuel fume soaked air filter. 24 hours later sporting one brand new air filter we were on our way. We were very lucky.

Once again it was a case of OWTs being handed down by people who didn't know better and like me had got away with the method for a long time.

I now use the Cessna Pilots Association method for hot starts. It's not only safe but it's much more reliable.

Cheers RA

[RatsoreA]

The risk mitigation for engine fire is to keep cranking it and keep the fire to where it should be!

I don't know if anyone has had a look at the priming time graph supplied with the POH, but in Australia, it is realistic to expect to prime the engine to anywhere between 8-14 seconds when it's cold (0 degrees C ambient temp) to 6-8 seconds in warmer ambient temp.

Now, quick survery for those that have flown the Seneca, what happens after about 3 seconds of holding in the primer buttons...?!

[Tinstaafl]

Ta muchly.

[43Inches]

Are you referring to the overboard fuel vent, this will occur if the fuel pumps are left on with the engine not turning as well.

EB, Priming 5 seconds warm and 10 seconds cold always seemed to work (without primer buttons). With the primer, hitting it during start usually got it going if stubborn, and the occasional tap until stable.

The RBs only liked a very small prime when hot, but a good dose needed when cold.

The risk mitigation for engine fire is to keep cranking it and keep the fire to where it should be!

Works in most but have still seen an instructor BBQ a Warrior even with cranking after using the throttle to prime it, followed by more pumping during cranking. Had to abandon and use the extinguisher.

[Old Akro]

I jumped out and pushed the airplane about 20 feet backwards

I still reckon most twin owners would push it INTO the fire; not backwards.:E

[Tonym3]

I don't know about all the other silent readers of this thread (and the other threads about engine management), but I have found this discussion extremely valuable. Education in this area during my training was poor to non-existent. I certainly want to find time to get to one of Jaba's classes when they are next being run in my area.

Thumbs up for pprune dunnunda.

[RatsoreA]

Are you referring to the overboard fuel vent, this will occur if the fuel pumps are left on with the engine not turning as well.

Yes. The primer buttons just being a spring loaded switch that turns the fuel pumps on.

Most Senecas I have flown start dumping fuel overboard after about 3 seconds of priming...

Akro,

Gold. There isn't a twin owner out there that hasn't at some point stood there looking at their plane war-gaming how it would go!

[43Inches]

My understanding is that the optional primer buttons allow a higher flow rate using the hi-flow pump in the alternate system. That is primer equiped aircraft have the Hi-Lo fuel pumps. This is why priming using pumps is longer, low flow rate only on non primer installed aircraft.

In the non-primer Seneca II aircraft losing the mechanical pump results in only 25% available power through the aux pump. With the alternate system approx 75% is available through the Hi pump and Lo is used for vapour suppression.

The cold weather start procedure has the fuel pumps on low continuously and using prime buttons as well during cranking, and then as needed until stable operation.

[Jabawocky]

Education in this area during my training was poor to non-existent. I certainly want to find time to get to one of Jaba's classes when they are next being run in my area.

Can I make a cationary warning here. Waiting is a bad idea. If you want to do one, go to it. It will not come to you. Australians are lucky enough now to avoid having to go to Ada OK. and as Walter will tell you, why would any civilised human being want to travel to OK. :E

Last year I was hammered by requests to do a class in Sydney. Wild promises and all that. So we did. If you consider one husband and wife team as ONE, and a Melbourne course student who at the last minute had baby sitting issues, and was lucky to have the next one in her home town, then there were only two Sydney bookings out of the whole class.

Yes how sad.....we had several folk from Tasmania, Queensland, NW NSW and Broome WA.

What was the frustrating thing, that all the folk who badgered me to put one on in Sydney, at greater expense I might add, and poorer venue quality, was that not one of them was one of the two that was there.

So in future we will run dedicated closed courses for organisations like the one in Cairns in a couple of months or maybe in Perth, but otherwise they will be in Adelaide or Brisbane. Why? Well simply no matter where you hold them the majority have to travel anyway. You are away from home and the kids footy, wife chore list etc. And we can better control the quality of the venue.

We do not do them for the purpose of making money, so being careful not to burn ourselves is one thing, and when I think about it, the course is not cheap, but it is not outrageous either, so ensuring the delivery quality and venue quality is up to standard is the most important thing, otherwise the student suffers.

In short Tonym3, if you would be kind enough to email me I will put you on our email list for future courses and we would love to have you along. It is a great 3 days and lots of fun. :ok:

davidbrown'at'advancedpilot.com

[Old Akro]

Walter, John, Jaba

I went for a short fly yesterday. It was for another reason and I didn't have a sustained climb to experiment as much as I might have otherwise, but I set 35 / 2575 and tried to lean to the " Full Rich" figure in the KB engine chart - 67 litres / hr. The TIT was getting higher than I liked (probably would have settled over 1400 degF TIT). Instead I went back to the EB " Max Allowable - full Rich" figure of about 70 litres / hr (might have been a bit more) and got a TIT of 1300 degF (might have been a bit more).

So, are CMI recommending something you you would not regard as best practice? Or is my idea that I could climb at 1250 - 1300 degF a bit too conservative?

[Jabawocky]

Akro,

I would like to see what Walter and John have to say here, and as previously stated my Seneca experience is limited to very little, but in my opinion the following apply;

1. 67 LPH is not enough, and the over 1400dF EGT supports this, assuming timing is accurate.

2. You are possibly being a bit too conservative, for a low compression turbo I would expect a EGT (cylinder EGT) of around 1350-1370 and a TIT of a touch more. But not over 1400.

So I guess you could split the difference.

Let's see if John or Walter have any suggestions overnight.

Cheers :ok:

DB

[gassed budgie]

Hi Old Akro

It's been a few years since I've flown a Seneca and I can't remember fuel flows, power settings etc., but I currently get to fly between a couple of intercooled, twin turbo'd IO-540's every now and then.

The aeroplane has it's stock engine instrumentation, but there are no EGT gauges. Just a couple of TIT and fuel flow gauges.

Takeoff power shows up as 42" and 2500RPM with the fuel flow sitting on 175l/h per side. The TIT hovers around 1250°F or a bit more. I normally set climb power at 38" and 2400RPM. If the mixture is left full rich the TIT drops back to a bit over 1200°F and the fuel flow settles on 160l/h per engine.
However, I find that some times if the mixture is left full rich in the climb (the POH states full rich anytime you're above 75%), the aeroplane leaves long trails of black smoke everywhere it goes. It was enough for someone who knows the aeroplane to give me a call one day as I climbed out, suggesting that I had an engine fire!

For me, that indicates that the engines are running far too rich. With climb power dialled up I'll pull the mixtures back slightly, looking for 1350°F on the TIT's. The fuel flow comes back to a more reasonable 150l/h (although at 300l/h total, some might say that's still very unreasonable). I never have a problem with CHT's at any of the above power settings. The CHT sits rock solid on 320° in the climb all the way to FL200. It's only when the aeroplane gets above this altitude and the wastegates are fully closed, that the CHT might drift up to and nudge 340°F. That's still way below 400°F and I feel comfortable with that CHT at high altitude.

I realise I'm not talking TCM IO-360's here, but you were mentioning TIT's so I thought I'd compare notes.GB.

[Walter Atkinson]

Old Acro:

I concur with Jabba.

[Old Akro]

the aeroplane leaves long trails of black smoke everywhere it goes.

I've had that too. Received calls from the tower. Ours has been adjusted since then, but I still believe its richer at full power than the Continental "max allowable rich" graph. Thus I want to intervene manually to get a better condition.

If you have ever read the fuel flow adjustment procedure for a turbocharged engine it is quite complex, time consuming and requires calibrated gauges. I believe that hardly any LAME's do this and I suspect that few actually have the proper calibrated gauge set up. They just tweak it from the last position and ask the owner to report back. Proper adjustment requires full power climbs to the critical altitude - when is the last time that was done as part of a 100 hourly??.

But, I also think I'm discovering that the Continental fuel flow curves don't match (ie conflict with) some of their other specified operating limitations. This is the sort of thing that might happen if some data (ie the fuel flow curves) came from dynamo-meter run with perfect cooling and some restrictions came from real world testing and some came from good old fashioned boiler plating by guys sitting behind desks wanting to be conservative and add safety factors. - Which is the point John Deakins has been making for years!

[43Inches]

However, I find that some times if the mixture is left full rich in the climb (the POH states full rich anytime you're above 75%), the aeroplane leaves long trails of black smoke everywhere it goes. It was enough for someone who knows the aeroplane to give me a call one day as I climbed out, suggesting that I had an engine fire!

I found this with PA31s which I think you are referring to, happens mostly on cold mornings or if you don't warm the engines enough before departure. Cool engines especially oil can play all sorts of tricks with the density/differential controllers and waste gates. If its happening consistantly all the time then most likely a problem that needs fixing. Also if you flood start these engines everyone around will know as it belches black smoke everywhere and splutters to life slowly.

[Jabawocky]

Gassed budgie and 43"

I just had a quick peek at some data on that engine, and one that is properly set up ;) and the fuel flows when full rich were 42"/2570 = 154 LPH (40.5GPH) with a TIT of 1370dF and at 40"/2400 it was 136LPH (36GPH) with a TIT of 1300-1305dF.

You could do a rough scaling of this for 38/2400 and it would be 129-130LPH.

As 43" has mentioned with cold oil and cold atmosphere the density controllers will do their thing and they need to be set up right.

But one point to remember, and this applies to ALL ENGINES, no matter what, it is better to have a fuel delivery system slightly richer than slightly leaner Not drowning it though. Because no matter how hard you push the red knob in it will never flow more, but as the human FADEC you can control it back if need be. So be careful about having the LAME's reduce the flows unless they are ridiculous now. Better to have a fraction too much than too little.

All the best
DB :ok:

PS: If anyone wants to see this stuff and learn a heap, PM me your email address and I will keep you informed on when and where the next opportunity will be.

[Old Akro]

Hey Walter, is this a LOP problem ?????

https://www.youtube.com/watch?v=d_8Fc9qAZcw

:E

[Walter Atkinson]

LOL!

For whatever reason, it was an ICP problem.

i.e., Overboost; not rich enough ROP for the power setting; not lean enough LOP for the power setting; improper timing; pre-ignition, improper torque on the head--one or a combination of the aforementioned.

Whoever was running the engine wasn't paying attention. You could tell it was coming!

[Old Akro]

I think its an engine from a tractor pull type tractor. The good ol boys just going full noise I think. Diesel with mechanical injection by the looks. Diesels basically always run LOP!!! No throttle butterfly, power set by mixture.

[Jabawocky]

Watch the exhaust stack move before the let go. :}

Nice one Akro :ok:

[Richard Beekman]

IS this forum still active I have a Seneca V I'm looking for advice running LOP I have an engine monitor and pictures that I'll post for advice as well