Single Lever Power

[mmarien]

Lycoming started with an engine close to the TIO-540-AE2 found in a Piper Mirage. It’s the big-case, angle-valve-cylinder engine nominally good for 350 horsepower with twin turbos and intercoolers. The final IE2 engine will be called a TEO-540-A1A, and it will be an FAA-certified product. The mechanical differences between the TIO-540 and the TEO beyond the control system are minor, just slight changes in the head castings to accommodate the IE2’s knock sensors.

Knock sensing is the “killer application” here, a technology used widely in cars but thought impossible to implement in piston aircraft engines. Why? Acoustic knock sensing “listens” for detonation; in comparatively smooth, quiet car engines, this isn’t difficult. In fact, you can often hear engine ping from the driver’s seat. But an aircraft engine is, mechanically speaking, much noisier. Lycoming, however, says it has developed the right computer algorithms to detect detonation from the rest of the mechanical din.

The climb through FL180 at the same 140 KIAS—but at 36 inches MP—had the fuel flow down to 25 gph and a CHT range of 345° to 469°.

Do these temps seem high to you? Well, Lycoming says that the IE2 engine can operate and survive with much higher CHTs than we are accustomed to or comfortable with. The protection provided by the elaborate sensors and precise engine control allows operations at temperatures that would destroy a manually regulated engine.

The concept of single lever does start taking the pilot out of the control loop. So when something goes wrong like a ceramic breaking in a plug, I wonder how it deals with that? This is what concerns me the most.

So does this happen a lot with your engine? and what do you do when it happens David?

 

[DBRV10]

I see they note that the killer application is the knock sensor. And they are on the money with the reasons why the auto style never was going to work!

Now like I said before PRISM has been around a long time but not released to the market yet. It was developed in response to no lead. But the technology used is relevant to the Lycoming as I dare say they are doing the same thing GAMI did many years back. Knock sensing but not accoustically but via Pressure Pulse measurement. The GAMI dyno measures this at 1MHZ from memory. Quite a high sample rate!

Have a look at this spark plug and see if you see anything different.

[edit]So does this happen a lot with your engine? and what do you do when it happens David? [/edit] No, but I sure know exactly what to do and what not to. And if its a dark night over hostile country....I will surely have a life expectancy measured in minutes if I get it wrong. :'( I recently met a guy who had this happen, he inadvertantly did the right thing, and was not shark fodder. Which he would have been. Also lucky the single probe CHT and EGT was on that cylinder..... Your chances then are 1 in 4 or 6 so a good reson to buy a Dynon EMS

[edit]
The climb through FL180 at the same 140 KIAS—but at 36 inches MP—had the fuel flow down to 25 gph and a CHT range of 345° to 469°.[/edit]

What sort of statement is that? Were the CHT's all around 345 say +/- 20 or were they all around 469 +/-20 ?

From your comments elsewhere about CHT I think your green zone is a lot lower. Mine even lower thanks, I think we all know how aluminium alloys behave with temperature increase.

I doubt the heads are anything super special with respect to temp tolerance, but hey, if they are you beauty! The reason why water cooled heads say like a Rotax can be run closer to detonation is cooling capacity. Detonation is harder to create with stable temps.

 

[mmarien]

Thanks for the article. Lots of good stuff in there. But no matter how you say it, it's electronic ignition - part of single lever power.

If the statistics are correct, 80% of GA can run on 87 octane and don't have a problem with detonation while running on 100LL and won't have running 94UL. The attitude is there isn't a problem so why fix it, except for high performance engines. There will a problem for high performance engines when the inevitable happens and LL goes away. We aren't going to get two levels of octane. It's going to be 94UL when the hammer comes down. Parts of Europe already have it. That or 94UL for GA and some expensive hybrid for those that need it. The automotive industry used electronic ignition and fuel injection for economy 40 years ago when the supply of fuel was threatened. The aircraft industry is doing the same today because 100LL is going away.

I agree that aluminum weakens with temperature - it's a given. However, our uninformed limits seems to be modest in comparison to what Lycoming and GAMI (460F) suggest as safe limits. So you still haven't told us what you do "when something goes wrong like a ceramic breaking in a plug" IMHO I think it irrelevant to this topic. If anything electronic engine management goes a long way to prevent those types of events. At least GAMI thinks so. Give it a try. It might alleviate some of your fears.

Rhetoric aside, my quest here is to update my aircraft to the 21st century. If it was TBO'd I'd replace it with one of the new UL Power six cylinders. My engine isn't high performance. I've been running electronic ignition for a year. I had first start with multi port electronic fuel injection yesterday. The efi system has a ten year reputation of keeping planes in the air and claims prizes at Reno. I believe I'm in good hands. The ceramic on my automotive plugs won't break up. My plane won't fall out of the sky.

Next project is automatic electronic management of the prop pitch. I'm looking for suggestions.

 

[DBRV10]

So you still haven't told us what you do "when something goes wrong like a ceramic breaking in a plug" IMHO I think it irrelevant to this topic.

Sorry, I thought I had addressed this previously, or maybe it was elsewhere, and not here, so my mistake if so. I use this as a classic example of knowing what to make of your engine monitor and why understanding things is very important. This is not stuff I can teach here in a few posts. This is best done by attending an APS course.

So the story is this; Imagine you are flying over the Rockies at 14000', at night, Lowest Safe just below you, and you see the EGT on cylinder 5 drop a bit, and then you see a rising CHT that keeps ticking over, it is normally 365F and it is ticking over now at a rate of about 2 or more F per second, What is it and What do you do? Well the answer is it is Pre-Ignition (most likely a cracked ceramic or a helicoil tang pushed into the combustion chamber) and what you do about it is go full rich ASAP.

You can't shut down, you cant pull off heaps of power and you have nowhere to land within gliding range, and when the engine fails in about a minute or so, you will most likely perish.

Your only option is full rich. Probably to the point the engine almost drowns and stops, but this will kill off the pre-ignition. Changing the spark timing to something very retarded might do this for you, but remember Preignition is a self funding process, it uses residual heat like a glow plug to keep the process going, the spark is sent after the event. So it has minimal effect.

The fuel air ratio needs to become VERY hard to get going. And a very Rich mixture, with not a lot of compression (by the time the hot spot would normally arc it up) is about the only way to put the fire out, and let the sparks do the work a little later.

This stops your engine from being destroyed by one cylinder having its pistion destroyed and then pumping all the oil out, killing the remaining 5 or 3. And on 3 they run much worse than they do on 5.

And these failures happen, I can think of several right now. I had a guy in one of my lectures who had this exact thing happen, he did not know it. Luck was on his side, or he would be shark poop by now.

Have fun experimenting!

 

[purlee]

Let's come at this from a different perspective.

Independent control of boost, rpm and mixture becomes particularly important when flying for maximum range. Not only is flying at the right speed important, but also reducing fuel consumption, which is best achieved at low rpm, high boost and lean mixture.

Now, just in case you are thinking "I never fly for maximum range" let's consider the case where you are over water and suddenly discover that a fuel drain has been leaking for the last half an hour or so and you are now in a critical fuel state.

So, having flown across the occassional ocean in my time, here is how you handle it.

Immediately switch to only the leaking tank, if it has fuel left in it, that way you use all the fuel you can before you lose it.

Slow down to best range speed, this is almost always about 1.7 VS, so if you don't know the correct speed, (you really should), but you know what speed you stall "power off" in clean configuration, 1.7 times that speed is going to be close enough.

Reduce the rpm as far as you can, most light aircraft engines will come down to about 1900 RPM with reasonable boost, increase boost until the aircraft just flies level at 1.7 Vs and readjust the rpm to as low a value as possible.

We all know, don't we, that lean mixture produces high EGT and CHT temperatures, but leaned beyond peak, these temperatures cool down again! If you lean to the point where the engine runs rough and then richen until it just runs smoothly, you are flying as economically as you can, without over-temping the engine. Monitor CHT and EGT carefully and increase RPM slightly if they get too high.

"In extremis" remember that it takes power and fuel to carry weight, so, if safe to do so, jettison everything but the passengers and the liferaft!

As you burn fuel, Vs decreases, so should your speed and power. Done properly, you will be amazed at how much your "Air Miles per Gallon" will improve. I can't garuantee that you will make it, but you will maximise your chances.

The point of this discourse? You simply don't have that level of control with a single lever!