Backcountry Pilot • Manifold Pressure at altitudes

Manifold Pressure at altitudes

Lycoming, Continental, Hartzell, McCauley, or any broad spectrum drive system component used on multiple type.
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Re: Manifold Pressure at altitudes

whee wrote:Can anyone report the MP they see on their Continental with cross flow cylinders (intake on top of the engine)? I'm wondered if there is any ram air effect from intake being on the pressure side of the cowl.

My father in law has that same engine you're using, and he flies high all the time - I will ask him what he sees.
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Re: Manifold Pressure at altitudes

If you really want to learn about engine operations, you should take the Advanced Pilot Seminar (https://www.advancedpilot.com/). The APS course will bring your engine operation knowledge from "near zero" to "very competent" over a weekend. It's not cheap (about 1 AMU for the classroom course, or half that for the online course), but as a "graduate" of the course, I can tell you it's probably the best AMU I've ever spent on aviation training.

The APS course is taught in Ada, OK. If you sign up for the live course, they give you access to the online course for a full year (same as if you purchased that course), and encourage you to complete the online course before you even come to Ada. I did the online course multiple times before I went, earning near-perfect scores on the self-evaluation at the end. Yet I was still amazed at how much more I learned in the live course, even beyond everything I learned during all that prep. It was absolutely, hands down, the best education experience I've ever had. (And as a retired IT guy, I attended seminars, webinars, and all kinds of continuing education on a near weekly basis for 20+ years...)

The guys have access to one of (if not THE) most sophisticated aircraft engine test cells in the world (shared with Tornado Alley Turbos and GAMI), and the course is very "fact-based". One of the co-developers of the course is the chief engineer for TAT, and he led the development of the Turbo-Normalized version of the Cirrus SR-22. In fact, these guys actually wrote the manual for engine operations for that airplane. They also developed the aftermarket turbo-normalizer system for Bonanzas that is simply incredible... As a result of that "heavy" Continental background, there is a slight "fuel-injected Continental" information slant to the course, but they also talk about Lycoming and carbureted engines. In fact, everything they teach is every bit as applicable to your 4-stroke lawnmower engine...

The course is so good that Continental Motors is slowly sending all of the tech specialists and engine reps through the course. At the seminar I attended, there were four guys from Continental in attendance. When it was over, I talked to a couple of them, asking if they learned anything new... The response (paraphrasing slightly) was "Are you kidding? I (we) learned probably about as much as you did... This information just isn't taught in any of the pilot or A&P training courses. The guys back at CM told us to expect to have our minds blown, but this... This was just amazing!"

And just to be clear, I have zero relationship with the APS guys, other than as an extremely satisfied (and much more educated) customer. Highly recommended - 5 Stars!
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Re: Manifold Pressure at altitudes

I have learned a lot about aircraft engine operation that I thought I already knew by virtue of my automotive background. What I am learning is the BIG difference between auto and aircraft engines is that aircraft engines have FIXED timing. The same threat of engine destruction exists in automobiles that still exists in aircraft which is detonation. The automotive world developed load dependent spark curves 60 years ago using spring loaded centrifugal weights connected to the distributor shaft along with engine manifold pressure sourced actuators that modulated ignition timing according to load conditions. They have since developed extremely reliable electronic ignition systems that have been in use since the 70's. Aircraft still have a FIXED timing that pilots need to be wary of conditions that could be a costly or even deadly mistake. I blame the certification process to some degree and pilot resistance to product development for the remainder for this worrisome dynamic existing today.

This link is a good article about why proper engine ops is essential to the pilot; a long read but very good. I suspect it contains a lot of what the APS school is about:

http://www.avweb.com/news/pelican/182084-1.html

Better ignition systems for aircraft are on the horizon and working to get FAA certification now. I can't wait to upgrade my plane when this all works out. Pilots have a pretty intense workload already that engine ops should not be a threatening part of that equation.
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Re: Manifold Pressure at altitudes

DeltaRomeo wrote:This link is a good article about why proper engine ops is essential to the pilot; a long read but very good. I suspect it contains a lot of what the APS school is about:

http://www.avweb.com/news/pelican/182084-1.html

Not surprising that the info in the article would convey some of the same material as the Advanced Pilot Seminars. After all, the author of the "Pelican's Perch" series is John Deakin, who was the driving force behind creating the APS. He, along with George Braly and Walter Atkinson developed the course and all three participate in teaching it.

That said, John would be the first to tell you that he (along with the others) has learned A LOT since those articles were written, and the APS course is constantly updated with their learnings. As part of my preparation to attend the APS, I read John's entire "Pelican's Perch" series. And I still learned more in that seminar that I could believe was possible. It's really THAT good...
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Re: Manifold Pressure at altitudes

That is all well and good information a pilot should have. My frustration is that level of study, awareness, and technique (i.e. additional pilot workload) are necessary only because we are chained to an antiquated technology that permits that risk to exist in the first place. At this point in time it is completely unnecessary to subject oneself to that risk if it weren't for the certification process that holds applying new technology back.
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Re: Manifold Pressure at altitudes

DeltaRomeo wrote:That is all well and good information a pilot should have. My frustration is that level of study, awareness, and technique (i.e. additional pilot workload) are necessary only because we are chained to an antiquated technology that permits that risk to exist in the first place. At this point in time it is completely unnecessary to subject oneself to that risk if it weren't for the certification process that holds applying new technology back.


This is the core of the problem. GA pilots and pax will still die at the same rates and for the same causes in the next 50 years as they did in the past 50 years unless something changes. That means changes to training (very low likelihood of moving the needle meaningfully), operating regs (who knows), and certification standards to promote development of tech to displace the Hudson and Studebaker tech that is GA. The FAA has traditionally set the standard for other governing bodies with regards to certification, which means that meaningful progress is unlikely in the certified category for GA just about anywhere in the world.
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Re: Manifold Pressure at altitudes

lesuther wrote:
DeltaRomeo wrote:That is all well and good information a pilot should have. My frustration is that level of study, awareness, and technique (i.e. additional pilot workload) are necessary only because we are chained to an antiquated technology that permits that risk to exist in the first place. At this point in time it is completely unnecessary to subject oneself to that risk if it weren't for the certification process that holds applying new technology back.


This is the core of the problem. GA pilots and pax will still die at the same rates and for the same causes in the next 50 years as they did in the past 50 years unless something changes. That means changes to training (very low likelihood of moving the needle meaningfully), operating regs (who knows), and certification standards to promote development of tech to displace the Hudson and Studebaker tech that is GA. The FAA has traditionally set the standard for other governing bodies with regards to certification, which means that meaningful progress is unlikely in the certified category for GA just about anywhere in the world.


Actually, I'm concerned that the new ACS standards, especially as it applies to slow flight and stall training, will have the opposite of the FAA's intended effect--more, not fewer, LOC accidents, as students will learn less about aerodynamics "for real".

The low tech nature of aircraft engines, and the very slow adoption of higher tech, certainly is directly related to certification stodginess. I'd suggest that Hudson and Studebaker engine tech was actually more advanced than much of today's GA engine tech. The Hornet didn't win a series of NASCAR races by being low tech! The ridiculous cost in both time and money to obtain STC certification makes adoption of things like electronic ignition virtually out of reach for most of us, when the benefits are so minimal (slight increase in fuel economy, somewhat easier starting)--if I wanted to make the conversion, it'd be hard to justify financially.

But I ramble.

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Re: Manifold Pressure at altitudes

Got another trip under my belt; learned a lot about turbulence :shock: . Spent 8.5 hrs flying into a head wind and my experience now teaches me the value of flying above cumulus clouds. In the western states the terrain is already fairly high so if your aircraft ceiling is 15,000' getting above the cumulus isn't possible; you just have to take your licks or fly mornings or night. Flying under cumulus is decent if they are fairly connected enough to create shade that reduces convective activity. The sunny open spots are rough. It was fairly easy to avoid the falling shafts of heavy rain (and air). Although it is tiring its very akin to operating a tractor for long days and those of you here that have done or do that still you know what I mean. Anyone not accustomed to the tractor environment will have greater issue with this flying environment.

I made notes of manifold pressure readings at various altitudes and it was interesting to find that I could no longer make 24" by 5000' MSL. I was at WOT by then and didn't expect that condition until 7000'. Some more numbers:

6500' 22" @ 2250 rpm
7500' 21.5" @ 2400 rpm
9000' 20" @ 2400 rpm
11,500' 19" @2400 rpm
Static manifold pressure at KGNT was 23" (6500 MSL)

This experience was good and will allow for increasing the comfort prospects for pax; important because without pax you diminish many of your mission opportunities. It will also help planning for avoiding the encounter when performance is less than the challenge. Hope this is helpful for someone else here looking for the same kind of info.
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Re: Manifold Pressure at altitudes

Oh man, I know what you mean about flying with pax in turbulent air. My wife isn't a fan of the bumpies but wanted me to take her to a wedding the other weekend - departing mid-day with a SCT/BKN layer above us. It was one of those days where you could really feel the difference between shaded ground and sunny ground! She did pretty good, I was proud of her.

DeltaRomeo wrote:I made notes of manifold pressure readings at various altitudes and it was interesting to find that I could no longer make 24" by 5000' MSL. I was at WOT by then and didn't expect that condition until 7000'.


What was the OAT? Or specifically, what was the density altitude?
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Re: Manifold Pressure at altitudes

CamTom12 wrote:What was the OAT? Or specifically, what was the density altitude?


OAT varied as the trip spanned 750 miles and flight altitudes of 4500 to 11,500'. I suspect at 5000' it was about 60º F but I didn't make note. I do recall activating the cabin heat as it got chilly as I continued to climb to fly over towered airspace.

On another note, I managed to squeeze 7.7 GPH out of one leg of the trip :D . This was a surprise too as my leaning and performance settings have been fairly routine and unchanged. I had been running mostly 8.5 before and since. Only thing I can suspect there is that maybe the fuel pump meter at the airport I filled up at may be reading poorly and in my favor... :-k
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Re: Manifold Pressure at altitudes

DeltaRomeo wrote:
CamTom12 wrote:What was the OAT? Or specifically, what was the density altitude?


OAT varied as the trip spanned 750 miles and flight altitudes of 4500 to 11,500'. I suspect at 5000' it was about 60º F but I didn't make note. I do recall activating the cabin heat as it got chilly as I continued to climb to fly over towered airspace.

Ah, gotcha. I'd guess your DA was probably close to 7,000 ft.

DeltaRomeo wrote:On another note, I managed to squeeze 7.7 GPH out of one leg of the trip :D . This was a surprise too as my leaning and performance settings have been fairly routine and unchanged. I had been running mostly 8.5 before and since. Only thing I can suspect there is that maybe the fuel pump meter at the airport I filled up at may be reading poorly and in my favor... :-k


Nice!
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