Mike Busch at OSH 2021

[Colonel]

When I used to fly Neil's S1 I would see 3200 RPM easy. I have some video, somewhere.

The sonic crack off the prop was really obnoxious

You really can't easily compare car/motorcycle engines with airplane engines. It's
just silly.

One of my motorcycles has a 15,000 RPM redline (really) and it makes 120 hp
at 13,800 RPM which I probably have spent 42 milliseconds passing through, with
the engine making it's rated torque at that RPM.

Not bad for 600cc:

0-60 mph 2.9 seconds
1/4 miles 10.56 sec. @ 130.77 mph

It's a liquid-cooled inline four with DOHC. Not much in common with an AEIO-540.

But, you never see one of these "advanced" engines on an airplane. Porsche tried
and lost hundreds of millions of dollars.

[David MacRay]

You really can't easily compare car/motorcycle engines with airplane engines. It's
just silly.

Fine. How about locomotives and Priuses?

[Squaretail]

What part of "continuous" and "maximum power" is Mooney wrong about, according to you?

I think you and I are talking about slightly different (but related) things.

That's the maximum power they want you to run at, its not the maximum power that engine can possibly produce. Not sure if you've ever had a prop governor fail on you before, but that engine can certainly get way higher than 2700 rpm. Also in your example of the mooney, it doesn't produce 200 BHP unless its at sea level, which its unlikely to be flying at. I mean show me the cruise performance chart where its maintaining 200 BHP @ 3000'. Normally aspirated engines just can't produce all their power to their full envelope of flight. That's part of why I agree with you with your assessment of Mike's red-box alarmism - most planes just can't be run in that box, you only got to worry about it when you start being able to increase how much power (and heat) those engines can generate.


If we add a turbo into the mix, its even more obvious that aero engines aren't operating at the engine's maximum potential - or at least the manufacturer does not recommend doing it for lengths of time. As I recall, both the TCM TIO-520 and the Lyc TIO 540 books say you can use All levers to the wall to no ill effect for a max 5 minutes, so obviously they don't want you to run that continuously.

but a Lycoming is perfectly happy
at max MP and max MP continuously,

Because they have limited that in some fashion. As above, the max number they list is the max number they approve of, not what it can actually do. The only difference really between aero engines and car engines is the certification process that has been mandated upon the aero product. Economics has a larger role to play than technology. TCM and Lycoming have cornered the market, and the current regulatory process helps them keep the market cornered, and the piston market is to small for anyone to really dabble in. I mean I've had the chance to fly behind some V-8s before and they seem to be fine. The power to weight and reliability seem fine. One guy I knew had dumped millions in to trying to get it certified, lots of which has nothing to do with actually proving the engine is safe and reliable. Automotive engines will run all day long at full throttle, though you usually don't find that in cars, but rather other industrial applications. For example, lots of construction equipment is hydraulically driven, and when you work with it, you throttle it up when you start, and throttle it back when you finish. You can run it for as long as you got fuel non-stop at full throttle application. And do that day in and day out with minimal maintenance. Same engines are used in compressors and generators where they might run continuously for days or weeks. So don't tell me that only TCM and Lycoming have found the secret to long running at max power.

But as before, that's only a small point of quibble. I don't think the issue of long running reliability at high power setting is what's keeping GM or Honda out of making airplane engines. It surprises me that BMW doesn't make anything. I mean they used to, surely they could figure it out. Be neat if they still made 801s even if I am skeptical of German made stuff.

[digits]

As I recall, both the TCM TIO-520 and the Lyc TIO 540 books say you can use All levers to the wall to no ill effect for a max 5 minutes, so obviously they don't want you to run that continuously.

Note that a lot of limitations like that are pretty useless because they don't specify when you can start the clock again. 5 minutes max, go to idle for 2 seconds, and back on for 5? Or 5 minutes per hour? Per flight? Not sure about the specific engines mentioned above, but it just bugs me when I see similar limitations on turboprop or jets, and they don't specify it further.

[David MacRay]

As usual I’m with digits. These books are great, but they’re full of loose guidelines open for interpretation by flight instructors, who then make up funny laws for flying, they expect you to memorize said laws just in time to change their minds.

“We don’t do that anymore.” Fine pass me the checklist..

[Squaretail]

As I recall, both the TCM TIO-520 and the Lyc TIO 540 books say you can use All levers to the wall to no ill effect for a max 5 minutes, so obviously they don't want you to run that continuously.

Note that a lot of limitations like that are pretty useless because they don't specify when you can start the clock again. 5 minutes max, go to idle for 2 seconds, and back on for 5? Or 5 minutes per hour? Per flight? Not sure about the specific engines mentioned above, but it just bugs me when I see similar limitations on turboprop or jets, and they don't specify it further.

The main point is if it was fine to run it continuously like that, that's what would have been listed as its "max continuous power".

[Colonel]

if it was fine to run it continuously like that, that's what would have been listed as its "max continuous power".

Which is exactly what Mooney says.



I don't think that's unclear. You can run your Lycoming in your Mooney M20J (where I got this)
wide open continuously, with no ill effects.

I really have no idea why pilots don't like engines to run RPM or produce torque.

Nobody cares, but what hurts an engine is not a lot of RPM - Mooney says overspeeds to nearly
3000 RPM are no problem - but particular RPM's with resonant torsional frequencies, particularly
with no crankshaft counterweights.

Has no one ever flown an aircraft with a yellow arc in particular RPM ranges?

-- EDIT --

From that very same POH:



Pilots think they are "babying" the engine with low power settings, doing exactly what Lycoming
says not to.

Yeech. No wonder break-in is such a problem. I know I'm weird, but I think it's great fun to run
an airplane with the throttle wide open for an hour at the surface. Start with RPM max, then
back it off 200 RPM for a bit, then back to max RPM. Full rich mixture, of course. You're going
to pull a little G doing it, if you want to stay in the same zip code.

If you have a normally aspirated engine (99% of the fleet) you can generally run all the RPM and
MP you can get. Just keep the temps down below redline. That's what ages metal - over-temping.

You really don't want to know how I operate my TCM IO-360. 50 years, no problems so far.



I used to run the GTSIO-520's in the 421's I flew to (gasp!) 3400 RPM. Sounded great, they lasted forever when I flew them.



Not so much with the retired Air Canada pilots, who destroyed both 421 engines in 100 hours.

That's why I really hate to sell an airplane. The next guy generally kills it, which the airplane doesn't
deserve. Do you hate airplanes? I don't. I rather like them, more than most pilots.

I can't stand cruelty to dogs or airplanes. Sorry if that hurts anyone's feelings, but if I catch you
abusing either, you will not enjoy what happens after.

[Squaretail]

I'm just not communicating what I'm thinking well enough, and that's on me.

But further thought on the matter, what I'm trying to express is maybe borne out by the example of the Cessna 175 powered by the undeservedly maligned GO-300. Now the GO-300 is essentially an O-300 with a gear box. Now the O-300 installation like on my old plane was rated in the book similar to above at 145 BHP at 2650 RPM as its max. However its really the prop which was a limitation on the limitations of that engine, because the GO-300 runs happily right up to 175 BHP at 3000 RPM. Obviously the O-300 in the 172 wasn't being tapped for its real full capacity, and makes you wonder what sorts of RPMs these engines could really output if you had the right gearing to maximize it. So from a design perspective, to me its not obvious that a limiting factor on aero engine design isn't that it can run at max rated power for prolonged amounts of time, at least that's not an advantage it holds over an automotive engine. My truck red lines at 6000 rpm, my bike at 12,000, and each of them obviously extracts the maximum power somewhere in that arc. Airplane engines are simply limited by having to transmit that power to a propeller which itself is limited on the rpm that turns that power into thrust. I haven't researched my truck as well, but as I recall, the bike puts out its max horse power at 72 BHP at 9000 rpm, so with the use of a gear box and transmission, that engine's max power is in the middle of its acceptable power band as opposed to at the end of it like most airplanes.

But that's a long way of making a small point, but in a round about way of agreeing with you about the idea of red boxes of doom.

[Colonel]

I'm really weird. I LOVE geared engines!

Most people hate them, which is a pity.

I loved the TCM GTSIO-520 in the C421. However, you had to be careful not to drive
the engine with the prop. The gear reduction unit seemed to be happiest if you
only transferred torque from the engine to the prop - NOT the other way 'round.

Contrast that with the Pitts (or any other aerobatic airplane) with a constant
speed prop. You can fly insane approaches with that (direct drive) setup. Sean
Tucker, Skip Stewart will fly wide open, Vne to short final. Throttle comes back
to idle on very short final. The drag from the three prop blades throws you
forward into the shoulder harnesses. If you time it right, you de-celerate power
off to 120 MPH over the numbers, plop the mains on, and drive down the runway
with your tail in the air, stick going fully forward as you slow down. Optionally
add power and brakes to taxi in with the tail still up.

Don't do that with a geared engine.

I loved the geared P&W engine in the clip-wing hotrod Harvard I flew with the giant
geared metal 3-blade R-1340-AN2. Not your father's T-6. Fun during the hhead pivot.



Like the zoomies? Didn't sound like a T-6 at all. No prop bark as it went by, only engine.

And, I loved the geared Lycoming GO-480 engines in the Twin Bonanza. Everyone hated them,
but they sounded better than anything else on the field.



See, here's a secret. All airplanes are different. Some do stuff much better than others.
Some do stuff much worse than others. Every time you meet a new airplane, spend a little
while and make friends with it. Learn what it does well, and what it does badly.

When you fly the airplane, do what it does well, and don't do what it does badly.

I know this will hard to understand for some, and will be heresy to the egalitarians, but
Dear Old Dad didn't have problems with the dreaded T-tail pitchup as a nuclear weapons
test pilot in the F-104, because he never stalled it.

See?

[Squaretail]

I'm really weird. I LOVE geared engines!

Well that's something we can agree upon. While I know its not as cool, I really liked the Skylark, the extra performance was transformative for the STOL characteristics of the Cessna airframe. Its too bad that engine didn't catch on. The bigger prop helped too, since the hub was a few inches higher than the regular 172, and they put it to good use.