I took my M20F to FL220 (naturally aspirated)

[SkepticalJohn]

I'm late to the party on this post but found it strange that no one mentioned the magnetos... Flying a non-turbo aircraft (IE: one without pressurized mags) in the flight levels can cause arcing in the mags due to the lack of air to insulate the electrodes. This arcing can... will... damage your mags. A magneto doesn't work in a vacuum. Our turbo birds have pressurized mags for a reason. The arguments pro, fly-as-high-as-you-want-because-it-isn't-in-the-limitations-section, seem foolhearted to me. 

For a "cliffs notes" education, I'd suggest reading the paragraphs half-way down on the following page under the "High-Altitude Misfire"

https://www.avweb.com/ownership/whats-under-the-hood-magnetos/

I've no experience in non-turboed Mooneys, so I may be missing something?

[carusoam]

That sure is an interesting point SJ.

+1 for the electronic mags...(?)

Best regards,

-a-

[MikeOH]

While SJ is correct that unpressurized mags are going to have issues at high altitude, they would work just fine in a vacuum!  It turns out the arc potential reaches a minimum and then begins to INCREASE as the pressure continues to decrease; see Paschen curve: https://en.wikipedia.org/wiki/Paschen's_law

[FloridaMan]

On 5/16/2021 at 4:33 PM, SkepticalJohn said:

I'm late to the party on this post but found it strange that no one mentioned the magnetos... Flying a non-turbo aircraft (IE: one without pressurized mags) in the flight levels can cause arcing in the mags due to the lack of air to insulate the electrodes. This arcing can... will... damage your mags. A magneto doesn't work in a vacuum. Our turbo birds have pressurized mags for a reason. The arguments pro, fly-as-high-as-you-want-because-it-isn't-in-the-limitations-section, seem foolhearted to me. 

For a "cliffs notes" education, I'd suggest reading the paragraphs half-way down on the following page under the "High-Altitude Misfire"

https://www.avweb.com/ownership/whats-under-the-hood-magnetos/

I've no experience in non-turboed Mooneys, so I may be missing something?

For what it’s worth, the Rockets can fly up to FL280 and do not have pressurized mags. 

[aviatoreb]

Just now, FloridaMan said:

For what it’s worth, the Rockets can fly up to FL280 and do not have pressurized mags. 

But the tsio520nb mags are designed with altitude flight in mind.  Don’t they?

[Ibra]

On 5/16/2021 at 10:33 PM, SkepticalJohn said:

Our turbo birds have pressurized mags for a reason

Because they are turbos running at high 100% power? so the mags risk to run out of ambiant pressure before the engine runs out of manifold pressure?

The physics in non-turbo engine will make sure engine will run out of air & power steam probably before the mags runs out of air

Mags misfiring at high altitudes happens at high 100% power (most likely in turbo) but will disapear at lower 45% power (normally aspirated), natural power reduction allow easy spark plug firing as there is less and less pressure in tbe combustion chambre, so less risk of arcing or rough running, if you are happy to reduce power on turbo to normally aspirated level, the engine will run smoothly without pressurized mags, it's only in high power where misfiring and arcing are big concerns 

The service ceiling is defined as the place where you can't have more than +100fpm climb, that depend on engine but also on wings aerodynamics, most likely the wings and thin air will outclimb low power NA engine (or turbo on low power) way before the mags wiggle !

Edited May 17, 2021 by Ibra