Oh Continental, what have you done now?

The so-called "counterweights" also have pins and bushings that retain them, arranged so that they are mechanically a very short length pendulum. They each have a comparatively heavy weight. The effective pendulum length depends on the pin and bushing diameter differences, such that the effective pendulum lengths are less than 1/8 inch or so. This is hard to imagine but the natural frequency of each pendulum weight also depends on the centrifugal acceleration of each mass which of course also directly depends on the rpm of the engine. The faster the crank rotates, the higher the natural frequency of the pendulum. The tuning of these pendulum(s) is critical and depends on the diameter differences of those very precision hard bushings and pins. But since the natural frequency goes directly as engine RPM, they are very effective for reducing a certain natural harmonic vibration of the crankshaft propeller driveline rpm (called order).

They were a wonderful invention of the 1930s that enabled the high hp engines of WW2. Prior to their development crankshaft and propeller torsional failures were common.

The same pendulum principles are used to reduce sway in high rise buildings but that's another order of magnitude and another story.....
 
Thank you, @nrpetersen. That's a big help, and an interesting backstory, too.

Do other kinds of piston engines also have these moving-pendulum weights on their crankshafts? I'm thinking of automobile engines and diesel engines.
 
NoHeat said:
Thank you, @nrpetersen. That's a big help, and an interesting backstory, too.

Do other kinds of piston engines also have these moving-pendulum weights on their crankshafts? I'm thinking of automobile engines and diesel engines.
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There are various ways of counteracting torsional vibrations including pendulum weights, fixed mass weights, and even entire secondary shafts turning solely to balance a primary shaft. All depends on application.
 
NoHeat said:
Dumb question: Why don't they just cast the counterweights into the crankshaft itself, instead of adding separate pieces that must be attached?
Click to expand...

Because they are DYNAMIC. Meaning they move.
 
Do other kinds of piston engines also have these moving-pendulum weights on their crankshafts? I'm thinking of automobile engines and diesel engines?

Probably some bigger diesel engines might, but I'm not aware of any car engines that use the same damper concept. However, most car engines have a (torsional) inertia damper on the front side of the engine. They use the built-in rubber ring as the spring. You can sometimes tell this as in the winter the spring gets very stiff and the damper isn't anywhere near as effective and it sounds terrible until the rubber warms up. You can also tell the effect of the front damper as that mass is resonating on the rubber especially near idle, where you can hear the fan belt squeaking as it also tries to torsionally vibrate the fan. It is the same overall concept, tho car engines have a flywheel at one end and the damper assembly at the other end of the crank. aircraft use the propeller as the flywheel and put the damper at the other (back) end of the crank. OK there are some other more complex higher order modes of crank/propeller vibration and a bunch of other compromises such that other balance weight systems are located elsewhere on the crank length.

Aircraft engines use the pin/inertia type of damper because they are so effective under most conditions. Aircraft operate with a near-constant RPM and a load (propeller) that contributes its own dynamic properties. As a simplification, if you could ride (spin) on the spinner with x-ray vision, and see into the engine you would see the back of the crank vibrating to-and-fro, while the propeller tips go fro-and-to (read that carefully). The frequency is about 200 Hz (just below middle C on a piano). If the damper assembly(s) become mis-tuned for example, the result is the alternator on the engine back gets one helluva vibrating ride trying to follow the crank gear.

I could go on, but that's already more than you wanted to know....
 
nrpetersen said:
As a simplification, if you could ride (spin) on the spinner with x-ray vision, and see into the engine you would see the back of the crank vibrating to-and-fro, while the propeller tips go fro-and-to (read that carefully).
Click to expand...
And just to add, its the reason you put 2 velometers on an engine to perform a spectral analysis as the front side can be within limits but the aft end can be rattling the paint off depending on the frequency. There was a good article in Kitplanes last year (?) on balancing that gave a decent layman's explanation on the effects of vibrations from the engine and prop.
 
nrpetersen said:
Do other kinds of piston engines also have these moving-pendulum weights on their crankshafts? I'm thinking of automobile engines and diesel engines?

Probably some bigger diesel engines might, but I'm not aware of any car engines that use the same damper concept. However, most car engines have a (torsional) inertia damper on the front side of the engine. They use the built-in rubber ring as the spring. You can sometimes tell this as in the winter the spring gets very stiff and the damper isn't anywhere near as effective and it sounds terrible until the rubber warms up. You can also tell the effect of the front damper as that mass is resonating on the rubber especially near idle, where you can hear the fan belt squeaking as it also tries to torsionally vibrate the fan. It is the same overall concept, tho car engines have a flywheel at one end and the damper assembly at the other end of the crank. aircraft use the propeller as the flywheel and put the damper at the other (back) end of the crank. OK there are some other more complex higher order modes of crank/propeller vibration and a bunch of other compromises such that other balance weight systems are located elsewhere on the crank length.

Aircraft engines use the pin/inertia type of damper because they are so effective under most conditions. Aircraft operate with a near-constant RPM and a load (propeller) that contributes its own dynamic properties. As a simplification, if you could ride (spin) on the spinner with x-ray vision, and see into the engine you would see the back of the crank vibrating to-and-fro, while the propeller tips go fro-and-to (read that carefully). The frequency is about 200 Hz (just below middle C on a piano). If the damper assembly(s) become mis-tuned for example, the result is the alternator on the engine back gets one helluva vibrating ride trying to follow the crank gear.

I could go on, but that's already more than you wanted to know....
Click to expand...
This guy engines…
 
[I]Bell206 said:
And just to add, its the reason you put 2 velometers on an engine to perform a spectral analysis as the front side can be within limits but the aft end can be rattling the paint off depending on the frequency. There was a good article in Kitplanes last year (?) on balancing that gave a decent layman's explanation on the effects of vibrations from the engine and prop.[/I]
Click to expand...
That's radial vibration of course. The frequency is the rpm, and not a torsional harmonic. Torsional vibrations are so spooky in that they really don't manifest themselves to us mere mortals. Instead they just shed prop tips and wreck alternator drive belts.

The 172M that I had for 30 years had an obvious torsional vibration cruising at very low rpm (like 1950 rpm or 32 revs/sec). Most people would probably just call it a harshness. I could hear it ring slightly below middle C (256 Hz), which could be the 6th harmonic of 32 revs/sec. There is no 6th order damper on the Lyc O320-E2D engine so I could demonstrate it to most any passenger and then they could then hear it too (hum a few bars please).

Obviously I certainly never cruised there. (Numbers are from memory and approximate)
 
nrpetersen said:
Torsional vibrations are so spooky in that they really don't manifest themselves to us mere mortals.
Click to expand...
Is there not a coupling effect between radial/axial vibs and torsional vibs? However, I could be wrong as it was many years ago when I first heard of this. We had a helicopter tail rotor driveshaft that was eating Thomas couplings (stacked, flexible disc packs). Tech support had us re-aligning and re-balancing the shaft multiple times to no long term effect. One of the engineers finally showed up and after checking our work had us point a Strobex at the disc pack from a specific angle which showed the pack deforming in a rhythmic "axial" manner. He said it was a torsional vibration but I thought he said it should have also shown up in one of the other balance checks. We changed the driveshaft and all went away. I can see how spooky that would be especially with a crankshaft.
 
An interesting example of torsional vibration coupling to axial (but not radial) can be seen by looking sidewise at a running propeller against a dark background while someone else varies the engine at moderate rpms. The prop blades can then be seen as vibrating (actually flexing) out of its rotational plane - like 1/2 inch (!) at various moderate (like maybe around 1200 rpm). It is the propeller deflection matrix analysis that enters into this although this flexing/flapping mode is not particularly damaging. Instead it is the higher frequency (~200 + Hz) ringing in the chordal direction of a prop blade that can propagate a leading edge stone pit to a blade shedding crack, that the mass damper systems address.

Vibration can show in weird ways. You saw one of the most-weird in that tail rotor driveshaft. That would have been a real challenge for that engineer but the Strobex was definitely the way to visualize the mode. Fun and interesting! :cool:
 
AD has been issued. It includes some additional info on failures and does not exempt 200hr TIS engines.
AD 23-04-08
 
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So how many planes/engines are we taking about here. Sounds like a lot!
 
So far, reports I have seen of aircraft that have been inspected, there have been no issues found. It will be interesting to see how many bad ones there are.
 
Pinecone said:
So far, reports I have seen of aircraft that have been inspected, there have been no issues found. It will be interesting to see how many bad ones there are.
Click to expand...

Like a function of how many bad assemblers in the pool. If there’s 12 assemblers and one bad guy, I’d expect something like a 1:12 ratio for bad motors. Maybe less.
 
The local shop sent out an email today. Has to be done before next flight if impacted. Costly
 
Did FAA just "ground" all aircraft with a Continental engine??
I just received this email . .

NOTE: It states "affects any crankshaft assembly on a Continental Engine"

email_template.gif

For Immediate Release
Notice Number: NOTC2875


For Immediate Release - AIRWORTHINESS DIRECTIVE (AD) AFFECTING CONTINENTAL ENGINES


Docket No. FAA-2023-0172; Project Identifier AD-2023-00265-E; Amendment 39-
22355; AD 2023-04-08]
RIN 2120-AA64

This AD and final rule is effective February 23, 2023 and affects any crankshaft assembly on a Continental Engine. Due to improper installation of the counterweight retaining rings during manufacture loosening of a counterweight retaining ring may result in the loss of retention of the counterweight. If not addressed, the condition could result in catastrophic engine damage and possible engine seizure.

An inspection of the crankshaft is required prior to further flight or a ferry permit must be obtain to fly the aircraft to a place where the inspection can be performed.

For further information see https://www.federalregister.gov/doc...ospace-technologies-inc-reciprocating-engines

Guy Minor

Aviation Safety

Airworthiness Program Manager, National FAA Safety Team (FAASTeam), AFS-850

General Aviation and Commercial Division, AFS-800

guy.d.minor@faa.gov

Cell: 707-704-3530
 
A1Topgun said:
Did FAA just "ground" all aircraft with a Continental engine??
I just received this email . .

NOTE: It states "affects any crankshaft assembly on a Continental Engine"

email_template.gif

For Immediate Release
Notice Number: NOTC2875


For Immediate Release - AIRWORTHINESS DIRECTIVE (AD) AFFECTING CONTINENTAL ENGINES


Docket No. FAA-2023-0172; Project Identifier AD-2023-00265-E; Amendment 39-
22355; AD 2023-04-08]
RIN 2120-AA64

This AD and final rule is effective February 23, 2023 and affects any crankshaft assembly on a Continental Engine. Due to improper installation of the counterweight retaining rings during manufacture loosening of a counterweight retaining ring may result in the loss of retention of the counterweight. If not addressed, the condition could result in catastrophic engine damage and possible engine seizure.

An inspection of the crankshaft is required prior to further flight or a ferry permit must be obtain to fly the aircraft to a place where the inspection can be performed.

For further information see https://www.federalregister.gov/doc...ospace-technologies-inc-reciprocating-engines

Guy Minor

Aviation Safety

Airworthiness Program Manager, National FAA Safety Team (FAASTeam), AFS-850

General Aviation and Commercial Division, AFS-800

guy.d.minor@faa.gov

Cell: 707-704-3530
Click to expand...

Read the final rule at the link given. You will have your answer.
 
I narrowly avoided it. My new IO-550 just missed the serial number range here.
 
TCABM said:
How many motors have you gone through in the last few years?
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My GO-435 died in 2001. I put in a 9-hour IO-550-B (int was part of an A36 Bonanza that immediately went into turbo prop conversion). In 2016, that engine, as we say in NASCAR, blowed up. I put another brand new IO-550-B while also changing the engine instrumentation to an MVP-50 during that renovation. Unfortunately, my mechanic suffered a stroke in the middle of this which led to a year long delay before he could recover and I could get another mechanic to check over everything he had done.
 
Does the AD require an IA to check the crankshaft serial number list in the AD against the engine logbook before starting the engine, or can I actually check my own obviously-not-that-new logbook and fly my plane? Does anyone else remember the AD on PA-28 fuel selector placards that temporarily required a licensed mechanic to look at it and say that the thing in the plane didn’t look like the picture in the AD?
 
flyingron said:
I narrowly avoided it. My new IO-550 just missed the serial number range here.
Click to expand...
Mine is outside the SN range and during assembly, the overhauler noted the clips to be inserted incorrectly.
Sorry if this affects anyone’s sleep tonight.
 
“The manufacturing quality escape has resulted in ground engine seizures and an in-flight loss of engine oil pressure, which could lead to catastrophic engine damage, engine seizure, and consequent loss of the aircraft.”

That’s from the AD. So there was one in-flight failure. I wonder what the outcome was.
 
I am always happy to hear new euphemisms. Part of me revels in being in golden age of word smithing. Another part says we have to be close to maxing out.

But then comes along something like "manufacturing quality escape" and my faith in humanity's ability to convolute anything is restored.

I have whoever came up with that one got some reward, because that was good.
 
iamtheari said:
Does the AD require an IA to check the crankshaft serial number list in the AD against the engine logbook before starting the engine, or can I actually check my own obviously-not-that-new logbook and fly my plane? Does anyone else remember the AD on PA-28 fuel selector placards that temporarily required a licensed mechanic to look at it and say that the thing in the plane didn’t look like the picture in the AD?
Click to expand...
Actually a PP could sign off that AD on their own plane. I was a student at the time, owned a plane that was affected by the AD and had to get an AP to sign it off. What I found absurd was that getting my PP would magically make me qualified to say the stickers on my fuel valve looked like the correct picture. The letter L and the letter R were in the right place.
 
guest user said:
I am always happy to hear new euphemisms. Part of me revels in being in golden age of word smithing. Another part says we have to be close to maxing out.

But then comes along something like "manufacturing quality escape" and my faith in humanity's ability to convolute anything is restored.
Click to expand...

Agree! And I plan to put "manufacturing quality escape" to good use this morning at my staff meeting as one of my vendors just let some quality escape!
 
iamtheari said:
Does the AD require an IA to check the crankshaft serial number list in the AD
Click to expand...
Anybody can read and research an AD. Its actually an owners responsibility to do so. However the AD states before flight so you'!l need a mechanic to sign it off before you go fly.
Hang 4 said:
Actually a PP could sign off that AD on their own plane
Click to expand...
No. Only if the AD applicability statement allows a pilot to sign it off is it permitted. Short of that you need a mechanic to sign it. I believe the fuel valve placard AD stated this.
 
Steamflyer said:
Agree! And I plan to put "manufacturing quality escape" to good use this morning at my staff meeting as one of my vendors just let some quality escape!
Click to expand...

Actually, quality escape is a well established phrase in manufacturing. Sorry, it is not a new one invented by the CMI legal team.

Tim
 
http://www.tcmlink.com/pdf2/MSB23-01.pdf Listed a 5 hour grace period for ferry flights and 200 hour TIS upper limit of effectivity.

https://drs.faa.gov/browse/excelExternalWindow/FR-ADFRAWD-2023-03796-0000000000.0001 AD 2023-04-08 eliminates both - no more grace period for ferry (ferry flight required) i.e. "Prior to Further Flight" restriction and no more upper limit on TIS; AD seems to apply to ALL Continental engines built since June 2021.

First 2 inspections we did on brand new engines in our shop: 1 was completely OK, other had 1 snap ring clip not seated properly, but hadn't come loose. We were able to seat it properly.
 
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150Mike said:
had 1 snap rign clip not seated properly, but hadn't come loose. We were able to seat it properly.
Click to expand...
Did you have to flip the retaining ring, or did you tap it into place?

Do you think you could snake a borescope in to see the rings before cylinder removal? Or if the engine requires 2 or 3 cylinders off, do you think a borescope could see the other rings with only one cylinder off?
 
Hang 4 said:
Actually a PP could sign off that AD on their own plane. I was a student at the time, owned a plane that was affected by the AD and had to get an AP to sign it off. What I found absurd was that getting my PP would magically make me qualified to say the stickers on my fuel valve looked like the correct picture. The letter L and the letter R were in the right place.
Click to expand...
I recall that there was a period of time when that AD was issued before the AMOC of the pilot-owner looking at the placard was allowed. I owned a PA-28 at the time and recall it being a pain in the butt.

Bell206 said:
Anybody can read and research an AD. Its actually an owners responsibility to do so. However the AD states before flight so you'!l need a mechanic to sign it off before you go fly.
Click to expand...
The real question I have is whether I need a mechanic to sign off "AD N/A this serial number." Does the mechanic have to be an IA? Do I need a ferry permit to bring my obviously-not-affected aircraft to a mechanic to confirm that Serial Number A produced a decade ago is absent from List B of items produced in the past couple of years? Emergency ADs like this are frustrating because they force airplane owners to do legal research, which disproportionately affects the airplane owners who are responsible enough to ask questions and research the answers.
 
The AD says you have to perform the inspection if you have one of the affected engines (ones with the crankshaft serial numbers listed in the SB). There's no obligation to do anything if it isn't one of those, though it is handy to note that you've determined the AD doesn't apply to you.
 
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