Maybe dumb engine start question

[ArtVandelay]

but is'nt that why we are told to fly our planes alot so we burn off all the moisture in the oil?

And more importantly, will keep the engine well lubricated, coated in oil.

[Ragsf15e]

52 minutes ago, PT20J said:

Physicist Richard Feynman described the scientific method as a two step process: Guess at a solution and then prove or disprove it by experiment. The problem with all these supposed causes of cam problems that we hear and read about is that they are just guesses that have never been validated. After they get repeated long enough they become "Old Wives Tales" -- a term I believe was first applied to aviation beliefs by Randy Sohn and popularized by John Deakin. I'm not pointing any fingers: I have believed a lot of things over the years that have turned out not to be true, and I probably still believe things that aren't true.

While I have no firsthand knowledge, I believe it reasonable to assume that Lycoming knows more about its engines than anyone outside the company. Besides seeing engines that come back for overhaul and rebuild, Lycoming has all the design and test data and a failure analysis lab. The fact that Lycoming changed the lifter design tells me that they knew something needed fixing. The change to roller tappets required redesigning the case haves to accept them as well as the tappets themselves and probably a ton of testing. Changes like this are very expensive and not undertaken without good reason.

Skip

This from an ex-secretary of Defense could help us with our cam corrosion problems, “… there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones.” Donald Rumsfeld.

[PT20J]

1 hour ago, Ragsf15e said:

This from an ex-secretary of Defense could help us with our cam corrosion problems, “… there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones.” Donald Rumsfeld.

Well, I don’t know….

[Shadrach]

3 hours ago, PT20J said:

Physicist Richard Feynman described the scientific method as a two step process: Guess at a solution and then prove or disprove it by experiment. The problem with all these supposed causes of cam problems that we hear and read about is that they are just guesses that have never been validated. After they get repeated long enough they become "Old Wives Tales" -- a term I believe was first applied to aviation beliefs by Randy Sohn and popularized by John Deakin. I'm not pointing any fingers: I have believed a lot of things over the years that have turned out not to be true, and I probably still believe things that aren't true.

While I have no firsthand knowledge, I believe it reasonable to assume that Lycoming knows more about its engines than anyone outside the company. Besides seeing engines that come back for overhaul and rebuild, Lycoming has all the design and test data and a failure analysis lab. The fact that Lycoming changed the lifter design tells me that they knew something needed fixing. The change to roller tappets required redesigning the case haves to accept them as well as the tappets themselves and probably a ton of testing. Changes like this are very expensive and not undertaken without good reason.

Skip

I agree,  but the fact that it took 50 years to make such a change in the design is suspect. You’ve been at this longer than me. Did Lycomings have a reputation for cam problems when you started flying?  Seems to me if they had been spalling cams since the 50s they’d have not been very successful.  I personally know of two factory new engines that ate cams in less than 4 years and 500hrs but that was in the early to mid 00s.

[PT20J]

36 minutes ago, Shadrach said:

I agree,  but the fact that it took 50 years to make such a change in the design is suspect. You’ve been at this longer than me. Did Lycomings have a reputation for cam problems when you started flying?  Seems to me if they had been spalling cams since the 50s they’d have not been very successful.  I personally know of two factory new engines that ate cams in less than 4 years and 500hrs but that was in the early to mid 00s.

Good questions Ross. I don't recall being all that concerned about it when I had my first '78 J back in the late '80s. Back then, everyone was starting to worry about shock cooling. I'll bet Lycoming has been through a number of changes in 50 years. Did they make their own camshafts in house? Did they use outside vendors? Did they switch back an forth as the market boomed and collapsed? Did vendors change? Did the specs change? Even if there is a solid specification, manufacturing processes can have a lot of variation if vendors change. Some process things are art. There is just so much we don't know. What we do know is that you have a golden cam and I have roller lifters and we are probably both in good shape. 

Cheers,

Skip

[carusoam]

Well Mr. Rumsfeld…

What we know…

Lycoming knows a lot…

Lycoming doesn’t always tell us when they have dropped the ball…. Neither did Gill or Champion….

There we’re certain years where the cam materials were not as good as the years before or after…

 

The poor cam gets a lot of the blame… yet the cam followers often look like cutting tools when the cam lobes are getting machined off….

 

Word of advice from this month’s newsletter… from the home drome… start and run the engine on low rpms… until the oil pressure comes up…

After the oil pressure comes up, splash lubrication occurs at and above 1k rpm…

 

Apparently, there have been a few engines sitting for a long time… that get started at higher than ideal rpm…

Dry cam and follower surfaces can heat really quickly… it is easy to destroy poorly lubricated rubbing metal parts…

 

So….   Back to Joe’s point…

No…it’s not the act of starting the engine that puts bad stuff in the oil… generally. 

Short runs aren’t going to be noticed amongst all the other cruising that gets done…

If it is only short ground runs for a year… there is a lot of moisture condensing inside the engine…

If the oil has dozens of hours on it… it accumulates the acids and other junk from the extra hours…

 

Fear the dry starts, lack of cruising, and nothing but ground running…

Also fear that some large corporations haven’t always had our best interests… they are getting remarkably better… with two way conversations.

+1 for letting the steam out if you can… know that smoky vapor can also have oil coming out….  Longer the cruise, the more water vapor has been generated… the fewer gallons are left in the tanks…

 

Now back to the usual program…. Fly often, change oil regularly, pray for good weather….

Best regards,

-a-

[Yetti]

1 hour ago, PT20J said:

Good questions Ross. I don't recall being all that concerned about it when I had my first '78 J back in the late '80s. Back then, everyone was starting to worry about shock cooling. I'll bet Lycoming has been through a number of changes in 50 years. Did they make their own camshafts in house? Did they use outside vendors? Did they switch back an forth as the market boomed and collapsed? Did vendors change? Did the specs change? Even if there is a solid specification, manufacturing processes can have a lot of variation if vendors change. Some process things are art. There is just so much we don't know. What we do know is that you have a golden cam and I have roller lifters and we are probably both in good shape. 

Cheers,

Skip

something happened along the 1990s to the 2000s to the cam and lifters....   Some EPA reg was followed or someone retired and then a bad batch came along and caused some spensive failures.

[igorbly]

On 1/2/2022 at 10:38 AM, PT20J said:

I am aware that this is one of the things that many people believe. Here are some things to think about:

1. The hydraulic lifters are supplied with pressurized oil which provides a source of lubrication to the lifter bores and the camshaft during operation.

2. Many IC engines utilize overhead cams without issues.

3. After an engine has been sitting for a time, oil will drain off all internal parts without regard to their position within the crankcase.

4. Flight school engines are started frequently and often reach TBO and beyond, so lack of lubrication at start up doesn't seem to be a problem.

5. Spalling is caused by metal fatigue. 

6. Corrosion is not always simply a chemical reaction -- it can have mechanical causes (called frictional or fretting corrosion).

7. Someone on MS posted a picture of a camshaft that had been sitting around in a hangar for years and looked almost new.

I didn't design the thing and I'm an electrical engineer, not a mechanical engineer. But, I would bet that the lifter faces have operating pressures near the limit for the hardness of the material and some just fail. Based on flight school experience, it seems frequent operation is beneficial. Everything else has likely a second or third order effect with only anecdotal evidence to suggest it has any effect at all. 

Skip

 

We were disappointed to find out last month our lifters were spalling. Although the plane had periods of low activity prior to us purchasing it 16 months ago, we flew it regularly and often last year. It was only the last oil change that had some metal flakes that gave us a heads-up this might be coming. I thought that if it made it a year, we would likely be past discovering effects of previous low usage, but it seems not.

[RobertGary1]

On 1/2/2022 at 8:26 AM, skydvrboy said:

After a short run to the fuel pumps, use the hot start procedure.  That always works in my plane, but if it doesn't, you can then go to the cold start procedure.  If you try the cold start procedure first and it doesn't work, you've flooded it and now must use the flooded start procedure.  It still works, but in my opinion the flooded start procedure is the most awkward and challenging.

I think this is mainly a problem in the long bodies.  My F had shock discs from 3/77 that I replaced recently and they still met airworthy specs.  I have no idea how the tanks were filled during those 40 years, but I'm guessing you won't get 40 years out of your discs in a long body regardless of how much fuel you store.

Having had an F for more than 20 years I can’t imagine filing it regularly. Like pulling a boat around all day behind a sports car. An F with full fuel is a dog and how often do you need 6 hour legs? If keeping the tanks topped off were a requirement I’d sell my F. 

[KB4]

On 1/1/2022 at 6:07 PM, Joe Larussa said:

I have bladders so I like to keep it full

Not sure with bladders, but without them, since you are in a hanger. I would not keep full, at most up to 25 mark.  Your Disks will thank me, and no corrosion issues.  Filling up before each flight even better assuming you have at least 10 in each.  Not saying run nearly dry then wait til next flight to fill. 
 

I thought they were kinda pricey at 90$.  Now they are 140$ 
Run a dehumidifier in the hanger too. In summer in pulls gallon of water out of the air each day.  

[DCarlton]

3 hours ago, RobertGary1 said:

Having had an F for more than 20 years I can’t imagine filing it regularly. Like pulling a boat around all day behind a sports car. An F with full fuel is a dog and how often do you need 6 hour legs? If keeping the tanks topped off were a requirement I’d sell my F. 

A bit of a tangent but were't we all initially trained to completely fill our tanks to avoid condensation and the potential for water in the fuel tanks?  Isn't that the root cause of the fill your tank logic?  I stopped doing it years ago and agree I rarely top my F.  Never thought of it as a dog full though but it sure flies nice on a cool day with half full tanks.  :> 

[jaylw314]

I stopped filling up all the way, because pulling the plane out of the hangar by hand, the 100 lbs difference feels like the difference between giving myself a muscle strain vs giving myself a hernia.

[Shadrach]

On 1/1/2022 at 8:59 PM, PT20J said:

except for highly theoretical conjecture unsupported by any actual data. 

If we eliminate data free, theoretical conjecture from mooneyspace Javier could save a lot on server space.

[McMooney]

always keep birdy topped off, like worrying about gas when i get back rather than prior to flight

[AH-1 Cobra Pilot]

I have seen car engines that are run short times in cold weather.  You will likely find a pasty build up of hydrogenated oil on the oil cap.  It is tan colored and the consistency of butter.  Unless you are seeing that, you probably do not have much of a problem with water condensation in your oil.

Do not necessarily presume engine companies employ the pinnacle of experts on engines.  A friend uses B&S engines to pump oil wells and has routinely had engines running 15-20 times as long as the B&S people thought possible.  Most people simply fall into accepting the prevailing knowledge, and very few actually experiment with new possibilities.

[EricJ]

2 hours ago, Shadrach said:

If we eliminate data free, theoretical conjecture from mooneyspace Javier could save a lot on server space.

This is true of the internet in general, or pretty much any media, actually... 

[Hank]

2 hours ago, Shadrach said:

If we eliminate data free, theoretical conjecture from mooneyspace Javier could save a lot on server space.

 

14 minutes ago, EricJ said:

This is true of the internet in general, or pretty much any media, actually... 

Yep, seems to be how most aviation reporting is done by major media, and how USA Today reports everything . . .

[RLCarter]

I believe for every 8 gallons of fuel burned an engine will produce 1 gallon of water as one of its byproducts. An engine that is allowed to get up to normal operating temperatures will burn off the moisture….

Lycoming changed something, my guess was to meet some EPA standards and it just didn’t work as well as the old way…

I fuel up once I figure how much I can add, full seats makes for short hops…

[carusoam]

Keeping the tanks filled solves a few challenges…

1) Empty tanks exchange air with the outside as the temperature and pressure changes over time….

2) Air entering the tanks, including when you burn off fuel…. Contains some moisture…

3) In cold temps, that moisture can fall out of solution and deposit itself in the tank… RH and saturation…

 

4) The other thing it is really good at… full tanks don’t get overheated like empty tanks can… leaving a plane outside in the sun… the temperature of the wing skins can get extremely hot….  This heat is tough on the sealant….

 

5) An OWT… tank sealant needs to be kept wet, or it dries out….   This would imply that the sealant actually absorbs some fuel….  If it did, the sealant would swell and cause other challenges… expect that our sealant doesn’t have a benefit of staying wetted…

Another point of proof… tank sealant is used to seal other things like windows… fuel doesn’t get used on windows, and they stay sealed…

 

Leaving tanks near empty… Or whatever status they are in after flying…

6) Fuel weighs a lot… extra weight on the donuts is known to compress them… rubber slowly creeeeps… flowing away from the pressure…. And doesn’t creep back when the weight is removed…

7) The tanks are always full… the day you have four people going flying…

With near empty tanks… you can fill them to fit the next flight’s requirements…

 

8) As a member of the CB club… I use the self serve pumps often… it doesn’t matter much if I fill before or after the flight… there is a small time hassle with either…

9) If your plane is parked out in the sun… filling the tanks is good protection for the sealant around the inspection panels on the wing top…

 

PP thoughts only…

-a-

[jaylw314]

Another argument for filling tanks is that with alternating day and night temps, air "breathes" in and out of the fuel vents, drawing in more moisture.  The more air in the tank, the more air is exchanged each day cycle.  Obviously, this one makes the most difference for planes parked outside

[A64Pilot]

On 1/2/2022 at 9:45 PM, Yetti said:

something happened along the 1990s to the 2000s to the cam and lifters....   Some EPA reg was followed or someone retired and then a bad batch came along and caused some spensive failures.

I tend to agree, it used to not be a problem, but since then fuel has changed, and I believe Crane Cams was Lycoming’s supplier, and did they go under?

I am not sure Crane made their cams, so maybe, maybe not.

So far as dry starts, pre-lubers we’re in fashion in the 70’s, were supposed to greatly extend the lives of many engines that accumulated a lot of use like OTR trucks etc.

But unfortunately they didn’t, one can only assume “dry” starts aren’t as harmful as many say.

I think calendar time is more harmful than we realize

[PT20J]

7 hours ago, A64Pilot said:

I think calendar time is more harmful than we realize

People like to call their 25 year-old 1000 hour engine “low time.” Everyone knows the hour TBO but we seem to forget that Lycoming has a 12 year TBO limit also. Sure, Part 91 operators are free to ignore it, but I think Lycoming is making a point: Don’t expect TBO hours if it sits a lot.

[RobertGary1]

2 hours ago, PT20J said:

People like to call their 25 year-old 1000 hour engine “low time.” Everyone knows the hour TBO but we seem to forget that Lycoming has a 12 year TBO limit also. Sure, Part 91 operators are free to ignore it, but I think Lycoming is making a point: Don’t expect TBO hours if it sits a lot.

I think it has a lot to do with where it sits. Arizona is different from Georgia. 

[PeteMc]

On 1/2/2022 at 9:56 AM, StevenL757 said:

I disagree...unless you want to pay for installation of new shock discs every year or so.

Meant to reply to this earlier and got sidetracked...

I actually disagree with your premise.  In the 30 years I've owned my (41 year old) K I have not excessively changed my donuts.  I'm thinking I've changed them once, but the logs  are at the mechanics for the Annual right now.  I've read lots of post from various people and there are as many that say they keep their donuts a long time as there are people that say they have to change them. 

I do think there is more of an issue if you live somewhere that it is really hot.  And I also think a lot has to do with how you land.  I have a friend that makes excellent landings in his Mooney and is extremely consistent.  But he was taught in his primary training to PLANT the plane.  I tend to let the plane stop flying (pending winds, etc.), so I think that may play into it as well.

[ArtVandelay]

I think it has a lot to do with where it sits. Arizona is different from Georgia. 

Doesn’t matter where it sits, dirty oil contains bad things including water. What matters is how the engine was treated. If you check the logs and only see oil changes during the annual, that’s a bad sign.