Maintenance question for engine over TBO
Joined: Jan 1999
Posts: 6,209
Likes: 2
From: north of barlu
Silvaire 1
Thats all very well but few of us have a hone that can work a Lycoming Cylinder or a set of valve seat cutters or an oven that can get the cylinder hot enough to get the valve seats out or the kit to measure the cylinder bore well enough to tell if it's worth reworking in the first place.
Joined: Jan 1999
Posts: 6,209
Likes: 2
From: north of barlu
Yes, it is all on the web !
I very much doubt that the $143 that I calculated from that price list will get you a cylinder that will last more that 150 hours, just fine if you want to sell the aircraft but no good if you are hanging your life on the thing over the Irish sea.
No just how much would Barrett or one of the other quality overhaul companys charge for a cylinder overhaul?
I very much doubt that the $143 that I calculated from that price list will get you a cylinder that will last more that 150 hours, just fine if you want to sell the aircraft but no good if you are hanging your life on the thing over the Irish sea.
No just how much would Barrett or one of the other quality overhaul companys charge for a cylinder overhaul?
Joined: Jan 1999
Posts: 6,209
Likes: 2
From: north of barlu
It's not about making anything a big deal, it is about what you get for your money, you may get lucky and get a good $300 cylinder overhaul but there is a reason that a $300 job costs $300 and that is the depth and care to which the inspection is done.
Early in my time in this busness I used cheap overhauled cylinders and the these cylinders usualy failed within 3-400 hours one at 50 hours. The overhaul shop that I use for cylinders are charging about $500 for a cylinder overhaul and you can expect one of these cylinders to last as well as a new cylinder.
The message is that you only get what you pay for.
Early in my time in this busness I used cheap overhauled cylinders and the these cylinders usualy failed within 3-400 hours one at 50 hours. The overhaul shop that I use for cylinders are charging about $500 for a cylinder overhaul and you can expect one of these cylinders to last as well as a new cylinder.
The message is that you only get what you pay for.
Joined: Jun 2003
Posts: 13,787
Likes: 0
From: EuroGA.org
Barrett did my engine in 2008 (SB569A). They did a superb job. Original cylinders were left on; rehoned. Last week the compressions were all 79/80, with one being 78/80. Can't get better than that.
My recollection is that on an overhaul they always use brand new Lyco cylinders, never repair old ones.
I am now at 1000hrs. When I get to OH I will send the motor to them to do, by DHL both ways (£3000 at today's prices) and it will be worth every penny, IMHO
My recollection is that on an overhaul they always use brand new Lyco cylinders, never repair old ones.
I am now at 1000hrs. When I get to OH I will send the motor to them to do, by DHL both ways (£3000 at today's prices) and it will be worth every penny, IMHO
Joined: Feb 2000
Posts: 731
Likes: 0
From: Pacific
Consider a a company working with FARs in the US. The company uses the airplane for commercial use but does not carry passengers. The Chief Mechanic states that Continental engines no longer use the term "recommended" when discussing TBO, but instead state that the TBO is a limit.
I agree with the need to overhaul the engine at TBO, but there is a lot of commercial pressure to go past TBO as "on condition".
Is the Chief Mechanic right? Is there an FAR that refers?
I agree with the need to overhaul the engine at TBO, but there is a lot of commercial pressure to go past TBO as "on condition".
Is the Chief Mechanic right? Is there an FAR that refers?
Fleet Manager
Joined: Aug 2006
Aviation Qualifications: CPL
Posts: 7,090
Likes: 2,952
From: Ontario, Canada
Limits
Do not take to following as "the gospel", but rather food for thought;
An engine manufacturer will state "limits" for an engine. They could be the maximum allowable diameter of a bore for something, etc. That limit, in and of itself, may not truly be an "airworthiness limitation".
Airworthiness limitations must be followed absolutely for the certified product to remain "airworthy". These limitations will always be stated right on the Type Certificate for the product. A pretty common example would be the "life limts" common to some helicopter parts. There is no option to go beyond the stated limitation (hours or cycles), and still declare the pruduct as "airworthy". To be "airworthy", it must conform to the limitations and conditions stated on the Type Certificate. So, if an engine TBO is stated on the Type Certificate as being limited in hours - that's that, no going over, without specific approval.
From here on, it gets a little more grey...
The Type Certificate will refer (sometimes rather indirectly) to maintenance and parts manuals. Those manuals may contain "limits". Unless those limits are also stated on the Type Certificate, they don't have quite the same absolutness (if that's a word). In theory, the mechanic should certifiy that everything is "within limits" for it to continue to be airworthy. However, some of the things you could measure, can only be accessed with an inspection much more in depth than the required interval inspections. The interval inspections are designed to "red flag" things going wrong. No red flag, don't inspect any further.
Those manuals have authority akin to a Service Bulletin. My experience has been that SB's are optional for private aircraft, and mandatory for commercial aircraft.
When I STC'd some replacement piston engine parts many years ago, I had a "life limit" in mind. To assure it was followed without option, I made it an airworthiness limitation of the STC. Adherance was mandatory. I am aware that one U.S. A&P was "cited" for not following it. It was there for a good reason, based upon test data, and vast experience. Otherwise, were it not an airworthiness limitation, and just a limit, it might not have been followed.
I hope that helps a bit. To get a valid, local interpretation, you'll have to seek local authority advice...
An engine manufacturer will state "limits" for an engine. They could be the maximum allowable diameter of a bore for something, etc. That limit, in and of itself, may not truly be an "airworthiness limitation".
Airworthiness limitations must be followed absolutely for the certified product to remain "airworthy". These limitations will always be stated right on the Type Certificate for the product. A pretty common example would be the "life limts" common to some helicopter parts. There is no option to go beyond the stated limitation (hours or cycles), and still declare the pruduct as "airworthy". To be "airworthy", it must conform to the limitations and conditions stated on the Type Certificate. So, if an engine TBO is stated on the Type Certificate as being limited in hours - that's that, no going over, without specific approval.
From here on, it gets a little more grey...
The Type Certificate will refer (sometimes rather indirectly) to maintenance and parts manuals. Those manuals may contain "limits". Unless those limits are also stated on the Type Certificate, they don't have quite the same absolutness (if that's a word). In theory, the mechanic should certifiy that everything is "within limits" for it to continue to be airworthy. However, some of the things you could measure, can only be accessed with an inspection much more in depth than the required interval inspections. The interval inspections are designed to "red flag" things going wrong. No red flag, don't inspect any further.
Those manuals have authority akin to a Service Bulletin. My experience has been that SB's are optional for private aircraft, and mandatory for commercial aircraft.
When I STC'd some replacement piston engine parts many years ago, I had a "life limit" in mind. To assure it was followed without option, I made it an airworthiness limitation of the STC. Adherance was mandatory. I am aware that one U.S. A&P was "cited" for not following it. It was there for a good reason, based upon test data, and vast experience. Otherwise, were it not an airworthiness limitation, and just a limit, it might not have been followed.
I hope that helps a bit. To get a valid, local interpretation, you'll have to seek local authority advice...
Joined: Sep 2006
Posts: 1,631
Likes: 0
From: Los Angeles, USA
If recommended becomes hard limits, there will be no more air shows with vintage aircraft, no more movies with period aircraft and no more historic fly-ins. Many of these aircraft run orphaned or discontinued engines that can not be overhauled to spec even if you wanted to.
My aircraft runs Lycoming GO-435's. All the geared GO, GSO and IGSO (and there are plenty of those around) are unsupported by Lycoming and have been for decades. I think it's the same with the Continental geared ones.
The gearbox parts are no longer available and the factory supply was bought by one company who charges an arm and a leg for them. Last quote I got from this firm was $40,000 per engine, which is madness. If you take away the gearbox, it's just a normal O-435 that costs about $20,000 to overhaul, but they can charge whatever they want for that gearbox overhaul cause they're sitting on the parts. And when these parts dry up, there is no longer a possibility to overhaul to factory specs. Thankfully, most things can be overhauled and as an owner you are allowed to manufacture your own replacement parts for part 91 ops, so this can be sidestepped. The reality is this is how all these Helio Couriers, Stinsons, Aero Commanders, Republic Sea Bee's, Bell 47's keep flying. Sure, some of them get sent off for complete overhauls by deep pocketed owners where such an option exists, but most get patched, repaired and tweaked to run for years. Many, many engines can not be sent off to anyone, especially the older rotary ones.
Tons of other aircraft would be grounded if TBO was a hard limit. Alvis Leonides? Gipsy Majors? Wright Cyclones? P&W radials? Franklin's? Rolls Royce Merlins? Gnome's? Blackburns? It would all come to a screeching halt eventually, so although it might make sense in a bureaucrats eye and under the guise of "safety", be careful what you wish for.
My aircraft runs Lycoming GO-435's. All the geared GO, GSO and IGSO (and there are plenty of those around) are unsupported by Lycoming and have been for decades. I think it's the same with the Continental geared ones.
The gearbox parts are no longer available and the factory supply was bought by one company who charges an arm and a leg for them. Last quote I got from this firm was $40,000 per engine, which is madness. If you take away the gearbox, it's just a normal O-435 that costs about $20,000 to overhaul, but they can charge whatever they want for that gearbox overhaul cause they're sitting on the parts. And when these parts dry up, there is no longer a possibility to overhaul to factory specs. Thankfully, most things can be overhauled and as an owner you are allowed to manufacture your own replacement parts for part 91 ops, so this can be sidestepped. The reality is this is how all these Helio Couriers, Stinsons, Aero Commanders, Republic Sea Bee's, Bell 47's keep flying. Sure, some of them get sent off for complete overhauls by deep pocketed owners where such an option exists, but most get patched, repaired and tweaked to run for years. Many, many engines can not be sent off to anyone, especially the older rotary ones.
Tons of other aircraft would be grounded if TBO was a hard limit. Alvis Leonides? Gipsy Majors? Wright Cyclones? P&W radials? Franklin's? Rolls Royce Merlins? Gnome's? Blackburns? It would all come to a screeching halt eventually, so although it might make sense in a bureaucrats eye and under the guise of "safety", be careful what you wish for.
Last edited by AdamFrisch; 1st May 2011 at 22:56.
Joined: Feb 2006
Aviation Qualifications: LAME
Posts: 36,145
Likes: 5,739
From: Falling off the end of the thread
Maintenance question for engine over TBO
Can anyone point us in the right direction?
I am part of a syndicate which runs a C172P on a UK private C of A. The engine (O-360) is over Lycoming's recommended TBO (now with about 2,300 hours on it) and we are operating it "on-condition". We have run this aircraft for over 20 years and it is very well maintained and used very regularly. We regularly run engines to over 2,500 before overhaul (we are on engine number 3 so far), as long as the certified engineer (and we pilots!) are happy that it is safe and legal to do so.
Here is the question: we have identified low compression on one cylinder (still within limits), and the engineer says it is a very simple fix as the valve probably needs re-seating. However, he also says that as it is "on-condition", he is not allowed to remove the cylinder head, but that the whole engine must be overhauled. If that is true, fair enough, but I like to see these things in writing. I've looked through LAMS/CAP411 and cannot see the reference. I don't have the C172 log-books to hand to see if it is referred to in the specific maintenance schedule for the type. Can anyone point me to where it says no part-disassembly of the engine once over recommended TBO?
Thanks in advance!
Can anyone point us in the right direction?
I am part of a syndicate which runs a C172P on a UK private C of A. The engine (O-360) is over Lycoming's recommended TBO (now with about 2,300 hours on it) and we are operating it "on-condition". We have run this aircraft for over 20 years and it is very well maintained and used very regularly. We regularly run engines to over 2,500 before overhaul (we are on engine number 3 so far), as long as the certified engineer (and we pilots!) are happy that it is safe and legal to do so.
Here is the question: we have identified low compression on one cylinder (still within limits), and the engineer says it is a very simple fix as the valve probably needs re-seating. However, he also says that as it is "on-condition", he is not allowed to remove the cylinder head, but that the whole engine must be overhauled. If that is true, fair enough, but I like to see these things in writing. I've looked through LAMS/CAP411 and cannot see the reference. I don't have the C172 log-books to hand to see if it is referred to in the specific maintenance schedule for the type. Can anyone point me to where it says no part-disassembly of the engine once over recommended TBO?
Thanks in advance!
GRN 24 covers it and you can pull cylinders...
Joined: Sep 2001
Aviation Qualifications: CPL
Posts: 2,787
Likes: 208
From: Toronto
Joined: Apr 2008
Posts: 555
Likes: 0
From: Cilboldentune, Britannia
All very well but look at it from the MO side, you have a TBO which is only a 'recommendation' and you decide that the compressions are good, no metal in the filters. What do you do? If say in the next few hours the engine blows up and causes an incident, how do you think you would feel? MOs are kind of forced into suggesting overhaul to be on the safe side as no one can predict the life of an engine and have to keep legal.
Joined: Jan 1999
Posts: 6,209
Likes: 2
From: north of barlu
Quote:-An "overhaul" does not mean returning the engine to new manufacturing tolerances, it means (at a minimum) disassembling the engine, verifying that it is within allowable *operational* wear condition and tolerances, and putting it back together. Therefore is is possible to legally overhaul an engine without all the parts required to return it to as-new tolerances.
I have to take issue with this statment, if an item is stripped and parts are found to be within the service limits then it has been repaired.
If an item is stripped and all the parts are returned to new limits then it has been overhauled.
The repaired part can continue to be used for the remander of it's service life, the overhauled part starts a new service life at zero hours.
I have to take issue with this statment, if an item is stripped and parts are found to be within the service limits then it has been repaired.
If an item is stripped and all the parts are returned to new limits then it has been overhauled.
The repaired part can continue to be used for the remander of it's service life, the overhauled part starts a new service life at zero hours.
Joined: Feb 2000
Posts: 731
Likes: 0
From: Pacific
The old TCM bulletin had this:
Thousands of hours of operating experience indicate that Teledyne Continental Motors (TCM) aircraft engines, when operated within prescribed limitations, instructions and recommendations, can be operated between overhauls for the number of hours listed in the following table. The overhaul periods listed are recommendations only. They are predicated on the use of genuine TCM parts, compliance with all applicable Service Bulletins and ADs, as well as all required preventive maintenance, periodic inspections, manufacturer's specifications, and the determination by a qualified mechanic that the engine is operating normally and is airworthy. The accomplishment of cylinder leakage checks and spectrographic oil analysis may be helpful in making this determination. Any operation beyond these periods is at the operator's discretion and should be based on the inspecting mechanic's evaluation of engine condition and operating environment. Calendar time also affects this condition and should be taken into account.
The latest copy does not have the statement "The overhaul periods listed are recommendations only". http://www.proaeroengines.com/docs/FCD65C1569DBB26D.pdf
I also cannot find any reference to commercial or private use of the engines. I think it might be hard in a court of law to prove to a judge that it is OK to fly an engine over TBO because it was for private use, particularly if someone had been killed or hurt due to an engine problem.
I have not checked, but I was told Lycoming still has a statement that TBO is a recommendation only, so maybe that type of engine can still be run past TBO.
I personally run a Lycoming in an experimental airplane, it has 500 hours since TBO in 1981 so it is overdue on calendar but since it is in an experimental airplane I don't have to comply with the TBO rules. It is also not insured! I try to avoid any congested areas and fly only over places I can set down without any collateral damage. It has wheels and floats so I have some choices in that regard, but it does worry me a little. In the US litigation can make one a pauper and I would hate to leave my family destitute just because I like to fly.
Thousands of hours of operating experience indicate that Teledyne Continental Motors (TCM) aircraft engines, when operated within prescribed limitations, instructions and recommendations, can be operated between overhauls for the number of hours listed in the following table. The overhaul periods listed are recommendations only. They are predicated on the use of genuine TCM parts, compliance with all applicable Service Bulletins and ADs, as well as all required preventive maintenance, periodic inspections, manufacturer's specifications, and the determination by a qualified mechanic that the engine is operating normally and is airworthy. The accomplishment of cylinder leakage checks and spectrographic oil analysis may be helpful in making this determination. Any operation beyond these periods is at the operator's discretion and should be based on the inspecting mechanic's evaluation of engine condition and operating environment. Calendar time also affects this condition and should be taken into account.
The latest copy does not have the statement "The overhaul periods listed are recommendations only". http://www.proaeroengines.com/docs/FCD65C1569DBB26D.pdf
I also cannot find any reference to commercial or private use of the engines. I think it might be hard in a court of law to prove to a judge that it is OK to fly an engine over TBO because it was for private use, particularly if someone had been killed or hurt due to an engine problem.
I have not checked, but I was told Lycoming still has a statement that TBO is a recommendation only, so maybe that type of engine can still be run past TBO.
I personally run a Lycoming in an experimental airplane, it has 500 hours since TBO in 1981 so it is overdue on calendar but since it is in an experimental airplane I don't have to comply with the TBO rules. It is also not insured! I try to avoid any congested areas and fly only over places I can set down without any collateral damage. It has wheels and floats so I have some choices in that regard, but it does worry me a little. In the US litigation can make one a pauper and I would hate to leave my family destitute just because I like to fly.
Joined: Sep 2006
Posts: 1,631
Likes: 0
From: Los Angeles, USA
The danger in the future, and especially in Europe, is that what might be a SB in FAA-land tends to become something mandatory in EASA-land.
A very good case in point is the Cessna 337 Skymaster that has a looming SID (Supplemental Inspection Documents) on it's wings. It requires the owner to do a tear down of the whole wing and do a one off inspection, Eddy current, dye penetrant, x-ray, the works to prove that it's safe. This will most likely run about $60K, well above what many 337's are worth. Now, in a part 91 operation, or private use if you wish, this is optional. In Europe, they have said that any SID that comes into effect will have to be complied with - they don't make an extinction between commercial and private use. This has the effect of, overnight, making any 337 worthless that's on the European register.
But what's more worrying is that these SID's are instigated by Cessna, they don't stem from an AD or the FAA. It's because Cessna wants to sell new airplanes - as simple as that. They're sick of people flying around in 40 year old aircraft that don't break down enough for the bean counters so they invent this inspection scheme. And you can be as sure as the sun shines that they have future SID's in place for all their aircraft and will roll them out in time to gradually force new sales, obviously starting with the least supported or loved models, i.e. Skymasters. It makes perfect business sense.
Ultimately, the problem with this (once again) is that in the US what's optional for a private owner, will in Europe be mandatory. This has potential catastrophic results unless EASA in the future will grant exceptions or make a distinction between private use and commercial. Taken to it's logical conclusion, and if all manufacturers follow Cessna's SID lead, they could make it so cost prohibitive that all GA flying in C of A aircraft in Europe could be threatened. I doubt that will happen, but it's a possibility.
A very good case in point is the Cessna 337 Skymaster that has a looming SID (Supplemental Inspection Documents) on it's wings. It requires the owner to do a tear down of the whole wing and do a one off inspection, Eddy current, dye penetrant, x-ray, the works to prove that it's safe. This will most likely run about $60K, well above what many 337's are worth. Now, in a part 91 operation, or private use if you wish, this is optional. In Europe, they have said that any SID that comes into effect will have to be complied with - they don't make an extinction between commercial and private use. This has the effect of, overnight, making any 337 worthless that's on the European register.
But what's more worrying is that these SID's are instigated by Cessna, they don't stem from an AD or the FAA. It's because Cessna wants to sell new airplanes - as simple as that. They're sick of people flying around in 40 year old aircraft that don't break down enough for the bean counters so they invent this inspection scheme. And you can be as sure as the sun shines that they have future SID's in place for all their aircraft and will roll them out in time to gradually force new sales, obviously starting with the least supported or loved models, i.e. Skymasters. It makes perfect business sense.
Ultimately, the problem with this (once again) is that in the US what's optional for a private owner, will in Europe be mandatory. This has potential catastrophic results unless EASA in the future will grant exceptions or make a distinction between private use and commercial. Taken to it's logical conclusion, and if all manufacturers follow Cessna's SID lead, they could make it so cost prohibitive that all GA flying in C of A aircraft in Europe could be threatened. I doubt that will happen, but it's a possibility.
