tbo-regulatory? recommendation? grace period?

[avbug]

Gravityhater you need to expand on that. You presented two different topics (unrelated) which need more info. I'm interested.

Annuals and 100 hours keep track of #1, but the risk of #2 increases gradually with engine life. It exists for a brand new engine, but the risk is lower than a high-time unit. TBO is an arbitrary number where somebody decided that statistically speaking the risk level had reached a certain point.

TBO isn't about risk, or about managing the risk of a catastrauphic failure.

An overhaul can re-use all the same parts, so long as the aircraft has been determined to be within manufacturer tolerances. Generally certain components get refurbished or replaced, but they need not be. Therefore, if it were really about engine components at risk of failure, those parts would be required to be replaced. They're not.

TBO is a manufacturer recommendation, often formed and changed based on thousands upon thousands of hours of real-world data, which establishes a mean time between overhauls. This serves to establish a generic goal and planning meter by which to gauge costs, establish maintenance intervals and inspections, etc. Many turbines have mandatory hot section inspection intervals that split the TBO in half. The inspection may see nothing replaced...it's not about a risk of catastrauphic failure; it's about inspecting for condition.

An engine run under Part 91 may be run on condition far beyond TBO legally, and safely. When the engine does get overhauled, the highest stress components such as connecting rods, cams, etc, often remain in the engine. Cylinders are resurfaced, valves may or may not be replaced, piston rings are often replaced. Many accessories remain the same, some may get addressed, others may not. It's not about the risk of parts failing; it's about the engine wearing to the point where it's time to inspect it for tolerance and bring back into tolerances what has slipped out due to wear, breakage, etc.

 

[GravityHater]

Gravityhater you need to expand on that.

some details:

from the AOPA:
SBs not mandatory, FAA counsel says

The FAA lawyers have spoken: Service bulletins (SBs) are not — repeat not — mandatory for most Part 91 aircraft operators. That's exactly the decision AOPA had encouraged and expected.
That had been everyone's understanding of the regulations until two months ago, when an NTSB administrative law judge issued a ruling that clouded the issue.
The judge said that by not using the manufacturer's prescribed inspection technique while rebuilding an engine, the mechanic violated regulations. That seemed to imply that any manufacturer SB or instruction for doing something required by regulation took on the force of regulation itself.
Not so, said the FAA's Assistant Chief Counsel for Regulations Rebecca MacPherson.
She issued an "interpretation" of the regulations to answer a question raised by the Cessna Pilot Association's Mike Busch almost a year ago. (It appears the FAA was looking for a case to be able to clarify its position again after the NTSB decision.)
Busch asked if the regulations required a mechanic to perform a borescope inspection in addition to a pressure check of Teledyne Continental Motor (TCM) engine cylinders. That's what a TCM SB requires for 100-hour inspections.
She said no.
All that's required is that mechanics use "methods, techniques, and practices acceptable to the administrator."
Manufacturers can't issue 'substantive rules'

If manufacturers could make SBs mandatory, it would, "effectively authorize manufacturers to issue 'substantive rules,' as that term is used in the Administrative Procedures Act," MacPherson said.
But the FAA can't delegate rulemaking authority to manufacturers, and "substantive rules" must go through public notice-and-comment procedures required by law — and manufacturers can't do that.
SBs not mandatory for most AOPA members

Bottom line, if a manufacturer wants to require an owner to do something with his aircraft, the FAA has to approve it.
For most of the aircraft flown by AOPA members in noncommercial operations, the only thing you have to do is comply with the FAA's regulations and any applicable airworthiness directives (ADs).
A manufacturer's SB isn't mandatory. But check with your mechanic. Complying with an SB still might be a good idea. (And SBs sometimes become mandatory ADs after they've gone through the rulemaking process.)
The caveats: Most commercial operators do have to comply with SBs because it is required in their operations specifications.
For newer aircraft certificated under Part 23 (rather than CAR 3), SBs can be made mandatory if approved by the FAA and incorporated into the airworthiness limitations section of the aircraft's maintenance manual or instructions for continued airworthiness.
[FONT=Arial,Helvetica,sans-serif][SIZE=-2]August 28, 2006
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NTSB not the law on service bulletins, AOPA says

Service bulletins aren't mandatory for Part 91 aircraft owners, regardless of what the NTSB says. And AOPA is asking the FAA to remain firm in upholding that longstanding policy and interpretation of the law.
"The FAA's past and present opinion is that while service bulletins and instructions are not mandatory, they may be used by mechanics as an acceptable method, but not the only method, to show compliance with the regulations when performing maintenance, alterations, or preventive maintenance," AOPA Executive Vice President of Government Affairs Andy Cebula said in a letter to Nicholas A. Sabatini, the FAA's associate administrator for aviation safety.
"Should the FAA deem it necessary to issue a letter of interpretation in the interest of clarity and to avoid misapplication of existing regulations, the agency must reaffirm that service bulletins and service instructions are not mandatory for general aviation.... A manufacturer is not allowed to unilaterally require compliance with future service bulletins or instructions," said Cebula.
The issue was raised by the NTSB's ruling in the case of Administrator v. Law, in which a mechanic was accused of performing unairworthy repairs. In essence, the FAA claimed the mechanic used procedures not approved by the administrator.
But the NTSB took it a step farther, saying that "by not using the manufacturer's prescribed inspection technique, [the] respondent violated the regulations...."
That language would seem to require compliance with service bulletins or service instructions, known and yet to be issued, when referenced by the manufacturer's maintenance manual.
For general aviation aircraft certificated under CAR 3 (the majority of GA aircraft, designed before 1972), that's not the law. Any mandatory changes, repairs, or upgrades to an aircraft must be FAA approved and must go through the rulemaking process, including public comment, as required by the Administrative Procedures Act.
(For newer aircraft certificated under Part 23, service bulletins can be made mandatory if approved by the FAA and incorporated into the airworthiness limitations section of the aircraft's maintenance manual or instructions for continued airworthiness. Also, service bulletins are usually mandatory for aircraft flying in commercial service.)
In the case of Administrator v. Law, the FAA filed an appeal brief clearly stating that the mechanic was not in violation of the regulations for failing to follow the manufacturer's service bulletins, but rather for failing to use acceptable practices. "Why NTSB failed to mirror the FAA's language in their decision is a mystery," Cebula said.
AOPA told the FAA that the association was "concerned that the language used by the NTSB in their decision is contrary to established policy, practice, and law, and that mechanics and possibly FAA inspectors could misinterpret the NTSB's decision to require compliance with all manufacturers' service bulletins and instructions."
As FAA rulings have made clear through the years, following acceptable procedures does not necessarily mean mandatory adherence to service bulletins unapproved by the FAA.
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[GravityHater]

August 1 1,2006
CERTIFIED MAIL - RETURN RECEIPT REQUESTED
Mr. Michael D. Busch
1 127 Hetrick Avenue
Arroyo Grande, California 93420
Re: Request for Interpretation of 14 C.F.R. 4 43.13(a) and part 43, appendix D
Dear Mr. Busch:
On November 10, 2005, you requested, via E-mail, an interpretation of the above-referenced
regulations in the context of whether a procedure specified as "required" in a service bulletin
issued by a manufacturer is mandatory under the Federal Aviation Administration's (FAA)
maintenance regulations (1 4 C.F.R. part 43) for an aircraft operated only under 14 C.F.R. part 9 1 .
In general, unless a service bulletin is incorporated either directly or by reference into a document
that makes its requirements mandatory, the answer is no.
Based on the information you provided, we see nothing that indicates the service bulletin
referenced in your inquiry is mandatory under the FAA's regulations. Nevertheless, you opined
that manufacturer-issued service bulletins are mandatory under the regulations if they specify a
particular procedure or method of doing an item required by the regulations-in this case a
cylinder compression test performed during an annual or 100-hour inspection required by
14 C.F.R. part 43, appendix D. In support you stated that 14 C.F.R. 9 43.1 3(a) "requires that it
[maintenance, specifically, the compression test] be done in accordance with manufacturer's
instructions . . . ." You also stated: "Furthermore, 14 CFR 43.13(a) requires that the maintenance
shall be done using methods, techniques and practices prescribed by the manufacturer or other
methods, techniques and practices acceptable to the Administrator."
The text of section 43.13(a), however, states in pertinent part: "Each person performing
maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance
shall use the methods, techniques, and practices prescribed in the current manufacturer's
maintenance manual or Instructions for Continued Airworthiness prepared by its manufacturer, or
other methods, techniques, and practices acceptable to the Administrator." The text of that section
provides a person performing maintenance, alteration, or preventive maintenance on a product
with a number of permissible options when performing that work. A manufacturer may
legitimately incorporate a service bulletin into one of its maintenance manuals by reference. If it
does so, the data specified, and the method, technique, or practice contained therein, may be
acceptable to the Administrator. However, unless the method, technique, or practice prescribed
by a manufacturer is specifically mandated by a regulatory document, such aS an Airworthiness
Directive, its contents are not mandatory.
Your specific question concerns the application of a service bulletin issued by an engine
manufacturer to an inspection item required by 14 C.F.R. part 43, appendix D, "Scope and Detail
of Items (As Applicable To The Particular Aircraft) To Be Included In Annual And 100 Hour
Inspections." The inspection item at issue is at paragraph (d)(3) of the appendix, which states:
(d) Each person performing an annual or 100-hour inspection shall inspect
(where applicable) components of the engine and nacelle group as follows:
(3) Internal engine-for cylinder compression and . . . . If there is weak
cylinder compression, for improper internal condition and internal improper
tolerances.
According to your inquiry, on March 28,2003, Teledyne Continental Motors (TCM) issued
Service Bulletin SB03-3, titled "Differential Pressure Test and Borescope Inspection for
Cylinders." As you stated, the service bulletin "transmits TCM's current guidance concerning
how differential pressure tests (compression tests) of cylinders are to be done on TCM engines,
and supersedes TCM's previous guidance on the subject (service bulletin M84- 15)." You note
that a major difference between the two service bulletins is that the later bulletin requires that a
borescope inspection be done in conjunction with the differential pressure test. The abovereferenced
paragraph of appendix D, though requiring an inspection for improper internal
condition and tolerances if the compression test shows weak cylinder compression, does not
specify a particular method for doing so, i.e., it does not require a borescope inspection as the
means for determining the internal condition of the cylinders. Other methods could be used, for
example, cylinder disassembly and inspection. In fact, if no weak cylinder compression is
observed, no further cylinder inspection is required under that paragraph of appendix D.
In your example, although it would be good practice in view of the manufacturer's
recommendation to do a borescope inspection, its performance would not be required. If the
borescope inspection were not performed, the engine inspection would nevertheless have to meet
the criteria specified in section 43.13(a), ie., it would have to be done in accordance with the
"methods, techniques, and practices prescribed in the current manufacturer's maintenance manual
or Instructions for Continued Airworthiness prepared by its manufacturer, or other methods,
techniques, and practices acceptable to the Administrator." No violation of the regulation would
be incurred if the borescope inspection were not performed provided the engine inspection was
accomplished using methods, techniques, and practices acceptable to the Administrator.
A contrary result would lead to serious legal objections. It would mean that our regulations
effectively authorize manufacturers to issue "substantive rules," as that term is used in the
Administrative Procedures Act (APA), i. e., it would enable them to impose legal requirements on
the public. This would be objectionable for at least two reasons. First, the FAA does not have
authority to delegate its rulemaking authority to manufacturers. Second, "substantive rules" can
be adopted only in accordance with the notice-and-comment procedures of the APA, which does
not apply to manufacturers.
In sum, the fact that '"TCM requires a cylinder borescope inspection . . . ,'" does not make the
borescope inspection mandatory from a regulatory perspective. If TCM were to incorporate this
inspection into its current maintenance manual or Instructions for Continued Airworthiness and if
compliance with either of those documents were specifically mandated by regulation, or the FAA
were to incorporate SB03-3 into an AD or some other regulatory document, then the borescope
inspection would become mandatory.
We hope the above answer responds to your needs.
Sincerely,
Rebecca MacPherson
Assistant Chief Counsel for Regulations
Office of the Chief Counsel

 

[Lars!]

Mr. Michael D. Busch (Mike Busch) puts on a seminar and also writes a column on AvWeb called the savvy aviator. I highly recommend it if you are confused or concerned about TBO.

http://savvyaviator.com/

http://www.avweb.com/news/savvyaviator/187037-1.html
http://www.avweb.com/news/savvyaviator/186596-1.html
(free signup)

I'll try and paraphrase some of what I've heard and read, but you really need to read/hear it for yourself.

Saying an engine has a TBO of 2000 hours is like saying the average American lives to be age 72. The age of 72 is a useful number for insurance people, government officials, and statisticians. It is NOT a useful number for an emergency room physician! If your TBO is 2000 hours that is a useful number to figure out how much you should put in the savings account after each flight hour. But there is no good reason to euthanize your engine at 2000 hours, assuming it shows no signs of excessive wear or damage. (more on that below)

Just as men and women, Asian and Caucasian, poor and rich people have different average life spans, so do different engines used in different ways. An IO-360 used for aerobatics or touch and go's has a much different life span than an IO-360 used exclusively for 4 hour cross countries. If you have good genes and good habit you may well live 20 or 30 years beyond the "average" of 72.

The number one enemy of most owner flown engines is corrosion. We usually don't fly our aircraft enough to get rid of the moisture in the engine, which leads to corrosion of camshafts and other parts. The best thing you can do to keep your engine healthy is to fly it, regularly!

Most air carriers maintain their engines "on condition". The can do this because:

a. Their aircraft fly regularly
b. They monitor their engine condition on each flight via electronic monitoring and data analysis.
c. They have a maintenance program that regularly monitors engine performance and inspects for wear and damage.

(I know, they use turbines and we use pistons. The same principles apply.)

For the average piston owner the equivalent would be:

a. Fly as often as you can, and keep your engine (and plane) int he most non-corrosive environment you can. (Hangar, pre-heat, engine dryers all can help)
b. Download the data from your JPI, etc. to a PC program that can analyze it
c. In addition to your annual inspection, perform oil analysis at each oil change and cut your filter open to look for metal.

Like I said, there is more to it than that, but that is the basics. Hope that helps and check out the links above!

 

[avbug]

Carriers do not maintain aircraft on-condition only, except insofar as a condition outside specs means early maintenance. Carriers must respect all component inspection intervals, including TBO, hot section, etc. Carriers with an approved program can apply for and receive TBO extentions, and this is frequently done. If a carrier can show that their maintenance program is able to ensure continued operation beyond the original TBO, then they may be approved under their maintenance program to use different intervals.

A service bulletin of it's own accord is not mandatory. However, when included as a required inspection item under approved documents (such as inclusion in the maintenance manual), the inspection or work included in the SB must be accomplished, and becomes mandatory. Making it an AD is only one way of ensuring compliance.

 

[USMCmech]

Overhauling an engine at TBO is not a requirement for pt 91 operators. Many pt 135 operators have extensions on their engines allowing them to run past the published TBO.

TBO is an "estimate" of when the engine will NEED to be overhauled. Nothing more nothing less. Some engines will break down before TBO, and some others will last much longer.

Most American males need to have their heart overhauled between 55-60. Does that mean that you will get bypass surgery at 60, even if your doctor says that your cholesterol is low, BP is fine, ect. Of course not! There is no more reason to overhaul an engine if it is not showing any signs of failure just because it has run for a certian amount of time. Some desiel generators have been running constantly for DECADES whitout ever being shut down much less overhauled.

I personally know a pilot who flys pipleine patrol in a C-172 with an engine that has 7500 hours SMOH. He has replaced 2 cylinders in the past 10 years, he flies it almost daily, it still makes good compression, shows no sign of metal in the oil, still makes full take off power, ect. In short it is as good as the day it came out of the shop. He has no plans to EVER split the case untill the engine shows some sign of a problem.


OTOH, any engine not makeing full power, showing metal in the oil, or has a prop strike, ect. needs to be overhauled imeadiately, regardless of the number of hours it has beeen running. I have seen a IO-540 that needed to be rebuilt after only 100 hours. A large amount of metal was showing up in the oil anylsis and the filter. The main bearings had been heavily worn and the camshaft showed serious spalling.

Don't ever say to your self, "it runs like crap, but it was just overhauled so it must be OK". That is an exact quote from a pilot who had to make a forced landing after that freshly overhauled engine blew an exauxst valve.