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Legal Interpretations

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DiSalvatore-Mercedes Transcription Inc 2019

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Summary

The Question

Is a turbine engine manufacturer's recommended time between overhaul (TBO) in an engine maintenance manual mandatory for an aircraft operated under 14 CFR part 91?

Background

The president of Mercedes Transcription, Inc. operates a Citation Bravo with Pratt & Whitney PW530A engines under 14 CFR part 91. The manual's recommended 4,000-hour initial TBO appears under Scheduled Maintenance Checks, not in the FAA-approved Airworthiness Limitations section.

The FAA’s Interpretation

No, unless the TBO is specified in the FAA-approved Airworthiness Limitations section or required by an Airworthiness Directive or other FAA regulation. Under 14 CFR 43.16 and 14 CFR 91.403(c), replacement times in an FAA-approved Airworthiness Limitations section are mandatory, but this engine's TBO is listed elsewhere in the manual. Following it may be good practice, but it is not mandatory for 14 CFR part 91 operations.

Requester
DiSalvatore
Organization
Mercedes Transcription Inc
Issued
May 7, 2019
Subjects
General Operating & Flight Rules · Air Carrier & Commercial Operations · Maintenance & Repair Stations

Regulations Cited

  • 14 CFR 43.13
  • 14 CFR 43.16
  • 14 CFR 91.403
  • 14 CFR 135.421
  • 14 CFR 145.109

Page 1

U.S. Department
of Transportat'ion
Federal Aviation
Administration
HAR -y
Mr. John DiSalvatore
26 Nurmi Drive
Ft. Lauderdale, FL 33301
Office of the Chief Counsel
800 Independence Avenue, S.W.
Washington, D.C. 20591
Re: Whether a Manufacturer's Recommended Time Between Overhaul
(TBO) in an Engine Maintenance Manual is Mandatory for an Aircraft
Operated under 14 CFR Part 91
Dear Mr. DiSalvatore:

This responds to your August 24, 2018 E-mail asking whether a turbine engine manufacturer's recommended timebetween overhaul (TBO) in an engine maintenance manualis-rnandatory for an aircraft operated under 14 CFR Part 91. The answer is no, unless that TBO is specified in the applicable FAA-approved Airworthiness Limitations section or is required by an Airworthiness Directive (AD) or other FAA regulation.

You asked specifically about the TBO for a Pratt & Whitney Model PW530 turbine engine on a Citation Bravo you operate under 14 CFR part 91. Note 2 in this engine's type certificate data sheet (TCDS) states that life-limited parts are listed in the Airworthiness Limitations section of the engine's maintenance manual. Under 14 CFR §§ 43.16 and 91.403(c), replacement times, inspection intervals, and related procedures specified in an FAA-approved Airworthiness Limitations section of a maintenance manual are mandatory. The TBO for this engine, however, is not listed in the FAA-approved Airworthiness Limitations section of the maintenance manual-rather, it is found in another section of the manual under Scheduled Maintenance Checks. This section (05-20-00, Rev. 47.0- 06/AUG/18) provides the Pratt & Whitney "TBO" by stating: "The recommended initial time between overhaul (TBO) for all PW530A engines is 4000 hours." Accordingly, while it may be a good practice for an operator to follow an engine manufacturer's recommended TBO, doing so is not mandatory under the FAA' s regulations for operations under part 91.

The FAA' s Office of the Chief Counsel has addressed similar issues in prior letters and memorandums of interpretation. We are enclosing the following for your assistance in assessing similar issues in the future:

Page 2

Legal Interpretation of "Current" as it Applies to Maintenance Manuals and Other Documents Referenced in 14 C.F.R. §§ 43.13(a) and 145.109(d), dated August 13, 2010, addressed to Manager, A WP-230, from Assistant Chief Counsel for Regulations, AGC-200; Response to Request for Interpretation of 14 C.F.R. § 135.421 (b), dated May 23, 2017, addressed to John S. Duncan, Director Flight Standards Service, from Assistant Chief Counsel for Regulations; Applicability of 14 CFR Part 43 Maintenance Regulations for Aircraft Operated under 14 CFR Parts 91and135, dated July 5, 2017, addressed to W. Harvey Cash, from Assistant Chief Counsel for Regulations, AGC-200; Request for Legal Interpretation on the Use of Manufacturers' Publications to Determine Inspection Intervals and Replacement Times, dated April 22, 2011, addressed to Albert T. MacMillan, from Assistant Chief Counsel for Regulations.

I trust this letter is responsive to your questions. This response was prepared by Edmund A verman, an attorney in the Regulations Division in the Office of the Chief Counsel, and coordinated with the Aircraft Maintenance Division (AFS-300) in the FAA's Flight Standards Service. If you have additional questions regarding this matter, please contact us at your convenience at 202-267-3073.

Sincerely,

Lorelei D. Peter

Assistant Chief Counsel for Regulations, AGC-200

Enclosures

Page 3

Young, Kim L (FAA)

From: Doan, Viet (FAA)

Sent:

To:

Friday, August 24, 2018 2:13 PM

Young, Kim L (FAA)

Subject: RE: Legal Interpretation

Yes, this looks like a question for Skip. Thanks!

From: Young, Kim L (FAA)

Sent: Friday, August 24, 2018 2:06 PM

To: Doan, Viet (FAA) <viet.doan@faa.gov>

Subject: FW: Legal Interpretation

Richard

Please let me know if t his belong to AGC-210?

Thanks

Kim L Young

Management & Program Analyst

Regulations Division, AGC-200

---"&~Federal Register Lia..:..:is~o...;_n~---------- -----· .......___

(202) 267 -3073 office

(202) 267 -7971 fax

Kim.L.Young@faa.gov

From: John DiSalvatore <John@mercedestranscription.com>

Sent: Friday, August 24, 2018 12:13 PM

To: Young, Kim L (FAA) <kim.l.young@faa.gov>

Cc: John DiSalvatore <Joh n@rnercedestranscription.com>

Subject: Re : Legal Interpretation

Ms. Young, I'm requesting a written legal interpretat ion ofTurbine TBO's under Pa rt 91 operation. I'm told I can go beyond TBO if it's a Part 91 ope ration. We obviously will still conform with a maintenance program post TBO. The plane is a Citat ion Bravo with P&W 530-A engines.

My address: 26 Nurmi Drive

Ft. LAUDERDALE FL

33301

Feel free to contact me with any questions.

John DiSalvat ore

President

Mercedes Transcription, Inc.

4007-F Norbeck Road

Rockville, Maryland 20853

Page 4

(301) 758-6300 mobile

John@mercedestranscription.com www.mercedestranscription.com On Aug 23, 2018, at 8:24 AM, "kim .1.young@faa.gov" <kim .l.you ng@faa.gov> wrote:

Mr. Salvatore

You w ill need to address your request t o Lorelei Peter, Assistant Chief Counsel for Regulations 800 Independence Avenue, SW Washington, DC 20591. You can also submit by email to me but please make sure your US mailing address is on your request.

Thanks

Kim L Young

Management & Program Analyst

Regulations Division, AGC-200

& Federal Register Liaison

(202) 267 -3073 office

(202) 267-7971 fax

Kim. L.Young@faa.gov

Regulations Referenced

14 CFR Part 9114 CFR 43.1614 CFR 91.40314 CFR 43.1314 CFR 145.10914 CFR 135.42114 CFR Part 43

Snapshot retrieved August 6, 2026.

Summary

The Question

Is a turbine engine manufacturer's recommended time between overhaul (TBO) in an engine maintenance manual mandatory for an aircraft operated under 14 CFR part 91?

Background

The president of Mercedes Transcription, Inc. operates a Citation Bravo with Pratt & Whitney PW530A engines under 14 CFR part 91. The manual's recommended 4,000-hour initial TBO appears under Scheduled Maintenance Checks, not in the FAA-approved Airworthiness Limitations section.

The FAA’s Interpretation

No, unless the TBO is specified in the FAA-approved Airworthiness Limitations section or required by an Airworthiness Directive or other FAA regulation. Under 14 CFR 43.16 and 14 CFR 91.403(c), replacement times in an FAA-approved Airworthiness Limitations section are mandatory, but this engine's TBO is listed elsewhere in the manual. Following it may be good practice, but it is not mandatory for 14 CFR part 91 operations.

Requester
DiSalvatore
Organization
Mercedes Transcription Inc
Issued
May 7, 2019
Subjects
General Operating & Flight Rules · Air Carrier & Commercial Operations · Maintenance & Repair Stations

Regulations Cited

  • 14 CFR 43.13
  • 14 CFR 43.16
  • 14 CFR 91.403
  • 14 CFR 135.421
  • 14 CFR 145.109