AD 88-21-06

88-21-06 ROLLS-ROYCE plc: Amendment 39-6031. Applies to Rolls-Royce plc (R-R) (Formerly Rolls- Royce Limited) Dart Mks. 506, 510, 511, 514, 525, 526, 527, 528, 529, 531, 532, and 542 series turboprop engines and all variants.

Compliance is required as indicated, unless already accomplished.

To prevent low cycle fatigue failure of high pressure (HP) impellers and low pressure (LP) impellers, accomplish the following:

(a) Remove from service HP impellers installed in Dart Mks. 506, 510, 511, 514, and all variants, in accordance with the following schedule:

(1) HP impellers to Mod 844 standard which have accumulated 8,000 or more total flights since new on the effective date of this AD, within the next 400 flights from the effective date of this AD, or within the next 12 calendar months from the effective date of this AD, whichever comes later.

(2) HP impellers to Mod 1455 standard which have accumulated 8,600 or more total flights since new on the effective date of this AD, within the next 400 flights from the effective date of this AD, or within the next 12 calendar months from the effective date of this AD, whichever comes later.

(3) HP impellers to Mod 844 standard which have accumulated less than 8,000 total flights since new on the effective date of this AD, at or prior to accumulating 8,400 total flights since new, or within 12 calendar months from the effective date of this AD, whichever comes later.

(4) HP impellers to Mod 1455 standard which have accumulated less than 8,600 total flights since new on the effective date of this AD, at or prior to accumulating 9,000 total flights since new, or within 12 calendar months from the effective date of this AD, whichever comes later.

NOTES: (1) Total flights since new is defined as the total number of flights accumulated by the part since first installation in an engine. This total includes all Mod standards the part has operated under.

(2) This action establishes a new Overhaul Manual Chapter 5 life limit for HP impellers, as noted in items (a)(3) and (a)(4) above.

(3) Reference R-R Service Bulletin (SB) DA72-496, dated June 1986.

(b) Remove from service HP impellers installed in Dart Mks. 525, 526, 527, 528, 529, 531, 532, 542, and all variants, on or before the life limits in the following schedule:

Life Limit in Number of Flights

Dart Mk. Pre-Mod 797 Mod 797 Open Bore Processed Mod 797 Pre-Mod 1455 Mod 1455 Mod 1475 525 thru 529 4,500 11,000 14,000 NC NC 531 and 532 4,500 11,000 14,000 NC NC 542 NA NA 12,000 16,000 14,500

(Since incorp. of Mod 1455)

NA - Model not applicable to specific impeller.

NC - Life limits not covered by this AD. Information relating to these impellers is contained in the manufacturer's appropriate overhaul manual.

NOTE: The above noted HP impeller life limits were published in AD 73-21-04, Amendment 39-1734 (38 FR 27819), and have notchanged. This section is only intended to reprint for clarity, already existing AD requirements with respect to current R-R SB information.

(c) Remove from service LP impellers installed in Dart Mks. 506, 510, 511, 514, 525, 526, 527, 528, 529, 531, 532, 542, and all variants, on or before the life limits in the following schedule:

Limit in Number of Flights

Dart Mk. Mod 797 Open Bore Processed Mod 797 Pre-Mod 1455 Mod 1455 506 10,500 11,250 11,250 510 10,500 11,250 11,250 511 10,500 11,250 11,250 514 10,500 11,250 11,250 525 thru 529 9,000 9,000 9,000 531 and 532 9,000 9,000 9,000 542 NA 9,000 9,000

NA - Model not applicable to specific impeller.

NOTES: (1) LP impellers to Mod 1455 Part 1 standard (manufactured by R-R to this standard) are not affected by this AD. Life limits for this part are quoted in the overhaul manual, Chapter 5, "Time Limits".

(2) The above noted LP impeller life limits were published in AD 73-21-04, Amendment 39-1734 (38 FR 27819), and have not changed. This AD, with respect to LP impeller life limits, is only intended to reprint for clarity, already existing AD requirements with respect to current R-R SB information.

(3) Rolls-Royce Dart SB 72-463 also pertains to LP impeller life limits.

(d) Aircraft may be ferried in accordance with provisions of FAR 21.197 and 21.199 to a base where the AD can be accomplished.

(e) Upon request, an equivalent means of compliance with the requirements of this AD may be approved by the Manager, Engine Certification Office, Engine and Propeller Directorate, Aircraft Certification Service, Federal Aviation Administration, 12 New England Executive Park, Burlington, Massachusetts 01803.

(f) Upon submission of substantiating data by an owner or operator through an FAA Airworthiness Inspector, the Manager, Engine Certification Office, Engine and Propeller Directorate, Aircraft Certification Service, may adjust the compliance schedules specified in this AD.

This amendment supersedes Amendment 39-1734 (38 FR 27819), AD 73-21-04.

This amendment, 39-6031, becomes effective on November 6, 1988.