AD 72-16-05

72-16-05 ROLLS ROYCE (1971) LTD: Amendment 39-1491 as amended by Amendment 39-1568. Applies to Dart Series Models 506, 510, 511, 514, 525 through 529, 531, 532, and 542 engines and all variants.

Compliance required as indicated unless already accomplished.

To prevent engine failures resulting from fatigue cracks of the impellers specified in Column 2 of the following tables, accomplish the following:

(a) Within the next 50 flights after the effective date of this AD or before the accumulation of the number of flights specified in Column 3, for the applicable impeller, whichever occurs later, and thereafter at intervals not to exceed the number of flights specified in Column 3, replace the applicable impellers specified in Column 2 when they are installed on the engines specified in Column 1 with impellers having the same part number or a part number approved for that engine which have not exceeded their life limits.

(Column 1) DART ENGINE SERIES (Column 2) IMPELLERS (Column 3) LIFE LIMITS (FLIGHTS)

Second stage impellers incorporating all Pre 797 Modifications 4,500

Second stage impellers incorporating Modification 797 which have not been Open Bore Processed.* 9,000 Models 506, 510, 511 and 514 and all variants First and second stage impellers incorporating Modification 797 Open Bore Processed.* 1st stage - 10,500 2nd stage - 6,000

Second stage impeller incorporating Modification 1455. 14,000 since the incorporation of Modification 1455

Second stage impellers incorporating all Pre 797 Modifications 4,500 Models 525 through 529, 531, and 532 and all variants Second stage impellers incorporating Modification 797 which have not been Open Bore Processed.* 14,000

First and second stage impellers incorporating Modification 797 Open Bore Processed.* lst stage 9,000 2nd stage - 11,000

*NOTE: For purposes of this AD "Open Bore Processed" means that the impeller during an overhaul subsequent to the incorporation of Modification 797, has been stripped and anodized or anodized, without the impeller bore being fitted with blanks, or that leakage past the blanks has occurred due to an improper fitting of the blanks.

(b) Within the next 50 flights after the effective date of this amendment, (Amdt. 39-1568, effective December 4, 1972), or before the accumulation of the number of flights specified in Column 3, for the applicable impeller, whichever occurs later, and thereafter at intervals not to exceed the number of flights specified in Column 3, replace the applicable impellers specified in Column 2 when they are installed on the engines specified in Column 1 with impellers having the same part number or a part number approved for that engine, which have not exceeded their life limits.

Column 1 DART ENGINE SERIES Column 2 IMPELLERS Column 3 LIFE LIMITS (FLIGHTS) Models 506, 510, 511, 514 and all variants First stage impellers incorporating Modification1455 14,000 since the incorporation of Modification 1455 Models 525 through 529, 531, and 532 and all variants First stage impellers incorporating Modification1455 11,500 since the incorporation of Modification 1455 Models 542-4 and 542-10 and all variants Second stage impellers incorporating all PreModification 1455 modifications

Second stage impellers incorporating Modification 1455

Second stage impellers incorporating Modification1475 12,000

16,000 since the incorporation of Modification 1455

14,500

(c) For the purpose of complying with this AD a flight shall constitute an engine operating sequence consisting of an engine start, takeoff operation, landing and engine shut-down. The number of flights may be determined by actual count or, subject to approval, by the FAA assigned maintenance inspector, by dividing the impeller time in service by the operator's fleet average time per flight.

Amendment 39-1491 became effective July 31, 1972.

Thisamendment 39-1568 becomes effective December 4, 1972.