AD 72-14-06

72-14-06 ROLLS-ROYCE: Amdt. 39-1479. Applies to series Dart Model 542-4, -4K, -10, -10J, and -10K engines. These engines are installed on but not necessarily limited to those Convair Model 340/440 airplanes (commonly known as Convair 600 and 640) which have the subject engines installed as a result of modification and NAMC YS-11 airplanes.

Compliance is required as indicated.

To prevent possible fatigue failure of first stage (low pressure) impellers, accomplish the following:

(a) For a first stage (low pressure) impeller that does not incorporate Rolls Royce Dart Modification 1455, within the next 100 flights after the effective date of this AD or before the accumulation of 11,000 flights on that impeller, whichever occurs later, comply with subparagraph (c)(1) or (c)(2) and thereafter comply with paragraph (d) or (e) as applicable.

(b) For a first stage (low pressure) impeller that incorporates Rolls Royce Dart Modification 1455, within the next 100 flights after the effective date of this AD or before the accumulation of 11,000 flights after the incorporation of Rolls Royce Dart Modification 1455, whichever occurs later, comply with subparagraph (c)(1) and thereafter comply with paragraph (d) or (e) as applicable.

(c) Comply with subparagraph (1) or (2) of this paragraph as prescribed in paragraphs (a), (b), (d), and (e).

(1) Remove the first stage (low pressure) impeller from service and replace it with -

(i) A first stage (low pressure) impeller that does not incorporate Rolls Royce Dart Modification 1455 and which has accumulated less than 11,000 flights in service; or

(ii) A first stage (low pressure) impeller that incorporates Rolls Royce Dart Modification 1455 and which has accumulated less than 11,000 flights in service since the incorporation of that modification.

(2) For an impeller that does not have Rolls Royce Dart Modification 1455 incorporated, incorporate that modification.

(d) For an impeller that has been installed in compliance with subparagraph (c)(1)(i), before the accumulation of 11,000 flights on that impeller comply with subparagraph (c)(1) or (c)(2).

(e) For an impeller that has been installed in compliance with subparagraph (c)(1)(ii) or modified in accordance with subparagraph (c)(2), before the accumulation of 11,000 flights since the incorporation of Rolls Royce Dart Modification 1455 on that impeller comply with subparagraph (c)(1).

(f) For the purpose of complying with this AD, a flight shall consist of an engine operating sequence consisting of an engine start, take-off operation, landing, and engine shutdown. The number of flights may be determined by actual count or, subject to acceptance by the assigned FAA Maintenance Inspector, may be calculated by dividing the compressor section's time in service by the operator's fleet average time per flight for airplanes equipped with the subject type engines.

This AD supersedes the telegraphic ADon the same subject issued on April 13, 1972.

NOTE: Rolls Royce Dart Alert Service Bulletin No. DA 72-391 Revision 1, dated May 1, 1972 refers to this matter.

This amendment is effective upon publication in the Federal Register as to all persons except those persons to whom it was made immediately effective by the telegram dated May 31, 1972, which contained this amendment.