AD 56-24-02

56-24-02 CONVAIR AND MARTIN: Applies to the Following Aircraft Equipped with PR-58E5-17 and -27 Carburetors in P&W Double Wasp CB Engines: Convair 240 and 340 (Except 340's with 440 Nacelles) and Martin 202A and 404. Also Applies to 340 Aircraft With 440 Nacelles and Equipped With PR-58E5-29 Carburetors; and to 440 Aircraft Equipped with PR-58E5-29 Carburetors.

Compliance required by first engine overhaul after January 1, 1957, but not later than September 1, 1957.

Normal fuel metering in carburetors incorporating the PR-58E5-17 and -27 "Transport Setting" may result in powers lower than those employed for aircraft certification. This occurs in the high power range with the control in the Auto-Rich position in cases where the carburetor meters on the rich side of the allowable limits. The amount of power loss will vary with different carburetors.

Performance information in the FAA-approved Airplane Flight Manual is based upon the maximum certificated power ratings ofthe engine. To obtain full rated power at manifold pressure limits for maximum continuous power, it is necessary to adjust the fuel mixture by the mixture control (takeoff power is not adversely affected by use of the full rich mixture position).

(P&W Engine Operation Information Letter No. 28, and P&W Service Bulletins Nos. 1602 and 1604 cover this subject in further detail.)

In order to insure obtaining the power used in aircraft certification, accomplish the following:

1. For MC power during one-engine-out operation use Auto-Lean mixture setting. Revise the pertinent airplane flight manuals accordingly to insure that the operation check procedure includes this item for engine-out operation.

2. Incorporate the leaner carburetor derichment jet per Bendix Service Bulletins Numbers 804 and 806. This applies to PR-58E5-17 and -27 carburetor settings only. The primary purpose of this change is to provide correct fuel flow for takeoff power. It does not materially affect fuel flow for maximum continuous power.

3. The Auto-Lean mixture control position should be plainly marked and identified.

NOTE: Selective manual leaning of the mixture by reference to the fuel flowmeter is not satisfactory because of the time and attention required for such a procedure in an emergency. It is necessary that the mixture adjustment be completed in one direct movement by placing the control in the Auto-Lean marked position.

Compliance with items 1 and 3 is not directly related to item 2, and should be accomplished as soon as possible regardless of the time of compliance with item 2.