AD 90-23-08

90-23-08 MESSERSCHMITT-BOLKOW-BLOHM (MBB): Amendment 39-6778. Docket No. 89-ASW-68.

Applicability: All MBB Model BO105C and BO105S series helicopters, certified in any category, that operate in snow conditions.

Compliance: Required as indicated, unless already accomplished.

To prevent engine flameout resulting from ingestion of layers of wet snow in engine inlets, accomplish the following:

(a) Install a continuous ignition system in accordance with MBB Service Bulletin, SB-BO 105-80-108, "Optional Equipment-Retrofit of Continuous Ignition System," dated May 11, 1990.

(b) Incorporate into the applicable Rotorcraft Flight Manual (RFM) the FAA- approved flight manual Revision No. 2/16, dated October 1, 1989, which includes the following paragraphs 2.8.2.4 and 2.8.2.5: 2.8.2.4 Snow Conditions

Operation in snow is prohibited, except when the Continuous Ignition System) OPT 19 is installed and switched on. Prior to takeoff, snow and ice must be removed, particularly from the following areas: - cabin roof - transmission cowling interior in front of engine air intakes - transmission compartment interior - engine inlet deflector shield.

NOTE: After engine operation in snow make an entry in the logbook. Maintenance action is required in accordance with the Allison Operation and Maintenance Manual.

2.8.2.5 Engine Inlet Deflector Shield The engine inlet deflector shield must be installed at all times.

The procedures shall be done in accordance with MBB Service Bulletin SB-BO 105-80- 108, which incorporates the following pages: 1, 2, and 8, Rev. 1, dated May 11, 1990; 3-7 and 9, Original, dated June 12, 1989. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from MBB Helicopter Corporation, 900 Airport Road, P.O. Box 2345, West Chester, PA 19380. Copies may be inspected at the Office of the Assistant Chief Counsel, FAA, 4400 Blue Mound Road, Fort Worth, Texas, or at the Office of the Federal Register, 1100 L Street, NW., Room 8301, Washington, DC.

This amendment (39-6778, AD 90-23-08) becomes effective on December 3, 1990.