91-06-11 MESSERSCHMITT-BOLKOW-BLOHM (MBB): Amendment 39-6901. Docket No. 90-ASW-45.
Applicability: All MBB Model BK-117 series helicopters, certificated in any category with the following serial numbers (S/N):
S/N's 7001 up to and including 7261 (Ref. ASB-MBB-BK 117-90-104 dtd. August 11, 1989)
S/N's 7001 up to and including 7241 (Ref. ASB-MBB-BK 117-90-105 dtd. May 23, 1990)
S/N's 7001 up to and including 7215 (Ref. ASB-MBB-BK 117-60-107 dtd. December 12, 1989)
S/N's 7001 up to and including 7215 (Ref. ASB-MBB-BK 117-60-108 dtd. December 22, 1989)
Compliance: Required within the next 50 hours' time in service or within 28 days after the effective date of this AD, whichever comes first.
To prevent uncontrolled fuel vapor ignition which could result in an explosion, fire, and the subsequent loss of the helicopter, accomplish the following:
(a) Modify and retrofit the bonding jumpers on the landing gear in accordance with MBB Alert Service Bulletin, ASB-MBB-BK 117-90-104, dated August 11, 1989.
(b) Install electrostatic dischargers and modify the fuel vent outlet parts in accordance with MBB Alert Service Bulletin, ASB-MBB-BK 117-90-105, dated May 23, 1990, with the following changes to Figure 2, page 10 of 12:
(1) The Note 4 dimension is changed from 145-155 mm to 125 mm.
(2) The P/N 117-181001.03 bracket shown in View A must be rotated 180 degrees.
(3) The added washer, P/N LN 9016-08L (Item 15), must be relocated to the top of the bolt, between the cable terminal and the bolt head, instead of as shown.
(4) In addition, conduct a control freedom check; i.e. collective down, cyclic full forward, aft, left, and right and repeat with collective full-up to assure there is no tension in the cables at any control position.
NOTE: These four changes are intended to allow enough slack for blade folding and to keep the grip bolt from contacting the sleeve, thus allowing full pitch angle change without straining the jumper.
(c) Remove, without replacing, the fuel return lines in accordance with MBB Alert Service Bulletin, ASB-MBB-BK 117-60-107, dated December 12, 1989.
(d) Inspect fuel supply tank vent outlet ports in accordance with MBB Service Bulletin SB-MBB-BK 117-60-108 dated, December 22, 1989, to assure that they are not closed by paint.
(e) An alternate method of compliance with this AD or adjustment of the compliance times, which provides an equivalent level of safety, may be used if approved by the Manager, Rotorcraft Standards Staff, ASW-110, Federal Aviation Administration, Fort Worth, Texas 76193-0110, telephone (817) 624-5110.
(f) In accordance with FAR Sections 21.197 and 21.199, the helicopter may be flown to a base where the inspections required by the AD may be accomplished.
The procedures shall be done in accordance with the following service bulletins: ASB- MBB-BK 117-90-104, dated August 11, 1989; ASB-MBB-BK 117-90-105, dated May 23, 1990; ASB-MBB-BK 117-60-107, dated December 12, 1989; and ASB-MBB-BK 117-60-108, dated December 22, 1989, as applicable. 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, P.O. Box 80 11 40, 8000 Munich 80, West Germany. 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, N.W., Room 8301, Washington, DC.
This amendment (39-6901, AD 91-06-11) becomes effective on April 9, 1991.