AD 83-07-15 ACTIVE

83-07-15 BRITISH AEROSPACE, AIRCRAFT GROUP, SCOTTISH DIVISION: Amendment 39-4617. Applies to Model HP.137 Jetstream MK.1 and Jetstream Series 200 airplanes certificated in any category.

Compliance: Required as indicated, unless already accomplished.

To prevent cracking of the front pressure bulkhead boundary angle and possible catastrophic depressurization, accomplish the following:

a) For all affected airplanes with 12,900 or more flights, unless British Aerospace Modification No. 5115 is installed, within the next 100 flights after the effective date of this AD, apply a red line to the cabin differential pressure gauge to indicate that the maximum allowable differential pressure is 2.5 PSI. Extend the red line to the case of the instrument to avoid confusion if the glass cover is rotated.

b) For all other affected airplanes with less than 12,900 flights, unless British Aerospace Modification No. 5115 is installed, within the next 100 flights after the effective date of this AD or upon the accumulation of 2,000 flights, whichever occurs later, apply a red line to the cabin differential pressure gauge to indicate that the maximum allowable differential pressure is 4.0 PSI except that in no case shall airplanes in this group be allowed to accumulate more than 13,000 flights without having the cabin differential pressure gauge remarked with a red line at 2.5 PSI in accordance with paragraph a) of this AD. Extend the red line to the case of the instrument to avoid confusion if the glass cover is rotated.

c) For all aircraft modified per paragraphs a) and b) of this AD, fabricate a placard to read as follows and install it adjacent to the pressure differential gauge:

1) For aircraft affected by paragraph a) of this AD: "2.5PSI max. press. difference."

2) For aircraft affected by paragraph b) of this AD: "4.0PSI max. press. difference."

d) Within the next 500 flights after the effective date of this AD on all affected airplanes, unless British Aerospace Modification No. 5115 is installed, modify the pressurization systems in accordance with British Aerospace, Aircraft Group Modification No. 5151, Issue 1, dated August 1981 or Modification No. 5152, Issue 1, dated August 1981, as appropriate to limit maximum pressurization to 4.0 PSI or 2.5 PSI respectively.

e) For purposes of complying with this AD, subject to the acceptance by the assigned FAA maintenance inspector, the number of flights may be determined by multiplying each airplane's hours time-in-service by two.

f) The modifications specified by paragraphs a), b) and (c), or d) of this AD are no longer applicable when British Aerospace Modification No. 5115 is installed.

g) Aircraft may be flown in accordance with FAR 21.197 to a location where this AD can be accomplished.

h) An equivalent method of compliance with this AD if used must be approved by the Manager, Aircraft Certification Staff, AEU-100, Europe, Africa and Middle East Office, FAA, c/o American Embassy, 1000 Brussels, Belgium.

This amendment becomes effective on April 14, 1983.