Maintenance and Manufacturing Staff Instructions (MSI) No. 42

Subject: Number: MSI 42
Maintenance Scheddule Amendment Instructions for the Inspection of Thermal/Acoustic Insulation Revision No: 2
  Number of Pages: 2
File No: AARP-5009-3-42 Issue Date: June 30, 2004

1. Purpose

1.1 This MSI requires Civil Aviation Safety Inspectors to issue maintenance schedule amendment instructions with respect to thermal/acoustic insulation when there is evidence of increased levels of contamination caused by deficiencies in an air operator's maintenance schedule. This requirement applies to large aeroplanes, only where it is determined necessary to include or revise tasks and intervals for the inspection and removal of contamination.

1.2 This should be done under the authority of STD 625.86(10), which requires owners or operators to amend their approved maintenance schedules when so directed by the Minister. This requirement is a condition of the approval granted under CAR 605.86(2), which is delegated to inspectors under Schedule G-5 of the Delegation of Authority #150346.

2. Background

2.1 Flammability standards for thermal/acoustic insulation for transport category aeroplanes are in the process of being upgraded for improvement of the fire resistance of these materials. Research data has shown, however, that the flammability of most materials can change if the materials are contaminated. Contamination may be in the form of lint, dust, grease, liquids, etc., and can increase the material's susceptibility to ignition and flame propagation. On some large aeroplanes, for areas in which thermal/acoustic insulation is exposed to a higher incidence of contamination, the increased risk or susceptibility to ignition and flame propagation may require special mitigating action.

2.2 The intent of this MSI is to ensure that specific attention is directed to the inspection of thermal/acoustic insulation materials where increased levels of susceptibility to contamination are inadequately addressed within the air operator's maintenance schedule. Examples of areas so affected may include bilge areas and open-floor areas in cargo compartments. Based on findings and observations by Principal Maintenance Inspectors, these areas may require the addition of specific inspection tasks at appropriate intervals, and dedicated sign-offs, to an air operator's maintenance schedule.

3. Instructions

3.1 Principal Maintenance Inspectors with oversight responsibility for operators of large aeroplanes shall ensure that their operators have included the following in their approved maintenance schedules for the inspection of thermal/acoustic insulation:

  1. the manufacturer's recommended inspection tasks and intervals for thermal/acoustic insulation;
  2. specific inspection tasks and appropriate intervals for those areas containing thermal/acoustic insulation susceptible to increased levels of contamination;
  3. instructions for the disposition of contaminated insulation (accept/reject criteria); and
  4. procedures for refurbishing contaminated insulation where applicable.

Once established within an operator's maintenance schedule, the operator in accordance with their normal procedures may amend the frequency and detail of the inspections, where experience shows that the tasks or intervals can be adjusted and safety will not be compromised.

3.2 Where it has been found that there is evidence of increased levels of contamination caused by deficiencies in the maintenance schedule, the air operator should be requested to amend their approved maintenance schedule to make specific reference to tasks pertaining to the inspection of thermal/acoustic insulation for contamination. These tasks should be arranged to enable a dedicated sign-off in accordance with the structure of the complete check package.

4. Effective date

4.1 This instruction comes into effect immediately

5. HQ Contact

5.1 The responsible division indicated below may be contacted for information regarding this MSI:

Superintendent, Aircraft Evaluation - AARPG 
Aircraft Maintenance & Manufacturing 
Phone: (613) 990-1069
Facsimile: (613) 952-3298

D.B. Sherritt
Maintenance and Manufacturing