Determination of the Corrosion Levels

A. Find the Corrosion Levels.

(1) Corrosion found on a structure when you use the Corrosion Program and Corrosion Prevention 7(CPCP) Baseline Program will help find the extent of the corrosion.

(2) The second and subsequent inspections will find how well the CPCP program has been prepared or if there is a need to make adjustments to the Baseline Program.

(3) A good quality CPCP is one that controls corrosion to Level 1 or better.

(4) If Level 2 corrosion is found during the second or subsequent inspection, you must do something to decrease the future corrosion to Level 1 or better.

(5) If Level 3 corrosion is found, you must also do something to decrease the future corrosion to Level 1. Also, a plan to find or prevent Level 3 corrosion in the same area on other airplanes must be added to the CPCP.

(6) All the corrosion that you can repair in the allowable damage limits, (less than 10 percent of the part thickness) is Level 1 corrosion.

(7) If all corrosion is Level 1, the CPCP is correctly prepared.

(8) If you must reinforce or replace the part because of corrosion, the corrosion is Level 2.

(9) If the part is not airworthy because of the corrosion, you must do an analysis to find out if the corrosion is Level 3.

(10) The chart found in this section will help find the level of the corrosion.

(11) The probability that the same problem will occur on another airplane is dependent on several factors such as: past maintenance history, operating environment, years in service, inspectability of the corroded area and the cause of the problem

Level 2 Corrosion Findings

A. All Level 2 corrosion that is more than the rework limits of the approved repair procedures must be reported to Cessna Aircraft Company. Cessna Aircraft Company engineering will do an analysis to make sure the corrosion is not an urgent airworthiness concern.

B. When doing the analysis, Cessna Aircraft Company will consider:

(1) Can the cause of the corrosion be identified, such as a chemical spill or protective finish breakdown?

(2) Has the same level of corrosion been found on other airplanes?

(3) Are the corrosion protection procedures applied during manufacture the same for earlier and later models?

(4) Age of the corroded airplane compared to others checked.

(5) Is the maintenance history different from the other airplanes in the fleet?

Actions Follow Corrosion

 A. If corrosion is found, find the corrosion level, then do the necessary steps for a specific inspection.

B. If Level 1 corrosion is found during the first CPCP inspection.

(1) Repair the structure. Contact Cessna  for an approved repair procedure.

(2) Continue with the Baseline Program.

(a) Optional: Document the results of the inspection for use in validating program compliance.

C. If Level 2 corrosion is found during the first CPCP inspection.

(1) Repair the structure. Contact Cessna  for an approved repair procedure.

(2) Report the details of the corrosion you see to Cessna Aircraft Company and the DGCA.

(3) Continue to use the Baseline Program but check the corroded area carefully when you do a subsequent CPCP inspection.

(4) It is recommended that you record the results of the inspection to show compliance with the program.

D. If Level 3 corrosion is found during the first CPCP inspection.

(1) Immediately contact Cessna Aircraft Company and the DGCA of the corrosion you found. 

(2) Give sufficient information to make sure that the condition is a possible urgent airworthiness concern for your fleet. Get assistance from Cessna Support to develop a plan of action.

(3) Apply the corrosion program inspection, which includes the repair of the structure. Contact Cessna Aircraft Company for an approved repair procedure.

(4) Do a report that has the information of the findings. Refer to Corrosion Prevention And Control Program Reporting System - Description And Operation.

(5) Continue with the Baseline Program and other steps of procedure required by the DGCA. Examine this area carefully during future inspections.

E. If no corrosion is found during the second or subsequent CPCP inspection:

(1) Continue with the current Corrosion Prevention and Control Program. No adjustment of the current program is required.

(2) It is recommended that you record the results of the inspection for a possible increase of the corrosion inspection interval.

.