A spar crack, an old blend-out and a fleet to protect
You are performing a 100-hour inspection on a PAC 750XL used for skydiving. While inspecting the wing centre-section you find a 15 mm fatigue crack originating at a bolt hole in the forward spar carry-through, with fretting debris around the fastener. The aircraft has 6,850 hours. In the aircraft logbook you see that 14 months ago the same operator's other 750XL had a "similar crack" at the same location, which was blended out and returned to service with a logbook entry signed by an engineer who has since left. No defect report or manufacturer notification appears in the records. The operator's chief engineer tells you the previous repair was "approved by the manufacturer over the phone" and asks you to do the same blend and sign it out, because the aircraft is needed for a busy weekend and reporting will "ground the whole fleet".
1. What are your reporting obligations on finding this crack?
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A crack in a primary structural element such as a spar carry-through is a serious airworthiness matter. The defect reporting requirements (under Part 43 and the operator's Part 135 arrangements) require defects of this kind - particularly those that could affect other aircraft of the type - to be reported to the CAA, and the manufacturer/type certificate holder should be notified so it can assess fleet risk. The fact that a similar crack was found on a sister aircraft 14 months earlier makes this more than an isolated finding: it looks like a fleet issue, and the CAA needs that context to decide whether an airworthiness directive or other action is required.
Reporting is your obligation as the person who found the defect; it is not a decision for the chief engineer. The absence of any earlier report is itself a concern that should be recorded and raised. Do not let the commercial consequence (grounding the fleet) affect the judgement - the purpose of the reporting system is precisely to stop a known defect being repeated across a fleet.
2. Can you carry out the blend-out repair and release the aircraft?
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No, not on the information available. A blend-out of a crack in primary structure is a repair, and depending on its extent it may be a major repair or design change requiring approved data - manufacturer structural repair data, a design approval, or an approved engineering assessment under Part 21. "Approved over the phone" is not approved data and cannot be certified against; if the manufacturer did provide approval, there should be a written record (repair drawing, letter, or service instruction) that you can reference in the logbook.
Even with approved data, you would need to establish the allowable blend depth, inspect for additional cracking after blending, apply the required protective treatment, and record the repair with dimensions and the data used. The aircraft should be quarantined in the meantime, the cracked area preserved and photographed, and the part not disturbed more than necessary. Releasing it for a weekend of skydiving on the basis of an undocumented verbal approval would be a false certification and would put jump pilots and passengers at risk.
3. What should happen about the earlier blend-out on the sister aircraft, and how do you deal with the chief engineer?
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The earlier repair needs to be examined on its own merits: locate the logbook entry, identify the data referenced, and check whether the blend was within approved limits and properly recorded. If there is no approved data, the repair is unapproved and the aircraft's airworthiness is in question; the CAA should be told as part of the defect report, and the operator should not fly that aircraft until the repair is validated. The engineer who signed it out may need to be contacted for the basis of the approval, and the quality manager should review how an undocumented repair was accepted.
With the chief engineer, be direct: you will report the defect and you will not sign a repair without approved data. Put the refusal and the reasons in writing to the chief engineer and the quality manager, and keep copies. If the operator flies either aircraft without resolving the issue, report that to the CAA. "Grounding the fleet" is the correct outcome if the fleet has a systematic cracking problem - the alternative is discovering it after a structural failure.