Cracked Heat Exchanger at an Outstation

No. The reasoning runs like this:

• Deferral is not a pilot's power and not a vague permission. Defects are controlled by the operator's approved maintenance programme and, where the operator has one approved, a minimum equipment list (MEL). A deferral must identify the specific defect, the operational limitation it imposes, and the rectification date, and must be certified by a person authorised under the maintenance rules.
• The entry does not describe the defect I found. “Cabin heat weak” is a performance complaint. A 20 mm crack in the shroud with soot staining is a different, physical defect - one that allows exhaust gas, including carbon monoxide, into the cabin heat supply. A generic “monitor” sign-off cannot be stretched to cover new damage discovered later.
• A current maintenance release is not a warranty. It certifies the aircraft's condition at the time it was issued and does not override a known unserviceability found since.
• The PIC owns the airworthiness decision for the flight. Even with valid paperwork, I must be satisfied the aircraft is in a condition for safe flight. Knowing what I know, it is not - CO exposure in flight is insidious, and two passengers would have no way to detect it before symptoms set in.

So the entry is irrelevant to this defect, and I have no authority to defer it myself.

Options

1. Fly the passengers as booked. Rejected: I would be flying an aircraft I know to be unairworthy, with a known CO pathway into the cabin, over rising terrain in cold air when the cabin heat would be in use.
2. Fly it empty to base. Not automatically lawful. Without a certification by an authorised person, an empty flight is still a flight of an unairworthy aircraft. A ferry would need the defect rectified, or the system made safe and certified (for example, the cabin heat supply disconnected and blanked), or a special flight permit from the CAA.
3. Get a LAME to the strip. Realistically slow and expensive at a gravel strip 90 nm from base, but it is the clean solution if the aircraft must move.
4. Leave the aircraft and move the passengers commercially / by road. This is the option that protects everyone except the schedule.

My choice: cancel the flight, arrange surface or alternative transport for the passengers, and leave the aircraft until an authorised person has inspected it. I would phone the LAME and the operator with the specific finding and photographs, and ask whether the heat system can be made safe and certified for a VFR ferry with no passengers - but I would not depart before that certification exists in writing. Document the decision, the time, and who said what in the defect log and the operator's safety reporting system.

Obligations

• The pilot in command is responsible for the safe operation of the flight and for accepting the aircraft. An operator or dispatcher cannot direct a pilot to fly an aircraft the pilot considers unairworthy, and compliance with a commercial schedule is not a defence.
• I must not make an entry in the defect log that minimises or misdescribes the defect, and I must not certify anything I am not authorised to certify.
• There is a reporting dimension: a defective aircraft plus commercial pressure is a safety issue for the operator's system, not just for today's flight.

How I handle it

1. State the finding factually and in writing: crack size, location, soot, the CO risk, and that I am not departing.
2. Ask the dispatcher to put any direction to fly in writing - that usually ends the conversation and creates the record if it does not.
3. Route it into the operator's safety management system as a hazard/occurrence, and tell the chief pilot or safety manager, not just the dispatcher.
4. If the pressure continues or the aircraft is dispatched with another pilot, report it to the CAA. The consequences of a CO incident sit with the pilot who flew it; the consequences of hiding it sit with everyone.

The test is simple: would I be comfortable explaining this decision, and the defect, to an investigator?