ADS-B Failure in Class C Airspace
You are the pilot-in-command of a Part 91 IFR flight from Napier (NZNR) to Auckland (NZAA) in a Piper PA-32R, cruising at FL110. About 25 nm south of Hamilton, the transponder/ADS-B unit fails completely: you have no Mode A/C or ADS-B replies, but your VHF radios are working. You are in Class C controlled airspace, in IMC, and Auckland Control has just cleared you to descend to FL90. The aircraft has no second transponder and no exemption. Auckland’s weather is forecast fine, but there is known IFR and VFR traffic in the area. You have 90 minutes of fuel. Your clearance limit is Auckland. You must decide what to tell ATC, whether you can continue, and what you will do if ATC cannot provide separation.
1. What are your immediate obligations and options when the transponder/ADS-B fails in controlled airspace?
Read the worked answer
Tell ATC immediately: for example, “Auckland Control, [callsign], transponder and ADS-B failure, request instructions.” Maintain the last assigned altitude and route until instructed otherwise.
In New Zealand controlled airspace, ADS-B is mandated, but ATC can authorise continuation after an equipment failure. Your obligations are to inform ATC, follow its instructions, and not remain in controlled airspace without a clearance. Because you are in IMC, you cannot simply cancel IFR and proceed VFR.
2. ATC asks whether you can maintain FL90 and proceed to Auckland. What factors determine whether you accept?
Read the worked answer
Consider:
- whether ATC can provide separation without transponder or ADS-B replies, including procedural separation and known traffic;
- your fuel endurance and the weather at Auckland and any diversion aerodrome;
- whether an alternative route outside controlled airspace is available in VMC;
- the aircraft’s remaining equipment and your workload.
If ATC can separate you, continuing may be the safest option. If it cannot, you must be prepared to divert or leave controlled airspace only when it is safe and legal to do so.
3. If ATC instructs you to leave controlled airspace, what should you consider?
Read the worked answer
Clarify exactly what is meant: leaving controlled airspace is not the same as cancelling IFR. In IMC you cannot cancel IFR unless you are in VMC and can maintain terrain clearance. Ask for an alternative clearance or a diversion. If no safe option exists, declare an urgency or emergency and request priority. Do not descend into cloud or terrain simply to comply with a route instruction.