Yes, as long as you are not flying anywhere that having a transponder activated and pinging is required by law. According to the Experimental Aircraft Association, it’s safe and legal to fly without one outside of those perimeters. However...
If you want to fly in class A, B, or C airspace, travel at altitudes exceeding 10,000’MSL, or be anywhere in a 30-mile nautical radius of a primary airport in class B airspace, then you require both a transponder and altitude encoder AKA “Mode C”.
Your aircraft can, however, be authorized to fly without an operating transponder by Air Traffic Control in certain circumstances.
For instance, if your transponder breaks, you are legally allowed to fly to “the airport of ultimate destination, including any intermediate stops, or proceed to a place where suitable repairs can be made.”
You must request to do so “at least one hour before the proposed time” of departure in order to legally enter the airspace without a working transponder. In difficult situations, for instance, if you lose an alternator, you can also turn off Mode C in your aircraft provided you immediately alert ATC as to why.
As you can see, there are several situations in which flying without a transponder is more than just legal, it is encouraged! So long as you are sure it is necessary to turn it off, or not necessary to have it on in the first place, you’re good to go.
Can you fly IFR without a transponder?
Yes, but only if you are not breaking any air traffic laws! Having your transponder turned off is allowed in certain circumstances, particularly if the pilot is in an emergency situation, but otherwise, you need it on.
Flying under Instrument Flight Rules (IFR) as opposed to regular Visual Flight Rules (VFR) when your flight cannot be managed safely by using visual references from outside leaves you dependent on your instruments to pilot, as the name suggests.
You can legally do this without your transponder - or Mode C, as it is often referred to - provided you don’t need to enter class A, B or C airspace, travel at altitudes exceeding 10,000’MSL, or come within 30 nautical miles of an airport in class B airspace. Otherwise, you’re going to need it turned on.
However, if you’re currently in distress and need to conserve electrical energy, provided you have already alerted Air Traffic Control about your intentions then you are legally allowed to disable Mode C in these circumstances.
What airspace requires a transponder?
According to the Federal Aviation Handbook, transponders are required in the following circumstances:
- In Class A, Class B, and Class C air spaces;
- Above the ceiling and within the lateral boundaries of Class B or Class C airspace up to 10,000 feet MSL;
- Class E airspace at and above 10,000 feet MSL within the 48 contiguous states and the District of Columbia, excluding the airspace at and below 2,500 feet AGL;
- Within 30 miles of a Class B airspace primary airport, below 10,000 feet MSL (commonly referred to as the "Mode C Veil");
- For ADS-B Out: Class E airspace at and above 3,000 feet MSL over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles
It is also important to note the following exclusions to the rule:
“Transponder and ADS-B Out requirements do not apply to any aircraft that was not originally certificated with an electrical system, or that has not subsequently been certified with such a system installed, including balloons and gliders.”
Such aircraft as these may conduct operations without a transponder or ADS-B Out when operating:
- Outside any Class B or Class C airspace area;
- Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport, or 10,000 feet MSL, whichever is lower
What does Squawk 1000 mean?
Squawk 1000 is a code sent via the transponder of an aircraft, alerting Air Traffic Control to its current location.
According to the official list of transponder codes from the Federal Aviation Administration, it means different things depending on where you are located when you send it:
- In the US, Squawk 1000 is a code used solely by those piloting ADS-B aircraft to inhibit Mode 3A transmittance; it can also be used for non-discrete code assignments in accordance with FAA Order JO 7110.65, 5-2, as well as in oceanic airspace, unless another code has been assigned by Air Traffic Control
- In Canada, Squawk 1000 is a code that refers to an Instrument Flight Rules (IFR) flight below altitudes of 18,000’ when no other code has been applied
- In Europe, Squawk 1000 is a code that refers to IFR GAT flights operating in designated Mode S Airspace