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5 Answers

Before radar contact

Asked by: 1894 views Instrument Rating

Is it possible for two aircraft to collide under the following circumstances?

Conditions are IFR,  each aircraft is departing  an uncontrolled separate  airfield,  both are going to the same initial fix,  both are given clearance to depart IFR  at the same time but ATC  has not yet made radar contact with either of them so essentially they are both flying blind.  Is such a situation possible? 

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5 Answers



  1. Ron Klutts on May 11, 2017

    Not possible. ATC will only release 1 IFR flight at a time from a non-towered airport. You get a void if not off by time after which you can’t depart. This ensures that only 1 aircraft is in the area at any given time.

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  2. John D Collins on May 12, 2017

    Not possible if both aircraft are IFR. Only one IFR operation, a departure or approach is permitted at a time at a non towered airport. You get a release for departure with a clearance void time. Once you are in radio contact with ATC and the required IFR separation is assured, the next flight can use the airport. It does not require radar contact as procedural methods can be used to separate aircraft.

    But at most non towered airports, separation from VFR aircraft is not provided and in most instances, class G airspace goes to 700 AGL. Day VFR in these circumstances only requires visibility of 1 SM and remain clear of clouds, so if the visibility is 1 mile and the ceiling is 200 feet, that is a beautiful VFR day in class G airspace.

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  3. Russ Roslewski on May 12, 2017

    I’m pretty sure Glenn is asking about two aircraft departing IFR from two _different_ (but nearby) uncontrolled airports, being cleared to the same initial fix.

    Neither of them gets in radar contact yet, but are headed toward the same fix.

    I believe he is asking about what protections are in place to prevent a collision in that situation.

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  4. R. Anderson on May 12, 2017

    I believe Ron’s answer above is accurate.

    I might add, even with a clearance void time, ATC will not allow the second aircraft to be released/depart under IFR until the first aircraft is accounted for and positive separation exists. In a non-radar environment, once the first aircraft is within controlled airspace, and, for example, has reported out of say 5000 ft, the second aircraft could be released to an assigned altitude of 4000 ft. (assuming those altitudes are available to the controller.

    Either way, the second aircraft would not be allowed to depart under an IFR clearance (along the same route) until positive separation was assured with the first aircraft.

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  5. R. Anderson on May 12, 2017

    Let me clarify my last sentence above:

    Either way, the second aircraft would not receive a clearance to enter controlled airspace under an IFR (along/over the same or conflicting route) until a positive form of separation, in my example “vertical” separation, existed from the first aircraft who is also in controlled airspace.

    This is not an uncommon scenario.

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