How safe is IFR in class E?

Philippe Leybaert
  • How safe is IFR in class E? Philippe Leybaert

    In class D and E airspace, there is no separation between IFR and VFR traffic. However, most airspace in the United States below 18,500 feet MSL is class E airspace, which is exactly where non-pressurized aircraft cruise when flying IFR.

    My question is not about regulation (that's perfectly clear: no separation between IFR/VFR) but I'm curious to learn how safe it actually is when cruising at 10,000 feet in VMC on an IFR flight plan while in class E airspace. I'm pretty sure many pilots will be on autopilot without taking too much notice of what's happening outside but according to the regulations the pilot is still responsible for seeing and avoiding other VFR traffic.

    Are there any accident statistics on this? I have read hundreds of accident reports over the last few years and I can't remember ever seeing a report on a midair collision between IFR and VFR aircraft in class E.

  • I'm pretty sure 99% of pilots will be on autopilot without taking too much notice of what's happening outside but according to the regulations the pilot is still responsible for seeing and avoiding other VFR traffic.

    Well, shame on the pilots, then. Put down your iPads and do your job. It is "see and avoid". Perhaps they have some automation in the cockpit to help them like TIS or TCAS etc. but it is their responsibility to avoid a collision - period. And the old Mark I eyeball is frequently the only way to accomplish that task.

    To answer your question more directly, the system works pretty well. I don't have statistics but I do know that we would read a lot about it in the press if collisions happened regularly.

  • As with any flight, "It's as safe as you make it".

    The vast majority of the General Aviation fleet (piston singles) don't even have an autopilot, and the ones that do may only be single-axis units (wing levelers), so the pilot has to have some level of attention on flying the airplane.
    If we assume these are the folks flying around VFR we can also generally assume they should be looking out the window the vast majority of the time (like Skip said, "Put down your iPads and do your job.")

    Adding to that, "See and avoid" is every pilot's responsibility in VMC - whether operating under Visual Flight Rules or Instrument Flight Rules - if you can see, you are expected to avoid (and if necessary deal with ATC freaking out about you deviating from a clearance later).


    A number of other steps have been taken to enhance safety in Class D and E airspace:

    In the US FAR 91.159 prescribes specific VFR cruising altitudes, and FAR 91.179 is the IFR equivalent.
    The cruising altitudes in these regulations result in an automatic 500-foot vertical separation of VFR and IFR traffic (at least between 3,000 feet MSL and 18,000 feet MSL - which is where VFR and IFR traffic are likely to be mixing in cruise. ).

    Additionally IFR traffic is usually receiving radar separation services (there are some non-radar areas in the US, but not many). Nominally this separation is "IFR-to-IFR" in Class E airspace, but if a controller sees a VFR target squawking 1200 and behaving unpredictably they can vector IFR traffic around it.
    Similarly if a controller sees a "primary target only" (something without a transponder, and not reporting altitude information) they will often vector IFR traffic around it until they can establish what it is and what it's doing.

    Within class D airspace the level of service you'll get depends somewhat on the equipment the controllers have. A "purely visual" tower with no radar can only give traffic advisories for aircraft they can see by looking out their window, but if they see an conflict they're going to say something. A tower with radar (either local or slaved from a nearby airport) may give give VFR-to-VFR or VFR-to-IFR separation advisories based on that data as well, sometimes including advisories to aircraft inbound who are outside their airspace.

Related questions and answers
  • How safe is IFR in class E? Philippe Leybaert

    In class D and E airspace, there is no separation between IFR and VFR traffic. However, most airspace in the United States below 18,500 feet MSL is class E airspace, which is exactly where non-pressurized aircraft cruise when flying IFR. My question is not about regulation (that's perfectly clear: no separation between IFR/VFR) but I'm curious to learn how safe it actually is when cruising... can't remember ever seeing a report on a midair collision between IFR and VFR aircraft in class E.

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