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.

  • 1
    $\begingroup$ No 99% will NOT be on autopilot and will be taking notice of what is going on outside. Also are you asking about in IMC, VMC, or both? Because in IMC it should still be separated because no one SHOULD be flying VFR. Even in VMC though the VFR pilots AND the IFR pilots should be looking out for each other AND the IFR pilots (or VFR with advisories) ALSO have the ADDED advantage of ATC RADAR service. $\endgroup$ – p1l0t Jan 27 '14 at 17:21
  • $\begingroup$ Since I'm asking about VFR/IFR separation, I'm obviously talking about VMC conditions. The question wouldn't make sense otherwise. $\endgroup$ – Philippe Leybaert Jan 27 '14 at 17:37
  • $\begingroup$ Well now that you edited out that 99% comment.. It's probably safer than VFR because ATC is watching too. Just because they aren't the responsible for separation doesn't mean that a second set of eyes is a bad thing. Most of the time if they see something they will say something. It seems like before you were insinuating that pilots on an instrument flight plan aren't paying attention. Complacency is always dangerous, in IFR or VFR but being on an IFR flight plan doesn't degrade safety, sorry. $\endgroup$ – p1l0t Jan 27 '14 at 18:25
  • $\begingroup$ The essence of my question is this: We all know that we have to watch out for other traffic when flying VFR but whether we like it or not, cruising IFR at 12,000ft gives a false sense of security and pilots pay less attention than they should. $\endgroup$ – Philippe Leybaert Jan 27 '14 at 18:33
  • $\begingroup$ Wrong, the problem is you are still confusing VFR with VMC. What you should be saying is: "We all know that we have to watch out for other traffic when flying VMC whether we like it or not". $\endgroup$ – p1l0t Jan 27 '14 at 18:36

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 a conflict they're going to say something. A tower with radar (either local or slaved from a nearby airport) may 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.

  • 1
    $\begingroup$ Class D with no tower may not see every plane, but they certainly should know where every plane in their airspace should be! $\endgroup$ – rbp Dec 20 '14 at 19:00
  • 5
    $\begingroup$ @rbp Funny word "should" - people often confuse it with "is", but that's not always the case (with regard to both the tower knowing where aircraft are, and the aircraft being where the tower expects) :) $\endgroup$ – voretaq7 Dec 21 '14 at 5:13

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.


In class D and E airspace, there is no separation between IFR and VFR traffic.

This is not a true or correct statement. In these airspace classes, there is no requirement by ATC to provide separation between VFR and IFR traffic. There must still be separation in order for flight to be safe, therefore the responsibility to maintain this separation ultimately rests with the pilots of both aircraft.

ATC is responsible for providing IFR-IFR separation in any controlled airspace. VFR pilots, for their part, are required to "see and avoid" other traffic around them. This is half of why the VFR separation minima exists; you as a VFR pilot must have sufficient visibility in all directions to be able to spot other aircraft and maintain a safe distance from them.

IFR pilots have the same "see and avoid" responsibility when operating in VMC; if ATC instructions would cause the pilot to violate separation minima with observed traffic that ATC doesn't seem to know about, the pilot receiving the instruction must respond that he cannot do as instructed because of the observed traffic, which will include a report of its general position. This is the other half of the reason for VFR separation minima; if you're not flying under direct guidance of ATC, other traffic, IFR or VFR, must be able to see and avoid your aircraft, and therefore you have to stay far enough away from clouds that you're either not a danger to anyone travelling through the cloud or around the other side, or they can see you with enough time to maneuver to avoid you if you are.

ATC may provide separation involving VFR craft in Class D/E airspace as information and workload permit. VFR traffic, while not required to maintain contact with ATC, may still do so, reporting position and altitude (if ATC doesn't have a radar fix) and receiving traffic advisories of anything ATC does know about. This doesn't relieve the VFR pilot's responsibility to see and avoid but it can help him stay aware of the presence of nearby planes. This becomes more important near major airports in dense areas of airspace, which is why Mode C veils exist; while within the veil, aircraft in Class E can be easily seen and their altitude known, even if they aren't talking to ATC. ATC can then advise IFR traffic to maintain separation.

Obviously, in IMC, pilots can't "see and avoid", therefore VFR flight is illegal and IFR flights have to trust and follow ATC instructions unless anything they might still see or know obviously indicates otherwise.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.