I'm flying out of a small private coastal airfield in California that has a variety of obstructions including nearby trees and hills to the North and East of it, and am trying to understand the legal minimums for IFR departure. There are no other nearby airports or airspaces.

When I call center on the phone they'll give me a clearance "climb and maintain seven thousand, contact center on..." and the release time and void time, but I'm not clear on the legal visibility and cloud clearance minimums for the climb-out and up to the cleared altitude. Must I remain clear of clouds while in Golf? What about upon entering Echo during the climb, but before reaching the assigned altitude?

I'd generally file and be cleared direct (which would be East), but there is terrain to the East so the local process whether VFR or not would be to depart the NorthWest facing runway, then at the end of the runway, turn left towards the ocean, and then continue turning left to on course direct.

Thanks for any legal IFR insights.


3 Answers 3


Two things are at play here, when your IFR clearance takes effect and when the FAA assumes responsibility for your terrain and obstruction clearance.

If your clearance is "Cleared to XYZ as filed, climb and maintain seven thousand" without any further qualifiers, then you are cleared IFR. Full stop, end of story, that is an IFR clearance. In order to depart into Class E you also need to obtain an IFR release, but assuming you have both the clearance and the release you are perfectly legal to go blasting off from the airport, even in IMC, in fact even in 0/0 conditions (at least under Part 91 rules).

ATC is allowed to issue IFR clearances that pass through uncontrolled airspace (see, e.g., JO 7110.65 4–3–2b1, "Specify the destination airport [as the clearance limit] when practicable, even though it is outside controlled airspace.") Once you have your IFR release ATC will restrict IFR departures out of and arrivals in to your airport—although it is possible another aircraft may be operating IFR without a clearance, unless there is a Class E surface area. ATC cannot and will not guarantee IFR traffic separation in uncontrolled airspace, even if your clearance takes you through such airspace.

To sum it up: Provided you are properly certificated and current and everything else, you are permitted to fly IFR and also to enter IMC in Class G airspace immediately upon departure, whether or not you have received an IFR clearance. In order to fly IFR in Class E airspace (whether IMC or VMC) you need to receive a clearance, which you have in fact received. Everything about your scenario is perfectly legal as far as that goes.

As for terrain and obstruction clearance, if and only if your airport has an official Instrument Approach Procedure, then you can look it up in the Terminal Procedures booklet and see what (Obstacle) Departure Procedures it has. Each runway will have an (O)DP listed, or it will be listed as "N/A" (not authorized) for some reason. In the absence of either one, the standard departure procedure applies: cross the departure end of the runway at least 35' AGL, then continue to 400' AGL before starting a turn, and then continue climb at a rate of 200' per nautical mile or greater up to the minimum IFR altitude.

If your airport does not have any official IAP, then nobody has surveyed it to see what, if any, (O)DP is necessary. Instead you are the final authority as to whether a departure into IMC is safe, and what sort of procedure you would need to fly in order to ensure obstacle clearance. See this question already linked by quietflyer and my answer to it for further discussion.

ATC's rules do not distinguish between a Class G airspace that has been surveyed for instrument departures and one that has not. The phraseology should be the same in either case. It is entirely the pilot's responsibility to know the difference and how it affects your ability to safely depart into IMC.

Once they grant your IFR release ATC will be "blocking" the airspace in the immediate vicinity of the airport up to the initial altitude in your clearance. This means they are protecting that whole area so when you pop up they don't have an immediate loss of separation with another IFR aircraft nearby. This also means you have a little bit of wiggle room to maneuver before turning directly East in accordance with your clearance, but telling them what your plan is would probably be appreciated.

  • $\begingroup$ Note: This situation is a little bit muddied because controlled airspace extends so low in so much of the country. There are stories of pilots in past decades flying IFR, and IMC, on cross-country journeys entirely in Class G and without a clearance—legally. Today it would be extremely difficult if not impossible to comply with minimum IFR altitude rules while remaining in Class G. This also means that ATC de facto does provide separation to IFR aircraft as they land and depart Class G airports, even though the letter of the law means such separation is not guaranteed to be complete. $\endgroup$
    – randomhead
    Commented Dec 8, 2023 at 16:42
  • $\begingroup$ This is probably among the top 10 answers I've seen on Aviation SE. Personally though, I have always struggled with the concept of IFR without a clearance in G. It seems that violates the "R" in IFR. That you are more accurately described as flying in IMC in the absence of a requirement to operate under IFR. Or is there an actual "rule" under IFR that allows this? $\endgroup$ Commented Dec 8, 2023 at 22:28
  • 1
    $\begingroup$ @Michael I don't think there's a specific "rule" which allows IFR in G; rather there is a rule which prohibits IFR in E without a clearance (91.173). The FARs do explicitly account for the possibility of IFR in G, eg 91.179(b) "each person operating an aircraft under IFR in level cruising flight in uncontrolled airspace shall maintain an appropriate altitude as follows..." Other IFR "rules" are written as airspace-agnostic include 91.167, 91.171, 91.177, 91.179, etc. $\endgroup$
    – randomhead
    Commented Dec 9, 2023 at 0:10
  • $\begingroup$ In accordance with ICAO Annex 11 Appendix 4, IFR flights in Class F/G are not subject to an ATC clearance. No rule requires a clearance in order to fly under IFR in such airspace, just like there is no rule requiring a clearance in order to fly VFR in Class E. $\endgroup$
    – randomhead
    Commented Dec 9, 2023 at 0:14
  • $\begingroup$ Thanks. I'm pondering a new question... $\endgroup$ Commented Dec 9, 2023 at 1:17

There are no legal minimums, assuming you are operating under part 91. If you want to take off under 0-0 conditions, it might not be prudent but it's legal. You're responsible for your own traffic separation and obstacle avoidance in class G airspace. Once you enter class E airspace your route is given non-radar traffic separation until you get into radio contact.

Traffic separation is unlikely to be a problem in IMC. Prolonged legal IFR flight in class G is not possible in California so the traffic separation you are provided in class E essentially protects your departure as well. It's not really possible to protect class E without essentially protecting class G by default.

Obstacles are a problem. To be safe it may be wise to only depart when you can avoid all the obstacles visually. Making your own pseudo-ODP is legal but make 100% sure you know what you're doing and that it provides accpetable clearance regardless of weather conditions. Don't zoom in too close- you should go the extra mile and make sure your flight path will be clear in any weather conditions you'd fly in all the way up to the OROCA.


I assume you are referring to a part 91 operation.

  • I am surprised about the clearance you got, are you sure you are not missing a part that says "upon entering controlled airspace, this-and-that"? ATC is not allowed to clear any aircraft into G. It is uncontrolled airspace, and they don't provide separation in G, the main task of ATC for IFR. The clearance they give you may cause you to fly through G, but you are on your own for that part.
  • The E part should be clear, you have a clearance for the controlled airspace part, you can fly in 0 vis. The tricky part is only the G part.
  • My flight instructor summarized the question of whether or not to violate vis minimums in G as "legalized scud-running". Realize that scud-running is still clear out of clouds. Flying in the clouds is not scud-running anymore! You are in the clag!
  • you can fly in G clear of clouds, VFR and IFR. You can not fly in 0 vis, VFR or IFR.
  • Realize that 0 vis is not just "in the clouds". It also includes dense fog. You can be outside of the clouds and can still be in IMC, for example when in dense fog. Conceivably heavy rain can give you 0 vis. Conceivably heavy rain makes it impossible for you to look out the windshield because all you see is water. That too is instrument meteorological condition! You are in IMC whenever you can't see anything outside and need to fly on instruments, no matter the reason(s) for that. Therefore you should really look at this as IMC, not just "clear of clouds". In the clouds is sufficient for "no", clear of clouds is not sufficient for "yes". Clear of clouds would be one of several necessary conditions for "yes".
  • you can only fly in IMC, regardless of airspace, if you have a clearance. ATC does not give a clearance for G. That answers your "Must I remain clear of clouds while in Golf" part, which I think is the center of your question.
  • I think we can also approach this with another purely logical argument. Jurists like hypotheticals, and I think this is another way to see this. If, hypothetically, flying in the clouds in G were legal, then two planes could be in the same cloud under the same flight rules, and don't see, hear, or know of each other (possibly not on freq, possibly no xpndr, possibly no ADSB, these are simply not required in G). That alone cannot be allowed (two in the same cloud not knowing of each other), therefore flight through the clouds in G is illegal. At the very least it would be careless / reckless.

I think that should cover the legalities, which is what you have asked for. My recommendation (although you didn't ask for it):

  • Already flying clear of clouds under basic VMC in G is playing Russian roulette, so I wouldn't do it, a) for safety reasons, and b) it may also be construed as careless or reckless, 91.13. Someone else may be doing the same thing and you don't see, hear, or know of each other, and the other guy may be "just around the corner" of that cloud in G, legally there, just like you, and kaboom. I'd fly close to the clouds only in positively controlled airspace, and E and G are not positively controlled, G is even uncontrolled.
  • There are reasons commercial operations are not allowed in G under IFR. And you'll remember from back when you did your CPL that pilots were encouraged to embrace part 135 standards even for part 91 flights. That alone is a no-no for me for many scenarios that would be legal under part 91. If you're allowed to do it, someone else is allowed to do it, and kaboom. That's why ATC will never clear you into or though G. There are several other things you are allowed under 91 you are not allowed under 135 or 121, for example taking off in 0-0. That means you would be allowed to take off on an airport that you would not be allowed to return to if you developed engine problems immediately after take-off. Whatchagonna do now? Or you don't need a functioning landing light under part 91. But is that smart? Bottom line: if you can't do it under 135, don't do it under 91. Remember: the life you save may be your own. Life is precious, especially when you fly a Mooney :) Think about all the many Mooney hours you can still have when you don't mess with clouds in G.
  • 2
    $\begingroup$ If you are IFR, you can legally fly in 0 vis even in class G. Whether this is prudent is a different question. $\endgroup$
    – Chris
    Commented Dec 8, 2023 at 5:54
  • 2
    $\begingroup$ Several things are incorrect about this answer... ATC can and will issue an IFR clearance both into and out of Class G airspace. And you do not require an IFR clearance to fly under Instrument Flight Rules (including IMC) in uncontrolled (Class G/F) airspace. $\endgroup$
    – randomhead
    Commented Dec 8, 2023 at 5:55

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