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If you're talking about a big puffy cumulus cloud it's pretty obvious. But from where I am right now, looking up I see grey sky from horizon to horizon. But visibility at the surface is good. All nearby metar's are reading 10SM CLR. It's just a tiny bit hazy, but I can clearly see a water tower that is 8 miles from me. But there is no defined cloud layer. It just seems that the haze gets thicker the higher you go. If there was a vfr plane up there at a few thousand feet I'm sure I could see it but I can't see any of the four airliners that FR24 shows are above me.

My question is, when there's no defined cloud layer, what is considered "cloud" and what isn't? If the minima require you to stay 500 feet below clouds, where exactly is that? With metars showing no ceiling how do you know where it is safe to fly and where there might be an ifr flight descending that can't see you?

TomMcW
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    I don't know about the FARs, but my instructor told me, "If you can see through it for a distance of 3NM (or visually down 500 ft, or visually up 1000ft), then its not a cloud; its just some moisture." – abelenky Feb 23 '17 at 22:13
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    My CFI pretty much mirrored what @abelenky 's CFI did, "if you can see through it, don't worry about it". – Ron Beyer Feb 23 '17 at 22:43
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    "That's not a cloud - that's a region of temporarily reduced visibility." – pericynthion Feb 24 '17 at 00:58

1 Answers1

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My question is, when there's no defined cloud layer, what is considered "cloud" and what isn't? If the minima require you to stay 500 feet below clouds, where exactly is that? With metars showing no ceiling how do you know where it is safe to fly and where there might be an ifr flight descending that can't see you?

The FAA defines clouds in AC-006B

A cloud is a visible aggregate of minute water droplets and/or ice particles in the atmosphere above the Earth’s surface. Fog differs from cloud only in that the base of fog is at the Earth’s surface while clouds are above the surface. Clouds are like signposts in the sky that provide information on air motion, stability, and moisture. Clouds help pilots visualize weather conditions and potential weather hazards.

However legally and practically speaking you can fly as high as you like if there are no clouds provided you can maintain situational awareness and proper cloud clearances from any adjacent clouds (including those under you). There are a few practical limits to this. First off Class A airspace starts at FL180 so you cant fly above 18,000 Ft. without being on an IFR flight plan since you cant fly VFR into class A. Further more, since you seem to be asking about small aircraft, you will more than likely be limited by your airframes maximum altitude before hitting the Class A limit. You will also need O2 onboard to fly above 12,500 ft.

The risk of a descending aircraft above you is always a concern be it VFR or IFR flying as they generally cant see below them and you cant always see above you when flying. In many cases the IFR flight will have some help from ATC who will see you on radar even if you are flying VFR and squawking 1200 on your transponder.

Dave
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  • In the US, only student pilots need to maintain sight of the ground. Once you have your PPL, you can fly over cloud cover—I do it all the time. It even has a name—VFR Over-the-Top. I don’t believe that there is a requirement to maintain visibility with the horizon for either student or PPL. – JScarry Feb 24 '17 at 00:01
  • You are correct that you can fly Over-the-Top, the horizon issue is somewhat addressed in this question Something made me think you also needed to see the ground but im looking into it now. You may in-fact be correct. However not being able to see the ground or the horizon may be considered IMC. – Dave Feb 24 '17 at 00:24
  • As long as you are in VFR conditions (§91.155 Basic VFR weather minimums.), a PPL can legally fly VFR. However, it is possible to be flying on instruments, and even log IFR time, in VFR. Imagine a moonless night above the clouds or out in the boonies. No horizon, no view of the ground. You may need to fly solely by reference to instruments. That would count as instrument time for your logbook, but you would not need to be on an IFR flight plan since you are in VFR meteorological conditions. – JScarry Feb 24 '17 at 00:53
  • The only reference to seeing the ground that I am aware of is Subpart C—Student Pilots §61.89 General limitations. (7) When the flight cannot be made with visual reference to the surface; or – JScarry Feb 24 '17 at 00:59
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    By "VFR flight conditions" you mean VMC? – DJClayworth Feb 24 '17 at 01:47
  • I do mean VMC, I can change it if need be. I did some digging and I cant find anything about the ground however it does seem that there may be some non FAA/USA regulations around this, I found some Canadian regulations that may require it but have not yet finished digging into them. – Dave Feb 24 '17 at 02:16
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    This is one of my pet peeves: When talking about the conditions (moonless night, etc), it should be important to call them either VMC or IMC. When talking about rules, it's VFR or IFR. You must be in VMC to operate under VFR rules. This should not be referred to as "VFR Conditions", because you can also operate under a different set of rules (IFR) in those same conditions (VMC). Unfortunately, even the FAR and AIM both use the term, "VFR Conditions" -- which in my opinion is a term that needs to be nixed from all literature. Too much confusion has been had by intermingling terms. – Jimmy Feb 24 '17 at 02:19
  • @Jimmy Most of the time it is clear what is meant, but you are right, it does occasionally lead to confusion. I count 15 times it is used in the AIM. It is also used in Aviation Weather Services, Aeronautical Decision Making, Instrument Flying Handbook, Risk Management, Airplane Flying Handbook, Aviation Instructors Handbook, Airplane Flying Handbook, Instrument Procedures Handbook, Pilots Handbook of Aeronautical Knowledge, and the Pilot Controller Glossary. And at least 10 times in the FARs. So I doubt that it will ever be nixed. – JScarry Feb 24 '17 at 02:47
  • @jscarry, you're right, it's a futile expectation. And my "rant" didn't add anything to this Q&A. To sorta get back on topic: you mention "logging IFR time". This is another confusing term because (afaik), you can only log "instrument" time (that portion of the flight when you are controlling solely by reference to the instruments). Conducting an IFR flight entirely in VMC means you cannot log "instrument" time, but the phrase "logging IFR time" implies that you would log the entire flight (having been under IFR rules the whole time). (which, I believe, they do in Europe - log "IFR time") – Jimmy Feb 24 '17 at 03:15
  • @Jimmy, can you not log instrument time in VMC with a proper view limiting device? – Dave Feb 24 '17 at 03:52
  • @Jimmy §61.51 Pilot logbooks. g) Logging instrument time. (1) A person may log instrument time only for that flight time when the person operates the aircraft solely by reference to instruments under actual or simulated instrument flight conditions. Note that the FAR does not say instrument flight rules, just instrument flight conditions. I don’t see that term defined, but in the context of the rule, I assume it means "as if you are flying under instrument meteorological conditions" i.e. you can’t get cues to your position or orientation from outside the cockpit. BWTHDIK – JScarry Feb 24 '17 at 15:23
  • I found the reference, there is a book called "FARs Explained" where I got my interpretation. They base it on an FAA Chief Counsel letter to Joseph Carr in 1984. I can’t find the letter, but I found a transcript of it. http://forums.jetcareers.com/threads/logging-actual-under-part-121.74365/ The relevant part is "actual instrument conditions may occur in the case you described a moonless night over the ocean with no discernible horizon, if use of the instruments is necessary to maintain adequate control over the aircraft. The determination … is somewhat subjective…" – JScarry Feb 24 '17 at 15:36
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    Thanks, @jscarry, and good reference! My comment was only on the phraseology that you used: "IFR time". My statement was that "Instrument time" is the more correct term. In the US, pilot's don't log "IFR Time", because that phrase implies any flight where they are on an IFR flight plan and under ATC control. The entire flight would be considered "IFR Time", but not necessarily "instrument time". US Pilots only log "Instrument Time" during meteorological conditions met in 61.51, no matter if they are on an IFR flight or VFR flight. (and the caveat that I believe Euro pilots do log "IFR Time") – Jimmy Feb 24 '17 at 23:59
  • @Dave yes, pilots are allowed to log "simulated instrument time" when they are using a view-limiting device in VMC and under the supervision of a safety pilot. – Jimmy Feb 25 '17 at 00:00