Being an engineer, I like clear and easy to verify rules. Things like “don’t fly above 3.500 feet” are good. Give me an altimeter, a local pressure setting, and I can do that. Don’t fly faster than 250 knots below FL 100 ? Easy… and I’d like to fly once an aircraft able to fly more than 250 knots.
Airlaw books are full of rules and to my disappointment, many are not so easy to verify. An example ? Distance from clouds. In airspace F and G, this is easy: clear of clouds. Correction, this is easy-ish. When clear of convective clouds is easy, but with stratiform ones… They sometimes form thin layers in which the visibility is reduced, but not to zero. Where’s the limit of such a clouds ? Not to mention the second part of the rule: in sight of ground. Some clouds are so thin that one can see the ground through.
Another set of rules I dislike it about distance to clouds. 1.000 feet below, 5 or 8 kilometers laterally. Is climbing until reaching the clouds, note the altitude, and descend 1.000 feet a valid method ? I don’t think so. Evaluating distances from fluffy things in the air, with no reference is not something I’m good at.
I understand why the rules exist. The see-and-avoid principle is the base of VFR flying and this requires sufficient visibility. Speed must also be restricted to give pilots sufficient time to spot each other and take appropriate action. Visibility and clouds base height are measured at airports, making a go / no-go decision possible on base of what is legal. Note that the decision is not only about what is legal but also about personal minimums which can be more restrictive. Once in cruise, there is no possible measurement of visibility or distance to clouds. Weather reports from nearby airports can be of some help but conditions in the air and on ground can be dramatically different.
In case of incident, or accident, there is no way to measure what the visibility and ceiling were, or what the distance to clouds was at occurence time or position. Investigators will certainly check recent reports, radar and satellite pictures, but this gives a rough estimation only. The outcome of a trial depends on whether rules have been violated or not. And rules including the words “sensible” or “appropriate” are not really rules, aren’t they ?
I know lot of pilots who would launch in terrible conditions, should the rule say “aircraft shall be operated in sufficient visibility and at an appropriate distance from clouds”. I also know of others who whould call me “girly” for not flying under the same conditions…
So what do we have ? A set of formal rules defining criterions that can hardly be verified. It’s frustrating but there is no other way. What I use to do is to get weather reports from airports along the route to make the decision. If it’s a got, then I see what I get, and if I don’t feel comfortable with it, I divert to somewhere with better weather. No shame, no question, no problem.
Vincent Lambercy is a Swiss private pilot now living in Germany. He holds a private pilot certificate with single-engine, multi-engine and instrument ratings and has logged more than 430 hours of flight.
{ 3 comments… read them below or add one }
In some of those grey areas, it’s more important to understand why a rule exists than the rule itself. The bottom line is to stay safe. Most of the time a bit of good judgement and common sense will keep you safe and violation-free.
And what do you mean Vincent, you don’t carry a pocket tape-measure with you for those cloud distance requirements? My company has specific limitations on snow thickness. If it’s .25 inches, we do this, and if it’s .5 inches we do that. Now what am I supposed to do, jump out and stick a ruler in the snow before I take off? You just do the best you can and err on the side of conservatism.
Great point on the transparent clouds. I’ve been told that “if you can see through it, it isn’t a cloud” but I’ve never seen that documented anywhere. That being said, the point of cloud clearance is to avoid colliding with other airplanes, and if you can see through the cloud then there is no increased risk of collision. Legally though, it comes down to each individual FSDO’s interpretation of the rules.
This brings up a good point: if issues arise with any perceived grey area, consult your local FSDO (or European equivalent). And understand that the local interpretation may change from location to location.
Let see if I can comment
On the cloud clearance requirements, I think one of the key reasons for the requirement is for clearance between VFR and IFR traffic as the IFR traffic is coming out of the clouds. I have had this happen once so far and it is a little disconcerting to report 3 mile final on the local frequency and then pop out at ~1300 AGL with traffic near you and slightly below you. I think he was possibly legal, and he was far enough away from the airport to possibly not be listening to the frequency. If he had been a little closer to the clouds, it might have been a close call. So keep the IFR traffic in mind if you are flying close to the clouds, especially if you are in line with a long final or near a victor airway near an IFR altitude.