Day VFR -- when is it night?

[Dennis]

I know that as a Private Pilot flying as a Sport Pilot I cannot fly at night. But I am not sure how the night is defined for my flying. I assume it involves local civil twilight. My planetarium program typically shows local twilight as two hours past sunset. This is getting confusing!

EAA and other web sites offer different interpretations. So, time to bring in the big guns -- this group.

1) How late can I fly on a given day at a given lat/long?
2) What is a web site that will do the calculation for me?

I raise this questions because of late the only calm air is around sunset and sunrise.

Thanks!

Fly safely,
Dennis

[David]

I know that as a Private Pilot flying as a Sport Pilot I cannot fly at night. But I am not sure how the night is defined for my flying. I assume it involves local civil twilight. My planetarium program typically shows local twilight as two hours past sunset. This is getting confusing!

EAA and other web sites offer different interpretations. So, time to bring in the big guns -- this group.

1) How late can I fly on a given day at a given lat/long?
2) What is a web site that will do the calculation for me?

I raise this questions because of late the only calm air is around sunset and sunrise.

Thanks!

Fly safely,
Dennis

1/2 an hour before and after


The half hour before and after are called "civil twilight". A sport pilot may fly during civil twilight, but the aircraft must display navigation lights during this time. (Navigation lights must be turned on between sunset and sunrise.) A sport pilot may NOT fly at night, which is that time between the end of evening civil twilight and the beginning of morning civil twilight.


Here is a link http://aa.usno.navy.mil/data/docs/RS_OneDay.php

If you have a iPhone I use the Nav Clock app


http://www.splitrailsoft.com/srs/Home.html

[drseti]

1/2 an hour before and after

It's not always so simple. Civil twilight times vary with season, airport elevation, and latitude. WingX includes a Civil Twilight calculator - for my airport (KLHV), here are today's values:

Morning civil twilight 0906Z
Sunrise 0939Z
Sunset 0037Z
Evening civil twilight 0110Z

So you see, today at my location it's 33 minutes before and after. (Tomorrow will differ).

Under Sport Pilot rules, you may only fly between the hours of morning civil twilight and evening civil twilight. I tell my students and renters to flight-plan to take off after official sunrise, and land before sunset. The civil twilight rule gives them a safety buffer.

[David]

Paul I agree the 1/2 hour was the option on the faa test. LOL

I use that app or the web site for the exact time, but it should be a buffer as you stated

[jnmeade]

I tell my students and renters to flight-plan to take off after official sunrise, and land before sunset. The civil twilight rule gives them a safety buffer.

This sort of advice drives me crazy and I would never do it. Here's why:
1. Using this rule consistently, one forgets how to look up or calculate civil twilight or the exact rule about civil twilight. It replaces the rules with a rule of thumb. And it deprives the pilot of legal flight time.
2. It patronizes the student by giving them the impression that they aren't smart enough or mature enough to understand or apply the regs.
3. Pilots who follow this kind of rule of thumb pretty soon get confused about whether or not they can fly before sunrise or after sunset, and thus the equipment requirements, and begin to tell others "sunrise to sunset" which is wrong. It's one of the ways aviation old wives tales are started - all with good intent but ultimately confusing and misleading.
4. There should be no buffer requirement on take off - check the ephemeris and an accurate clock and off you go. Any buffer on arrival before the end of civil twilight out to be a part of flight planning and while it can be "about sundown" that shouldn't drive the plan. (oh, if you're are caught out "after dark" (between civil twilights, you'd better have 45 minutes of fuel left, not 30 and hopefully you are current at night landings if you have passengers.) I bet most of us don't plan for a buffer on arrival in most cases. We may wish to when terminating a flight near civil twilight but I'd say it should depend on weather, traffic and many other considerations, not just sunset. I will concede that if one took a friend up for a local sundown flight without doing any flight planning, then seeing the sun go below the horizon is a good time to be on final. But for a cross-country trip I'd relay on flight planning and not the sun angle.

§ 91.151 Fuel requirements for flight in VFR conditions.

(a) No person may begin a flight in an airplane under VFR conditions unless (considering wind and forecast weather conditions) there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed—

(1) During the day, to fly after that for at least 30 minutes; or

(2) At night, to fly after that for at least 45 minutes.

On one hand, train and expect pilots to know some very specific and somewhat arcane knowledge. For example, we expect them to know that the hemispheric rule depends on heading, not track or bearing. Yet, here we are willing to let the student off the hook on knowing equipment requirements and how to find civil twilight by saying in essence just avoid the question by not operating in that environment. It's like telling a person to never fly unless it's 10 and clear.

[drseti]

It's like telling a person to never fly unless it's 10 and clear.

Which is exactly my flight school's rule for primary students! Of course, before they graduate, we spend a lot of time together developing a Personal Minimums Checklist, which they tweak over time as they gain experience. What time of day to fly is a similar matter: for students, my rules apply (and they do not allow flying in those Civil Twilight periods). Of course, Jim is right that, after the checkride, each pilot has to develop personal minimums with which he or she feels comfortable (and reassess those from time to time). Yes, they need to know the civil twilight rules for the knowledge and practical tests. That doesn't necessarily mean they can't avoid problems by setting a more conservative personal buffer.

[jnmeade]

Aviation Instructor's Handbook FAA-H 8083-9A

p 2-11
Primacy
Primacy, the state of being first, often creates a strong, almost unshakable impression and underlies the reason an instructor must teach correctly the first time and the student must learn correctly the first time.

I restate my concern that by the time the student is out on his own, he has ingrained your personal standards and substituted them for the regs and his own experience.

[VL Roberts]

Nothing wrong with a flight school having procedures to ensure students stay well within the envelope.

[drseti]

underlies the reason an instructor must teach correctly the first time and the student must learn correctly the first time..

As a professional educator for 40 years, I certainly understand the law of primacy. I simply maintain that it's not incorrect to start off with standards and policies that are more conservative than the FARs. Now, starting off more lax than the regs, that would be wrong (and the law of primacy would apply). The basic rule is, never teach anything that's going to have to be unlearned. There is no reason a student will ever have to unlearn caution.

[FastEddieB]

If we're choosing sides, I'm with the professor.

[drseti]

I restate my concern that by the time the student is out on his own, he has ingrained your personal standards and substituted them for the regs and his own experience.

Your concern is noted, Jim, and I respect it. I would be more concerned if my students were automatons. Fortunately, they seem quite able to think for themselves.

[jnmeade]

Nothing wrong with a flight school having procedures to ensure students stay well within the envelope.

Yes there is.

Procedures to not exceed, yes (such as don't fly before morning civil twilight). Flying 1 minute after morning civil twilight is perfectly legal and easy to prove. If you are talking the student is not competent, then fine, teach him. But if you mean you are afraid to let the student do something that is patently and demonstrably OK, that is wrong.

Procedures to build in an arbitrary buffer such as no flying after sunset when it is legal to fly for some additional time (according to local evening civil twilight which is about 30 minutes for the sake of this discussion) are a disservice to the student for reasons I explained in a prior post.

If you are doing pattern work and you can do a circuit every 0.1 hour, quite reasonable at a quiet, non-towered airport, it is foolish to me to stop at sunset when you could do 4 more circuits or even 3 and be on the ground well before evening civil twilight. If you are flying a cross country, there may be reasons you'd like to be on the ground by sunset, but the main determinant of time should be flight planning, not looking at the sun. Of course you need alternatives which you should be implementing well before it is evening civil twilight and well before sunset. One is using flight planning enroute to verify that timing is OK or an alternate should be implemented.

To me, this kind of arbitrary exceeding of regs smacks of safe-siding it for the convenience and anxiety of the flight school and CFI and has nothing to do with a legality or safety or a good way to teach students.

It's the kind of mindset that has VFR pilots not only afraid to fly if it is not 10 and clear, but also casting aspersion on those who may think it is fine to fly when it is 5,000 scattered and 8 miles or 3,000 overcast, 7 miles, a stable air mass and trending better weather plus an airport every 10 miles. We start developing a culture of excessive caution and in doing so we form a pilot community that self-restricts itself to the point where pilots can't fly what is legal because they've never practiced.

[FastEddieB]

Jim,

Would you allow a solo student to fly in crosswinds right up to the demonstrated maximum in the POH?

Would you do so on his or her first solo?

Just curious.

[jnmeade]

Eddie, you bring up an excellent point. I don't think the two situations are at all analogous. In one case, we are talking about safe-siding a very predictable, controllable activity - for what purpose? On the other side, we are talking about the student's ability to apply a skill set. I would like to think that ideally, we would feel the student has been trained adequately to permit such a crosswind on first solo. In reality, all of us would be a bit hesitant because we probably haven't been able to train to that standard. I think it would be good if conditions permitted us to do that kind of training. Even the PTS recognizes that sometimes we don't have the conditions. Maybe as simulators get better we will be able to take all of our students to the limits under supervision and safely.

Each of us who has had kids learn to drive has felt what Paul is suggesting, but each of us probably didn't train our kids as well as we train out pilots and not as systematically.

My basic disagreement is with the setting of local standards that are more restrictive than the FAA sets when there is not a compelling safety reason. I am not disagreeing with a pilot setting his own more restrictive envelope.

In aviation, perhaps more than in any other endeavor, we see the instructor as next to god. There is a lot of "do this" "do that" and not enough explanation and the CFI, often young and inexperienced, may often not be able to give a good background understanding for the topic being taught. In other words, I think Paul is being overly cautious on this topic. If he were to say, "I've not been able to do crosswind operations in more than 10 knots with you so I will not endorse you to fly in more than 10 knot crosswinds" I would support his decision without question.

[Merlinspop]

My primary flight school had varying minima for pre- and post-solo, and local vs cross country. I can't remember the details, except that it started out very restricted, but by the time I was ready for the practical, my 'leash' was as long as the FARs allowed for PPL holders.