Flight Training - June 2020 - 16

WEATHER

BY JILL W. TALLMAN

ASK AOPA

BY CRAIG BROWN

CLOSE ENOUGH?

A SMIDGE LESS JUST WON'T CUT IT

MAY GRAY, JUNE GLOOM

THE MURKY MARINE LAYER CAN FRUSTRATE WEST COAST PILOTS
SOUTHERN CALIFORNIA PILOTS HAVE IT ALL OVER THE REST OF US WHEN IT COMES TO

great flying weather-except during the months of May, June, and July, and sometimes
into August. That's when they must contend with a weather phenomenon known as
the marine layer.
The marine layer is fog that rolls in from the ocean, where it develops, to hang
out for an annoyingly long time on what would otherwise be a beautiful day. It's an
air mass that develops over the surface of a large body of water, in the presence of a
temperature inversion-which is usually initiated by the cooling effect of the body of
water on the surface layer of an otherwise warm air mass. The cooling air becomes
denser than the air above it and gets stuck below that air. Coastal communities will
be blanketed with advection fog until the sun is strong enough to evaporate it, hence
the colloquialism, "Burn it off." Typically marine layers have bases of 400 to 800 feet
and tops of 3,000 feet.
"The ocean is like the freon in your refrigerator in the summer," said CFII Jason
Miller, host of The Finer Points aviation podcast, who flight instructs in the San
Francisco Bay area. "When the summer hits and the state gets hot, the Valley hits 110
degrees; that heat draws all the air inland. That becomes the sea breeze effect. As the
air comes in at night, the land cools down dramatically and the air is so moist, it comes
over the cold land and turns it into this blanket of fog."
Miller said the microclimate creates excellent conditions for instrument training
and flying. During this time of year, pilots need to be mindful not to get stuck on top of
a marine layer. An instrument-rated and proficient pilot can file a pop-up IFR clearance
to land at a fogged-in airport, but that's not legal for VFR pilots, who would need to
scurry inland and land at another airport reporting VFR conditions.
If the marine layer is being particularly stubborn about moving off, a special
VFR clearance could help. Special VFR clearances permit pilots to take off or land in
controlled airspace when conditions are less than VFR. California pilots know that in
some instances, an airport may report "broken" conditions, but the weather is clear
to the east with a fog bank to the west. Bear in mind that some airports don't permit
fixed-wing aircraft to conduct SVFR operations, and if you are not familiar with the
characteristics of the marine layer, don't make flying plans-especially fuel-related
decisions-based on when you think the marine layer will dissipate.
jill.tallman@aopa.org

FLIGHT TRAINING JUNE 2020

Q: When I measure out my planned solo
cross-country flight I need to earn my
private certificate, the distance comes to
148 miles. Isn't that close enough to satisfy
the FAA requirement?
A: No, it is not. The regulation, 61.109(a)
(5)(ii), states it must be 150 nautical miles
total distance. My suggestion: Add another
leg to the trip to increase the distance. A
flight of greater distance is acceptable.
The regulations typically cite only
minimum training requirements. Anything greater is fine, but a smidge less just
won't cut it. You will likely be denied a
checkride and will then have to go back
and complete the requirements properly.
In my 33 years of flight instruction, I
have seen my share of uh ohs. A student
I inherited told me he had "dozens" of
cross-country solo hours. A quick check
of his logbook confirmed that, but his long
cross-country (more than 300 miles at the
time) showed he was three miles short.
Whoops. Guess who had to make that
five-hour flight again?
Make sure you get three hours of
night training and 10 takeoffs and landings. Almost doesn't work. Likewise, the
examiner will turn you away if you show
up with 2.9 hours of simulated instrument
time; you need at least three. If you have
80 hours of logged flight time but only
9.8 solo, guess what? The same result will
occur if you can only show two landings at
a towered airport. So, double check each
requirement, and be sure yours meets the
regulatory minimum.
For more information, contact AOPA's
Pilot Information Center at 800-872-2672
or pilotassist@aopa.org.
CRAIG BROWN is a senior aviation technical specialist in the AOPA Pilot Information Center.

Flight Training - June 2020

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