FAA
Aviation Safety
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General Aviation
Joint Steering Committee
Safety Enhancement Topic
Mountain Flying
Flying over mountains can offer beautiful scenery and views you just can’t get from the ground.
Whether it’s the Rockies, the Appalachians, or the Alps, mountain flying is often an unforgettable experience.
However, keep in mind that mountain flying also involves more risks than flying over the flatlands.
Mountain Weather
Mountain weather can be a challenge for
any pilot, especially those without a lot of
experience. The Colorado Pilots Association has
these weather minimums recommendations for
inexperienced pilots.
Maximum Winds aloft at 9,000 and 12,000 feet
less than 25 knots. Above 25 knots, turbulence,
updrafts, and downdrafts may exceed aircraft
limitations.
Ceiling at least 2,000 feet above all ridges and
passes along the route. This will help reduce the
exposure to the most hazardous turbulence in
most cases. The ceiling minimum should be
increased as the wind speed increases.
Visibility of at least 10 miles. Good visibility, well
above the basic VFR requirements, is needed since
you will generally be using pilotage for navigating.
GPS is an excellent tool, but there are times when
picking out a particular pass or valley will need to
be done visually. Good visibility is the only way to
be able to do that safely.
Be aware of mountain waves. During a mountain
wave event, there are strong up and down drafts
downwind from the ridges. The downdrafts in even
moderate mountain waves exceed 1,000 feet per
minute, making it difficult or impossible to cross
the ridge. Rotors are caused by the wind shear and
rotating moment underneath the crest of a
mountain wave. The rotors will cause severe or
greater turbulence and must be avoided.
Density Altitude
Failure to take density altitude into
consideration has led many pilots into situations
their aircraft couldn’t handle. It is imperative that
you understand how your aircraft performance is
affected by density altitude. Even in the early
evening, density altitude can be quite high and can
present problems if you are not properly trained
and prepared. Keep in mind the following:
True Airspeed increases. True Airspeed is
approximately 2% higher than Indicated Airspeed
for every thousand feet of altitude
AFS-850 17_04
Power decreases. Normally aspirated engines put
out less horsepower than at sea level (3% power
loss per thousand feet).
Leaning for take off. At sea level or the low levels
of the Midwest, takeoffs with full rich mixture are
required. However, at higher density altitudes,
even those found at airports along the Front
Range of the Rockies from New Mexico to
Wyoming, leaning for takeoff is the only way to
get the expected performance from a normally
aspirated engine.
Planning Tools
Planning a mountain flight involves finding
points in space, not predefined intersections. You
are looking for terrain features, such as passes and
drainages. Using GPS waypoints in conjunction with
an electronic app on your tablet or smartphone, is a
good way to maintain situational awareness and
avoid getting lost in unfamiliar terrain.
Some states produce tools to help pilots
navigate their mountains safely. One example
is produced by the Colorado Aeronautical
Division and shows all of the Automated
Weather Observing Systems (AWOS) locations in
the state, including those on mountain ridges.
Webcams are also useful for a real time look at
the weather along your route. Airportview.net
is one place to go for cameras located at
airports. Most state departments of
transportation also have webcams that will give
you a real-time look weather in places you may
be operating.
www.FAASafety.gov Produced by FAA Safety Briefing | Download at 1.usa.gov/SPANS
Many of us are now viewing the radar image
on our iPad apps while in flight. However, radar
and mountains don’t mix very well. For example,
the Denver NEXRAD system can’t see anything
below about FL230 over the central part of the
state. You may not be seeing the complete picture
because of these limitations.
What Gets Pilots in Trouble?
Mountainous terrain can be hazardous for
GA pilots. Here are some of the ways pilots get in
trouble in the mountains.
Picking the wrong route has claimed many pilots
who didn’t have local knowledge of issues that
might be associated with some passes.
Wishful Thinking. Hoping that bad weather will
suddenly get better when we need it to has
trapped many pilots. Consider landing or turning
around if the weather does not cooperate.
Poor Planning. Before descending into a
mountain airport, look at what your options are
for go-arounds and takeoff routes.
Box Canyon. Never fly up a canyon that you
haven’t already flown down so that you know if
there is room to turn around. NEVER try to out
climb the terrain in ANY airplane.
Resources
Pilot’s Handbook of Aeronautical Knowledge,
Chapter 11: Aircraft Performance
http://1.usa.gov/2nBxvNT
NTSB Safety Alert: Mastering Mountain Flying
http://1.usa.gov/2p2lot1
Colorado Pilots Association
www.coloradopilots.org
“Rocky Mountain High: The Zen of Mountain Flying,” FAA
Safety Briefing, May/June 2012
https://go.usa.gov/xXBZq