Mountain Flying

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					Mountain Flying
        By virtue of learning to fly at Selkirk College you will be much more familiar with
mountain flying and its joys and hazards than pilots trained at almost any other school in the
world. All your cross-countries will be mountain flights and of course your local flights will be
in the mountains too.

        Without doubt mountain flying is challenging, the main factor being the weather,
combined with the fact that safe operation requires considerably more altitude than in the
flatlands. There are some advantages to the mountains for example they make it much easier to
identify checkpoints when navigating. All in all mountain flying, like any type of flying, is as
safe as you make it. The purpose of this article is to help you make it as safe as possible.

Minimum Safe VFR Altitude (in the mountains)
        Depending on where you learned to fly you may be in the habit of flying at altitudes little
more than circuit altitude at considerable distances from the airport. Many students in the lower
mainland for instance think nothing of descending to circuit altitude in the practice area and then
flying 10 or even 20 miles at that altitude back to the airport. You have quite likely also done
practice diversion exercises at 500 agl. In the mountains you MUST not do either of these things.

        In flatter parts of the world it is pretty easy to specify a ground level. The defining
characteristic of mountains, as opposed to hills, from an aviation perspective is whether or not
you can fly in the valleys. In the mountains you CAN fly in the valleys, but sometimes you
don’t. Therefore there are two distinct circumstances to mountain flying and you must know
which one applies at a given moment. You may fly “in a valley”, or you may be “crossing a
ridge.” All mountain flying can be divided into these two categories. A given flight may switch
back and forth between these circumstances many times, but you are always doing one or the
other of these.

       When flying in a valley experienced mountain pilots establish minimum safe altitudes for
each particular VFR valley route. In what follows we will discuss several common VFR routes
and the minimum altitudes for each.

         When crossing ridges experienced mountain pilots agree that when wind conditions are
ideal the minimum safe altitude is 1,000’ agl above the ridge tops. When the wind speed rises to
more than 20 knots the minimum rises to 2,000’ agl. There is a specific technique for crossing a
ridge safely. If you employ the technique and develop some experience in judging where the
downdrafts are going to be you may sometimes be able to fly lower safely. We will discuss ridge
crossing below.

        Most mountain airports are in the bottom of valleys, like Castlegar (or Kelowna,
Penticton, Kamloops, Cranbrook, etc.) The only way to approach these airports is along the
“corridor” created by the valley. If you are arriving from other directions you must either
maintain ridge-crossing altitude (see above) until over the airport or plan your arrival so that you
intercept the valley, then descend to the airport. When you do start your descent you should
avoid flying for extended periods of time at low altitude. There are fewer good off airport
landing sites in the rugged mountainous terrain, so it is prudent to plan your descent so that you
reach circuit altitude just prior to reaching the circuit. If you find yourself leveling off at circuit
altitude several miles before the airport you are flying too low.

Mountain Cross-countries
         While you are at Selkirk College you will be sent on a number of VFR cross-country
flights. You can find the details in the AVIA 100 and AVIA 200 sections of this manual.

         The instructors tend to describe these trips as either “valley trips”, or “DR trips.” A valley
trip is one in which you fly along a valley with very few if any ridge crossings. It is a type of
VFR cross-country unique to the mountains. We discuss it extensively below. A “DR trip” is a
dead reckoning trip, i.e. one in which you fly directly from one location to another. This is the
only type of navigation that students at most flight schools will experience. In the mountains any
DR trip will necessarily involve crossing ridges. For example when you fly to Swift Current you
will cross the Rocky Mountains, the biggest ridge in North America.

        A DR cross-country over the mountains is no big deal when the winds are light and the
ceilings high. When you are more than 2,000’ above all the ridges then flying around B.C. is no
different than flying across Saskatchewan. The challenge is in the fact that at any time the ceiling
could drop and you might have to descend to within 2,000’ of the ridges, or even drop right
down into a valley and convert to VFR valley-flying techniques. When this happens your
piloting skills will be challenged.

       While you are a student at Selkirk College we will take great care not to send you on DR
cross-countries when there is a significant probability that they will turn into VFR valley flights.
Besides the obvious safety consideration the VFR route usually takes longer, and that means it
costs more. Even though we try to avoid it, it is probable that you will have to switch between
DR ridge crossing and VFR valley techniques a few times during your flying at Selkirk.
Depending on the type of job you get after graduation this sort of thing could become a regular,
almost daily, occurrence for you.

       As you fly around B.C. you should be keeping track in your mind of whether you are in
“valley mode” or “ridge-crossing mode”. These are as distinct as VFR and IFR. We will now
discuss each.

Ridge Crossing Technique
                                                                 A ridge is a line of mountains that
                                                          connect to each other like links in a chain.
                                                          Mountain chains are also known as
                                                          mountain ranges. And some individual
                                                          mountains have names.

        The tops of the mountains are called peaks. The lower points, where two mountains
touch, are called a passes. Usually highways cross ridges at passes, and when the ceiling is too
low to fly over the peaks aviators cross there too (we will discuss that more as we go along).
       Most ridges have names; for example just north of Castlegar is the Valhalla range, just to
the west are the Rossland and Christina ranges, and just east of us are the Bonnington and
Selkirk ranges (for which the college is named).

                                                       In B.C. almost all the ranges run
                                               north and south; consequently there are
                                               extended north south valleys between the
                                               ranges. You can fly some of these valleys
                                               for many miles. The Columbia river
                                               (Arrow Lakes) is one such valley. The
                                               famous “Rocky Mountain Trench” is

        Erosion has created some east west valleys also, although most of those valleys are quite
short (the Kootenay River from Crawford Bay to Castlegar for example). Sometimes fairly low
passes join these valleys. Remember that when you fly over a pass you are actually crossing a
ridge, not flying a valley. For example the Blueberry Paulson pass connects the Kootenay River
valley to the Grand Forks valley, crossing the Rossland mountain range (see your Calgary and
Vancouver VNCs).

        The main hazard in crossing a ridge is either encountering a downdraft of such force that
the airplane is pushed down into the ground, or encountering terrain that rises so steeply that the
airplane cannot out climb it. The rising terrain hazard is most common when attempting to fly
through a pass. Downdrafts are the main hazard when crossing ridges above peak elevation. We
will now discuss these two situations in detail.

        The easiest situation to make general statements about is when the weather is good
enough to fly above the top of the peaks. In this case the pilot does not need to “slip through a
pass” to cross a ridge. Instead s/he simply flies directly enroute, just like a flatlander.

                                                         The picture to the left shows the
                                                 situation where the pilot is approaching a
                                                 ridge, intending to fly across it.

                                                          If there is no wind there will be
                                                 little danger. 1,000’ is recommended as the
                                                 minimum altitude because there is almost
                                                 always some wind at altitude.

But if the wind is stronger than 20 knots then a substantial downdraft will form on the lee
(downwind) side of the ridge. The downdraft could be well over 1,000 feet per minute. Of course
such strong downdrafts don’t always form, but you don’t want to turn your life into a game of
Russian roulette, so the first rule when crossing a ridge on a windy day is to stay 2,000’ above
the altitude of the peaks. If you can do that you are pretty safe except when mountain waves
form. We will get back to mountain waves in a minute; first let’s deal with the situation where
you are unable, due to ceiling or airplane performance, to fly 2,000’ above the ridge.
                                                        If you must cross a ridge at less
                                                than 2,000’ the safest way is to fly a path
                                                like the one shown to the left.

                                                        As you approach the ridge turn so
                                                that you fly across at a 45 angle. That
                                                way, if you encounter a downdraft you can
                                                quickly turn away from the ridge, back to
                                                the valley where you have lots of terrain
                                                clearance (see picture for “escape route”).

Once you reach the center of the ridge turn 90 to the ridge to get away from it as quickly as
possible. Make sure you understand and follow this procedure anytime you are crossing a ridge
at less than 2,000’ above the peaks.

         Crossing a ridge via a pass presents a whole different set of problems. Downdrafts may
still be a problem, but even on calm days you may find that the valley leading to the pass slopes
so steeply that you can’t safely out climb it. The results can be disastrous.

                                                        In the picture to the left an airplane
                                                is climbing up a sloping valley that leads to
                                                a pass. You can see that the clouds are well
                                                below the height of the peaks, one of which
                                                is shown in the background. For clarity the
                                                clouds obscuring the peak have been left
                                                out of the picture.

If the valley leading to the pass slopes at less than 200 feet per nautical mile most airplanes will
be able to out climb it.
                                                          But many valleys slope more
                                                  steeply; in that case the pilot should
                                                  establish a minimum altitude at which it is
                                                  safe to begin the flight up the valley toward
                                                  the pass (see picture to left). Some advice
                                                  on minimum altitudes when approaching
                                                  specific passes is provided below,
                                                  additional advice can be found in the
                                                  publication Aviation Weather Hazards of
                                                  British Columbia and the Yukon, copies of
                                                  which are in the College library.
An important rule for safe mountain flying is to respect the minimum altitude for entrance to a
sloping valley and turn around if the ceiling is below that. Doing so will avoid the need to turn
around later, close to the ground.

       Sometimes the clouds follow the slope of a valley, as in the diagram above, but not
always. Anytime you are approaching a pass you have to be prepared for the possibility of it
being shrouded in cloud necessitating a turn around. We discuss the technique for turning around

         When flying up a sloping valley it is easy to lose track of airspeed and get too slow. This
is particularly so when visibility is poor, as it often is. The pilot must monitor the airspeed
regularly. If the airspeed is allowed to decay while the ground rises up below, there comes a
point when it is no longer possible to turn around safely. A good mountain pilot will never let
things get that far (the procedure for turning around in a mountain valley is discussed below).

                                                        A very insidious situation is
                                                depicted in the picture to the left. An
                                                airplane has crossed a pass and is
                                                descending along a sloping valley in which
                                                the ceiling is getting lower and lower
                                                (closer to the ground).

                                                        We can see that a few miles ahead
                                                this pilot is going to have to turn around –
                                                but s/he doesn’t know that yet.

When the airplane finally turns around will it be able to climb back up the valley to the pass? If
not then this pilot is making a big mistake – and it may be his/her last. The rule in mountain
flying is to never descend down a valley that you can’t turn around and climb back up. If you are
descending down a steeply sloping valley then you must have sufficient climb performance so
that if you turn around you can climb back to the pass. In a steep valley with a low performance
airplane (like a C-172) that means cutting off the descent at a minimum altitude, just as described
above regarding minimum altitude to enter a valley approaching a pass. It is very easy to be
drawn into a mistake in such situations as you may feel you have enough ceiling to continue
safely. If you actually make it through (i.e. don’t wind up turning around) you may never realize
you risked your life, but if you do have to turn around and then realize you are too low to get
back up the slope you will get that sinking feeling in your stomach that tells you that you have
made a big mistake. Note: Two examples of such valleys are descending from Nancy Green
Lake to CYCG along highway 3, and descending from Manning Park toward Hope Slide along
highway 3 (remember that these two “valleys” are really passes that cross ridges).

Valley Flying
        By valley flying we mean specifically valleys that have minimal or no slope to them such
as river valleys. In B.C. most of these valleys run north and south – the east/west valleys being
mostly short or consisting of sloping valleys traversing passes, as already discussed above.
        Flying in a valley with a moderate ceiling and good visibility is no big deal. In such cases
your primary concern is navigation. If you don’t know the route well it is easy to branch off into
the wrong valley and get lost. To prevent mistakes (getting lost) you should keep your pencil or
finger on the map recording where you are in the valley, and use your watch to keep track of
distance covered and remaining. Don’t forget that you won’t be able to see the mountain peaks,
so you must identify your position based on features visible in the bottom of the valley. If there
are towns, highways, railways or other prominent features you will have little trouble. If the
valley is featureless it will take a lot more effort. Your fancy GPS will be of minimal assistance;
you need good old-fashioned map reading skills.

        When the ceiling or visibility starts to deteriorate valley flying becomes trickier. We need
rules and limits to guide our decision-making and keep us safe. We turn to the task of developing
those rules next.

        Normal procedure in valley flying is to stay well to the right hand side of the valley. By
regulation (CAR 602.34(2) if you are within 3,000’ agl you are not obligated to maintain the
cruising altitude according to the usual cruising altitude orders. On a valley flight you should fly
as high as the weather permits, which in most cases means 500’ below the ceiling (or just clear
of cloud if below 1,000’ agl (read CAR 602.34(2)). By flying on the right-hand side of the valley
you will avoid any airplanes flying in the opposite direction, just like cars passing on the
highway. There are some exceptions to the right-hand rule and those will be explained as we
continue our discussion of mountain flying.

Turning Around in a Mountain Valley
        You may recall from your aerodynamics course that in theory the minimum radius of turn
for any airplane is achieved by flying at the maneuvering speed while banked so steeply that you
experience the maximum amount of “g” the airplane is certified for. Most pilots will blackout at
four g’s, and it is almost impossible to maintain orientation in poor visibility in such an
aggressive turn – so whatever you do, don’t turn around in a valley using this technique. We
need a much safer plan.

       No pilot should ever plan to use more than a 45 bank turn in a mountain valley. At 45
of bank you will experience only 1.41 g and the stall speed will be only 1.2Vso. Therefore the
recommended thing to do is:

    1. Slow to normal (or short field) final approach speed
    2. Configure the airplane with full flap (or less if the airplane is low powered)
    3. Make a 45 bank turn

       For the C-172 the procedure means slowing to 65/70 KIAS with 20 flaps (because the
C-172 is a low powered airplane) then make a 45 bank turn.

        If you wait to the last second and try to slow from cruise speed to approach speed when
you desperately realize the need to turn around you are at great risk of making a greasy spot on
the side of a mountain. Instead you should be flying slowly any time you are in a situation where
a turn around is possible. Normally you would slow down to a speed similar to what you would
fly on downwind or base in the circuit. For example, in the C-172 we recommend 80 KIAS with
10 of flaps, in the B95 you would slow to 100KIAS with 20 flaps. At these reduced speeds you
would continue along the valley, hoping to get through, but ready to slow down the last few
knots and turn around if your hopes are dashed. (NOTE: slowing down as recommended here
corresponds to the “marginal” weather category explained next – turning around is done as soon
as the “unacceptable” category is reached. These categories are explained in the next section.)

        When the time comes to actually turn around in a valley the secret is to be calm. An
airplane can be turned around in a very small area so by far the greatest danger is that you will
lose control of the airplane. If you follow the recommendations in the next section about when to
turn around and follow the right hand rule described above you should have lots of room to make
the turn.

         To make a valley turn-around slow the airplane to normal approach speed (65/70 in the
C-172) with approach flaps (usually full flaps, but use 20 in the C-172). While you are slowing
down check your heading indicator to see what heading you are going to turn to (usually you
turn 180 , or just slightly more). Next, look over your shoulder to check for traffic and
obstructions (if you are on the right side of the valley you are going to turn left). Once you are
ready to turn fly instruments, i.e. the turn is an instrument maneuver, because in the poor
visibility you won’t be able to see the horizon. Add a small amount of power (100 to 200 rpm) to
maintain speed and concentrate on maintaining altitude and 45 bank. Roll out on the planned
heading and resume visual flight back to safety. Return to a speed and configuration appropriate
to the weather category (see below).

Minimum Recommended Weather for VFR Mountain Flying
        While it is impossible to make absolutely definitive rules regarding the lowest possible
ceiling and visibility to fly VFR in the mountains there are some solid guidelines that we can

        The first rule is that you MUST work your way up to (that really should be down to)
flying in minimum weather; the primary factor being familiarity with the route. If some old-timer
tells you that you can get through such-and-such pass with a ceiling at 5,000’ asl claiming, “I
have done it hundreds of times” then he is probably right, but it doesn’t mean you should go
through with such a low ceiling if you have never been there before.

        Another thing to keep in mind is that aviation safety is measured in units of accident rate
per 100,000 hours. So just because someone, including yourself, has done some activity 100
times without killing themselves does not make it safe. If you have 1 chance in 1,000 of killing
yourself those are NOT good odds they are terrible. If every pilot flew with such odds daily
airplanes would be raining from the sky. The bottom line is that you must not delude yourself
into thinking that just because you got away with “slipping through” once or twice that you will
continue to get away with it in the future.

        The weather guidelines suggested below are intended for use after graduation. While you
are a student higher weather standards apply. As mentioned above you must work your way
up/down to these limits, and may even be able to go beyond them on particular routes if you
develop enough familiarity with those routes. The speed and climb performance of your airplane
are major factors in establishing minimum weather as well. A very fast airplane requires much
more weather to operate safely. On routes that involve steeply sloping valleys a very powerful
airplane that can out climb the slope may safely operate with a lower ceiling than a low powered
airplane (see the advice above about approaching passes). Keep these things in mind – just
because an experienced pilot feels the weather is good enough for him to slip through in a C-180
doesn’t mean you can get through safely in a King Air.

        You should categorize weather as follows:

   1.   Excellent – no problems, no limitations
   2.   Good – no problems, but start getting weather updates and reviewing the map.
   3.   Marginal – continue, but if it gets worse divert and land
   4.   Unacceptable – divert now BEFORE the situation becomes dangerous
   5.   Dangerous – you should already be on the ground
   6.   Too late (you are now a statistic)

        Keep in mind that we are talking about flight in valleys with minimal slope. In that
situation, if the ceiling is high enough for you to maintain 1,000’ agl and the visibility is 15+ the
conditions can be classified as excellent. As long as you meet your minimum altitude criteria for
any valleys that slope up to passes you will have a pleasant flight.

        As soon as the visibility drops to between 10 and 15 miles, but still with 1,000’ agl
cruise, you should downgrade your weather assessment to good. There is no reason to change
your route and most likely all will go as planned, but if the weather gets any worse you may need
to divert so you should be PLANNING now. I.E. just make sure you know what alternate routes
are available, what alternate airports are available, and be sure to call FSS and get a weather
update for the rest of your route.

        Once the visibility drops to between 5 and 10 miles, OR if the ceiling drops so that you
are flying between 500 and 1,000’ agl the weather is marginal. Marginal weather does not
necessarily cause an experienced mountain pilot to divert (i.e. a pilot who knows the route well)
but you should SLOW DOWN - in the case of the C-172 slow to 80 KIAS and drop 10 of flaps.
In lots of cases you won’t have to divert, you might have to work around some fractus clouds, as
described later – but you definitely must begin taking each remaining mile of the trip one at a
time, i.e. you fly from each bend in the valley to the next then make a conscious decision
whether to continue or divert. A specific diversion plan must always be in your mind, and you
must establish a visibility and ceiling that you will not go below. (Don’t forget to keep track of
what is going on behind you. Don’t let weather close in behind you so that a 180 turn-around is
no longer an option.)

        If the visibility drops below 5 miles or the ceiling below 500’ agl the weather is classed
as unacceptable, and it is time to divert. Such weather is really not good weather at all – it will
be quite uncomfortable in fact – but it isn’t fatal if you stay calm. BUT, if it gets any worse it
will be fatal so divert and land somewhere safe now, before you regret it. Of course you would
divert even sooner (marginal weather) if the weather was deteriorating rapidly, it was reported as
below 5 miles (unacceptable) ahead, or you were not highly familiar with the route (remember
that the advice being dispensed here is for a licensed commercial pilot who is IFR rated and quite
familiar with mountain flying. It is also assumed that the pilot knows the route and airplane
being flown well).

        If the visibility drops to less than 2 miles in the mountains you are going to need some
luck to survive. You should already be on the ground, if you’re not then go down now. If no
airport is close by do an off-airport precautionary. There may be some specific situations where
this advice doesn’t apply – for you to recognize such a case you would need to be a highly
experienced mountain pilot and you wouldn’t be paying attention to this advice anyway.

        A debate you may find yourself facing someday in mountain flying is whether or not to
climb out of the valley and request an emergency IFR clearance. The practicality of this option
depends on several factors – but it usually isn’t a good idea. Obviously if you are flying a high
performance twin, such as a KingAir, and the valley is wide, and you can ensure yourself of a
suitable heading to avoid the valley sides during the climb, then it is a possibility. But if you are
deep in a valley in a C-172 or similar airplane then a climb to IFR altitude is definitely a last
desperation move to be executed only by a pilot who did not follow all the other advice provided

        In summary, you should consciously get into the habit of categorizing the weather, as
described above, as you fly on valley trips. Know your command responsibilities for each
category and fulfill them. If you do this you won’t get into trouble and you won’t scare yourself

Dealing With Fractus Clouds, etc.
        Sometimes when you fly a mountain valley the ceiling is smooth and the visibility is
constant below it. That makes it pretty easy to categorize as suggested above. But often there are
bits of clouds that tear off from the main cloud deck and float around in the valley – these are
called fractus clouds. There can also be isolated showers in which the prevailing visibility drops
for several miles. There can also be isolated shallow fog banks that hug one side of the valley, or
completely fill some section of the valley. When you encounter these weather phenomena you
need a plan.

         Often the fractus clouds block your vision down the valley. If they drop it below 10 miles
then you should immediately adjust your category to marginal and start planning a diversion.
However, while you are doing that you should try changing your cruising altitude. Move up a
few hundred feet, or if that isn’t possible descend a few hundred feet. Often a small change in
altitude will give you a completely different perspective on the clouds and you might be able to
upgrade your weather category back to good (if not then you haven’t lost anything by trying.) If
an altitude change doesn’t help then try moving a bit side to side in the valley - normally you
should be on the right-hand side but you can try moving to the center, or even to the left side for
a while. If you do move you need to take extra care looking for other airplanes, but it is a
reasonable experiment to see if things look better. If they do look better then scan the valley
ahead and judge as to whether or not to continue. Seldom will you need to fly the non-standard
side of the valley for more than a few minutes – if it looks like you will have to then perhaps it
would be wise to cancel the trip, especially if it is a frequently flown route where there is likely
to be opposite direction traffic.
        It is not uncommon to change altitude several times on a valley trip, in order to maintain
the highest possible visibility. It is much better to change altitude than allow flight visibility to
deteriorate due to dogged insistence on maintaining a specific altitude. Keep in mind that all the
power changes increase your fuel consumption, so you need to keep conservative track of your
remaining fuel. Also keep in mind that if you are doing this sort of thing then by definition the
weather is marginal, so you should have a specific diversion plan and cut-off weather in mind.
Don’t forget to keep track of whether you have enough fuel for your diversion plan. We will talk
about fuel reserves next.

Fuel Reserves on Mountain Valley Trips
        When planning flights in the mountains, especially east-west flights where you will be
climbing and descending over passes, remember that fuel consumption tables in the aircraft POH
are based on properly leaned mixture. Since you will be setting the mixture rich during climbs
and may leave it rich during descents your fuel consumption will be higher than on “normal”
cross-countries. Plan accordingly; we recommend increasing your planned fuel consumption by
10% (i.e. use 110% or POH fuel flow values. You should record actual fuel consumption figures
over several valley flights to determine your actual fuel flow rate before using anything lower
than this recommended value for flight planning purposes).

        CAR 602.88 states that VFR flights must carry enough fuel to reach destination plus 30
minutes reserve. This is completely inadequate fuel reserve for most mountain flights,
particularly valley mountain flights.

        One reason to carry more reserves is that mountainous areas are usually sparsely
populated, so airports are further apart. The same applies to some non-mountainous areas also,
and you should carry more reserves there too. The reason should be obvious – if you reach your
destination only to find the airport closed (perhaps due to an accident on the airfield) 30 minutes
reserve is not of much value if the next nearest airport is two hours flying time away. So, always
carry extra reserves in sparsely settled areas, especially when the destination airport has only one
runway. Some day I guarantee you will arrive at destination only to discover the runway closed –
and as we have mentioned many times you will not be remembered for the 1,000 successful
flights but for the one accident you had.

        There is another reason why extra fuel reserves are needed in the mountains and that is
that diversions are common and can often extend the length of a trip by a large amount. The
author has many times flown from CYCG to CYVR VFR in a C-172 or similar aircraft. The
record shortest trip was 1.4 hours (good tailwinds and direct flight at 8500 asl) the record long
flight was 5.0 hours. The long flight started off with a plan to fly the VFR route along highway 3.
This crosses two passes, the Rossland (known as the Blueberry Paulson) and the coast range
(known as the Allison pass, or Manning park pass). Both passes were crossed with no problem
and the airplane was within 30 minutes of destination at the Hope slide right on schedule as per
the flight plan, which called for 2.0 flight time to CYVR. Unfortunately low cloud at Hope
required a 180 turn-around. From Princeton we then tried following the Coquihalla to Hope.
Unfortunately it was necessary to turn around at the tollbooth. The third try was the charm –
from Princeton I flew to Lytton then south along the Fraser Canyon to Hope, then on to CYVR.
Note that fuel is not available in Princeton, so if 6.0 hours of fuel had not been onboard this
flight could not have been completed. Of course the airplane could have been landed in
Princeton, but it would have been stuck there until fuel was brought in by land vehicle. The air
regulations do not prohibit that, but it would be quite undesirable.

        The minimum practical requirement for fuel on a mountain flight is to have enough that if
diverting at any point along the route you can always find your way to a safe place to land.
Usually the greatest consideration must be given to the later part of the route, as that is where
your fuel reserves will be lowest. Don’t make the mistake of thinking that if you make it 75% of
the way along a route you will make it all the way. It is very common in the mountains to have to
retreat within only a few miles of destination. My personal record is making the 180 turn-around
on base leg for destination. So – it is really true that you may have to divert at any point on a trip,
and should have adequate reserves to make that diversion.

        Ideally you should carry enough fuel that you can both divert to a safe place to land and
also refuel to continue with the trip.

        The only conditions in which you should even consider reducing reserves to less than
advocated above is when the weather is excellent, as defined previously. In that case a diversion
is very unlikely and you might prudently fly with a 30-minute reserve, IF you have taken the
question of sparsely settled (few airports) into consideration.

High Density Altitude Operation
        It was mentioned earlier that most airports are in the bottom of valleys. That is quite
fortunate because it means that the airports are not at too high density-altitude. In Canada we
have far fewer really high altitude airports than in the USA; Calgary being the highest major
airport at 3,557’. The Denver airport is famous for being “one mile” above sea level (5,280’).
But the Grand Canyon airport is 6,800’, as is the West Yellowstone airport, and there are other
small airports that are even higher.

        A few years ago two pilots were on a night charter from Winnipeg to California in a
Cessna Citation jet. They had to make a night landing in Utah for fuel. The airport was at 5,200’
asl and the temperature was slightly above standard, so the density altitude was 5,500’. Neither
pilot had ever taken off at such a high density-altitude before. They looked in the POH and
discovered that above 5,000’ the POH recommends taking off with no flaps – neither pilot had
ever done that before. Never the less they taxied out for takeoff and set the flaps to zero as per
the POH. At Vr they rotated but the airplane did not leap into the air the way a jet usually does.
It was sluggish and “didn’t feel right.” They rejected the takeoff – they ran off the end of the
runway – they wrote off a multi-million dollar airplane – and luckily they survived to know
better next time.

        There was actually nothing wrong with the airplane. Any airplane, from C-172 top B-777
will feel sluggish and climb poorly at a high density-altitude.

        You may have experienced a similar sensation to the one described above if you have
flown the C-172 many times with only one or two people on board and mostly at moderate
temperatures, then one day you get a chance to fly at maximum weight, and the temperature is a
bit warmer than you are used to. When you rotated the airplane may not have lifted off, instead
the stall horn beeped and the airplane seemed to stay “stuck to the ground” for what seemed like
forever. In fact it was only a few seconds before the airplane finally staggered into the air, but it
seemed longer. You would then have noticed that the airspeed was lower than it usually is, so
you lowered the nose and finally everything settled down the way is should be, except you were
climbing at several hundred feet per minute LESS than you are used to.

         If you are taking off from a high density-altitude airport you MUST anticipate that the
airplane will be sluggish and the climb after liftoff shallower than you are used to. Be sure that
you have used the POH charts to determine that you have sufficient runway before taking off.
When you rotate do so a bit slower than you would a sea level and establish a slightly lower
pitch attitude (think about the attitude you would use in climb at the altitude in question, that is
the attitude you will need to rotate to on takeoff). Remember that if you over rotate airspeed will
remain too low and climb performance will be worse than it should be.

        While high density-altitude is most noticeable during takeoffs it is also a factor during
enroute flying in the mountains, especially with lower powered airplanes. Recall the discussions
above about how critical climb performance is when approaching a pass, or when flying through
a downdraft while crossing a ridge, and you can easily see why reduced performance due to high
density-altitude is a problem. Many mountain flying accidents have been caused by reduced
climb performance when a pilot attempted to out climb rising terrain only to discover that the
airplane was not able to climb as steeply as s/he anticipated. The problem is of course
exaggerated if the airplane is loaded heavily. Consequently your flying at Selkirk College, where
the airplane is normally well below gross weight, might give you a false sense of security for
post-graduate flying at higher weights. Keep that in mind for future mountain flights. Also
remember that density altitude is substantially affected by air temperature. Your flying at Selkirk
College is mostly done in the cooler months, but if you were flying a fire patrol over the same
terrain on a hot August day reduced climb performance due to high density altitude could
represent a trap waiting for you to fall into it – so be alert to this danger when mountain flying.

One-Way Strips
        As mentioned under the topic Precautionary Approach, many strips in British Columbia
are one-way due to high terrain on one end of the field. A photo of Crawford Bay airport can be
found on page Error! Bookmark not defined., showing the rising terrain north of the field. The
CFS advises pilots to land on runway 32 and takeoff on runway 14. You will have an opportunity
to land at this airport when you do your CPL preparatory flights in second year.

        Prior to landing at any one-way strip you must always determine your airplanes required
landing and takeoff distances WITH A TAILWIND. Decide in advance the maximum wind you
are willing, or permitted by your company SOPs, to operate with – then calculate the required
runway length with that wind applied as a tailwind. Any time you land at a one-way strip you
will either have a tailwind on landing or takeoff, so you need to know before you get there
whether or not the runway will be long enough. Be sure to remember to allow for grass or gravel
runway if applicable. (Most one-way strips are also unpaved.)

        When landing on a one-way strip there is a point on final approach where an overshoot is
not safe. Consequently you must determine early on the approach that all is well – and if it is not
overshoot early while you still have enough altitude to clear the obstruction. To equip yourself
with the best possible odds avoid “crowding” the circuit. Make the base leg reasonably wide so
you have a long final approach to get setup on the desired glidepath. DO NOT wait until short
final to slow down. On such a difficult approach it is important to establish final approach speed

         This photo shows an extremely difficult to judge runway. It is easy to misjudge the
approach to a runway like this. Use your VSI and scan ASI frequently. If you airplane has the
ability to generate an artificial glide-slope be sure to use it.
Syllabus Mountain Airports

       The photographs below are of airports you will visit during your training at Selkirk

Crawford Bay airport – looking north. The trees and power line obstruct the final approach to
runway 14. The airplane is backtracking and will do a 180 to takeoff on runway 14.
On left base for runway 14 at Golden; the airplane will make a low pass to inspect the runway
prior to landing, as per SOPs.

Fairmont airport as the airplane flies past enroute from Cranbrook to Golden. The Fairmont
airport is the alternate landing site if Invermere is not suitable or available for landing.
The above view is from above the circuit and west of Invermere. From here the pilot will
proceed to the other side of the airport (east); descend to circuit altitude; then cross midfield to
join the circuit. The pilot notes the high terrain east of the airport and that the CFS specifies right
hand circuits for runway 15.