A primer on the fun and challenge of personal flying in mountainous terrain (video clips in original not supported)

1. Corona (Rollins) Pass, CO 11,571 msl (Charles Luce)
Mountain Flying
A Primer
© 2013 Mark J. Kolber
www.midlifeflight.com

4. Mountain Airports
Airport No. 1
• 3300’ runway at 5900' msl.
• Standard temperature: 3°C/37°F.
• 70°F = 7919 D-Alt.
• In a canyon.
• Partially blind approach.
• One way in/opposite direction
out recommended due to terrain.
• Limited go-around opportunities.
• Potential burble/downdraft on
final when crossing the river.
Airport No. 2
• 2900' runway at 4500' msl.
• Standard temperature: 6°C/43°F.
• 70°F = 6200+ D-Alt.
• On mountainside/nearby peaks.
• Uphill landing/downhill takeoff
• One way in/opposite direction
out due to terrain and slope.
• Runway illusion makes go-around
more likely.
• Potential burble/downdraft due
to the drop-offs on both ends.

5. Mountain Airports
Airport No. 1
• Glenwood Springs(KGWS)
• Considered by many to be
one of the more difficult
paved airports in Colorado
Airport No. 2
• Mountain Air (2NC0)
• North Carolina
Phil Verghese, www.pfactor.com

6. Glenwood Springs, CO
Glenwood Springs, CO 5916 msl (Neil Davis)

7. Mountain Air, Burnsville, NC
Mountain Air, NC 4432 msl

8. Ashe County, Jefferson, NC
Ashe County, NC 3178 msl

9. Gunnison, CO
Gunnison, CO 7680 msl

10. What is Mountain Flying
• Not about back-country airstrips
• Not exclusively about extremely high density
altitude
Cavanaugh Bay, ID 2484 msl (Robert Kinney)

11. What is Mountain Flying
• Safely enjoying the beauty of the mountains
and landing at prime destinations
Grand Lake, CO (KGBY 8207 msl)

12. What is Mountain Flying
• The science and art of wind and weather and
how they are affected by topography.
• Understanding your airplane's and your
performance limitations.
• Learning how these will affect
– the decisions you make
– the flight procedures you use
– the skills and knowledge you will need to apply

13. Mountain Risk Factors
• Density Altitude
• Terrain
• Weather
– Changes very quickly and from pass to pass
• Wind
• The Magenta Line
• Human Factors

14. Risk Mitigation
• Basic Premise #1—Always Remain In a
Position Where You Can Turn To Lowering
Terrain.
• Basic Premise #2—Do Not Fly Beyond the
Point of No Return.
-Sparky Imeson, Mountain Flying Bible
• Understand your airplane and yourself.

15. Human Factors
• PAVE and IM SAFE Checklists

16. Human Factors
• Hypoxia
– Diminished vision, behavioral changes, diminished
judgment
– Consider supplemental O2 even in the “low”
mountains and especially when crossing at night
or IFR
• Dehydration

17. Altitude and Performance
• Reduced Power
– Normally-aspirated engines lose approximately 3%
of available power for each 1000’ above sea level
– Leadville, CO (9927 msl) on a Standard Day , a
normally-aspirated engine can develop only 70° of
its rated horsepower.
• POH: Cessna 172 at 8000’ produces only 72% of rated
HP
– 7% (variable pitch prop)-8% (fixed pitch) loss of
climb performance per 1000’ altitude

18. Altitude and Performance
• Reduced Airfoil Efficiency
– Wings need more airspeed to achieve lift
– Propellers provide less thrust for a given rpm
• Increased TAS for given IAS
– 2% TAS increase per 1000’
– At 10,000’, 100 IAS = 120 TAS
– At 5000’, 100 IAS = 110 TAS

19. Altitude and Performance
• Whenever we talk about altitude and aircraft
performance, we are talking about density
altitude
• Density Altitude = “Performance Altitude”
• Pressure altitude corrected for non-standard
temperature.

20. Density Altitude
• ~120’ for every 10° above
standard temperature
• Standard pressure and
70°F (21°C)
– Leadville, CO (9927 msl)
• Standard terperature: -5°C
• Density Altitude: 12,800’
– KGEV – Ashe County, NC
(3178 msl)
• Standard temperature: 9°C
• Desnity Altitude: 4600’

21. Takeoff and Climb
• Requirement to lean for full power
• Longer takeoff roll
• Fixed Pitch: about 12% longer takeoff roll 1,000 feet of density
altitude up to 8,000 feet; about 20% for each additional 1,000 feet
density altitude
• Constant Speed: about 10% for each 1,000 feet up to 8,000 feet;
about 15% for each additional 1,000 feet
• Slower acceleration
• Faster perceived speed
– Optical illusion
– Tendency to pull back too early
• Reduced climb capability
– Vx increases and Vy decreases

22. Takeoff and Climb
180 HP Cessna 172
Ashe County, NC
Temperature: 70°F
D-Alt: 4600’
Rotation: 55 KIAS
• Perceived rotation
speed: 60 KTS
• HP Available: 155
• Takeoff runway
required: >300 more
than sea level

23. Takeoff and Climb
180 HP Cessna 172
Ashe County, NC
Temperature: 90°F
D-Alt: 5900’
Rotation: 55 KIAS
• Perceived rotation
speed: 67 KTS
• HP Available: 147
• Takeoff runway
required: >400 more
than sea level

24. Takeoff and Climb
180 HP Cessna 172
Leadville, CO
Temperature: 70°F
D-Alt: 12,803’
Rotation: 55 KIAS
• Perceived rotation speed:
70 KTS
• HP Available: 110
• Takeoff runway required:
Performance chart only
goes up to 8000’

25. Takeoff and Climb
180 HP Cessna 172

26. Takeoff Planning & Techniques
• Plan for less weight, less than full fuel
– Takeoff performance charts show a substantial
increase in performance as weight goes down.
• Lean for best power
• Proficient in short and modified soft field
takeoffs

27. Takeoff Planning & Techniques
• Compute and anticipate takeoff distances and
expected rate of climb
• Maintain a margin for book takeoff distances to
account for mountain wind and other factors
• Have a takeoff abort point
– Rule of thumb: 70% takeoff speed 50%runway

28. Takeoff Planning & Techniques
• Downhill departure (may even have a tailwind
since the downhill will compensate)
• Many mountain airports are one-way-in-one-
way out
Aspen, CO 7838 msl

29. En Route
• En route
– Aircraft service ceilings
– Mountain airflow and ridge crossings
– Mountain weather
– Human factors: hypoxia!

30. Mountain Air Flow

31. Mountain Winds and Weather
• Strong winds can cause
dangerous conditions.
• Avoid flying if winds near
ridge tops exceed 25Kts
• Windward side will
generally be smoother
• Leeward side will
generally produce
downdrafts
• Mountain waves
• Downdrafts can exceed
aircraft climb capability

32. Mountain Winds and Weather
• Lenticular clouds
– Byproduct of mountain
wave and strong winds
– Stable air flowing over
mountain ranges
– Begins to form on
leeward side
– Can extend for hundreds
of miles
– Often smooth above the upwind side
– Turbulent otherwise

33. Mountain Winds and Weather
• Cap clouds
– Similar to formation
of lenticular clouds
– Upslope winds cooling
to the dew point
– Peak of the ridge can be
visible from the leeward side and pilots have been
suckered into thinking
they can sneak across

34. Mountain Winds and Weather
• Rotor clouds
– Form on the leeward side under the mountain
wave.
– Very turbulent
– Upslope air – supercooled clouds with icing
dangers

35. Ridge Crossings
Hagarman Pass, CO 11,925 msl

36. Ridge Crossings
• Mountain pass depicted
on charts is not necessarily
the best place to cross
• Downdrafts can exceed climb
capability
• 45° approach for options
• Be level at least 3 miles away
• 45-90° departure – shortest route to lowering
terrain
• Updrafts and downdrafts can
occur on either the windward or leeward side
– Shuttle climbs

37. Emergency Landing Sites
• Variety and Irregularity makes it difficult to list general
rules.
• Preflight planning: GPS direct or “IFR” (“I Follow Roads”)?
• Survivability
• Visibility
• Access
• Don’t fly needlessly low or slow
• Gliding opportunities toward lower terrain
• Be aware of increased turn radius required
– Radius of turn increase by square of speed.
– Double the speed = 4X the radius required

38. Landing
• Revisiting altitude effects on altitude
• Density altitude effects on TAS and “feel”
– Same IAS; increased TAS
• 65 KIAS approach in C172
at KGEV at 70° F= 71 KTAS
• 73 when 90°F
• Longer landing distances
• Illusions of increased
speed

39. Landing
• Windshear and
downdrafts
caused by terrain
features
• Steepen the approach –
short field configuration
• Uphill, not downhill

40. IFR Considerations
• High mountain west: Don’t!
– Lower altitudes may not be an option
– Higher altitudes may be beyond climb capability
• Increased TAS/GS may require greater vertical
speed needed but may not have the capability,
especially for a missed approach
• Always check departure performance
requirements and
obstacle departure
procedures

41. IFR Considerations
• Standard Instrument
Departures (SID)
guarantee obstacle
clearance
– Can your performance
profile comply?

42. IFR Considerations
• Obstacle Departure
Procedures (ODP)
• Pilot’s prerogative to
use when not accepting
a SID
• ATC does not assume
you will use it, so advise

43. IFR Considerations
Obstacle Departure Procedures

44. IFR Considerations
Obstacle Departure Procedures

45. Wrap Up
• Flight Planning and Route Selection
– Airways generally over easier terrain
– Diversion options
– Consider of wind and terrain
– Emergency landing sites
– Don’t be one of the “children of the magenta”
• Fly at Less than max gross
• Fly in the morning, not the afternoon
• Day VFR only inmost cases
• GPS terrain readouts
• Pilotage
• Use Flight Following (when you can )
• Consider filing VFR Flight Plans and making position reports

46. Visual Approach and Landing into Aspen, CO
Video in Original

47. Mountain Flying
Q&A
Corona (Rollins) Pass, CO 11,571 msl (Charles Luce)