mountain flying, a primer (2013)

Corona (Rollins) Pass, CO 11,571 msl (Charles Luce)

Mountain Flying

A Primer

© 2013 Mark J. Kolberwww.midlifeflight.com

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.

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

Glenwood Springs, CO

Glenwood Springs, CO 5916 msl (Neil Davis)

Mountain Air, Burnsville, NC

Mountain Air, NC 4432 msl

Ashe County, Jefferson, NC

Ashe County, NC 3178 msl

Gunnison, CO

Gunnison, CO 7680 msl

What is Mountain Flying

• Not about back-country airstrips• Not exclusively about extremely high density

altitude

Cavanaugh Bay, ID 2484 msl (Robert Kinney)

What is Mountain Flying

• Safely enjoying the beauty of the mountains and landing at prime destinations

Grand Lake, CO (KGBY 8207 msl)

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

Mountain Risk Factors

• Density Altitude• Terrain• Weather– Changes very quickly and from pass to pass

• Wind• The Magenta Line• Human Factors

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.

Human Factors

• PAVE and IM SAFE Checklists

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

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

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

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.

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’

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

Takeoff and Climb180 HP Cessna 172

Ashe County, NCTemperature: 70°F

D-Alt: 4600’Rotation: 55 KIAS

• Perceived rotation speed: 60 KTS

• HP Available: 155• Takeoff runway required:

>300 more than sea level

Takeoff and Climb180 HP Cessna 172

Ashe County, NCTemperature: 90°F

D-Alt: 5900’Rotation: 55 KIAS

• Perceived rotation speed: 67 KTS

• HP Available: 147• Takeoff runway required:

>400 more than sea level

Takeoff and Climb180 HP Cessna 172

Leadville, COTemperature: 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’

Takeoff and Climb180 HP Cessna 172

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

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

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

En Route

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

Mountain Air Flow

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

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

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 thinkingthey can sneak across

Mountain Winds and Weather

• Rotor clouds– Form on the leeward side under the mountain

wave.– Very turbulent

– Upslope air – supercooled clouds with icing dangers

Ridge Crossings

Hagarman Pass, CO 11,925 msl

Ridge Crossings

• Mountain pass depicted on charts is not necessarilythe best place to cross

• Downdrafts can exceed climbcapability

• 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

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

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

Landing

• Windshear and downdrafts caused by terrain features

• Steepen the approach –

short field configuration• Uphill, not downhill

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 andobstacle departureprocedures

IFR Considerations

• Standard Instrument Departures (SID) guarantee obstacle clearance– Can your performance

profile comply?

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

IFR ConsiderationsObstacle Departure Procedures

IFR ConsiderationsObstacle Departure Procedures

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

Visual Approach and Landing into Aspen, COVideo in Original

Mountain Flying

Q&A

Corona (Rollins) Pass, CO 11,571 msl (Charles Luce)