Mountain Flying, A Primer (2013)


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A primer on the fun and challenge of personal flying in mountainous terrain
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  • Cavanaugh Bay is only 2484 msl
  • Three components
  • Ask questions about effect on performance. Get the level of knowledge.
  • Ask questions about effect on performance. Get the level of knowledge. Don’t get too excited about the increase in TAS; you need the power for it!
  • HP. 3%=5.4HP*4.6=~25 less HP (~155). TAS 2@=1.3*4.6=5.98 (approx 71).
  • HP. 3%=5.4HP*4.6=~25 less HP (~155). TAS 2@=1.3*4.6=5.98 (approx 71).
  • HP. 3%=5.4HP*4.6=~25 less HP (~155). TAS 2@=1.3*4.6=5.98 (approx 71).
  • Strong winds can cause some of the most dangerous conditions pilots must contend with in mountainous terrain,To minimize the chance of encountering dangerous downdrafts and turbulence, flight operations should be avoided if the winds aloft forecast near the ridge tops exceed 25 knots. Consider planning the trip when the forecasted winds are less than 25 knots, such as early morning or evening.
  • Explain same IAS, different GS – don’t be fooled!. Uphill will require more nose-up.
  • Explain same IAS, different GS – don’t be fooled!. Uphill will require more nose-up.
  • Wind and terrain: which side will produce the greatest turbulence or downdrafts and give the most outs?Pilotage: Stan and Corona Pass; turn to the on-course heading (compare with doing that in student cross countries).
  • Mountain Flying, A Primer (2013)

    1. 1. Corona (Rollins) Pass, CO 11,571 msl (Charles Luce)Mountain FlyingA Primer© 2013 Mark J.
    2. 2. Mountain AirportsAirport 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 directionout recommended due to terrain.• Limited go-around opportunities.• Potential burble/downdraft onfinal 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 directionout due to terrain and slope.• Runway illusion makes go-aroundmore likely.• Potential burble/downdraft dueto the drop-offs on both ends.
    3. 3. Mountain AirportsAirport No. 1• Glenwood Springs(KGWS)• Considered by many to beone of the more difficultpaved airports in ColoradoAirport No. 2• Mountain Air (2NC0)• North CarolinaPhil Verghese,
    4. 4. Glenwood Springs, COGlenwood Springs, CO 5916 msl (Neil Davis)
    5. 5. Mountain Air, Burnsville, NCMountain Air, NC 4432 msl
    6. 6. Ashe County, Jefferson, NCAshe County, NC 3178 msl
    7. 7. Gunnison, COGunnison, CO 7680 msl
    8. 8. What is Mountain Flying• Not about back-country airstrips• Not exclusively about extremely high densityaltitudeCavanaugh Bay, ID 2484 msl (Robert Kinney)
    9. 9. What is Mountain Flying• Safely enjoying the beauty of the mountainsand landing at prime destinationsGrand Lake, CO (KGBY 8207 msl)
    10. 10. What is Mountain Flying• The science and art of wind and weather andhow they are affected by topography.• Understanding your airplanes and yourperformance limitations.• Learning how these will affect– the decisions you make– the flight procedures you use– the skills and knowledge you will need to apply
    11. 11. Mountain Risk Factors• Density Altitude• Terrain• Weather– Changes very quickly and from pass to pass• Wind• The Magenta Line• Human Factors
    12. 12. Risk Mitigation• Basic Premise #1—Always Remain In aPosition Where You Can Turn To LoweringTerrain.• Basic Premise #2—Do Not Fly Beyond thePoint of No Return.-Sparky Imeson, Mountain Flying Bible• Understand your airplane and yourself.
    13. 13. Human Factors• PAVE and IM SAFE Checklists
    14. 14. Human Factors• Hypoxia– Diminished vision, behavioral changes, diminishedjudgment– Consider supplemental O2 even in the “low”mountains and especially when crossing at nightor IFR• Dehydration
    15. 15. 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 , anormally-aspirated engine can develop only 70° ofits rated horsepower.• POH: Cessna 172 at 8000’ produces only 72% of ratedHP– 7% (variable pitch prop)-8% (fixed pitch) loss ofclimb performance per 1000’ altitude
    16. 16. 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
    17. 17. Altitude and Performance• Whenever we talk about altitude and aircraftperformance, we are talking about densityaltitude• Density Altitude = “Performance Altitude”• Pressure altitude corrected for non-standardtemperature.
    18. 18. Density Altitude• ~120’ for every 10° abovestandard temperature• Standard pressure and70°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’
    19. 19. Takeoff and Climb• Requirement to lean for full power• Longer takeoff roll• Fixed Pitch: about 12% longer takeoff roll 1,000 feet of densityaltitude up to 8,000 feet; about 20% for each additional 1,000 feetdensity 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
    20. 20. Takeoff and Climb180 HP Cessna 172Ashe County, NCTemperature: 70°FD-Alt: 4600’Rotation: 55 KIAS• Perceived rotationspeed: 60 KTS• HP Available: 155• Takeoff runwayrequired: >300 morethan sea level
    21. 21. Takeoff and Climb180 HP Cessna 172Ashe County, NCTemperature: 90°FD-Alt: 5900’Rotation: 55 KIAS• Perceived rotationspeed: 67 KTS• HP Available: 147• Takeoff runwayrequired: >400 morethan sea level
    22. 22. Takeoff and Climb180 HP Cessna 172Leadville, COTemperature: 70°FD-Alt: 12,803’Rotation: 55 KIAS• Perceived rotation speed:70 KTS• HP Available: 110• Takeoff runway required:Performance chart onlygoes up to 8000’
    23. 23. Takeoff and Climb180 HP Cessna 172
    24. 24. Takeoff Planning & Techniques• Plan for less weight, less than full fuel– Takeoff performance charts show a substantialincrease in performance as weight goes down.• Lean for best power• Proficient in short and modified soft fieldtakeoffs
    25. 25. Takeoff Planning & Techniques• Compute and anticipate takeoff distances andexpected rate of climb• Maintain a margin for book takeoff distances toaccount for mountain wind and other factors• Have a takeoff abort point– Rule of thumb: 70% takeoff speed 50%runway
    26. 26. Takeoff Planning & Techniques• Downhill departure (may even have a tailwindsince the downhill will compensate)• Many mountain airports are one-way-in-one-way outAspen, CO 7838 msl
    27. 27. En Route• En route– Aircraft service ceilings– Mountain airflow and ridge crossings– Mountain weather– Human factors: hypoxia!
    28. 28. Mountain Air Flow
    29. 29. Mountain Winds and Weather• Strong winds can causedangerous conditions.• Avoid flying if winds nearridge tops exceed 25Kts• Windward side willgenerally be smoother• Leeward side willgenerally producedowndrafts• Mountain waves• Downdrafts can exceedaircraft climb capability
    30. 30. Mountain Winds and Weather• Lenticular clouds– Byproduct of mountainwave and strong winds– Stable air flowing overmountain ranges– Begins to form onleeward side– Can extend for hundredsof miles– Often smooth above the upwind side– Turbulent otherwise
    31. 31. Mountain Winds and Weather• Cap clouds– Similar to formationof lenticular clouds– Upslope winds coolingto the dew point– Peak of the ridge can bevisible from the leeward side and pilots have beensuckered into thinkingthey can sneak across
    32. 32. Mountain Winds and Weather• Rotor clouds– Form on the leeward side under the mountainwave.– Very turbulent– Upslope air – supercooled clouds with icingdangers
    33. 33. Ridge CrossingsHagarman Pass, CO 11,925 msl
    34. 34. Ridge Crossings• Mountain pass depictedon 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 loweringterrain• Updrafts and downdrafts canoccur on either the windward or leeward side– Shuttle climbs
    35. 35. Emergency Landing Sites• Variety and Irregularity makes it difficult to list generalrules.• 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
    36. 36. Landing• Revisiting altitude effects on altitude• Density altitude effects on TAS and “feel”– Same IAS; increased TAS• 65 KIAS approach in C172at KGEV at 70° F= 71 KTAS• 73 when 90°F• Longer landing distances• Illusions of increasedspeed
    37. 37. Landing• Windshear anddowndraftscaused by terrainfeatures• Steepen the approach –short field configuration• Uphill, not downhill
    38. 38. 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 verticalspeed needed but may not have the capability,especially for a missed approach• Always check departure performancerequirements andobstacle departureprocedures
    39. 39. IFR Considerations• Standard InstrumentDepartures (SID)guarantee obstacleclearance– Can your performanceprofile comply?
    40. 40. IFR Considerations• Obstacle DepartureProcedures (ODP)• Pilot’s prerogative touse when not acceptinga SID• ATC does not assumeyou will use it, so advise
    41. 41. IFR ConsiderationsObstacle Departure Procedures
    42. 42. IFR ConsiderationsObstacle Departure Procedures
    43. 43. 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
    44. 44. Visual Approach and Landing into Aspen, COVideo in Original
    45. 45. Mountain FlyingQ&ACorona (Rollins) Pass, CO 11,571 msl (Charles Luce)