Mountain Checkout

Mountain Checkout / Mountain Flying

Due to the unique set of challenges encountered, it's a good idea to do a mountain checkout before flying as PIC in the mountains, deserts, and other remote or challenging areas. WVFC requires a Mountain Checkout before members are allowed to take club aircraft into the mountains.

The outline below serves as a framework for a mountain checkout. The ground portion usually take approximately 2-4 hours, depending on your background and experience, and your success at completing the prescribed reading ahead of time. The flight portion typically takes all day, and includes approximately 5 hours of flight time. We usually get lunch at someplace interesting along the way.

It is best to do the ground portion in a separate session days in advance of the flight portion. You should schedule 2.5-4 hours for the ground session (depending on your experience), and a full day (0800-1900) for the flight portion. The day of the flight usually starts with a thorough flight briefing and review of the flight plan — and possible rework — in light of the current conditions and forecast.

On the day of your mountain checkout flight, don't forget to bring the various recommended items (below) with you. And when you preflight your aircraft, be mindful of aircraft weight and do not automatically "top off the tanks for a long flight." In many cases, we will want no more fuel than "to the tabs" before departure (yet within safety margins, including appropriate reserves). Our goal is to arrive in the mountains at or below 90% of our maximum gross weight for the aircraft.

Reading and References (read before ground session)

Discussion Topics (for ground and flight sessions)

VFR, IFR, and Night Flying

  • Mountain flying is flown Day VFR.

  • Neither IFR nor night flight are particularly compatible with mountain flying. Both IFR and night flying are strongly discouraged in the mountains. (Turboprops and jets are possible exceptions, and then only to arrive/depart via safe corridors and procedures.)

  • IFR in the mountains requires a highly skilled pilot and a very high performance aircraft.

  • Night flying obscures most visual cues, making terrain and obstacle clearance difficult if not impossible.

Aircraft Performance Issues

    • The trifecta of performance hits (due to thinner air as density altitude increases):

      • Thinner air ⇒ less power from engine (unless turbocharged or turbine)

      • Thinner air, less power ⇒ less thrust from prop

      • Thinner air, less power, less thrust ⇒ less lift from the wings

    • Climb rate reduced

    • Same indicated airspeed but higher ground speed for both takeoff and landing

    • Higher ground speed but with lower performance ⇒ greatly increased takeoff and landing distances

    • Density altitude (rough rule of thumb is to add 120 feet per 1 °C over standard)

    • Density altitude horsepower rule of thumb: A normally aspirated aircraft engine will lose approximately 3% of its horsepower for every 1,000-foot increase in density altitude. So at a density altitude of 7,000 feet, over 21% of engine power has vanished.

    • Aircraft Horsepower - Unless the pilot has a great deal of mountain flying experience, 160 HP should be considered the minimum power for mountain flying. Additionally, 60 HP per person should also be considered minimum. Note that these are minimums; in many cases greater horsepower is highly recommended, especially for those not significantly experienced in mountain flying.

    • Aircraft Weight - It is highly recommended that you limit your aircraft's weight to no more than 90% of it's maximum gross weight. This reduction in weight will noticeably improve aircraft performance. Further weight reduction, when reasonably possible, will further improve aircraft performance.

    • Reduced Fuel - One way to achieve a lower aircraft weight for your mountain flying (see above) is to limit your fuel to only the fuel needed, plus appropriate reserves. When able, plan on refueling at a lower altitude airport after leaving the mountain flying area rather than refueling in the mountains. If you need to add fuel while in the mountains, be judicious about the amount of fuel added.

    • The minimum required Rate of Climb (ROC) performance is a function of pilot skill level, the aircraft, and conditions. But a good guideline is to require at least 400 FPM expected performance at the airport's density elevation. A more conservative minimum of 500 FPM is recommended for pilots with minimal mountain flying experience (less than 6 flights in appropriately challenging mountainous environments). If the performance charts and calculations predict performance less than your minimum ROC then you should plan for another day, time, or location.

Cessna C172SP

Cessna C182T

Cirrus SR20

Cirrus SR22

    • Use POH and actual/predicted conditions to calculate expected performance

    • From the above data, you should note that the C182 has approximately 150' better ROC performance at any given altitude than the C172. This performance improvement translates to about 3,000'-4,000' feet of additional usable altitude (to meet the same minimum required ROC performance).

    • Also note that the C172SP has better climb gradient performance than the Cirrus SR20. The SR20 is not a good match for the mountains.

    • Make sure to use recommended leaning - often lean above 3,000-5,000 feet (for the C182T use the fuel flow placard per the POH)

    • Abort takeoff if unable to reach 70% of Vr by midpoint of runway

    • W&B / DA / fuel / performance

    • Spiral up if/as needed to gain altitude (plan for extra flight time)

    • Leverage orthographic lift

    • Larger turning radius due to higher ground speed - Higher true airspeeds result in larger radius turns (the increase in turing radius depends on if you are holding the rate of turn (directly proportional), or angle of bank (proportional to the square of the airspeed) constant for the comparison). Either way, it takes more distance to make a turn at a higher TAS than at a lower TAS, so be careful when turning at the the higher true airspeeds in the mountains.

    • Adjust mixture for maximum power during run-up/pre-takeoff power check

    • Consider runway slope

      • Given in at least 4 different forms: degrees, percentage, gradient, ratio (be careful not to confuse your units)

      • Note: For small angles (≤ 10°) each 1.0° = 1.75%

        • Simple percent to degree conversion: 1% = 0.6°, 2% = 1.1°, 3% = 1.7°, 4% = 2.3°, 5% = 2.9°, 6% = 3.4°, 7% = 4.0°

        • Simple degree to percent conversion: 1.0° = 1.75%, 2.0° = 3.5%, 3.0° = 5.25%, 4.0° = 7%

      • Even 1% (0.6°) is very noticeable, 4.1% (2.3°) is huge! (See O54 - Lonnie Pool Field at Weaverville, CA)

      • Consider both slope and winds for both takeoff and landing

      • Consider takeoff/departure before landing, especially at one-way in / one-way out airports

    • Flaps - alternate flap settings should be considered for both takeoff and landing:

Climb Performance Factors

Since weight, altitude and configuration changes affect excess thrust and power, they also affect climb performance. Climb performance is directly dependent upon the ability to produce either excess thrust or excess power. Earlier in the book it was shown that an increase in weight, an increase in altitude, lowering the landing gear, or lowering the flaps all decrease both excess thrust and excess power for all aircraft. Therefore, maximum AOC and maximum ROC performance decreases under any of these conditions.

      • Takeoff

        • Takeoff flaps offer more lift, but they also present more drag

        • In a high density altitude environment this additional drag saps the already limited excess power available

        • Takeoff flaps can result in a shorter takeoff roll, but at the expense of wasted energy (KE + PE). Use minimum takeoff flaps, when able

        • Consider runway length available vs expected climb performance

        • Consider a no flap takeoff if sufficient runway length is available

        • If you do use takeoff flaps retract them as soon as safe and practical to minimize drag and maximize performance

        • Make sure to use speeds appropriate for the chosen flap configuration

      • Landing

        • The use of full flaps can help reduce approach and landing speed and increase drag, thereby reducing landing runway requirements

        • But the use of full flaps reduces the excess power available (due to the significant drag) to overcome downdrafts or LLWS

        • Consider using full (or nearly full) flaps when landing on a short runway, as long as downdrafts and LLWS are not expected

        • Consider using only partial flaps to reduce drag and leave more excess power available to overcome downdrafts or LLWS, if sufficient runway is available

        • Consider an aiming point 1/3 the way down the runway if landing in the presence of downdrafts or LLWS, if sufficient runway is available

        • Make sure to use speeds appropriate for the chosen flap configuration (and appropriate corrections for gusting winds and LLWS)

Winds

Weather

    • (See winds, above)

    • Can obscure mountains and obstacles

    • Can change rapidly

    • Thunderstorms are common in the afternoons

    • Maintain a minimum of 20 miles from thunderstorms (greater distance is better)

    • Poor visibility - smoke/fog can settle into a valley/canyon

Additional Hazards

Emergency / Rescue Issues

Poor Communication Issues

    • Aviation COM and VOR NAV is based on VHF line-of-sight communications

    • COM radios may not work

    • NAV radios (including GPS!) may not work

    • Cell phones may not work

    • Close your flight plan / terminate flight following while still in COM range

    • Climb if/as needed for COM/NAV

    • Bring paper (or pre-downloaded) charts just in case

Altitude and Physiology

Pre-flight briefing for each airport of intended use

For each airport of intended use (including possible alternates) read all available information, including chart supplement entry, ForeFlight comments and remarks, airport-specific web pages (often related to the local municipality), etc. You goal is to learn of any hazards, limitations, conventions, recommendations, reporting points, contact information, etc. relevant to each specific airport. In particular, be alert for:

Recommendations

    • Defer to another day if winds are > 20-30 kts.

    • Remember to bring your mountain go bag (emergency kit)

    • Remember to bring emergency clothing, food, water, etc.

    • Give thunderstorms a wide berth - usually at least 20 miles.

    • Fly at least 2,000' above nearby peaks when flying over mountains.

    • Cross ridgelines at a 45° angle to improve escape options when flying near the peaks.

    • Lean the engine to maximize power at altitude (non-turbocharged engines).

    • Compute density altitude - DA adds 120' for every 1 °C over standard.

    • Consult the performance section of your POH to verify performance under expected conditions. Determine climb performance and runway requirements for takeoff and landing.

    • Allow an additional margin of safety to account for sub-optimal performance of aircraft, pilot, winds, down-drafts, etc. (+20-50%?).

    • Limit aircraft weight to 90% or less of MGW while operating in the mountains.

    • Do not "top off fuel" unless necessary. Refuel (as needed) when out of the mountains.

    • Abort takeoff if unable to reach 70% of Vr by midway point of runway.

    • Review your POH and determine/calculate Vx and Vy for your expected altitude and weight.

    • Adjust airport pattern to avoid/compensate for terrain, box canyons, downdrafts, etc.

    • Learn/use canyon turn to maneuver/escape in tight canyons.

    • Always have a plan just in case you don't achieve the expected performance. (Eg, "On takeoff we're going to veer to the left around that hill if we don't achieve enough climb rate to climb over it.")

    • Learn/master short field landings and takeoffs.

    • Consider flap settings for takeoff and landings as appropriate for the situation

    • Make a reconnaissance pass of airport and runway before landing.

    • Departure often takes more runway than landing - check the numbers before landing.

    • Visualize the winds and airflow - when able, exploit updrafts and avoid downdrafts.