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WHS CLASS of '65
SKYDIVE INTO BLUE HOLE -- BELIZE
DEPARTURE CHECKLIST FOR
HIGH ELEVATION AIRFIELDS
NINE POINT CHECKLIST FOR DEPARTING HIGH ELEVATION AIRPORTS (>7,000' MSL)*
(1) RUN-UP AT MAXIMUM POWER
When running the engine up at a high elevation airfield, always run-up at full power (max. RPM), not the RPM recommended in the POH. Lean mixture until engine RPM just begins to drop, then advance mixture control two full rotations (720 deg.). Use this setting for takeoff --- in fact, do not alter this mixture setting in any way during taxi, takeoff roll, climbout, en route climb, cruise, descent, and landing after setting as long as you are flying and landing at high elevation airfields. If the mixture control is a lever, during run-up lean mixture until there is a slight drop in RPM, then enrich very slowly until maximum RPM is achieved. Keep mixture control at that setting while flying into and out of high elevation airfields.
(2) USE SHORT FIELD DEPARTURE PROCEDURE
Always use short field departure procedure as described in the A/C POH. Line up at the very end of the runway, advance to full power with brakes applied, then release brakes. If terrain clearance is not an issue, fly in ground effect above the runway to allow the A/C to gain airspeed before climbing out.
(3) CONSIDER DOWNHILL T/O ROLL
If the runway is sloped, consider using the downhill direction for T/O roll, even if winds are more favorable for an uphill departure. If there is a very high headwind (>20 knots), the uphill upwind RW may be preferable. A general rule of thumb: if the slope is 1% or greater, take off downhill. Taking off downhill with a 1% slope is like adding 10% to the runway length. If the winds are 20 knots or more, take off uphill into the wind. When taking off uphill consider the fact that you will probably be heading into rising terrain after you depart the RW environment. (See #4 and #7 below.)
(4) USE A RUNWAY FROM WHICH CLIMB OUT WILL BE AWAY FROM RISING TERRAIN OR OTHER OBSTRUCTION
All things being equal, use the runway where you will need the least rapid rate of climb for terrain clearance. This assumes the winds are calm or at a right angle to the runway, the runway is level (not significantly sloped), and surface conditions are the same the entire length of the runway.
(5) CARRY THE LEAST FUEL NECESSARY
Use minimum fuel load necessary to reach your destination with required reserve as the plane will climb out and fly better with less weight. This is no time to top off the tanks.
(6) T/O WHEN AMBIENT TEMPERATURE IS LOWEST
If possible take off during the coolest time of the day as the effect of density altitude will be minimized. Some piston GA aircraft may not be able to depart a high elevation airfield safely in the heat of mid day during the summer months.
(7) YOU MUST REACH 71% OF ROTATION SPEED BY HALF WAY DOWN THE RUNWAY
It is important to calculate precisely 71% of rotation speed. If you do not reach this speed by half way down the runway, you will not be able to take off in the available runway length. This does not account for clearance of trees or other structures on the runway heading and assumes you will not be required to clear any obstacles. If necessary you should walk off the entire length of the runway before departure and mark the mid point with a paper cup or other object placed on the ground at the side of the runway. If you cannot depart safely under existing conditions, wait for more headwind, cooler temperatures, or off-load passengers, baggage or fuel to lighten the load.
(8) CLIMB OUT WILL BE SLOW
You should realize that the A/C will not climb out at the same rate it does when departing a sea level airfield. Also control surfaces will not be as effective at high density altitude compared to sea level. It is important not to over-rotate at lift off to avoid a high angle of attack, high induced drag, and poor takeoff performance. Once the A/C breaks ground, allow it to accelerate in ground effect before climbing. Be patient --- climbout may be slower than 350'/min. Normally aspirated engines usually lose about 1" of manifold pressure for each 1,000' of elevation.
(9) BEST RATE OF CLIMB (Vy) DECREASES AS ALTITUDE INCREASES
Best angle of climb (Vx) increases slightly as elevation increases. Begin rotation just before reaching Vx, but fly no higher than one-half wingspan above the ground as the A/C accelerates to near Vy.
POCKET CHECKLIST FOR T/O PROCEDURES AT HIGH ELEV. AIRFIELDS
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