by Jonathan M. Stern
At airports with operating control towers, the controller instructs arriving aircraft how and where to enter the pattern. For example, an aircraft might be instructed, "Cessna 12345, enter left base for runway 23, report entering base."
Flight Simulator is not yet at the point where it has such advanced air traffic control simulation capabilities. Accordingly, for visual flights, you should either pretend that the airport is uncontrolled or give yourself air traffic control instructions that you might receive from an air traffic controller.
At uncontrolled airports, the standard traffic pattern entry procedure involves a 45° entry onto the downwind leg. Figure 6.1 depicts the standard traffic pattern (including pattern entry) at an uncontrolled airport.Figure 6.1. The standard traffic pattern at an uncontrolled airfield.
The following steps provide the procedure for entering the standard pattern for arriving aircraft:
- Enter pattern in level flight abeam the midpoint of the runway at pattern altitude (1,000 feet above airport elevation unless established otherwise).
- Maintain pattern altitude until turning onto the base leg. Note that some instructors teach that the descent should begin on the downwind leg after passing abeam the landing threshold.
- Complete the turn onto the final approach at least one quarter mile from the runway.
The following steps are for departing aircraft:
- Continue straight ahead until beyond the departure end of the runway.
- If remaining in the traffic pattern, commence the turn to the crosswind leg beyond the departure end of the runway and within 300 feet of reaching pattern altitude.
- If departing the traffic pattern, continue straight out on upwind leg or exit on a 45° left turn beyond the departure end of the runway and after reaching pattern altitude.
As an example, take the traffic pattern for Runway 36 at Meigs Field. A non-standard (right) pattern is used with Runway 36 in real life, because a left pattern would put airplanes in the vicinity of downtown Chicago. Nonetheless, we will fly it with a standard left traffic pattern at 800 feet above the airport (at 1,400 feet).
Follow these steps:
- When the airplane passes through 1,100 feet, commence a left turn onto the crosswind leg while continuing the climb to 1,400 feet.
- As the aircraft reaches 1,400 feet, lower the pitch as necessary to maintain altitude. Fly the downwind leg approximately one quarter mile from the landing runway.
- In the real airplane, the pilot continually looks in different directions. With Flight Simulator, you need to take advantage of the different viewing directions. Make a 90° left turn onto downwind at an appropriate time.
- Reduce the throttle setting so that the airspeed does not exceed 140 knots.
- When the airplane passes abeam the midpoint of the landing runway, perform the Before Landing checklist (in Appendix D). Turn the carburetor heat on before the throttle setting is further reduced.
- It's a good idea to have target speeds for various points in the traffic pattern. For example, consider slowing to 90 knots on downwind after extending 10° of flaps, 80 knots on base after extending 20° of flaps, and 70 knots on final with full flaps.
- Drop the first 10° of flaps and adjust the throttle to slow to 90 knots.
- The turn onto base leg should begin when the airplane is situated 45° off the approach end of the runway. To judge this point, select the left rear view (Shift+1). See Figure 6.2. Figure 6.2. The turn from downwind to base should generally begin when the airplane is situated 45° off the approach end of the runway, as shown here.
- On the base leg, the airplane must be descended from pattern altitude at a rate that allows it to arrive at airport elevation at the completion of the final approach.
- Select a point near the center of the first one-third of the landing runway and target it as the touchdown point.
- Extend the flaps to 20° during the base leg and, as discussed previously, the target speed on base leg should be 80 knots. If there is a wind blowing down the runway, there likely will be a crosswind while flying the base leg, which requires a crab angle to the left while flying a left pattern (see Figure 6.3.) Figure 6.3. A crab angle is often required while flying the base leg.
- On all legs of the traffic pattern, an awareness of the wind and its effect must be maintained. Each leg should be flown on a heading that keeps the aircraft parallel to (on downwind and upwind) or perpendicular to (on cross-wind and base) the landing runway.
- Make the turn onto the final approach at a safe altitude relative to terrain and obstructions and lead it so that the airplane rolls wings-level aligned with the runway's centerline. Many students have difficulty judging how much lead distance to allow for this, and this problem is aggravated by a tailwind on base leg or when transitioning to faster aircraft, which require more lead distance. Don't be disappointed if you overshoot or undershoot the turn to final several times. With practice, you will improve.
- Make the turn from base to final with a shallow to medium banked turn, because the airplane is now slowed so that a steep bank could increase the stall speed to the speed at which the airplane is flying.
Figure 6.4 graphically depicts the increase in load factor (G units, which represent the force of gravity) as bank angle is increased while maintaining altitude.Figure 6.4. Load factor increases dramatically at bank angles greater than 60°.
For example, at 60° of bank in level flight, the load factor is 2 Gs, meaning that the effective load that the airplane is supporting is twice its weight at rest on the ground. The airplane's stall speed increases in proportion to the square root of the load factor. The square root of 2 being 1.414, the calibrated stall speed of the Cessna with 20° of flaps and landing gear extended increases from 52 knots to 74 knots if a 60° banked turn is made while maintaining altitude. Using the airspeed calibration tables in Appendix D, you can see that 74 knots calibrated is approximately 72 knots indicated with 20° of flaps.
What all this means is that using a steep turn from base to final could put you dangerously close to a stall. If, during the turn to final, you recognize that you will overshoot, do not steepen the bank beyond 35 or 40 degrees. Instead, make an s-turn to become realigned with the landing runway or abandon the approach and start again.
After completing the base to final turn, align the airplane with the runway centerline. This is done to determine whether there is a crosswind. If there is, the airplane will drift left or right of centerline. Assuming no crosswind, the airplane should remain aligned with the centerline. The Course Tracking feature in Flight Simulator may prove useful in assessing the quality of your traffic patterns.
For additional instruction and practice with traffic patterns, select the Options/Flight Instruction menu and choose "Lesson 7—Traffic Pattern" from the Advanced Lesson Category and/or "Lesson 2—Attitude Flying" (Basic Lesson Category).