In this article, we will be diving into some of the aircraft performance questions you may see on the private pilot written exam. Check out Sporty’s online ground school here to get access to their online private pilot ground school. ASA is another great private pilot test prep software for student pilots looking to pass their FAA written knowledge test.
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How to Determine Crosswinds
What is the crosswind component for a landing on Runway one eight if the tower reports the wind as 220 degrees at 30 knots?
A. 19 knots
B. 30 knots
C. 23 knots
Solution: To find the answer to this question, first subtract the runway direction of 180 degrees from the wind direction of 220 degrees to get 40 degrees (see orange arrow in figure 2 below). Remember that runway headings are aligned to their magnetic direction. According to Chapter 14 of the Pilot’s Handbook of Aeronautical Knowledge (PHAK), “the runway number is the whole number nearest one-tenth the magnetic azimuth of the centerline of the runway, measured clockwise from the magnetic north.” So, runway 18 would be aligned with 180 degrees magnetic.
Since the wind speed is reported at 30 knots, draw a line on the 30-degree arc in the diagram (as highlighted by the red dashed line in Figure 2 above). Then draw a line down from the area where the wind angle line and wind velocity arc intersect. The crosswind component is just to the left of 20 degrees so we can see the crosswind given the conditions is 19 knots.
How to Determine Landing Ground Roll Distance
Determine the approximate landing ground roll distance for an aircraft given the current set of conditions. The pressure altitude is 1,250 feet, headwind is at 8 knots, and temperature is standard at 15 degrees Celsius or 59 degrees Fahrenheit.
A. 275 feet
B. 470 feet
C. 366 feet
Solution: Since the pressure altitude is 1,250 feet which is between sea level and 2,500 feet, we need to take the averages of the ground roll distances at sea level and 2,500 feet. Add 470 to 445 to get 915 then divide by 2 to get the approximate landing ground roll distance at 1,250 feet which is 457.5. Since there are 8 knots of headwind, we need to decrease the distance by 20 percent, since the chart says to decrease the distances 10 percent for each 4 knots of headwind. 20 percent of 457.5 is 91.5 so subtract 91.5 from 457.5 to get the correct answer of 366 feet. 366 feet would be the approximate landing ground roll needed if the pressure altitude were 1,250 feet, there was 8 knots of headwind, and the temperature was standard.
How to Determine Takeoff Ground Roll Distance
What is the approximate ground roll distance necessary for takeoff under the following conditions? The outside air temperature is 90 degrees, the pressure altitude is 4,000 feet, takeoff weight is 2,600 pounds and there are 20 knots of headwind.
A. 1,000 feet
B. 600 feet
C. 800 feet
Solution: To find the answer to this question, start by drawing a line up from the 90 degrees outside air temperature line at the bottom of the chart (see figure 6 below). Draw the line up until it intersects the 4,000-pressure altitude line. Then draw the line to the right and then down until it meets the takeoff weight of 2,600 pounds as illustrated in the middle of the chart in figure 6. Continue drawing the line over to the right until meeting the wind component section. Since there is a 20-knot headwind, draw the line down and to the right until it intersects the 20-knot wind line near the right of the chart. Finally draw the line to the right. Notice that the line ends up right under the 1,000-foot figure on the far-right hand side of the chart. This means the approximate takeoff ground roll distance based on the given set of conditions is 800 feet.
How to Determine Density Altitude
Determine the density altitude for these conditions. The altimeter setting is 30.30, the runway temperature is 25 degrees Fahrenheit, and the airport elevation is 3,894 feet above mean sea level.
Source: Figure 8 from Airman Knowledge Testing Supplement for Sport Pilot, Recreational Pilot, Remote Pilot and Private Pilot
A. 2,200 feet MSL
B. 3,000 feet MSL
C. 3,650 feet MSL
Solution: The first step to solving this problem is to adjust the pressure altitude based on the current altimeter setting which in this case is 30.30. Notice the pressure altitude conversion factor of minus 348 for the altimeter setting of three zero point three zero. We need to subtract 348 from the airport elevation of 3,894 feet to get the adjusted pressure altitude of 3,546 feet. Then draw a line up and to the right roughly halfway between the 3,000 and 4,000 foot pressure altitude lines since 3,546 feet is roughly halfway between 3,000 and 4,000. Next draw a line up from the 25-degree outside air temperature line at the bottom of the chart until it intersects the red pressure altitude line. Finally draw the line over to the left to find that the line ends up just above the 2 in the chart.
Since the figures on the left of the chart are showing the approximate density altitude in thousands of feet, we can see the best answer to this question is 2,200 feet since the orange arrow is pointing just above the 2,000-foot density altitude line on the left of the chart.
What Types of Atmospheric Conditions Reduce Aircraft Performance
Which combination of atmospheric conditions will reduce aircraft takeoff and climb performance?
A. High temperature, low relative humidity, and low-density altitude.
B. High temperature, high relative humidity, and high-density altitude.
C. Low temperature, low relative humidity, and low-density altitude.
Solution: See chapter 11 of the Pilot’s Handbook of Aeronautical Knowledge for more information on how temperature and humidity affect aircraft performance. Higher air temperatures and high humidity result in reduced aircraft performance due to lower air density and high-density altitude. Higher air temperature and humidity will reduce an aircraft’s takeoff and climb performance. This results in the aircraft needing a longer takeoff roll on takeoff.
How to Calculate Fuel Consumption
What is the expected fuel consumption for a 1,000-nautical mile flight under the following conditions?
The pressure altitude is 8,000 feet, temperature is 22 degrees Celsius, manifold pressure is 20.8 inches and the wind is calm.
A. 73.2 gallons
B. 60.2 gallons
C. 70.1 gallons
Solution: Since the temperature is 22 degrees Celsius, which is above standard we would use the figures on the far right (see figure below). Go down to the row which highlights the power settings, speed, and fuel flow at a pressure altitude of 8,000 feet. To find the expected fuel consumption, we first need to know the expected time in flight, assuming no wind. A pilot would need to account for winds in the time en route calculation if there were expected headwinds or tailwinds. Since the flight will be 1,000 nautical miles and our expected true airspeed is 164 knots, divide 1,000 by 164 to get the expected flight time of 6.1 hours. Since the aircraft is expected to burn 11.5 gallons per hour, multiply 11.5 by 6.1 to get 70.1. Given the current conditions and aircraft performance, the aircraft will be expected to burn 70.1 gallons of fuel during this 1,000 nautical mile flight.
Thank you for reading and we hope you now have a better understanding of how to solve the aircraft performance questions you may see on the private pilot written exam. These questions are not too difficult after you practice them a few times. Best of luck in your flying journey!