Wind correction, ground speed, fuel used problems
Density altitude, true altitude, true airspeed problems
Weight and balance problems
Figure 1. Wind correction calculations are cumbersome on a slide-rule E6B but are very easy on Phone E6B.
3000 6000 9000 12000 2907 3225+10 3325+02 3335-05Answer: 352°
The forecasted winds aloft at the cruise altitude of 9000 ft are "3325+02", which means that the wind is from 330° (true) at 25 kts. From the Phone E6B main menu, select "Wind Correction/Ground Speed". Enter 12 as the true course. Press the down button or enter button to move to the True Airspeed input area. Enter 100 as the true airspeed, then enter wind direction 330, wind speed 25. Phone E6B will tell you that the true heading is 2°. Since magnetic variation is 10° E, the magnetic heading is 2 - 10 = -8. Since this value is negative, add 360 to get the magnetic heading 352°.
Note: if the True Airspeed and Wind Speed input areas do not have "(kts)" next to them, use the Change Units function to change these speeds to knots.
2. Predict the time en route. The distance from Mercer to Minot is 60 NM. Add 3 minutes for takeoff and departure climb.
Answer: 48 min
Phone E6B has already calculated that the ground speed is 80 kts. Just type in 60 as the distance. (If you do not see "(NM)" next to the Distance, use the Change Units function.) Phone E6B will tell you that the time is 45 min. Add the 3 minutes for takeoff and departure climb to get 48 min.
3. How much fuel will be used if the plane uses 6.8 gallons per hour? Add 3 gallons for takeoff and departure climb.
Answer: 8.1 gallons
Type in 6.8 as the fuel burn rate, and Phone E6B will tell you that the fuel used is 5.1. Add to that the 3 gallons for the takeoff and departure climb to get 8.1 gallons.
4. Due to the headwind, you decide to fly at 3000 ft instead. Recalculate the magnetic heading, ground speed, time en route, and fuel used.
Answer: 18°, 99 kts, 36 minutes, 7.1 gallons
In the Phone E6B aviation calculator, redoing the calculation is very simple. Simply move the cursor to the Wind Direction input area. (On most phones, you can do this by pressing the Up key until you get to the Wind Direction input area. On touchscreen phones, you may be able to get to the input area by touching or tapping the input area. Other phones may have a trackball that can be used to move up to the Wind Direction input area. Most phones will have a visual indicator that shows what input area is active. For example, the cursor may appear as a vertical line or rectangle on the screen. On other phones, the active input area will appear as a slightly different color. In Figure 1, the active input area has a light blue background and the cursor is a blue rectangle.) Change the Wind Direction to 290. (Your phone will have a key that can be used to delete characters. Alternatively, you can use the Delete command from the menu to delete the entire contents of the input area. On Blackberries, use the Clear Field command.) Then, change the Wind Speed to 7 kts. As soon as you make these changes, Phone E6B recalculates everything. Phone E6B will tell you that the true heading is 8°, ground speed is 99 kts, time is 36 minutes, and fuel used is 4.1 gallons. Therefore, the magnetic heading is 18°. Adding the time and fuel for takeoff and departure, the total time is 39 minutes and fuel used is 7.1 gallons.
5. Calculate the magnetic heading, ground speed, time en route, and fuel used for the return flight, assuming the same wind conditions as in the previous problem.
Answer: 206°, 101 kts, 39 min, 7.1 gal
Change the True Course to 192. Phone E6B instantaneously recalculates the heading, time en route, and fuel used. The magnetic heading is 206 and ground speed is 101 kts. Including the takeoff and departure allowance, the time 39 minutes and fuel used is 7.1 gallons.
6. You are flying a vintage biplane in which the Pilot's Operating Handbook (POH) and all the gauges are in MPH. Calculate the wind correction angle and magnetic heading needed to fly a magnetic course of 292° during the departure climb with true airspeed 70 MPH. Also, calculate the ground speed in knots and MPH. The METAR is
KABC 121845Z 24030KT 6SM SCT250 16/8 A3001Answer: WCA -23°, ground speed 41 MPH (38 kts)
The true airspeed is in MPH and the wind speed is in knots, but using mixed units in Phone E6B is easy. Press the phone's menu button and select the Reset command to clear all the input fields. You can use Phone E6B with a magnetic course instead of a true course. If you enter a magnetic course in Phone E6B, you must also enter a magnetic wind direction, and Phone E6B will output a magnetic heading. Enter 292 in the "True Course" input area (ignore the fact that it says "True".) To enter the true airspeed in MPH, go to the True Airspeed input area. Press the Menu button and select the Change Units command. Select mph and then enter 70. METARs give magnetic wind direction. Therefore, enter 240 as the wind direction and 30 kts as the wind speed. (The units for wind speed do not change when you change the True Airspeed to MPH.) Phone E6B will tell you that the wind correction angle (WCA) is -23, the heading is 269 (the heading is magnetic, not true, because you entered a magnetic course and magnetic wind direction), and ground speed is 38 kts. To convert the ground speed to MPH, move the cursor to the Ground Speed output area. Press the menu button, select the Change Units command, and select mph. Phone E6B will tell you that the ground speed is 41 MPH.
7. At a ground speed of 80 kts, how far can you travel in 6 hours and 30 minutes?
Answer: 520 NM
If you are still in the Wind Correction/Ground Speed calculator, press the escape button or select Exit from the menu in order to return to the Phone E6B main menu. From the main menu, select Time/Distance. Enter 80 kts for speed. Move the cursor to the time input area and enter "6:30". Phone E6B will tell you that the distance is 520 NM.
8. If you burn 6.8 gallons/hr, how much fuel would you use in 6 hours and 30 minutes?
Answer: 44.2 gal
From the Phone E6B main menu, select Fuel Burn. Enter "6:30" as the time and 6.8 gal/hr as the fuel burn rate. Phone E6B will tell you that the fuel used is 44.2 gallons.
9. How long can you fly if you have 65 gallons of fuel and burn fuel at 6.8 gal/hr?
Answer: 9 hr 34 min
Go to the fuel used input area and type in 65 (gal). Phone E6B will tell you that the time is 9 hours 34 minutes.
10. What effect, if any, does high humidity have on aircraft performance?
A. It increases performance
B. It decreases performance
C. It has no effect on performance
Phone E6B can calculate the effect of temperature and humidity on performance. You must remember that performance decreases when density altitude increases. From the Phone E6B main menu, select Density Altitude. Pick some arbitrary numbers for the pressure altitude and temperature. For example, let's use pressure altitude 1000 ft and temperature 25°C. Move the cursor to pressure altitude and enter 1000 and then enter 25 as the temperature. To see what the density altitude is when the relative humidity is 100%, set the dew point to the same value as the temperature (25°C in this example). Phone E6B will tell you that the density altitude is 2799 ft. To calculate the density altitude with no humidity, move the cursor to the Dew Point input area and select Use Dry Air from the Menu. (Alternatively, you could enter a very large negative number as the dew point, e.g. -100°C). Phone E6B will tell you the density altitude is 2385 ft. Therefore, density altitude increases when humidity increases. Therefore, high humidity decreases aircraft performance.
11. Which combination of atmospheric conditions will reduce aircraft takeoff and climb performance?
A. Low temperature and low relative humidity
B. Low temperature and high relative humidity
C. High temperature and high relative humidity
From the previous problem, we can rule out answer A. Now let's see what effect temperature has on density altitude. Picking up from where we left off in problem 10, change the temperature to 0°C. Phone E6B will tell you density altitude is -589 ft. Therefore, high temperature increases density altitude and therefore decreases performance. So, the correct answer is C.
12. Determine the density altitude for these conditions:
Altimeter setting 29.25" Hg Runway temperature 81°F Dew point 20°F Airport elevation 5250 ft MSL
Answer: 8620 ft
From the Density Altitude calculator, use the Reset command to clear all the fields. Enter 5250 as the Indicated Altitude, 29.25 as the Altimeter, 81 as the temperature, and 20 as the dew point. (Use the Change Units command if the units are not ft, in Hg, and °F.) Phone E6B will tell you that the density altitude is 8620 ft.
13. What is the effect of a temperature increase from 25 to 50°F on density altitude if the pressure altitude remains at 5000 ft and there is no humidity?
Answer: density altitude increases by 1663 ft
Enter 5000 as the pressure altitude and 25 as the temperature. Move the cursor to the dew point input area and from the menu, select Use Dry Air. Phone E6B will tell you the density altitude is 3913 ft. Then change the temperature to 50, and Phone E6B will tell you the density altitude is 5576 ft. Therefore, the temperature change increases density altitude by 5576-3913 = 1663 ft.
14. You have set your altimeter to the altimeter setting from the nearest weather reporting station. Which condition would cause the altimeter to indicate a lower altitude that actually flown (true altitude)?
A. Air temperature lower than standard
B. Atmospheric pressure lower than standard
C. Air temperature higher than standard
Using the correct altimeter setting takes care of altitude variation due to lower than standard atmospheric pressure, so B can be ruled out. To see what effect temperature has on true altitude, go to the Phone E6B density altitude calculator. Put in some arbitrary values for the indicated altitude, altimeter setting, and temperature, for example, indicated altitude 5000 ft, altimeter 29.92 in Hg, temperature 30°F, dew point -100°F (i.e. dry air). Press the Calc True Alt on-screen button and enter an arbitrary number for station altitude, for example 1000 ft. Then, change the Temperature to a larger value such as 60°F. In this example, Phone E6B will tell you the true altitude is 4911 ft when the temperature is 30°F and 5150 ft when the temperature is 60°F. Therefore, true altitude increases when the air temperature increases. Therefore, hotter than standard days, the indicated altitude is lower than the true altitude. So, C is the correct answer.
15. What is your true airspeed under these conditions:
Indicated altitude 10000 ft Altimeter 28.85 in Hg Temperature from the nearest weather reporting station 15°C Outside air temperature 5°C Relative humidity of the outside air 0% Indicated airspeed 135 kts Configuration flaps up, normal static sourceThe Pilot's Operating Handbook (POH) contains this table:
Answer: 155 kts
Go to the Phone E6B density altitude calculator and enter indicated altitude 10000 ft, altimeter 28.85'' Hg, and temperature 5°C. (The temperature of the nearest weather reporting station is irrelevant. The temperature and dew point that must be entered are for the air outside the airplane (OAT). The temperature would be measured by your plane's thermometer.) If the dew point input area is visible, move the cursor to it and choose Use Dry Air from the menu. Press the Calc TAS on-screen button. From the POH's table, we see that when the indicated airspeed is 135 kts, the calibrated airspeed is 129 kts, so enter 129 as the calibrated airspeed. Phone E6B will tell you that the true airspeed is 155 kts.
16. In the previous problem, what if you do not know the relative humidity of the outside air?
Answer: between 155 and 156 kts
In general, when flying, you do not know the humidity of the outside air. The nearest weather reporting station might give you a dew point, but that is the dew point at the altitude where the station is. The dew point at the altitude you are flying might be different. Nevertheless, you can calculate a range of values that the true airspeed might be, by calculating what the TAS would be with no humidity and what the TAS would be at 100% humidity. The actual TAS will be somewhere in that range. Press the Add Humdity on-screen button. To find the TAS at 100% humidity, set the dew point to the same value as the temperature (5°C). Phone E6B will tell you the TAS is 156 kts. Therefore the actual true airspeed is between 155 and 156 kts.
17. You want to land on runway 18. The tower reports that the wind is 220 at 30 knots. The POH says that the maximum demonstrated crosswind component for your plane is 25 kts. Is the crosswind lower than the maximum demonstrated crosswind component for your plane?
From the Phone E6B main menu, select Headwind/Crosswind. Enter 30 as wind speed and 40 (220 - 180 = 40) as the relative wind angle. Phone E6B will tell you that the crosswind is 19.3 kts. Therefore, the crosswind is lower than your plane's maximum demonstrated crosswind component.
18. In the previous problem, what is the (minimum) landing distance? The pressure altitude at the airport is 1000 ft, temperature is 10°C, your plane's gross weight is 1600 lbs and the POH contains this table:
1. Use the short field technique described in Section 4
2. Decrease the distances 10% for each 9 knots of headwind. Increase distances 10% for every 2 knots of tailwind
Answer: 417 ft
From the previous problem, Phone E6B tells you the headwind is 23 kts. The relevant entry from the table is ground roll 560 ft and the note says to decrease the distance by 10% for each 9 kts of headwind. Therefore, decrease the ground roll by 10% x 23/9 = 26%. Therefore the landing distance is 560 x (1-.26) = 417 ft.
19. An aircraft is loaded 110 pounds over maximum certified gross weight. If fuel is drained to bring the aircraft weight within limits, how much fuel should be drained?
Answer: 18.3 gal
From the Phone E6B main menu, select Convert Units. Select weight as the conversion type. Move the cursor to the Weight 1 input area. If "(lbs)" does not appear next to Weight 1, then change the units to lbs by selecting Change Units from the menu. Move the cursor to the Weight 2 input area. Select Change Units from the menu and choose "gal 100LL avgas @ std temp)". Phone E6B will tell you that Weight 2 is 18.27, which means that at standard temperature 18.27 U.S. gallons of 100LL avgas weighs 110 lbs. Therefore, the answer is 18.27 gallons (U.S.).
20. Calculate the weight, moment, and center of gravity.
Front seat passengers 340 lb Rear seat passengers 295 lb Fuel 44 gal Baggage 56 lbFrom the POH:
Empty weight - 2015 lbs, moment 155400 lb-in
Figure 2. Lengthy weight and balance calculations can be easily done on your phone - even if your phone has a small screen.
Picking up from the previous problem, type in 44 as Weight 2 (gallons of avgas) and Phone E6B will tell you that the avgas weights 264.88 lbs. Now use the Exit command from the menu to return to the Phone E6B main menu, and select Weight and Balance. Press the on-screen Add Item button (or select Add Item from the menu). For the empty weight, enter 2015 as weight and 155400 as the moment. You may enter "Empty weight" as the Name, but that is not required. Press the on-screen Enter button or select Enter from the menu. Press the Add Item button again. For the front passengers, enter weight 340 and arm 85. Press the on-screen Enter button. Repeat this process for the rear passengers, fuel, and baggage. (Use 264.88 as the weight for the fuel.) Phone E6B will tell you that the weight is 2970.88 lbs, center of gravity is 83.38, and moment is 247701 lb-in.
21. What would the weight, center of gravity, and moment be if the rear passenger were 120 lbs?
Answer: 2796 lbs, 81.02 in, 226526 lb-in
Move the cursor to the entry for rear passenger (the third item). Select Edit from the menu. Change the weight to 120 and press enter. The new weight is 2795.88 lbs, center of gravity is 81.02 in, and moment is 226526 lb-in.
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