| Cross Country Questions |
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1) A flat bottomed cumulus cloud with sharp edges
a) is a reliable indication of thermal lift A - Cumulus is good. It indicates instability in the air (lift). |
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2) A spread out, shallow layer of cloud
a) is a reliable indication of thermal lift C - Shallow layers of clouds (Stratus) indicate stable conditions. |
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3) Best L/D speed would be the best to fly when
a) thermaling D - When flying in calm air or a crosswind, we need to use the best L/D speed to get the maximum distance for loss of altitude |
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4) Best L/D speed plus ½ the estimated wind speed would be the best speed to fly when
a) thermaling B - When flying into a headwind, we want increase our speed to minimize the time that the wind is acting on us. |
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5) When thermaling, the best speed to fly is
a) Best L/D speed d) minimum sink speed for the angle of bank being flown D - When we're thermaling, we're looking for the least loss of altitude over time. The glider is always descending. Flying the minimum sink speed allows the least loss of altitude, which provides us with the maximum rate of climb in the thermal. The best L/D speed comes into play when we want to get the maximum distance versus altitude loss. |
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6) Minimum sink speed would be the best speed to use for
a) flying through thermals with no intention of stopping to circle |
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7) What performance factor is recommended for beginning cross country pilots when planning safe decision points? a) Best L/D glide ratio
b) ½ best L/D glide ratio B - The listed L/D for an aircraft by the factory is often optimistic, and are based on a perfect plane. Add the effects of a rough surface (bugs, scratches, etc.), and the L/D decreases, even with the perfect pilot flying it at exactly the proper speeds. Now add in the performance lost through speed variance, etc. by the average pilot, and you can see why you plan for lower performance when beginning cross country flying. After gaining experience, you can increase the planned L/D. |
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8) To assure landing at an airport at anytime on a cross country flight, a pilot should a) plan decision points
b) fly the best L/D speed A - Although you need to adhere to "B" and "C", they just get you the maximum distance. It doesn't do any good if the next airport is only 10 miles away, you're at 3,000 feet AGL, a realistic 20:1 L/D at 50 knots, 20 knot headwinds, and no lift. If you reverse course and head to an airport that's 10 miles away, can you make it? Remember, we're learning cross country flying. You don't need the additional pressure of worrying if you can make the next point. You'll have enough to worry about with navigation, etc.You're not in a race! At least not yet. |
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9) When determining safe decision points:
a) plan to arrive over airports at a minimum altitude of 1000 AGL C - We've already discussed using 1/2 of the best L/D speed for initial cross planning last time. You need to plan to arrive over the airport at a minimum of 1,000 AGL to provide a margin of safety and to allow a normal traffic pattern. |
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10) When flying cross country, at a minimum altitude of 3000 AGL you should
a) select a specific landing area(s) c) select a general landing area(s) C - Even if you're thousands of feet high, you always need to be looking for general landing areas. You never know when something may happen that would require you to discontinue your flight, and need to always have a plan available. By the time you're down to 3,000 AGL, you need to select a general landing area, and insure you can reach it. |
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11) When flying cross country at a minimum altitude of 2000 AGL you should
a) select a specific landing area(s) A - Remember, at 3,000 AGL you should have a general landing area picked. As you get lower, you need to lock down a landing area. |
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12) When flying cross country at a minimum altitude of 1000 AGL you should a) select a specific landing area(s)
b) be on the upwind leg of a specific landing area |
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13) When flying cross country with a specific landing area chosen, an alternate landing area should be within easy reach in case of discovering a hazard as low as?
a) 500 - 1000 AGL B - While moving toward the specific landing site we are planning on using, we should be looking for alternate sites. As we approach our specific selected landing area, we need to start check the landing site for hazard. If we discover a hazard above 1,200 AGL, we should be able to divert to the alternate site, and still be able to fly a normal pattern. Obviously, this is perfect landout solution. Remember, at this point we're not trying fly a race. Plan and fly your decision points, and you should have airfields to land at. |
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14) Prior to takeoff on a cross country flight, the altimeter should read?
a) zero B - Altimeters should always be set to the field elevation before flying cross country. That will give you your altitude above sea level (MSL). Sectional charts show elevations in MSL. It is easy to subtract the surface elevation (MSL) from the indicated altitude (MSL), to obtain your height above ground (AGL). Some pilots set their altimeters to "0". That's fine if you are flying local and landing at the same field. Density altitude is pressure altitude adjusted for temperature and humidity. It doesn't help tell us how high above the ground we are. Density altitude does effect the aircraft performance. |
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15) During a cross country flight he altimeter should read height above
a) ground level D - Setting the altimeter to display altitude above sea level, allows you to easily compute altitude above ground level by subtracting the elevation from the sectional from the indicated altitude. |
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16) How many statue miles will a glider with a 39:1 glide ratio travel for each 1,000 feet of altitude loss?
a) 30 miles |
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17) How many statute miles will a glider with a 30:1 glide ratio at 50 mph travel for each 1,000 feet of altitude loss with a 10 mph headwind
a) 4.1 miles B - Last time we discussed how to compute how far we would travel with a 30:1 L/D with each 1,000 feet of altitude loss. The answer was 5.7 miles. Computing the effect of wind, is simply a ratio problem. An easy way to compute this in your head is to say that the new ground speed is 40 MPH (50 MPH for best L/D - 10 MPH headwind). 40 is 80% of 50. Multiply the distance in still air by the headwind factor (5.7 X .8), and we get 4.5 miles. For practice, try computing the effect of a 10 MPH tail wind. How many miles can you go? Do you see that a simple change in direction from a small 10 MPH headwind to a small 10 MPH tailwind, can make a 40% difference in the distance you are able to travel? |
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18) How much altitude will a glider with a 30:1 glide ratio lose while traveling one statue mile in still air?
a) 300 feet |
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19) In calm winds, 20 statute miles from the airport, in a glider with a 30:1 glide ratio at 50 mph, how high do you need to be to arrive over the airport at 1000' AGL? Airport elevation is 800' MSL. Assume no safety factor. Assume pilot flies at 50 mph.
a) 3500 MSL C - To obtain the altitude needed to cover a distance, you divide the distance by the glide ratio, and adjust it for speed. To do the math, we need to convert values to similar units. In this case the distance is 20 miles or 105,600 feet (20 miles * 5,280 feet per mile). The L/D is 30, so the altitude needed is 3,520 feet (105,600 / 30). Add the airport elevation and the safety margin for the traffic pattern (800 + 1000) to the altitude needed to make the distance(3,520), and you find you need to be at least 5,320 feet MSL to make it to the airport safely. There are many other ways to solve the problem, including electronic flight computers and the old E6B wiz wheel. You can also do a close approximation in your head. With a 30:1 ration, we lose 1 mile of altitude to cover 30 miles on the ground. 20 miles is 2/3 of that 30 miles, therefore we'll lose 2/3 of a mile to cover that distance. By rounding off that mile (5280 feet) to 5,400, you may be able to do the division in your head. An E6B wiz wheel is nothing more than a circular slide rule. If you can't do math in your head, an E6B or a small electronic calculator is cheap. You don't need a fancy flight computer to obtain that final glide number. |
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20) With a 10 mph headwind, 15 statute miles from the airport, in a glider with a 30:1 glide ratio at 50 mph, how high do you need to be to arrive 1000' AGL at the airport? Airport elevation is 800 MSL. Assume no safety factor. Assume pilot flies at 50 mph.
a) 3300 MSL B - We just completed a similar problem in #19. The difference now is we need to apply correction for the head wind. Let's calculate what we need in still air. You know the formula (15 * 5,280 / 30). We find we need 2,640 feet in still air. However, we have a head wind that's decreasing our performance. To find out how much, divide the best L/D speed by the wind, and we get the percentage our performance decreases. Here we have 50 divided by 10, for a decrease of 20%. To say it another way, we're only getting 80% of what we could get in still air. Take the value in still air and divide by that factor for the needed altitude (2,640/.80 = 3,300). Add the airport elevation and safety margin (800 + 1,000) to the altitude needed to make the distance (3,300), and you find you need to be at least 5,100 feet MSL to make it to the airport safely. Want to try it in your head? 15 miles is half of the 30 miles you could go from a mile (5,280 feet) high. That's 2,640 feet. The wind is effecting the distance you travel by 20% (50 / 10), therefore we need another 20% altitude. The money we would spend for the GPS and flight computer is looking better all the time! |