GEN 16: Rate of Descent

📄 Detailed Notes⚡ Cheat Sheet
 

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📄 Notes ⚡ Cheat Sheet
📄 Notes ⚡ Cheat Sheet

Q1. Given: aircraft height 2500 FT, ILS GP angle 3 deg. At what approximate distance from THR can you expect to capture the GP?

8.3 NM –

  • Formula: Distance (NM) = Height (ft) / 300 (approximation for 3 degree slope).
  • Calculation: 2500 / 300 = 8.33 NM.

    • Q2. An aircraft is on an ILS 3-degree glideslope, which passes over the runway threshold at a height of 50 feet. The DME range is 25 nm from the threshold. What is the height above the runway threshold elevation? (Use the 1 in 60 rule and the approximation 6000 feet = 1 nautical mile)

    7550 feet. –

  • Height = (Distance * Angle * 100) + Threshold Height.
  • Height = (25 * 3 * 100) + 50 = 7500 + 50 = 7550 ft.

    • Q3. Convert 80 meters/ second into knots?

    155 kts –

  • Conversion factor: 1 m/s approx 1.94 knots.
  • 80 * 1.94 = 155.2 kts.

    • Q4. An aircraft at FL390 is required to descend to cross a DME facility at FL70. Maximum rate of descent is 2500 FT/MIN, mean GS during descent is 248 kt. What is the minimum range from the DME at which descent should commence?

    53 NM –

  • Altitude loss = 390 – 70 = 320 (32,000 ft).
  • Time to descend = 32,000 / 2500 = 12.8 mins.
  • Distance = GS * Time / 60 = 248 * 12.8 / 60 = 52.9 NM.

    • Q5. Given: TAS=197 kt, True course = 240 deg, W/V=180/30kt. Descent is initiated at FL 220 and completed at FL 40. Distance to be covered during descent is 39 NM. What is the approximate rate of descent?

    1400 FT/MIN –

  • Calculate GS: Wind angle 60 deg off nose. Headwind approx 15 kts. GS approx 182 kts.
  • Altitude loss = 18,000 ft. Time = Dist / GS = 39 / 182 = 0.214 hrs = 12.8 mins.
  • ROD = 18,000 / 12.8 = 1406 ft/min.

    • Q6. An aircraft at FL 290 is required to commence descent when 50 NM from a VOR and to cross the VOR at FL80. The mean GS during descent is 271 kt. What is the minimum rate of descent required?

    1900 FT/MIN. –

  • Time available = 50 / 271 * 60 = 11.07 mins.
  • Altitude to lose = 21,000 ft.
  • ROD = 21,000 / 11.07 = 1896 ft/min.

    • Q7. An aircraft at FL370 is required to commence descent at 120 NM from a VOR and to cross the facility at FL130. If the mean GS for the descent is 288 kt, the minimum rate of descent required is:

    960 FT/MIN –

  • Time = 120 / 288 * 60 = 25 mins.
  • Alt loss = 24,000 ft.
  • ROD = 24,000 / 25 = 960 ft/min.

    • Q8. An aircraft at FL370 is required to commence descent when 100 NM from a DME facility and to cross the station at FL120. If the mean GS during the descent is 396 kt, the minimum rate of descent required is approximately:

    1650 FT/MIN –

  • Time = 100 / 396 * 60 = 15.15 mins.
  • Alt loss = 25,000 ft.
  • ROD = 25,000 / 15.15 = 1650 ft/min.

    • Q9. An aircraft is descending down a 12% slope whilst maintaining a GS of 540 kt. The rate of descent of the aircraft is approximately:

    6500 FT/MIN –

  • Formula: ROD (ft/min) = Groundspeed (kts) * Gradient (%) * 1.013.
  • Rough Calc: 540 * 12 = 6480. Closest answer 6500.

    • Q10. What will be the rate of descent when flying down a 4 degree glide slope, at a ground speed of 200 knots?

    1350 ft/min. –

  • Formula for 3 deg is 5 * GS. For 4 deg it is (4/3) * 5 * GS.
  • Calc: (20/3) * 200 = 1333 ft/min. Closest is 1350.

    • Q11. Assuming zero wind, what distance (in NM) will be covered by an aircraft descending 15000 FT with a TAS of 320 kt and maintaining a rate of descent of 3000 FT/MIN?

    27 –

  • Time = 15,000 / 3000 = 5 mins.
  • Distance = 320 * (5/60) = 26.6 NM. Rounds to 27.

    • Q12. What will be the rate of descent when flying down a 10% glide slope, at a ground speed of 350 knots?

    3545 ft/min. –

  • Formula: ROD = GS * Gradient * 1.013.
  • Calc: 350 * 10 * 1.013 = 3545.5.

    • Q13. Given: ILS GP angle = 3.5 DEG, GS=153 kt. What is the approximate rate of descent?

    900 FT/MIN –

  • Calc: 5 * 153 * (3.5/3) = 892 ft/min. Rounds to 900.

    • Q14. An aircraft at FL350 is required to descend to cross a DME facility at FL80. Maximum rate of descent is 1800 FT/MIN and mean GS for descent is 276 kt. The minimum range from the DME at which descent should start is:

    69 NM –

  • Alt loss = 27,000 ft. Time = 27,000 / 1800 = 15 mins.
  • Dist = 276 * (15/60) = 69 NM.

    • Q15. If there is a 20-knot increase in headwind by what amount must the rate of descent be changed in order to maintain a 3 degree glideslope?

    It must be decreased by 100 ft/min. –

  • Increased headwind reduces Groundspeed. Since ROD for a fixed angle is proportional to GS (5 * GS), a lower GS requires a lower ROD.
  • Change = 5 * 20 = 100 ft/min.

    • Q16. If there is a 17 knot decrease in headwind by what amount must the rate of descent be changed in order to maintain a 3 Degree glideslope?

    It must be increased by 85 ft/min. –

  • Decreased headwind increases Groundspeed. Higher GS requires higher ROD.
  • Change = 5 * 17 = 85 ft/min.

    • Q17. By what amount must you change the rate of descent to maintain a 3 degree glideslope if you meet an increase in headwind of 10 knots?

    50 feet per minute decrease. –

  • Increased headwind reduces GS. ROD must decrease.
  • Change = 5 * 10 = 50 ft/min.

    • Q18. A descent is planned from 7500 ft MSL so as to arrive at 1000 ft MSL 6 NM from a VORTAC. With a GS of 156 kts and a rate of descent of 800 ft/min The distance from the VORTAC when descent is started is:

    27.1 NM –

  • Alt loss = 6500 ft. Time = 6500 / 800 = 8.125 mins.
  • Dist flown = 156 * (8.125/60) = 21.1 NM.
  • Total Dist = 21.1 + 6 = 27.1 NM.

    • Q19. At 0800 an aircraft at FL350, GS 300kt, is on the direct track to VOR ‘X’ 150 NM distant. The aircraft is required to cross VOR ‘X’ at FL50. For a mean rate of descent of 1500 FT/MIN at a mean GS of 220 kt, the latest time at which to commence descent is:

    0815 –

  • Desc Time = 30000/1500 = 20 mins. Desc Dist = 220 * (20/60) = 73.3 NM.
  • Cruise Dist = 150 – 73.3 = 76.7 NM. Cruise Time = 76.7 / 300 = 15.3 mins.
  • Start Time = 0800 + 15 mins = 0815.

    • Q20. You are homing to overhead a VORTAC and will descend from 7500 QNH to be 1000 AMSL by 6 NM DME. Your ground speed is 156 knots and the ROD will be 1000 feet/min. At what range from the VORTAC do you commence the descent?

    22.9 NM –

  • Alt loss = 6500 ft. Time = 6.5 mins. Dist = 156 * (6.5/60) = 16.9 NM.
  • Start Range = 16.9 + 6 = 22.9 NM.

    • Q21. At 0422 an aircraft at FL370, GS 320kt, is on the direct track to VOR ‘X’ 185 NM distant. The aircraft is required to cross VOR ‘X’ at FL80. For a mean rate of descent of 1800 FT/MIN at a mean GS of 232 kt, the latest time at which to commence descent is:

    0445 –

  • Desc Time = 29000/1800 = 16.1 mins. Desc Dist = 232 * (16.1/60) = 62.3 NM.
  • Cruise Dist = 185 – 62.3 = 122.7 NM. Cruise Time = 122.7 / 320 = 23 mins.
  • Start Time = 0422 + 23 = 0445.

    • Q22. An aircraft is cruising at FL350, Temp -50 C and is told to descend to FL80, Temp -10 C. If the IAS for the descent was 188 kt, what would be the appropriate TAS ?

    260 kt –

  • Mean Altitude 21,500 ft. Mean Temp -30C. TAS increases approx 2% per 1000ft.
  • 188 * 1.43 approx 268 kts. 260 is the closest option.

    • Q23. A ground clearance of 20 Nm is necessary for an aircraft to ascend 6000 feet immediately after take-off in a no-wind situation at a TAS of 200 knots. With a headwind of 30 knots, the required ground clearance would be?

    17 –

  • Climb time in no wind = 20/200 = 0.1 hr (6 mins).
  • With 30kt HW, GS = 170. Time to climb 6000ft is still 6 mins.
  • New Dist = 170 * 0.1 = 17 NM.

    • Q24. An aircraft has to climb from FL50 -10 C to FL260 -25 C. The IAS for the climb is 180 kt and the WC is +30 kt. If the ROC is 900 ft/min, how many miles will the climb take?

    106 NM –

  • Climb 21,000 ft @ 900 fpm = 23.33 mins.
  • Mean TAS calculation (using 2/3 rule provided in source) = 241 kts. GS = 241 + 30 = 271 kts.
  • Distance = 271 * (23.33/60) = 105.3 NM.

    • Q25. An aircraft is can maintain maximum climb rate of 2000 feet per minute with mean GS of 230 knots. How much ground clearance is required to climb up 6000 feet ?

    11.5 –

  • Time = 6000 / 2000 = 3 mins.
  • Distance = 230 * (3/60) = 11.5 NM.

    • Q26. Given: aircraft height 2500 FT, ILS GP angle 3 deg. At what approximate distance from THR can you expect to capture the GP?

    8.3 NM –

    • Formula: Distance (NM) = Height (ft) / 300 (approximation for 3 degree slope).
    • Calculation: 2500 / 300 = 8.33 NM.

    Q27. At what approximate distance from the threshold would an aircraft intercept the glide path if the aircraft height is 2500 feet, and the ILS glide path angle is 3º?

    Q28. Convert 70 metres/second into knots?

    Q29. If there is a 10 knot increase in headwind by what amount must the rate of descent be changed in order to maintain a 3º glideslope?

    Q30. What will be the rate of descent when flying down a 12% glide slope, at a groundspeed of 540 knots?

    Q31. An aircraft flying down a 3″ ILS glideslope is at 25 nm DME from the threshold. Using the 1 in 60 rule and approximating 1 am to 6000 ft, calculate the aircraft height above the runway threshold, assuming that the ILS glidepath crosses the threshold at a height of 50 ft?

    Q32. 730 FT/MIN equals?

    Q33. If there is a 15 knot increase in headwind by what amount must the rate of descent be changed in order to maintain a 3º glideslope?

    Q34. What will be the rate of descent when flying down a 10º glide slope, at a groundspeed of 500 knots?

    Q35. An aircraft at FL370 is required to commence descent when 100 NM from a DME facility and to cross the station at FL120. If the mean GS during the descent is 396 kt, the minimum rate of descent required is approximately?

    Q36. An aircraft is descending down a 12% slope whilst maintaining a GS of 540 kt. The rate of descent of the aircraft is approximately?

    Q37. If there is a 25 knot increase in headwind by what amount must the rate of descent be changed in order to maintain a 3º glideslope?

    Q38. What will be the rate of descent when flying down a 5% glide slope, at a groundspeed of 450 knots?

    Q39. An aircraft is maintaining a 5.2% gradient is at 7 NM from the runway, on a flat terrain. Its height is approximately?

    Q40. If there is a 10 knot decrease in headwind by what amount must the rate of descent be changed in order to maintain a 3º glideslope?

    Q41. What will be the rate of descent when flying down a 8% glide slope, at a groundspeed of 400 knots?

    Q42. An aircraft at FL350 is required to commence descent when 85 NM from a VOR and to cross the VOR at FL80. The mean GS for the descent is 340 kt. What is the minimum rate of descent required?

    Q43. If there is a 15 knot decrease in headwind by what amount must the rate of descent be changed in order to maintain a 3º glideslope?

    Q44. The equivalent of 70 m/sec is approximately?

    Q45. What will be the rate of descent when flying down a 10% glide slope, at a groundspeed of 350 knots?

    Q46. An aircraft at FL330 is required to commence descent when 65 NM from a VOR and to cross the VOR at FL100. The mean GS during the descent is 330 kt. What is the minimum rate of descent required?

    Q47. If there is a 20 knot increase in headwind by what amount must the rate of descent be changed in order to maintain a 3º glideslope?

    Q48. Assuming zero wind, what distance is covered by an aircraft descending 15000 FT with a TAS of 320 kt and maintaining a rate of descent of 3000 FT/MIN?

    Q49. What will be the rate of descent when flying down a 7% glide slope, at a ground speed of 250 knots?

    Q50. An aircraft at FL370 is required to commence descent at 120 NM from a VOR and to cross the facility at FL130. If the mean GS for the descent is 288 kt, the minimum rate of descent required is?

    Q51. If there is a 20 knot decrease in headwind by what amount must the rate of descent be changed in order to maintain a 3º glideslope?

    Q52. Given: Aircraft height 2500 FT, ILS GP angle 3º. At what approximate distance from THR can you expect to capture the GP?

    Q53. What will be the rate of descent when flying down a 12% glide slope, at a groundspeed of 240 knots?

    Q54. Given: ILS GP angle = 3.5 DEG, GS = 150 kt. Approximate rate of descent is?

    Q55. If there is a 17 knot decrease in headwind by what amount must the rate of descent be changed in order to maintain a 3º glideslope?

    Q56. An aircraft at FL350 is required to descend to cross a DME facility at FL80. Maximum rate of descent is 1800 FT/MIN and mean GS for descent is 276 kt. The minimum range from the DME at which descent should start is?

    Q57. An aircraft at FL390 is required to descend to cross a DME facility at FL70. Maximum rate of descent is 2500 FT/MIN, mean GS during descent is 248 kt. Minimum range from the DME at which descent should commence is?

    Q58. What will be the rate of descent when flying down a 8% glide slope, at a groundspeed of 340 knots?

    Q59. An aircraft at FL350 is required to cross a VOR/DME facility at FL 110 and to commence descent when 100 NM from the facility. If the mean GS for the descent is 335 kt, the minimum rate of descent required is?

    Q60. Given: TAS = 197 kt, True course = 240°, W/V = 180/30kt. Descent is initiated at FL 220 and completed at FL 40. Distance to be covered during descent is 39 NM. What is the approximate rate of descent?

    Q61. By what amount must you change the rate of descent to maintain a 3º glideslope if you meet an increase in headwind of 10 knots?

    Q62. What will be the rate of descent when flying down a 12% glide slope, at a groundspeed of 150 knots?

    Q63. When 65 nm from a VOR you commence a descent from FL330 with the intention of arriving at the VOR at FL100. What rate of descent is required if your mean ground speed is 240 knots?

    Q64. What is the rate of descent on a 12% glide slope if groundspeed is 540 knots?

    Q65. What will be the rate of descent when flying down a 12% glide slope, at a groundspeed of 175 knots?

    Q66. At 100 nm from a VOR an aircraft commences a descent from FL330 in order to arrive overhead the VOR at FL100. What rate of descent is required if the mean groundspeed in the descent is to be 240 knots?

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