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DGCA Technical General · 41 questions

Airspeeds: DGCA Technical General Questions and Answers

41 practice questions on Airspeeds with answers and explanations, plus the key concepts and formulas, from the TrueHeading question bank.

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About this topic

Use this page to revise Airspeeds for the DGCA Technical General paper. Below are the key ideas first, then 12 practice questions with answers and explanations, picked from the 41 questions in the TrueHeading bank for this topic.

In short: Corrections applied in order:

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Key concepts: Airspeeds

2 ideas to know cold.

IAS, CAS, EAS and TAS?

Corrections applied in order:

TAS=EASσ,σ=ρρ0TAS=\frac{EAS}{\sqrt{\sigma}},\qquad\sigma=\frac{\rho}{\rho_0}
  • IAS → CAS: instrument and position error
  • CAS → EAS: compressibility
  • EAS → TAS: density (altitude and temperature)
  • TAS ≈ CAS + 2 % per 1000 ft
IASindicatedCAScalibratedEASequivalentTAStrueinstrument+ position errorcompressi-bilitydensity(alt, temp)IAS → CAS → EAS → TASTAS ≈ CAS + 2 % per 1000 ft (rule of thumb)in ISA at sea level all four are equal at low speed

Describe the chain IAS → CAS → EAS → TAS.

IAS + position/instrument error = CAS. CAS − compressibility = EAS. EAS ÷ √σ = TAS.

TAS=EASσTAS=\dfrac{EAS}{\sqrt{\sigma}}
  • TAS ≈ CAS + 2 % per 1 000 ft (rule of thumb)
  • σ = density ratio
  • Mach = TAS / LSS

Practice questions: Airspeeds

Tap “Show answer” after you have tried each one.

Q1EAS is 150 kt at 5 000 ft in ISA (density ratio σ = 0.8617). The TAS is approximately (kt):

  1. 180
  2. 145
  3. 195
  4. 160
Show answer

Answer: D. 160

TAS = EAS / √σ = 150/√0.8617 ≈ 162 kt.

Q2EAS is 250 kt at 5 000 ft in ISA (density ratio σ = 0.8617). The TAS is approximately (kt):

  1. 290
  2. 255
  3. 305
  4. 270
Show answer

Answer: D. 270

TAS = EAS / √σ = 250/√0.8617 ≈ 269 kt.

Q3EAS is 200 kt at 10 000 ft in ISA (density ratio σ = 0.7385). The TAS is approximately (kt):

  1. 235
  2. 255
  3. 220
  4. 270
Show answer

Answer: A. 235

TAS = EAS / √σ = 200/√0.7385 ≈ 233 kt.

Q4EAS is 150 kt at 15 000 ft in ISA (density ratio σ = 0.6292). The TAS is approximately (kt):

  1. 190
  2. 210
  3. 175
  4. 225
Show answer

Answer: A. 190

TAS = EAS / √σ = 150/√0.6292 ≈ 189 kt.

Q5EAS is 250 kt at 15 000 ft in ISA (density ratio σ = 0.6292). The TAS is approximately (kt):

  1. 350
  2. 335
  3. 300
  4. 315
Show answer

Answer: D. 315

TAS = EAS / √σ = 250/√0.6292 ≈ 315 kt.

Q6EAS is 200 kt at 20 000 ft in ISA (density ratio σ = 0.5328). The TAS is approximately (kt):

  1. 275
  2. 310
  3. 295
  4. 260
Show answer

Answer: A. 275

TAS = EAS / √σ = 200/√0.5328 ≈ 274 kt.

Q7EAS is 200 kt at 25 000 ft in ISA (density ratio σ = 0.4481). The TAS is approximately (kt):

  1. 320
  2. 285
  3. 300
  4. 335
Show answer

Answer: C. 300

TAS = EAS / √σ = 200/√0.4481 ≈ 299 kt.

Q8EAS is 150 kt at 30 000 ft in ISA (density ratio σ = 0.3750). The TAS is approximately (kt):

  1. 245
  2. 230
  3. 280
  4. 265
Show answer

Answer: A. 245

TAS = EAS / √σ = 150/√0.3750 ≈ 245 kt.

Q9EAS is 250 kt at 30 000 ft in ISA (density ratio σ = 0.3750). The TAS is approximately (kt):

  1. 395
  2. 410
  3. 430
  4. 445
Show answer

Answer: B. 410

TAS = EAS / √σ = 250/√0.3750 ≈ 408 kt.

Q10EAS is 200 kt at 35 000 ft in ISA (density ratio σ = 0.3099). The TAS is approximately (kt):

  1. 360
  2. 395
  3. 380
  4. 345
Show answer

Answer: A. 360

TAS = EAS / √σ = 200/√0.3099 ≈ 359 kt.

Q11EAS is 150 kt at 40 000 ft in ISA (density ratio σ = 0.2462). The TAS is approximately (kt):

  1. 335
  2. 300
  3. 320
  4. 285
Show answer

Answer: B. 300

TAS = EAS / √σ = 150/√0.2462 ≈ 302 kt.

Q12EAS is 250 kt at 40 000 ft in ISA (density ratio σ = 0.2462). The TAS is approximately (kt):

  1. 525
  2. 505
  3. 490
  4. 540
Show answer

Answer: B. 505

TAS = EAS / √σ = 250/√0.2462 ≈ 504 kt.

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