Airspeed Determination Givens: Altitude: FL310 (31,000 ft Pressure Altitude) Ind

Question

Airspeed Determination

Givens:

Altitude: FL310 (31,000 ft Pressure Altitude)

Indicated Airspeed: 250 KIAS

Indicated Outside Air Temperature (IOAT) or Total Temperature: -30 deg C

Figure 2.1 for Atmosphere

Figure 3.1 Position Errors

Figure 3.2 Compressibility Errors

Figure 11.2 or Tt = Ta (1 + .2M2) Temperature Ram Rise

1. Find CAS (Calibrated Airspeed in kts).

2. Find EAS (Equivalent Airspeed in kts).

3. Find Pressure Ratio: .

4. Find Mach.

5. Find Actual Outside Air Temperature (ambient temperature).

6. Find Temperature Ram Rise.

7. Find Density Ratio: .

8. Find TAS, True Airspeed in kts.

9. If you are landing into an airfield in mountainous terrain at a field elevation of 3,000 ft

MSL (Mean Sea Level) and the field outside air temperature is -24 deg C, according to

AC 91-XX Draft Appendix 2, how should you adjust your approach arrival procedures

with a Final Approach Fix (FAF) at 5,000 ft MSL and your Minimum Descent Altitude

(MDA) at 3500 ft MSL?

Explanation / Answer

now that this poor chap has become totally confused allow me an attempt, MSL is the published elevation of the airport above sea level, for instance if the published airport elevation is 560 then your altimeter ( used to determine your altitude while flying ) will if calibrated correctly read 560 when the altimeter is set to the correct current barometric pressure. Standard pressure is considered 29.92. As pressure variations exist over broad areas, this setting is updated from time to time to ensure that you are getting a correct reading now read as altitude above MSL. AGL is the difference between the MSL displayed altitude and the actual terrain elevation. In a hypothetical situation if you are flying at an altitude of 5,000 feet MSL over terrain that rises from say 600 feet MSL to say 3,000 feet MSL then you can see that your actual altitude AGL will become lower as you fly into rising terrain. Aeronautical charts (low level) will show obstacles heights such as radio towers as above ground level. Aircraft flying above 18,000 feet msl use the standard 29.92 altimeter setting for the portion of flight at or above 18,000 feet. Most airports have a sensitive altimeter and can tell you the current barometric pressure, if that information is unavailable the pilot sets the altimeter to the known field elevation and reads the corresponding pressure. This information along with temperature is important in calculating aircraft performance from tables and graphs which are derived from standard 29.92 inches 59 degrees f. enroute aircraft obtain updated altimeter settings from ground stations in close proximity to their position. As you can see AGL altitude varies constantly as the aircraft proceeds on course therefore the only constant is MSL which is important information when working in and around controlled airspace or providing traffic separation clearance enroute. I know it's not the simplest of explanations, but it is important the you understand the relevance especially if you are learning to fly. Have your instructor spend some time with you utilizing a sectional chart.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.