Mountain Airport Airfield Parameters Obstacle Distance in Nautical Miles from In

Question

Mountain Airport Airfield Parameters Obstacle Distance in Nautical Miles from Interpolate to NEXT HIGHEST 1,000' 6076 ft per Field Elevation Obstacle Initial Height Ft. Runway nautical AGL Selected Runway (highest will Next higher be 11,000')1,000' DA Position mile Single engine Airliner 6000 ft 6000 ft 3000 ft 6000 ft 30,380 30,380 2900 Station Pressure Corrected to Sea- AirportThumb Level Sufficient Aircratft (38°F ST) Altitude at Sufficient Climb Runway Rate to Distance of Temperature Temperature Airport in degree:s Takeoff AircraftLength for Clear in degrees Station Fahrenheit Pressure Pressure Altitude Altitude Altitude Pressure Density Density Chart Rate Takeoff? Obstacle? Obstacle Obstacle Aircraft Type Celsius Distance of Climb (Yes/No) (Yes/No) after T/OHt 6000 6000 7000 7000 8000 6000 6000 6000 7000 7000 8000 7800 8008 10123 9380 10448 10799 8008 9087 10123 9380 10448 10799 9000 11000 10000 11000 11000 9000 10000 11000 10000 11000 11000 Single engine Single engine Single engine 1950 1200 1200 1200 1200 2900 2900 2900 2900 2900 2900 Airliner Airliner Airliner In the article you read, when talking about the density altitude rule of thumb the author states that "(usually any error will be less than 300 feet)." Is the statement accurate based on your calculations? Why? 68-38 = 30F * 600/10-1800ft 86-38 = 48F * 600/10-2880ft 104-38 = 66F * 600/10-3960ft Standard Temp at Elev Elevation ft * 3.5°F/1000dT; 59"F-dT = St Temp @ elevat.on DA ROT: 10°F T St Temp. Add 600 ft to PA

Explanation / Answer

The pressure altitude which is corrected for non standard variations in temperature is known as density alitude. Density altitude is important factor in calculating performance of aircraft as well as engine. High density altitude means that the density of the air is reduced which has an adverse impact on the performance of the aircraft. To determine the density altitude there is a rule of thumb that for every 10 degree above or below the standard temperature, add or subtract 600 feet to the field elevation. Then multiply field elevation( in 100s of feet by 3.5 degree and then subtract from standard sea level temperature

Density altitude in feet= pressure altitude( in feet)+120*(OAT-IAS temperature)

OAT= outside air temperature( in degree celsius)

ISA=standard temperature( in degree celsius)

Standard temperature is 15 degree celsius at sea level and reduces by about 2 degree celsius or 3.5 degree fahreinheit/1000 feet altitude above sea level.

Calculations:

Elevation( ft)*3.5/1000ft=dT

Elevation=6000 feet( for single engine)

6000*3.5/1000=dT

21000/1000=dT

21=dT

21 degree fahreinheit

Now, standard temperature at elevation

59 degree Faheinheit-dT= standard temperture at elevation

59-21=standard temperature at elevation

38 degree faheinheit

Now,

Density altitude=Pressure alitude in feet+120*(OAT-ISA temperature)

Pressure altitude=6000 feet( given)

standard temperature=38 degree fahreinheit=3.3degree celsius( calculated from above)

OAT= outside air temperature=20 degree celsius( given)

Now, density altitude=6000+120*(20-3.3)

6000+120*16.7

6000+2004=8004

Error=calculated density altitude-observed density altitude

=8004-8008=4 feet

Similarly when OAT=40 degree celsius

Then density altitude

6000+(120*(40-3.3)

6000+(120*36.7)

=6000+4404

=10404

Error=calculated value of density altitude - observed value of density altitude

=10404-10123=281feet

therefore based on these calculations the error in density altitude is less than 300 feet

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