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2011年8月4日星期四

Can a student pilot fly with a density altitude?

-I'm a little confused. if the ASOS at an airport is telling me the temp is 26 degrees celcius, and the density altitude is 1,200..can i still fly over there? its in the desert,, but the airport is 100 ft under sea level. its gusting over there at 17kts too..my instructor would totally let me go, but rules state a student pilot can't.



your opinion?Density altitude is what it sounds like. It's how "Dense" the air is. If the ASOS is reporting a Density altitude of 1,200 ft. that means the airplane, on departure, is going to perform essentially like an airport at 1200 MSL, instead of one at -100MSL. The airplane will perform more poorly due to density altitude. That said, a density altitude of 1200 isn't something you should probably worry about realistically.



I presume the winds are the primary factor in saying you can't go? Generally school rules are rules due to insurance requirements. If you ignore them, or fly outside of the envelope of rules, your insurance is probably as good as void for the flight.
The wind is the only limiting factor really. 1,200' density altitude is nothing. Lots of students have trained from airports over a mile high.
Yes, that is nothing and very common in many areas during the summer. Go to an airport in AZ and you'll see density alt upwards to 5,000- that is when you better have a good plan and plenty of runway. Also landing in the mountains, like in CO is the same scenario, you may not have an official density altitude reported, but the air is so thin that performance is reduced.



All density altitude does is change the airplane's performance to the particular Daltitude reported. The higher you go, the less air the airfoils and the engine have to grab a hold of. Check the POH, which you should be familiar with, and see how the performance is reduced...it won't be by much in your case.



Now keep in mind though that with higher density altitudes (3000' +), you may want to approach higher in airspeed than normal because the plane will want to settle faster, the best case is that it is a harder than normal landing. Then you should always take into consideration of the XW factor, which will be about 9 kts added...you'll be coming in quickly.



If you've performed well so far, your instructor should allow it unless the owners of the a/c have placed their own rules. It may actually be due to the gust factor that he's talking about, I would not let a first time solo student go into a gust factor higher than 10 Kts or a substantial crosswind component...they do require the pilot to be a little more sharp and ready to go-around or abort the landing. At your stage, you may not have the necessary training for such conditions, it all takes time.

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