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Ground Effect In High Density Altitude  
User currently offlineModesto2 From United States of America, joined Jul 2000, 2801 posts, RR: 5
Posted (8 years 9 months 2 weeks 6 days 21 hours ago) and read 3035 times:

How does ground effect change at a high altitude and hot temperature situation compared to standard conditions at sea level? At a high density altitude, will the ground effect be more or less pronounced and why?

4 replies: All unread, jump to last
 
User currently offlineLehpron From United States of America, joined Jul 2001, 7028 posts, RR: 21
Reply 1, posted (8 years 9 months 2 weeks 6 days 21 hours ago) and read 3018 times:

Hmm, subsonic ground effect theory relates the wingspan (or width) of a plane and the height above ground level. The factor calculated multiplies into the induced drag, which is produced by lift as some velocity.

I would suppose that if the air was thicker, the velocity to maintain lift would be less and if it were also in ground effect, the overall velocity would go down a bit more due to a decrease in drag. Likewise if the density was thin, the ground effected velocity would be higher.

Since temperature varies density and viscosity, hot air would make density thin if the air pressure was constant, etc.

Let me know if your answer was in here.  

[Edited 2005-12-08 00:32:39]


The meaning of life is curiosity; we were put on this planet to explore opportunities.
User currently offlinePihero From France, joined Jan 2005, 4462 posts, RR: 76
Reply 2, posted (8 years 9 months 2 weeks 6 days 21 hours ago) and read 3018 times:
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It will be the same, as we are talking about equivalent airspeed.
Upon landing, the aircraft wing will be generating the same amount of lift, at grossly the same indicated airspeed. What changes will be the true airspeed of our model.
for more on this,
Ground effect

Regards



Contrail designer
User currently offlineKELPkid From United States of America, joined Nov 2005, 6392 posts, RR: 3
Reply 3, posted (8 years 9 months 2 weeks 6 days 18 hours ago) and read 2988 times:

Quoting Modesto2 (Thread starter):
How does ground effect change at a high altitude and hot temperature situation compared to standard conditions at sea level? At a high density altitude, will the ground effect be more or less pronounced and why?

You won't notice a difference, trust me...I learned to fly "Hot 'n High" (desert southwest of the USA, the LOWEST field I practiced at was 4100' MSL!).

Indicated airspeed is what performance charts are written for, and for good reason: It doen't change MUCH (I know, it does change some...and there are corrections that can be applied for calibrated or true airspeed) relative to the aircraft's performance (for typical airfield elevations, anyways...).

If you carry 5-10 extra knots on final on a 100 degree (Farenheit) day at, say, LRU, you will float just as far down the runway bleeding off the extra airspeed before the 172 finally decides to land  Smile Actually, maybe even a bit longer, since your groundspeed will be much higher in this instance, than say if the day were more like 60 degrees farenheit.

If you attempt a soft-field takeoff, you will take much longer to get airborne into ground effect (due to the less-dense air effecting both lift and engine performance), however your indicated airspeed will still be more or less the same when you are able to go airborne into ground effect. Once again, if you are hot and high, your actual groundspeed will be pretty high in relation to a much cooler day.



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineStoicescu From United States of America, joined Sep 2005, 79 posts, RR: 0
Reply 4, posted (8 years 9 months 2 weeks 5 days 21 hours ago) and read 2914 times:

There will be no difference. The loss of induced drag will be the same (also the downwash)

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