modesto2
Posts: 2685
Joined: Sun Jul 16, 2000 3:44 am

Ground Effect In High Density Altitude

Thu Dec 08, 2005 7:28 am

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?
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: Ground Effect In High Density Altitude

Thu Dec 08, 2005 8:05 am

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.
 
Pihero
Posts: 4248
Joined: Mon Jan 31, 2005 5:11 am

RE: Ground Effect In High Density Altitude

Thu Dec 08, 2005 8:06 am

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
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Ground Effect In High Density Altitude

Thu Dec 08, 2005 10:29 am

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 :-)
 
Stoicescu
Posts: 80
Joined: Sun Sep 11, 2005 2:39 pm

RE: Ground Effect In High Density Altitude

Fri Dec 09, 2005 7:29 am

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

Who is online

Users browsing this forum: BartSimpson, StereoTechque and 12 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos