As I progress through my pre dual flight training study [by design], I have come across the concept of Density Altitude and its impact on aircraft performance. Right now, my focus is on the takeoff and landing segments of flight. I get the fact that density altitude is pressure altitude corrected for non-standard temperature, but that technical definition somehow leaves me still wanting more.
Apparently, density altitude can be impacted by temperature. An increase in temperature leads to an increase in density altitude which leads to a decrease in aircraft performance. Conversely, a decrease in temperature leads to a decrease in density altitude which leads to an increase in aircraft performance.
Additionally, I've read that density altitude can also be impacted by relative humidity with the same directional vectors as Temperature: raise this, lower that, lower this raise that. I also understand that when you combine the effects of both temperature and relative humidity, the impact on density altitude and by extension, aircraft performance, can be drastic.
But, here is what I don't understand: In high density altitude conditions, why does the delta between indicated airspeed and true airspeed begin to widen or increase?
Example: Normal departure airport field elevation is 3,000 ft msl. Atmospheric conditions are such that the HDA is 7,300 ft msl. So, the aircraft will now need more runway for the ground-roll. But,
why does the aircraft
also require a higher true airspeed/ground speed? I don't yet understand why.
I've read stories where pilots have flown into higher field elevation airports, spent some time on the ground, came back to the aircraft and loaded it up with full fuel, cargo and possibly a passenger or two,
after a significant increase in the density altitude and then has very difficult trouble getting the nose off the ground during the ground-roll, having to either abort the landing, or ditching off the end of the runway.
This blows my mind and I'm trying to make sure that I don't do the same thing. Are these cases simple matters of just needing more airspeed? Or, are these matters a case where the HDA factor had grown well beyond the takeoff performance capability of these aircraft and no matter what the pilot did, the takeoff was doomed to end in an abort, regardless?
Thanks for the help in advance, guys.
