SkyDemon Forums

Density altitude

http://forums.skydemon.aero/Topic26746.aspx

By Martin Bech - 8/24/2018 9:59:30 PM

If you can calculate TOD in different temp and at different altitudes - so can a computer program!!

It is just a matter of giving the program neccesary information to do that. I know there are a person on this forum who do not want more help from SD, but want you to do things manually.......old stuff.

Other systems calculate TOD, so can SD. I would like to have that giving a simple possibility to make the calc before every flight.
By T67M - 8/25/2018 4:34:08 PM

According to most POH, the first step in calculating the takeoff/landing distance is to factor pressure altitude and temperature togheer, effectively "calculating" the density altitude. However, no two POHs then use this in the same way. Since SD (rightly or wrongly) doesn't do the performance calculations for you, there is no point (IMO) in SD calculating a useless number that can't be used in the POH charts/tables for aircraft performance. What you need for them is (generally) pressure altitude, and that's trivial to obtain with no calculation whatsoever (set 1013.25 in the Kohlsmann Windows and read the altimeter).
By BearLS - 8/28/2018 12:47:50 PM

 
Tim Dawson - 8/22/2018 4:20:17 PM
Chris, you forgot to say exactly why it would be useful. What exactly do you use the DA number for, once you have it?


Density altitude is the critical parameter to calculate the take off distance and the climb rate.
The most dramatic example i know is Samedan LSZA at 5600 ft altitude. Before you are allowed to fly there you must pass an examination in internet. The calculation of the density altitude is an important part of it. The reason for that is that there where to many deadly accidents at take off.
Most people forget that the density altitude is also important at higher altitudes in terms of the climb rate. In the last weeks we had rather high temperatures in Switzerland. At least in two cases Swiss Transportation Safety Investigation Board (STSB) had to get active due to deadly accidents which are absolutely linked to the density altitude, see  https://www.sust.admin.ch/inhalte/AV-berichte/HB-HOT.pdf (20 persons killed) and https://www.sust.admin.ch/inhalte/AV-berichte/HB-KEE_2.pdf (4 persons killed, I knew the pilot and the plane very well).
To increase the awareness for the density altitude it would be very helpful to get the density altitude in each METAR reported by SkyDemon.

Yes, I am aware the we mountain pilots will probably never get the desired improvement, since we are a minority among the customers of SkyDemon. Very sad situation.
By rafale52 - 9/4/2018 8:08:37 AM

 
BearLS - 8/28/2018 12:47:50 PM
 
Tim Dawson - 8/22/2018 4:20:17 PM
Chris, you forgot to say exactly why it would be useful. What exactly do you use the DA number for, once you have it?


Density altitude is the critical parameter to calculate the take off distance and the climb rate.
The most dramatic example i know is Samedan LSZA at 5600 ft altitude. Before you are allowed to fly there you must pass an examination in internet. The calculation of the density altitude is an important part of it. The reason for that is that there where to many deadly accidents at take off.
Most people forget that the density altitude is also important at higher altitudes in terms of the climb rate. In the last weeks we had rather high temperatures in Switzerland. At least in two cases Swiss Transportation Safety Investigation Board (STSB) had to get active due to deadly accidents which are absolutely linked to the density altitude, see  https://www.sust.admin.ch/inhalte/AV-berichte/HB-HOT.pdf (20 persons killed) and https://www.sust.admin.ch/inhalte/AV-berichte/HB-KEE_2.pdf (4 persons killed, I knew the pilot and the plane very well).
To increase the awareness for the density altitude it would be very helpful to get the density altitude in each METAR reported by SkyDemon.

Yes, I am aware the we mountain pilots will probably never get the desired improvement, since we are a minority among the customers of SkyDemon. Very sad situation.


I totally agree 
By Chris_LSZO - 8/22/2018 11:19:07 AM

Hi

Easy-VFR calculate the density altitude for every airfield. Could you implement this very useful feature in Skydemon too?
Thank you.



Chris
By ArnaudC - 10/3/2018 3:05:16 PM

For quick MET readouts I use the AeroWeather app. It calculates DA.
Most POHs have a PA/DA conversion chart at the beginning of section 5. Cruise performance charts can be used for it as well.
As mentioned by T67M above, unless T/O/climb/LDG performance calculations are made in SD as well, you still have to open your POH. Displaying only the DA without the rest is only semi-useful.


 
T67M - 8/25/2018 4:34:08 PM
What you need for them is (generally) pressure altitude, and that's trivial to obtain with no calculation whatsoever (set 1013.25 in the Kohlsmann Windows and read the altimeter).

It's easier to set the field elevation and read the PA in the window. Potato potato.