Above rwy elevation, but not over the runway, sorry ;-)
I wonder if this low departure was due to temperature, or intentional as a joke?
Accurate OAT measurement normally uses the Stevenson screen. Interesting that the inventor had a son called R.L. Stevenson 
Apparently, the best result is obtained if the ground is covered in short-cut grass.
That Falcon 50 is nothing compared to the famous Vodka Burner.
Alexis is correct with 2m. The temp sensors are not in the shade however but they are in a specialized housing which is also ventilated. They used to be in white wooden boxes (the traditional Stevenson weather huts) but now this is done with specific equipment. VAISALA is the foremost producer of such sensors. They are sufficiently distanced from the runway not to present an obstacle to aviation. Most antennas such as GS etc are significantly higher.
We also have over ground sensors at 5cm over grass and Beton. Temps can be significantly different but for flying you hardly go below 2m I imagine…
As every WMO station does it that way the results are comparable everywhere.
This is what one of those looks like.
Btw, there’s a very easy – and pretty correct – rule of thumb for DA: DA increases by 1000ft for every 8C above standard temp.
So, say, you have a sea-level airport (standard temp 15C) and it’s 31C then your DA is approx. 2000ft. Works very well and as additional bonus, errs a bit on the side of caution, IOW tends to give you a slightly higher reading than the actual DA. It doesn’t take humidity into consideration.
In Alexis’ example above this would give you:
Munich airport elevation : 1500ft
Standard temp therefore: 15C minus 3C (2C standard lapse rate per 1000ft) = 12C
DA: ((34-12)/8)x1000 = 2750 rounded above airport elevation 1500ft, therefore 1500+2750 = DA 4250ft
NOTE: edited, had forgotten to add the base airport elevation (note to self – don’t post too early in the morning!)
Peter wrote:
Accurate OAT measurement normally uses the Stevenson screen. Interesting that the inventor had a son called R.L. Stevenson
Wow! Never knew that. Thanks Peter!
I knew that formula … but for 34° C and 1500 ft MSL at a QNH of 1018 my calculator says: DA 3799 ft!
Nowadays everyone has a smart phone anyhow and there are dozens of free apps to calculate DA.
What I like is when airports include it in the ATIS like Samedan does.
It’s also fun to calculate density altitude of alpine passes or rather their minimum crossing altitudes. At ISA +20 some of the smaller engined planes can run in trouble even crossing a 9000 ft (min overflight) pass route.
Yes, what’s also great is the DA indication on my MFD (I wonder why it doesn’t have a way to enter weight and show takeoff distance right away). And of course it would be nice if actual airplane weight was measured (by sensors in the landing gear) .. and the runway is too short pull the mixer automatically ;-))
I have DA on my Davtron.
