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A hot tarmac runway / where is airport OAT measured?

Alexis wrote:

I knew that formula … but for 34° C and 1500 ft MSL at a QNH of 1018 my calculator says: DA 3799 ft!

Alexis you are right, I just edited and corrected my post – had forgotten to add the base airport elevation. Too early morning here in SoCal

Mooney_Driver wrote:

What I like is when airports include it in the ATIS like Samedan does.

Recently most (all?) airports at in the SoCal area have started to include this. Not overly relevant for the coastal ones, but given that there are places like Big Bear with an elevation of 7000ft, it becomes a great tool.

@172driver
Thanks! (Where in SoCal, will be there this summer)

Alexis wrote:

Thanks! (Where in SoCal, will be there this summer)

Then get in touch! Los Angeles.

For years many AWOS/ASOS transmissions in the US have included density altitude (although for a long time some just said “Check density altitude”).

Andreas IOM

alioth wrote:

For years many AWOS/ASOS transmissions in the US have included density altitude (although for a long time some just said “Check density altitude”).

Around here it seems to be a relatively new thing, at least for the low-lying airports. Big Bear had it for years (at least as long as I’ve been flying there!) and they also have a big sign at the runup, but places like KSMO never had it.

As I wrote in post #1 there can be a lot of hot air rising up from a hot runway.

I wonder if performance on a hot dark runway might be helped by the hot air rising up from it, so while you lose in terms of density altitude (the air above the runway is less dense so you get less lift for a given IAS and AoA) you might gain some lift because the air is rising.

It has to be something like this otherwise I think there would be a lot more trouble in practice. I can easily see the air above a runway to be 10 degC hotter which is a really big increment on the runway distance required.

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Shoreham EGKA, United Kingdom
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