Just looking at some aircraft on ADS-B,over the N Sea and looking at `details`,at FL s340-390,with IAS between 245-300 kts,,details show TAT/OAT,with a split usually between 25-30 degrees less on the TAT..Did the WW2 Navs have a `correction chart `,for the difference between TAT/OAT,lower IASs,as well as the `density/ISA correction...if you get my `drift`...?
I have seen OAT probes reading 0* when iced-up,when the actual OAT was totally different...