TL;DR Use conv standard function.
conv(num: Column, fromBase: Int, toBase: Int): Column Convert a number in a string column from one base to another.
With conv a solution could be as follows:
scala> icao.show
+------+-----+
| Icao|count|
+------+-----+
|471F8D|81350|
|471F58|79634|
|471F56|79112|
|471F86|78177|
|471F8B|75300|
|47340D|75293|
|471F83|74864|
|471F57|73815|
|471F4A|72290|
|471F5F|72133|
|40612C|69676|
+------+-----+
// conv is not available by default unless you're in spark-shell
import org.apache.spark.sql.functions.conv
val s1 = icao.withColumn("conv", conv($"Icao", 16, 10))
scala> s1.show
+------+-----+-------+
| Icao|count| conv|
+------+-----+-------+
|471F8D|81350|4661133|
|471F58|79634|4661080|
|471F56|79112|4661078|
|471F86|78177|4661126|
|471F8B|75300|4661131|
|47340D|75293|4666381|
|471F83|74864|4661123|
|471F57|73815|4661079|
|471F4A|72290|4661066|
|471F5F|72133|4661087|
|40612C|69676|4219180|
+------+-----+-------+
conv has a feature of giving you a result of the type of the input column, so I started with strings and got strings.
scala> s1.printSchema
root
|-- Icao: string (nullable = true)
|-- count: string (nullable = true)
|-- conv: string (nullable = true)
If I had used ints I'd have got ints.
You could cast the result of conv using another built-in method cast (or start with a proper type of the input column).
val s2 = icao.withColumn("conv", conv($"Icao", 16, 10) cast "long")
scala> s2.printSchema
root
|-- Icao: string (nullable = true)
|-- count: string (nullable = true)
|-- conv: long (nullable = true)
scala> s2.show
+------+-----+-------+
| Icao|count| conv|
+------+-----+-------+
|471F8D|81350|4661133|
|471F58|79634|4661080|
|471F56|79112|4661078|
|471F86|78177|4661126|
|471F8B|75300|4661131|
|47340D|75293|4666381|
|471F83|74864|4661123|
|471F57|73815|4661079|
|471F4A|72290|4661066|
|471F5F|72133|4661087|
|40612C|69676|4219180|
+------+-----+-------+
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