Giving a repair command to a helicopter in TD has it return to the helipad and repair.
However, if you give the command to two aircraft the 2nd aircraft will ignore the command. In fact if you have two helipads it will not even go to the farther one away. It seems the command searches for nearest helipad, and if it's occupied the order is ignored.
the helipads are technically repairpads but they only allow aircraft. This also happens if you order aircraft to repairpads in other mods with the difference being only that other aircrafts land at regular helipads instead.
In Red Alert this is an issue, as helipads do not repair aircrafts.
A partial workaround is to send a group of helicopters to the repair bay. A single helicopter will land for repairs. When it is fully repaired, it takes off. Clicking the repair bay again will send another helicopter for repairs. This babysitting is tedious, and requires attention that could be better utilized elsewhere.