depends on the helicopter. i fly remote control ones in my free time. bigger helicopters, the 12 to 30 degrees maybe sounds about right. but for small ones, depending of design and purpose, can go 90 degrees and back again. but of course they would have to be very high off the ground because at 90 degrees, all lift is lost. some pilots have modified the rotor trim control on the helicopter to enable it to fly upside down. So practically anything is possible

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Current
2006 E320 CDI, 57K bought at 67K "Liesl"
1986 190E 2.3-16, 198K bought at 56K "Brigitta"
1987 300TD (Chuggin Along), 292K "Friedrich"
1995 E320 Wagon, 200K "Louisa"

Past
1987 300SDL, (sold) 125K, bought for 1$ "Kurt"