Brakes are always an interesting subject, especially when they don't work.
I came across this thread where some tow truck operators were discussing parking brake failure on a P 30 Airstream motorhome. I thought it might be of interest for those who own older units.
Airstream park brake. in Motor Coach & Emergency Vehicle Towing Forum
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"Had a customer call in this morning over 100kms from us stuck in a break down area. He has a 1996 Airstream motor home on a Chevy chassis with a GVWR of 16500lbs. Presumably it's a P30 but he didn't know. "
Remember -- Anytime you are traveling, it helps everyone including yourself, if you know what equipment you have, or have the information with you so that you can refer to it when needed.