If the crew took off in MANUAL, they will have noticed immediately
- I'm afraid I disagree. Remember 'going up' has far less effect on the ears than coming down'. I suggest 'may'? I had to depart INN once unpressurised until around 6000' due to a tech issue and I do not recall noticing anything 'unusual' on the ears. No comments from c/crew or pax either.
I cannot remember the detail of the Helios but I'm sure the 'implication' is that the crew did NOT notice the lack of pressurisation even when the horn went off.