always let any pilot back on to the flight deck? In all circumstances let the captain back in? Only let F/O in if captain agrees? Let any pilot back who gives a cheery wave....etc
Wiggy
The flight crew have an absolute right to be where they belong on the flight deck.
Any flight crew Captain or FO has a right to re enter and have access to the flight deck.
The remaining Flight Crew member still on the the flight deck has no rights to block that entrance to him/her unless they have absolute backed up evidence that their actions are correct.
I would suggest that a Captain /FO on the outside who has lost the plot would be noticed by the CC who I am sure would be relaying messages to the remaining pilot flying that pilot X has lost the plot and just assaulted a CC or whatever?
On the ground the remaining handling pilot would I am sure be able to justify his actions with multiple CC and PAX witness.
There are a number of reasons why the other pilot may not be able to continue with his / her duties,illness, incapacitation jumps to mind but that becomes a team event with CC and even a PAX Doctors involvement! I cannot think of any innocent situation where one pilot would unilaterally have cause to lock out another flight crew member without third party involvement and witness
But you cannot get away from that absolute right principle! Any other argument goes into the realms of absurd