Thanks, Monarch.
With respect to the Birgenair accident, at that time the Boeing checklist did not specify an immediate attitude and thrust in the memory items of the checklist as it does now. Boeing only reinvented that checklist in response to the Air France accident (as you would know). So the current Boeing checklist may have helped them back then.
Draglift, I apologise for the tone of my response, and thank you for letting it go. When scenarios come up in Tech Log, it is easy for various posters to interpret the scenario in different ways if the exact conditions of the questioned scenario is not very specific. I had worst-case scenarios in mind when I responded to your post.
Non-normal scenarios will always have a milion answers, and that's obviously why Boeing cannot provide a QRH answer for every scenario. In the same way, PPruNe cannot provide an answer for every scenario.
I have given my answer that will cover most scenarios. Other posters might have had different scenarios in mind when posting their answers. I finally provided my reasons for my answer (which I probably should have done earlier) but those reasons may also not cover all scenarios.
I will concede after reading all these posts that there may be situations where setting roughly known cruise thrust and attitude may be appropriate in some circumstances, so long as the shared mental model I explained previously is not compromised. That will depend on many factors, including how well you know the pilot sitting next to you, the conditions on the day, whether you have some idea of why the airspeed has become unreliable, and whether you are absolutely positive there is or will be no confusion prevalent on the flight deck.
Human factors cause a lot of aircraft accidents. They also save a lot of aircraft - you won't find me proposing autonomous airliners on
those theads.
There aren't a lot of accidents put down to unreliable airspeed, so the data supporting appropriate corrective action is minimal.
My home port of Brisbane Australia had a wasp infestation a year ago resulting in at least 4 aircraft in one day suffering blocked pitots on takeoff. Fortunately, none of those incidents turned into accidents, they were all well handled, and I don't think they even made the local news. These wasps were so keen they could block a pitot in a 40 minute transit. (Only in Australia... I saw one of them devouring a bird-eating spider in the engine intake during my walkaround...
). We now install pitot covers every transit.
But as I said, the checklist changed considerably after the Air France accident. With a lack of data, any proposed corrective action outside of the "extensively studied" QRH actions are subjective or speculative.
I've certainly learned something from this thread...by thinking at length about what others have posted and re-evaluating my thoughts on the subject. If anyone else has learned anything from my posts then that makes me happy too.