Passive voice (all tenses)
Are these translations correct? and I couldn't translate some tenses into spanish. For example: The letter has been being written.
I put three question marks. Can you fill them? Gracias por sus ayudas!
P.S. This is not my homework. 
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The letter is written (by the secretary).->La carta está escrita. (por la secretaria)
The letter is being written.->La carta está siendo escrita.
The letter was written.->La carta fue escrita.
The letter was being written.->La carta estaba siendo escrita.
The letter will be written.->La carta será escrita.
The letter will be being written.-> ???
The letter will have been written.->La carta habré sido escrita.
The letter will have been being written.->???
The letter has been written.->La carta ha sido escrita.
The letter has been being written.-> ???
The letter had been written.-> La carta había sido escrita.
The letter had been being written.-> ???
5 Answers
Traditonal passive voice (versus using passive-reflexive se) uses Ser+pp+por+agente.
La carta es escrita (por la secretaria).
The letter is written (by the secretary).->La carta está escrita. (por la secretaria)
Using estar is saying that the letter is written (adjective; not verb). e.g. The letter is written in English.
The letter was being written.->La carta estaba siendo escrita. This is past progressive tense with the traditional passive voice construction.
The letter will be being written.-> ???
La carta estará siendo escrita. (future progressive and traditonal passive construction)
The letter will have been being written.->???
La carta habrá estado siendo escrita.
The letter has been being written.-> ???
La carta ha estado siendo escrita.
The letter had been being written.-> ???
La carta había estado siendo escrita.
You might wish to read about how to form the perfect progressive tenses in this article.
Mistake in "The letter will have ben written" - La carta habrá sido escrita.
The four that you want translated don't make sense in English or in Spanish.
Let us work on your example: The letter has been being written.
The sentence is incorrect in english. Choose one or the other.
The letter is being written. (He, She or It) is writing the letter would be. Present progressive, Está escribiendo la carta.
The letter has/had been written. (He, She or It) has/had written the letter. Present/Past participle, Ha escrito la carta. or Había escrito la carta.
As Margaret said... you can translate them into Spanish, but neither the English nor the Spanish make any sense with the "been being".
áThe letter will be written.->La carta será escrita.
The letter will be being written.-> La carta será escrita.
The letter will have been written.->La carta habrá sido escrita.
The letter will have been being written.->La cartas habrá estado siendo escrita
The letter has been written.->La carta ha sido escrita.
The letter has been being written.-> La carta ha estado siendo escrita.
The letter had been written.-> La carta había sido escrita.
The letter had been being written.-> La carta había estado siendo escrita.
