Can we use a past form of verb with present form of linking verb 'be'?

Question

I am learning English grammar from a book. The current section I am learning is Adverbial clauses of time (future reference).The section says to use present form after adverbial clause when referring to future. e.g

The Owens will move to new flat when their baby is born.

We should visit the Duty Free Shop before our flight calls.

Now as we know called is the past form of call verb, So how can we say ...before our flight is called. like is it right to say e.g

The verdict was announced and Pierre is punished for a crime he is unaware of.

So my question is, can we use the past form like punished or called with is, as we see in the sentences: Pierre is punished or flights is called.

Answer 1

As Khan tells you, the -ed forms you ask about are not being used as past-tense forms but as past participles.

With "regular" verbs, the past-tense and past-participle forms are the same. But many of the oldest verbs in the language follow different patterns, in which the past-participle form is marked with a change in the stem vowel or an -en ending, or both.

 PLAIN FORM     PAST FORM     PAST PARTICIPLE
 sing           sang          sung
 break          broke         broken  
 give           gave          given   

It is the past-participle form which combines with a form of BE to form the passive-voice construction. The participle itself has no tense; the time referred to is determined by the tense of the BE form:

                PRESENT                       PAST
 ACTIVE VOICE:  Somebody punishes Pierre.     Somebody punished Pierre.
 PASSIVE VOICE: Pierre is punished.           Pierre was punished.

 ACTIVE VOICE:  Somebody sings a song.        Somebody sang a song.
 PASSIVE VOICE: A song is sung.               A song was sung.  

The past-participle form also combines with a form of HAVE to form the perfect construction; and the perfect and passive may be combined with the past-participle form of BE:

                PRESENT PERFECT               PAST PERFECT
 ACTIVE VOICE:  Somebody has punished Pierre. Somebody had punished Pierre.
 PASSIVE VOICE: Pierre has been punished.     Pierre had been punished.

 ACTIVE VOICE:  Somebody has sung a song.     Somebody had sung a song.
 PASSIVE VOICE: A song has been sung.         A song had been sung.  

All of these may also be cast into future tense with the modal auxiliary will or the BE going to construction. In this case the following auxiliary ('helping') verb, BE or HAVE, takes the infinitive form

                    FUTURE
 ACTIVE:            Somebody will sing a song.      Somebody is going to sing a song
 PASSIVE:           A song will be sung.            A song is going to be sung.
 PERFECT ACTIVE:    Somebody will have sung a song. Somebody is going to have sung a song. 
 PERFECT PASSIVE:   A song will have been sung.     A song is going to have been sung.

There's rarely a need for the future perfect; I've seen an estimate that the future perfect passive occurs about once every 1800 printed pages!

Answer 2

The phrase "...before our flight calls" suggest that the flight itself is calling, ie it suggest that the aircraft is sending the message. What actually happens is that someone sends the message (or puts text on a flight departures board) on behalf of the airline and the flight crew.

The sentence "The verdict was announced and Pierre is punished for a crime he is unaware of" works well. However I would prefer either "... was announced and Pierre was punished ..." or "... is announced and Pierre is punished ..." depending on whether the whole text is past or current tense.

Answer 3

"Is called" is a passive construction. "Before our flight is called" means " before somebody calls out flight BA772 to Paris is now boarding".

We make the passive in English by using the passive auxiliary BE and a participle. The tense of the verb BE tells us the tense of the construction. So "is called" has the present tense of the verb BE, and is therefore present tense.

The participle we use to make the passive often looks the same as the past tense of the verb. However, participles don't have any tense. The fact that these participles sometimes look the same as the past simple form is misleading. They have nothing to do with past time or with tense at all. Unfortunately though somebody decided to call them "past participles". Luckily, that was a long time ago and that person is now extremely old or deceased, so we do not need to shoot them.

So-called "past participles" have nothing to do with the past!