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I've seen the following sentence just before. I hope you also a little look at it.

"Only such technical staff as are skilled and experienced in their respective trades and such foreman and leading hands as are competent to give proper supervision to the work they are required to supervise."

[1] I think the sentence above is wrong so revised as follows.
"Only such technical staffs as are as skilled and experienced in their respective trades and such foremen and leading hands as are competent to give proper supervision to the work they are required to supervise."

[2]And when reading the sentence, it seems a comparative sentence as "you are as white as snow".

[3]So now I think it should be like this.
"Only such technical staffs are as skilled and experienced in their respective trades and such foremen and leading hands as being competent to give proper supervision to the work they are required to supervise."
Am I wrong ?

[4] As far as I know, the first "as" is an adverb. We should put it behind of "to be" verb. Why did the writer put the first "as" in front of "to be" verb?

[5] For the second "as", it can be a preposition or a conjunction. If it is a conjunction, does he have to write as "as being",not "as are"?

Could someone answer me whether or not the sentence above is right and teach me why he wrote like that.

Thank you for your kind explanation in advance.
Comments  
The sentence seems to me to be a fragment, not a complete sentence.

1) Staff is a mass (non-count) noun. The plural "staffs" is possible when the word means a walking stick, but not employees.

2) "As" is used in an unusual way. It is a relative pronoun, meaning "that" see entry #`13.
http://dictionary.reference.com/browse/as?r=66

So this is an alternate writing:

"Only such technical staff that are skilled and experienced in their respective trades and such foreman and leading hands that are competent to give proper supervision to the work they are required to supervise ... (to complete this we need a complement such as) will be hired in the future.
Really thank you so much for your kind explanation,Ms.AlpheccaStarsEmotion: embarrassed. Today I've learned that "as" can be a relative pronoun for the first time. By the way, then, the noun of "foreman" is also a kind of plural noun like staff.Isn't it? Thank you for your answer in advance.
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Since my dictionary doesn't indicate the role of an adverb for "such",I'm confused on the expression of "such foreman". Please forget my question as to "such foreman". I will treat it as a singular noun. Thank you,Ms.AlpheccaStarsEmotion: embarrassed
AlpheccaStarsStaff is a mass (non-count) noun. The plural "staffs" is possible when the word means a walking stick, but not employees.
When 'staff' refers to the employees of one company, it is generally used as a singular collective noun, though in BrE it can take a plural verb: The staff are not happy about the new timetable.

When we are talking about the staffs of different establishments, the plural form is common. Sixteen of the first twenty citations (and there are 1,453) for 'staffs' in the COCA are of the word used in this way
Thank you so much,Mr.Fivejedjon. You've made me know for the noun of "staff" more clear. Thanks once again,Emotion: embarrassed
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Son JamesBy the way, then, the noun of "foreman" is also a kind of plural noun like staff.Isn't it?
The plural of compound words of -men and -woman follows the pluralization of men and women.

The chairman / chairwoman (singular)
The chairmen / chairwomen (plural)
The foreman (singular)
The foremen (plural)

In American English, staff as a collective noun takes a plural verb. British English perhaps allows the plural form.

The staff of United Airlines, Korea Airlines, and British Airways are forming a union. (I would use this form being a speaker of American English)
The staffs of United Airlines, Korea Airlines, and British Airways are forming a union. (It is possible, but sounds a bit "off" to me. Perhaps it is more common in British English)

One major difference in the two Englishes is the collective plural and their verb agreements.

When speaking of the employees of one company, a singular verb is uncommon but possible:
The staff is not happy about their benefits.

But I think most times the verb is plural:
The waitstaff here are not well trained in customer service.
Thank you so much for your kind explanation,Ms.AlpheccaStarsEmotion: embarrassed