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How is the ATR 42/72 empennage considered? Is it a T-Tail or a cruciform tail? From the image the elevators are placed quite high on the tail that they can be considered as a T-Tail but is it so?

Looking at the tail of a 727 the elevators are placed at the top of the tail but just leaving the space for the mechanism to move them, whereas on the ATR they are placed in a slightly lower position.

Are there any technical specifications and measurements that clearly define the difference between the two mentioned configurations?

I understand that cruciform means "similar to a cross" but it would be interesting to know, as previously mentioned, if there are specifics about this definition making it clear for everyone from a technical point of view. (briefly, when does a T-Tail become cruciform?)

ATR Tail view

727 Tail view

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    $\begingroup$ Why do you think there should be clear boundary? Those are just common names for the designs. And there is no principal difference between them. All parameters vary continuously with the position of the horizontal stabilizer. $\endgroup$
    – Jan Hudec
    Apr 21, 2014 at 15:21
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    $\begingroup$ If we were in any other industry I would have closed an eye on it but since we are talking about aviation where everything is standardized and everything is documented I thought that such differentiation would be in some way distinguished. That's all $\endgroup$
    – Fabrizio Mazzoni
    Apr 21, 2014 at 15:35

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As far as technical specifications are concerned, some explanation is:

Excerpt from Wikipedia (formatting is mine):

T-tail

DESIGN: The horizontal stabilizer is mounted on top of the fin, creating a "T" shape when viewed from the front.

PURPOSE:

  • T-tails keep the stabilizers out of the engine wake, and give better pitch control.
  • T-tails have a good glide ratio, and are more efficient on low speed aircraft.
  • However, T-tails are more likely to enter a deep stall, and are more difficult to recover from a spin.

T-tails must be stronger, and therefore heavier than conventional tails. T-tails also have a larger radar cross section.

Cruciform tail

DESIGN: The horizontal stabilizers are placed midway up the vertical stabilizer, giving the appearance of a cross when viewed from the front.

PURPOSE: Cruciform tails are often used to keep the horizontal stabilizers out of the engine wake, while avoiding many of the disadvantages of a T-tail.

In reference to your comparison between ATR 42/72 with Boeing 727, if we take out the difference in tail heights (ATR 42: 24' 11"; ATR 72: 25' 1"; B727: 34' 0"), the position of horizontal stabilizer on vertical stabilizer is almost the same on these three airplanes. So they all match closely to a T-Tail configuration rather than a cruciform.

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