ATR empennage configuration

Fabrizio Mazzoni
  • ATR empennage configuration Fabrizio Mazzoni

    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

  • 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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