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Why do some aircraft have T-tails?

Why do some aircraft have T-tails?

A google suggests that there are very few advantages to such a design.

The only 2 that I found that were really relevant were:

1. On some aircraft the wing disturbs the airflow over the elevator, but by locating it up higher it keeps it in cleaner air
2. It’s out of the way on the ground, and therefore less likely to get damaged.

However these don’t seem to stack up to me. With 1, that doesn’t seem to be a problem in the cruise as there is plenty of fast airflow. However at slower speeds, on approach and especially in the flair, where there is much less airflow, because of the nose higher attitude (relative to the airflow) the tail of a T-tail is now put directly into the dirty airflow. So exactly when you need the elevator to be most effective, it’s put into the dirty airflow on a t-tail.

With 2, while it might be less likely to get damaged higher up (I remain to be convinced of that anyway) it’s also a lot harder to inspect for damage preflight.

But there are plenty of T-tail aircraft around. So what am I missing? Why do some models have t-tails instead of conventional tails? What is their advantage? Is it purely an aesthetic choice by the designer?

EIKH Kilrush

dublinpilot wrote:

Is it purely an aesthetic choice by the designer?

Could be. Just like for wing tips on small aircraft – quite often they are introduced for “ramp appeal”.

EGTR

Comfort in cruise is important, and you would be willing to forgo a degree of comfort in the approach or take-off for improved comfort in cruise. However, one of the drawbacks of the T-tail is the possibility of getting into a deep stall with the tail shielded by the wing. That is to say, that this is something that happens at angles of attack well beyond those you might hope to meet in the approach. So frankly I doubt whether increased roughness in the approach would be of concern.

Keeping the tail in clean air will make it more efficient. On our aircraft, excepting those who fly jets, the roughness also comes from propwash as well as disturbed air from the wing.

It’s not something you would do for ramp appeal as a T-tail is structurally more challenging than a conventional tail. I am aware of aerobatic aircraft with T-tails such as the Colomban CriCri, but I believe they all warn against flick rolls, for example, as the concern is that the tail simply wouldn’t hold up to the abuse.

The Piper Tomahawk is the only aircraft I’ve flown with a T-tail. You need to be moving a bit faster before you get pitch authority, as the horizontal stabiliser is not in the propwash. It’s nice to fly and the handling is fairly conventional otherwise.

Last Edited by kwlf at 28 Dec 14:14

Less sensitive to debris and stones, better rudder authority in flight and during landing, less susceptible to turbulent airflow in turboprops, therefore oftentimes found in military airplanes and sailplanes ?

Safe landings !
EDLN, Germany

EuroFlyer wrote:

Less sensitive to debris and stones, better rudder authority in flight and during landing,

Why would a T-Tail have better rudder authority? The rudder is much the same wheter the elevator sits atop of the horizontal stabiliser (=T-Tail) or at its bottom, isn’t it? Or do you mean elevator instead of rudder?

I always wondered wheter a cruciform tail would be the “best of both worlds”, as in one of my favourite aircraft designs, the Do 335 Pfeil

On such aircraft, the tailplane is not directly in the wake of the wings, but not too far from the thrustline either.

Novice pilot
EDVM Hildesheim, Germany

Comfort in cruise is important,

My PA28RT – Arrow IV – is a T-tail.
It is phenomenally stable and smooth in the cruise which is 98% of my flying.

Rochester, UK, United Kingdom

Peter_G wrote:

My PA28RT – Arrow IV – is a T-tail.
It is phenomenally stable and smooth in the cruise which is 98% of my flying.

Can confirm that. I only have a few hours in that type, but the difference to a ‘normal’ PA28 is startling.

I’ve never noticed any extra smoothness in a Pa38 over a Pa28.
The prototype BAC111 had a fatal deep stall from high altitude.
With prop singles, the propwash is an advantage for low speed emergencies.
When the rear engine jets with high tails came in, I suspect the hightail singles were a fashion choice.

Maoraigh
EGPE, United Kingdom

It is also an advantage on the ground, when rain falls you can get a little bit of shelter :-). Besides that, on instrument approaches you benefit from pitch stability during power variation.

One rarely needs that much power amount or power changes on instrument approaches so that a T-tail make a big difference?

The amount of force required to flare is rather exagerated (the Arrow T-tail nose is as heavy as Mooney nose with same heavy engine) but I think comfort on cruise & ramp appeal would be the top selling points? it is very common in gliders, it seems to improve L/D ratio? but I never flew other than T-tail (I owned Grob102 & Grob109 and both were T-tail)

Last Edited by Ibra at 28 Dec 23:48
ESSEX, United Kingdom
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