T-Tail design advantages?

[FSIGRAD]

I'm trying to figure out the advantages/disadvantages to T-tail aircraft design. I have an article that states T-tails became popular in the 1980's due to a 1970's NASA study that pointed out the configuration was ideal for spin recovery (Horizontal stablizer doesn't blank out the rudder in a spin) however this adds disadvantages of extra weight and complexity. It also said that T-tails have a modernistic appearance and enthusiasm for them is greater from the sales department than the engineering department.
I'm pretty sure there has to be more to the pro's and con's argument, T-tail airplanes that come to mind Seminole, BAE-146, C-141 Starlifter all seem to be short field planes and not ones that would be particularly conducive to spin recovery.

Any one have any ideas?

 

[Cornelius]

You get less pitch changes with changes of power since the t-tail is in totally uninterrupted airflow. You get no debris damage from the prop blast. You won't get as big of pitch changes when extending/retracting flaps. I think the biggest reason the T-tail is more popular is because it in the free airstream.

These are some of my ideas.

 

[Marko Ramius]

Here's what I remember about what they told us in ground school on the 1900.

Advantages:
-increases cg range to allow for a wider range of payload carrying options.

-out of propeller slips stream, so less metal fatigue.

Disadvantages:
-like you said it requires a heavier, more complex structure, that adds weight. Although I'm guessing that has been controlled somewhat in modern times with the increased use of composites.

-another disadvantage that they didn't tell us all about for a long time(at least where I worked) is tail stall susceptibility. After the ATR Roselawn, and Comair Detroit accidents, I guess NASA did a study on icing characteristics in turboprop aircraft. In the video we saw in recurrent, I think they used a DHC-6, although I'm not sure. Anyways, NASA concluded that the turboprops most susceptible to tail stalls are those with unpowered flight controls(no hydraulic assist), large flap deflections, and of course T-tails. They attached all of these little strips to the tailplane to show you what happens. The airflow on the tailplane reverses, similar I think to what happened with the ailerons on the ATR. They had some nasty stalls on that video, and lost quite a bit of altitude on a few. The fun part is that the recovery is counter intuitive to everything we are generally taught about stalls: basically you have to increase pitch and reduce power.

While I have never heard of a tail stall incident in the mighty Beech, I never wanted to be the first so this video certainly got my attention. Especially since the carrier I worked for doesn't extend the flaps from 17 to 35 until the field is in sight on a IAP, which could be as low as 100 feet above TDZE-not a lot of altitude or time for a recovery! A little over three years ago, going into DEN on the ILS to 35L, our aircraft and a UAL 757 on the parallel picked up severe ice on the approach(airport closed after our arrivals). The rumours about the 1900 being a truck in ice are true, but it certainly doesn't fly the same! I sure would have liked to have known about all that tail stall stuff before I shot a minimums approach in stuff like that, not only for risk assessment but because that recovery procedure is so counterintuitive that you want to mentally remind yourself of it.

 

[flydog]

none

 

[A Squared]

http://www.ntsb.gov/NTSB/brief.asp?ev_id=20001213X32506&key=1

Kind of a brief description, but tailplane icing might have been a factor in this one. Tailplane icing is supposed to cause a pitch down, but with the cg as far aft as it was.....well, who knows.

 

[00Dog]

Also, some business jets' wings are so low that wing mounted engines would be dangerously close to the ground. One these planes, the t-tail is there out of necessity.

 

[Simon Says]

Disadvantage..............

I know from flying a PA28-201T (Arrow T-Tail) in the flare the nose became very heavy. This was due to the high angle of attack the main wing blocked air flow to the tail. This resulted more back force.

At least that is how it was explained to me.

 

[bobbysamd]

T-Tail disadvantage

I think another disadvantage may be lesser elevator authority because it is out of the propeller slipstream. I know a lot of t-tail aircraft are harder to land because the elevator loses authority in the flare.

It is true that the sales department loves t-tail aircraft. I remember that in the 80s a lot of airplanes that had the standard configuration were converted to t-tails, e.g. some Arrows.

 

[NSUDemon]

disadvantage

I've only flown a T-Tail arrow, and it was a beast at the controls, they were really heavy. I was also told by my chief flight instructor that the T-Tail design was simply a sales pitch in the 70's and 80's.

 

[MartinFierro]

That video which Marko Remius references is I believe the same one that is available from Sporty's Pilot Shop for only $5.00. I bought this, and it is excellent. WELL worth the money (it was 5.00 a few years ago, but I doubt the price has changed much). It is produced by NASA Glenn Research Center and is simply called "Tailplane Icing". There is another video also produced by NASA (and also for only $5.00) called "Icing for Regional and Corporate Pilots." Also well worth the small investment.