FlightSimFreak From United States, joined Oct 2000, 720 posts, RR: 0 Reply 1, posted (4 years 10 months 2 weeks 2 hours ago) and read 3739 times:
Cons:
In all T-tailed aircraft there is the possibility of "deep stall" where the elevator/stabilizer becomes stalled and the nose becomes impossible to push over, thus causing the plane to remain in a stalled condition, certain aircraft overcome this by fins or strakes on the fuselage (think of the MD-80)
In a normally-tailed single engine prop aircraft, when the pilot adds power, he immediately gets wind over the tail, and thus control authority. This does not happen in a T-tailed single such as the Beech Skipper (in which I have about 80 hours) or the Piper Tomahawk, thus the pilot cannot get immediate elevator authority by adding power.
From a maintenance point of view, it would probably be harder to get all the way up there to work on the T-tail, but this may not be the case, I don't know.
Pros:
The elevator and stabilizer are out of the way of FOD kicked up by the gear and engines.
In the case of the Beech Skipper and Piper Tomahawk, it gives the airplane a "big plane" control feel in that the plane handles similar to a large aircraft with respect to the fact that the pilot does not get immediate control authority with added power. Both the Skipper and Tomahawk were meant to be introductions into Beech and Piper's aircraft lines, respectively. Therefore, they were supposed to be trainers to prepare the pilot for a move up, eventually into a light twin, where the pilot doesn't get that control authority.
In jets with rear mounted engines, it probably gives the designer a place to hang the engines...
That's all that comes to mind at the moment. If I think of anything else in the near future, I will post again.
N243NW From United States, joined Jul 2003, 965 posts, RR: 16 Reply 2, posted (4 years 10 months 1 week 6 days 20 hours ago) and read 3676 times:
From a maintenance point of view, it would probably be harder to get all the way up there to work on the T-tail, but this may not be the case, I don't know.
Correct. Inadequate maintenance (probably because of the hassles of T-tail maintenance procedures) to the horizontal stab trim jackscrew was a major factor that led to the Alaska MD-83's accident off the coast of California.
Quoted several times by the NTSB: the probable cause of this accident was a loss of airplane pitch control resulting from the in-flight failure of the horizontal stabilizer trim system jackscrew assembly’s acme nut threads. The thread failure was caused by excessive wear resulting from Alaska Airlines’ insufficient lubrication of the jackscrew assembly.
Contributing to the accident were Alaska Airlines’ extended lubrication interval and the Federal Aviation Administration’s (FAA) approval of that extension, which increased the likelihood that a missed or inadequate lubrication would result in excessive wear of the acme nut threads, and Alaska Airlines’ extended end play check interval and the FAA’s approval of that extension, which allowed the excessive wear of the acme nut threads to progress to failure without the opportunity for detection.
The safety issues discussed in this report include lubrication and inspection of the jackscrew assembly, extension of lubrication and end play check intervals, jackscrew assembly overhaul procedures,...Alaska Airlines’ maintenance program...
B747skipper From , joined today!, posts, RR: Reply 3, posted (4 years 10 months 1 week 6 days 19 hours ago) and read 3680 times:
Dear RockyRacoon -
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Generally, T-tail designs are associated with "aft engines" mounted on the fuselage. Apparently, modern designs and concepts of airplanes shy away from such designs, unless of course, the design is derived from older types such as the DC9/MD80-90s leading the way to the B-717...
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Our friends N243NW and FlightSimFreak have mentioned the stall potential problems of the T-tail design, and since these tails are often associated with tail mounted engines, there are similar problems with engines with the stalls.
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Airflow can be disturbed by a stalled wing when it comes to the tail surface, and so are engine inlets, causing inlet "upsets"... and possible "flame-outs"... Many airplanes with such design have a "stick shaker" which gives warning to the pilots of an impending stall condition, and even "stick pushers" to force the nose down, should pilots fail to recover from high angle of attack.
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Further, it has been found that mounting engines in the tail forced the design to provide heavy fuel, hydraulic and electrical lines to the rear of the aircraft, increasing the weight of the airframe... apparently, the Tu134 was designed as a T-tail, engines in the rear version, of the TU124... and that aircraft did end up being a bit heavier...
xxx
I flew the 727 in the past... when we entered potential icing conditions, we had to operate the engine anti-ice AS WELL AS the wing anti-ice, in fear that any ice located at the leading edge of the wing would go into the engines. Even a VHF antenna on top of the fuselage had to be anti-iced, in fear some ice would enter the center engine...
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In the other airplanes I flew, 707, DC8 and now 747, in potential icing conditions we operate engine anti-ice, the wing anti-ice is rarely used... our engines - forward of the wing, would not be damaged by ice removed from the wing.
xxx
So, to my opinion, T-tail and rear engines... are more headaches...
Happy contrails
(s) Skipper
Jetguy From , joined today!, posts, RR: Reply 4, posted (4 years 10 months 1 week 6 days 18 hours ago) and read 3659 times:
T-Tails have their place. I believe that one of best looking aircraft ever designed was the classic 20/30 series Learjet. I think in many instances, the horizontal stab was placed on top of the rudder because that was the only place let to put it where it would be out of the way. About the only real or imagined advantage that I can see for the use of a t-tail is that placing the horizontal stab at the end of the rudder will have a tendency to increase the rudder's effectiveness. The draw backs are many, less pitch authority, deep stall issues, etc. In the case of the Lear, you've got stick shakers and stick pushers. I think that the engineers are trying to tell us something here - they really don't want folks running around stalling the airplane. I wonder why?
One of the problems associated with T-Tails is that they happened to be the aeronautical fad du jour about 25 or 30 years ago, much like winglets are today. Back in the 70's and 80's you saw T-Tails introduced on several single-engine Pipers, the Beech King Air F90 and several other designs where the advantages of a T-Tail were (are) extremely hard to see. It's kind of like mother nature, only the fittest will survive and almost without exception, those light GA aircraft with t-tails have all either gone out of production or reverted back to the standard tail configuration.
SSTjumbo From , joined today!, posts, RR: Reply 6, posted (4 years 10 months 1 week 6 days 17 hours ago) and read 3630 times:
Excellent question RockyRacoon!!! The way I simply see it in my limited experience, if you're coming in a bit steep and at risk of striking the nosewheel first, putting the prop in danger among other things (as in Piper T-hawk), adding just a tad of power won't let you flare out easier. I'm sure somebody can shoot me down on this if I'm wrong. Even more rudimentary than that, if you're in a single-engine prop, you have even less elevator control, a bad thing if you're one of those guys who likes throwing those bad-boy P51 engines in your Piper Arrow IV's, or just happen to simply load too much forward moment on the plane. That's my take.
Pilotpip From United States, joined Sep 2003, 2078 posts, RR: 6 Reply 7, posted (4 years 10 months 1 week 6 days 16 hours ago) and read 3617 times:
Or, in the case of a Seminole, you get a really big left arm from yanking back on the yoke during stalls and slow flight and a really small right arm from spinning the stab trim wheel so much.
There is a noticeable loss of stabilator effectiveness as mentioned before.
Another thing that hasn't been mentioned, the T-tail is a much weaker design structurally. If you ever have the chance to compare a KingAir C90 to an E90 or normal Piper Arrow to an Arrow IV(T-tail model) You will see that the horizontal stabilizer is much bulkier. All of that surface area being moved up there puts a ton of stress on the tail of the aircraft. In conventional designs most of these forces will be placed directly into the airframe. In a T-tail design many of these strong forces are placed upon the empenenage which creates more leverage as it transfers it's forces to the rest of the airframe.
I've flown a turbo arrow with a T-Tail and one without, same basic aircraft otherwise. I can say that I preferred the conventional tail model much more.
Positive rate From Australia, joined Sep 2001, 2143 posts, RR: 0 Reply 8, posted (4 years 10 months 1 week 6 days 15 hours ago) and read 3600 times:
I know it doesn't count for much but T-Tails just looks so much better. Especially on a jet the T-Tail configuration gives it a fast sleek look- the 727 being the perfect example. I prefer T-Tailed jets
Also having rear-mounted engines has its advantages: In the case of an engine failure/shutdown there will be less yaw and the wings are more efficient with the less drag they have due to no engines/pylons hanging off them, and the big advantage= quieter cabin.
MITaero From United States, joined Jul 2003, 497 posts, RR: 7 Reply 9, posted (4 years 10 months 1 week 6 days 15 hours ago) and read 3607 times:
I think the main motivation for building T-tailed aircraft came from the fear that, at higher angles of attack, conventional elevators would be caught in the wake of the wing, decreasing control authority. As mentioned above, there are many other problems which arise from moving the horizontal stab/elevators up.
FredT From United Kingdom, joined Feb 2002, 1993 posts, RR: 15 Reply 10, posted (4 years 10 months 1 week 7 hours ago) and read 3298 times:
T-tails are the ones to get caught in the wake of the wing at high AoAs, as described by FSF and others, leading to the deep stall problems and necessitating stick pushers.
Conventional tails might blank the rudder, making spin entry easier and recovery harder.
The structural weight needed to transfer moments and forces from the elevator to the fuselage through the fin is not negligible.
On the other hand, a T-tail can be smaller as the leverage is longer at the end of the fin. Less induced drag, less weight.
In gliders, landing out in crop is much more of a problem with conventional tails as they tend to catch the crop and break. Ground loops are more prone to snapping the fuselage though, as the yaw acceleration force on the elevator puts torque on it through the leverage provided by the fin.
Getting the elevator out of the slipstream of the propellers can make life easier.
But mainly, I think it comes down to fashion. One of those design choices which has to be made, where you have to balance it all together and arrive at a decision along a process which has to be explainable rather than make actual sense...
Cheers,
Fred
I thought I was doing good to avoid those airport hotels... and look at me now.
Sevenair From United Kingdom, joined Feb 2001, 1728 posts, RR: 0 Reply 11, posted (4 years 10 months 3 days 10 hours ago) and read 3173 times:
One of UK worst accidents (the second worse after lockerbie i think) was in the 70s when a BEA trident left LHR. Soon after takeoff the aircraft entered a stall which progressed to a deep stall, and it fell out of the sky, landing in Staines. The pilot was blamed for retracting leading edge flaps too soon. I forget the particulars of it all
Cfalk From , joined today!, posts, RR: Reply 13, posted (4 years 10 months 2 days 23 hours ago) and read 3117 times:
As I understand it, the T-tail on jets was developed to give room for rear mounted engines. but there are also wing-engined jets that have T-tails, like the C-5 Galaxy and the Avro RJ. Why is that?
Meister808 From United States, joined Jan 2000, 945 posts, RR: 2 Reply 15, posted (4 years 10 months 2 days 20 hours ago) and read 3093 times:
Well, in the case of the C-5, it would be to cut down on Foreign Object Damage (see flightsimfreak's reply above), since the C-5 needs the ability to operate out of unimproved runways. It probably helps in loading through the rear, too, since the elevator is up and out of the way.
As for the ARJ, the reason would be so that they could put the speedbrakes on the back end of the fuselage. These speedbrakes were pretty important in the design of a short-field a/c without thrust reversers, so they had to design the rest of the empennage around them.
Positive rate From Australia, joined Sep 2001, 2143 posts, RR: 0 Reply 16, posted (4 years 10 months 2 days 17 hours ago) and read 3074 times:
Sevenair the captain of the Trident suffered a heart attack very soon after takeoff and it is thought he retracted the leading edge droops at too low an airspeed causing the plane to enter a stall which the automatic stick pusher recovered. One of the other pilots then dumped the auto stick push function and the Trident went into a deep stall which was unrecoverable.
L-188 From United States, joined Jul 1999, 27932 posts, RR: 69 Reply 17, posted (4 years 10 months 2 days 16 hours ago) and read 3066 times:
Nobody is ever going to know what caused that Trident crash exactly. There was a carving made in the flight engineers desk/counter that made some pretty rude comments about the captain on that particular flight. So there is some thought currently that there may have been some CRM issues, but this was long before that term every came into the vocabulary.
But since the crash happened before CVR's and FDR's there is no way to tell for sure what happened. All we have to go on is speculation.
As far as T-Tails, one thing that is nice about them is the fact that they get the horizontal surfaces out of the prop wash on propeller powered aircraft. A bad thing is that they get the horizontal surfaces out of the prop wash on propeller powered aircraft. Getting the tail out of the prop wash will generally smooth out the ride since the turbulent propwash isn't buffeting the hell out of it, but you don't get the benefits of the propwash acting on the tail surfaces. Without the propwash the tail has to rely solely on airspeed for air movement over it, which is one of the reasons you don't see a lot of aerobatic aircraft such as Pitts, Extra's and Sukhoi's running around with T-tails. I suspect it is also the reason why you don't see a lot of T tails on taildraggers either, since the propwash on the tail is what gets the tail up out of the grass at the start of a takeoff run.
I guess the end product is a result of the question, "What are you designing for"
Positive rate From Australia, joined Sep 2001, 2143 posts, RR: 0 Reply 18, posted (4 years 10 months 2 days 14 hours ago) and read 3058 times:
Hey L-188 the BEA Trident accident occured in 1972 and the iarcraft was in fact fitted with a FDR(Flight data recorder). They have been around since the 1950's i think. It didn't have a CVR though(although they were around in '72 i think) so the investigators knew what happened but because there was no CVR they didn't know why it happened.
Justplanesmart From United States, joined Mar 2001, 656 posts, RR: 2 Reply 19, posted (4 years 10 months 2 days 12 hours ago) and read 3050 times:
Many high-wing airplanes have a T-tail, and in addition to some of the reasons stated above, I believe it is to keep the stabilizer out of the wake turbulence caused by the wing. I remember my father telling me something to that effect, and he was an aeronautical engineer.
PMN1 From United Kingdom (Wales), joined Jun 2007, 69 posts, RR: 0 Reply 20, posted (1 month 4 weeks 18 hours ago) and read 1504 times:
Just reading an old 1977 Flight article on the 7N7 and 7X7...
The T-tail was virtually an accident, 7N7 project manager Bob Norton tells Flight. "It took us by surprise. We checke dit out in the wind tunnel because we wnated to use the existing 727 empennage, minus the S-duct". In fact the T-tail turned out to be worth 2% in fuel consupmtion without adding to the weight. As now planned the 7N7 will have a modified 727 tail unit, and Nortan says the tunnel testing has revealed no superstall problem.
Starlionblue From Greenland, joined Feb 2004, 12561 posts, RR: 55 Reply 21, posted (1 month 4 weeks 5 hours ago) and read 1384 times:
Quoting PMN1 (Reply 20): The T-tail was virtually an accident, 7N7 project manager Bob Norton tells Flight. "It took us by surprise. We checke dit out in the wind tunnel because we wnated to use the existing 727 empennage, minus the S-duct". In fact the T-tail turned out to be worth 2% in fuel consupmtion without adding to the weight. As now planned the 7N7 will have a modified 727 tail unit, and Nortan says the tunnel testing has revealed no superstall problem.
That would be this one I believe:
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