Started, Advertising & The optimal treatment strategy for acute exacerbation of COPD in the ICU next to the well-known benefits of noninvasive ventilation (NIPPV) is unknown The aerodynamic consequences of a T-tail have most to do with stability and control in stall and post-stall behaviour, and can be grave. You might see V-Tails used on high-performance models, such as slope soaring or discuss launch gliders. The T-tail raises the tailplane out of the fuselage drag-hole which can reduce your tailplane effective aspect ratio by 20% or more. So I make it a point to "fly" the nose more deliberately with t-tail airplanes. Others have given you aerodynamic reasons (which are all very good), but a reason why most military cargo planes have t-tails is also because it allows for larger loading ramps at the tail. This distance gives the plane leverage and enables the tailplane to control the aircrafts pitch attitude. Answer (1 of 17): A T-tail increases manufacturing and operating costs. However, T-tails are more likely to enter a deep stall, and is more difficult to recover from a spin. Beautiful shots taken while the sun is below the horizon, Accidents With taildragger landing gear, the secondary wheel is behind the two primary wheels. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Name as many disadvantages and advantages of each that come to mind. Conventional. The 200-HP Piper Arrow is an unremarkable performer; the 180-HP version is, well, doggy. My thoughts on 159 hours in rented T-tail Turbo Arrows One nice feature on my Sky Arrow is that the position of the CG means that if you lower the tail to the ground it stays there: I think the OP was asking about 'real' planes. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. Anything related to aircraft, airplanes, aviation and flying. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Source: I study aeronautical engineering and we had to do an exercise involving finding the correct posistion for the HTP to minimize downdraft. There can also be some slight negatives in terms of efficiently generating pure pitch or yaw moments without also generating unwanted roll moments. [citation needed], Depending on wing location, the elevator may remain in undisturbed airflow during a stall. The T-tail lifts the horizontal tail clear of the wing wake (downwash) and propwash, which make it more efficient and hence allow reducing its size and also allows high performance aerodynamics and excellent glide ratio as the horizontal tail empennage is less affected by wing slipstream. Most aircraft feature empennage incorporating vertical and horizontal stabilizing surfaces which stabilize the flight dynamics of pitch and yaw as well as housing control surfaces. With tricycle landing gear, the secondary wheel is in front of the two primary wheels. In the 1960s, several passenger jets with rear-fuselage-mounted engines featured T-tails, such as the BAC One-Eleven, the Vickers VC10, the McDonnell Douglas DC-9, the Boeing 727, the Fokker F28 Fellowship, and the Russian Ilyushin Il-62 and Tupolev Tu-154. What is (theoretically) the most efficient shape for an aircraft, assuming you don't have to carry any cargo? For the pilots its interesting to note that if you apply thrust it has a pitch down tendency (when engines mounted rear) because the engines are above the C.G. Observed form behind, this looks like the capital letter T. Sometimes the term is used to refer to an aircraft with such empennage. The C2 has a conventional tail rotor: The RPM of the tail rotor on the C2 is roughly 2150 RPM. Are there tables of wastage rates for different fruit and veg? I too love the look of a V tail, and soon enough ill be trying my first V tail home build! [citation needed] T-tails can be harder to inspect or maintain, due to their height.[3]. The conventional cross tail is the easiest to design, modify during the development process and adjust during set up of a new model. The main advantage of a T-tail is that during normal flight conditions the elevator is above most of the effects of downwash from the propeller (in case of a propeller-driven aircraft) and the airflow around the fuselage and wings. Quiz: Can You Identify These 7 Cloud Formations? T-tails have a good glide ratio, and are more efficient on low speed aircraft. Popular in fighter jets: Twin Tail, aka Double Vertical Stabilizer. The tail provides stability and control for the aircraft in flight. A stabilizer in undisturbed airflow will produce better L/D than in turbulent flow, as well. . The conclusion of this study cannot be drawn without a specific example but I hope it is clear for you that stability is really impacted by the choice of the tail. Rotate at 75 knots. Human Error in Aviation and Legal Process, Stabilised Approach Awareness Toolkit for ATC, Flight Deck Procedures (A Guide for Controllers). There can be practical considerations, like them being less likely to drag in the grass. T-tails must be stronger, and therefore heavier than conventional tails. In comparison with conventional-tail aircraft, the elevator on a T-tail aircraft must be moved a greater distance to raise the nose a given amount when traveling at slow speeds. Sounds good, but if you examine engine FOD statistics, the MD80 actually has a higher rate of engine FOD events than the 73Classic/NG. Learn more about Stack Overflow the company, and our products. Given the option, I preferred the conventional tail. The stabilator, which is 13% smaller in span and area than that of a Warrior/Archer/low-tail Arrow, is up out of the energized propwash, so it seems ineffective. 5. Ascended Master. What leaves me questioning is that almost all large commercial aircraft feature a conventional tail (B747, B777, A340, A380) while most military aircraft of a similar or larger size have a t-tail (C-17, C-5), and then if you get even larger (AN124, AN225) you're back to having a conventional tail again. Why do T- tail airplanes have a shorter vertical stabilizer? (https://www.airliners.net/discussions/tech_ops/read.main/138372/). Subscribe to get the latest videos, articles, and quizzes that make you a smarter, safer pilot. The Boeing 737 was initially planned with rear-mounted engines, like the Sud-Aviation Caravelle, which it was meant to replace. In this condition, the wake of the wing blankets the tail surface and can render it almost ineffective. Swayne is an editor at Boldmethod, certified flight instructor, and a First Officer on the Boeing 757/767 for a Major US Carrier. In fact, I was under the impression that a major disadvantage of a T-tail was that the wash during a stall could envelope the tail and remove the authority needed to correct the situation. Asking for help, clarification, or responding to other answers. It ensures clean airflow, at least on gulfstream aircraft. It also helps to reduce wave drag, especially when using a well designed Kchemann body (the round, long, spiky thing on the tail junction of a Tu-154) by stretching the structure lengthwise. Why did the F-104 Starfighter have a T-tail? This is the small wing-like protrusions from the main tail, or rear of the fuselage. Reduces stick lightening: The greater height of T-tail can help reduce stick lightning caused by the conventional tail after entering the wake while maneuvering. Quiz: Can You Identify These 6 Uncommon Airport Lighting Systems? There are several things to consider in a T-tail design. Quiz: Do You Know What These 5 ATC Phrases Mean? The reason for this is the reversal of the $C_M$ - $\alpha$ slope of T-tails, as depicted below. Manufacturing cost because the vertical stabilizer needs to be built that much stronger to handle additional mass and aerodynamic forces that are now on the end of a long, slender lever. That additional weight means the fusel. The T-tail increases the effectiveness of the vertical tail because of "end plate" effect. When the vertical tail is swept, the horizontal tail can be made smaller because it is further rearwards and therefore has a greater lever arm. If you look at the Rafale planform you see that it has a small LERX on the wing and another on the canard (this one is really thick and rounded, but it will still have similar function aerodynamically). It is structurally more compact and aerodynamically more efficient. Now, I'm not entirely sure about this, but the lift from the Wings generates what is approximated as a so called Horseshoe-Vortex. Sponsorships. Press question mark to learn the rest of the keyboard shortcuts. Lighter: V-tail-designed aircraft is lighter compared to the conventional tail configuration of other aircraft designs. The T-tail is very common on aircraft with engines mounted in nacelles on a high-winged aircraft or on aircraft with the engines mounted on the rear of the fuselage, as it keeps the tail clear of the jet exhaust. Aside from the aforementioned lack of propwash, because a T-tail is usually further aft and has more lever arm, it can be made smaller, with less overall drag. There were a LOT of legit proposals out there. I would say that the use of V tails has almost nothing to do with performance. Props and jets from the good old days, Flight Decks The loss of Alaska Airlines Flight 261 was attributed to improper maintenance of the T-tail. Twin tail (also referred to as H-tail) or V-tail are other configuration of interest although much less common. The horizontal stabilizer acts like a winglet, reducing induced drag of the rudder. its more stable in turbulent conditions and centerline thrust (in case of engine failure). 3 7 comments Add a Comment MathJax reference. All rights reserved. Why Britain fell in love with the T-tailed aeroplane", "What Are The Advantages And Disadvantages Of T-Tails? Typical values are in the range of 8% to 10%. Other common tail designs: V-Tail, T-Tail, Cruciform, Dual-Tail, Inverted Y. Get below 95 kts on final (especially with just one or two people up front) and the wing will start to blank out the tail and things get squirrely. You just compared RC airplane design and quality to FAA certified airplane design and quality. The AC isn't prescriptive. However, the downwash induced by the main wing on the flow is taken into account (for the cruise conditions) in the design of the tail in order to reduce some negative aspects of the interaction between the main wing and the tail. Why is this sentence from The Great Gatsby grammatical? On light airplanes, the primary reason that T-tails were used was aesthetics. MCDONNELL DOUGLAS MD-82) because it removes the tail from the exhaust blast. We hope you found this article helpful. List price for the PT is a little cheaper than conventional, but you have to buy a plug tail separately. For the elevator, when the stick is pulled back, both ruddervators deflect upwards much like on a normal elevator (just think of this one as having an upward bend in the middle of it). Not only for the aerodynamic loads, but for the elevator and elevator trim mechanisms. 4. Anyway, from what I've been told: The T-tail sticks the elevators out of the disturbed air of the wings, prop, and (usually most of) the fuselage which gives you better elevator authority, and makes a tail stall less likely. Rear mounted engines also require more fuselage structure. Here's how they're different than conventional tail configurations. This is because there is generally less surface area needed for a V-Tail (you have two surfaces cutting through the air, not three). There is no prop wash over the elevator. receive periodic yet meaningful email contacts from us and us alone. Rear mounted engines would also be much closer to the centerline of the aircraft, reducing the controllability issues in an engine out scenario. Accident, incident and crash related photos, Air to Air The resulting drag is what counts. This is a lot lower compared to the Fenestron RPM of roughly 3150 RPM (about 50% higher RPM! Provides smooth flow: A T-tail ensures the tailplane surfaces behind the wings are out of the airflow. Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. As your AOA increases the wash from the wings will come closer and closer to the tail, not further, and so your tail will become more and more inundated by the wash, rather than less in the case of a conventional tail. Zero tail swing vs normal tail swing. T-tails keep the stabilizers out of the engine wake, and give better pitch control. Reduced and zero tailswing models have become popular due to their easy maneuverability in urban and residential areas where space is limited. This occurs because the stabilator sits up out of the . With heavy attachments or loads the zero swing is likely to pitch more than a conventional machine. In a normal tailed engine aircraft, when the pilot increases power, he gets wind over the tail and has control authority of the aircraft. It can help to increase the effectiveness of the vertical tail by keeping the air on both sides of it separated. Quiz: Do You Know These 6 Common Enroute Chart Symbols? Rudder authority: T-tail design gives you a better rudder authority when flying at a very high AOA and stalls thus preventing a spin. The duct is integrated into the tail boom and is usually made of a fiberglass skin. Why is this the case? Also, approaching a stall, you will have more elevator effectiveness with the T-tail, as the wing wash is below the horizontal stabilizer. Most of the entries in the NAME column of the output from lsof +D /tmp do not begin with /tmp. Note that the increased leverage means that the horizontal tail can be smaller as well. The simple answer is that they can be more efficient than a conventional tail. Inadequate maintenance of t-tail may lead to loss of control of the aircraft on air. Before CFD, mounting the engines on the wing created lots of problems, prompting the engineers to move to tail-mounted engines in their next design (DC-8 -> DC-9, B707 -> B727), The mass of the horizontal tail on a long lever arm (= the vertical tail) means that the torsional eigenfrequency of the fuselage will go down. The most noticeable difference is that V tail aircraft are much more sensitive to being loaded tail-heavy. Why are the Antonov An-124 horizontal stabilisers directly behind the wings? It has some drawbacks though, by putting the elevators directly in the (turbulent) separated flow from the wings during a stall can put you in a (more or less) unrecoverable deep stall. By designing the junction with the vertical well, the T-tail has less interference drag. I could imagine that the HTP is moved up to the T-configuration to ensure that the direction of air movement over the stabilizer is horizontal and not vertical. As I already explained in this answer, the tail is used to create some lift that is required to fulfil the trim relations. Discussion in 'Flight Following' started by kontiki, Aug 5, 2012. T-tails are also sometimes chosen to provide additional separation from non-sky (as in sea planes). T-tails are also often used when engines are mounted to the rear of the fuselage as often seen on business jets. Dunno. obtain an immediate elevator authority by increasing the aircraft power. Don't have an account? Frequent air travellers would have noticed different aircraft for longer and shorter air routes. I really don't care either way except to be ready for the different feel on takeoff and the flare. A T-tail produces a strong nose-down pitching moment in sideslip. This is due to the fact that the stabilator sits up out of the propwash, and so is less effective at low airspeeds. 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