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Aircraft Wing construction Wings: The wings of an aircraft are surfaces designed to give lifting force when moved rapidly through the air. The particular wing design for any given aircraft depends on a number of factors, such as size, weight, use of the aircraft, desired speed in flight and at landing, and desired rate of climb. The wings are designated as left and right, corresponding to the left and right hands of the pilot seated in the cockpit or the pilot'scompartment. Engines mounted on wings are numbered from the left wing to the right. Design: The wings of military or large commercial aircraft are usually of cantilever design; that is, they are built so that no external bracing is needed. With few exceptions, wings of this design are of the stressed skin type, which means that the skin is a load-bearing part of the wing structure. Wing construction: In general, wing construction is based on one of three fundamental designs: monospar (one), multispar (two or more), or box beam. Slight modifications of these basic designs may be adopted by various manufacturers. The monospar wing incorporates only one main longitudinal member (spar) in its construction. Ribs or bulkheads supply the necessary contour or shape to the airfoil. Although the strict monospar type wing is not common, this type of design, modified by the addition of false spars or light shear webs along the trailing edge as support for the control surfaces, is often used. The multispar wing incorporates more than one main longitudinal member (spar) in its construction. To give the wing contour, ribs or bulkheads are often included. This type of construction, or some modification of it, is used in the lighter types of combat aircraft. The box-beam typeof wing construction uses two main longitudinal members with connecting bulkheads to furnish additional strength and to give contour to the wing. A corrugated sheet may be placed between the bulkheads and the smooth outer skin so that the wing can better carry tension and compression loads. In some cases, heavy longitudinal stiffeners are substituted for the corrugated sheets. A combination of corrugated sheets on the upper surface of the wing and stiffeners on the lower surface is sometimes used. Other variations in wing design are necessary because of the angle at which the wing attaches to the fuselage. As shown in below figure, wings angled upward have positive dihedral, and wings angled downward have negative dihedral. The wing

tip may be square, rounded or even pointed. Both the leading edge and the trailing edge of the wing may be straight or curved. In addition, one or both edges may be tapered so that the wing is narrower at the tip than at the root where it joins the fuselage. Numerous types of modern aircraft use swept back wings.

Construction Futures: The main structural parts of a wing- the spars, ribs, stringers or stiffeners, and skin are illustrated in below figure. These structural parts are riveted or welded together.

Spars: Spars are the principal structural members of the wing. They correspond to the longerons of the fuselage. They run parallel to the lateral axis, or toward the tip of the wing, and are usually attached to the fuselage by wing fittings, plain beams, or part of a truss system. The I-beam type of construction for a spar consists of a web (the deep wall plate) and cap strips (which in reality are extrusions or formed angles). These carry the loads caused by the wing bending, and also provide a foundation for attaching the skin. Stiffeners give additional strength to the spar structure. Stiffeners may be

beads pressed into the web or extrusions or formed angles riveted to the web, either vertically or diagonally. Detail of above figure, shows a typical I-beam type of spar.

Ribs: Ribs are the cross-pieces that make up the framework of the wing. They run from the leading edge toward the trailing edge (front to rear) of the wing. The ribs are secured to the spars, and since they are curved. They give the wing its aerodynamic shape when it is covered with the skin. Ribs transmit the load from the skin to the spar. There are two general types of ribs construction, as shown in below figure. The reinforced rib is relatively heavy as compared to the formed rib, and is located only at points where the greatest stresses are imposed. Formed ribs are located at frequent intervals through the wing. The reinforced rib is similar in construction to spars, consisting of upper and lower capstrips joined by a web plate. The web is reinforced between the capstrips by vertical and diagonal angles.

Formed ribs are made of formed sheet metal and are very light in weight. The

bent-up portions of a formed rib are referred to as the flanges, and the vertical portion is called the web. The web is constructed with lightening holes, with beads formed between the holes. The lightening holes lessen the weight of the rib without decreasing the strength. Flanging the edges of the lightening holes helps maintain the rigidity of the web. The beads stiffen the web portion of the rib.

Stringers: Stringers or stiffeners are attached to the skin where high compressive loads arc encountered, or where a shape must be held. These are usually found closely spaced on the underside of the upper wing skin, where stiffening demands become extreme, the skin is usually reinforced by a corrugated panel or honeycomb sandwich instead of individual stringers. Cross sections of typical stiffened panels are shown in below figure.

Skin: The skin used as wing covering is quite strong in tension and shear. The skin is employed as a primary load-carrying member in wing construction. The thickness of wing skin varies widely, depending upon the stresses encountered. Thicknesses vary from as low as inch in small aircraft to as much as . inch in the wings of heavy bombers. If weigh reduction is of prime importance, the skin is tapered so that the proper amount of strength is provided.

In the last few years, machine milled skins (below figure) have become routine in the aircraft industry. Many parts on high performance aircraft have been redesigned for machine milling. This process results in fewer parts, fewer fasteners, decrease in weight, easier assembly, greater load carrying capacity, and easier field repairs. Many different machines are required to machine mill skins. They

include vertical milling machines, horizontal milling machines, detail milling machines, drilling machines, and routing machines.

Chem-milling is a process used to shape metals to an exacting tolerance by chemical removal, or deep etching, rather than by conventional mechanical

milling or machining operations. Originally developed as a means of providing increased metal thickness, at the edges to be butt-welded, the chem-mill process has mushroomed into a full-scale production tool. Designs which were once avoided as impossible to produce, or prohibitive in cost are being achieved daily in chem-milling facilities.

Chem-milling or etching, is the immersion of a part in an etching solution to remove metal and leave a predetermined design. The etching solution dissolves the metal not only in a direction perpendicular to the exposed surface, but also undercuts the mask. That is, the solution cuts underneath the mask approximately as far as it cuts into the metal. A series of tanks filled with special solutions are arranged to allow a rapid transfer of parts from one to another as etching and rinsing proceeds. The depth of metal removed depends on the time of immersion in the etching solution. Honeycomb panels are also used as skin coveringon certain sections of the wing.

The type of honeycomb assemblies most commonly used consists of a honeycomb core of aluminum foil and then aluminum facing material bonded together with an adhesive. You can recognize honeycomb assemblies by their thin outer skin, the absence of fasteners and the light weight of the complete assembly.

Below figure shows one type of honeycomb skin panel assembly.

Wing sections: The leading edge, center section and trailing edge section are the three sections that make up an aircraft wing (front to rear). The leading edge is the front section of the wing. The purpose of the leading edge is to streamline the forward section of the wing. The space within the leading edge is sometimes used to house extra equipment such as landing lights, plumbing lines or thermal anti-

icing systems. Leading edges constructed with thermal anti-icing systems consist of two layers of skin separated by a thin airspace. The center section of the wing is from the front spar to the rear spar. This is the main structural section of the wing. All external structures are attached to this section. The space within this section is sometimes used to store fuel, and on fighter type aircraft this space serves as housing for the landing gear. The center section is where the wing walkway areas are located. The trailing edge section is the rear most part of the wing. Attachments for the control surfaces are located within this section.

External structures: On multiengine type aircraft, the streamlined structural units placed around the aircraft engines to provide a smooth surface for airflow are called nacelles. The nacelles on jet aircraft are attached to a strut which in turn is attached to the center section of the wing. Below figure depicts this type of design.

On propeller driven aircraft, the nacelle is built as the part of the wing itself. Below figure illustrates the internal structural units for a built-in type nacelle. The construction features are similar to that of the fuselage. On twin-engine aircraft, the nacelles also house the wing landing gears and related equipment. On a four engine aircraft, the landing gear is enclosed in the inboard nacelles. An engine cowling with quick release type fasteners and latches provides access to the engine within the nacelle.

Fairings: Fairings are auxiliary members that streamline various parts and locations on the aircraft to reduce drag. They cover the joints formed where wing sections meet the fuselage and where the vertical and horizontal stabilizers mount on the main structure. They are often used to streamline around fittings, navigation lights, landing gear struts, wheels, and the like. Fairings are not strength members and are not intended to carry any of the principal loads placed on the aircraft structures.

‫نکات مهم در طراحی بال هواپیماهای مسافربری‪:‬‬ ‫در طزاحی تال َّاپیوا یاسدُ پاراهتز اصلی ٍجَد دارد وِ ػثارتٌذ اس‪:‬‬ ‫‪ .1‬هساحت هزجغ تال(‪)S‬؛‬ ‫تؼییي دٍ هتغییز دٌِّ تال(‪ٍ ٍ )Span‬تزهتَسط آیزٍدیٌاهیىی(‪ )Mean Aerodynamic Chord‬در‬ ‫ایي لسوت اس اّویت سیادی تزخَردار است‪.‬‬ ‫‪ .2‬هحل ػوَدی ًصة تال؛‬ ‫تطَرولی چْار هحل ًصة تال تِ تذًِ ٍجَد دارد وِ ػثارتست اس‪:‬‬ ‫‪ ‬تال تاال (‪)High Wing‬؛‬ ‫‪ ‬تال ٍسط (‪)Mid Wing‬؛‬ ‫‪ ‬تال پاییي (‪)Low Wing‬؛‬ ‫‪ ‬تال تاالتز (‪)Parasol Wing‬؛‬ ‫‪ .3‬همطغ تال(‪)Airfoil‬؛‬ ‫ایزفَیل ًمش اصلی خَد را در حالت ‪ Cruise‬ایفا هیوٌذ یؼٌی در حالت تؼادل ًیزٍیی تایستی‬ ‫ضزیة ‪ Lift‬تیشتز اس ضزیة ‪ Drag‬تاشذ ٍ ایي هالن اًتخاب یا طزاحی ایزفَیل است‪.‬‬ ‫‪ ‬طزاحی همطغ ایزفَیل؛‬ ‫طزاحی ایزفَیل پزّشیٌِ ٍ ًیاسهٌذ اهىاًات گستزدُ ٍ هتخصصیي ستذُ دارد‪.‬‬ ‫‪ ‬اًتخاب اس هماطغ استاًذارد؛‬ ‫ایزفَیلّای ساسهاى َّافضای هلی آهزیىا (‪ ٍ )NACA‬یا ‪ NASA‬هؼزٍفیت تیشتزی‬ ‫دارًذ‪.‬‬ ‫‪ ‬هشخصات ػوَهی ایزفَیل‪:‬‬

‫تا تَجِ تِ تزرسیّای اًجام شذُ‪ّ ،‬زچِ ساٍیِ حولِ ایزفَیل تیشتز شَد ضزیة ‪ )Cl( Lift‬تیشتز هیشَد تا‬ ‫آًجا وِ شزٍع تِ افت هیوٌذ وِ تِ ایي ًمطِ‪ً ،‬مطِ ٍاهاًذگی (‪ )Stall‬گَیٌذ‪ .‬ایي ساٍیِ تمزیثا" تیي ‪ 11‬تا‬ ‫‪ 15‬درجِ (تستِ تِ ًَع ایزفَیل تزای َّاپیواّای هسافزتزی) دارد‪.‬‬

‫‪ً .4‬سثت هٌظزی(‪)Aspect Ratio‬؛‬ ‫‪ً ‬سثت دّاًِ تال تِ ٍتز هتَسط آیزٍدیٌاهیىی تال است ‪.‬‬ ‫‪‬‬


‫‪b‬‬ ‫( )‪AR  (Rectangular ), AR  b (Trapze‬‬ ‫‪c‬‬ ‫‪S‬‬


‫‪ ‬اثزات ًسثت هٌظزی‪:‬‬

‫‪ّ ‬زچِ تال دٍرتز اس ریشِ تاشذ اثز گزداب تال ووتز است‪.‬‬

‫‪ّ ‬زچِ ًسثت هٌظزی افشایش یاتذ‪ ،‬ساٍیِ ٍاهاًذگی واّش خَاّذ یافت چَى ساٍیِ‬ ‫حولِ هَثز ًَن تال افشایش هییاتذ‪.‬‬ ‫‪ّ ‬زچِ ًسثت هٌظزی افشایش یاتذ‪ٍ ،‬سى افشایش خَاّذ یافت‪.‬‬ ‫‪ّ ‬زچِ‬


‫افشایش یاتذ‪،‬‬


‫‪ L D‬‬

‫تزای َّاپیواّای هادٍى صَت واّش هی‪-‬‬


‫‪ّ ‬زچِ ًسثت هٌظزی واّش یاتذ‪ ،‬پسا افشایش هییاتذ‪.‬‬ ‫‪ً .5‬سثت هخزٍطی(‪)Taper Ratio / ‬؛‬ ‫‪ً ‬سثت تیي ٍتز ًَن تال تِ ٍتز ریشِ تال است‪.‬‬ ‫‪ ‬تِطَرولی ًسثت تاریه شًَذگی تیي یه(تال هستطیلی) ٍ صفز(تال هثلثی) است‪.‬‬ ‫‪ ‬اصلیتزیي هؼیار تؼییي ًسثت هخزٍطی‪ ،‬رساًذى تَسیغ تزآ رٍی تال تِ شىل تیضَی است‪.‬‬ ‫‪ ‬اثزات ایي ًسثت ػثارتٌذ اس‪:‬‬ ‫‪ ‬تَسیغ تزآ رٍی تال را تغییز هیدّذ‪.‬‬

‫‪ ‬واّش ایي پاراهتز ساخت را هشىلتز وزدُ ٍ ّشیٌِ ساخت را تاال هیتزد‪.‬‬ ‫‪ ‬واّش ایي ًسثت‪ٍ ،‬سى را واّش هیدّذ‪.‬‬

‫‪ .6‬پیچش( ‪)Twist / t‬؛‬ ‫در صَرتی وِ ساٍیِ حولِ ًَن تال تا ساٍیِ حولِ ریشِ تال تفاٍت داشتِ تاشذ‪ ،‬تال دارای پیچش‬ ‫است‪ .‬در صَرتی وِ ساٍیِ حولِ ًَن تال تیشتز تاشذ‪ ،‬پیچش هثثت(‪ ٍ )Wash-in‬در صَرتی وِ‬ ‫ووتز تاشذ هٌفی(‪ )Wash-out‬است‪ .‬ػوَها" در َّاپیواّا پیچش هٌفی تَدُ ٍ تیي صفز تا ‪-3‬‬ ‫درجِ است‪.‬‬ ‫‪ ‬دٍ دلیل اصلی پیچش تال ػثارتست اس‪:‬‬ ‫‪ ‬جلَگیزی اس ٍاهاًذگی ًَن تال لثل اس ریشِ تال؛‬

‫‪ ‬تغییز تَسیغ تزآ تِ یه تَسیغ تیضَی؛‬ ‫‪ٍ ‬جَد پیچش هٌفی تاػث واّش تزآ هیشَد ٍلی در ػَض اس ًظز ایوٌی هشىل ٍاهاًذگی‬ ‫حل شذُ است‪.‬‬

‫‪ ‬اًَاع پیچش‪:‬‬

‫‪ ‬پیچش آیزٍدیٌاهیىی‪ٍ :‬لتی ایزفَیل ریشِ ٍ ًَن تال هتفاٍت تاشذ وِ اس ًظز‬ ‫ساخت هشىلتز است‪.‬‬ ‫‪ ‬پیچش ٌّذسی‪ٍ :‬لتی وِ ایزفَیل ریشِ ٍ ًَن یىساى تاشذ‪.‬‬

‫‪ .7‬ساٍیِ ػمةگزد(‪)Sweep‬؛‬ ‫ٌّگاهیوِ لثِ حولِ تال یا خط گذرًذُ اس درصذ خاصی اس ٍتز هحلی تا هحَر ػزضی َّاپیوا ساٍیِ‬ ‫داشتِ تاشذ هیگَیٌذ تال ػمةگزد دارد‪ .‬اگز ًَن تال تِ سوت دم هتو��یل تاشذ‪ ،‬ػمةگزد تِ ػمة‬

‫ٍ اگز تِ سوت دهاغِ هتوایل تاشذ‪ ،‬ػمةگزد تِ جلَ یا جلَگزد گَیٌذ‪ .‬ایي ساٍیِ را تا ‪ً ‬شاى هی‪-‬‬ ‫دٌّذ‪.‬‬ ‫‪ ‬ػمةگزد تِ دالیل سیز السم است‪:‬‬

‫‪ ‬تْثَد شزایط در سزػتّای تاالی حذٍد صَت یا هافَق صَت تا تاخیز اًذاختي‬ ‫اثزات تزاونپذیزی‪.‬‬

‫‪ ‬تٌظین هزوش ثمل َّاپیوا ٍ هزوش آیزٍدیٌاهیه تال تِ طَری وِ تِ ّن ًشدیهتز‬ ‫شًَذ‪.‬‬ ‫‪ ‬تْثَد پایذاری طَلی ٍ سوتی تزای َّاپیواّای تذٍى دم‪.‬‬ ‫‪ ‬افشایش دیذ خلثاى تِ خصَص در َّاپیواّای ًظاهی‪.‬‬

‫‪ .8‬سزاشیثی یا ّفتی تال (‪)Dihedral / ‬؛‬ ‫‪ ‬در ًوای جلَی َّاپیوا‪ ،‬ساٍیِ تال تا افك است‪.‬‬ ‫‪ً ‬مش اصلی آى‪ ،‬تاهیي پایذاری ػزضی است (‪ )Rolling Stability‬یؼٌی تا چزخش حَل‬ ‫هحَر ‪ّX‬ا‪ّ ،‬فتی آى را تِ حالت افمی تاس هیگزداًذ‪ .‬تال تاال‪ ،‬تاثیز ّفتی تال را تمَیت‬ ‫وزدُ ٍ تال پاییي‪ّ ،‬فتی را تضؼیف هیوٌذ‪.‬‬ ‫‪ ‬تٌاتزایي سزاشیثی تال‪ ،‬تاػث افشایش پایذاری هیگزدد‪.‬‬ ‫‪ .9‬ساٍیِ ًصة تال(‪)Incidence Angle / set‬؛‬ ‫‪ ‬ساٍیِ تیي ٍتز ریشِ تال ٍ خط هزوشی تذًِ را گَیٌذ‪.‬‬ ‫‪ ‬ایي ساٍیِ هیتَاًذ ثاتت ٍ یا هتغییز تاشذ وِ هتغییز تَدى آى اس ًظز ایوٌی ٍ افشایش ٍسى‬ ‫ًیاس تِ توْیذات تیشتزی دارد‪.‬‬ ‫‪ ‬ایي ساٍیِ تایذ آى لذر تاشذ تا ضزیة ‪ Drag ٍ Lift‬السم را در طَل پزٍاس ایجاد وٌذ‪.‬‬ ‫‪ ‬ایي ساٍیِ تِطَر ولی در َّاپیواّای دستساس ػوَهی حذٍد ‪1‬تا‪ 3‬درجِ؛ در َّاپیواّای‬ ‫حول ٍ ًمل هسافزی حذٍد ‪3‬تا‪ 5‬درجِ ٍ در َّاپیواّای جٌگٌذُ حذٍد صفز تا ‪ 1‬درجِ‬ ‫است‪.‬‬

‫‪ًَ .11‬ع تزآ افشا (‪ ٍ )Flap‬اتؼاد ٍ ساٍیِ چزخش آى؛‬ ‫‪ ‬تزآ افشا جشء سطَح وٌتزل ثاًَیِ تَدُ وِ تِ ػٌَاى اتشار افشایش ‪ Lift‬تِخصَص در ًشست‬ ‫ٍ تزخاست‪ ،‬استفادُ هیشَد‪ .‬ایي اتشار چْار ػول تز رٍی تال اًجام هیدّذ‪:‬‬ ‫‪ ‬ضزیة تزآی تال را افشایش هیدّذ‪.‬‬

‫‪ ‬ساٍیِ حولِ تزآی صفز را هٌفیتز هیوٌذ‪.‬‬

‫‪ ‬ساٍیِ ٍاهاًذگی تال را واّش دادُ ٍ تال سٍدتز ٍاهاًذُ هیشَد‪.‬‬ ‫‪ ‬سزػت ٍاهاًذگی را واّش هیدّذ‪.‬‬ ‫‪ ‬هحلّای ًصة تزآ افشا‪:‬‬

‫‪ ‬لثِ حولِ تال(‪.)Leading Edge Flap‬‬ ‫‪ ‬لثِ فزار تال(‪.)Trailing Edge Flap‬‬

‫‪ ‬اًَاع هختلف تزآ افشا‪:‬‬

‫ًىات هْن‪:‬‬ ‫‪ ‬هؼوَال" تزآ افشا در لسوت داخلی تال (‪ً ٍ )Inboard‬شدیه تذًِ ٍلی شْپزّا در لسوت خارجی‬ ‫تال لزار هیگیزًذ‪ .‬ػلت آى واّش گشتاٍر تزآ افشای تال ٍ افشایش راحتی وٌتزل (افشایش گشتاٍر‬ ‫شْپزّا) هیتاشذ‪.‬‬ ‫‪ّ ‬زچِ هساحت تال تیشتز تاشذ‪ ،‬تایستی تزآ افشا ضؼیفتز تاشذ‪.‬‬ ‫‪ّ ‬زچِ ٍسى تیشتز تاشذ تایستی تزآ افشا‪ ،‬لَیتز تاشذ‪.‬‬ ‫‪ .11‬شْپز (‪)Aileron‬؛‬ ‫‪ ‬شْپز در ایجاد گشتاٍر چزخشی(‪ ٍ )Roll‬وٌتزل دٍر سدى دخالت دارد‪.‬‬ ‫‪ ‬تا حزوت هؼىَس رٍی دٍ تال‪ ،‬تیي دٍ تال اختالف تزآ ایجاد وزدُ ٍ تاػث چزخش هی‪-‬‬ ‫گزدد‪.‬‬ ‫‪ ‬تْتزیي هحل آى لثِ فزار تال ٍ تیي ‪ 2 3‬تا ‪ 3 4‬دٌِّ است‪.‬‬

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