CONCEPTUAL DESIGN & TAKE-OFF WEIGHT ESTIMATION OF ATTACK FIGHTER AIRCRAFT

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1 Proceeding of the International Conference on Mechanical Engineering and Renewable Energy 2015 (ICMERE2015) November, 2015, Chittagong, Bangladeh ICMERE2015-PI-256 CONCEPTUAL DESIGN & TAKE-OFF WEIGHT ESTIMATION OF ATTACK FIGHTER AIRCRAFT Afani Kahem Prokrity 1,*, K. M. Atiq Adnan 2 and Nadia Mahmud Military Intitute of Science & Technology (MIST), Bangladeh 1,* afaniprokrity@gmail.com, 2 adnan.atiq09@gmail.com, 3 nadiakanta57@gmail.com Abtract- Aircraft deign include three important phae; conceptual deign, preliminary deign & detail deign. Thi paper deal with the conceptual deign & a part of preliminary deign (maximum take-off weight etimation) of an attack fighter aircraft. Conceptual deign include the initial configuration of the aircraft from recent trend & hitorical obervation. Preliminary deign phae include calculation of maximum take-off weight, wing loading & engine thrut for the aircraft. In thi paper conceptual deign & the calculation of maximum take-off weight are done. In cae of calculating maximum take-off weight, weight lo due to bomb drop i conidered which i abent in general aircraft. Keyword: Conceptual deign, Preliminary deign, Aircraft deign 1. INTRODUCTION Attack fighter aircraft deign varie from normal aircraft deigning. The purpoe & miion profile of the fighter aircraft i quite different from that of the normal tranport, commercial or trainer aircraft. It include weight drop, more controllab than tab due to it baic purpoe & complex the miion profile. Conceptual deign provide the very baic conideration for the aircraft deign. Preliminary deign include calculation of maximum take-off weight and engine thrut. In thi paper, we completed the conceptual deign and calculation of maximum take-off weight for given miion profile. Conceptual deigning wa done by conidering both hitorical data and recent trend. In cae of calculating maximum take-off weight, we had to conider the attack egment where weight lo occurred due to bomb drop. Our tak wa to deign an attack fighter aircraft for the following condition: Table 1: Miion requirement Parameter Minimum Requirement Range 1150 km Or, 620 nm Maximum Mach No..62 Ceiling ft Payload Load Factor +9-3 Crew 1 Miion profile for thi i given below: Fig.1: Miion profile 2. CONCEPTUAL DESIGN Figure of merit analyi wa ued to find the appropriate configuration. mean Weight of merit. Better option wa marked by a higher value. Thi value range from 5 to Selection of Wing Type Table 2: Selection of wing Mono-pl ane Bi-pl ane Delta wing Weight Aerodynamic Control & Stab Manufacturab Total (Sample calculation: for monoplane, total value =30*8+30*7+20*7+20*9=770)

$the weight etimation part. To accomplih thi, we divided the miion profile into 20 different egment. For calculating maximum take-off weight, we conidered the fuel weight fraction for different egment.$

2 2.2 Selection of Tail Type Table 3: Selection of tail Invere T tail V tail H tail Weight Aerodynamic Control & Stab Manufacturab Total olve only the weight etimation part. To accomplih thi, we divided the miion profile into 20 different egment. For calculating maximum take-off weight, we conidered the fuel weight fraction for different egment. For ome of the egment, we got the value directly from hitorical data [1]. For other egment, where bomb drop i not included, we conidered Breguet Range equation to find fuel weight ratio for thoe egment [2]. For the ret of the egment including weight drop, we conidered breguet range equation a well a, weight drop related calculation to find the fuel weight ratio for thoe egment. 3.1 Maximum Take-off Weight Etimation 2.3 Selection of Landing Gear Type Table 4: Selection of landing gear Quad-cy cle Tri-c ycle Conv entio nal Weight Aerodynamic Control & Stab Manufacturab Total Selection of Power plant Poition Table 5: Selection of power plant poition Fuelage mounted Below wing Weight Aerodynamic Control & Stab Manufacturab Total Final Selection Table 6: Final election of different item Item Wing type Tail type Landing gear Power plant poition Selected Mono-plane H tail Tri-cycle Fuelage mounted 3. PRELIMINARY DESIGN Preliminary deign include weight etimation and calculation of wing loading and engine thrut. Here, we ll Fig.2: Detailed miion profile for attack fighter aircraft Aumption: H1= ft H2= 2000 ft H3= ft H4= 2000 ft H5= ft R1= 250 km = ft R2=100 km = ft r1= 10 km = ft R3= 90 km = ft R4=150 km = ft r2=10 km = ft R5=140 km = ft R6=100 km = ft r3=10 km = ft R7=90 km = ft R8=200 km = ft Weight of the crew = 200 lb Here, r1, r2, r3 i the ditance the aircraft paed while bomb dropping. Fuel weight fraction in thi mall range i aumed to have a value of 1. Aumption of payload: Table 7: Aumption of payload Payload type Weight (lb) Fixed 9000 Droppable in 1 t cae 2750 Droppable in 2 nd cae 500 Droppable in 3 rd cae 2750 Total Calculation of fuel-weight fraction for different egment and maximum take-off weight:

3 i. For thi egment, fuel weight fraction i directly obtained from hitorical data [1]. W 2/W 1 = 0.99 ii. For thi egment, fuel weight fraction i directly obtained from hitorical data [1]. W3/W2 = 0.98 iii. W4/W3= e.. (1) In thi cae, R = R1 = ft, SFC i found from hitorical data [3]. SFC = 1/3600 lb/lb/ Aume, L/D = 15 becaue, the highet mach i quite low and the value of L/D i larger for lower value of Mach number. Here, H = H1 = ft, = (1.4 x 287 x ) = m/ = ft/ temperature at ft, which i obtained from = ( x 0.62) ft/ = 600 ft/ W4/W3=e -[( x 1/3600)/ (0.866 x 15 x 600)] = 0.97 iv. For thi egment, fuel weight fraction i directly obtained from hitorical data [1]. W5/W4 = 0.99 [1] v. W6/W5 = e In thi cae, R= R2 = ft, SFC = 1/3600 lb/lb/ L/D = 15 (aume) = (1.4 x 287 x 283.2) = m/ = ft/ = ( x 0.62) ft/ =686 ft/ W6/W5 = e -[( x 1/3600)/ (0.866 x 15 x 686)] = vi. In bomb dropping phae, fuel-weight fraction i equal to 1 [4]. W7/W6 = 1 vii. W8/W7 = e In thi cae, R= R3 = ft, SFC = 1/3600 lb/lb/ = (1.4 x 287 x 283.2) = m/ = ft/ = ( x 0.62) ft/ = 686 ft/ -[( x 1/3600)/ (0.866 x 15 x 600)] W8/W7 = e = But, thi value hould be corrected due to bomb dropping [5]. Fuel weight fraction up to thi part =0.99 x 0.98 x 0.97 x 0.99 x 0,9898 x 1 = Therefore, jut prior to the bomb drop, weight = (15000 x.9222) lb = lb Immediately after bomb drop, weight = ( ) lb = lb The weight ratio of after & before bomb drop i = (11083/13833) = 0.85 the corrected value of W8/W7 = [1-( ) x 0.85] = viii. Fuel weight fraction for thi egment wa aumed by comparing with the fuel-weight fraction for climb [1]. W9/W8 = 0.98 ix. W10/W9 = e In thi cae, R= R4 = ft, SFC i found from hitorical data [3]. SFC = 1/3600 lb/lb/ Here, H = H3 = ft = (1.4 x 287 x ) = m/ = ft/ temperature at ft, which i obtained from tandard atmopheric temperature & preure chart. = ( x 0.62) ft/ = ft/

4 W10/W9 = e -[( x 1/3600)/ (0.866 x 15 x 600)] = x. In bomb dropping phae, fuel-weight fraction i equal to 1 [4]. W11/W10 = 1 xi. W12/W11 = e In thi cae, R= R5 = ft, SFC = 1/3600 lb/lb/ [3] Here, H = H3 = ft And, a= (γr T) 1/2 = (1.4 x 287 x ) = m/ = ft/ temperature at ft, which i obtained from = ( x 0.62) ft/ = ft/ W12/W11 = e -[( x 1/3600)/ (0.866 x 15 x 600)] = But, thi value hould be corrected due to bomb dropping [5]. Fuel weight fraction up to thi part = x.991 x.98 x.983 x 1 = Therefore, jut prior to the bomb drop, weight = [( ) x.896] lb = lb Here, = 12250, i the weight of total payload, after the 1 t bomb drop. Immediately after bomb drop, weight = ( ) lb = lb The weight ratio of after & before bomb drop i = (10476/10976) = the corrected value of W12/W11 = [1-( ) x 0.954] = xii. Fuel weight fraction for thi egment wa aumed by comparing with the fuel-weight fraction for decent [1]. W13/W12 = 0.99 xiii. W14/W13 = e In thi cae, R= R6 = ft, SFC = 1/3600 lb/lb/ a= (γr T) 1/2 = (1.4 x 287 x 283.2) = m/ = ft/ = ( x 0.62) ft/ =686 ft/ W14/W13 = e -[( x 1/3600)/ (0.866 x 15 x 686)] = xiv. In bomb dropping phae, fuel-weight fraction i equal to 1 [4]. W15/W14 = 1 xv. W16/W15 = e In thi cae, R= R7 = ft, SFC = 1/3600 lb/lb/ [3] Here, a= (γr T) 1/2 = (1.4 x 287 x 283.2) = m/ = ft/ = ( x 0.62) ft/ = 686 ft/ W16/W15 = e -[( x 1/3600)/ (0.866 x 15 x 600)] = But, thi value hould be corrected due to bomb dropping [5]. Fuel weight fraction up to thi part =0.896 x x 0.99 x x 1 = Therefore, jut prior to the bomb drop, weight = (( ) x.864) lb = lb Here, ( ) lb = lb i the weight of payload after the 1 t & 2 nd bomb drop. Immediately after bomb drop, weight = ( ) lb = 7402 lb The weight ratio of after & before bomb drop i = (7402/10152) = 0.73 the corrected value of W8/W7 = [1-( ) x 0.73] = xvi. Fuel weight fraction for thi egment wa aumed by comparing with the fuel-weight fraction for climb [1]. W17/W16 = 0.98 xvii. W18/W17 = e In thi cae, R = R8 = ft, SFC = 1/3600 lb/lb/ [3], L/D = 15 ; Here, H = H5 = ft, Here, a= (γr T) 1/2 = (1.4 x 287 x ) = m/ = ft/

5 temperature at ft, which i obtained from tandard atmopheric temp. & preure chart. = ( x 0.62) ft/ = 603 ft/ W18/W17=e -[(656168x 1/3600)/ (0.866 x 15 x 603)] = xviii. Fuel weight fraction for thi egment wa obtained from hitorical data [1]. W19/W18 = 0.99 xix. Fuel weight fraction for thi egment wa obtained from hitorical data [1]. W20/W19 = total fuel-weight fraction W20/W1 = [ (W 2/W 1) X (W3/W2) X (W4/W3) X (W5/W4) X (W6/W5) X (W7/W6) X (W8/W7) X (W9/W8) X (W10/W9) X (W11/W10) X (W12/W11) X (W13/W12) X (W14/W13) X (W15/W14) X (W16/W15) X (W17/W16) X (W18/W17) X (W19/W18) X (W20/W19)] = xx. Again, Maximum take-off weight can be etimated uing the following equation [6]: Wto=(Wcrew+Wpayload) / [1-(Wf/Wto)- (We/Wto) ] (2) Wf/Wto = 1.05[1-W20/W1] = From eqn (2), Wto = 15200/ ( We/Wto) Or, Wto = 15200/( We/Wto) Or, Wto-We=15200 We =0.7988Wto (3) xxi. Again, we ued another equation containing empty weight to total weight ratio [7]. We/Wto = AWto C K Here, for thi purpoe, A= 2.34, C= -0.13, K=1 auming fixed weep aircraft [7]. We/Wto = 2.34Wto Putting value from eqn (3), (0.7988Wto 15200)/Wto =2.34Wto Or, Wto = (2.34Wto X Wto) Or, Wto = 2.34Wto ( ) Or, Wto = 2.34Wto 0.87 Or, 2.34Wto Wto = 0 (4) We can find Wto by olving eq n (4). Thi eq n can be olved by putting different value of Wto ; and find a value of Wto, for which the L.H.S of eq n iii become zero. Table 8: Iteration to find Wto Wto = (lb) L.H.S of eq n iii value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) value of Wto lie in between & (according to bi-ection method) = R.H.S Wto = Maximum Take-off weight i lb. 4. CONCLUSION Conidering the given requirement the attack fighter aircraft will be a monoplane, H tail aircraft having a tri-cycle landing gear. The powerplant will be fuelage mounted. Maximum takeoff weight for the aircraft including bomb drop i lb. 5. REFERENCES [1] Dr. Jan Rokam, Airplane Deign Part I, Publihed by DARcorporation, Table: 2.1 [2] Dr. Jan Rokam, Airplane Deign Part I, Publihed by

6 DARcorporation, Chapter 2, Page 62 [3] Dr. Jan Rokam, Airplane Deign Part I, Publihed by DARcorporation, Table: 2.11 [4] Dr. Jan Rokam, Airplane Deign Part I, Publihed by DARcorporation, Chapter 2, Page 63 [5] Dr. Jan Rokam, Airplane Deign Part I, Publihed by DARcorporation, Chapter 2, Page 63, 64 [6] Daniel P. Raymer, Aircraft Deign: A Conceptual Approach, 4 th edition, Publihed by AIAA, Chapter 2, page 16 [7] Daniel P. Raymer, Aircraft Deign: A Conceptual Approach, 4 th edition, Publihed by AIAA,Chapter 2, page NOMENCLATURE Symbol Meaning Unit T Temperature (K) P R SFC L/D R γ Wto We Wf Preure Range Specific fuel conumption Lift to drag ratio Ga contant Specific heat ratio Maximum take-off weight Empty weight Fuel weight (Pa) (Feet) (lb/lb/) Dimenio nle (J/Kg K) Dimenio nle (lb) (lb) (lb)

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