design lab present a ion
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A Amith Reddy (AE09B032) Ch Deepak (AE09b034) S Hari Prasad (AE09B036) Jackson Joseph (AE09b037) Yogesh Jethani (AE09B038)
GROUP 6 :
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MISSION AND FIRST WEIGHT ESTIMATE
MISSION Design a strategic bomber conceptually.
PRIMARY DESIGN CRITERIA Important parameters :
Range (8000 Kms – 10000 Kms) Service ceiling (8000 m) Maximum speed (1000 kms)
FIRST WEIGHT ESTIMATE Approach : First weight estimate based on historical data
𝑊𝑜 = 𝑊𝑐𝑟𝑒𝑤 + 𝑊𝑝𝑎𝑦𝑙𝑜𝑎𝑑
+ 𝑊𝑓𝑢𝑒𝑙 + 𝑊𝑒𝑚𝑝𝑡𝑦
𝑊𝑜 = 𝑊𝑐𝑟𝑒𝑤 + 𝑊𝑝𝑎𝑦𝑙𝑜𝑎𝑑 + (𝑊𝑓/𝑊𝑜)𝑊𝑜 + (𝑊𝑒/𝑊𝑜)𝑊𝑜
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Graphs plotted from historical data
a) 𝑊𝑓/𝑊𝑜 𝑣𝑠 𝑊𝑜 b) 𝑊𝑒/𝑊𝑜
𝑣𝑠 𝑊𝑜 c) 𝑅𝑎𝑛𝑔𝑒 𝑣𝑠 𝑊𝑜 d) 𝑆𝑒𝑟𝑣𝑖𝑐𝑒 𝑐𝑒𝑖𝑙𝑖𝑛𝑔 𝑣𝑠 𝑊𝑜 e) 𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑆𝑝𝑒𝑒𝑑 𝑣𝑠 𝑊0
Analytical optimization process gives 𝑊0. Using above 𝑊0 and graphs ‘a’ and ‘b’ we can get 𝑊𝑓 and 𝑊𝑒 . Calculated values :
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MISSION PROFILE AND SECOND WEIGHT ESTIMATE
MISSION PROFILE
(30 mins)
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Weight loss due to bomb dropping is excluded, because bombs should be carried back if not used.
EMPTY WEIGHT FRACTION • Empty weight fraction can be estimated Using curve fit
equation given below
• 𝑾𝒆
𝑾𝟎= 𝑨𝑾𝟎
𝒄 𝑲𝒗𝒔 --------------(1)
• Kvs is variable sweep constant which in this case is 1 as we didn’t opt for any variable sweep.
• For a bomber aircraft ,A and C values are 0.93 and - 0.07 respectively.
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FUEL FRACTION ESTIMATION
ENGINE SPECIFICATIONS : Since the aircraft is subsonic high bypass turbofan is selected for its high efficiency in this velocity range.
Specific fuel consumption : Cruise:0.5 Loiter:0.4
TAKEOFF, CLIMB AND LANDING : Weight fractions of Takeoff, climb and landing are independent of the type of aircraft Historical mission segment weight fractions:
Warm up and takeoff 0.970
Climb 0.985
Landing 0.995
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CRUISE : The cruise mission segment can be found out from the range equation which is
𝑊𝑖
𝑊𝑖−1= exp −
𝑅𝐶
𝑉(𝐿
𝐷)
LOITER : The loitering weight ratios are found out using the
endurance equation
𝑊𝑖
𝑊𝑖−1= exp −
𝐸𝐶
(𝐿
𝐷)
From historical data wetted aspect ratio is 1.2, with wetted aspect ratio (L/D)max=15.4 and (L/D) = 0.866*(L/D)max . CRUISE SPEED : Cruise speed is found using historical data Plotted graphs from historical data
a. cruise speed vs. range b. cruise speed vs. service ceiling c. cruise speed vs. total take-off weight
with optimization similar to the previous one, cruise speed is found to be about 600 kmph.
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SECOND WEIGHT ESTIMATE
Using calculated values for (L/D)max and C, we get 𝑊3
𝑊2 and
𝑊4
𝑊3 .
Taking the aircraft weight at the end as W6, we have
𝑊6
𝑊0=
𝑊6
𝑊4
𝑊4
𝑊3
𝑊3
𝑊2
𝑊2
𝑊1
𝑊1
𝑊0 and
𝑊𝑓
𝑊0= 1.06 ∗ 1 −
𝑊6
𝑊0 .
Now iteration is performed using the relation 𝑊0 =𝑊𝑐𝑟𝑒𝑤+𝑊𝑝𝑎𝑦𝑙𝑜𝑎𝑑
1− 𝑊𝑓
𝑊0 −
𝑊𝑒𝑊0
and equation 𝑊𝑒/𝑊0 = 0.93𝑊0
− 0.07 From the iterative processes
𝑾𝒆𝒎𝒑𝒕𝒚 37200
𝑾𝒐(second estimate) 88880
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