A Amith Reddy (AE09B032) Ch Deepak (AE09b034) S Hari Prasad (AE09B036) Jackson Joseph (AE09b037) Yogesh Jethani (AE09B038)

GROUP 6 :

Home

Previous

Next

Help

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

Home

Previous

Next

Help

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 :

Home

Previous

Next

Help

MISSION PROFILE AND SECOND WEIGHT ESTIMATE

MISSION PROFILE

(30 mins)

Home

Previous

Next

Help

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.

Home

Previous

Next

Help

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

Home

Previous

Next

Help

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.

Home

Previous

Next

Help

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