1. Congratulations…Welcome to UTHM PARIT RAJA….A Place To Be..
DR. ZAMRI BIN OMAR Department of Aeronautical Engineering Faculty of Mechanical & Manufacturing Eng. Phone : /7711 Room: C & A4, 2nd Floor

2. ~(5) A Better Weight Estimation
In step 1, weight is estimated based on historical data.
Now we have the aircraft layout: size & shape are known.
weight is so important  special task for ‘Weight Engineers’
We’ll do crude weight buildup BUT more detail than in Step 2
So the layout will let us re-calculate the weight buildup.
Guidelines from Raymer for GA aircraft,
Units !
Area : ft2
weight : lb

3. ~(5) A Better Weight Estimation
Consider wing weight,
Exposed planform area: area seen in Fig (projected area not included)
Sw=176 ft2: projected area included.
From fig. 8.19, for one wing, the area is 176/2 = 88 ft2.

4. ~(5) A Better Weight Estimation

5. ~(5) A Better Weight Estimation
Based on previous 3 figures,
Calculation for wing;

6. ~(5) A Better Weight Estimation
Estimate of wetted area of FL.
What is wetted area ??
FL is composed of 3 parts as shown
Total wetted area;

7. ~(5) A Better Weight Estimation : Fuselage wetted area.
Elliptical area = pi x ( a/2) x (b/2)
Conical area = pi x r x sqrt(r2+h2)

8. ~(5) A Better Weight Estimation :
Now solve the following equations, got to deal with iterations !
= 2.5 x 148 ft2 = 370 lb
= 2.0 x 35.3 ft2 = 70.6 lb
= 2.0 x 14.4 ft2 = 28.8 lb
= 1.4 x ft2 = lb
= x 5,158 lb = 294 lb
= 1.4 x 547 lb = lb
= 0.1 x 5,158 lb = lb
*TOTAL EMPTY WEIGHT = 2,474 lb
*In 1st estimation, We/W=0.62,
 We = 3,198 lb
(WW)
(WHT)
(WVT)
(WF)
(WLG)
(WIE)
(WEE)

9. ~(5) A Better Weight Estimation :
TOTAL EMPTY WEIGHT = 2,474 lb
Gross Take-off Weight 
With this Wo, we recalculate WLG & WEE (eqn. 8.83e & 8.83g), and recalculate We,
Landing gear weight = x 4,434 lb = lb
All else empty = 0.1 x 4,434 lb = lb
With new WLG & WEE , give us new We & Wf ;
 We = 2,360 lb, Wf = x 4,434 lb = 705 lb
Yet, another value of Wo is obtained,
 Wo = ,360 = 4,205 lb
Repeat this process (recalculate We, Wf & Wo), until we obtain convergence.

10. ~(5) A Better Weight Estimation :
Summary of iteration process;
Now compare these weight buildups with their old values in step 1
 We = 3,198 lb, Wf = 820 lb, Wo = 5,158 lb
Better airplane’s weight is estimated !
Step 5 just completed.