Embed Size (px)
DESCRIPTION
Weights & Balances. Moment:. www.GeoffHatcher.com. Moment:. Torque. Torque and moment are expressed in in-lbs or ft-lbs. The measure of the distribution of mass or force relative to a given axis. (datum plane). Force x leverage(moment arm) = torque. Weight x Moment Arm = Moment. - PowerPoint PPT Presentation
Citation preview
Moment:Torque and moment are expressed
in in-lbs or ft-lbsForce x leverage(moment arm) = torqueWeight x Moment Arm = Moment
The measure of the distribution of mass or force relative to a given axis. (datum plane)
Torque
www.GeoffHatcher.com
0
Datumline
Moment: The measure of the distribution of mass
relative to a datum line. Mass x arm= moment
1pound1foot 2 feet
One pound placed I foot from the datum…..If it is moved a foot further from the datum line…..It’s moment would increase to 2 foot pounds (2 ft·lbs)has a moment of one foot pound (1 ft·lb )
www.GeoffHatcher.com
20 20
Left side 20 X -4 = -80Right side 20 x 4 = 80Balance Bar 10 X 0 = 0
We use the formulaMass x arm = moment
Total 50 0 ÷ 50 =0
Total Moment ÷ Total weight = center of gravity
Bar=10 lbs
1 2 3 4 5 6-1-2-3-4-5-6 0
Bar=10 lbs 20Bar=10 lbs
Finding a 3000 pound aircrafts balance point requires mathmatics because you can’t very well pick it up and balance the thing on your fingers.
Mass x arm = moment
www.GeoffHatcher.com
Left side 20 X -4 = -80Right side 20 x 6 = 120Balance Bar 10 X 0 = 0
Mass x arm = moment
Total 50 40 ÷ 50 = .8
Moment÷ weight= arm center
20
1 2 3 4 5 6-1-2-3-4-5-6 0
20 20Bar=10 lbsBar=10 lbs
www.GeoffHatcher.com
•It’s important to notice that the placement of the datum line can be anywhere you want as long it is consistent throughout
the calculations.
•The Datum line is never the actual C.G. because it is constantly shifting.
Bar=10 lbs2020
7 8 9 10 11 121 2 3 4 5 6-1-2-3-4-5-6 0Datum
Left side 20 X 2 = 40Right side 20 x 10 = 200Balance Bar 10 X 6 = 60
Mass x arm = moment
Total 50 300 ÷ 50 = 6
Total Moment ÷ total weight = total moment armCenter of gravity
www.GeoffHatcher.com
The Datum on an Aircraft is usually placed at the fire wall, the nose, or the base of the nose cone to avoid the complex arithmetic associated with negative numbers.
Datumline
42 1280 52 76 101
5132C.G. Limits
Negative numbers can cause spatial disorientation, in many pilots.
StationsForward seats 42Fuel Tanks 52middle seats 76rear seats 101rear baggage 128
Each Area of the plane is assigned a “station” according to how many inches away it is from the datum
The aircraft is drained of fuel and oil and its empty weight and C.G is determined.
2,179 lbs at 41” moment 89,609 in·lbs
www.GeoffHatcher.com
Datumline
42 1280 52 76 101
5132C.G. Limits
400 lbs
516 lbs of fuel
200 lbs 100lbs400 lbs
Forward seats 400 lbs X 42 = 16,800
Middle seats 400 lbs X 76 = 30,400
Rear seats 200 lbs X 101 = 20,200
Mass X arm = moment
Total 3,795lbs 196,641 ÷ 3795 = 51.82”
Total Moment ÷ total weight = total moment arm
Center of gravityBaggage 100 lbs X 128 = 12,800
Fuel 516 lbs X 52 = 26,832
Aircraft 2,179 lbs X 41 = 89,609
www.GeoffHatcher.com
Datumline
42 1280 52 76 101
5132C.G. Limits
400 lbs
516 lbs of fuel
200 lbs 100lbs400 lbs
Forward seats 400 lbs X 42 = 16,800
Middle seats 400 lbs X 76 = 30,400
Rear seats 200 lbs X 101 = 20,200
Mass X arm = moment
Total 3,795lbs 196,641 ÷ 3795 = 51.82”
Total Moment ÷ total weight = total moment arm
Center of gravityBaggage 100 lbs X 128 = 12,800
Fuel 516 lbs X 52 = 26,832
Aircraft 2,179 lbs X 41 = 89,609
Weight shift Problem
www.GeoffHatcher.com
Datumline
42 1280 52 76 101
5132C.G. Limits
400 lbs
516 lbs of fuel
200 lbs 100lbs400 lbs
Mass X arm = moment
196,641
Total Moment ÷ total weight = total moment arm
Weight shift ProblemLets drop off one of the two middle passengers (200 lbs) and move a rear passenger (150 lbs) to the middle.
3,795 lbs
-200 lbs X 75 = -15,000
-150 lbs X 101 = -15,150
150 lbs X 75 = 11,250
Passenger gets out of middlePassenger gets out of backAnd moves to the middle
Total weight 3595 lbs 177741 ÷ 3595 = 49.4
www.GeoffHatcher.com
