Mass Volume Conversion | CRP 5 Flight Computer | Navigation Computer #4
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This video explains “How to use CRP 5 for
Conversion between Mass and Volume”, and we are starting right now! Hello and welcome to Answering ATPL, the focus
of this channel is to provide solutions for EASA ATPL questions and other aviation related
stuff. Let me know in the comments section below
if you are currently taking ATPL theoretical examination. This video is the fourth video of a series
of videos explaining the usage of CRP 5 computer face. If this is your first time here, consider subscribing to my channel, and click on the bell icon to get notified when I published a new video. Amount of fuel required for a flight is calculated
in the unit of mass either Kilograms or Pounds. Having determined the amount of fuel required
for the flight. It is necessary to convert the mass to volume
because the fuel operator dispenses the required amount of fuel in volume, using US gallons,
Imperial gallons or liters. Mass is defined as: “The quantity of matter
which a body contains.” Volume is defined as: “The amount of space
that a substance or object occupies.” On the screen is a diagram showing the relationship
between Mass, Volume and Temperature. As a conclusion, we can say that: When temperature
changes, mass remain constant, and Volume is changing with temperature. This poses challenges for conversion; we can’t
convert Mass to Volume or Volume to Mass using a fixed ratio. To convert from mass to volume and vice versa
we need, “Specific Gravity!”. Specific Gravity, or SG is defined as, “A
comparison of the heaviness of one substance, to that of water”. The formula for Specific Gravity
SG=Density of Object divided by Density of water
For example: 1 imperial gallon of AVGAS has a mass of 7.2
lbs, and 1 imperial gallon of water has a mass of 10 lbs. Thus, the Specific Gravity of the AVGAS=7.2/10
=0.72 Now let take a look how to make the conversion. In order to help you with the conversion. You’ll see on screen, a handy chart illustrating
all the step needed to change the volume to mass, and mass to volume. On the left-hand column, Volume are listed
in US Gallons, Imperial Gallons, and Liters. And, in the right-hand column mass is listed
in pounds and kilograms. The necessary conversion factors are listed
along the appropriate lines. To carry out a conversion using the arrow,
multiply the box at the tail of the arrow, by the conversion factor, and when moving
against the arrow divide the box at the arrowhead, by the conversion factor. The following example will guide you through
conversion. We will work through 2 examples on screen,
first using the chart, and later using CRP5 Example 1: Convert 1000 US gallons of Jet
A1 with specific gravity 0.83, into kilograms. To solve example 1, start by dividing 1000
US gallons by 1.2, this becomes imperial gallons. Now multiply by 4.546 to bring it to liters. And Finally, multiply by the SG 0.83 to reach
a solution 3144 kilograms. Example 2 demonstrate going in the reverse
direction converting kilograms to US gallons. Convert 1000 kg to US gallons with SG 0.83. First, multiply 1000 kg with 2.205 to bring
it to pounds. Now divide by 10 and 0.83 respectively to
obtain imperial gallons. And finally, multiply by 1.2 to reach the
solution of 319 US gallons. Now let look on how to do the conversion using
CRP 5. There are two scales on the periphery of the
instrument which enable us to convert volume into mass, and vice versa. There are label Sp. G which stand for specific gravity. The first scale is used to convert pounds
of fuel at various specific gravity to imperial gallons, US gallons, and liters, and vice
versa. This scale can be identified by red letters
lbs adjacent to it. The other scale is used to convert kilograms
of fuel at various specific gravity to imperial gallons, US gallons, and liters, and vice
versa. This scale can be identified by red letters
KGS adjacent to it. Now let re-work our previous example to understand
how this function work. Example 1. Convert 1000 US gallons of Jet A1 with Specific
Gravity of 0.83 into kilograms. As any other operation using CRP 5 the first
step is to approximate the answer. From the previous video, we know that US gallons
and imperial gallons have roughly similar magnitude. Thus, we can assume that 1000 US gal is approximately
equal to 1000 imperial gallons. Round up specific gravity to 0.8
1000 imperial gallons times 10 times 0.8 is equal to 8000 lbs. Since 1 kg is approximately equal to 2 lbs;
8000 lbs are approximately equal to 4000 kg. Now that we have the approximation, we can
now use CRP 5 to get the answer. Locate US. Gal marker. Align the cursor with US. Gal Marker. Align the 10 index on the inner scale with
the cursor to represent 1000 US gallons. Align cursor to 0.83 on Sp.G marker near KGS
marker. Read the answer on Inner scale, 31.4
Our approximate value is in the region of thousand. Our final answer should be: 1000 US gallons
at Specific Gravity of 0.83=3,140 kilograms. Let use the same example to find the mass
in pounds. Ensuring the scale are in their relative position,
move the cursor to align it with 0.83 on lbs Sp.G scale. Read the answer on the inner scale, 69.2
Our approximate value tells us the final answer is: 1000 US Gallons at 0.83 Specific gravity
equal to 6,920 lbs. Now let look at Example 2. Convert 1000 kg to US gallons at Specific
Gravity 0.83 First Step – Approximation. 1 kg is roughly 2 lbs. Thus, 1000 kg is roughly 2000 lbs. Round up specific gravity at 0.8; This means
1 imperial gallon equals 8 lbs. We take it as 10 lbs.
2000 lbs divided by 10 equals 200 Imperial gallons. Since imperial gallons and US gallons have
roughly the same magnitude, we can say that 200 imperial gallons are approximately 200
US gallons. Now that we have the approximate, we can proceed
to step 2: using CRP 5 to get the answer. First, locate KGS marker. Align cursor to Specific Gravity 0.83 near
KGS marker. Align the 10 index on the inner scale to the
cursor to represent 1000 kilograms. Align Cursor with US. Gal marker. Read the answer on the inner scale, 31.9
Thus, our final answer will be 1000 kg at specific gravity 0.83 is equal to 319 US gallons. By using the same procedure, we can also find
the value for imperial gallons. Just align the cursor to Imp. Gal marker. And, read the answer from the inner scale. 26.58
From our approximation, we know the correct value is 265.8 imperial gallons. In the next video in these videos series,
we will discuss on Time, Speed and Distance. If you want to learn more about ATPL or aviation,
start now by hitting the round subscribe icons! Also, if you have any questions or comments
about ATPL or aviation related problems, you can leave them in the comment section. Thank you so much for watching, I’ll see you
next time!

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