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WORKING OUT FUEL AT STARTUP AND FLIGHT FUEL

  • boeing777mark
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boeing777mark created the topic: WORKING OUT FUEL AT STARTUP AND FLIGHT FUEL

Hello guys,I am working on bob taits book VFR DAY page 3.1.21 trying to work out fuel required at startup and flight fuel..

The first answer ask you to work out how many gallons and litres you would need for startup, using my cr3 computer i am unable to get the correct answer

Please can someone tell me how to work it out as my brain has done that much studying today it can no longer function, i am aware that it is a very simple calculation using the cr3 computer but i still can't get it

I am working on Exercise 6 if anyone can help me

Kind Regards
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Richard replied the topic: Re: WORKING OUT FUEL AT STARTUP AND FLIGHT FUEL

Hi Mark,

Let's work the first one and I'll leave you to do the rest (or post again if you get stuck)

From Exercise N6 on p 3.1.21:

14gph for 88 min and we want the fuel required at start-up in gallons and litres plus we want flight fuel in gallons and litres. The operator specifies a fixed reserve of 10 gallons, taxi/startup allowance of 2 gallons and no variable reserve.

First off, let's find how much fuel we need for the 88 minutes of flight (the flight fuel). You can use a calculator for this step but we'll do it with the CR3 for now. On the CR3, line up the burn rate of 14 gph on the outer scale against the "1:00" or 1 hour marker of the inner scale. The CR3 is now set up to read fuel over time with fuel amounts on the outside scale and time on the inside scale calibrated for a fuel burn rate of 14 units per hour (gallons in this case).

We want the time of 88 minutes so find "88" on the inner scale and read off the fuel burn from the outside scale. You'll see it comes to 20.5 gallons.

To calculate the other values we use a calculator. I'll create a simulated fuel plan with columns for gallons and litres so you can better see how the values all fit together. I have used the supplied constants of 1 gallon = 3.78 litres.
FUEL ....................GALLONS LITRES
Flight Fuel:88 min @ 14 gph20.5 gallons20.5 x 3.78 = 77.49 round up to 78 litres
Variable Reserve:....................NoneNone
Fixed Reserve:....................10 gallons10 x 3.78 = 37.8 litres
Taxi/Startup....................2 gallons2 x 3.78 = approx 7.5 litres
FUEL AT STARTUP....................20.5 + 10 + 2 = 32.5 gallons78 + 37.8 + 7.5 = 123.3 litres round to 123 litres

Fuel at start-up is the flight fuel plus all reserves and allowances together so we simply add the flight fuel plus the fixed reserve plus the allowances to get the final total.

Have a go at the others in N6 now and let me know if you get stuck or have any more problems.

Cheers,

Rich
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  • boeing777mark
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boeing777mark replied the topic: Re: WORKING OUT FUEL AT STARTUP AND FLIGHT FUEL

Hi Richard

Thankyou so much for your reply, i will have a go at it tonite and i will let you know how i go,it looks pretty straight forward now

Appreciate your help mate

Cheers
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boeing777mark replied the topic: Re: WORKING OUT FUEL AT STARTUP AND FLIGHT FUEL

Hi Richard

Just thought i would let you know that i have done a bit of work on exercise 6 and it all make sense so i thankyou for your assistance in helping me

Just wondering if you could do an example of exercise 7 for me on the same page, working out the fixed reserve fuel of 45 minutes

Appreciate it richard

Kind regards
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Richard replied the topic: Re: WORKING OUT FUEL AT STARTUP AND FLIGHT FUEL

Hi Mark,

You do N7 in exactly the same way as N6. The only difference is you need to first work out the fixed reserve required. In N6 there was a set fixed reserve of 10 gallons. In normal operations the amount needed as fixed reserve is usually calculated using the fuel flow at a particular power setting for the aircraft. In exercise N7 this fuel flow is given and it's based on the cruise fuel flow. In real life (and in other questions) you may find the fixed reserve is actually based on a lower power setting such as would be used if the aircraft was in a holding pattern. Don't worry about that too much yet though.

Anyway, for N7, the fixed reserve is 45 minutes at the fuel flow expected with the aircraft in cruise and the values for the cruise fuel flow for each problem are given in the first column.

Here's an example of calculating a fixed reserve:

How much fuel is required for 45 minutes fixed reserve at a cruise rate of 52 litres per hour?
Use your CR3 to line up 52 litres on the outside scale against 1:00 on the inner scale. Find 45 minutes on the inner scale and read off the fuel quantity of 39 litres on the outer scale. Using our gallons-litres conversion constant of 3.78 we can work out that 39 litres is also (39 / 3.78) = 10.3 gallons

In exercise N7, for each line of the table you will need to calculate the fixed reserve at the specified fuel flow and then work the rest of the values in that row using the same process as in exercise N6.

Cheers,

Rich
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boeing777mark replied the topic: Re: WORKING OUT FUEL AT STARTUP AND FLIGHT FUEL

Hi Richard

To easy mate, thankyou so much for your help

Kind regards

Mark
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