Fuel consumption / Mission preplanning

[DirtyFret]

I have being trying to improve my skills in mission planning namely fuel cpnsumption calculations and estimation to optimize the weight that I can ferry. The draft manual provides good tables and numbers and I think I got the basics of it.

 

Regarding this I have a few questions:

 

- Does the warm up or run-up fuel consumption vary with airfield elevation?

 

- Does the KO-50 heater use the same fuel and if so does it has to be estimated into mission planning?

 

- In cruise calculations which is better/more accurate: kgf/km or kgf/h?

 

I am slightly confused with the manuals instructions at the end about how to get the total amount.

 

 

"To calculate the required fuel for a given mission range, calculate the fuel re-

quired for non-navigation phases of the mission (start, taxi, target attack

run(s)), add the minimum fuel quantity, then subtract this sum from the total

fuel quantity on board. Multiply the remainder by 0.95 to add 5% navigational

error factor and another 0.95 to add 5% for formation keeping."

p.122

 

If I calculate the total amount required based on the consumption tables why do I have to subtract that amount from total amount. I probably don't understand this correctly and I would be gratefull of any clarification on this

[DirtyFret]

- In cruise calculations which is better/more accurate: kgf/km or kgf/h?

 

Found the answer to this one. I must improve my search skills if I want to do search and rescue in Mi-8 :music_whistling:

 

http://forums.eagle.ru/showpost.php?p=2609227&postcount=2

 

The answers to the remaining questions still elude me.

[Cibit]

KO 50 heater is kerosene so presumably has its own tank. Helicopters would probably be cheaper to operate if kerosene was the fuel:)

[Necroscope]

KO-50 heater use about 2.8kg\h if I remember correctly, so this can be neglected.

 

KO 50 heater is kerosene so presumably has its own tank. Helicopters would probably be cheaper to operate if kerosene was the fuel:)

 

But kerosine is the fuel for Mi-8...

[Darkwolf]

As a dirty calculation, i take 3 liter/km. Charts are below it, but that makes me a good reserve in case i get fuel leak in flight.

 

To calculate the required fuel for a given mission range, calculate the fuel re-

quired for non-navigation phases of the mission (start, taxi, target attack

run(s)), add the minimum fuel quantity, then subtract this sum from the total

fuel quantity on board. Multiply the remainder by 0.95 to add 5% navigational

error factor and another 0.95 to add 5% for formation keeping."

it's

 

Non navigation :

 

Takeoff fuel + mission fuel (Think about how long you gonna stay around your target/deliverypoint)

 

Navigation :

 

You regular flight fuel

 

 

Total 1 = nav + non-nav fuel.

 

 

 

Add everything together and add 5% for navigation mistake.

And on top of this - another 5% if you do formation flight. (guys following someone tend to consume more as they do more power adjustement to fly formation)

You may want to add some more fuel for reserve in case of wind/damage.

 

I'm suspecting a mistake in the text, you may want to divide by .95 to do a 5% addition.

 

Edited December 30, 2015 by Darkwolf

[Cibit]

KO-50 heater use about 2.8kg\h if I remember correctly, so this can be neglected.

 

 

 

But kerosine is the fuel for Mi-8...

 

In the UK we speak of kerosene as paraffin like you use in oil lamps and space heaters in garages. I understood helicopter engines used Jet A or refined unleaded petrol

[xxJohnxx]

KO 50 heater is kerosene so presumably has its own tank. Helicopters would probably be cheaper to operate if kerosene was the fuel:)

 

The Ko-50 runs on normal fuel, so yes, you have to consider it in. Though it probably doesn't need very much fuel.

[Flagrum]

I'm suspecting a mistake in the text, you may want to divide by .95 to do a 5% addition.

No, it states that the remainder is to be multiplied by .95 - so you get 95% of the available fuel aka add 5% to the reserve. :smartass:

 

In the UK we speak of kerosene as paraffin like you use in oil lamps and space heaters in garages. I understood helicopter engines used Jet A or refined unleaded petrol

"Kerosene, also known as lamp oil, is a combustible hydrocarbon liquid widely used as a fuel in industry and households. (...)

Kerosene is widely used to power jet engines of aircraft (jet fuel) and some rocket engines, and is also commonly used as a cooking and lighting fuel and for fire toys such as poi."

So I guess, it's basically all the same. :smartass:

[Necroscope]

Yep. And (quote): Jet A and Jet A-1 are kerosene-type fuels. Military JP are also kerosine-based: https://en.wikipedia.org/wiki/Jet_fuel#Military_jet_fuels

So basically you burning jet fuel in own oil lamp. )))

[Cibit]

Thanks for pointing out my mistake without taking the P*$$ your never to old to learn;)

[gospadin]

I wonder if Belsimtek modeled fuel density variation by temperature when filling tanks...

 

http://www.pprune.org/tech-log/348739-temperature-vs-fuel-density.html

[Art-J]

I wonder if Belsimtek modeled fuel density variation by temperature when filling tanks...

 

http://www.pprune.org/tech-log/348739-temperature-vs-fuel-density.html

 

Hop in the F-86 and test it then. I remember the plane has the fuel quantity gauge with density correction on/off function. I admit I never tested it on winter vs. summer map though.

[DirtyFret]

Good discussion and good pointers.

 

I must admit though that I am still confused with the manuals final statement"...this sum from the total fuel quantity on board. Multiply the remainder by 0.95 to add 5% navigational

error factor and another 0.95 to add 5% for formation keeping.""

 

If I calculate a estimated fuel consumption A what is this "total fuel quantity on board" (B) that I am subtracting the estimated fuel consumption amount from? Is B the total fuel capacity? Doesn't this vary with fuel pods etc.?:helpsmilie:

 

And still I would find it more straightforward to just do Ax1.05x1.05 to find the amount of fuel to be filled into the tanks?

 

I don't get the logic behind the (A-B)x0.95x0.95. What amount of fuel would I tell my (virtual) crew chief to load up?:noexpression:

[gospadin]

I agree with your math. I'd add 10% to the amount to ask for to cover those possible error sources as well.

[flo57100]

I admit I'm confused as well by substracting the found result from the total fuel quantity on board. What does it mean ? If we calculate the needed fuel for a given range, we assume the tanks are empty and we want to know how much fuel to be poured in those tanks, no ? And for the "multiply the found result by 0,95 then again by 0,95", I would say divide the result by 0,95 , otherwise you Will have even less fuel than calculated before...

[msalama]

Fuel x .95 x .95 gives you the amount of fuel at your _disposal_ for the trip since it accounts for formation flying and nav errors, no?

[Flagrum]

Good discussion and good pointers.

 

I must admit though that I am still confused with the manuals final statement"...this sum from the total fuel quantity on board. Multiply the remainder by 0.95 to add 5% navigational

error factor and another 0.95 to add 5% for formation keeping.""

 

If I calculate a estimated fuel consumption A what is this "total fuel quantity on board" (B) that I am subtracting the estimated fuel consumption amount from? Is B the total fuel capacity? Doesn't this vary with fuel pods etc.?:helpsmilie:

 

And still I would find it more straightforward to just do Ax1.05x1.05 to find the amount of fuel to be filled into the tanks?

 

I don't get the logic behind the (A-B)x0.95x0.95. What amount of fuel would I tell my (virtual) crew chief to load up?:noexpression:

You have the maximum amount of fuel, including additional tanks and whatnot. From that you calculate how much you have at your disposal (assumption: 95%) for actual flying your planned route. Now you have your available fuel and can calculate how far it can take you.

 

But yeah, probably starting from the other end makes more sense: you start with a given flight distance, calculate the needed fuel for that distance and then add some reserve to it. The result would be the amount of fuel to be filled into the tanks.

[DirtyFret]

Thanks guys. Thanks to your explanations and a couple days I finally understand this. :thumbup:

 

To calculate mission range one calculates the non-nav fuel + emergency fuel and subtracts this from total amount of fuel onboard. This remainder is then multiplied by 0.95x0.95 to give the amount of fuel for Nav phase. From this and the tables provided one can calculate how long (hrs or km) they can fly.

 

Alternatively if you know the total mission range (km) one can calculate the fuel consumption and multiply that with 1.05x1.05 and the add the non-nav + emergency fuel to get the final amount (what I have been doing)

[spaceraver]

I might be dumb here, but why not calculate the amount of fuel needed for the distance and add 10%, that's a bit more than you need to be on the safe side.