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Old 06-25-2019, 12:43 PM   #1  
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Default Fuel Calculation

Hello,

Could someone direct me to an example of a fuel calculation, if unable to show determination on here:

This would be for a Cessna Super Cargomaster feeder for shorter haul- 90nm each way approx as well as 261 nm each way. One example would be great.

From what I've read, the payload is approximately 4000lbs. The max takeoff weight is approximately 42,000lbs. Fuel tank capacity is 335 gallons/economy is 2.57nm/gallon. I've seen different equations on the computer with winds etc., calculated. The weight of the Pilot(s) would be the standard 170pnds. I realize we also need some sort of fuel contingency.

Thank you.
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Old 06-25-2019, 01:25 PM   #2  
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Rachel,

Clearly you're not flying this aircraft or you'd have this information available. Are you writing an article?

Any time someone asks the a variation of the question about wanting to know about flying (but not landing), you may be able to see the implication. What's the purpose?

A fuel calculation is done using the fuel charts in the aircraft flight manual, and will take into account cruise altitude and weight. For most aircraft, temperature, as well. Fuel and time to climb to altitude is calculated separately, as is time, distance, and fuel burn to descend, and there is a fuel value used for taxi time.

When you ask about a Cessna Super Cargomaster, are you referring to the Cessna Grand Caravan? If so, your estimate of takeoff weight is off by a bit. You mentioned a takeoff weight of 42,000 lbs. The Cessna 208B "Super Cargomaster" has a gross weight of 8,750 lbs, and a relatively small engine. As a turboprop, fuel is calculated in either gallons per hour, or typically pounds of fuel burn per hour.

There isn't really a miles per gallon calculation, though there's something similar called "specific fuel consumption." It's typically not used for something like the Caravan. When calculating fuel burn, the groundspeed with forecast wind at the planned cruise altitude is calculated, then the fuel burn in pounds per hour calculated, then the enroute fuel burn based on pounds per hour over the duration of the cruise time. Obviously for a headwind, cruise time is greater, hence greater fuel burn.

Fuel burn, depending on power setting, will average 60-80 gallons per hour overall. Figure that at 6.7 lbs/gallon for turbine fuel, at 400-540 lbs/hour.

90 nautical mile trip, still air, figure 170 knot cruise speed, approx 35 minute trip. Fuel burn of 70 gph trip average for roughly 42 gallons, plus time to an alternate, using the same number, total of 84 gallons. Figure 45 minutes reserve after that at 55 gallons (rounded off slightly) for a trip minimum fuel of 140 gallons, or 940 lbs.

If you fill the tanks unnecessarily, you'll be carrying less cargo. Bear in mind that the Super Caravan is restricted to a lesser weight in icing conditions, and a higher fuel burn may be needed in the event of an icing encounter.
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Old 06-25-2019, 02:11 PM   #3  
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Quote:
Originally Posted by JohnBurke View Post
Rachel,

Clearly you're not flying this aircraft or you'd have this information available. Are you writing an article?

Any time someone asks the a variation of the question about wanting to know about flying (but not landing), you may be able to see the implication. What's the purpose?

A fuel calculation is done using the fuel charts in the aircraft flight manual, and will take into account cruise altitude and weight. For most aircraft, temperature, as well. Fuel and time to climb to altitude is calculated separately, as is time, distance, and fuel burn to descend, and there is a fuel value used for taxi time.

When you ask about a Cessna Super Cargomaster, are you referring to the Cessna Grand Caravan? If so, your estimate of takeoff weight is off by a bit. You mentioned a takeoff weight of 42,000 lbs. The Cessna 208B "Super Cargomaster" has a gross weight of 8,750 lbs, and a relatively small engine. As a turboprop, fuel is calculated in either gallons per hour, or typically pounds of fuel burn per hour.

There isn't really a miles per gallon calculation, though there's something similar called "specific fuel consumption." It's typically not used for something like the Caravan. When calculating fuel burn, the groundspeed with forecast wind at the planned cruise altitude is calculated, then the fuel burn in pounds per hour calculated, then the enroute fuel burn based on pounds per hour over the duration of the cruise time. Obviously for a headwind, cruise time is greater, hence greater fuel burn.

Fuel burn, depending on power setting, will average 60-80 gallons per hour overall. Figure that at 6.7 lbs/gallon for turbine fuel, at 400-540 lbs/hour.

90 nautical mile trip, still air, figure 170 knot cruise speed, approx 35 minute trip. Fuel burn of 70 gph trip average for roughly 42 gallons, plus time to an alternate, using the same number, total of 84 gallons. Figure 45 minutes reserve after that at 55 gallons (rounded off slightly) for a trip minimum fuel of 140 gallons, or 940 lbs.

If you fill the tanks unnecessarily, you'll be carrying less cargo. Bear in mind that the Super Caravan is restricted to a lesser weight in icing conditions, and a higher fuel burn may be needed in the event of an icing encounter.
Hello John,

Thanks for the response. I'm looking to eventually purchase for business usage, if manageable. Currently, I'm researching to determine the best-suited carrier for express cargo purpose. I'm putting together an itemized budget for the cost of the approximate operation of the aircraft, prior to expressing interest, and fuel consumption will be a part of that budget. I apologize if unclear, the cities which we will deliver will be 98nm X2 and 261nm X2.

Interesting, the plane is a Cessna 208B, and the numbers cited were taken directly from the listing. I've heard this is an excellent choice for feeder type operations. Is that correct?

Thank you for showing the determination. It gives me a bit of relief to understand how this is done. I currently have not hired a Pilot to help with this side of things so it's much appreciated.

Best wishes!
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Old 06-25-2019, 07:04 PM   #4  
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Quote:
Originally Posted by RachelM View Post
Interesting, the plane is a Cessna 208B, and the numbers cited were taken directly from the listing. I've heard this is an excellent choice for feeder type operations. Is that correct?
Depends upon the local terrain and especially the frequency of icing conditions. It has a somewhat sketchy history with icing, even with the TKS system.


Aviation Safety - Saving The Cessna Caravan


https://www.cav-systems.com/wordpres...na-Caravan.pdf
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Old 06-25-2019, 11:42 PM   #5  
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Rachel,

There's far too little information here. If you're talking feeder to FedEx, which utilizes the Caravan, there are a number of feeders already out there. Feeder aircraft run the gamut from the Caravan to Beech 99 and 1900's, Brazillias, etc, up through the ATR 42. There are various piston airplanes that include Piper Navajos, Twin Commanders, Cessna 402's, and so forth.

The Caravan is easy to fly and fairly straightforward. It's slow, and isn't a great weather airplane, and of course has one engine. It's not really an ice airplane.

Direct operating costs such as fuel and crew are only part of the equation. Maintenance is a big factor as is training and maintaining an operating certificate, to say nothing of obtaining one. Fuel may be the least of your costs. If a pilot experiences a hot start on the engine, you're going to be looking at close to half a million dollars, and components such as aircraft radios can get quite costly. Even a starter-generator can run up to 40,000 dollars.

I'm not sure what website gave you a 42,000 lb gross weight for a Cessna Caravan, but it's not even nine thousand pounds; that includes the weight of the airplane and fuel before getting to cargo. Airplanes that weigh greater than 12,500 lbs have additional requirements, including a type rating for the pilot, which adds to the expense. The Caravan is 2/3 that weight.
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Old 06-26-2019, 05:46 AM   #6  
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Quote:
Originally Posted by Excargodog View Post
Depends upon the local terrain and especially the frequency of icing conditions. It has a somewhat sketchy history with icing, even with the TKS system.


Aviation Safety - Saving The Cessna Caravan


https://www.cav-systems.com/wordpres...na-Caravan.pdf
Thanks for the information. It's certainly helpful. We do have the distinct seasons of four weather and a rainy/snowy winter so I'll have to rethink this option. Any suggestions?
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Old 06-26-2019, 06:03 AM   #7  
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Quote:
Originally Posted by JohnBurke View Post
Rachel,

There's far too little information here. If you're talking feeder to FedEx, which utilizes the Caravan, there are a number of feeders already out there. Feeder aircraft run the gamut from the Caravan to Beech 99 and 1900's, Brazillias, etc, up through the ATR 42. There are various piston airplanes that include Piper Navajos, Twin Commanders, Cessna 402's, and so forth.

The Caravan is easy to fly and fairly straightforward. It's slow, and isn't a great weather airplane, and of course has one engine. It's not really an ice airplane.

Direct operating costs such as fuel and crew are only part of the equation. Maintenance is a big factor as is training and maintaining an operating certificate, to say nothing of obtaining one. Fuel may be the least of your costs. If a pilot experiences a hot start on the engine, you're going to be looking at close to half a million dollars, and components such as aircraft radios can get quite costly. Even a starter-generator can run up to 40,000 dollars.

I'm not sure what website gave you a 42,000 lb gross weight for a Cessna Caravan, but it's not even nine thousand pounds; that includes the weight of the airplane and fuel before getting to cargo. Airplanes that weigh greater than 12,500 lbs have additional requirements, including a type rating for the pilot, which adds to the expense. The Caravan is 2/3 that weight.
Thanks for the information, John. There are a lot of factors to take into account. I'm trying to learn about air freight/rail and that is why I have put my questions online.

The airplane would be an additional method of transport. I'm trying to determine whether or not it would be a successful addition. I have no affiliations with FedEx. Perhaps I've misread the website for the weight. I'll double check. After reading the articles above, it may not be the best choice for my location. Again, I appreciate all of your suggestions.
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Old 06-26-2019, 09:13 AM   #8  
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The aircraft you want depends on what you’re hauling.

Sometimes you aren’t hauling anything heavy and only need an airplane to get it there quick. Medical transport companies make good use of the Pilatus PC12 for this. Important documents are also shipped via PC12. It can handle the northeast weather.

If you’re transporting bulk packages, the ATR, or the Shorts 360 are commonly used to fill the routes that the C208 Grand Caravan is not capable of keeping up with
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Old 06-27-2019, 05:58 AM   #9  
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Thanks for the suggestions Dontlookdown! I'll look into these online.
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