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A 717 (95% load factor) burns only 631 gallons of fuel for a 300 nautical mile trip. This translates to 2.1 gallons of fuel per nautical mile flown.
It's only 83 nautical miles between Kahului and Honolulu airport. So your "factual" 470 gallon figure translates to 5.7 gallons of fuel burned per nautical mile... or 2.7X higher than flightruns' established burn rate. Are they really off by a factor of 2.7X?
I understand that planes burn 15-20% of their fuel on takeoff only (so shorter trips use more fuel per mile)... but still, 15-20% allocated to takeoff does not justify your 470 gallon number. Further, a plane traveling 300 miles will fly to a much higher elevation than one that travels only 83 miles thus burning more fuel.
A 717 (95% load factor) burns only 631 gallons of fuel for a 300 nautical mile trip. This translates to 2.1 gallons of fuel per nautical mile flown.
It's only 83 nautical miles between Kahului and Honolulu airport. So your "factual" 470 gallon figure translates to 5.7 gallons of fuel burned per nautical mile... or 2.7X higher than flightruns' established burn rate. Are they really off by a factor of 2.7X?
I understand that planes burn 15-20% of their fuel on takeoff only (so shorter trips use more fuel per mile)... but still, 15-20% allocated to takeoff does not justify your 470 gallon number. Further, a plane traveling 300 miles will fly to a much higher elevation than one that travels only 83 miles thus burning more fuel.
A 717 never ever reaches optimal cruising altitude - ever and not even close (over 30,000 feet), between OGG-HNL (they get to a max of about 13,000 feet, that's it for about 6 minutes). Practically the entire flight is taxing (which takes a lot of fuel although less than flying) - taking off - a very short cruise at a less than fuel burn optimization (6 minutes) - approach which is another massive fuel burn (they don't glide in) - and another fuel burning taxi.
To simply take a 300 mile trip and reduce that down to a 80 mile flight is highly flawed - most of a 300 mile flight is at a highly efficient cruising altitude at 30,000 feet and moving like highway miles on a car. It is what it is.
And your fuel burn consumption has no taxing involved.
A 717 never ever reaches optimal cruising altitude - ever and not even close (over 30,000 feet), between OGG-HNL (they get to a max of about 13,000 feet, that's it for about 6 minutes). Practically the entire flight is taxing (which takes a lot of fuel although less than flying) - taking off - a very short cruise at a less than fuel burn optimization (6 minutes) - approach which is another massive fuel burn (they don't glide in) - and another fuel burning taxi.
To simply take a 300 mile trip and reduce that down to a 80 mile flight is highly flawed - most of a 300 mile flight is at a highly efficient cruising altitude at 30,000 feet and moving like highway miles on a car. It is what it is.
And your fuel burn consumption has no taxing involved.
LOL.
Yes, the 717 between Maui and Oahu will not reach "optimal" cruising altitude but that doesn't mean the fuel efficiency takes a 200%+ hit
The 7,000 gallons the SuperFerry claims it consumes between Maui and Oahu does not include fuel consumption while docked. The overwhelming majority of non-flight fuel consumed by a plane is when it is sitting idle at the terminal - not while it's physically taxiing towards the takeoff runway. So if you want an apples to apples comparison, you will need to consider the vast amounts of fuel the SF uses while sitting idle at the docks, waiting for hundreds of cars and passengers to board (and disembark).
Bottom line is you can use the 470 gallon figure for a 717, you need to include the hundreds of gallons of fuel wasted by the SF while docked.
Of course none of this really matters as the efficiency of the SF is AT LEAST 10 TIMES WORSE than a jet plane traveling 10X faster if we go with your best-case scenario.
Yes, the 717 between Maui and Oahu will not reach "optimal" cruising altitude but that doesn't mean the fuel efficiency takes a 200%+ hit
It does.
Quote:
Originally Posted by pj737
The 7,000 gallons the SuperFerry claims it consumes between Maui and Oahu does not include fuel consumption while docked. The overwhelming majority of non-flight fuel consumed by a plane is when it is sitting idle at the terminal - not while it's physically taxiing towards the takeoff runway.
Bottom line is you can use the 470 gallon figure for a 717, you need to include the hundreds of gallons of fuel wasted by the SF while docked.
You seem to imply I suggested the superferry was more fuel efficient than 8 717's. I didn't say that. As a follow-up though, at HNL, a 717 usually uses about 500lbs of fuel from gate to runway.
Perhaps you can tell us maintenance costs on 8 jets and useful life vs. Superferry next.
Perhaps you can tell us maintenance costs on 8 jets and useful life vs. Superferry next.
The maintenance cost of the SF will be considerable.
I couldn't compare the maintenance costs of the two travel options (because I don't know what the SF's maintenance costs are) but I can tell you an airline could buy three 717s for the cost of one SuperFerry. That airline can move at least twice as many people as the SF in those three jets in one day's time (with each and every individual passenger saving 3 hours of commute time compared to the SF). And at a lower cost. And at 1/10 the amount of fuel. And without any damage to our marine life.
Let's be real here. Compared to the airlines, the SF is slower, more expensive and magnitudes more damaging to the environment. Let's just throw all common sense out the window in favor of.... an "alternative" to air travel? The mere existence of the SF is literally comical.
You usually make good points from time to time. With this I just don't know.
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