Re: Piston airliners
Sat Dec 26, 2009 5:15 pm
Thats a great idea Mr Greenwood, every passenger should try a recip airliner once to see where it all began and how improved things are today (I say improved not perfect before someone starts shooting at me!!) 
Re: Piston airliners
Sat Dec 26, 2009 5:53 pm
Don't know about the tin foil deal. But the tin cup tells me at 40,000 hours that would be about
10,000,000 gallons of fuel burned and that is just one engine. And I'm being real conservative on those figures its probably more like twice that figure. No matter what is said about turbines they are still fuel gulping blow torches. Tell me how long could you run an R-3350 on that much fuel?
I don't think the average person realizes how much fuel is burned up in jets. Please direct me to the FAA information on that!
10,000,000 gallons of fuel burned and that is just one engine. And I'm being real conservative on those figures its probably more like twice that figure. No matter what is said about turbines they are still fuel gulping blow torches. Tell me how long could you run an R-3350 on that much fuel?
I don't think the average person realizes how much fuel is burned up in jets. Please direct me to the FAA information on that!
Re: Piston airliners
Sat Dec 26, 2009 7:24 pm
Are you talking about consecutive operating hours without any mechanical failures in that wager? As I recall, the R3350 was just slightly more reliable than the R4360. I've never heard of a modern (since 1948) turbine engine that wanted to become a pyrotechnic display with no notice. The romance is long gone from commercial flying, the necktie and white gloves are gone, now a days its a friggin' GREYHOUND with wings, airplanes full of over stressed, overhyped, smelly, rude, inconsiderates about 1/3rd of whom bring screaming offspring that they've never given a waking thought to teaching how to be quiet, who only want one thing-to be 'there' 'now'. And I sort of agree, I'd rather, if I had to, spend 6 1/2 hours getting from New York to London @ 41000 feet than 16 hours @ 22000 feet ad two fuel stops in the middle. Like Bob Euker said in 'Major League' 'suffering from a bad case of propeller lag'
Your supply chain better be pretty long and deep and filled with cylinders, link rods, blower cases, and prop governors if you even dream of running something a mechanically complex as a 3350 for 40000 hours uninterrupted.
The only alternative to consuming all those gallons of fuel would be man carrying kites, and I don't see SWA or RYANAIR clamoring for fleets of kites. I love big recips as much as the next person, nothing makes the hair on my neck stand up more than a group of R-2800's running or a MERLIN @ 50 In/Hg, but I'm also a practical sort and the glory days of piston driven commercial aviation are long, long past. I agree with Bill Greenwood that it would be fun to see someone incorporate piston airliners into some sort of fleet but I also know that it's right near impossible to get a 121 cert to operate DC-3's in pax configuration outside of places like Alaska, that's why things like SPUNKMEYERs flights in the Bay area went away, the legal hoops and insurance premiums made everyone stop doing that some time ago. I also have a deep appreciation for steam locomotives and their complexities, and hope one day after I retire to witness the Union Pacifics CHALLENGER run past me, but I don't see AMTRAK or CON-RAIL using steam either.
www.FAAhome.gov
Your supply chain better be pretty long and deep and filled with cylinders, link rods, blower cases, and prop governors if you even dream of running something a mechanically complex as a 3350 for 40000 hours uninterrupted.
The only alternative to consuming all those gallons of fuel would be man carrying kites, and I don't see SWA or RYANAIR clamoring for fleets of kites. I love big recips as much as the next person, nothing makes the hair on my neck stand up more than a group of R-2800's running or a MERLIN @ 50 In/Hg, but I'm also a practical sort and the glory days of piston driven commercial aviation are long, long past. I agree with Bill Greenwood that it would be fun to see someone incorporate piston airliners into some sort of fleet but I also know that it's right near impossible to get a 121 cert to operate DC-3's in pax configuration outside of places like Alaska, that's why things like SPUNKMEYERs flights in the Bay area went away, the legal hoops and insurance premiums made everyone stop doing that some time ago. I also have a deep appreciation for steam locomotives and their complexities, and hope one day after I retire to witness the Union Pacifics CHALLENGER run past me, but I don't see AMTRAK or CON-RAIL using steam either.
www.FAAhome.gov
Re: Piston airliners
Sat Dec 26, 2009 9:34 pm
Not many years ago I used to do a lot of travel between Seattle and Dutch Harbor, Alaska. Several times I was fortunate enough to ride on the 1957 Lockheed Electra between Dutch Harbor and Anchorage. I think it was operated by Alaska Airlines. The interior was refitted to the original material and color scheme and the flight attendants were usually high on the senority list as it was considered good duty on that plane. It may still be flying.
Re: Piston airliners
Sat Dec 26, 2009 10:02 pm
engguy wrote:Don't know about the tin foil deal. But the tin cup tells me at 40,000 hours that would be about
10,000,000 gallons of fuel burned and that is just one engine. And I'm being real conservative on those figures its probably more like twice that figure. No matter what is said about turbines they are still fuel gulping blow torches. Tell me how long could you run an R-3350 on that much fuel?
I don't think the average person realizes how much fuel is burned up in jets. Please direct me to the FAA information on that!
At the risk of beating a dead horse:
Next time I go into work I will probably haul 180 people coast to coast in a B757. At an average total fuel flow of a little under 900 gallons per hour I'll burn a little less than 5,000 gallons of fuel to do it. That's about 28 gallons per passenger (seat)
Just guessing here: Average 100 gal per engine in a Connie. 290 kts TAS. 90 seats. (just guesses, please, anyone, I'd be interested to know some good numbers!!) I figure the Connie will burn 3,310 gallons of gas for the same leg. That works out to 36 gallons per passenger.
In fairness, I'm guessing the 707 burned almost twice that amount of gas to carry probably the same # of people as the 757, but with fuel at 20 cents per gallon, the other efficiencies made up the difference.
Having said all that, sign me up. I'd go fly the recips!
Best
Re: Piston airliners
Sat Dec 26, 2009 11:12 pm
buffcc,
First off, welcome to the nut house! It looks like you'll fit right in-if you were flying between ANC and Dutch Harbor it was probably on REEVE ALEUTIAN, and it would seem correct because Bob Reeve trying to get a penny nailed to a phone pole is why the world has copper wire. Back in the day virtually no one else flew the chain except RAA, now I watch 'Deadliest Catch' and see folks getting on and off of METROLINERS in St. Paul Island and its a very long way out in very green water and crap weather.
In the very early days jet fuel was about 6 or 7 cents a gallon and there were no speed restrictions below 10K so the crews kept the levers against the panel until the outer marker, setting loads of city to city speed records that haven't been eclipsed. One of my favorite early days jets were ALASKAS CV-880 and CV-990 between Seattle and Anchorage, those things just howled along and they were comfortable and pretty quiet at least forward of the trailing edge of the wing.
and engguy, I think your fuel useage math is on a par with the people who feel it's physically impossible for the earth to support enough cows to supply Mickey D's with that much hamburger
First off, welcome to the nut house! It looks like you'll fit right in-if you were flying between ANC and Dutch Harbor it was probably on REEVE ALEUTIAN, and it would seem correct because Bob Reeve trying to get a penny nailed to a phone pole is why the world has copper wire. Back in the day virtually no one else flew the chain except RAA, now I watch 'Deadliest Catch' and see folks getting on and off of METROLINERS in St. Paul Island and its a very long way out in very green water and crap weather.
In the very early days jet fuel was about 6 or 7 cents a gallon and there were no speed restrictions below 10K so the crews kept the levers against the panel until the outer marker, setting loads of city to city speed records that haven't been eclipsed. One of my favorite early days jets were ALASKAS CV-880 and CV-990 between Seattle and Anchorage, those things just howled along and they were comfortable and pretty quiet at least forward of the trailing edge of the wing.
and engguy, I think your fuel useage math is on a par with the people who feel it's physically impossible for the earth to support enough cows to supply Mickey D's with that much hamburger
Re: Piston airliners
Sun Dec 27, 2009 12:43 am
I knew a guy that sold fuel to airlines in the old days. The price he mentioned to me back in the early 70's was 3 cents a gallon for jet fuel. Why not all the normal folks got to pay how many times more for automobile fuel, so that pretty much pays to refine the nice kerosene for the airlines.
On the 757, what is the power setting for that flight? And what engines? What thrust level at cruise and what TSFC?
The math is close. If I remember correctly a JT9D burns a gallon a second at 70% I used lot less than that. A jet engine is a constant combustion engine, and not positive displacement, the air and fuel pretty much freely flow through it.
On the 757, what is the power setting for that flight? And what engines? What thrust level at cruise and what TSFC?
The math is close. If I remember correctly a JT9D burns a gallon a second at 70% I used lot less than that. A jet engine is a constant combustion engine, and not positive displacement, the air and fuel pretty much freely flow through it.
Re: Piston airliners
Sun Dec 27, 2009 2:04 pm
Well, even the jets quit from time to time. Still.
I've had 3 engine failures in my carreer, all on JT8Ds, all on twins, last one in about 1996.
Eight years to go.
Dave
I've had 3 engine failures in my carreer, all on JT8Ds, all on twins, last one in about 1996.
Eight years to go.
Dave
Re: Piston airliners
Sun Dec 27, 2009 5:31 pm
Re: Piston airliners
Sun Dec 27, 2009 5:38 pm
engguy wrote:I knew a guy that sold fuel to airlines in the old days. The price he mentioned to me back in the early 70's was 3 cents a gallon for jet fuel. Why not all the normal folks got to pay how many times more for automobile fuel, so that pretty much pays to refine the nice kerosene for the airlines.
On the 757, what is the power setting for that flight? And what engines? What thrust level at cruise and what TSFC?
The math is close. If I remember correctly a JT9D burns a gallon a second at 70% I used lot less than that. A jet engine is a constant combustion engine, and not positive displacement, the air and fuel pretty much freely flow through it.
PW 2037's in the 757 I fly.
My memory of the JT9D is that typical cruise FF is about 4500 Pounds per hour per engine. That works out to about 1 gallon every 11 seconds....
Re: Piston airliners
Sun Dec 27, 2009 6:38 pm
Okay then actually its 4 gallons per every 11 seconds then on a 4 engine plane.
What is the cruise setting? % of throttle.
What is the cruise setting? % of throttle.
Re: Piston airliners
Sun Dec 27, 2009 6:55 pm
Since you don't like working in the real world and want to work theoreticals only, here's the "theory" of how jets become more efficient than pistons.
First, there is no set "cruise power" setting on a jet aircraft. On a piston, you fly a "power profile", setting specific power settings to get the most efficient use of the piston because fuel consumption doesn't change much with altitude. On a jet, since your fuel efficiency improves with altitude, you fly a speed profile. You fly set speeds at all times and your power will be set to hold that speed. As you get lighter, the power setting decreases, thus your fuel efficiency is the best just prior to top of descent and in the descent as your engines are running at their lowest power for the flight.
This is where jet's come into their own. On a piston, because of the way the plane is designed, the thermodynamics of a cooling engine (i.e. shock cooling) and the inertia of the propeller (i.e. not allowing the prop to drive the engine) you must maintain power during the entire descent, making your descent much less efficient than it could be. In a jet, this is not a concern, so you just bring the engines back to flight idle, tip the nose over, and control your speed in the descent by pitch (and thus rate of descent). By delaying your descent as long as possible and using your speed control devices (speedbrakes, gear, and/or thrust reversers in idle reverse depending on the jet) you can actually save a lot of fuel in a jet, something not possible with the piston.
In 1 hour of cruise a jet may burn more fuel than a piston, but it also travels much further in that time and does so in a manner where winds aren't the major issue they were with pistons as they can pick a lot more altitudes to find favorable winds at, something many pistons couldn't do (you could descend but not climb due to weight, thus descending meant you went slower over the ground and negated the gain in favorable wind conditions).
First, there is no set "cruise power" setting on a jet aircraft. On a piston, you fly a "power profile", setting specific power settings to get the most efficient use of the piston because fuel consumption doesn't change much with altitude. On a jet, since your fuel efficiency improves with altitude, you fly a speed profile. You fly set speeds at all times and your power will be set to hold that speed. As you get lighter, the power setting decreases, thus your fuel efficiency is the best just prior to top of descent and in the descent as your engines are running at their lowest power for the flight.
This is where jet's come into their own. On a piston, because of the way the plane is designed, the thermodynamics of a cooling engine (i.e. shock cooling) and the inertia of the propeller (i.e. not allowing the prop to drive the engine) you must maintain power during the entire descent, making your descent much less efficient than it could be. In a jet, this is not a concern, so you just bring the engines back to flight idle, tip the nose over, and control your speed in the descent by pitch (and thus rate of descent). By delaying your descent as long as possible and using your speed control devices (speedbrakes, gear, and/or thrust reversers in idle reverse depending on the jet) you can actually save a lot of fuel in a jet, something not possible with the piston.
In 1 hour of cruise a jet may burn more fuel than a piston, but it also travels much further in that time and does so in a manner where winds aren't the major issue they were with pistons as they can pick a lot more altitudes to find favorable winds at, something many pistons couldn't do (you could descend but not climb due to weight, thus descending meant you went slower over the ground and negated the gain in favorable wind conditions).
Re: Piston airliners
Sun Dec 27, 2009 9:29 pm
engguy wrote:Okay then actually its 4 gallons per every 11 seconds then on a 4 engine plane.
What is the cruise setting? % of throttle.
Depends on weight and altitude. Might be close to 100% at max altitude for a given weight. We don't have an easy way of determining power as a percentage of total available. It isn't really a useful number.
Steve
Re: Piston airliners
Sun Dec 27, 2009 10:30 pm
There are a bunch of oil rigs in North Sea that use industrial versions of the RR Avon for powerplants. The inspection process involves flying past the oil rig in a helicopter while the passenger does "Inspection by binoculars" to see if there is heat coming from the exhaust. If heat is seen they fly on to the next oil rig...
Re: Piston airliners
Mon Dec 28, 2009 7:51 am
engguy,
I'm not sure what you're getting at but maybe the moral of the story is:
If you want to go flying for an hour, leave the 747 in the hangar. You're correct, it burns a boatload of fuel.
If you want to economicaly transport a bunch of people:
Jet airliners are the most fuel efficient way to fly them. Bigger and newer is generally better for fuel efficiency.
Recips are classy and fun and cool, but not as fuel efficient. (I'm still waiting for the address for "Emperor Airlines.")
If you want to go green and burn as little fuel as possible, consider the following:
A full 757 gets about 75 passenger miles per gallon
Our minivan (18 mpg highway, 7 seats) gets 118 passenger miles per gallon if we fill all the seats.
A full passenger train gets somewhere near 500 passenger miles per gallon.
You could use a bicycle.
Your mileage may vary.
If you're an air force, you want the jets for the simple reason that speed = life. If you want to go as fast or faster than the bad guys, you better have a jet no matter how much gas it burns. Nobody ever said war was "green."
I'm not sure what you're getting at but maybe the moral of the story is:
If you want to go flying for an hour, leave the 747 in the hangar. You're correct, it burns a boatload of fuel.
If you want to economicaly transport a bunch of people:
Jet airliners are the most fuel efficient way to fly them. Bigger and newer is generally better for fuel efficiency.
Recips are classy and fun and cool, but not as fuel efficient. (I'm still waiting for the address for "Emperor Airlines.")
If you want to go green and burn as little fuel as possible, consider the following:
A full 757 gets about 75 passenger miles per gallon
Our minivan (18 mpg highway, 7 seats) gets 118 passenger miles per gallon if we fill all the seats.
A full passenger train gets somewhere near 500 passenger miles per gallon.
You could use a bicycle.
Your mileage may vary.
If you're an air force, you want the jets for the simple reason that speed = life. If you want to go as fast or faster than the bad guys, you better have a jet no matter how much gas it burns. Nobody ever said war was "green."