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what might look like a step backwards is

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actually two giant steps forward on the

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since 1941 the Lewis Research Center has

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developed an international reputation

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for its research on jet propulsion

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systems however in 1977 the researchers

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at Louis began to take a new look at the

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propeller their challenge was to combine

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the efficiency of the propeller with the

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power of the turbine engine what has

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evolved is ATP the advanced turboprop

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project

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Keith severs manager of the NASA

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advanced turboprop project office at the

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Lewis Research Center back after World

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War two jets for the thing the coming

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thing her powers were very efficient in

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those days but they couldn't go fast it

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couldn't go to high altitudes and quite

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frankly they were not jazzy like jet

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engines and which gave way them to

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turbofan engines and high bypass ratio

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engines and when fuel was cheap people

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didn't worry much about it 10 cents a

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gallon as long as they get speed high

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altitude capability which the air

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transport system required propellers

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just kind of withered on the vine for 20

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or 30 years the Arab oil embargo of the

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early 70s not only hit American

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consumers at the corner gas station but

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was also reflected at the airline ticket

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counter due to the soaring price of jet

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fuel in 1973 the price of a gallon of

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jet fuel was 12 cents and represented

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one-quarter of the direct operating cost

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of the jet by 1979 the price had risen

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to 63 cents a gallon and represented

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half of the direct operating cost in

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1981 the cost of jet fuel was over a

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dollar eight cents a gallon with the

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rising fuel prices a fuel efficient

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propeller engine again became the object

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of an aeronautical propulsion research

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effort the researchers objectives were

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to develop a powerplant that would be

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fuel efficient dew point eight mach

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cruise at 35,000 feet operate at a

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reduced noise level

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these propellers look a lot different

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there are very highly swept they're very

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thin compared to old propellers and the

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thing it hits you first is they're eight

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to ten blades on these are rather than

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three or four is that you've been

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accustomed to in the past and what the

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sweep doesn't in the propeller end of

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finis is is to reduce the drag losses at

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the higher tip speeds and higher Mach

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numbers also helps to reduce the source

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noise of the propellers the higher blade

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count and we've loaded these blades up

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much higher than old propellers so we

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get a lot more power at a lot smaller

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diameter and this saves weight on the

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propeller say it's weight on the engine

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and it also packages better on the

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aircraft earlier two turbo props were

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limited both in horsepower and in flight

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speed mainly because of the

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compressibility effects that occur at

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the propeller tips with the recent

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advances in computer design technology

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we are now able to optimize the blade

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shape to minimize the compressibility

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effects occurring at the blade tips

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allowing the planes to fly faster up to

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six hundred miles an hour and at higher

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altitudes up to 35,000 feet as you

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approach the speed of sound you run into

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a problem where the apparent pressure

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that you're trying to push through

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suddenly takes a quantum leap and

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because the blades are very large in

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diameter to 13 feet in diameter the tip

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speed is upwards of 800 feet per second

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which is just under Mach 1 or the speed

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of sound as you try to push through that

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Mach 1 range you run into this

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compressibility factor it's almost like

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running into a brick wall with the blade

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the blade construction is now a

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composite type arrangement where you

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have a metallic leading edge such as

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aluminum and a graphite epoxy resign'd

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internal construction that allows the

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blades to be very lightweight and

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cause they're lighter weight minimizes

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the centrifugal stresses that occur when

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the propeller system is rotated at

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12,000 rpm ultimate goal is to save fuel

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commercial aircraft and also military

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aircraft were it can be applied and this

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fuel saving is very dramatic compared to

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the fuel burn that aircraft have today

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such as a 727 737 that type of air cream

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aircraft a prop van driven airplane can

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do the same mission that like forty to

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fifty percent of the fuel that they use

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today if you look at just the u.s. fleet

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existing today for medium to short range

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aircraft I'm talking 727 737 is dc-9s

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md-80s those aircraft in a typical year

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burn about 5 billion gallons of fuel if

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these aircrafts were equipped with pop

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fans they could do the same mission

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they're doing today and save two to two

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and a half billion gallons of fuel per

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propeller-driven airplanes have

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traditionally been noisy advanced

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turboprop researchers are tackling the

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problem of trying to build a turboprop

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to rival the relative quiet and

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smoothness of the ship well we've had to

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look at the entire aircraft as a system

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we didn't look just at sticking a new

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widget called a prop fan on them better

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look at what to do they do to the rest

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of the aircraft and particularly we're

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concerned about passenger comfort it

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doesn't matter how much fuel was saved

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if people don't like it or they're

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uncomfortable sound vibration and

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they're not going to write it so it

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won't matter so part of our project goal

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is to to make sure that people have the

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same comfort that they're used to on

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today's wide-body aircraft in addition

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we're concerned about community noise

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these things are allowed and we have to

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provide the technology sort of the

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equivalent existing far 36-yard stage

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three regulate

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by around airports and communities

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most the time we really don't even know

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what's running inside the cockpit it's

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that quiet and we're only what 15 feet

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away from after several years of wind

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tunnel and static engine testing a full

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flight test of the advanced propeller

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system was held on May 19 1987 at

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Lockheed Georgia company in Marietta

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Georgia so far operation has been very

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good everything is about as predicted

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that the engineers had predicted from

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their initial assessment of the program

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we haven't really had any big surprises

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I should say when you pull the prop fan

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in and add power to it the pilot really

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knows it but there again this airplane

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wasn't really designed to fly with an

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engine out on a on the left wing but

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again what our engineers predicted is

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pretty much what's happening with the

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airplane so I'd have to say so far it

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looks good so far it looks very good if

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all goes to plan prop fans will probably

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be fitted on short to medium range

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aircraft we hope to have as a part of

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the project goal to have a technology in

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hand by the end of 1980s so that

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industry the engine people the aircraft

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people can make marketing decisions

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because it involves a lot of private

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capital that's a make sure breaks our

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company so the way things are proceeding

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right now it looks like Boeing and

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McDonnell Douglas are aiming for new