It's widely acknowledged that jet airliners are environmentally damaging. So why no new turboprop airliners?
Answers:
Props are more efficient than pure jet engines at low altitudes, however jets are more efficient than props at the altitudes needed to fly above any significant weather.
This is due to a prop's inability to grasp the thinner air at altitude and the jets pressure ratio between inlet and and exhaust duct getting better in the cooler air at altitude.
A turbo prop engine also gets more efficient at altitude, but alas it is the propeller that is transmitting the power and that is a catch 22 situation.
Propeller technology and efficiency is coming on in leaps and bounds though, expect more props in the future; although one difficult problem to overcome at present is the noise generated when propeller tips approach the speed of sound. Bigger the diameter of the prop, slower the revs need to be to avoid this, that is why many props now have five or more blades to soak up the power, thus reducing the diameter needed and therefore the tip speed.
They are too slow.
i think its because people want to get to places quicker at any cost
b/c the world today thrives on speed, we only have 24hrs to get done what we need to get done
Because they use basically the same engines. However even the old gas engines were poluters
They are just as bad
Noisy and slow relative to turbofan. The problem you run into with a prop is that once the prop speed approaches the speed of sound, it gets really energy inefficient. We had pretty much reached the limit of what you could do with prop technology by the time we reached the end of WWII. If you want to go beyond 350mph, you need a jet engine, really.
a lot of the problems come from the take off and landing but one of the biggest environmental concerns is due to the hight at which planes fly causing them to form contrails in the sky. These can form clouds and so help to increase global warming as radiation reflected from the earth's surface back to space is then reflected back to the earth from the clouds.
There was an interesting study on the effects of airlines conducted after 11th of September terrorist attack where air travel was greatly reduced globally and this coinsided with an average reduction in cloud coverage of around 7%( this figure may not be accurate. I'm trying to remember a report I read a long time ago!).
After meeting with the head of Shell avaition as part of my undergraduate degree I learnt that there are plans to develop new jet engines and fuels for the future of air travel and that these should start to become apparent from 2030.
1. It would burn more fuel traveling by turboprop than by jet.
Results: environmentally unfriendly.
2. You couldn't carry as many passengers by turboprop, thus requiring more aircraft.
Results: environmentally unfriendly.
3. Your flight would take considerably longer.
Result: This is a "get me there now world" and you wouldn't be able to fly to your favorite tree to hug as quickly.
Because the turboprops are even worse for the environment. Its 'cos they have to opperate longer to get you the same distance as they're slower.
a turboprop is a jet engine
A TURBOPROP IS A JET.
They're adequate for shot distance flights, but too slow for long haul use.
As they tend to use less fuel per seat mile, they do less damage to the environment, but they are still damaging to some extent.
Modern jet and turboprop aircraft aren't nearly as bad as older aircraft.
While turboprops are environmentally friendlier than jets they just don't have the capabilities that jets do. They can't go as fast and they are not capable of moving as many people as needed in this day and age. That is why they are only used for commuter-type flights. The only props in current airline use are the ATR-42, ATR-72, Beech 1900, Beech 2000, and Embrear EMB-120 Brasilia.
Boston and kman are right that turboprops are more efficient on a gallons per seat-mile basis than a turbofan. And that both turbofans and turboprops have a turbine ("jet") engine inside them. They all use "jet fuel", JP-4, etc.
But turbofans can fly higher which gets them above the weather (smoother ride, fewer cancellations) and fly faster (which the customers want). Also, as you get higher, your "mileage" gets better because there is less friction drag in the thinner air. That is true for all planes - reciprocating engined props, truboprops, turbofans or pure jets - up to their service ceiling. But jets can go higher.
I would argue that turboprops are not a whole lot slower than turbofans for 300-900 mile trips and if a turboprop is available from a closer airport, you'll definitely save time. But people want to fly in "jets" and big ones at that, so fuel use per seat-mile isn't the only driver.
I'd add the DeHallivand Twin Otter and Dash-7 and Dash-8 to the list someone gave. I'm on those 20 times a year.
They arent. a full 747 uses less fuel per passenger than a hybrid with a single passenger. A 747 using 70,000 lbs of its thrust uses 3700 gallons an hour. divide that by the passengers (about 500 in a two class setup) and you get 7.4 gallons per passenger per hour. so all you need to do is divide the area covered(400 mph minimum) by the 7.4 gallons and you get 54 miles per gallon, per passenger.
As many others have answered, turboprops are too slow for the majority of routes and may not even be "enviromentally friendly".
However, another commonly held belief by the flying public is that turboprops are more unsafe than their jet engine counterparts. Some people freak out when they see those blades spinning very fast so close to the fusalage. This is another reason why turboprops have been phased out by the majority of airlines.
It's a combination of reasons that causes airlines to choose jets over turboprops.
theyl be same
Turboprops use jet engines, so what's the difference there? Plus, you can fly at 350 mph or at 600 mph, what will people choose? I wonder. The only way not to damage the environment would be to stop the use of fossile fuels, and we can't do that yet.
Turbo prop is still a jet engine. The main shaft still just turns a propellor to get thrusst instead of it coming from the jet exhaust itself!!
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