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Old 02-23-2008, 12:59 AM   #41 (permalink)
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Old 02-23-2008, 01:00 AM   #42 (permalink)
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Old 03-09-2008, 11:45 AM   #43 (permalink)
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This is interesting. Claiming better FE then a Prius. 97.5g of CO2 per passenger km.

Quote:
easyJet has today become the first airline to outline the environmental requirements that must be met by the next generation of short-haul super-clean aircraft; and unveiled its design of what such an aircraft could look like for operation by 2015.

Dubbed the easyJet ecoJet, the aircraft would need to be 25% quieter and would emit 50% less CO2 and 75% less NOx than todays newest aircraft (the 737 and A320 families of aircraft).
Quote:
The design will contain a number of key features to make it radically more environmentally efficient:

* Rear-mounted open-rotor engines offer unrivalled environmental performance for short-haul flying due to their higher propulsive efficiency. However, there are significant difficulties in fixing such a large engine under a wing of a narrow-body aircraft, making rear-mounting of the engines the optimum solution
* A lower design cruise speed to reduce drag and a shorter design range to reduce weight
* Noise reductions are expected to come from a gear box between the engine and the open-rotor blades keeping them subsonic during take-off and landing, the use of the rear empennage to shield the ground from engine noise, and airframe improvements (such as no slats on the front of the wing)
* The airframe will be made of advanced weight-reducing materials similar to those used in current projects like the Boeing 787, which itself is estimated to be 27% more fuel efficient than the aircraft it will replace in many fleets
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Old 03-10-2008, 12:52 AM   #44 (permalink)
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Props to Props

Quote:
Originally Posted by Lazarus View Post
This is interesting. Claiming better FE then a Prius. 97.5g of CO2 per passenger km.
This is a VERY interesting concept.

I have to stress something that many potential fliers fear: The Propeller!

I give props to the props. I fly on propeller planes, on the average of once a month (over the last 7-8 years), and I'm still here -- it's safe!. They're more efficient than jets, slightly slower (maybe 5-10 minutes per hour of flight) -- but that's what they were meant to do: Regional Service.


Saab 340 Twin Turbo-Prop

My least favorite plane is the "Regional Jet". 50 Passengers crammed into a 2X2 seating arrangement, and even on flights in excess of 2 hours. Painfully uncomfortable -- and forget about getting any work done (plus larger airliner pilots are short-changed). The single row on each side makes every seat a window and aisle. Everybody wins.

My questions for the "ecoJet" design:
  1. How does the gearbox reduce the prop noise? Propellers are generally "Featherable" meaning they twist to produce zero forward thrust (or a reversing/resistance action), or angled to produce forward pull (controllable). They make noise in the variety of settings.
  2. Wings swept forward = less stability. I wonder if complex computer-controls and systems (similar to the F-16 SFW) will be required to maintain stability.

I can't recall seeing a twin turbo-prop, fuselage-mounted engine layout with a low-wing setup. Cool!

Review: Props are efficient, safe, and hopefully making a comeback.

Great link, Laz!

RH77
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Old 03-13-2008, 09:55 PM   #45 (permalink)
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I flew the 50 seat regional jets and the larger turbo props for several years out of Denver. We definitely adhered to company fuel savings procedures. As already mentioned, we usually taxied on a single engine. We had precise climb profiles designed for both fuel efficiency and performance. In cruise we were required to cruise at .76 mach (approx. 440 kts) although the aircraft was capable of much faster. All aircraft parameters are recorded so the company knows if you are pushing up the throttles. If we were really behind, we would speed up to make up time but that was the exception. We also cruised at as high an altitude as we could. A turbine engine is normally aspirated and the higher it flies the less power it makes and thus thte less fuel it burns. For the turboprops, this was usually at 29,000 ft. At that altitude our fuel flows were probably 20% lower than cruise in the upper teens or low 20's. The only problem with the regional jet is that the 50 seaters are gutless at altitudes above the low 30s' in the summer when the temps are higher at altitude. As far as descents go, when assigned a lower altitude, the thrust levers go to flight idle and we descend at the same speed we were cruising. All airliners have spoiler/speedbrakes to help with descents. On landing approach in the landing configuration (gear down/flaps down) you actually have to keep the power up to counter the added drag of the gear and flaps. Power didn't come back to flight idle until 50 feet above the runway. Once on the ground, we usually shut one engine down. Fuel costs are the #1 expense for the airlines and they do what they can to save.

Last edited by cajun98; 03-13-2008 at 09:56 PM.. Reason: sorry for the double post; my bad
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Old 03-13-2008, 10:49 PM   #46 (permalink)
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Hey cajun98 - thanks for the input.

I have to ask... everybody: what is it with fuel economy / modding and pilots? Based on the responses in this thread, I definitely get the impression there's a disproportionately large number of flyers on the forum.
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Old 03-13-2008, 11:21 PM   #47 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
Hey cajun98 - thanks for the input.

I have to ask... everybody: what is it with fuel economy / modding and pilots? Based on the responses in this thread, I definitely get the impression there's a disproportionately large number of flyers on the forum.
I bet you would get an equal amount of responses if you asked do sailboat/ship captain hypermile ?
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Old 03-13-2008, 11:26 PM   #48 (permalink)
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Good point.

And re: pilots - someone did point out that fuel weight is something very front of mind for planning trips as well. So it's something thought about more than not.
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Old 03-13-2008, 11:50 PM   #49 (permalink)
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Quote:
Originally Posted by RH77 View Post

My questions for the "ecoJet" design:
  1. How does the gearbox reduce the prop noise? Propellers are generally "Featherable" meaning they twist to produce zero forward thrust (or a reversing/resistance action), or angled to produce forward pull (controllable). They make noise in the variety of settings.
  2. Wings swept forward = less stability. I wonder if complex computer-controls and systems (similar to the F-16 SFW) will be required to maintain stability.

I can't recall seeing a twin turbo-prop, fuselage-mounted engine layout with a low-wing setup. Cool!

Review: Props are efficient, safe, and hopefully making a comeback.

Great link, Laz!

RH77
I not sure about your question but I think the gearbox is just slowing down the propeller rotation speed. The lower the rpm the quiter.

The forward sweep wing has been around for a very long time. This is fast and a very stable platform with lots of room inside. This is a pic of it. There are probably less then a half dozen left flying in the US 15 years ago so there probably are not any around now. They have a tendance for corrosion and the cost to repair was not worth it. The company that had one sold it to a production company for a plane crash scene when it was deemed unairworthy due to the corrision.
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Old 03-14-2008, 12:10 AM   #50 (permalink)
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Quote:
Originally Posted by Lazarus View Post
I not sure about your question but I think the gearbox is just slowing down the propeller rotation speed. The lower the rpm the quiter.

The forward sweep wing has been around for a very long time. This is fast and a very stable platform with lots of room inside. This is a pic of it. There are probably less then a half dozen left flying in the US 15 years ago so there probably are not any around now. They have a tendance for corrosion and the cost to repair was not worth it. The company that had one sold it to a production company for a plane crash scene when it was deemed unairworthy due to the corrision.
Ah, got it now. The prop can probably turn slower, under power, with the gearbox -- whereas conventional turbines have a minimum prop RPM.

I may have confused the full swept-back wing in stability issues. (Whichever military aircraft has the adjustable sweep).

Also, I must apologize to Cajun98 for my description of the 50-seat RJs. I fly them regularly and rely on their service. No offense to your aircraft. I've recently had a run of flying them everywhere lately and getting pressed up against the window by a linebacker-type for a couple hours at a time. A bit weary It beats the middle seat in an A319

EDIT: ...and welcome to the site, by the way!

RH77

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Last edited by RH77; 03-14-2008 at 12:12 AM.. Reason: welcome
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