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Old 03-14-2008, 04:52 PM   #51 (permalink)
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Quote:
Originally Posted by RH77 View Post
I may have confused the full swept-back wing in stability issues. (Whichever military aircraft has the adjustable sweep).

RH77

That would have been the F-14A. Not a particularly fun airframe to fly. As wide as it was long with wings spread for takeoff and landing (cats and traps). Made it fly like a frisbee balanced on your finger at low speed. The differential tail had some weird effects as well. Definintely not something you want to do a V2 cut on. Of course, you didn't want that on an A-7E either!

Remember Lift = Drag for most part in autos.

We did downwind recoveries in the Red Sea as common practice because we'd run out of water otherwise. It's a busy shipping area. Not a comforting approach at night. Instead of making the approach at 135knots with a good 15kt headwing giving 2 miles/minute groundspeed, you'd have 150kt groundspeed and very high rates of descent to stay on glideslope. Then in close, you picked up ship wind and such. Neverless, home and your rack was but a three wire away. I can't recall the Skipper ever pointing us down wind on any launch. We stayed at Military Thrust on cat shots, and only pulled back the throttle at the beach if we had IFR wingmen in tow. Speed and altitude are life.

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Old 03-15-2008, 08:01 PM   #52 (permalink)
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No offense taken RH77. The 50 seaters are not very comfortable in the back. I'm 6'5" and can't see out the windows. They are comfortable on the flight deck though. The newer 70 and 90 seaters are much better aircraft.
As far as gearboxes on turboprops go, I used to fly MetroLiners (Texas Lawn Darts). They have the Garrett direct drive turbines with a gear reduction box that reduces the turbine core speed from approximately 35,000 rpm's down to 1000rpm at the prop. These engines were rated for 1000 hp or 1100 hp for takeoff with water/methanol injection. In cruise we planned for a fuel burn of 10 lbs per min or 600 lbs per hr. A prop driven airplane is much more efficient at lower altitudes (below 30,000 ft). You just have to keep the prop tip speeds subsonic. The Garretts are one of the most fuel efficient turbines out there. The engine and gearbox probably weigh less than 200 lbs. Thats a pretty good power to weight ratio.
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Old 12-02-2008, 01:43 PM   #53 (permalink)
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New blog post on this topic

Rick just posted a good blog entry on this subject:

United Hypermiles Trans-Pacific Flights, Proves Flaws with FAA

.
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Old 12-02-2008, 07:18 PM   #54 (permalink)
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Sailor/Pilot

We have to calculate and monitor fuel burn rate at altitude, range, weight and balance and of course manual mixture control and exhaust gas temperature to keep tabs on in the smaller prop aircraft.

Similar issues with sailing as well as aerodynamics.

I think we are generally gadget/vehicle enthusiasts which is why many pilots get into flying in the first place. That and we are generally not allowed to mod our air machines.

Pimp my Airbus 320.

Speaking about hypermiling, my first electric vehicle was my sailboat. Hooked up my 12V cordless drill to a home fabbed prop/shaft to a 12V car battery to bring it in from mooring last fall. Also used it in my kyack to get to the boat. I hate outboard gas motors.
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Old 12-02-2008, 10:35 PM   #55 (permalink)
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OT: orange, I hooked a 17 lbs thrust trolling motor to my 5000 lbs sailboat several times last summer to move it around (when it wasn't windy).

My boat has an INBOARD 2 stroke (sail drive). And I hate it too. Hatehatehate. I'm either going to get a more powerful troller, convert an outboard, or convert the saildrive to electric.
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Old 12-03-2008, 01:43 AM   #56 (permalink)
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Back on topic. Remote control optional:



OT Metro: Also 2 stroke chainsaws, leaf blowers and mowers: Hatehatehate
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Old 12-03-2008, 10:55 AM   #57 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
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.
Some rough data to chew on (learned this in Aircraft design, prof used to work at boeing)

Boeing 747-400 weighs 400,000lbs empty
for a transatlatlantic flight it carries 400,000lbs of fuel
remaining payload available. 20,000 lbs (passengers, luggage, etc...)

Aircraft are sized and designed to fly certain distances with a given amount of fuel. If the trip is less than the max range, it flies with the appropriate amount of fuel.

someone mentioned winlets earlier...
at the end of a wing on a plane flying at ~0.8 mach there is usually a shock that appears on top of the wing near the tip. (air moves faster on top of the wing, and usually exceeds the speed of sound in transsonic flight). Winglets are used to reduce the downwash vorticies that are created by this shock at the end of the wing, which in turn reduces induced drag. In short, adding winglets to your car wont do much.

disclaimer, im not a pilot.
just a senior aero engineering student.
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Old 12-03-2008, 02:23 PM   #58 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
Do airline pilots hypermile?

Or would saving fuel cost too much money overall through lower passenger throughput (due to going slower)?

I would think that an obvious opportunity to save fuel (aside from flying slower) is in the approach to land.

I don't fly often, but have wondered:does a pilot typically make the most of the opportunity to literally glide in toward landing, or do they do the equivalent of what most drivers do: hard on the gas, late on the brakes?
For the airline industry, fuel conservation is a planning factor for every flight. Flight planning is done by a "dispatcher" which is a FAA licensed occupation. All commercial carriers (above 31 pax seats) in the US are mandated by the FAA to use licensed dispatchers to plan all flights.

Flight planning includes:
• current/forecast weather (including clear air turbulence, thunderstorms, wind shear, icing, snow) for takeoff, enroute, landing and alternate airports.

• condition/status of airports & navigational aids

• over water requirements

• arrival & alternate airport weather minimums, runway in use, types of approaches available & minimums

• fuel load (in pounds), max. weight allowed for takeoff (based on length of to runway, obstacles off of end of RW, fuel burn enroute, max allowable landing wt., fuel to alternate airport, etc.

• planning includes spot cost of fuel, planned length of flight, temperatures, winds, expected ATC delays, etc.

Once the dispatcher finishes planning the specific flight, he will then make up a "flight release" on a computer. The "release" includes but is not limited to max allowable takeoff weight, fuel burn to destination, alternate airport, tail number of airplane, maintenance status of airplane, call-sign for the flight, departure, arrival & alternate airport, dispatcher's name. The release is sent to the Captain who reviews the "release". If the Captain concurs with the release, he signs the release. The release then becomes a part of the required documents to be kept on file for that specific flight.

Climb, enroute & descent speeds are determined by a number of factors including route length, fuel costs, winds aloft, temperatures, etc. Pilots have an onboard computer that has many of the variables plugged into it and will determine the climb, enroute & descent speed to the knot or 1/1000 of a mach number.

• airlines estimate their cost to passengers by a "cost per seat mile". It is usually around $0.08-0.15 per seat mile.

• indirect costs include cost of aircraft amortized over its estimated life time in hours, plus all the other costs associated with the airline, (headquarters, gate & ground equip. leases, maintenance, scheduling, IT, advertising, personal, etc.)

Ideally all flights would be a max power climb, economy cruise, & idle descent all the way to a 3 mile final at which time you would configure the aircraft for landing. Ideal doesn't happen very often. Arriving at large to medium size airports can be very complicated.

Example: aircraft arriving from the SW USA destination JFK in NY, start queueing-up over Atlanta, GA, and heading to JFK just off the eastern seaboard.

Boeing 747-400
Max To weight: 875,000 lb
Max Fuel Capacity: 57,285 US gal.
Max range: 7,260 nautical miles
Max seating: 524 seats
Max cargo: 6,025 cu. ft.

Boeing: Commercial Airplanes -- 747 -- 747-400 Technical Characteristics
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Old 12-03-2008, 02:49 PM   #59 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
Rick just posted a good blog entry on this subject:

United Hypermiles Trans-Pacific Flights, Proves Flaws with FAA
Googled "rick harrell united airlines" & got ecomodder hit.

NEWS FLASH Ricky! Anyone with a pulse, 20/20 vision and a command of the English language would know that the FAA-ATC system has an unique ability to remain years behind in the current technology. This has been going on since the invention of the first solid state devise.

Quote from Rick Harrell: "If you’re concerned with emissions, choose an airline with a documented carbon offset scheme."

CHALLENGE: Anyone find an official news release or document from a USA airlines that as a "carbon offset scheme".

What is sad Ricky is , if any US airline did have a carbon offset plan it would be nothing more than a scheme. Scheme another word for BS, or pull the wool over...

Does Ricky Harrell have a Carbon Offset scheme to offset his blog's carbon emissions?
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Old 12-03-2008, 03:15 PM   #60 (permalink)
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Quote:
Originally Posted by Tourigjm View Post
Winglets are used to reduce the downwash vorticies that are created by this shock at the end of the wing, which in turn reduces induced drag.
There's also noise reduction benefits too

Quote:
Blended winglets offer operational and economic benefits to BBJ and 737-800 customers. Mission block fuel is improved approximately 4 percent. Range capability is increased by as much as 200 nmi on the BBJ and 130 nmi on the 737-800 commercial airplane. The reduction in takeoff flap drag during the second segment of climb allows increased payload capability at takeoff-limited airports.

Environmental benefits include a 6.5 percent reduction in noise levels around airports on takeoff and a 4 percent reduction in nitrogen dioxide emissions on a 2,000-nmi flight.

The blended winglets now are available as standard equipment on BBJs, as optional equipment on 737-800 commercial airplanes, and by retrofit for BBJs, 737-800, and 737-700 commercial airplanes already in service. Because the winglet structure and systems follow established maintenance intervals and life cycles, winglets have a minimal effect on airplane maintenance.
Aero 17 - Blended Winglets

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