Dash8widget

Not quite. The reason they go to a higher voltage (240 vs 120) is so that they can deliver greater power (watts) on the same wire or the same power on smaller (ie. lighter) wire. You can deliver the same power at 240 volts as you can with 120 volts but with 240 you would need half the required current. The two big players when it comes to electrical heat generation are current and resistance (W = I2 x R). The big demand on higher voltage systems comes down to adequate insulation of conductors, etc.

Now in the case of a relay, true, the higher voltage can lead to greater arcing between the contacts, which in turn can lead to carbon build up and increased resistance. But, the heat generated across that resistance will still only depend on the current flowing across the resistance. One the circuit is made, the actual voltage that the relay is operating at becomes pretty much a non issue.

If you had said that at any fixed resistance, an increase in the voltage would result in an increase in current and therefore heat, you would be spot on. But an increase in resistance for any fixed voltage (wether it be 120 volts, 240 volts or 2400 volts) actually results in a decrease in current and a corresponding decrease in heat (ohms law, I = E/R. As R gets bigger, I, current, gets smaller)

I'm not an electrical engineer, but I did stay at a Holiday Inn Express last night.

johnso29

Nevermind. Found the answer. Thanks.

acl65pilot

ACL likes "Multi-quote"

What the two major aircraft makers have been saying for a 787/350 type of narrow body clean sheet design is a 20-25% (min) improvement over current models. The composite type barrel that is used on the wb jets needs to be improved on a little more for it to have the durability for a nb jet. (cycle life) If they can get there, they are looking at airframes that do not have corrosion issues, and well as a magnatiude of other benefits. The other components need to mature a little more as well. Boeing and Airbus say that the technology will mature enough to make a viable design in the 2015-2017 time frame with deliveries after 2020.

5-10% (min) improvements may not seem like a lot, but remember that these are all guesses, and if they are better, no airline can afford to be wrong on them. Owning jets that miss this mark will require airlines to reinvest to keep up. The benefits of buying cheap will not be there when comparing the reworked 73N and the 320 compared to the clean sheet composites.

I do agree that the 320 will probably win out on a 73N Neo since the 73N requires some structural work to make the GTF work, whereas the 320 requires almost none.

georgetg

There is no 757 replacement. Nothing comes close to payload/range
But as much as we might be fans of the 757 it's days in domestic service are numbered.
The ETOPS 757 on the other hand will remain in DALs fleet in niche transatlantic service for the next 10-15 years.

The 321neo is a gamechanger....

The 321 with sharklets already offers a 17%/seat fuel burn advantage over the existing 757-200; that's already massive.
The 320neo family will offer an additional 10-16% improvement over that with the PTW1000 (GTF) or the CFM LEAP-X.

The 321neo will offer a nearly 30% fuel burn advantage/seat over the existing 757, this is a no-brainer, there is no need to wait for a clean sheet design.
The 321neo with sharklets can do full payload trans-cons and Hawaii from the West coast, it is a game changer.
In addition the MRO expenses on the 321 are not much over the existing 320 family below the 757, offering additional savings.

Why should all this matter to us as a pilot group?
It's not about Boeing vs Airbus as much as it's about shifting a significant portion of the 7ER flying to the lower rungs of the payscale.

The 7ER category will shrink significantly with the introduction of the 321neo. I only bring this up because as a pilot group we need to be aware of this big shift that is coming our way.

I wouldn't hold my breath on the C-series, the fuselage is still aluminum and the wing composite, It's not that much different from existing designs and will be capital-intensive for the mission it serves, that's why DAL is getting MD90s...

Cheers
George

80ktsClamp

Agreed all around, George. Perhaps another reason to have our pay tables not delinated by type but by larger categories next round?

I am all for something similar to the small narrowbody, large narrowbody, widebody, premium widebody, and SUPER premium widebody ( )... (note there is no such thing as a small widebody!).

Or perhaps short range narrowbody, long range narrowbody, short range widebody, long range widebody, ULR widebody??

Thinking out loud here...


The key is that the company is probably going to come running asking for some sort of relief, and 1. we have to hold the line, and 2. we have to plan ahead for the coming large fleet replacement with next gen engines, wings, and tubes (current 737 cockpit need not apply... for the love of pete update that thing!)


Edit: notice how RJ wasn't in there? those are just short range narrowbodies. bring them on!)

lolwut

As far as pay rates, what Delta has now is way too complicated..... what I'd do....

4 categories, with overrides.

> 50-150 seats (mostly narrowbody north america flying)
> 150-250 seats (large domestic to europe and smaller asia flying)
> 250-350 seats (most large international flying)
> 350-450 seats (large long haul)

10% (or whatever you choose) override for international flying
20% (or whatever you choose) override for intercontinental flying


Of course, all these numbers could be tweaked to your pleasure. Theres no need for dozens of different pay scales, there are only 4 or so real categories of flying a major airline does. Alternatively, if you don't want to base it on seats (seat counts change, similar seating planes do different missions...), you could could make 4 MTOW categories and do the same sort of deal.


0-199k lb
200-349k lb
350-599k lb
600k+ lb

Sink r8

And he's using complete sentences! I was getting used to the "Oracle of Delphi" thing, where you would shake your head for a while, and kinda think you knew what he meant.

Carl Spackler

YES!!

Carl

Bucking Bar

Fuel is up 2.5% for the week ending Friday and 17.6% over the last year. You are right about the factors which will push fuel, along with other commodities higher.

acl65pilot

I agree on the 321. It will make the 757 a niche aircraft to those high hot airport. I do agree that the 757 will never be revived, but one can dream!

The nice thing about the 757 is that we fly so many of them that the pilots can do a wide variety of missions.

Also we have a precedence in pay rates. They bring the 321 on, it will require a sub category override or a blended rate that the 73N 320, DC-9 and 7ER now have. I am sure the MD's will be the end of the next contract as well. The point is that we have that practice on our side.

Like I said, I would floored to see DAL sign on to a huge NB order that would total replace a fleet with a large number of deliveries prior to 2020. If anything we may see this stuff start arriving in 2015 and beyond.

We may see a C-Series size small order, and a large jet order, but the MD-90's will be a band aid until DAL is 1005 willing to commit the capex on a brand new fleet. You do make a good point that if the 321, and 320Neo are bought, the savings may be enough for DAL to wait until the true next gen stuff is proven to be workable. I do admit that is RA's way. I just do not think the 757's will be replaced on a large scale.

If they go this way, they will probably start with 320 replacement and then move in to 757 replacement as time moves on. That makes more sense to me.