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Taxi645
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A growing chasm between max. payload and range with efficiency increasing?

Fri Jan 15, 2021 7:54 am

Which each improvement in efficiency does chasm between max. payload and range increase? With each efficiency improvement the required weight (fuel) to reach a certain destination decreases, yet often the means to achieve these higher efficiencies is by heavier higher bypass engines. So the lower fuel load requires less MTOW but the heavier engines increase OEW. To maintain the required max. payload, maximum range tends to increase beyond what is required for many missions. The distance between two places on the globe does not change (although what you can fly economically of course does expand with increasing efficiency).

Is this chasm really becoming an issue in defining new aircraft models or is there more to it in reality?
Innovation is seeing opportunity before obstacle.
 
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kitplane01
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Re: A growing chasm between max. payload and range with efficiency increasing?

Sat Jan 16, 2021 5:59 am

I think you’re correctly claiming that the extra payload lost per extra mile flown is going down. No .. that doesn’t seem a problem.
 
Some1Somewhere
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Re: A growing chasm between max. payload and range with efficiency increasing?

Sat Jan 16, 2021 8:43 am

I think it's the opposite - a tonne of fuel instead of a tonne of payload gets you a bigger increase in range than it used to, because you can fly further on that extra tonne.

If anything, this is a good thing, at least in some situations. Ferry flights are easier and in a situation where performance is marginal, you don't need to block as many seats/offload as much freight to be able to make the trip.
 
flipdewaf
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Re: A growing chasm between max. payload and range with efficiency increasing?

Sat Jan 16, 2021 9:36 am

I think I see what you are saying, if you design a plane for a standard pax and bags only range then because of the higher specific range of a newer model the max payload range performance would suffer. What we actually see is the opposite if this in that the design case is more skewed towards the max payload case and that, to a large degree, has remained relatively static over time (particularly for the long range jets)and pax only “marketing” ranges have got big instead.

The aircraft that appears to buck this trend is the 779x where the “marketing” range is similar to that if the predecessor, so assuming the marketing range is correctly estimated and they have improved the specific range then something will be awry with the overall payload/range performance, this could either be in the form of max payload available or range at max payload. I am confidently optimistic the marketing range will increase after more testing is done.

Fred


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Taxi645
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Re: A growing chasm between max. payload and range with efficiency increasing?

Wed Jan 27, 2021 9:15 am

Thank you for the answers and apology for the long delay in reply. This document explains it well think: https://www.google.com/url?sa=t&rct=j&q ... Komp_A7U0j

As described in the document on page 13 the number missions at the rights side of the payload-range diagram is relatively limited. With increasing efficiency the area under the right side of the payload-range diagram increases because the decline in payload becomes less steep as range increases. However the mostly flown missions are on the left side of the diagram. So what I'm saying is that yes efficiency give you range "for free" however it is not that beneficial to most missions. If that is efficiency is actually achieved by heavier engines, you might actually be restricting payload at the range where most missions are flown. With older less efficient aircraft the shape of the payload-range diagram might have been more in line with the payload and range distribution of missions flown (of course this also changes depending on what

This is a graph similar to figure 10 on page 13, but than for 60453 flights of the 787-8:

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ElroyJetson
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Re: A growing chasm between max. payload and range with efficiency increasing?

Wed Jan 27, 2021 10:49 pm

Taxi645 wrote:
Which each improvement in efficiency does chasm between max. payload and range increase? With each efficiency improvement the required weight (fuel) to reach a certain destination decreases, yet often the means to achieve these higher efficiencies is by heavier higher bypass engines. So the lower fuel load requires less MTOW but the heavier engines increase OEW. To maintain the required max. payload, maximum range tends to increase beyond what is required for many missions. The distance between two places on the globe does not change (although what you can fly economically of course does expand with increasing efficiency).

Is this chasm really becoming an issue in defining new aircraft models or is there more to it in reality?


I think it is a positive in that it gives airlines increased flexibility. For example, if UA wants to fly 20 tons of cargo from ORD-LHR with the 787-10 they can do so, and then use the same aircraft to fly ORD-HND with full pax and bags. The variance in payload and range can be used beneficially depending on the requirements of each individual flight.

I use the 787-10 as an example because at MTOW it's stated range is "only" 4200 nm. However, with full pax and bags it can comfortably exceed 6000 nm. As you indicated, that is a wide variance, but imho that can add flexibility for an airline.

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