B787-8 analysis

Lissys, the software firm providing the PIANO software, did an analysis for early-built B787's and compared the fuel burn for a 5000nm mission carrying 22 metric tonnes of payload with the B767-300ERW (where W is for winglets). The analysis showed that the B787 with it's "near EIS" performance would burn only marginal less fuel than the B767 (50.1t vs. 50.7t, a difference of 1.18%).
But as the author says, the B787 cruises at Ma0.85, where the normal cruise speed of the B767 is Ma0.8. If one lets the B767 fly at Ma0.85, that would result in a fuelburn of 62.7t, so the difference at same speed is 20%. Of course this is not the orĂ­ginal claim from Boeing (well, at least I hope so...).

But let us look further into the model of the B787 and why the fuelburn is so high relative to what one should expect from that brand-new aircraft with state-of-the-art engines.
Lissys also provides a baseline model of the B787 from 2008, where the original performance Boeing designed the aicraft for is implemented.
We can now take this baseline model and do a "Point Performance" (click this option in the "Output" box)comparison: say, at 35.000ft, Ma0.85 and a weight of 180 metric tonnes.
Here is an excerpt of the output for the baseline model:
 Overall Lift / Drag Ratio = 20.25
 Total Lift Force     1765206. newtons
 Total Drag Force       87169. newtons (43584.newtons per engine)
 Engine / Airframe Performance:
 Total Fuel Flow at Thrust=Drag:       4791. kg/hr
 Specific Fuel Consumption (SFC)       0.5390 kg/hr/kgf
 Specific Air Range (SAR)              .10226 nm/kg
 Emissions Index, NOx                  11.79 g/kg.

And here is the same output for the "near EIS" model:
 Overall Lift / Drag Ratio = 19.39
 Total Lift Force     1765206. newtons
 Total Drag Force       91049. newtons (45525.newtons per engine)
 Engine / Airframe Performance:
 Total Fuel Flow at Thrust=Drag:       5116. kg/hr
 Specific Fuel Consumption (SFC)       0.5511 kg/hr/kgf
 Specific Air Range (SAR)              .09576 nm/kg
 Emissions Index, NOx                  12.03 g/kg.

What do we see?
  1. Lift/Drag Ratio decreased from 20.25 to 19.39. This is about 4.24%. In other words, the aircraft needs 4.24% more thrust to hold that speed (Ma0.85) with that weight (180 t) at that height (35kft).
  2. Specific Fuel Consumption is 0.5511kg/hr/kgf for the near EIS model, where it was 0.539kg/hr/kgf for the 4.24% lower thrust. This is an increase of 2.2%
  3. Accordingly, fuel burn per hour is almost 6.8% higher for the near EIS variant.
From all what we know about the Trent1000 and the GEnx engines, the 2.2% miss in SFC is probably a good guess for the early build B787's.
What I do not understand is the 4.24% decrease in Lift/Drag ratio. That would mean that the wings of the B787 have an aerodynamic problem. If I remember correctly, Boeing onces stated that the wing of the B747-8 (which was designed in the same timeframe) is aerodynamically better than expected, so I would guess that the B787 wing is at least as good as it was planned to be.
So I have my doubts about that part of the analysis.

On the other hand:
If we compare the baseline B787 model and the B767-300ERW, the difference in fuel burn for the 5000nm mission is about 9.5% - significant, of course, but far from being 20% as Boeing always claimed.
Even if we add 4% fuel burn for the "non-wingletted" B767-300ER, we are not near the 20%.

So there is the old wisdom, that you need the right aircraft for the right mission...



In the last few days we saw a few more orders and commitments for the A320neo and B737 MAX. Here is a list:

50 Qatar (+30 options)
50 ALAFCO (+30 options)
30 ACG
45 Spirit Airlines
30 Volaris

B737 MAX:
201 Lion Air (+150 options)
35 ACG

So we now know three committed customers for the B737 MAX out of the nine customers that committed for 700 aircraft - the third one of course being American Airlines, triggering the launch of the B737 MAX with their rejection of the also proposed Boeing NSA and their commitment to take 100 B737 MAX and an option for another 60.
The Lion Air commitment is significant:


Dubai Air Show

If an article published by Reuters is correct, we will see a major order for more B777-300ER's from Emirates at the Dubai Air Show, which opens on Sunday. Rumors are, that Emirates will order another 30-50 of the long-range twin. They still have 41 B777-300ER on order. At the recent order pace that would be good for another 3.5 years. By then the first A350-900 aircraft should arrive. Ordering more B777-300ER could have the following rationalities then:
  • Just more growth...well, it is Emirates!
  • Dumping the A350-900/-1000 order altogether - unlikely!
  • These will in fact be orders for a B777-8 or B777-9 - not too likely at this point, but not completely impossible!
Also, who knows - rumor is that Emirates will also order 30 more A380 - maybe they will announce to be the launch customer for the A380-900...

Embraer decides in favor of EJet's

Embraer decided to abandon plans for a new 5 abreast aircraft for now and instead opted to reengine to EJet's in the latter half of the decade - EIS could be in 2018. Given that Embraer could not do both at the same time - financially, but also due to manpower restrictions, as the KC-390 is in development also, this seems to be a wise decision.
Let us look at the timeline: in 2018 all new engines currently under development for the MRJ, CSeries, the A320neo, the B737MAX, the C919 and the MS-21 will be in service. Of course one could ask at least in case of the latter two if the EIS dates for these will stay where they are now. But Embraer will have a good idea how the engines - two versions of the LEAP (the C919 LEAP-1C will have the same turbo machinery as the A320neo LEAP-1A) and three types of the GTF (MRJ, CSeries and A320neo/MS-21) - are doing during development. An EIS in 2018 would probably mean an engine selection about 5 years earlier, around 2013, maybe 2014. By that time the PW1200G and PW1500G are flying at least on the respective aircraft prototypes and the first PW1100G engine should run on ground (the LEAP-1A seems to be a bit behind).


News about MAX

Jon Ostrower (Flightblogger)  and Scott Hamilton both are reporting about a presentation given by Boeing Commercial Airplanes CEO Jim Albaugh at Goldman Sachs.