Leeham News and Analysis
There's more to real news than a news release.
Bjorn’s Corner: Engine efficiency revisited
By Bjorn Fehrm
18 December 2015, © Leeham Co:Part of the discussion following last week’s article around quad or twin engine airliner designs was about engine efficiency and specifically around the engine’s thermal efficiency as a function of Pressure Ratio, PR.
I got the question, if an engine working at a higher pressure ratio was therefore working at a higher thermal efficiency. I knew enough on the subject to know I did not have a good answer without doing a bit of checking; jet engines are no simple contraptions.
I have previously written about turbofan efficiency in a Corner. The article was focused around propulsive efficiency. Now we will have a look at the other part of overall engine efficiency, the thermal efficiency or the efficiency of the core.
Bjorn’s Corner: Twins or quads?
By Bjorn Fehrm
11 December 2015, ©. Leeham Co: The debate over two or four engines for long range aircraft is as old as the jet airliner. A number of myths have been pedaled over the years over the virtues of the one over the other. The myths have even been presented by airline CEOs as “facts that are known in the industry.”
Having done several in-depth comparisons of two-vs-four engined long range aircraft, we can’t find the patterns that these myths propel: that a quad is less efficient than a twin and should have higher maintenance costs. What we see is that it is all dependent on what one compares and to what technology generation the one or the other aircraft belong.
When we didn’t get the same results as the myths on a number of areas, we started to wonder what could have created the myths in the first place. Looking at what four engined airliners could have been the source of the rumours, we started to see a pattern. It was a pattern of apple-and-oranges being compared and wide ranging conclusions being drawn.
Here is what we found. Read more
Bjorn’s Corner: Modern IFE
By Bjorn Fehrm
04 December 2015, ©. Leeham Co: During the last two weeks I have been busy explaining how a mid-life long range aircraft is refurbished. The articles have been about how to prepare 10 year old Boeing 777-200ER and Airbus A340-300 for their second half of life.
One of the things that must be done is updating the part of the aircraft that meets the customer, the cabin. Most passengers don’t know much about the aircraft they are flying, but they can tell you if the seats were comfortable, if there was enough leg space and if the movies on the entertainment system were any good.
This means that if the cabin is brought up to a modern standard with lie-flat business seats, refreshed interior surfaces and textiles, and if there is a personal IFE unit with good content, the passenger will not reflect over that he flies an old aircraft.
Such refreshes cost a lot of money. Without changing all items in a 300 seat cabin, one is easily at between $5m-$10m for material and installation. One of the problems when wishing to keep existing seats, for economic reasons, is that it is virtually impossible to implement in-seat IFE to an existing seat. Luckily there are other solutions. Read more
Bjorn’s Corner: Aircraft deterioration
By Bjorn Fehrm
27 November 2015, ©. Leeham Co: In an article yesterday, we looked at the economics of acquiring used aircraft for long range operations. We compare getting a second hand Boeing 777-200ER or Airbus A340-300 to operate as a long range complement to an existing network or to start a charter operation to destinations further away than previously possible.
The low fuel cost has made longer range destinations economical for a number of business models and the low capital cost and good conditions of these aircraft open new opportunities.
One of the things that must be considered in such analysis is the deterioration of the aircraft’s components. This will affect the aircraft’s performance in a marked way. In fact, an aircraft only has its factory advertised performance once in its life-time: at delivery.
Certain types of deterioration can be reset to zero by maintenance actions; others will not be reset completely by a visit to the maintenance shop. Let’s go through the different forms of deterioration that one normally caters for in performance calculations and how one go about to restore the aircraft’s operation as much as possible with scheduled maintenance.
Bjorn’s Corner: Production rates
By Bjorn Fehrm
20 November 2015, ©. Leeham Co: Emirates Airline CEO, Tim Clark, is quoted as having said “it takes them forever to get this thing up.” He was talking about the Airbus A350 production rate and his reasons for delaying Emirates’ decision on what to buy for the airlines medium range needs. Clark said Emirates wants more aircraft in operational use before they can evaluate the operational characteristics of the A350.
Emirates want to see at least 20 aircraft in operation and right now it is about seven to nine that fly every day. Actual deliveries stand at 10 with one month to go before the first anniversary when deliveries started (the first A350-900 was delivered to Qatar Airways on the 22 December 2014).
Looking at how many aircraft that are actually flying, one can agree with him. It seems actual production rate is more like one per month rather than the three to four a month that Airbus talked about at the first delivery ceremony.
So why is this? Is the production of A350 therefore in serious trouble? What is taking them so long? Has Emirates pointed to a weak part of the A350 program?
Bjorn’s Corner: MRJ90 first flight
By Bjorn Fehrm
13 November 2015, ©. Leeham Co: Mitsubishi flew their MRJ for the first time this week. I could have added “finally” because it is two years late compared to the original time plan. But who cares when the aircraft is finally ready to fly and everything goes well? (Well, the customers do, actually.)
It was a big moment for Japan, a nation with a sizable aeronautical industry. Japan has been a major partner to Boeing in their larger airplane programs over the 757/767 to the 777 and 787. For the Dreamliner, they even designed and made the hottest item, the high-tech Carbon Fibre Reinforced Plastic (CFRP) wing.
Despite having such a capable aeronautical industry, Japan has not built an own civil aircraft since it closed the production line for the YS-11 twin engined turboprop in 1973. Since then it has acted as sub-supplier and has worked on certain military programs like the Mitsubishi F-2 fighter, based on the Lockheed Martin F16.
The Mitsubishi corporation flew the MRJ90 for the first time Wednesday from the Nagoya Airport in Japan (screenshot from video from Mitsubishi). Most of the flight testing will be done in Moses Lake (WA), USA, where four test airplanes will be based.
Moses Lake is blessed with open skies, little air traffic, a long runway and good weather. It has a long history of flight testing, serving as a test-base for Japan Air Lines 747 pilot training for decades. Boeing also uses Moses Lake for flight testing.
We analyzed the MRJ90 and its main competitor the Embraer E175 in a subscriber article the 25th of January. We will revisit the main characteristics and then comment on what could be seen from the first flight. Read more
Bjorn’s Corner: Aircraft systems, the real nuts to crack
By Bjorn Fehrm
06 November 2015, ©. Leeham Co: COMAC’s C919 was rolled out in the week. We got to see a new shiny aircraft which looked ready to fly. The nicely curved fuselage and wings were immaculate, the paint was shiny and the CFM LEAP-1C engines were ready to go.
Yet many ask, when will it fly for the first time? It used to be that when the airframe was finished and the engines ran reliably it was time to fly. No longer! Today the most challenging part of an aircraft program is the integration of all the complex systems which hide under the skin. This is what kept the Bombardier CSeries on ground longer than it should and the Boeing 787 and Airbus A380 had the same flu (the latter also had to short wires).
It is the part of the aircraft which takes longest to get to work reliably. The A380 is known for its long period of nuisance warnings from the complex avionics system after entry into service and the reliability work for the 787 has to a large extent been one of software tuning of its system side.
As the system function of modern aircraft has grown more complex the whole architecture of how it was built had to be changed. Here’s how.
Bjorn’s Corner: Aircraft programs
By Bjorn Fehrm
30 October 2015, ©. Leeham Co: There has been dramatic news this week around Bombardier’s (BBD) CSeries program. I wrote a subscribers article about what to expect in terms of the cash flow problem that the BBD management has been wrestling with. The announcements yesterday and the following earnings call confirmed the financial modelling I did with our aircraft modelling tool.
Having watched experienced Wall Street analysts being hard pressed to understand what has happened with the CSeries, I thought I could use this week’s corner to explain the overall economical flow of an aircraft program like the CSeries (there will be details in a follow up subscriber article). I will also put it in context with how it affects a company like BBD and what one must think about when it comes to timing of such projects.
To give the timing aspect more colour, I will also compare with Embraer and their E-Jet E2 project and Boeing’s 787 program. The three programs are very different and they demonstrate in an illustrative way the challenges of making a new civil airliner and that one must adapt the project to the company’s position and its strength and weaknesses.
Bjorn’s Corner: Increasing an aircraft’s range, further considerations
By Bjorn Fehrm
23 October 2015, ©. Leeham Co: In last week’s Corner, we went through how Airbus can offer an Ultra Long Haul (ULH) aircraft to Singapore Airlines by increasing the Maximum Take-Off Weight of its A350-900, increasing the tankage and lower the payload. There are a couple of other considerations when extending the range of an aircraft that we did not touch upon. For completeness, we go through them here.
When increasing the allowed weights (really, masses) of a certified airliner, there are a few things that need to be re-evaluated and perhaps modified. First of all, the airframe needs to withstand the higher loads caused by the higher weights. Secondly, the aircraft’s field performance will be affected by higher weights. Required take-off field length must stay within usable limits, as must landing performance.
If the increase in flying weights are significant, it will also require a check on what happens to the aircraft’s flight profile when fully loaded. A heavier aircraft will cruise at lower flight levels and the One Engine Inoperative (OEI) service ceiling will diminish.
We now go through these additional areas and evaluate their impact on overall aircraft performance in general and on an A350-900ULR in particular.
Bjorn’s Corner: Increasing an aircraft’s range
By Bjorn Fehrm
16 October 2015, ©. Leeham Co: Airbus announced this week how it made an Ultra Long Haul (ULH) aircraft out of the long haul A350-900. The resulting A350-900ULR (Ultra Long Range) enables Singapore Airlines to reopen the famous direct “Flight 21” to New York.
But Singapore’s press release also talks about US West coast destinations, the first being Los Angles. They released this picture:
Reading the many comments around how an aircraft like A350-900 can reach such longer range, it can be worth going through the basics on how different parameters affect range and what Airbus or any other OEM has to consider when they want to increase the range of an existing aircraft.
We will do that from a slightly different angle than normal. We will show how a pilot would think about how he can get an aircraft with more range. Pilots reason in a different way to design engineers. They are better served by thinking on the aircraft’s range performance as endurance, meaning how many hours can we stay aloft. This works better when one plans with the prevailing weather on the route.
We will now take it step-by-step and explain which parameters matters for the pilot and which do not and how he gets his ULH aircraft. Read more