Leeham News and Analysis
There's more to real news than a news release.
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
Bjorn’s Corner: Engine rubbing
09 October 2015, ©. Leeham Co: Last week an Airbus A320neo prototype with Pratt & Whitney’s (PW) GTF had a problem while testing hot and high conditions at Al-Ain airport in Abu Dhabi. The engine suffered a rubbing problem and PW and Airbus decided to replace the engine before returning the A320neo to Toulouse.
I had the opportunity to discuss what happened with PW people at ISTAT this week and decided it makes for a good follow up to our two other engine Corners to write about what happened and how serious it was.
The problem was compressor blades rubbing against the compressors stator wall. PW knew that this engine individual could have that problem. They saw when assembling the engine it was a bit tight in the compressor area. PW said they told Airbus there was a risk with this particular unit, and sure enough, there was rubbing to be seen when they boroscope checked the engine after the test.
Here what it was all about and what to do about it. Read more
Bjorn’s Corner: Engine ratings
By Bjorn Fehrm
02 October 2015, ©. Leeham Co: After the article about the role of bypass ratio on a turbofan’s efficiency, we now look at other aspects of civil turbofan engines that are worth some light. It’s about how the engine OEMs create different versions of the same engine to cater for different aircraft variants.
The aircraft OEMs create different size variants from the same base model of aircraft by means of stretches. There is no better example of that than the Boeing 737. Over the years it has had more than 10 major versions. For the present in-service series, 737NG, there is three official variants, from the -700 to the -900ER. Originally it also had a smaller -600 variant.
These require engines from 20klbf to 27klbf. How this is achieved and what it means for engine characteristics and reliability is the focus of today’s Corner. We will also compare it to a typical long range engine, the Rolls-Royce Trent 1000/7000, which powers the Boeing 787 and Airbus A330neo.
Bjorn’s Corner: USAF Tanker program
By Bjorn Fehrm
25 September 2015, ©. Leeham Co: When Scott Hamilton asked me to give my view on his article “Pontifications: Duelling refuelling tankers” I accepted. I was not involved in the project and was only following it casually over the years.
I will also not give my view on what would have been the most suitable tanker for the US Air Force. I simply don’t have the relevant military competence for that, having never operated my fighters with aerial tanking nor been in an aerial tanker aircraft.
Where I have relevant competence is in writing military specifications for important aircraft procurements and the excerpts I have seen from the tanker RFQ on key specification points don’t impress. Let me explain.
Bjorn’s Corner: Engine efficiency
18 September 2015, ©. Leeham Co: The debate around the market’s two single aisle combatants is quite heated, with fans of the one side saying “the limited space for a high bypass engine on the 737 MAX will cripple it forever” and the other side saying “the tighter design of the 737 will make it highly competitive against the A320neo, it is the A320 which has a weight and size problem”.
One of the arguments is that each inch of engine fan diameter brings 0.5% in increased propulsive efficiency. Therefore the A320 with up to 81 inches fans will win against the 737 MAX, which has a 69 inch fan. Having all the tools to check out if this is really the truth, I fed our airplane model with all the facts and looked at the result. It’s not so easy, guys…
New single aisles on home stretch
By Bjorn Fehrm
16 Sep 2015, © Leeham Co.: Boeing released pictures yesterday of the first 737 MAX 8 being on the Renton Final Assembly Line (FAL) having completed the wing-to-body joins. With the Airbus A320neo now flying again with both Pratt & Whitney GTF and CFM LEAP test vehicles and Bombardier completing 85% on CSeries (having passed 2,400 hours of flight testing), one can say the new single aisles are on their home stretch.
737 MAX on the Final Assembly Line at Renton, Seattle. Source: Boeing.
Original planning had the CSeries entering service in December 2013, nearly two years before A320neo (October 2015) and four years before the 737 MAX (4Q2017). With the 737 MAX now on the FAL one can start to review the Entry into Service (EIS) for all three. It will be tighter than the companies have said.
Bjorn’s Corner: Production costs.
By Bjorn Fehrm
11 September 2015, © Leeham Co: In connection with our articles, there a numerous reader discussions around the development and production costs of new aircraft families. It’s not easy to understand how these costs arise, how they are booked in the OEM’s accounting and how they can be compared. Time for a primer.
I will not duplicate a course in company accounting, but it can be worth the read to understand how costs are created, accounted for and what we as externals can observe via aircraft industry economic reports .
I will focus on Airbus and Boeing. These are good examples of the different ways of collecting and showing costs in the global aircraft industry.
Bjorn’s Corner: The seating dilemma
By Bjorn Fehrm
By Bjorn Fehrm
04 September 2015, © Leeham Co: One of the hottest areas of modern airline aviation is the passenger experience and especially the seating. There are people who are specialists on the subject like Runway Girl Network; I will not try to duplicate their work here on my Corner. But I follow the subject in detail as it touches on our work of creating apples-to-apples airline comparison conditions, our Normalized cabins or LOPAs as its also called (Layout Of Passenger Amenities).
As I observe the debate on more and more cramped economy seating, I can’t but feel the whole debate is revolving around the wrong dimensions. The debate is focusing on seat width but it is a seat width which is not the primary one that affects a passenger’s comfort. Before being accused of trying to confuse with facts, let me explain.
Bjorn’s Corner: Russian aircraft industry.
By Bjorn Fehrm
22 August 2015, ©. Leeham Co: The Russian air show MAKS is taking place in Moscow, on the airfield of Zhukovsky, Southeast of Moscow. The town of Zhukovsky is called the Aero-City of the Russian federation. It houses not only a 17,800ft runway but also the center of the Russian aeronautical research and test knowledge around the gigantic airfield.
Just a couple of miles from the airfield lies the well-known Russian Central Aerohydrodynamic Institute, TsAGI. It has been involved in designing the aerodynamics of all Russian aircraft, including the latest, the Sukhoi Superjet and Irkut’s new MC-21 competitor to the Boeing 737 MAX and Airbus A320neo.
I have always been interested in the enigma of the Soviet and later Russian aeronautical industry. It had such a different structure to its western counterparts and has therefore struggled. The MC-21 is a good example. Ilyushin says they are working on MC-21, as does Yakolev and Irkut. Irkut says it is their aircraft, yet I had not heard of Irkut as a plane OEM before MC-21.
My household names for Russian airliners were Tupolev and Ilyushin with perhaps Yakolev for the smaller types. If we included Ukraine during the Soviet period, we could add Antonov as a known airliner OEM. But not Irkut. Yet today the main players doing new civil airliners are Sukhoi and Irkut, neither known for building airliners. How does this all fit together? Here is a try to sort it out. Read more