Leeham News and Analysis
There's more to real news than a news release.
Leeham News and Analysis
- Airbus sees Boeing as medium-term competitor, with Comac next June 14, 2025
- Boeing bullish on 20-year forecast, despite short-term headwinds June 14, 2025
- Embraer’s 20-year market forecast under 150 seats: fewer turboprops, jets about the same June 14, 2025
- Airbus Canada CEO: Airbus is here to stay in Canada June 14, 2025
- Little known, most unknown in Air India 171 crash June 13, 2025
Bjorn’s Corner: Flight control, Part 4
By Bjorn Fehrm
1 April 2016, ©. Leeham Co: Last week we described the computer augmented flight controls that are possible with Fly-By-Wire (FBW) systems. We described the most common flight control laws by discussing the two most common control law implementations in the market, the Airbus and the Boeing ones.
Today we will finish the series by discussing how an autopilot, or as the OEMs call it, an Autoflight or Automatic flight system, is added to the aircraft’s control system. An autopilot is most of the time combined with a flight director and a Flight Management System (FMS).
We will mention how these fit in the picture but focus on the autopilot, once again to keep it simple and avoid trying to cover too much. The autopilot subject is large enough. Read more
Bjorn’s Corner: Flight control, Part 3
By Bjorn Fehrm
25 March 2016, ©. Leeham Co: Last week we covered the natural stability of commercial aircraft and the most important movements the aircraft would go into if we had no pilot intervention.
Now we will cover how Fly-By-Wire (FBW) systems make enhanced flight control laws practical to implement. We will cover the principal build up of a FBW system with enhanced control laws and two of the most common approaches used in the market for such control laws: the Airbus and the Boeing implementations.
The discussion will focus on the essential and forgo many deeper discussions over redundancy and safety. Otherwise the subject expands into a book rather than an easy to read article and that is not what we want.
Bjorn’s Corner: Flight control, Part 2
By Bjorn Fehrm
18 March 2016, ©. Leeham Co: Last week we covered the early days of flight control when the pilot controlled the aircraft’s movable surfaces (called movables; e.g. stabilator, rudder, ailerons, spoilers…) without the involvement of computers.
We will now continue with more advanced control systems, all based on the electrical signalling of the intentions of the pilot to the movables. As the modern Fly-By-Wire (FBW) control systems modify the aircraft’s basic flying behaviour, we need to start with understanding what that behaviour is. Then we can understand how different FBW systems go about modifying these characteristics.
One could think that an aircraft is made to fly nice and stable, should the pilot take a few seconds and admire the view. Nothing could be further from reality. All normally stable aircraft which do not employ flight computers or autopilots to enhance the normal stability would go into a rather nasty dive after a while.
Why this is so and what is done to help the pilot in modern FBW systems is the subject of today’s and next week’s Corner.
Bjorn’s Corner: Flight control
By Bjorn Fehrm
11 March 2016, ©. Leeham Co: We covered a bit on flight testing some Corners ago and the fact that test pilots like to fly in direct Fly-By-Wire mode for initial evaluation of the aircraft. There’s a lot to say about how an aircraft is controlled. I have experienced the significant shift from mechanical flight controls to Fly-By-Wire (FBW).
For the pilot, things haven’t changed that much for normal flying with the introduction of FBW, but for the aircraft manufacturer it’s a dramatic change. It changes the way how one works to get an aircraft to fly nicely within its whole speed and altitude register (called the aircrafts flight envelope).
We will cover the reasons for the changeover to FBW for commercial aircraft and what this enables in a couple of Corners. We will start with how the classical mechanical flight control gradually got itself into more and more complication and how this was solved with FBW.
In a subsequent Corner, we will look at how FBW enable us to fly the aircraft differently. We can with the help of FBW implement more sophisticated flight control laws, aimed at helping the pilot to a safer flight.
Bjorn’s Corner: Engine architectures
4 March 2016, ©. Leeham Co: There is a saying, “There’s more than one way to skin a cat.” The same goes for making successful Turbofans to commercial aircraft.
At the recent Pacific Northwest Aerospace Alliance 2016 sub-supplier conference in Seattle, GE, Rolls-Royce and Pratt & Whitney all talked about their latest engine projects and the technology development that was critical to their success.
The engines they talked about, the GE9x, Rolls-Royce Advance and Pratt & Whitney’s Geared Turbofan, can all be characterised as the best of breed for their intended use but they could not be more different in how their level of excellence is achieved.
It made for interesting listening. Here’s the gist of what was told.
Bjorn’s Corner: Flight tests
By Bjorn Fehrm
19 February 2016, ©. Leeham Co: Last week I described how Mitsubishi Aircraft Corporation (MAC) issued a press release on Christmas day communicating MAC would be doing structural reinforcements on their test airframes before continuing flight testing. MAC was perhaps overzealous when informing the world that they would do minor reinforcements to two ribs and a few stub spars in order to pass Ultimate strength tests for the aircraft.
I rightfully thought this is the Japanese culture at play; there must not be a big problem behind it.
There was one more area of that press release that intrigued me. Here what it said: “The first flight and the subsequent flight tests have confirmed the basic characteristics to be satisfactory. However, we also have recognized several issues as we attempt to accelerate our development.”
Time to decrypt this as well and compare to what has become standard industry practice.
Bjorn’s Corner: Communicate or not?
By Bjorn Fehrm
19 February 2016, ©. Leeham Co: Mitsubishi Aircraft Corporation (MAC) announced on Christmas Day that they delayed the entry into service of the MRJ90 regional airliner by over a year. At the same time, they also announced that they had to reinforce the aircraft’s wing and fuselage.
The market’s reaction to the news was with disappointment. A further delay to a new aircraft from a new player in the market was not good news, but it was not that surprising. Bringing new aircraft to market on time is tough for the established players. Other new entrants, COMAC/AVIC and Irkut, are also running late with their programs, and Sukhoi was late with its SSJ100.
What worried many more was that the aircraft needed reinforcements, directly after its first flights. After only three flights, the aircraft was grounded and was scheduled for changes to its airframe. That was really bad news. “It’s going to be heavier.” How could MAC miss to gravely was the common reaction.
Having worked in a 50% Japanese company for many years, I wondered what was behind this all. Was the aircraft really in dire straits or did we witeness a cultural mismatch I’ve seen many times?
Bjorn’s Corner: Efficient systems, Part 2
By Bjorn Fehrm
12 February 2016, ©. Leeham Co: Last week we looked at what could be done to the aircraft’s systems to increase the aircraft’s efficiency. But it does not stop with systems which can improve the aircrafts internal efficiency. Modern avionics and flight procedures can improve the efficiency of an airliner’s flight operation.
Ever since the Second World War, the navigation of civil airliners has been done by flying straight leg routes with the help of special ground-based radio beacons. The most elementary of these is the Non-Directional Beacon, NDB. It requires the pilot to read bearings to the beacon and is difficult to use.
A directional beacon called VOR, that went operational after WW2, changed the way that airliners could navigate (over large un-inhabited areas like the Atlantic or the Oceans, different low precision wide area navigation systems were used like LORAN). While the VOR was a big step forward, it still required navigation in straight leg routes between VORs, and this was not 100% efficient.
The development of powerful navigation computers (FMS) and the use of GPS is now changing this.
Bjorn’s Corner: Efficient systems
By Bjorn Fehrm
05 February 2016, © Leeham Co: In recent Corners, we looked into technologies which have made the new breed of airliners more efficient.
We’ve talked about how new engines can raise efficiency by about 15% and how aerodynamic improvements, like more efficient split winglets, can add another 1%-2% over single blade winglets. We have also looked into modern ways to manufacture the more resilient and lighter composites structures that designers want to use to increase aircraft efficiency.
There is one area which we have not covered: the aircraft’s systems and how these can be made more efficient. An improved system architecture can add the efficiency improvement of a split winglet. So let’s have a look at the trends in aircraft systems.
We start this week with power distribution.
Bjorn’s Corner: Exciting 2016
By Bjorn Fehrm
29 January 2016, ©. Leeham Co: In the corner of two weeks ago we did a retrospective of 2015. Time for looking ahead. The year of 2016 will be quite interesting. We had entry into service of the first re-engine single aisle aircraft this week, the Airbus A320neo, the same week as we expect first flight from its main competitor, Boeing’s 737 MAX 8. We will also see first flight of the Embraer E190E2 and A350-1000 before the year is over.
The Mitsubishi MRJ shall go test flying in earnest and Bombardier’s CSeries 100 and 300 shall enter service. On top of that, the COMAC 919 will probably start ground roll tests this year and we should see roll out of Irkut’s MC-21. I would say 2016 is a busy year for civil aviation.
In the 2015 corner we talked a lot about engine technology as a key driver to further efficiency of air transportation. Now will dissect the airframe technology that all these new projects will bring us. Read more