Plane C919 launches regular flights

chiny24.com 1 year ago

On 4 August, the first 2 Chinese C919 aircraft began flights on the Shanghai-Chengdu route

On Friday, August 4, the first 2 copies of Chinese passenger aircraft C919 began regular service of Shanghai – Chengdu (the capital of Sichuan state in southwest China) for China east Airlines. It is another milestone in the continuous improvement of commercial aircraft operations C919.

Every Monday, Wednesday, Friday and Sunday there will be 4 flights on that airline with these aircraft, and on the remaining days 2, the China Media Group announced on Friday.

According to the Xinhua information agency, the launch of commercial routes is intended to gather more operational data and experience for C919 machines, contributing to the further improvement of advanced quality aircraft developed in the country.

The first C919, which piloted this route, made 125 commercial flights with a full service time of over 360 hours, carrying over 15,000 passengers. The second C919 aircraft was officially delivered to China east Airlines on 16 July.

How much does COMAC C919 cost?

Although COMAC does not print the authoritative catalog price, it is estimated that the aircraft could cost between $90 and $100 million. specified a price level seems rather competitive, given the price of an Airbus 320neo of $111 million, or a Boeing 737 max 8, which costs $112 million. The attractiveness of Chinese offer increases lower operating costs and advanced construction. COMAC is simply a company that is just gaining this section of the market. Therefore, the issue of the future is an additional origin affecting the popularity of the aircraft, which is its inability to operate.

Can C919 be considered a made in China aircraft?

According to Chen Yingchun, deputy chief designer, COMAC owns patent C919. Key processes, specified as design, final assembly, test flights and sales, were conducted by COMAC. China independently designed and tested aerodynamic configuration, as well as overseeing aircraft design, performance tests, component production and strategy integration.

The COMAC's own plan is the wings of C919. Wings are not only the main supporting elements of the full structure, but besides the most hard components to produce. Thanks to the recently developed Chinese overcritical lobe technology, C919 maintains performance levels even at 2 meters bent in static test (look at the static tests C919 and Airbus 350).

Fuel consumption by large passenger aircraft is huge. To accomplish fuel saving, supercritical lobe technology has been used, expanding aerodynamic performance by 20 percent and reducing opposition by 8 percent (!!!).

The supercritical lobe utilized in the C919 model was developed by Aviation manufacture corp of China (AICC).

Let's explain: what is simply a supercritical lobe

(source: https://michaelsoroka.com/2014/0829/flying-the-supercritical-wing-an-up-close-look-at-the-supercritical-airfoil-and-high-speed-flight/)

Some history.

During the early tests of supersonic flight in the 1940s and 1950s, it became clear that flying in the supersonic government poses serious engineering problems. It was rapidly noted that as the plane approaches and exceeds the velocity of sound, many bad things begin to happen. 2 of the most noticeable effects are the sharp increase in opposition due to the formation of the shock wave and the shifting of the centre of the carrier force generated by the wing backwards.

These challenges were yet reduced in military supersonic aircraft projects, but transport category aircraft were orphaned with wing designs from the time of Wilbur and Orville.

In the early 1970s, erstwhile request for cheap, economical and fast air travel increased, investigation began on a fresh wing kind that would work more efficiently at speeds close to supersounds. This yet led to the improvement of a supercritical wing.

The modern supercritical wing was first flown on a modified F-8 Crusader during NASA's investigation task in the early 1970s. Since then, adaptation of supercritical wing technology has been built into almost all category of transport aircraft. Canadair and Lear were among the first aircraft manufacturers to usage the supercritical wing in a commercial aircraft, and most likely that's why the supercritical wing in the CRJ series aircraft is more visible than in another transport category aircraft.

What is supercritical wing and how does it work?

When the air flow around the plane exceeds the velocity of sound, shock waves are generated. These shock waves, in addition to another adverse things, greatly increase the aircraft's resistance. Since the increased opposition caused by the supersonic flow around the aircraft is so significant, the aircraft's engines must produce a much larger thrust to push the air through with shock waves. This results in much more fuel burning at a reasonably tiny increase in speed.

As a result, oversonic passenger travel is highly costly due to the immense amount of fuel that supersonic aircraft must burn to penetrate the impact wave (sound barrier). This phenomenon was the main origin of Concorde’s economical collapse and is the reason why all modern passenger aircraft fly at a velocity lower than sound speed.

Although shock waves begin to form erstwhile the air flow around the aircraft reaches the velocity of sound, this does not mean that flying at a velocity just below the velocity of sound will defend the aircraft from the shock wave. Reason?

Some parts of the aircraft, in peculiar wings, are shaped to make the air flowing faster. This means that the aircraft can actually fly at a velocity well below sound speed, but it has localised areas where airflow is actually supersonic and generates adverse shock waves that affect the fast increase in fuel consumption.

The advanced surface of the conventional lobe wing (non-supercritical wing) is rounded. This helps to drag the air flowing above the advanced surface of the wing down, generating additional load-bearing force. Unfortunately, the rounded advanced surface of the conventional lobe besides greatly accelerates the air above it, as does Venturi's venturi. This means that the airflow over the top of the conventional lobe will scope supersonic velocity long before the aircraft reaches sound speed.

Thus, to counter this and hold the formation of the shock wave, the supercritical wing uses a more flat advanced surface and a more curved tail section. The more flat advanced surface of the supercritical wing does not accelerate the air as much as the rounded conventional lobe. This allows the aircraft to fly faster without supersonic flow over the advanced wing. The flattened advanced surface of the supercritical wing causes little load-bearing force than the conventional rounded lobe. To compensate for this, the supercritical wing uses a specially designed tail section to recover the load-bearing force lost by the flattened advanced surface.

The consequence is simply a lobe that inactive retains decent performance at low speeds, while at the same time gaining the ability to fly at speeds closer to the velocity of sound without generating large shock waves.

According to NASA, supercritical wings reduce fuel consumption at transsonic speeds by about 15%. The supercritical wing technology besides increased the velocity that the aircraft can effectively fly from about 0,70 sound velocity in the conventional wing to over 0,84 sound velocity in the supercritical wing. Which means you can get where you want, much faster and theoretically pay little for the ticket. Theoretically...

In 1974, NASA calculated that air carriers around the planet could save a full of about half a billion dollars on fuel by turning this technology on. This is almost $2.4 billion in terms of today's dollars, but then, according to the Canadian Department of Transportation, there were only around 4,500 passenger aircraft in the world, and Boeing estimated a global passenger aircraft fleet by the end of 2012 to be somewhat over 20,000 aircraft.

"NASA's work on sound barrier management has provided a fundamental knowing of transsonic and supersonic aerodynamics, which has enabled the improvement of the aircraft we are flying today"— says Robert Gregg, Chief Aerodynamics of Boeing Commercial Airplanes based in Renton, Washington. He notes that in 2012, US carriers made it possible for 734 million passengers to travel, and in 2008, goods worth $1.6 trillion were transported by air, adding, "Without NASA's work it would not be possible."

He adds that whatever is saved on fuel will besides be saved on carbon dioxide and another greenhouse gas emissions."

Source: https://spinoff.nasa.gov/Spinoff2015/t_2.html

Developing the optimal wing profile of the aircraft is not everything

A key technological feature in aircraft wings production – the shelling of large integral wings panels – has long been a abroad monopoly that has limited the improvement of large aircraft in China. After many studies and systematic experiments, the AICC yet mastered supercritical lobe technology and applied for a patent. Thus the abroad monopoly was bypassed and the company became 1 of the fewer in the planet with intellectual rights to this technology.

Another major accomplishment was the improvement and application of the spherical windshield of an airplane made of quartz glass. This is another origin reducing aerodynamic opposition and hence operating costs.

The COMAC itself does not presently supply detailed information on this issue.

This embodies the nature of technological investigation active in the improvement of C919. Western countries proceed to lead the improvement of large passenger aircraft and are veterans on the global marketplace while China is inactive facing method obstacles. COMAC focused on the improvement of 102 key technologies during C919 production, not only reaching a breakthrough in fresh materials, modern production and advanced power, but besides promoting the improvement of mechanics, computational mathematics and another key areas in China.