k******a
发帖数: 2436 | | k******a
发帖数: 2436 | 2 Many aviation experts believe that the J-20 relies on a pair of Russian
engines or their Chinese copies. In other words, the J-20’s engines are
picked out among members of the big family uniting the Item
117, AL-31F, WS-14 and WS-10 Taihang. Two engines together develop in
between 30 and 40 tons of thrust. If that is so, then the capability of the
propulsion system
Aircraf t
is enough for supercruise, or supersonic cruise flight at military power (
highest pow- er setting without afterburning). We may also expect that the J
-20 with restricted fu- el and combat load (for instance, when fly- ing air-
to-air mission) can fly vertical with- out losing speed at subsonic regimes
and low altitudes.
When in-flight photos appeared, the J-20 became the hottest topic for dis-
cussion among aviation enthusiasts round the world. But as it appeared, the
enthu- siasts, and even world-famous western journalists, had difficulty in
classification of the new Chinese warplane. Is it a su- periority fighter?
Is it a supersonic bomb- er? Or, perhaps, it is a multirole, multimode
airplane? Even columnist and experts with world’s leading aviation
magazines hes- itated to give their clear answer to these questions, — that
in the view of them hav-
ing good sources in the US and Europe- an intelligence bodies, defense
ministries and the industry. It seems that not only jour- nalists, but the
professionals were in some state of shock after seeing the new Chi- nese
bird.
First of all, let’s determine J-20’s center of gravity position. There are
some pho- tos available of the J-20 taxiing, in which we can clearly see
its long fuselage, wing- to-fuselage connection and landing gears. The J-20
undercarriage is fighter’s clas- sics: three-point with a nose gear. And so
it makes it easy to determine center of grav- ity position. To do that we
take the main landing gear strut, and attach a line to it starting on the
wheel’s ground contact point. The line goes up with at an angle of, say, 15
degrees, leaning towards the nose of the airplane. The point where it cross
- es the fuselage center line is the most likely
position for the airplane’s center of gravity. Here comes the first
surprise: the like-
ly center of gravity position rests... too far from the mean aerodynamics
chord (MAC) of the wing. As a first iteration for aircraft designers, the
center of gravity must be somewhere 25–35% of the wing’s MAC, — like so
is prescribed in the classic aircraft design books.
But the Chinese airplane appears to have the center of gravity position some
- where at MAC’s edge. It is fairly strange for a maneuverable fighter,
since bal- ancing of the aerodynamic forces and the gravity will require
relatively high de- flection of the control surfaces — canards in the J-20
’s case. Should this airplane try to execute high-G maneuvers at subsonic
speeds, the deflection of the canards could be a limitation. All this is
rather strange for a maneuverable fighter... But not for the J-20, which
does not appear to be one of those! | k******a
发帖数: 2436 | 3 Let’s take a look at other available pho- tos, in which the J-20 goes in
for the land- ing with landing gear down. Apparent- ly, the canards are set
at a rather high pos- itive angle (leading edge upwards), while the wing has
its leading edge deflected downwards. The trailing edge surfaces are also
deflected down, at rather a small an- gle. Obviously, at the approach for
land- ing configuration, the wing’s center line
is highly curved by means of the leading and training edges down, which
increases lift (achieved through altering the camber of the wing). But not
so much as in the case of classical flaps.
All this is, again, fighter classics for the delta winged aircraft with
foreplanes. And here lies their limitation: the pilot can- not move the
trailing edge further down, since the resulting lift force that builds up on
the training edge will be hard to bal- ance with the canards, in the view
of their limited deflection scope (in the view of them stalling).
It is well known from the aviation his- tory how to enable delta-winged air-
planes to generate more of the lift force at landing. For that purpose the
canards are placed as close to the fuselage’s nose as possible, to have a
larger distance to the center of gravity. For instance, the Tu- polev Tu-144 supersonic jet liner had fore- planes that were retracted into fuselage all the time except landing. But Cheng-du designers did not do this. Rather, they positioned the canards fairly close to the center of gravity position, and thus sacrificed their effectiveness at landing for some other purposes.
What purposes? Firstly, for non-retract- able foreplanes it is important to
have them within the supersonic cone as it sets on the top of the airplane’
s nose at Mach umbers exceeding 1.0. This lead to a con- clusion what the
Chinese must have been purposely shaping the J-20 for superson- ic flying.
Why the Chinese shaped the J-20 in the way it is? Perhaps, they are unfa-
miliar with the classic solutions for a del- ta-winged, canard-equipped
fighter? No, this is not the case knowing that Chengdu’s previous design
was the J-10 light weight fighter, now in service with PLAAF. On its first
public flight, the J-20 was escorted by a J-10B twin seater, the operational
train- er version of the baseline J-10 single seat fighter. This airplane
was the star of the Air- show China 2008 and 2010, when it flew superbly
with the PLAAF display team pi- lots at the controls. The J-10 is a very ma-
neuverable airplane, and this is the testimo- ny of the Chinese designers’
skills in devel- opment of maneuverable fighter aircraft. | k******a
发帖数: 2436 | 4 The J-10 is a classic design with “prop- er” positioning of the center of
gravity, like in the books. This is clear to tell looking at the main
landing gear struts attached to the fuselage somewhere near 15–30% of the
wing’s MAC. So, let us ask ourselves the same question again, why the
Chinese designers shaped the J-20 in the way it is?
Here are some suggestions.
First, to achieve smooth airflow with de- sirable parameters at the entry to
the en- gine’s fan, the J-20’s designers have to make the air intakes
rather long. This was an important consideration at design stage.
Second, they also needed to make the air channel S-shaped, so as to hide the
fan blades from the radio waves emit- ted by enemy radars. The latter is
need- ed for a lower visibility of the airplane. It is worth to notice that
the J-20’s air intakes resemble those first tried on the Lockheed
Martin F-35 Lightning II. This gives move ground to assert that the J-20 is
optimized for supersonic regimes and supercruise, much like the F-35.
Third, let us make distribution diagram for the airplane’s cross section
along
the J-20’s fuselage centerline. We need to take account of the thickness of
the wing, canards and tailplanes. The diagram is very smooth, —
exceptionally smooth! It comes without a peak, running smooth-
ly at approximately the same height from the tops of the air intakes all the
way to the engine nozzles. | k******a
发帖数: 2436 | 5 This seems to be the main thing for the Chengdu designers. Apparently, they
wanted to make the airplane’s equiva- lent body of rotation as narrow as
possi- ble. And they needed to make provision for internal carriage of
weapons, which is a characteristic feature for fifth gener- ation fighters.
In actual fact, the J-20 has much smoother cross section distribution
diagram than the F-22A Raptor, the F-35 Lightning II and the Sukhoi T-50 (
PAK FA or FGFA). Apparently, it required quite an ef- fort from Chengdu
designers and so made them go for compromises on other things.
Should the designers from Chendgu have made it “classic”, they would not
have moved the wing all the way towards the engine nozzles. But they did
because it was the only effective way to make the air- plane as narrow as
possible, with the need for big air intakes, air-supply channels and
internal weapons bays.
Again, this is the main thing about the J-20 design, and it sets it apart
from all other known next-generation fight- ers. Other designs have “peaks
” in some 60–70% down the way from the fuselage nose tip to the engine
nozzles.
A smooth cross section distribution dia- gram is important for transonic
drag. Su- personic aircraft are being designed in accordance with so-called
“area rul- ing”. For high Mach numbers (M>2)
the distribution diagram is not so impor- tant as for transonic regimes, M=1
...1.5. It seems the Chinese designers optimized their new jet for transonic
regimes and moderate supersonic speeds.
Our impression from the J-20 is that it is an uncompromised airplane for
super- cruse, for flying at moderate supersonic speeds corresponding to Mach
M=1.3–
1.6. Such speeds can be achieved with- out afterburning. Surely, the J-20
can ac- celerate to M=2 and faster, but this would require engaging
afterburners. In turn, the fuel burn will go high, lowering oper- ational
range of the aircraft and enlarg- ing its heat signature.
In our view the Chinese designers op- timized their new jet for M=1.3–1.6. | k******a
发帖数: 2436 | 6 Here comes the clue: the J-20 is a mis- sile launching platform able to
evade en- emy interceptors by high cruise speed. The J-20 may prove a good
interceptor, — very possibly. But its main task seems to be anti-shipping:
firing missiles at enemy warships while denying their air defense cover.
It may well be that one day the new Chinese jets would be used in anger. And
it would probably be PLAAF sending their pilots to attack warships off the
coast of a freedom-loving island not far from the mainland China.
The history of the powerful US Na- vy can be traced back to the famous duel
of the USS Monitor and VSS Vir- ginia (Merrimack) on 9 March 1862, the first
-ever battle of ironclads. Although the Confederacy gunners scored hun-
dreds of direct hits, shells bounced off her armor: the Monitor seemed to
have impunity to enemy fire. The USS Moni- tor, a 987-ton armored turret
gunboat, was built at New York, with a large sin- gle cannon turret on a low
freeboard. Af- ter the battle, the North Americans constructed fifty
monitors modeled on their namesake and made them the back- bone of their
navy. For their rather strange looks, these ships were called “cheese boxes
on rafts”. Since the memorable Bat- tle of Hampton, the North Americans
nev- er lose at sea, and now their cheese box- es sale when and where they
want. China prepares a ram for them. | N****w
发帖数: 21578 | 7 呼唤摘要
And
the
duel
first
【在 k******a 的大作中提到】
: Here comes the clue: the J-20 is a mis- sile launching platform able to
: evade en- emy interceptors by high cruise speed. The J-20 may prove a good
: interceptor, — very possibly. But its main task seems to be anti-shipping:
: firing missiles at enemy warships while denying their air defense cover.
: It may well be that one day the new Chinese jets would be used in anger. And
: it would probably be PLAAF sending their pilots to attack warships off the
: coast of a freedom-loving island not far from the mainland China.
: The history of the powerful US Na- vy can be traced back to the famous duel
: of the USS Monitor and VSS Vir- ginia (Merrimack) on 9 March 1862, the first
: -ever battle of ironclads. Although the Confederacy gunners scored hun-
| k******a
发帖数: 2436 | 8 摘要是老毛子特约评论员认为j20为了m1.3-1.6优化，主要目标是对舰攻击 | h*i
发帖数: 3446 | 9 Peng
fly
【在 k******a 的大作中提到】
: Was this posted before?
| N****w
发帖数: 21578 | 10 既然能对舰攻击
那其它地面目标也能攻击没问题
对舰有啥特殊要求？
【在 k******a 的大作中提到】
: 摘要是老毛子特约评论员认为j20为了m1.3-1.6优化，主要目标是对舰攻击
| | | s****r
发帖数: 31686 | 11 既然能够对舰， 对地应该不是开玩笑的
【在 N****w 的大作中提到】
: 既然能对舰攻击
: 那其它地面目标也能攻击没问题
: 对舰有啥特殊要求？
| B*D
发帖数: 5016 | 12 四代机的目标都是压缩航母防空圈，来实现对航母进行一定程度的"防区外"的单向打击
还有就是拆系统，攻击对方加油机，预警机，电子战飞机
不过有人说土鳖对美帝正面打脸的窗口随着美帝的电弹弓，x47b，激光炮等
服役，会迅速的被关闭 ...
【在 k******a 的大作中提到】
: 摘要是老毛子特约评论员认为j20为了m1.3-1.6优化，主要目标是对舰攻击
| N****w
发帖数: 21578 | 13 电弹弓能打飞机？
怎么瞄准阿？
x47b 更打不了飞机，再入大气层那功夫，飞机早没影了
激光炮还有点谱，天气好的话
【在 B*D 的大作中提到】
: 四代机的目标都是压缩航母防空圈，来实现对航母进行一定程度的"防区外"的单向打击
: 还有就是拆系统，攻击对方加油机，预警机，电子战飞机
: 不过有人说土鳖对美帝正面打脸的窗口随着美帝的电弹弓，x47b，激光炮等
: 服役，会迅速的被关闭 ...
| d*****g
发帖数: 1616 | 14 这些新玩具，美帝服役的时候会发现土共也装备了……
【在 B*D 的大作中提到】
: 四代机的目标都是压缩航母防空圈，来实现对航母进行一定程度的"防区外"的单向打击
: 还有就是拆系统，攻击对方加油机，预警机，电子战飞机
: 不过有人说土鳖对美帝正面打脸的窗口随着美帝的电弹弓，x47b，激光炮等
: 服役，会迅速的被关闭 ...
| t*n
发帖数: 14458 | 15 隐巡战轰党
摘要是老毛子特约评论员认为j20为了m1.3-1.6优化，主要目标是对舰攻击
【在 k******a 的大作中提到】
: 摘要是老毛子特约评论员认为j20为了m1.3-1.6优化，主要目标是对舰攻击
| b****g
发帖数: 4933 | 16 hehe
【在 t*n 的大作中提到】
: 隐巡战轰党
:
: 摘要是老毛子特约评论员认为j20为了m1.3-1.6优化，主要目标是对舰攻击
| B*D
发帖数: 5016 | 17 这个太hkc了
【在 d*****g 的大作中提到】
: 这些新玩具，美帝服役的时候会发现土共也装备了……
|
|
