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Chengdu J-20 5th Generation Aircraft News & Discussions

Hi Gambit, please could you help me this is urgent, I really need to know where you obtained them images, ive been looking all over the internet with no luck :(, they are on page 20 of this forum and they display the flight control system, there are a few images ranging from mechanic FCS to FBW FCS.

please could you either reply on here or email me on rizzy139 at hotmail.com :)
If you are referring to page 23 of this thread, those came from a General Dynamics' training program about the F-16's FBW-FLCS back in the '80s. They were used to train engineers and technicians on the basics of flight control systems philosophy and engineering. This was before the Internet when I was still keeping records on DEC's VAX computer system. It was a small box of 35mm slides, of which the projector is a museum piece today, and contain illustrations of FLCS engineering principles to the F-16's hydraulics actuators themselves. I do not know if the material can be obtained any more. Sorry, but you are talking to an old dog here.
 
J-20 ground test on Nov.14 (1/2) - preparing


J-20 ground test on Nov.14 (2/2) - high speed texi


THX汉魂雄风和himitechworld
 
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J-20 5th Generation Fighter - Page 28
I think the J-20 has two landing parachutes instead of one like single engined J-10, so that each chute catches part of the thrust from each of the two engines.

If you only have one chute, it might deviate and catches jet exhaust from one of the two engines predominantly, making it dangerous for the plane during landing.
J-20 5th Generation Fighter - Page 28
Are drag chutes design to catch engine thrust? I thought they were just there to increase drag (therefore slowing it down).
J-20 5th Generation Fighter - Page 28
Or one could install a larger chute instead of two. I'm guessing it's easier to install with two smaller ones. Wouldn't the chute catch on fire if catching jet exhaust?
J-20 5th Generation Fighter - Page 29
I think two smaller chutes is used because of room/clearance constraint, and the fact that the chute opening is close to the engine nozzle.

Military cargo planes use one large chute, but they are larger and their engines are situated under the wings and do not interfere.

They are not designed to catch the immediate exhaust leaving the engine but I think the backwash from the engine exhaust extends for quite some distance behind the plane.

Anyway it's my pet theory so don't look too deeply into it.
J-20 5th Generation Fighter - Page 29
There could be something to it. One large chute would collapse if two stream of thrust is directed at it.
Boys, stop it. You are talking nonsense.

First...There is a difference between a 'drogue' chute, which is a subcategory of the parachute, and the parachute itself.

Drogue parachute - Wikipedia, the free encyclopedia
A drogue parachute is more elongated and has a far smaller area than a conventional parachute, and thus provides less drag. This means that a drogue parachute cannot slow an object as much as a conventional parachute, but it can be deployed at speeds at which conventional parachutes would be torn apart.[1]

The drogue parachute's simpler design allows for easier deployment. Where a conventional parachute could get caught in itself while unfolding and fail to inflate properly (thus not slowing the falling object as much as it should), the drogue parachute will inflate more easily and more reliably to generate the expected amount of drag.
A drogue chute can be easily distinguished by the fact that one can literally see through it because it has many openings to allow air pass through, that is why a drogue chute does not slow down a speeding body, like an aircraft or a race car, as much as a full parachute. This pass through feature also make the drogue chute more stable once deployed, especially for any high speed body, like an aircraft or a race car.

Second...Even though the drogue chute is more stable, that does not mean it is completely immune from being collapsed by turbulence and when it is deployed behind a moving body like an aircraft or a race car, IF it is directly behind the body, as in being inline with the centerline of said body, the aerodynamic wake created by the body can cause oscillation, which increases the odds of the oddity 'the tail wagging the dog' effect and cause a crash during the landing run. The closer the deployed drogue chute to the body, the greater the odds of oscillation.

Project Excelsior - Wikipedia, the free encyclopedia
...a multi-stage parachute system to facilitate manned tests. This consisted of a small 6 feet (2 m) stabilizer or "drogue" parachute, designed to prevent uncontrolled spinning at high altitudes, and a 28 ft (8.5 m) main parachute that deployed at a lower altitude.
The highlighted is significant in that in the skydiving environment, there is a relatively equal amount of 3D air flow around the body as it travel. The danger of the speeding body going out of control still exists. But now with a landing aircraft, especially when the aircraft is as small and quite near the ground as a fighter, the asymmetrical air flow will create differential pressures that will come into contact with the drogue chute and will increase the risk of the aircraft going out of control.

One solution is to increase the distance between the deployed drogue chute and the aircraft. Another solution is to increase the ground clearance between the deployed drogue chute and the ground, which for as small an aircraft like a fighter, this solution is not possible. The better solution is to use two drogue chutes that when deployed, each will be off the aircraft's centerline to reduce the odds of oscillation (or swaying) and turbulence induced collapse. The decision to use a single parachute or drogue chute or two drogue chutes depends on the aircraft itself and how much study was involved before the decision.

This has nothing to do with catching engine exhaust. What the heck for? :disagree:
 
J20 new photo

4QFuX.jpg


thx 蓝胖
 
J-20 5th Generation Fighter - Page 30
holy ****. i think this might be short/vertical takeoff booster like you said. the J-20 had an amazingly short takeoff distance without even engaging the afterburners.
:lol: Typical exaggeration.

No. It is the exhaust for the jet engine starter. The device is itself a turbine (jet) engine, a small one. For the F-15 and F-16, it is called the Jet Fuel Starter (JFS)...

Auxiliary power unit - Wikipedia, the free encyclopedia
The primary purpose of an aircraft APU is to provide power to start the main engines. Turbine engines must be accelerated to a high rotational speed in order to provide sufficient air compression for self-sustaining operation. Smaller jet engines are usually started by an electric motor, while larger engines are usually started by an air turbine motor. Before engines are to be turned, the APU is started, generally by a battery or hydraulic accumulator. Once the APU is running, it provides power (electric, pneumatic, or hydraulic, depending on the design) to start the aircraft's main engines.

F-15E.info: Strike Eagle reference and resources - F-15E.info - Jet Fuel Starter
The JFS has its exhaust on the bottom fuselage of the aircraft, behind the central external hardpoint (SUU-73/A pylon).
Looks like the J-20's main engine starting system is no different than the American's.

Jet Fuel Starter
MicroTurbo supplies the Noelle 180 Jet Fuel Starter Model 086 that is employed in the Mirage 2000.
But of course, since this is the J-20, gross speculations and exaggerations MUST be made. :lol:
 
The automatic control system uses the measured air speed to calculate the control surface deflection necessary. So at low air speed these deflections will be large and very visible. But it might also feel that the undercarriage is rolling over the runway and therefore desist from these deflections. This refinement has apparently not been applied perhaps because a false signal that the aircraft is on the ground would lead to the loss of the aircraft.
Correct. Stability augmentation (stabaug) uses calculated airspeed and altitude as FACTORS in creating compensatory signals to displace flight control surfaces.

Flight control system uses more than that. The basic inputs are up-down-sideway acceleration, angular rates in pitch-roll-yaw, angle-of-attack, side-slip angle, airspeed, static pressure, and position of the flight control surfaces.
Correct.

Air data computer can detect the airspeed as being in single digit, but that does not mean the FBW uses that speed as input. There's no point in making a FBW to work that far below the stall speed of the aircraft. At such slow speed, the FBW is just going to work as if the plane is flying at stall speed.
Wrong, or at best you are using improper contexts. This is not about fly-by-wire FLCS but about stabaug, whose architecture has been established long before the advent of FBW-FLCS and air data is CONTINUOUSLY computed and send to the FLCC. If air data signals falls below a certain threshold, that does not mean they are ignored but CONTINUOUSLY monitored because they are variable factors that affect flight control responses. If they change, stabaug must instantly take in those changes.

No. You miss my point! I'm saying the FBW will behave differently during takeoff, cruise flight or landing and it's the job of the pilot to set the FBW to the task at hand.

During takeoff, for example, the FBW will maintain the elevon and leading edge slat at a set fixed position since this would give a more streamline flow with uniform lift and less drag, instead of varying the positions of the control surfaces to counteract the undulating movement and mess up the airflow and increase drag considerably. Of course, during a cruise flight, one would expect the FBW to respond differently to any undulating movements caused by changing air pressure for example. (Ok, time to go to sleep.)
===
I get your point completely, and I explained it doesn't work that way. FBW has to be transparent to the pilot, and your assumption that the pilot gets to select takeoff, cruise, and landing mode violates that transparency. How the FBW behaves at different stages of flight is the responsibility of the designers, not the pilot, and the designers have to work in the confine of sensor data that is available to the FBW.
No, it does not, and this is not about FBW-FLCS but about stabaug. There are many situations where the entire FLCS changes to a preset, such as landing gear handle position or external load configuration that impose a g-limit. All of this is still transparent to pilot but in principle, the first comment is correct.
 
If you are referring to page 23 of this thread, those came from a General Dynamics' training program about the F-16's FBW-FLCS back in the '80s. They were used to train engineers and technicians on the basics of flight control systems philosophy and engineering. This was before the Internet when I was still keeping records on DEC's VAX computer system. It was a small box of 35mm slides, of which the projector is a museum piece today, and contain illustrations of FLCS engineering principles to the F-16's hydraulics actuators themselves. I do not know if the material can be obtained any more. Sorry, but you are talking to an old dog here.

Hi, ive just seen the ones you referred to and no not them, they do look like there from the 80s :), the one I am referring to is:

---------- Post added at 10:32 PM ---------- Previous post was at 10:31 PM ----------

Hi, ive just seen the ones you referred to and no not them, they do look like there from the 80s :), the one I am referring to is:

im sorry im taking up a page, i need to post a link and it wont let me until i hit 5 posts

---------- Post added at 10:33 PM ---------- Previous post was at 10:32 PM ----------

Hi, ive just seen the ones you referred to and no not them, they do look like there from the 80s :), the one I am referring to is:

---------- Post added at 10:32 PM ---------- Previous post was at 10:31 PM ----------



im sorry im taking up a page, i need to post a link and it wont let me until i hit 5 posts

apologies again
 
If you are referring to page 23 of this thread, those came from a General Dynamics' training program about the F-16's FBW-FLCS back in the '80s. They were used to train engineers and technicians on the basics of flight control systems philosophy and engineering. This was before the Internet when I was still keeping records on DEC's VAX computer system. It was a small box of 35mm slides, of which the projector is a museum piece today, and contain illustrations of FLCS engineering principles to the F-16's hydraulics actuators themselves. I do not know if the material can be obtained any more. Sorry, but you are talking to an old dog here.

Here is the link finally !

<a href="http://s1005.photobucket.com/albums/af171/Rizzler123/?action=view&amp;current=actuator.png" target="_blank"><img src="http://i1005.photobucket.com/albums/af171/Rizzler123/actuator.png" border="0" alt="Photobucket"></a>

actuator.png
 
I do apologise gambit, they were on page 20 of a different thread. (this one http://www.defence.pk/forums/china-defence/88438-j-20-successfully-conducts-first-flight-20.html)
I am trying to remember where they came from. But I do know that they do not came from what was given to me either by the USAF or from literature given to me by manufacturers or from text books I acquired a long time ago. Several of my friends became instructors, some at Embry Riddle here in the US, some went overseas working for foreign air forces, either as contractors or manufacturer tech reps, and a few became tech reps for the US Navy and assigned to carriers, and I helped some of them put together training materials for their people. These may be from materials I reviewed and critique rather than helped put together. If so, then I would not have any formal documents but rather separate items they sent me for opinions.
 
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