J-15 carrier-borne fighter thread

[jobjed]

This seems to be two new photos taken during the J-15 ground-based catapult tests. To confirm.

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. Not sure if it posted before

I don't know how you managed to miss Deino's post just above yours.

 

[Hendrik_2000]

I don't know how you managed to miss Deino's post just above yours.

Because I check the previous page and don't see it and I just glance thru the first post of the latest page

 

[Deino]

Two new images via Eastpendulum/Henry K. ... blurred but anyway !

A bit better ...

 

[Iron Man]

The way I see it is that the stress forces from the tail hook will have be transmitted to the rest of the plane to slow it down to a stop. For this reason, re enforcement of the structure of the aircraft will have to be done longitudinally along the length of the aircraft from the tail-hook to at least until the front landing gear, to transmit the braking force to the rest of the aircraft.

Re-enforcing the structure around the tail-hook of the aircraft purportedly just for aircraft recovery won't do as the stress forces will be transmitted to the rest of the aircraft and possibly breaking the aircraft apart at the mid section.

That is why, to begin with even for STOBAR, re enforcement of the aircraft structure would already have to be done along the whole length of the aircraft (to wind-stand the stress of repeated aircraft recovery) and this, in my opinion, coincide with the requirement of catapult launching.

Bear in mind the extreme stress during the recovery of the STOBAR aircraft, which has to come to a complete stop in secs. The stress on the aircraft during recovery is even greater than that during a catapult launch, so this would even exceed the limits of the latter.

For this reason, the same re enforced structure would be more than strong enough to transmit the pulling force to the whole of the aircraft during a catapult launch. Imo, the pulling force on the front wheel could be transmitted to the strongest part of the structure possibly around the area where the tail-hook is attached with the use of additional re enforcing structures/rods/bars.


Imo, solving the 2 problems in one go saves a lot time and provides the opportunity to come with the best solution for an aircraft that can do both STOBAR and CATOBAR.

Nah. It's pretty obvious that the stresses resulting from pulling on the tail are not exactly the same as the stresses that result from pulling on the nosegear. They both involve longitudinal forces acting on the airframe so it's reasonable to conclude that there would be some overlap in the reinforcement given to the J-15's fuselage, but the forces are applied in opposite directions and in different locations on the fighter, so to expect that the STOBAR J-15 needs to be reinforced or is 'naturally' reinforced for a CATOBAR takeoff is definitely not a given. Now you could claim that the PLANAF had superior foresight and designed the STOBAR J-15 to be compatible with a future CATOBAR carrier, but again, 1) there is no 'automatic' compatibility between a STOBAR J-15 and a CATOBAR J-15, 2) fighters don't add weight/reinforcement in areas they aren't anticipated to need, and of course 3) you would also have to provide evidence of the PLANAF's superior foresight in anticipating STOBAR/CATOBAR mutual compatibility and designing such compatibility into the original J-15.

 

[Quickie]

Nah. It's pretty obvious that the stresses resulting from pulling on the tail are not exactly the same as the stresses that result from pulling on the nosegear. They both involve longitudinal forces acting on the airframe so it's reasonable to conclude that there would be some overlap in the reinforcement given to the J-15's fuselage, but the forces are applied in opposite directions and in different locations on the fighter, so to expect that the STOBAR J-15 needs to be reinforced or is 'naturally' reinforced for a CATOBAR takeoff is definitely not a given. Now you could claim that the PLANAF had superior foresight and designed the STOBAR J-15 to be compatible with a future CATOBAR carrier, but again, 1) there is no 'automatic' compatibility between a STOBAR J-15 and a CATOBAR J-15, 2) fighters don't add weight/reinforcement in areas they aren't anticipated to need, and of course 3) you would also have to provide evidence of the PLANAF's superior foresight in anticipating STOBAR/CATOBAR mutual compatibility and designing such compatibility into the original J-15.

The direction of the force on the re-enforced structure and whether the stress on it is a tensile or compressive type may change depending on whether it's a recovery or a catapult action, but still the stress forces would be spread out to the whole of the aircraft through the same re-enforced structure.

We'll just have to wait to see whether the news of the CATOBAR-ready J-15 is really something factual.

 

[Iron Man]

The direction of the force on the re-enforced structure and whether the stress on it is a tensile or compressive type may change depending on whether it's a recovery or a catapult action, but still the stress forces would be spread out to the whole of the aircraft through the same re-enforced structure.

We'll just have to wait to see whether the news of the CATOBAR-ready J-15 is really something factual.

The stresses would certainly be spread out to most of the airframe, but certainly not equally. I hope you are not trying to imply this. The stress during a trap would be greatest at the rear of the aircraft and least at the front, and vice versa during a catapult takeoff.

 

[Quickie]

The stresses would certainly be spread out to most of the airframe, but certainly not equally. I hope you are not trying to imply this. The stress during a trap would be greatest at the rear of the aircraft and least at the front, and vice versa during a catapult takeoff.

The stress during a trap would be greatest at the rear of the aircraft and least at the front, and vice versa during a catapult takeoff.

That would be bad design since you would need to re-enforced both the front and rear of the aircraft which would be a lot of additional weight.

A better way is to have the pulling/pushing force of the front-wheel /tail-hook transmitted (through re-enforcing structures/bars) to the stronger part of the re-enforced aircraft structure, which should be the area around the main landing gear, and from there the pulling/pushing forces spread out to the rest of the aircraft. It is this area which experiences the greater forces during a recovery or a catapult launch.

 

[delft]

That would be bad design since you would need to re-enforced both the front and rear of the aircraft which would be a lot of additional weight.

A better way is to have the pulling/pushing force of the front-wheel /tail-hook transmitted (through re-enforcing structures/bars) to the stronger part of the re-enforced aircraft structure, which should be the area around the main landing gear, and from there the pulling/pushing forces spread out to the rest of the aircraft. It is this area which experiences the greater forces during a recovery or a catapult launch.

The tail hook pulls on the rear end to create a large acceleration. To transmit that acceleration to the part in front of the wing a moderate force is needed because only a small part of the weight of the aircraft is in front of that place. When catapulting the same aircraft the weight of the aircraft behind that same place is much larger. The accelerations are comparable so the structure at that place needs to be stronger in the aircraft that will be catapulted. In other words you need to design the aircraft for the use you are to make of it.

 

[Iron Man]

That would be bad design since you would need to re-enforced both the front and rear of the aircraft which would be a lot of additional weight.

A better way is to have the pulling/pushing force of the front-wheel /tail-hook transmitted (through re-enforcing structures/bars) to the stronger part of the re-enforced aircraft structure, which should be the area around the main landing gear, and from there the pulling/pushing forces spread out to the rest of the aircraft. It is this area which experiences the greater forces during a recovery or a catapult launch.

No, this just doesn't even remotely sound right.



Look at the bottom right inset photo. The retraction actuator of the CATOBAR J-15 is massively overbuilt compared to the STOBAR J-15. The fuselage in the area where the retraction actuator attaches to the fighter and probably also the area where the shock strut of the nose gear attaches to the fighter (red) are going to be massively reinforced as well compared to the STOBAR J-15. The nose gear is nowhere near the main landing gear (orange), to speak nothing of the tail hook (yellow).

 

[Jeff Head]

Outstanding pic and analysis.