PLAN Carrier Strike Group and Airwing
- Thread starter Jeff Head
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Re: J-15 Carrier Multirole Fighter thread
Two things are lacking in the current discussion. First the length of Adm K was determined by the needs of the aircraft chosen to fly from her. Second if a two engine aircraft would be lost if the critical engine fails at the critical time it is prudent to go to a single engine aircraft. This was known at the start of the project. Before the first steel was cut for the ship simulations must have been run with the aircraft and engine characteristics determined as well as possible to determine the optimal ski ramp profile and the places of the starting positions for the aircraft considered at the store and fuel loads considered at relevant winds over deck without and with engine failure. After an engine failure at the moment the ship retracts the wheel blocks the aircraft accelerates at a reduced rate to achieve about two third of the speed it would have without engine failure, it will drop its external stores immediately after leaving the ski ramp and flies at a reduced angle of attack, that is in a curved flight in order to continue accelerating, flying a profile that will not end in the water.
It would be decidedly odd if the aircraft chosen would only be able to take off with a very reduced weight. This should already be enough to decide that the numbers given by Fomin are at least reasonable.
Two things are lacking in the current discussion. First the length of Adm K was determined by the needs of the aircraft chosen to fly from her. Second if a two engine aircraft would be lost if the critical engine fails at the critical time it is prudent to go to a single engine aircraft. This was known at the start of the project. Before the first steel was cut for the ship simulations must have been run with the aircraft and engine characteristics determined as well as possible to determine the optimal ski ramp profile and the places of the starting positions for the aircraft considered at the store and fuel loads considered at relevant winds over deck without and with engine failure. After an engine failure at the moment the ship retracts the wheel blocks the aircraft accelerates at a reduced rate to achieve about two third of the speed it would have without engine failure, it will drop its external stores immediately after leaving the ski ramp and flies at a reduced angle of attack, that is in a curved flight in order to continue accelerating, flying a profile that will not end in the water.
It would be decidedly odd if the aircraft chosen would only be able to take off with a very reduced weight. This should already be enough to decide that the numbers given by Fomin are at least reasonable.
thunderchief
Senior Member
Re: J-15 Carrier Multirole Fighter thread
That is why you have cos(angle) part . Basically , we are calculating distance plane would go before it starts descending . Best results are for 45 degrees , but this is a very rough first order calculation . For a better results you would need integral calculus , incorporating increase of speed . And then you would need to incorporate all forces acting on the plane , height of the ramp etc ...
For a 14 degrees you would get 73.9m "deck extension" and 232.5 km/h speed
That is why you have cos(angle) part . Basically , we are calculating distance plane would go before it starts descending . Best results are for 45 degrees , but this is a very rough first order calculation . For a better results you would need integral calculus , incorporating increase of speed . And then you would need to incorporate all forces acting on the plane , height of the ramp etc ...
For a 14 degrees you would get 73.9m "deck extension" and 232.5 km/h speed
Intrepid
Major
Re: J-15 Carrier Multirole Fighter thread
If an aircraft can take off without assistance, it can even better* take off using assistance
*better:
shorter distance and/or
more payload and/or
safer speed and/or
guided path in low visibility and/or
less stress to undercarriage due to a plain path
Any assistance is a plus in energy for the short moment of high acceleration. For a patrol aircraft an assisted take off means lighter engines and more range.
If an aircraft can take off without assistance, it can even better* take off using assistance
*better:
shorter distance and/or
more payload and/or
safer speed and/or
guided path in low visibility and/or
less stress to undercarriage due to a plain path
Any assistance is a plus in energy for the short moment of high acceleration. For a patrol aircraft an assisted take off means lighter engines and more range.
Re: J-15 Carrier Multirole Fighter thread
That's correct, and in simple English, as a figure of speech, it is important to note that not only is airspeed off the ramp important, a more important factor is rate of acceleration and thrust. Were it not for the J-15s tremendous thrust to weight ratio, this aircraft, at this weight would NOT be operating of the Liaoning or any other Stobar carrier. This aircraft will "always" depart or recover from this aircraft carrier while the ship is steaming at 20+ knots into the prevailing wind. On a combat air patrol, you will launch and climb to altitude initially and once there pull the throttles back to a very efficient power setting to "loiter" on the threat vector, factor in sufficient fuel for a 10 to 20 minute engagement, and return from altitude, to the ship with a "reserve" in case of a bolter or weather.
This discussion isn't nearly as nebulous as some would make it out, the J-15 will have very similar numbers to our own F-15 or even more accurately the Su-27 and her variants, because that gentlemen is what she is, a very lovely, sweet little Flanker, she is not large, she is lovely and very well proportioned, and 90% of the time, there is no need to launch her at MTOW, NADA/NONE!
That's correct, and in simple English, as a figure of speech, it is important to note that not only is airspeed off the ramp important, a more important factor is rate of acceleration and thrust. Were it not for the J-15s tremendous thrust to weight ratio, this aircraft, at this weight would NOT be operating of the Liaoning or any other Stobar carrier. This aircraft will "always" depart or recover from this aircraft carrier while the ship is steaming at 20+ knots into the prevailing wind. On a combat air patrol, you will launch and climb to altitude initially and once there pull the throttles back to a very efficient power setting to "loiter" on the threat vector, factor in sufficient fuel for a 10 to 20 minute engagement, and return from altitude, to the ship with a "reserve" in case of a bolter or weather.
This discussion isn't nearly as nebulous as some would make it out, the J-15 will have very similar numbers to our own F-15 or even more accurately the Su-27 and her variants, because that gentlemen is what she is, a very lovely, sweet little Flanker, she is not large, she is lovely and very well proportioned, and 90% of the time, there is no need to launch her at MTOW, NADA/NONE!
Re: J-15 Carrier Multirole Fighter thread
J-15 similarly have access to newer designed engines. In addition to WS-10 variants, Saylut apparently already have contract to supply Al-31 FN Series 3 (137kN compared to 125kN engine used in Su-33) to China.
J-15 similarly have access to newer designed engines. In addition to WS-10 variants, Saylut apparently already have contract to supply Al-31 FN Series 3 (137kN compared to 125kN engine used in Su-33) to China.
Engineer
Major
Re: J-15 Carrier Multirole Fighter thread
And I am telling you it doesn't work that way. Increasing the ramp angle for more upward velocity means reduction in forward velocity. Since lift is a function of airspeed, reduction in forward velocity means a reduction in lift generated, canceling the additional upward velocity. You cannot get extra benefit out of nothing.
Re: J-15 Carrier Multirole Fighter thread
But what you do get is time. Time for the engines to power the aircraft to enough air speed to generate the lift necessary to sustain flight before gravity overcomes the additional "upward" velocity imparted by the ramp. Then the wings take over.
Re: J-15 Carrier Multirole Fighter thread
What you get with a ramp is reduction in induced drag as the plane runs down and leave the deck, and thus giving the plane faster horizontal acceleration, and better margin of speed and safety.
When a plane runs down a flat deck it needs vertical velocity. To gain this it must rotate to increase the angle of attack of the wings. This increases lift from the wings and gives the plane the extra lift needed to gain vertical velocity. But increased angle of attack increases lift induced drag on the wings. As a result, it reduces the plane's forward acceleration.
When a plane runs off the end of the ramp the ramp imparts a vertical velocity. Even though the aircraft appears to be pitched up its relative angle of attack to ambient airstream remains low. As a result, the plane runs down the deck, up the ramp and then off the ramp in an attitude with low induced drag, and this increases its ability to sustain forward acceleration.
What you get with a ramp is reduction in induced drag as the plane runs down and leave the deck, and thus giving the plane faster horizontal acceleration, and better margin of speed and safety.
When a plane runs down a flat deck it needs vertical velocity. To gain this it must rotate to increase the angle of attack of the wings. This increases lift from the wings and gives the plane the extra lift needed to gain vertical velocity. But increased angle of attack increases lift induced drag on the wings. As a result, it reduces the plane's forward acceleration.
When a plane runs off the end of the ramp the ramp imparts a vertical velocity. Even though the aircraft appears to be pitched up its relative angle of attack to ambient airstream remains low. As a result, the plane runs down the deck, up the ramp and then off the ramp in an attitude with low induced drag, and this increases its ability to sustain forward acceleration.
Re: J-15 Carrier Multirole Fighter thread
Uh...which is exactly what I said.
Jeff Head said: