shiv wrote:JayS wrote:
Bolded part doesn't make sense to me. One can always fly an aircraft at such combination of speed and AoA that it will maintain steady constant altitude, constant Mach flight, at low altitudes we are talking about here. If you wanna fly faster, reduce AoA. If you want to go slower, increase AoA and still produce same lift, enough to just balance the weight.
You have not understood what I am asking. It is so difficult in this medium. Let me explain.
If you take the same aircraft, same weight, same power setting and simply increase the wing area (for example by extending flaps as is done for take off) - the lift increases. The act of deploying flaps decreases wing loading by increasing wing area for the same weight
In other words - at a given airspeed the same aircraft with will generate more lift if the wing area is higher. That "more lift" will try to take the plane to a higher altitude than if that extra wing area were unavailable. Suppose you cannot retract those flaps and the wing area remains higher than a sister plane without extended flaps then the only way you can force that aircraft with lower wing loading (extended flaps) to fly low is to:
1. Slow down thereby reducing lift
or
2. Force nose down (decrease AoA) by using some aerodynamic surface
Case 1: If the plane is made to slow down it will be flying slower than its sister plane with flaps retracted at the same altitude
Case 2: If the plane is forced to fly low there is increased drag because a force is being applied to counteract the extra lift. That will burn more fuel
In the case of identical sister planes the plane with greater wing area (deployed flaps) will burn more fuel (to keep nose down and fly as fast as sister plane at low altitude) or fly more slowly to maintain the same altitude as its counterpart without extended flaps.
Kindly do not tell me that the Jag and Tejas are not sister planes with the same specs. I know that. And that is what makes the answer more difficult without data.
The questions that arise from here are as follows and I would like hard data if possible
- 1. Can the Tejas fly nap of earth at the same speeds that Jaguar achieves
2. Would the fuel consumption of the Tejas, and hence its endurance be reduced if it was flown nap of earth like Jaguar
These are the critical facts in comparing performance of the Tejas versus Jaguar in a role that the Jaguar was designed for. It's not about whether the Tejas can do it or not.
Without hard data on this everything is guesswork. That is what I said in my reply to Sachin, whose question was the very question you said must not be asked.
Since it becomes rathe academic, I think its more suitable to have further discussion here. So x-posting.
Simplified scenarios like this don't help much in problem at hand. Extending flaps, actually make it as different wing and we no longer are comparing apple to apple. But still lets go ahead.
Lets neglect case 1, since its irrelevant. We want to maintain speed. But just to note, lightly loaded wing would be more efficient in cruise, albeit at lower speed, akin to case 1 and perhaps would out-range highly loaded wing, but would take more time. Moving on.
Case 2 - Lets say we make your modified jet fly at same speed as earlier unmodified jet was flying. Assuming no change in weight, same lift needs to be generated to maintain altitude.
Same speed, same altitude >> same dynamic pressure (q). But now we have higher wing area (S).
L = q * S * C_L
Obviously now we need smaller C_L for same L. If you consider typical drag polar:
If you reduce C_L, C_D also goes down. Now whether total drag D, reduced or remains same depends on what was your initial point was on the drag polar. But its reasonable to assume initial cruise point was at max L/D (where the tangent from origin touches the drag polar) to have best efficiency. From there C_D reduces quite a bit, if you reduce C_L. And increase in S, would more likely not compensate for it. Even in worse case, overcompensation would be marginal. So worst case scenario, Case 2 has marginal higher drag, more likely, it has marginally lower drag.
D = q * S * C_D.
Note that I am not trying to make it sound like LCA will be more efficient at low level flight than Jag. IMO, its reasonable to assume that it will be less efficient. But IMO, the difference should be small and LCA should be able to maintain the required speed. Yes, that would increase fuel consumption somewhat and reduce the range of LCA. But even if LCA was equally efficient aerodynamically as Jag is, it still was never going as far as Jag due to lesser fuel fraction, as Indranil mentioned. However when we have practical situations such as flying over Tibet, LCA might out-reach Jag in low flying "effectively", as it could TO from High altitude strips, near to border, while Jag will have to TO from farther airstrips situated in plains, negating its longer range.
But I agree to you in principle when you say, we are basically comparing two different planes optimized for two different jobs. And one need not be overzealous in supporting LCA, that he undermines strengths of other planes. IAF will and should use Jags until they have them. In future, they can very well replace Jags with LCA and come up with tactics which are superior to existing tactics + Jag combination. But more likely it will be AMCA.
) and all I can see is that the pilots were very much alive and talking to the ATC much after the engines shearing off from the wings and the recovered engines showed no signed of blade out or any significant internal damage.
