Cain Marko wrote:Rahul, what other factors would be so critical if the issue was take off with meaningful loads? wingloading, lift/drag ratio? Perhaps Kartik/Shiv/Vina can shed some light here. Even so, the fulcrum is known to generate as much as 40% of lift via the body thanks to the LERX so wingloading is not as much an issue with this design. For that matter the teens and the Rafale too utilize a lifting body design although I doubt the teens would make it thanks to relatively poor TWR.
As an aside, let us not prematurely rejoice about the LCA making it in light of this MRCA failure. We simply don't have enough info IIRC re. what config the LCA flew with from Leh and at what configuration the MRCAs failed to do so. IOWs, what was the LCA/MRCA weight at take off? 50% of MTOW? MTOW?
well lift is the critical issue here since the Leh airfield is situated 10,600 ft ASL.
Aircraft with lifting body fuselages (like the MiG-29) where the fuselage also generates quite a bit of lift along with the wings, are at an obvious advantage here. With the density of air being so much lesser than at sea level, any aircraft struggles to take off at what would be its regular take-off speed simply because they're not generating enough lift to be able to get them off the ground (since lift is directly proportional to the density of air).
So since you're not generating lift easily you need to have higher speed, which makes it quite difficult to descend into this airbase as well..first of all mountains surround it, which means that its quite a steep approach and high landing speeds, all of which test a pilot's skill. generally only delta wing aircraft were supposed to have higher landing speeds which meant higher brake wear but at Leh I'm pretty sure that if a flight is permanently based there they'll wear out their brakes fast as well.
The LCA video at Leh is really illuminating. The LCA was carrying 2x 1200 ltr drop tanks and 2 R-73 dummies so its a standard air-defence configuration. It has taken off in the same config in around 400-500 meters at Bangalore and yet at Leh it just kept going on and on and must have taken easily 1200 meters or more to rotate (not a scientific guess ok so don't jump on me) and even after that its labouring to really attain altitude. That is what happens when you have low density air.
see this video at the 7:52 mark
and compare it with the earlier take-offs shown from Bangalore airport.
Then again, the LCA is an aircraft that has a very large wing surface area compared to its size, so it generates quite a bit of lift (again lift is also directly proportional to surface area of lifting body) so it still did well at Leh and met the parameters set for it.
But, here are the details of the LCA's Leh test- and we could guess that similar tests were conducted on the MRCA candidates.
- 4 take-offs and landings (Tejas performed energetically it seems)
- These included early morning start ups after overnight cold soaks. The LCAs were parked overnight in open blast pens with temperatures going down to -20 deg C.
- All systems performed flawlessly the next morning, although the startup as expected, was a bit laboured, but all other systems were unaffected by the extreme conditions and cold soak
- This despite the fact that the LCA had issues with its fuel system at the time of the Leh trials.
So we cannot really comment on who failed and how they failed since we don't really know what were the parameters set- for instance did the IAF want them to rotate at a particular distance (take off distance from stand still), while carrying drop tanks and some air-to-air missiles/bombs or all of the above ?
If they didn't meet that mark, it doesn't mean that they're useless at high altitude bases. I'm pretty sure that all of the MRCA candidates can be based at Leh with suitable modifications if any systems are having difficulties at that altitude. Of course some will be better than the others and its upto the IAF to judge how important it feels the Leh leg of the trials are and what weightage it gives to them in its report. Probably the easiest thing would be build climate controlled concrete blast pens for the aircraft. Its never good to expose them to the elements unless you want to face issues unexpectedly down the line.
My guess is that the MiG-35 wouldn't have had any issues with taking off with a meaningful load given that although its heavier than the IAF's MiG-29s, its still got a lifting body fuselage and its engines generate a bit more thrust as well and have FADEC too..it may be a different story regarding the cold soak and avionics and fuel systems having to work perfectly well when exposed to cold overnight, but I'm just guessing.
I don't think that the Rafale or the Typhoon would've had problems taking off with a meaningful load either since both have good T/W ratios and a low wing loading factor. However, the cold soak may have been a bug-bear.
OTOH, the F/A-18 is used by countries like Canada and Finland, which are extremely cold in winter..however they don't leave them out in the cold..this from something I read about Norwegian F-16s and how quickly they need to be brought into climate controlled hangars (they face even worse weather conditions than those at Leh with sudden snow, sleet and extremely poor visibility all being quite normal)
My guess is that the F-16 Block 60 might have had issues in both taking off with a meaningful fuel and weapons load and with its avionics and fuel systems starting up after a cold soak since this is definitely not standard practice for even Nordic operators of the F-16 based on their operational experience with the F-16s. I'm guessing about the load since its wing loading is worse than earlier blocks what with the added weight of new systems.