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Thread: What is up with the F-35? Part II

  1. #31
    Patron Phoenix10's Avatar
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    I'm sure most have now seen this. More details on the F-35 kinematic performance:

    F-35 Tests Proceed, Revealing F/A-18-Like Performance - Defense News

    "Operational pilots should be thrilled with the F-35's performance, Kelly said. The F-35 Energy-Management diagrams, which display an aircraft's energy and maneuvering performance within its airspeed range and for different load factors, are similar to the F/A-18 but the F-35 offers better acceleration at certain points of the flight envelope.

    The E-M diagrams are very similar between the F-35B, F-35C and the F/A-18. There are some subtle differences in maximum turn rates and some slight differences in where corner airspeeds are exactly."

    And previously from John Beesley:

    New Fighter Jet: Controversial Future of the U.S. Fleet | LiveScience

    "In the subsonic flight regime, the F-35 very nearly matches the performance of its' larger, more powerful cousin, the F-22 Raptor, Beesley explained. The "subsonic acceleration is about as good as a clean Block 50 F-16 or a Raptor- which is about as good as you can get."

    "What Beesley expects will surprise future F-35 pilots is the jets' superb low speed handling characteristics and post-stall manoeuvrability."

    Since the F-35 has primarily been put through its paces at lower speeds we don't yet know the details of the high speed regime. Let's assume for the sake of argument that it meets its design goal of "meets or exceeds the F-16". If that is the case, we are looking at an aircraft with the high speed turning performance of an F-16 (or better), the low-speed, nose pointing ability of an F-18 (or better), acceleration better than both, carrying internal weapons, with 5th Gen avionics and VLO, carrying AIM-120D and AIM-9X. That sounds like a very potent BVR and WVR aircraft. As a US taxpayer, these reports sounds very promising. I would think that any Air Force would be happy to have such an aircraft. Now if only they can keep the price down....
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  2. #32
    Senior Contributor surfgun's Avatar
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    Nice to hear some good news.

  3. #33
    Military Professional wabpilot's Avatar
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    The main thing I am hearing right now from Pax River is the engines are developing more than specified power. Not entirely a bad thing, but not entirely a good thing either. The C is within 1% of the range spec, a manageable number. Once we tame the power output, we should probably hit the numbers. The B has some other issues. Engine temperatures are a bigger problem with the B. We are melting asphalt on the ramp at Pax River. If the deck coatings are not more heat resistant than the very worn coating at Pax River, we may be in trouble.

  4. #34
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    Quote Originally Posted by wabpilot View Post
    The main thing I am hearing right now from Pax River is the engines are developing more than specified power. Not entirely a bad thing, but not entirely a good thing either. The C is within 1% of the range spec, a manageable number. Once we tame the power output, we should probably hit the numbers. The B has some other issues. Engine temperatures are a bigger problem with the B. We are melting asphalt on the ramp at Pax River. If the deck coatings are not more heat resistant than the very worn coating at Pax River, we may be in trouble.
    Why is this necessary to develop a VTOL plane? By looking at the costs of the feature involved, we would have been better off by building more Charles de Gaulle style ships for the Marines. Those ships would have catapults and we would have spend a lot less than $1 trillion dollars.

  5. #35
    Senior Contributor Stitch's Avatar
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    That's always been a problem with modern VTOL aircraft; I know the Yak-141 wasn't allowed to land in the VTOL configuration at Farnborough in 1993 for fear it would blow a hole in the tarmac due to the eflux from the massive Kobchenko/Soyuz R-79 engine.
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  6. #36
    Senior Contributor surfgun's Avatar
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    They may as well develop an angled flight deck for the America Class LHA's and fit a catapult.

  7. #37
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    Quote Originally Posted by surfgun View Post
    They may as well develop an angled flight deck for the America Class LHA's and fit a catapult.
    Not easily done. You have to include hangars and elevators and stuff. You need Charles de Gaulle style ships if you don't want super carriers.

  8. #38
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    Quote Originally Posted by wabpilot View Post
    The main thing I am hearing right now from Pax River is the engines are developing more than specified power. Not entirely a bad thing, but not entirely a good thing either. The C is within 1% of the range spec, a manageable number. Once we tame the power output, we should probably hit the numbers. The B has some other issues. Engine temperatures are a bigger problem with the B. We are melting asphalt on the ramp at Pax River. If the deck coatings are not more heat resistant than the very worn coating at Pax River, we may be in trouble.
    The engine temps on the B have always been more of an issue, because they have to run it hotter to get the thrust.

    The range spec isn't a problem, combination of weight and tuning. These engines have always developed more than their advertised power- remember an F-119 hovered a 34,000lb. X-32 on mil power.

    Downthrusting might not be the answer to the range matter, because it's TSFC that matters. Downthrusting the F-135 means lowering the inlet temps- cut fuel only and you run too hot on an already extremely hot turbine. I think what you want is higher output on a lower power setting to reduce TSFC and increase range. Or reduce weight, or increase fuel capacity, or change the way the pickups are located in the tanks to make more fuel useable.
    Last edited by highsea; 27 May 11, at 23:45.
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  9. #39
    Military Professional wabpilot's Avatar
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    Quote Originally Posted by Blademaster View Post
    Why is this necessary to develop a VTOL plane? By looking at the costs of the feature involved, we would have been better off by building more Charles de Gaulle style ships for the Marines. Those ships would have catapults and we would have spend a lot less than $1 trillion dollars.
    We didn't develop a VTOL plane. The F-35B is STOVL. Short Take Off Vertical Landing. Although, it is capable of vertical takeoffs, it just consumes way too much fuel to make them practical. The F-35B was/is driven by the USMC and RAF/RN desire to replace the Harrier/Sea Harrier with a similar aircraft. Admittedly, STOVL makes little sense for the RN if they really do put their CVFs into service. The F-35B is a necessity for Italy and Spain though. None of the ships they have or might build will be big enough for CATOBAR operations.

  10. #40
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    I'm not sure I understand... the STOVL variant is unique compared to the Harrier or Forger in that the engine has a PTO shaft that powers a lift fan. This was a bold move by LM but it paid off in that the amount of lift is much greater than pure nozzle slew. I know the nozzle swivels at the rear as well, but why would this be melting surfaces so much more aggressively than earlier generation VTOL?


  11. #41
    Idiot Mode [ON] OFF Senior Contributor YellowFever's Avatar
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    Quote Originally Posted by wabpilot View Post
    The B has some other issues. Engine temperatures are a bigger problem with the B. We are melting asphalt on the ramp at Pax River. If the deck coatings are not more heat resistant than the very worn coating at Pax River, we may be in trouble.


    Ok, so the obvious question this amateur has is:

    It would be much cheaper to manufacture a heat resistent surface, about half an acre or so on smaller foreign carriers and whichever surface the B model would land on as oppossed to actually solving the problem of the engine melting the ramp........no?

  12. #42
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    It also has to be resistant to the various chemicals and fluids, saltwater, not wear prematurely, oh and we'd have to use it on a lot of airports/airfields or restrict the airplane from landing anywhere untreated (most of the world).

  13. #43
    Senior Contributor Stitch's Avatar
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    Quote Originally Posted by Chogy View Post
    I'm not sure I understand... the STOVL variant is unique compared to the Harrier or Forger in that the engine has a PTO shaft that powers a lift fan. This was a bold move by LM but it paid off in that the amount of lift is much greater than pure nozzle slew. I know the nozzle swivels at the rear as well, but why would this be melting surfaces so much more aggressively than earlier generation VTOL?

    I think highsea pointed this out; modern low-bypass turbofans run hotter than earlier turbofans because they are able to extract more thrust from a given amount of fuel. For the most part, higher ST is due to higher operating temps, something we're able to get away with now with newer high-temp turbines using newer technology. I think I even read somewhere that they're looking into ceramic-composite turbine blades that would allow even higher operating temps.
    "There is never enough time to do or say all the things that we would wish. The thing is to try to do as much as you can in the time that you have. Remember Scrooge, time is short, and suddenly, you're not there any more." -Ghost of Christmas Present, Scrooge

  14. #44
    Senior Contributor surfgun's Avatar
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  15. #45
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    I am so glad it wasn't that video from Battlefield 2 that spread through the internet like wildfire last year.

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