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For aviation fans: Immelman turn in a B-47

Discussion in 'Bad Dog Cafe' started by KokoTele, Jun 8, 2013.

  1. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    I saw this on an aviation forum and thought some of you guys would enjoy watching as well.



    Many people don't realize that most airplanes are capable of loops and rolls if the airspeed is managed well enough. Loops are a little trickier, but rolls are almost always manageable. An Air Force pilot demonstrated this to me in the C-5 simulator. (Actually, he said "Put the nose down to get some speed, and at 300 knots pull the nose up 10 degrees above the horizon and crank 'er over.")

    As long as the airplane has a decent rate of roll, maneuvers like this are done at low G-loading that any plane can handle.

    Here's another famous example:

     
  2. Buckocaster51

    Buckocaster51 Super Moderator Staff Member Ad Free Member

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  3. tfsails

    tfsails Friend of Leo's

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    The B-47 was used in perfecting the toss-bomb maneuver. The F-105 was designed to do just that ten years later. To my knowledge, nobody ever dropped a live nuke out of a Thud using toss bombing. We had the toss bomb computer on our Thuds when I worked on them, but we didn't maintain it. The space for the bomb in the Thud's bomb bay was taken up by the bomb bay fuel tank.

    It's impossible to loop or roll any Airbus. Their flight control laws (they're fly-by-wire) limit commanded pitch to +/- 30 degrees and roll to 60 degrees either side of leve.
     
  4. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    That's true. The airframe is capable of it, but the avionics have something called "flight envelope protection" that prevents pilots from performing that kind of maneuver.
     
  5. TieDyedDevil

    TieDyedDevil Tele-Holic

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    There's no override?
     
  6. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    Nope. Sounds scary to most people (and pilots), but the Airbus crashes have proven that the system is much safer than letting pilots fend for themselves.

    It's very, very common for pilots to fly the plane into a stall in the last moments before a crash. This causes a very high rate of descent and (often) loss of control. The Airbus envelope protection won't let the pilot stall the plane, so controlled glide continues all the way to the ground. The impact forces are greatly reduced, the airplane is usually fully upright, and injuries are less severe.
     
  7. Joe-Bob

    Joe-Bob Doctor of Teleocity

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    They did that with a Concorde, too. I saw the documentary. One pilot did a 1G roll. The other one said, you wound it up, now I gotta unwind it, and he did another roll the other direction.
     
  8. sacizob

    sacizob Friend of Leo's

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    I saw a B-1 Bomber do a barrel roll at an airshow.
     
  9. slauson slim

    slauson slim Friend of Leo's Platinum Supporter

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    Thuds - Thunderchiefs - F-105s. The original Wild Weasals. Triple Threat Jet.
     
  10. abracadabra

    abracadabra Tele-Meister

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    unfortunately the data on the Airbus is inaccurate :D

    normal flight control law allows roll up to 60 degree of bank, but with downgraded control laws the aircraft will roll inverted quite happily.

    also, the aircraft is only as good as its inputs, so if you have a simultaneous erroneously low rad alt reading on an ILS, the aircraft will quite happily stall as well. the Turkish Airlines 737 at Amsterdam crashed for that reason, and it subsequently emerged that Airbus aircraft can suffer the same fate as well. and with downgraded control laws it will stall just the same as any other aircraft, such as the Air France A330 crash whose initial failure was an also input one (frozen pitot tubes).

    but I'm nitpicking of course. the flight control laws are designed to, and do, make the aircraft much safer. :)

    btw, was great to see that 707 roll. I read a book called 'Test Pilots' (I think) when I was a kid, which recounted many great anecdotes, of which that was one.
     
  11. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    By downgraded control laws, do you mean that there's some data input missing/invalid so the computer allows expansion of the flight envelope into more dangerous territory?

    My knowledge is from a chapter on it in the book Fly By Wire, plus one other article I read in an aviation magazine years ago, so I admit I'm not an Airbus encyclopedia :)
     
  12. Obsessed

    Obsessed Telefied Silver Supporter

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    Great video! What was the lifespan of the B-47? How many were made? Was there an issue with landing that machine?

    As an engineer (no avionic education), I just want to throw on some gussets in back of the wing at the fuselage. Some of the fighters of that era were of the same design.

    The concepts developed during those early years of the Cold War. Scary, but true.

    Okay, I'll google it.

    Thanks for sharing!
     
  13. jefrs

    jefrs Doctor of Teleocity

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    Yes, Concorde could be rolled and looped like a fighter. No need for zero-gee.
    The airframe was suitably stressed for such manoeuvres, but was only done with the prototypes not production aircraft. Father in law was senior flight engineer Concorde. He was trained to pilot the aircraft if necessary and the Concorde roll was one of the simulation exercises.

    Here's another one that made it look easy -


    Military airframes are built for violent manoeuvres.
     
  14. BiggerJohn

    BiggerJohn Friend of Leo's

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    It was for toss bombing with nukes, to get the delivery aircraft out of the way when the nuke exploded, to try to save the crew. I think Thuds could toss bomb as well. Military thinking has changed since then.
     
  15. 4string

    4string Friend of Leo's

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    Dude. I once got a ride in a P-51D "Ridgerunner III". We did a couple sets of 4-point rolls. Not so bad. The loops? Ok, this is cool and all, by why is the 2nd loop changing into straight up?

    It was the tailslide stall into 4-point roll/dive with 7-8 G pullout that put my lunch, stomach, and probably intestines too in the "sickness bag".

    After falling out of the cockpit, a wheelbarrow was requested for further transportation and given full denial. Crawl worm, crawl......
     
  16. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    Here's a little known fact about the P-51: It has an incredibly slow rate of roll for a fighter, about 90 degrees/second at most airspeeds. That's 4 full seconds to do an entire aileron roll, glacial in comparison to modern airplanes, and slow even for its day.

    Those 4 point rolls were probably done absolutely as fast as they could be :)
     
  17. 4string

    4string Friend of Leo's

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    It wasn't snap-snap-snap-snap, it was more like s-n-a-p/hold (1001, 1002, 1003, 1004), s-n-a-p/hold (1001, 1002, 1003.......etc at about 400 mph. Oh, and we did the flat version at about 500 ft. The pilot, Dan Martin, used to race at Reno. He likes to fly near the ground. We were sideways way more often than flat generally speaking, and we were ???? (meaning I'm not sure what our relationship with the ground was) a lot too.

    We also shot through some canyons around Henry Coe State Park at full blast, missing ridge tops, trees, and cattle by less than the law says to if you get my drift.

    Happened 25 years ago, the memories are as vivid as yesterday.
     
  18. abracadabra

    abracadabra Tele-Meister

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    there are seven computers which perform various functions within the FBW system, and they get inputs from many many different sources. as a general rule of thumb, a single failure of any one of the aircraft systems, whether it be hydraulics, air data reference, inertial reference, flight controls, the flight control computers themselves, electrical buses etc, that has anything to do with the FBW system, will not cause a downgrade in the flight control laws. the 'law' will remain 'Normal'.

    however, a dual failure in any of the above systems (and others), will usually result in various levels of downgrade. the first stage is to 'alternate' law, which is like a dumbed-down version of 'normal', and the next is 'direct' law, when the plane behaves broadly like a non-FBW aircraft in terms of how is it controlled. there are a couple of other 'laws' but I won't bore you with that!

    anyway, in both 'alternate' and 'direct' law the aircraft loses its pitch and roll protections, which is what we were taking about, and can be flown up-side-down. :)

    it also does not require a failure to enter into such a downgraded state, a couple of computers can simply be turned off to achieve the same thing.

    I should also say that the FBW system Airbus has is fine in principle and 99.9999% of the time, but like any computer system it is only as good as the information fed into it. if it is fed erroneous Rad Alt data, the pitot tubes supply simultaneous incorrect readings, or the AOA vanes supply simultaneous incorrect readings, for example, remaining in normal law would be extremely dangerous. it has undoubtedly made the aircraft much safer in general, but a great deal of understanding and care needs to be applied, unlike non-FBW aircraft, to ensure that the very system that 'makes it safe' doesn't sometimes do the opposite!

    :)
     
  19. Guitarzan

    Guitarzan Poster Extraordinaire

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    I don't know a single pilot that would agree with you, and I've discussed it with quite a few, including men that served as test pilots. Airbus says that, but people know better. Their system is only as good as software programmers can be. I'd rather trust good pilots than software programmers. The recordings of the pilots in the crash of the Airbus from Brazil bound for Europe does not support it.
     
  20. tfsails

    tfsails Friend of Leo's

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    My FBW experience is limited to the F-16, so I'll have to pass on arguing this point because I just don't know enough about the Airbus's system to argue intelligently.

    The term "flight control laws" in Viper vernacular describes the capabilities the programmers designed into the FLCS software and verified by flight test during development.

    When the F-16 has multiple failures, the FLCS (flight control system) goes into "standby gains" mode, which degrades aircraft capability somewhat, but not a whole lot. If the Airbus's backup system, "alternate law" allows the pilot to exceed pitch and roll limits set by the "normal law" system, that would surprise me. As it is, I cannot imagine that the Airbus designers would design a system that allows the pilots to purposefully degrade the system in flight. It's impossible to turn an F-16's electrical system off once the airplane is in flight; I would strongly suspect that the Airbus has a similar design with its systems.

    I can see the headlines now: "Airbus captain lets son fly his airliner. Son turns FLCS computers off so he can roll the airplane. Airplane crashes with 250 deaths". Can you imagine the legal ramifications in today's litigious society??

    BTW, a similar accident scenario occurred in Russia within the past 15 years where the pilot let his son fly the airplane on a revenue flight and it crashed.
     
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