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off topic. Pitot tubes

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  • #31
    Re: off topic. Pitot tubes

    Originally posted by stuntflyr View Post
    I have to fly with those types every day. They're usually ex-military
    Well, quite honestly, before my current assignment where I fly with USAF pilots from many non-fighter airframes, I would have never believed it. Now...I do.

    I'd never seen that sort of thing anywhere in any of the nooks-and-crannies of the fighter and trainer community where I've spent my career. I've seen plenty of pilots who were all over the skills spectrum; some fantastic, some average, and some below average. All of them, however, came from aircraft where, if there was even an autopilot or TCAS on the airplane, it was only used extremely rarely. The vast majority of the flying skills were of the actual stick-rudder-throttles variety. When given a raw "flying skills" task, the majority of them were quite good at making the jet do what it needed to do.

    Note: I'll admit that after years of such experience, I was completely unaware of how to work modern FMS systems and skillfully manipulate an integrated autopilot. That was probably my most significant challenge in getting my most recent type rating: I wanted to solve every problem I couldn't sort out by kicking off the autopilot and hand flying...which didn't exactly meet the intent of the training course, ergo to learn how to operate the systems on the new aircraft. But, I have to ask, what's the bigger challenge: learning to work an FMS, or re-learning stick-and-rudder? I'll take my predicament, thanks, rather than the other way around.

    Never, however, had I ever seen in my USAF career pilots who use the automation so much that they see actual core skills like stick-and-rudder and visual lookout as contingencies when the FMS, autopilot, and TCAS are inop. I don't know if it's the result of apathy or simply "the way it is" in some of the heavy communities, but it sure as hell is rampant. It's probably something, as mentioned in my last post, that serves these pilots perfectly well in 99% of what they're called upon to do in their particular jobs. I can imagine that hand-flying a 9-hour transoceanic crossing would get a little tiresome (although I did it in the Eagle several times...but C-17 and KC-135 and KC-10, etc, pilots do that regularly).

    I don't think it's a "talent" issue with these guys -- they're not some kind of morons, and clearly they possess the skills and intelligence to make it through rigorous training and maintain high standards in their own missions. I think it's more of an "experience" issue - flying skills are perishable, and without frequent practice they can atrophy quickly. Some of these pilots simply aren't called upon to use the basic skills that often, and as such, their skills in working the automation are the ones that are the sharpest. Naturally those skills are the ones they're going to call upon first.

    I have, however, now witnessed what you mention in your post with mine own eyes...and therefore I now Believe.

    Comment


    • #32
      Re: off topic. Pitot tubes

      Originally posted by tow-3 View Post
      one airline, who shall remain nameless, prohibits flying a SID without the autopilot because they have had to many deviations, I cant believe that there skill set has gotten so bad that they cannot follow the FD hand flying.
      Can you at least give a hint for those of us who aren't airline guys??

      Comment


      • #33
        Re: off topic. Pitot tubes

        oh, lets just start at the top of the alphabet..........
        bob burns
        ex tow-3, now race 66 crew
        "dont mess with texas"

        Comment


        • #34
          Re: off topic. Pitot tubes

          After years of flying Boeing glass jets I now find myself stuck in a 747 "Classic" which has a very crude autopilot (the L-1011 was sooo far ahead of Boeing back in the day) with autothrottles that sometimes work, sometimes don't. I can't even count on my flight director to be operational. The work load required to hand fly these old jets in Europe, Asia and Africa is very high due to the nav precision required and the airspace congestion. I would kill for an FMS! In my opinion, the fully automated glass flightdeck that Boeing developed with the 757/767 is the standard by which all autoflight systems should be judges, in a two man cockpit it's vital to safety. Having said that, if a guy can't hand fly the big jet well without the AP he probably won't be able to do it well with the AP on and vise versa.

          Speaking of stalls at altitude; The old DC-8 which had a not so swept, swept wing had an interesting high speed buffet, stall mode. At altitude, any vertical acceleration due to mountain wave activity or turbulence would cause the center of pressure or lift, to move aft on the wing resulting in a nose a down pitching moment. A very simple system called the Pitch Trim Compensator (PTC) would apply back pressure to hold the nose up by pulling directly on the FO's elevator control cables under the floor. This was in addition to the stabilizer nose up trim. If you were close to your high speed buffet with the PTC fully extended you could find yourself going for a ride. The stall would brake nose down and the recovery would require the pilots to trim the stabilizer to the natural range before applying nose up elevator to recover. The effect is the same in modern jets, a high altitude upset may require pilots to unload the wing by first re-trimming the stabilizer to neutral to regain elevator authority....Dennis

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          • #35
            Re: off topic. Pitot tubes

            Originally posted by tow-3 View Post
            oh, lets just start at the top of the alphabet..........
            Are we talking about big, silver polished jets that start with AA, or smaller white jets that start with AE?

            Comment


            • #36
              Re: off topic. Pitot tubes

              the turbo-prop fleet at AE doesn't even have and FMS capable of doing a SID. most of the ATR fleet does not even have a FMS. The Jet fleet is capable and has no restrictions requiring the use of the AP for the SID.

              as was pointed out to me, Big brother has now made it a suggestion to use it, not a total requirement.
              Last edited by tow-3; 06-04-2011, 02:57 PM.
              bob burns
              ex tow-3, now race 66 crew
              "dont mess with texas"

              Comment


              • #37
                Re: off topic. Pitot tubes

                The following was forwarded to me by a very high-time, experienced pilot. He did not write it, but was merely sending it to me because he felt I would 'get it'. Take it for what it's worth, considering the writer wishes to remain anonymous.

                -----------------------------------------------

                Letter of the Week: Airbuses Fly "Like a Video Game"

                I would like to offer my comments and perspective with regard to the Air France Flight 447 accident. I have been a A-330 captain since 2003 and have over 4500 hours in the aircraft. While many A-320 pilots undoubtedly have more series time, I believe this probably makes me one of the most experienced A330 pilots in the world.

                When asked how I like the aircraft, I tell people that there is likely no easier airplane to take over an ocean, and that the systems design and presentation is superb. That said, the automation is more complex and less intuitive than necessary, and the pilot-aircraft interface is unlike that of a conventional aircraft. Most important with regard to this accident is the fly-by-wire sidestick control. The sidestick itself has a very limited range of motion, making inadvertent over-control very easy. Of even greater significance, the stick itself provides no "feel" feedback to the pilot. That is, unlike a conventional aircraft, the pilot does not get a sense through pressure of how much input is being sent to the control surfaces. The most important advice I give to pilots new to the Airbus is to treat the aircraft not as an airplane, but as a video game. If you wait for the sidestick to tell you what you are doing, you will never get an answer.

                Taking into consideration that Air France 447 was at FL 350 (where the safe speed envelope is relatively narrow), that they were in the weather at night with no visible horizon, and that they were likely experiencing at least moderate turbulence, it does not surprise me in the least that the pilots lost control of the aircraft shortly after the autopilot and autothrust disconnected.

                Let's keep in mind that these are not ideal conditions for maintaining controlled flight manually, especially when faced with a sudden onslaught of warning messages, loss of autofllght, confusing airspeed indications, and reversion to "alternate law" flight control, in which certain flight envelope protections are lost.

                A very bad Airbus design feature is thrust levers that do not move while in autothrust. They are instead set in a detent which would equal climb trust in manual mode. If the pilots did not reset the thrust levers to equal the last cruise power setting, they likely eventually ended up in climb power, making it difficult to reset the proper cruise power setting and adding to what was likely already a great deal of confusion.
                But the real problem probably occurred immediately after the pilot flying grabbed the sidestick and took over manually. Unfortunately, airline pilots rarely practice hand-flying at high altitude, and almost never do so without autothrust engaged. As a result, we forget that the aircraft is very sensitive to control inputs at high altitude, and overcontrol is the usual result. Because the Airbus sidestick provides no feedback "feel" to the pilot, this problem is dramatically compounded in this aircraft.

                I believe the Air France pilot grabbed the sidestick, made an immediate input (because as pilots, that's what we tend to do), and quickly became quite confused as to what the aircraft was truly doing. This confusion likely was exacerbated by fixating on airspeed indications that made no sense while trying to find a power setting with no airspeed guidance.
                When transitioning from autopilot to manual control at altitude in the Airbus, the most important thing to do at first is nothing. Don't move a thing, and then when you do, gently take hold of the sidestick and make very small inputs, concentrating on the flight director (which, in altitude hold, should still have been providing good guidance). Of course, this is much easier said than done with bells and whistles going off all over the place, moderate turbulence and a bunch of thunderstorms in the area. As I said before, treat it like a video game.

                So why did the Air France pilot find himself at the limits of sidestick travel, and then just stay there, maintaining a control input that simply could not logically be correct? When things go really bad and we are under intense pressure, it is human nature to revert to what we know from previous experience. Remember, the Airbus flies like no other aircraft in that the sidestick provides no feedback to the pilot. It is a video game, not an airplane.

                I believe the Air France pilot unintentionally fell back on all of his previous flying experience, in which aircraft controls "talked" to him when he moved them. Distracted by many confusing inputs, he instinctively expected to be able to control the aircraft by "feel" while dividing his attention to address other matters. I've seen it happen in the simulator, and in an Airbus this is a sure way to lose control of the aircraft and is possibly the most dangerous aspect of Airbus design philosophy.
                One last note: Airbus pilots often claim that the aircraft "can not be stalled." When the flight controls are in "normal law" this is a reasonably true statement. However, in "alternate law," as was the case here, stall protection can be lost. If we ever practiced this in the simulator, I don't remember it.

                Lest anyone think I am blaming the Air France pilots for this accident, let me be clear. Despite all of my experience in the aircraft, I am not the least bit certain that I would have been able to maintain control under the same circumstances. I do feel certain that were you to spring this scenario on pilots in a simulator without warning less than half of them would have a successful outcome. Safely flying the 320, 330 and 340-series Airbus requires something of a non-pilot mindset.

                Name Withheld

                Comment


                • #38
                  Re: off topic. Pitot tubes

                  Originally posted by Big_Jim View Post
                  Take it for what it's worth, considering the writer wishes to remain anonymous.
                  And we'll see why here:

                  Originally posted by Big_Jim View Post
                  I believe this probably makes me one of the most experienced A330 pilots in the world.
                  Wow. Can I have your autograph? Can I guess US Air east, or..?

                  Originally posted by Big_Jim View Post
                  Despite all of my experience in the aircraft...
                  Thanks for the reminder! I bet this guy is a PEACH to fly with!

                  There is a much easier way to explain this, and it's not really ALL about the Airbus: anything that is FBW is much like a video game. The stick provides plenty of control authority, but there isn't any feel to it. All of your feedback is visual, and in that sense, it's very much like a video game. There are some hydraulic flight control systems that have artificial feedback built into them in several ways.

                  They all make it easier to fly, and that's how we pilots want it. Are you going to design an aircraft like this that *might* be flown once under dire emergency conditions, and have those flight control systems tailored for that one chance, or for the 99.999999999% of its career that will be normal?

                  The Lancair I used to have had ZERO stick-force-per-G in pitch. The 737 has hydraulic flight controls, and the 787 is FBW as far as I know... The Cessna has cables and pulleys. In ALL of these aircraft, you NEED to be a pilot. I don't agree with Mr. Bigshot's assessment about this non-pilot attitude thing. BS to me. They're all airplane, they're all different, and I revel in the experience of flying them.

                  I'm just goofing on Mr. Bigshot Captain above, I mean no harm, but I have to put some sticks in the cage when he asserts his massive experience right off the bat.
                  Last edited by Scotty G; 06-07-2011, 01:07 PM.
                  Scotty G

                  Comment


                  • #39
                    Re: off topic. Pitot tubes

                    Originally posted by Scotty G View Post
                    There is a much easier way to explain this, and it's not really ALL about the Airbus: anything that is FBW is much like a video game. The stick provides plenty of control authority, but there isn't any feel to it. All of your feedback is visual, and in that sense, it's very much like a video game.
                    A question and then a comment from an engineer / non-pilot:

                    The question: don't some other manufacturers' FBW systems incorporate feedback derived from the control surfaces themselves? Yes, its "artificial" in that its just a servomotor tugging against your pressure on the controls, but doesn't that at least it make it feel more like you have a cable from the stick to the control surface?

                    And the comment: I'd guess its more like playing a video game while the Jolly Green Giant is shaking the building holding the arcade to see if it rattles. You're trying to precisely manipulate a joystick while the room is being tossed around by turbulence. At least when you're playing PacMan in an arcade you can count on down being down, up being up, and the roughly 1g sensation on your tush meaning you're rightside-up in a level room and not banked 45 degrees left but with a positive pitch rate. That's gotta be enormously confusing, and it just seems to me (remember: non-pilot!) that it would be easier to be wrestling with a big, heavy, feedback-rich B-24 yoke than a little PacMan joystick held in the center of its travel by springs. That's the engineer in me talking- make the feedback in the computer-assisted system you're building behave as much like the original mechanical system you're emulating as you possibly can.

                    I've kept out of the discussion precisely because I am a non-pilot and don't want to talk out my.. uh.. hat. Maybe its just the press coverage of these incidents, but it sure SEEMS like the company with about half the market share is accounting for WAY more than half of the incidents in which the pilot/machine interface is coming under scrutiny as a cause.

                    Comment


                    • #40
                      Re: off topic. Pitot tubes

                      I recently watched the PBS, Nova investigation of this accident. They recreated the scenario in the sim with some level of turbulence simulated. That was really laughable. You can't simulate moderate or higher, real life, turbulence in a sim without causing damage to the box. These AF pilots were likely experiencing at least moderate and maybe even severe turbulence judging from the satellite imagery that was presented. Turbulence is jarring and can through you violently against your belts. It makes interpreting flight instruments very difficult, especially at night and tape style airspeed and altimeter displays can turn into a complete blur. Attempting to make small, precise control inputs to that little joy stick seems almost impossible in the type of turbulence I'm describing.

                      Dennis

                      Comment


                      • #41
                        Re: off topic. Pitot tubes

                        440 Magnum,

                        I'm not aware of any way to get control feedback from the flight control surface in a FBW system back to the stick. First, the stick hits a transducer or whatever it is, and it generates an electrical signal that flows down the wire to another binky doohicky that makes a hydraulic servo move the control surface a certain amount.

                        The feedback would have to be generated somewhere else and fed back to the pilot by some separate means. Maybe there are systems like that, but I have no first-hand knowledge of them.

                        And you may be a non-pilot, but it's a discussion and all should be welcome to join.

                        And I whole-heartedly agree on the comments made about turbulence, reading some gauges, and making precise control inputs. You've all been there before.
                        Scotty G

                        Comment


                        • #42
                          Re: off topic. Pitot tubes

                          I have never flown anything with either boosted or fly-by-wire controls, or even many instruments. I do know that some cars (mine included) have a system to add feedback to the steering so that the faster you go, the less sensative the steering is. At speeds over 125 it takes a fair amount of force to move the wheel (compared to 10 mph). It keeps you from over-steering at speed.
                          Old school boosted controls had all kinds of bellows and weights to add feedback. Why isn't something like that done electronically, a progressive "stiffening" of the comtrols to prevent overcontrolling? Otherwise it seems it is about like my computer joystick. Not being sarcastic, it IS something I have wondered about.
                          Leo Smiley - Graphics and Fine Arts
                          airplanenutleo@gmail.com
                          thetreasuredpeacock.etsy.com

                          Comment


                          • #43
                            Re: off topic. Pitot tubes

                            Leo,

                            It's a good question, but the lightbulb over my head just went on...

                            We're all discussing something that isn't really necessary. For that 99.999999999999% of the time we're in normal ops, it just doesn't matter. You want something that's easy to move and doesn't tax you. And you're not on the controls all that much.

                            For that once-in-a-lifetime Air France scenario... Control feedback is the very least of your worries. Wouldn't have made a lick of difference.

                            So, we're discussing something - a control design that doesn't offer any sort of force-feedback - that doesn't even need to be there.

                            It's your experience in the seat that allows you to get to know the aircraft and know how it will react. Trust me, the 99.99% of the feedback you get is still visual and seat-of-the-pants anyway... It's really not an issue.
                            Scotty G

                            Comment


                            • #44
                              Re: off topic. Pitot tubes

                              Originally posted by Scotty G View Post
                              440 Magnum,

                              I'm not aware of any way to get control feedback from the flight control surface in a FBW system back to the stick. First, the stick hits a transducer or whatever it is, and it generates an electrical signal that flows down the wire to another binky doohicky that makes a hydraulic servo move the control surface a certain amount.

                              The feedback would have to be generated somewhere else and fed back to the pilot by some separate means. Maybe there are systems like that, but I have no first-hand knowledge of them.
                              Did some googling around over the last few days, and found many references to exactly this sort of thing in the 777 and in the F-16, but nothing too detailed on how it is implemented. Just that there are servomotors that do nothing except apply force to make the stick (or yoke) "feel" different as a function of airspeed, AOA, etc. to more mimic a direct connection to the control surfaces and to reduce the chance of over-control. Hey, its on the internet, it must be true, right? :-)

                              Seriously, I remember reading about feedback-enhanced FBW a number of years ago in an engineering journal, but don't remember many details. I seem to recall that the topic of artificial feedback (and the Airbus/Boeing split over whether to implement it or not) was all the buzz in man-machine interface field 10 years or so ago. I'll try to remember to post a link back to this thread if I run across anything definitive.

                              Comment


                              • #45
                                Re: off topic. Pitot tubes

                                I'm sure there are feedback systems, but like I said, I'm just not aware of them.

                                I don't know how the 'Bus is built, but the further you get from the center position on the stick, the "harder" it gets to move the stick. Well, I guess that's SOME form of feedback... It's supposed to tell you you're pushing, pulling, or rolling too hard. Whatever. It's not hard to hit the stops, but then the flight control laws limit you in terms of pitch, bank, and AOA.

                                On most flights with little wind, you shouldn't have to move the stick more than an inch back to rotate off the runway on takeoff, and about 1/4 - 1/3 inch for driving around. Throw in wind gusts to 38 knots or so, and the stick moves quite a bit more when you strive for wings level and the proper pitch. It's like any big airplane; not very precise because of mass and inertia.

                                The F-16 stick is extremely rigid and moves very, very little. F-16s can be pretty twitchy from what I've seen.
                                Scotty G

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