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  • Aviation Thread.

    For all things airbourne.

    I fly quite regularly. Every time I have some question that i Keep forgetting to ask. I'm sure there are some people on here that will know.

    What is the red tag the Marshall shows to the co-pilot once they've finished pushing out the plane.

    What does CAT I/II/III mean on runways?

    Why do 737's have no windows on the left hand side at row 10/11 but have them on the right hand side.
    https://www.picfair.com/users/MarkT128/

  • #2
    Non techy answer to the red tags - they are attached to pins that go into the noise gear to disable any inputs from the cockpit to enable the tug to steer the plane.
    Once the pin is out the hydraulics take over the wheel will straighten if its not already and the cockpit is in control again.

    I spent a few weeks in team aer lingus on the ramp doing turnarounds when I was 16 - mega fun!

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    • #3
      Originally posted by Boris View Post
      Why do 737's have no windows on the left hand side at row 10/11 but have them on the right hand side.
      On the missing windows, there is a fuselage strengthening member or part of the wing-fuselage mount somewhere round there on them:



      Only thing I can think of is that the seat plan is not symmetrical in the front half of the hull, and the windowed seats on the are at a slightly different position which allows a window cutout which doesn't clash with the main structure :



      I'm sure there's a couple of proper engineers on here who've seen below the skin of that particular beast on more than one occasion, so shouldn't take long to get a proper answer
      Last edited by -alan-; 26-08-2013, 01:35 PM.

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      • #4
        Although I am no plane-spotter. I saw what I am 99% sure was a Catalina Flying Boat over Dublin city centre at around 13.00 on Saturday.

        Looked like the one in the link below

        http://en.wikipedia.org/wiki/Consolidated_PBY_Catalina

        Did anybody else see it?

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        • #5
          yeah, isn't it for the dublin air show? flyovers on the liffey and all that.

          See here:

          http://www.flightfest.ie/displaying-aircraft
          Last edited by Jeremy Taxman; 26-08-2013, 03:37 PM.

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          • #6
            Originally posted by Boris View Post
            What does CAT I/II/III mean on runways?
            The category of instrument landing system the runway supports, as far as I understand it:

            http://en.wikipedia.org/wiki/Instrum...ILS_categories

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            • #7
              The pin is as mentioned by Rochey to disconnect the nose wheel steering so the tug can manipulate the direction of the nose wheel on push back. Pilots have to see it before they will taxi. There are other pins and clamps for the main wheels. Lots of planes depart every year with these still in place. They stop the gear from retracting. No harm just embarrassing for crew, engineers and an angry email from company.

              The link to the ILS by cdiv explains it. But if you fly a lot or to less well funded or less busy airports you might not have flown an ILS. You might have flown a pure r-nav approach which uses imaginary waypoints on the GPS in the horizontal and vertical to bring you within visual (hopefully) distance of the runway. E.g 1 mile for Belfast international 07.

              Or you might use NDB (rare) or vor. The approach into Nice is usually a Vor even though they have an ILS. The ILS fly's you over the rich people so they send you to do a for over the sea to end in a visual.

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              • #8
                As above, the pin puts the steering into bypass so the tug can turn the wheel, interestingly the BAe RJ85 doesn't actually have a bypass on the steering which is unusual, just don't turn on green hydraulics with the towbar on
                Dr Per Gillbrand - "

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                • #9
                  Originally posted by kicks View Post

                  Or you might use NDB (rare) or vor. The approach into Nice is usually a Vor even though they have an ILS. The ILS fly's you over the rich people so they send you to do a for over the sea to end in a visual.
                  I was very surprised to learn that Belfast City does not have an ILS. Slightest bit of Fog shuts the place down. May have changed recently but as of about a year ago, they did not.

                  The 'Sawing' noise on various Airbuses while taxiing, I know that it's some sort of Hydrualic gizmo balancing a load or similar, but why does it have to be so friggin noisy and how come other manufacturers don't need one?

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                  • #10
                    Originally posted by Pearse View Post
                    The 'Sawing' noise on various Airbuses while taxiing, I know that it's some sort of Hydrualic gizmo balancing a load or similar, but why does it have to be so friggin noisy and how come other manufacturers don't need one?
                    I presume you're talking about the PTU (power transfer unit), its basically a hydraulically driven hydraulic pump, if that makes sense. I can't speak for Airbus as I can't remember but the Avro RJ you have two hydraulic systems, yellow and green, the yellow system can be pressurised by the engine driven pump on the #2 engine or by an AC electric pump, the green system is powered by the #3 engine pump or can be powered by the yellow system through the PTU, therefore you can have full hydraulic power on the ground without any engines running and it gives you backup for various systems in flight or in case of failure. I can't remember the exact figure but when the pressure in the green system drops a few hundred psi below the yellow system the PTU will kick in once the switch is on. System pressure is about 3000psi, also worth mentioning that no fluid is transferred between the two systems and if my memory is right power can only be transferred from yellow to green. If that makes sense. I can't find a schematic online to show it.


                    The airbus is a bit different, three hydraulic systems and I honestly don't know why the PTU would be running while taxing but at a guess I'd say kicks might know.

                    Heres a diagram of the system on an a320 http://ozten.net/aviation/a320/image...etehydjpeg.jpg
                    You'll probably be able to make some sense of it.

                    And I think the 737 has a PTU as well but I always remember the airbus one making a fairly distinctive barking noise
                    Dr Per Gillbrand - "

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                    • #11
                      Originally posted by J_K View Post

                      And I think the 737 has a PTU as well but I always remember the airbus one making a fairly distinctive barking noise
                      Well the Airbus one sounds like someone is sawing off the undercarriage. Very noisy.

                      I also notice the rear rightmost seats on 737's have some sort of something overhead that makes a racket (like a Dyson Airblade hand dryer) throughout the entire flight. Very noisy seats and best avoided,

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                      • #12
                        Originally posted by Pearse View Post
                        Well the

                        I also notice the rear rightmost seats on 737's have some sort of something overhead that makes a racket (like a Dyson Airblade hand dryer) throughout the entire flight. Very noisy seats and best avoided,
                        That's the cabin utilities running to power stuff like boilers and ovens.

                        Comment


                        • #13
                          Originally posted by J_K View Post
                          I presume you're talking about the PTU (power transfer unit), its basically a hydraulically driven hydraulic pump, if that makes sense. I can't speak for Airbus as I can't remember but the Avro RJ you have two hydraulic systems, yellow and green, the yellow system can be pressurised by the engine driven pump on the #2 engine or by an AC electric pump, the green system is powered by the #3 engine pump or can be powered by the yellow system through the PTU, therefore you can have full hydraulic power on the ground without any engines running and it gives you backup for various systems in flight or in case of failure. I can't remember the exact figure but when the pressure in the green system drops a few hundred psi below the yellow system the PTU will kick in once the switch is on. System pressure is about 3000psi, also worth mentioning that no fluid is transferred between the two systems and if my memory is right power can only be transferred from yellow to green. If that makes sense. I can't find a schematic online to show it.


                          The airbus is a bit different, three hydraulic systems and I honestly don't know why the PTU would be running while taxing but at a guess I'd say kicks might know.
                          This is mostly it. We call it then barking dog. In the airbus there ware 3 systems. Green, Blue and Yellow. When we push back and start an engine the ptu will transfer power to provide hydraulics to either the green or the yellow systems. The blue system is not connected to it. If you hear it while taxing it is because the crew are preforming single engine taxi. This is getting more common to save fuel. The different systems are used for normal braking green side, alternate braking yellow, flaps, slats etc. Although this differes plane to plane because newer planes and older planes can have different things run from the 3 systems.

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                          • #14
                            This is a good thread.

                            I wondered what all the 'cross checking' was about...
                            http://www.askthepilot.com/how-to-speak-airline/

                            I have been curious about "fuel dumping" in flight booking for a while.

                            http://hackmytrip.com/2012/01/introd...-fuel-dumping/

                            on www.flyertalk.com theytalk secretively in code about it, but they manage to do things like book flights from Europe to the US for $200 by playing with bookings.
                            "All the finesse of a badger." (cdiv)

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                            • #15
                              Turbulence:

                              How come some times the "fasten seat belt" sign is activated due to anticipated turbulence which sometimes does not materialise? I know that there are different types of turbulence, caused by mountains, jet stream, wake from an aircraft flying ahead and that some may not be detectable via LIDAR. I'm also conscious that sometimes turbulence can strike without warning (characterised by the use of "immediately" in the address from the flight deck telling cabin crew to take their seats) but other times you're on a flight where they seem to just leave the light on (cheap form of insurance?) so now I just remain belted up all the time.

                              Is it that the aircraft is being radioed by another plane ahead on the same flight path who advised that turbulence was encountered and by the time the second aircraft arrives at the location the turbulence is no longer present?
                              1998 Porsche 911 3.4 Carrera 2 (996)
                              2000 Mazda MX-5 1.8 Jasper Conran #68/400
                              2003 BMW 325i E46 Sport Touring


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