Operate the window switch sends a coded signal to the UCH, which in turn operates the window. This powers up from the ignition signal, interacting with the security system to get information from the key before powering up the car. Now, on a modern car, the power goes to a UCH, body computer. When you operate it, it sends power to the motor. This circuit goes to a fuse, then on to the power side of the window switch. Your car has a live circuit, switched on by a relay via the ignition switch. On an older car, you operate your electric windows. Later aircraft benefitted from General Dynamic's work on the YF-16 and have this mythical databus. Overhead sections shared common wiring harnesses so it was relatively easy to route a voltage to a common warning light on the MWP. Components were wired to their respective sides in autopilot, instruments and warning lights. The 737 pre-dates the concept of the Databus, 1553 or whatever. I think nearly all real 737 pilots agree with you!įundamentally, you need to get below the surface a bit. Here's the link to the YouTube video I think you'll find it really interesting. Assuming that PMDG modeled the 737-800 correctly and that there is no required additional warning light in that model, it raises the question why would the FAA confine its directive to only the 100 to 500 class and not the 600 to 900 class which by my personal experience suffers from the same deficiency? Curiously, the PMDG 737 NGX doesn't model this additional warning light (I frantically searched for one when I got the alarm). I think I corrected the problem at 18000 ft so I and my virtual crew and passengers survived.īut more interesting is that, according the the accident re-enactment, in March of 2011 the FAA issued an air worthiness directive requiring all 737s of the 100 to 500 class to have two additional cockpit warning lights, presumably (though it was not clear) to differentiate between a takeoff config and a cabin pressurization alarm. On my last encounter I did finally put two and two together and finally diagnosed and found that the bleed air was off (have no idea how it got in that position). Amazingly, other than the audible alarm there is NOTHING that I could find that identified the problem. What is interesting is that in my own experience with the PMDG 737-800 on some rare occasions I have gotten that alarm myself but didn't know what it was (I've never taken cabin pressurization seriously while sitting in my desk chair at 350 ft ASL while simming).
#Helios flight 522 how to
(One cabin steward remained conscious but didn't know how to fly the aircraft and so died in the crash when it ran out of fuel)
#Helios flight 522 manual
It had been place on manual mode and left there by an engineer checking a door seal problem and they failed three times in the preflight and after take off checklist to identify this. Amazingly even after calling maintenance, they never identified that problem was with the pressurization system. The alarm went off at 10000 ft and they couldn't understand why the takeoff configuration alarm was sounding while in the air when it is only suppose to sound on the ground. The highly experienced pilots misinterpreted the cabin pressurization alarm with the takeoff configuration alarm which sounded identical. This was the crash of Helios Airways Flight 522. I came across an interesting accident re-enactment on the FlightChannel on YouTube.
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