Comments by "SeanBZA" (@SeanBZA) on "Mentour Now!" channel.

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  16. My father crashed one, after leaving the one wheel in the middle of a pothole on the runway, hidden by the part time airport having had heavy rain in the morning, and on approach in the late afternoon my father had seen the shiny water, and thought that the airport had finally tarred the runway instead of being grass, and was just late in updating the charts they had with outside countries. Nope, was water, and on landing he was getting spray, and then the one landing gear left. So he decided to cut power, using those magneto switches, up there for making turning off the engines a deliberate action you could not do by accident, and went gear up. So skidded to a halt outside the terminal/bar, where the part time ATC was belatedly firing a flare into the air to denote to go around. Passengers did not notice the accident, aside from them not needing a ladder to disembark, and them noticing the 2 bent propellors. Long distance phone call was made, via a good number of operators, to the destination airport, and the actual owner of the aircraft that he was doing a ferry flight on. Next morning the new plane was there, dropping off a crew of mechanics, 6 blades for the propellors, and the left undercarriage complete, and the tools and jacks. This then left with the paying passengers, down south to Johannesburg. A week later the aircraft, now repaired, flew back down with the mechanics and the damaged parts. Very likely I did fly on that exact aircraft, years later, in the military, as they got the entire fleet as the airline upgraded. My last flight in the military was on one, and of course it had issues, with me and the FE leaning out to look at the gear, as the right side was very unhappy to show green. I was the human chain, holding his belt, and acting as audio relay, while we both agreed it looked like it was over centre, and thus locked. Best landing ever on a C47, smooth, almost no bump, though slightly marred by having a fire engine keeping pace with us, with foam cannon ready to use. Got in to destination 6 hours late, and when asked, I replied the C47 broke down over the last stop, and we all had to get out and push it the rest of the way.
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  25.  @wolfgangpreier9160  The original 747 inertial measuring unit had 2 gyro assemblies for each axis, and would run if one of each failed. However that was not considered reliable, so there are 2 IMU assemblies, both located by the CG of the aircraft by the wing root. These then form the stable platform on which the acellarometers are mounted, and then the navigation computers, 2 again, each using the data from the 2 IMU sent to them, with each having it's own acellarometers and angle sensors. They then are correlated and displayed, and each checks the other. A very good system, just that you need to have the aircraft powered up on the ground, at a precise location, normally nose wheel parked on a paint dot, and the other wheel bogies on a set of painted lines, which were entered into the system as a known waypoint. Then sit there for a half hour while the computer sits and calculates drift for you, compensating for the drift of the earth rotating, the orbit of the earth around the sun, and the drift of the sun orbiting around the galaxy. Also the drift of the platforms as well, as they get slewed to have that as the initial level, and keep it for the powered up portion of flight. No vibration, no loading of the aircraft in any way, which makes it hard to keep it accurate. GPS is an augmentation, but as a single system cannot be said to be redundant, and fault that takes out the antenna will stop it working, and there are not many locations for the antennas either, as the GPS receiver calculates the position of the antenna, so it has to be mounted on top of the aircraft, in a spot above the wing root and the CG. Also power levels are low, the individual satellites only have a 500W power budget or so for the transmitter, which has to cover a good chunk of the planet, and thus the received power is very low, well below the noise, and only recovered by using complex mathematics to reconstruct it. Spoofing has a receiver that gets the area signals, and then keeps a rough lock on them, but retransmits up to the target location a signal that is stronger, but which slowly is shifted in time, so as to fool the receiver into thinking the stronger signal is the real one, and the position it is giving is valid.
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  36. Have been in a barrel roll, in a helicopter, and can agree that it is a low G manoeuvre, as I was sitting there, looking out the open door, with my legs outside, and looking down below my feet at the sky, and up overhead to the ocean. Very frustrated pair of pilots and the flight engineer, who had just spent the last 3 hours baking in the cockpit, with engines running, but zero collective, doing a compass swing and alignment, after replacement of the gyro compass magnetic pick up in the tail. I had been the human intercom between the poor guy being cooked in the tail, and the flight engineer, relaying from the pilots the readings on the 3 axis data displays for magnetic azimuth. At least we did not have to stop, like the last day, because one of the 2 gyro assemblies had dropped out, with a barberpole on the display, just near the end. Also the 707 had really good cross wing landing performance, I had a front row seat to that, with a perfect near textbook landing, while the 2 C130's that went before scrubbed all tyres to nothing on the landing, and did a really hard landing, which was audible inside the cabin of the 707. you could not feel anything, till the reverse thrust was applied full, and the pilot announced, that for all those interested, on open mic, that we had landed 10 seconds before. too bad my instructor was on one of those 2 planes, and had thought us 12 last ones were flying on a C47, we got put on the tanker instead. C47 was there to deliver AOG parts, and had spent the night as well.
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