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Geoff_H

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Everything posted by Geoff_H

  1. Geoff_H
    Just a reminder, do not remove oxide from electrical contract surfaces with carborundum (emery) it attaches small quantities to the surface and will oxidise with electrical current.
  2. Geoff_H
    In the 1970's when we first used computers in industry for control we would get many failures, almost always on computer board connections, we would always carry an ink rubber to remove oxides, more often happening in we weather. We were told by plug manufacturers that 30,000 psi connection pressure was needed to prevent high resistance connections. I believe that earth connections should be checked regularly, particularly after a wet period like the east coast is experiencing
  3. Geoff_H
    I think that you maybe right. Is there a difference between the shield and the ground plane. My experience is with instruments.
  4. Geoff_H
    It should have the shield wired to an instrument bus via a dedicated connection. However the installer may have connection the shied to earth at the aerial. The thing to do is only earth one shield end.
  5. Geoff_H
    Brendan the shield is best earthed at the tx/rx module. The antenna end shield is best isolated from the chassis of the aircraft. If the shield is earthed at both ends you will get an earth loop current in the shield, this loop current will radiate inside the aircraft and interfere with most devices. It is also recommended to check that an accidental earth is not happening at the antenna and a solid earth exists at the rx/tx module.
  6. Geoff_H
    Check your cable shields for earthing. Must be earthed solidly, and most importantly at one end only.
  7. Geoff_H
    Not totally sure but I expect that it has to do with the on/off control circuit. The battery is one huge Capacitor. I expect that the others have a amperage demand circuit and use that to control. I think that the Capacitor one uses a simpler control circuit using the Capacitor and the resistance of the cables to the battery in an RC delay circuit that would give the frequency of the on/off operation. Why the control doesn't have an inbuilt Capacitor is don't know, but I am guessing it is to do with the size of the box
  8. Geoff_H
    I expect that the Capacitor is to give the MOSFET a voltage level at which to switch off. When the Capacitor discharges into the aircraft electrical system iits voltage will start to drop, the control circuit will see this and turn the MOSFET on. When the Capacitor reaches the voltage of the set voltage for aircraft operation the control system will turn the MOSFET off. This cycle continues as required.
  9. Geoff_H
    Another technique is the same as inverter technology. It uses switching using Mosfets. If you use resistance for control a large amount of heat will be produced. In essence the .Mosfet will switch on and when the output reaches the desired voltage the Mosfet will switch off. It does this as often as the time for the outlet voltage to drop to a predetermined value. On and off will be very quick at low power and very long at high voltage. Efficiency low at low power settings.
  10. Geoff_H
    Second sentence should read: The non permanent magnet alternator/ generators regulate the magnetic field strength of the rotating field to give a stator voltage of 12volt
  11. Geoff_H
    Not exactly the same. The non permanent magnet alternator/generators alternator the magnetic current of the rotating field. The stator voltage is then a function of rotating flux density and velocity. The relay was altering the field current. With a permanent magnet rotor the field flux is fixed, the velocity varies so the output voltage varies with rpm, so you have to convert the output voltage to 14volts (or 28volts depending on system). It is just the same as a phone charger that converts 110 or 240volts to 5/12volts automatically.
  12. Geoff_H
    Doesn't it depend upon whether the output from the alternator is below or above 14V?. I think that you are right but if you use straight resistance you may have a heat dissipation problem. Yes I agree that the oscillation frequency is high, that way only a small transformer is needed. In the 1970's I had a job that needed 5volts from a 24Volt supply. Two racks of many 2n3055's tied together, then switch mode became available, one small package 1/10 the panel space and no heat issues.
  13. Geoff_H
    If I understand it correctly the way a permanent magnet generator works is the same as a switch mode power supply. The AC voltage from the generator that will be speed dependent. This voltage is rectified and a large capacitor charged. A control circuit will turn a power transistor on and off through a transformer at a rate that will give an output at the aircraft system charging voltage the rectify this ac voltage and connect the rectified output to the system. Well in a similar way to this.
  14. Geoff_H
    I was thinking about buying an 80% complete Starlet, this would be like buying an advanced kit phone. Only 80% to go lol. So I looked at what needed to be purchased, cowling, fabric props fuel system radios paint, the 80% to go looked good. Then I priced these components, including freight, it would be cheaper to buy an already flying one.
  15. Geoff_H
    I have a Chinese lathe. A dead copy of an American lathe. However it needed adjusting of the lathe from new. The Chinese However did not know the material composition of the critical parts. A high tensile steel part was copied as mild steel, the zero backlash devise is now useless. Sorry I don't share your acceptance of the Chinese propaganda that they can make good things. Look at their NPT threads are NP no T.
  16. Geoff_H
    I would never put my life in the trust of a Chinese made product. I have too much crap that was made in China. Bought carbide tool system to curt thread on lathe. It broke 10 tips without a single pass ( some at only a few thou deep) in steel. Dis cut a thread in aluminium
  17. Geoff_H
    30 years ago I got mild co poisoning. I was the commissioning manager on a boiler plant that burnt CO to make it into CO2. The resultant heat was used to produce steam for a separate process. The plant was in the open, I wore a CO monitor. One day the CO alarm on the monitor went off, I was around 5 metres from the plant. I immediately ran in a direction away from the plant. I noticed that the reading was 100ppm. I ignored the event and continued my job. Two hours later I felt tired and decided to go home. I got more and more tired. When I got home I immediately went to sleep, I did not stir and woke up at 7am the next morning, with a headache. I was told that on the CO alarm I should have gone to first aid and sat on oxygen for several hours. So what is the flying take from this. The characteristic that one should look for is starting to get tired with muddled thinking, the get on the ground and out of the craft ASAP.
  18. Geoff_H
    An RCD, an RCCB and Earth leakage circuit Breaker are all the same device. They measure the current to the load, and the current from the load, if they are not equal the current that is different will magnetically open the circuit Breaker. Regularly test them by pressing the test button. If the current goes through you and returns through the earth there will be a residual current and trip, BUT if it goes back through the path leakage Breakers there is no residual then there is no trip. You are electrocuted.
  19. Geoff_H
    Electrocution active to neutral is not protected by an earth leakage circuit Breaker
  20. Geoff_H
    If you use an "electrician screwdriver " make sure that you test it prior to and after identifying potential on a conductor
  21. Geoff_H
    Are you saying Brown is earth? I hope that you are being facetious. Better not write that herr for fear someone may use it.
  22. Geoff_H
    Already happened at Cessnock.....well that was 10 years ago. For the way they charge it probably still is happening. Some pilots would report "Aircraft turning Base etc" no callsign. I moved my aircraft to Maitland because of the unsafe acts. I was on final when an unannounced ultralight turned onto base in front of me, no radio call. I had announce turning base.
  23. Geoff_H
    Always make a radio call, use a Qantas &^& call sign, just say "Cessna xxx" in front of it. All around know what type of aircraft, but identification is uncertain. Switch off aircraft ID before, it worked in the old days before aircraft identity systems. I believe that it happened a lot at Cessnock where landing fees were exuberant.
  24. Geoff_H
    Reports are coming in of an aircraft that landed on a Wedderburn roof, apparently at the airstrip. Ambulance rescued an occupant.
  25. Geoff_H
    No it seems to have just vanished. Good luck with the restoration. You should have fun flying her.
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