I hate to pull rank here but I doubt if any of you have designed cock pit equipment, tested it, or done a FAA flight certification submittal. I have. Let me reply, below, to points made by Jeff and Gregg.
"Collins, Jeffrey" wrote: > Group, > > I happened to be flying on United Airlines this weekend and thought I'd run > this topic by a few pilots. (I got a chance to speak with 4 pilots > separately) The consensus from the UA pilots was: > > * The stun guns have been thoroughly tested in the cockpit and had no effect > on the avionics systems. > > * Type of stun guns( Taser only) would be the type that shoot the electrode > through the air at the target. > > * They all preferred hand guns with bullets over the Tasers. They all claim > that tests have been done unloading > several rounds of bullets into the fuselage of an aircraft at critical > altitudes without having severe affects. I am in total agreement. High Voltage guns, whatever you call them, deliver a high voltage at a very low current. I have not tested with Tasers but I have done ESD. Tasers are roughly equivalent to an ESD test. ESD Tests showed occasional minor damage to microphones, particularly those mounted on the wall to the side of the pilot or the autopilot might disengage if the yoke were zapped. Pilots are trained for autopilot disengagement. Redundancy was tested in many ways. One was to shoot virtual bullets at equipment. Virtual paths were selected at random. All equipment in the path was suddenly turned off by tripping the breakers. No single virtual bullet ever effected the flyability of the airplane. Two bullets on opposite sides of airplane could be troublesome but probably not fatal. All tests were conducted using simulation on the ground. L > > > The field of my survey was small and only targeted a single airline so I > don't know how this would correlate across the entire pilots union. Just > thought I'd share this piece of info for what its worth. > > Regards, > > Jeff Collins IGregg Kervill wrote: > Dear All, > > Many thanks for your comments - I think it may be worth making some comments > in summary: > > 1- Lightning has the same effect. Disagree - lightening is an external > effect - Physics 101 and the "Ice Pail" experiment. If anyone doubts the > difference go and visit the Munich Science Museum where every day (I think > they still do it) a volunteer climbs into a metal 'pod' and is winched > between two electrodes (about 20 feet apart) and becomes part of the > discharge path. Seeing it sure beat reading about it at school. Any > discharge on the inside of the "Ice Pail" is transferred 'instantaneously to > the outside surface - this is, after all, the principle upon which the Van > de Graff(sp?P generator is based. (Note the volunteer does NOT wave out of > the window!!!) You are partially correct. Lightning is a much bigger problem. The "E" field is external to the airplane. The "B" field enters the airplane and penetrates most shielding and therefore is internal. Stun guns are mostly a "E" field problem. The "Ice Pail" shows immunity to "E" fields. The same is true of the cockpit equipment. It is almost perfectly contained within ice pails called ATR boxes. The same protection is afforded to stun guns. ATR boxes usually do not protect against "B" fields making lightning the bigger problem. Because lightning is not a question of "IF", but rather of "WHEN", and because lightning is bigger problem, equipment is designed to survive lightning. > > > 2- Holes in structure versus hole and carriers in semiconductor > substrates > (yes it was a pun). I agree with those who preferred the idea of perforated > eardrums (depressurization) to perforated electronics. > > 3- Dead Pilot versus Dead Electronics. Neither is ideal - but many (most) > commercial aircraft are fly be wire - One of my clients make Simulators - > and I flew (for the first time ever) and Air Bus (simulator) from London > Heathrow to London Gatwick - Landed (ON THE RUNWAY) and taxied (the most > difficult part) to the airport. I had full control of the simulator and was > flying by instruments. The controls are ALL electronic and if there had been > multiple (i.e. non-random) fails then even a pilot would not have been able > to move the control surfaces. I'm not sure what your point is here. Air Buses use fiber optics for most flight critical systems. > > > 4- Testing - at 50kV????? any comments from ESD engineers out there????? My tests only went to 25KV. I think it largely a matter of current which is determined by the size of the storage capacitor, more than the voltage. > > > 5- TASER versus Stun gun - thanks for correcting my misunderstanding - > Two > comments - First - if the stun gun is discharged through the airframe there > will be an induced potential in local electronic systems. Correction. There will be an induced current. The potential will be almost zero across the very low resistance of airframe. > Second - if I must > turn off my tape recorder (powered but a single AA cell) because it may > affect systems then how is discharging 50k considered to be safe and OK??? It may interest you to know there is no FAA requirement to turn off your tape recorder. Instead the FAA allow airlines to set their own rules. You can not prove the negative case of never, ever causing a problem but I have never seen a documented case of a problem (to flight systems) caused by a tape recorder or even a cell phone. I think the reasoning of most airlines is to error on the side of safety. Besides without the earphones in your ears you can hear the crew instructions. > > > 6- Design of interfaces to cope - some of the prototype systems that I > did > safety and reliability work on in (1995)uses surface mount components to > provide lightening protection - these devices would not provide Creepage > distances of more than a couple of millimeters. I'm not sure what your point is here. SMD does not relate to safety and usually has better reliability. > > > 7- Ground computers - I agree that this is worrying - the UK has even > more > out of date equipment and then the new system (that will control air traffic > in the South of England) used equipment (and software) purchased in the late > 80's early 90's. I just hope that it still works when they take it out of > the box. The point is that RANDOM failures exist and there procedures have > been developed (and practiced) to deal with them. Anything that induces > non-random and multiple failures is - I suggest - another ball game. > > 8- The chances are low - I agree - I was flying back from the west coast > the > morning of 9-11 and I did not get a warm fuzzy feeling about probability > when I watched the news footage - but I have made many flights since and it > will not stop me from flying. I am grateful for the fact that Europe and the > middle East are sharing their security experiences with the US. Security is > a cultural thing and the US has a long way to go before it provides the same > level of security from officials AND MORE IMPORTANTLY from passengers. I strongly agree. Fred Townsend > > > These are Gregg's four pointers to improve security at ZERO cost: > Security guards most NOT walk around together. > ALL alarms must be investigated by security (a telephone call saying OK - is > negligence). > ALL unattended baggage MUST be treated as a bomb. > ANYONE asking me to "keep and eye" on their baggage will be told to take it > with them or I will report it as a bomb. > > Security is the responsibility of everyone that flies - Please help to keep > me safe and I will do my best for everyone else. > > Best regards > > Gregg > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
