Planning approaches, and early warnings vs environmental snags
Murphy's law claims that if something can go wrong it eventually will, if men can plan something,whether a warning system or a instrument approach or things that look good on the surface, there is inevitably a weak point, something that in retrospect may seem simple or obvious.
The flaw in this latest warning system is said to be just computer operator error, selecting the wrong input. But in the past there have been other similar cases where the glitch was an overlooked environmental factor. Some had no harm done, but one approach error was critical.
I don't have the exact info on the first case, but it was when a type of early warning radar or something similar was set up in Alaska in order to detect Russian long range bombers which might be heading over the more direct North pole route to attack the U S. This Defense Early Warning system would have been in the post ww II days decades ago. All went well till an alert was triggered at NORAD in the middle of the night and and there may have even been intercept fighters launched. Fortunately, there was some backup check and it was quickly determined that this was a false alarm. What triggered it? The moon, hard as it may be to believe. The planners of the system had not taken into acount the effect of a full moon rising which set offf the radar or whatever powered the system.
Another error from an environmental or fact of nature was not so lucky in outcome. The airport at Eagle has an adequate runway length and width for corporate jets and airliners , but it is located in a valley with higher terrain within 5 miles on all sides. The highway runs along the river and railroad just to the north on the valley floor. Many years ago, and early version of an instrument approach was installed during the summer and seemed to work fine. It was not an iLS, I seem to recall that it was an ADF (NDB) approach. Anyway one day in imc conditions there was a fatal accident on the approach. I read the accident report at that time, seems to me it was Learjet and may have been at night in December. When the NTSB investigated they found that the critical difference between when the approach had first been installed and tested as working well in the summer and they had not taken into account the effect of having snow on ground as was the case when this accident occurred. Seems hard to believe that this could change a signal but that was the finding. I never heard of this anywhere else, but the FAA first prohibited that approach and finally removed it. I'm not sure if a vor approach came next, but I know there was not radar for a long time and now there is radar on iLS type guidance.in thinking back on this , I wonder if it could have been a Loran approach back then, I just cant recall for sure, just that snow on the ground affected the signal. This was long before gps.
