[QUOTE=user_hostile]
Is that because accidents would be too infrequent to justify the cost of implementation? Or do you mean something else?
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The FAA hase been accused of ‘tombstone rulemaking’, which means that they don’t make a rule until enough people have been killed. One example I can think of just off the top of my head concerned new rules put into force after a Piper Archer collided with a DC-9 over Cerritos, CA in 1986. While this one crash did not trigger the new rules (requiring TCAS in commercial aircraft and Mode-C transponders in GA aircraft operating in areas of dense traffic), it contributed to them. In 1978 a Boeing 727 collided with a Cessna 172 in San Diego. This resulted in a TSRA (now Class B airspace) around Lingbergh Field.
On the other hand, mid-air collisions are rare. TCAS, Mode-C, Class B airspace, etc. make the areas around airports much safer for aircraft operating in their vicinities, but once you get away from airports (places where traffic is expected to be more dense) safety depends more on the vigilance of the pilots. This is especially true for helicopters, which operate under slightly different rules from fixed-wings. I could look up the specific rules in the FARs, but the basic rule is ‘don’t run into anything’. Helicopters tend to follow roads – keeping the roads to the left. This helps to reduce the possibility of head-on collisions. Helicopters are also expected to keep in touch with each other outside of ATAs. Within Class D, C or B airspace they’re on the tower frequency; but outside of controlled airspace helicopter pilots will switch to the air-to-air frequency and give position reports. For example, ‘Helicopter 4-0-0-0-Niner, westbound Simi, two-point-one.’ (‘N40009 is flying westbound on the right side of the 118 freeway at 2,100 feet.’) It works pretty well.
But then you have congregations of helicopters, such as when they are covering a news event. Often this is outside of controlled airspace (or usually, Class E airspace) where separation is not provided for VFR flights. It’s up to the pilots to not run into each other.
How would the FAA control the airspace? Class D airspace is what you find around municipal airports. They have their own workloads there keeping aircraft separated in the pattern and being aware of traffic within 5sm. Also, they might not be able to see low-flying helicopters at a distance. Raise the minimum altitude for helicopters? That would put helicopters, which often fly relatively slowly, in the same airspace as faster fixed wings. (For example, a Robinson R-22 might be cruising around at 70 kts while a Cessna 172 might be doing 120 kts.)
So given that mid-airs are rare, and that instituting new rules would be impractical for a problem so rare, I don’t think the FAA will see any need for rulemaking.
