Here's more of the citation from the article:
If the airport doesn't have a published approach, ATC isn't required to include a minimum altitude in the clearance. "Cruise 6,000 to the XYZ ranch" is all the pilot will probably hear. In this case, determining the applicable MIA is the pilot's responsibility. The Aeronautical Information Manual's pilot/controller glossary defines the MIA as the minimum altitude prescribed in Part 95 (airways and routes) or Part 97 (standard instrument approach procedures).
These regulations apply only if a pilot is flying along an airway or an instrument approach. When he flys off these routes, a pilot reverts to Part 91.177(a)(2), which requires him to fly at least 2,000 feet above the highest obstacle within four nautical miles of his course in mountainous areas, and 1,000 above the highest obstruction within four miles in other areas. But how is a pilot supposed to determine obstacle clearance when he's flying off-route?
Until recently, IFR low-altitude enroute charts didn't provide off-route obstruction clearance altitudes (OROCAs). A pilot flying off-route had to determine his MIA using the maximum elevation figures (MEF) on a sectional chart. There was some question in many pilot's minds whether this was legal, but the FAA Certification Branch in Washington says it is-if the pilot uses a current sectional chart.
Let's plan a cruise clearance to the El Coyote Ranch airport, shown in Figure 1, which is part of the L-16 low altitude enroute chart. El Coyote Ranch is 42 miles north of McAllen, Texas and in a box defined by 26 and 27 degrees north latitude, and 98 and 99 degrees west longitude. The large 182 in this box is the OROCA. It's high because of the nearby radar balloon.
Obviously, getting an IFR cruise clearance at El Coyote Ranch is going to be useless unless a pilot uses the corresponding, current sectional chart. El Coyote itself is within by a smaller lat/long quadrangle, and its minimum safe altitude- 900 feet (09)-is a lot lower. This doesn't mean an IFR pilot can fly that low.
IFR chart MIAs include the 1,000- to 2,000-foot obstacle clearance buffers. Sectional chart MEFs don't do this. The pilot must add the appropriate buffer to the MEF. In this case, he couldn't cruise below 1,900 feet unless he's in visual conditions. If the pilot has any doubt about his ability to stay within the lat/long box, he must refuse the cruise clearance and go to another airport.
To increase safety, cruise clearances and MIAs should be part of a pilot's preflight planning because in flight it's easy to misread obstruction altitudes if you're distracted by turbulence, weather, and other IFR duties. Because a pilot must know before departure which destinations have instrument approaches, he has little excuse for not being prepared.
