June 2010 NOT ALL THAT long ago even the best full-motion jet simulators had very basic visual presentations that were restricted to nothing more than a view straight ahead through the windshield.
Most simulators had a television-style screen mounted in each pilot’s windshield, and you couldn’t really see anything except the display on your side. And there were no visual displays for the cockpit side windows. It was the best technology the 1970s and early ’80s could provide.
This straight-ahead view only, with no peripheral clues — plus the lack of texture and detail in the only visual display available — made it very difficult to control the simulator flying visually. Because of the lack of details on the single-window visual displays, most pilots would do a perfectly fine job of flying the instrument approach procedure down to minimums, and then would wander all over the place once they looked up and tried to complete the landing.
What these simulators taught you with their limited visual cues was to not look up, at least not on an ILS approach. If you just kept your eyes on the instruments and tracked the ILS signal all the way to the runway, everything worked out fine. That was not the intended lesson, but that’s how you learned to get through simulator training.
Though the simulators lacked realism, they unintentionally reinforced a lesson all instrument pilots need to learn, and that is that the visual segment at the end of every IFR approach can be very difficult and, because you are so close to the ground, is very risky.
Today’s full-capability Level C and D simulators have excellent visual displays that wrap around for nearly a 180-degree field of view. The images on the displays are detailed with texture in terrain and even pavement, so our eyes can detect distance and relative motion. And most importantly, the images accurately portray visibility reduced by precipitation and fog so that you can never really get a crystal clear view of the runway all the way to touchdown when visibility is low.
Flying a modern simulator visually is realistic, and the fidelity of these simulators is one of several reasons the safety record of the jet pilots who train in them regularly is so good. When jet crew members encounter minimum visibility conditions at the end of an approach, it looks familiar because they have been there before in the sim.
The situation for the pilots of piston-powered airplanes, and other airplanes that cannot support the multimillion-dollar expense of a full-capability simulator, is not so good. The simulators for piston airplanes that do exist can’t match the visual authenticity of the jet sims, so training in them is better than not but still doesn’t match actual conditions.
Learning to fly IFR, and then practicing approaches under a hood, is totally useless in preparing a pilot for that final visual segment of an approach and landing in real instrument meteorological conditions (IMC). The hood limits your view, forcing you to fly by the instruments until reaching the end of the approach procedure, and then you take off the hood and are in instant VFR. Mother Nature doesn’t work that way. The irony is that instrument approaches end with a scud run to the runway, sometimes in very reduced visibility with a low ceiling.
What The Rules Say
The FAA is well aware of the risk involved in the visual portion of instrument approaches and has made rules to try to minimize the hazard. FAR 91.175 is one of the longest rules in the book and describes the conditions under which a pilot may descend below the minimum descent altitude (MDA) or decision height (DH) during an instrument approach.
Many IFR pilots get wrapped up in the list of features that must be clearly visible to continue down from decision height on an ILS approach, and that is important, but the more fundamental requirements for descent are summarized at the very top of FAR 91.175. That part of the rule demands that we do not descend below minimum authorized altitudes unless the runway is clearly visible and that, at all times, the airplane is in a position to make a normal approach and landing without need for unusual steep banks or dives.
As is often the case, the FAA rule writers don’t always talk to each other. The guys who laid out the basics of FAR 91.175 many years ago were dealing in common sense. The last thing any pilot should do is be yanking and banking in low visibility while flying close to the ground. That is obvious.
The other part of the FAA rule-making process, the group that lays out the requirements for instrument approaches, ignores FAR 91.175 in some cases by establishing minimum altitudes and decision points from which you cannot reach the runway without radical and unusual maneuvering.
For example, at Williamsport, Pennsylvania, the minimum visibility requirement for the localizer-only approach to Runway 27 is one mile, pretty typical for a straight-in nonprecision approach. However, the minimum descent altitude is 1,400 feet above the runway. So if you see the runway clearly at one mile, as the visibility minimum allows, you need to descend 1,400 feet in a mile. I don’t know of any normal airplane that can lose 1,400 feet of altitude in one mile without the extreme maneuvering the FAR 91.175 outlaws.
Williamsport is a radical example of how impossible it can be to get down to the runway from the minimum descent altitude, but it is not alone. A more typical example would be to have a visibility minimum of one mile with the MDA at 500 or 600 feet above the runway. To transition from level flight at the MDA to a normal approach to the runway that requires descending 500 feet in just one mile is a challenge. If you have a groundspeed of 90 knots, you will cover the distance to the runway in about 45 seconds. That translates into an average descent rate of about 750 fpm. That is a pretty high descent rate close to the ground while flying with only a mile of visibility.
The point is that what is legal in terms of the minimums on the chart might not be legal in terms of FAR 91.175 and its requirements for a normal visual approach to landing. And what’s legal may not always be wise. It’s vital to understand that there is no margin built into the minimum altitudes and visibilities on an approach, particularly a nonprecision approach.
