A high-performance single is proceeding to the Linden VOR for a full VOR-B approach to Virginia’s Front Royal-Warren County Airport. The instrument flight instructor has just advised the pilot/owner, who is undergoing an instrument proficiency check in actual instrument conditions, to allow some airspeed margin for a sudden, unexpected accretion of rime that began during the descent.
A brief discussion follows. The pilot normally flies approaches in the 140-knot aircraft at 85 to 95 knots. From past experience, the pilot has developed deep respect for icing of any type or extent; one lesson about that came long ago from a drop-in landing that happened at a surprisingly high airspeed. Of the many learning experiences accumulated over years of flying, that one had been among the most vivid, especially for a pilot well-read about airframe icing who had thought himself knowledgeable enough to avoid any such occurrence.
Well, he wasn’t the first "expert" ever humbled by an icing encounter. And here was a chance for redemption.
Not only would he fly the approach flaps-up, he informed the CFII, but he would maintain a generous airspeed margin at every phase while remaining poised for any sign of buffeting or icing-induced control decay.
"No more than 120 knots, please," said the instructor.
Why the limiting-airspeed?
Visualizing the flight’s next few minutes, the pilot could see the awkwardness of the piloting scenario he faced.
With a final approach course defined by Linden’s 335-degree radial, the angle between the course and Runway 10/28 demands considerable maneuvering to circle-to-land in either direction. Excess speed would be a liability. Also, the minimum descent altitude, 3,300 feet, leaves an aircraft at a lofty height above the airport’s 704-foot field elevation. (Note that the altimeter setting for the approach comes from Winchester, about 18 DME away along the ridge line to the north.)
At a more capacious airport, a fast approach would pose no problem. But here, given the growing list of constraints and conditions, the 3,007-foot-long runway must also be considered a factor, even more so if it is wet.
Reviewing the plate, the pilot now recalls that the instrument approach is only authorized for approach Category A or B aircraft. As Page 4-8 of the Instrument Procedures Handbook explains, an approach in Category B aircraft must be flown at less than 121 knots, as the CFII reminded him.