archive‎ > ‎air‎ > ‎articles‎ > ‎

Demi Demy

posted Apr 17, 2011, 2:36 PM by George Finlay   [ updated Apr 17, 2011, 2:36 PM by Nathaniel Cauldwell ]

Steve Demy flies a Columbia 300 based near Vancouver BC, and relishes the challenges of long flights. He watches the wind aloft and meticulously plans ideal altitudes as well as fuel and prop settings. He has regularly made non-stop Vancouver-Toronto trips, a distance of about 1800 nm.

Today I departed Bend OR in a new Columbia 400, N1134N, bound for N07 eventually, in Lincoln Park NJ, where the TKS anti-ice system is scheduled to be installed. With tailwinds forecast to be 75 knots or better, and icing airmets below 18,000 ft enroute, I chose FL250 as cruising altitude, both to take maximum advantage of the tailwind, and to stay well above clouds that might contain ice.

It worked out well. Five hours after departing at about 0945 PDT, N1134N touched down in Madison WI, (KMSN), having covered about 1400 nm on 88.5 gallons of 100LL. The wind held up at 75-85 kts on the tail, gradually diminishing and backing around from west to southwest, allowing us to average about 280 kts groundspeed. It was my demi-Demy leg. I suppose I could have stretched it for another hundred miles or so by throttling back. But my aim was different than one of Steve’s record attempts. I just wanted to get well clear of the mountains, and more than half way to my destination.

Weather was as forecast, with a broken to overcast layer below from Oregon to the Minnesota border, smooth to light turbulence, and almost exactly standard ISA temperature at FL250, -36 dC. Onboard weather data showed two quasi-stationary/cold fronts, one roughly paralleling our course to the north, the other to the south. East of the South Dakota/ Minnesota border, the undercast disappeared, replaced by a thin overcast above. That layer dissolved near Minneapolis, just before we crossed the area where the charts showed we would be expected to cross the benign cold front.

Over the Rockies, one’s thoughts turn to tactics to deal with the unlikely possibility of diverting to a high elevation alternate in response to a system problem. The topographic information provided by the Garmin G1000 MFD helps one picture the situation below, with a precise digital readout of maximum and minimum elevation within the selected range, along with a black bracket to reinforce the same data graphically on the legend, and a white horizontal line against the blue color representing the sky to show your altitude relative to the terrain below.

Performance figures, noted at two points enroute:

March 17, 2009 1720Z

MP 31.5 inches
RPM 2480
FF 16.0 gph
TIT <1615 dF
EGT <1575 dF
CHT <340 dF
OIL TEMP 171 dF
OIL PRESSURE 45 psi
TAS 210 knots
IAS 140 knots
GS 280 knots
FL250
OAT -36 dC (IAS -1 dC)

March 17, 2009 1900Z

MP 31.5
RPM 2480
FF 16.8
TIT <1625 dF
EGT <1585 dF
CHT <360 dF
OIL TEMP 176 dF
OIL PRESSURE 43 psi
TAS 218 knots
IAS 148 knots
GS 290 knots
FL250
OAT -36 dC (IAS -1 dC)


Comments