Tuesday, April 24, 2012

Interesting at Both Ends

The flight yesterday morning from KVKX in the DC area to KBDR in Connecticut was interesting from start to finish...except for the middle, which was uneventful. The departure was interesting due to the potential for icing (in late April!) and the arrival was interesting due to the approach conditions.

On Sunday I paid close attention to the forecast for temperatures aloft at 11Z the following morning (my planned departure time). Notably, the 0°C isotherm would be running just about north to south over the DC area at 3,000 and 6,000 feet. This was the leading edge of a vast pool of frigid air being rotated cyclonically around a deep low pressure center that would be over northern New Jersey (see the (click to enlarge) chart above left, a surface analysis for 7 AM EDT on Monday).

So a successful departure would involve staying low and dashing to the east with the expectation of finding considerably warmer air over the DelMarVa peninsula. Then I could climb to a reasonable en route altitude (I'd filed for 5,000 feet).

The next morning the surface temperature at KVKX was 40°F (about 4.5°C) when I got there at 0600. By 0700 N631S and I were at the hold short line for Runway 24 and I called Mount Vernon Sector for my release. They gave me four minutes to be off and stipulated, "Climb and maintain 2,000 feet; enter controlled airspace on a heading of 180°." We were off.

At 2,000 feet the outside air temperature (OAT) was 34°F as the Potomac TRACON controller said, "Cessna 31 Sierra, turn left heading 090, climb and maintain 3,000." My reply was, "Potomac, 31 Sierra left to 090 and I have a request on the altitude."

She asked me what I'd like to request and I said that I was in IMC and just about at the freezing level – so could I please continue to the east at 2,000 until I reached some warmer air. The controller cleared me to maintain 2,000 feet and said I should let them know when I wanted higher.

As I approached the western shore of Chesapeake Bay (by this time cleared direct to the Smyrna VOR (ENO)), the OAT was up to 37° so I requested 3,000. The temperature there was 35° and I could see that a few miles ahead there was a gap between layers with the overcast well above me. Since it would be nice to have some additional altitude in the bank crossing the Bay, I asked for and got my final altitude of 5,000 feet. At top of climb the temperature was still in the mid 30's and from then on it just got warmer.

I'd pulled ahead of the advancing cold air, and soon N631S and I were on top in the relatively warm sunshine. This was the uneventful "middle" of the trip, so I could use the time to plan for the arrival at KBDR. I'd had a look at the weather Bridgeport was reporting prior to departure; it had been moderate visibility in mist and a 500 foot overcast ceiling with light winds out of the northeast. The ILS approach for Runway 6 would be on offer so I dug out the approach plate and clipped it to the yoke. Then I pulled up the latest METAR and got a bit of a surprise. The ceiling had lowered to 300 feet:
KBDR 231049Z 02012KT 10SM OVC003 11/08 A2919 RMK AO2 RAE0956
The Decision Height for the ILS Rwy 6 at KBDR is also 300 feet...so unless things improved this approach would be to minimums. That was fine, but I'd be a lot more relaxed if it was a couple hundred feet higher!

N631S and I continued north along airway Victor 16 toward JFK, helped along by a nice tailwind that kept ground speed up around 155 knots. Another METAR came up about 1200Z:

KBDR 231152Z 15008KT 8SM OVC005 12/11 A2922 RMK AO2 SLP894
OK, better. The wind, still fairly light, had veered to the southeast (150008KT) and the overcast was up to 500 feet again. I relaxed and picked up the ATIS broadcast (which was by now in range). It confirmed the numbers from the METAR and added, "ILS Runway 6 in use, landing and departing runways 6 and 11." That meant a "circle to land" option was available.

"Circle-to-land" is used when approach conditions dictate use of an instrument approach to a runway that is not suited for landing. This could be due to adverse winds, or to a runway closure. Approach plates have separate minima for straight-in and circling conditions, the latter being a bit higher.

A "circle-to-land" approach can be tricky, depending on conditions. You're maneuvering, usually well below normal pattern altitude and often just below an overcast. It might be windy, it might be raining, it might be dark. There have been nasty accidents and many air carriers restrict the use of circle-to-land in their procedures. It's really a rather rare event – as of yesterday I had never made use of circle-to-land.

Checking on with the final New York Approach controller, I said, "New York Approach, Cessna 631 Sierra, level 3,000, 'Papa' at Bridgeport." and he said, "Cessna 31 Sierra, Bridgeport altimeter is 29.22. Will you want the circle to Runway 11 or the straight in?"

I was all set for that question. With the wind from 150° at 8 knots it was a direct crosswind well within N631S's capability. I saw no reason to mess about with the circling approach and told him I'd take the straight in.

A couple of minutes later, I was in the clouds at 2,000 feet above the Sound and approaching the localizer. Approach cleared me for the ILS and handed me off to Bridgeport Tower with whom I checked in: "Good morning, Bridgeport Tower, Skylane 631 Sierra on the ILS 6, 2 miles outside STANE, inbound for landing." The tower controller then threw me one more curve.

"31 Sierra, Bridgeport, report STANE. The wind has shifted to 170 at 9 knots, I was going to offer you circle to Runway 24...do you want that?"

I thought about that as I continued down the glide slope. A wind from 170° was beyond a direct crosswind and would give me a tailwind component. A slight one, but even so... I didn't yet know where I'd break out of the overcast; circling at 300 or 400 feet was not an attractive proposition. So I said to Tower, "I'd like to decide when I break out, depending on conditions."

He responded, "OK, that should be about three miles out, let me know your intentions." "31 Sierra, Roger."

At the end, I descended out of the cloud base at about 600 feet, into good visibility. I told the tower, "31 Sierra will circle to land 24."

"You can circle North or South, your choice."

"31 Sierra will circle south of the field." Circling to the south resulted in essentially making "left traffic"; this made it easier to keep the runway in sight at all times. And so I motored around at 500 feet altitude, which made for an interesting view. The only "burble" came when I turned to the North (essentially, turned onto base) and went from 10° to 20° of flaps. The added lift (along with some inattention on my part, I fear) popped me up into the base of the overcast. I quickly pulled some power and pitched down to stop the unintended climb, and got back down into the clear. A good lesson on how circling approaches can quickly become "interesting."

The subsequent landing was routine, and I got to log another 'first', a circle-to-land approach.

1 comment:

Cedarglen said...

Thanks, Frank. An outstanding post. It is refreshing to hear about ATC being so responsive to a 'small' guys needs and plans. Obviously, you were on top of every inch of this flight. Happy Landings. -C.