Saturday, February 5, 2011

A Break in the Weather

January was thoroughly unpleasant, and unproductive from an aviation viewpoint. N631S and I flew from the DC area to Connecticut on 3 January and then the airplane stayed parked for four weeks. One of the consequences of this hiatus was that my IFR currency lapsed. I no longer could claim the required six instrument approaches in the preceding six months. But with the weather looking good for this Friday (4 February) I needed to remedy the situation.
As mentioned in this post, the friendly folks at Volo Aviation had pulled N631S in out of the storm for the most recent weather event. I asked Andrew Post, a great young CFII at Three Wing Flying Services, to meet me there for an evening flight for which I had three objectives. First and foremost, to get me current so I could fly IFR legally the next day. Next, to shake off some of the cobwebs that would have accumulated on my flying during a four week layoff. And finally, to assure myself that N631S had come through the down period none the worse for wear.

With the cooperation of New York Approach we flew the RNAV 36 at Oxford (KOXC) and the RNAV 29 back at KBDR to a full stop. Mission accomplished in 0.8 hour. I was a little ragged on the first approach but the second was better. N631S performed superbly. Andrew was a delight to fly with and I expect I'll do so again. On landing we taxied to the Three Wing ramp and the line staff plugged in the Tanis heater to keep N631S warm overnight.

There was dominating high-pressure, and clear skies over most of the northeast yesterday so I anticipated an easy flight but a long one. The winds opposing the westbound parts of the flight would be impressive. FltPlan.com was telling me to expect 2:42 en route. That proved to be almost exactly correct.

The graphic below, from the FlightAware.com site, traces speed and altitude for the flight. You can see that during climb (at the left of the figure) speed over the ground drops to about 40 knots. N631S and I were climbing at an indicated airspeed of 90 knots. For much of the flight the ground speed hovered around 100 knots while true airspeed was about 140 knots.

But the flight, while long, was enjoyable. Flight visibility was excellent. At one point, soon after crossing the Hudson, I looked off to the south and could see the runways at Teterboro (KTEB) and Newark (KEWR) clearly. I asked the Garmin GNS-530 how far away KEWR was and it said 27.5 nautical miles. Soon (around 2130Z) a very nice sunset presented itself over Pennsylvania. (The bright spot on the ground in the picture above left is a ski area southwest of Allentown.) Darkness flowed over the landscape and the lights on the ground provided cheery company.

N631S and I were handed off by New York to Allentown and then to Harrisburg Approach and finally to Potomac Consolidated TRACON (PCT). Usually Harrisburg asks me to descend to 6,000 feet but in this case I was still at 8,000. The first Potomac controller issued the expected route change ("After Baltimore, direct Nottingham, thence direct to destination") and soon after, the expected altitude change. But with a twist:

PCT: "Skylane 31 Sierra, descend and maintain 6,000."
Me: "31 Sierra, down to six."
PCT: "Let's make it pilot's discretion descend to 6,000."
Me: "OK, PD down to 6...I believe I'll stay at 8 for a while."

This was a bit different. The controller had told me that he'd like me to descend to 6,000 feet but was leaving the timing of that descent up to me. I knew that they wanted me at 6,000 feet over Baltimore but the situation was ambiguous. When in doubt, request clarification:

Me: "Approach, Skylane 31 Sierra, when do you need me at 6?"
PCT: "31 Sierra, tell you what, cross 10 miles northwest of Baltimore at 6,000."
Me: "OK, 31 Sierra will cross 10 northwest of Baltimore at 6."

Woo-hoo! A crossing restriction! That was the first one of those I'd gotten in the 900 odd hours flown since getting my Instrument Rating. Just like the Big Guys!

Of course, if that restriction was issued to Cap'n Dave and Fi-Fi (the Electric Jet), he'd just punch a few buttons on his FMS and the computers would handle everything. I, however, needed to figure out when to start down to ensure I'd be at the specified altitude crossing the specified fix.

The GNS-530 has a vertical navigation (VNAV) function, but I don't normally use it and wasn't sure that it could deal with a descent over distance that involves a change in ground-speed. And this wasn't the time to pull out the manual.

My customary procedure for en route descents is to pitch the airplane down and accelerate to the top of the green arc (for the Skylane, 142 knots indicated airspeed (KIAS)). Soon thereafter, the descent rate settles down to about 500 feet per minute. I needed to lose 2,000 feet of altitude so that would take four minutes. The question was, how many miles would I cover in those four minutes?

The top of the green arc was about 15 knots faster than my current indicated airspeed, and the GNS-530 said that my ground-speed was 128 knots. So in the descent, my ground-speed ought to rise to about 143 knots. That's about 2-1/3 nautical miles per minute. Four minutes would eat up a bit over nine miles. A glance at the GPS display told me I was 35 miles from Baltimore. So, I could motor on at 8,000 until I was 20 miles out, then initiate the descent and level off at 6,000 feet just prior to the 10 mile mark.

Well I wasn't about to cut it that close. I waited until I was 25 miles out and called approach:

Me: "Approach, Skylane 631 Sierra out of 8 for 6."
PCT: "31 Sierra, roger."

The descent scenario played out exactly as expected. N631S and I leveled off at 6,000 feet just about 16 miles from BAL. Simple but satisfying.

To provide a nice ending for the evening, my friend Sarah was my final controller as I approached KVKX. I introduced you to Sarah in the post describing my recent visit to PCT. We exchanged pleasantries (without cluttering up the frequency) and I do not think I embarrassed myself. And, by the way, the lady gives good vectors!

The landing was uneventful, and occurred well before the arrival of today's rain event (returns from which are visible to the south in the FlightAware.com image above). As I type this N631S is snug in the hangar at Potomac Airfield. The break in the winter weather has been most welcome; it was really good to get into the air again.


Sarah said...

Aw, thanks Frank! :) I'm glad that you were able to get your plane back to VA! Working your flight was actually one of the few bright spots I had in a not-so-great day. (Nothing like getting your head kicked in every single time you sit down, then finding out that thanks to scheduling, you're the only person that can stay for mandatory overtime...thank goodness days like that are few and far between!) The weather looks gorgeous this morning...if you flew back to CT, I hope you had a great flight!

Frank Van Haste said...

It was nice working with you, Sarah. We will have to do it again some time :-)

And, yes, N631S and I are both back in CT. Nice wx and a tailwind to boot, this morning!