Sunday, March 20, 2011

Are We Having Fun Yet?

Friday's flight from KBDR to KVKX was not a great example of the joy of aviation. For the first couple of hours of the 2.8 hour trip N631S and I got to experience strong headwinds and fairly continuous light turbulence. Nothing nasty, just tedious and uncomfortable.

The wind field forecast by XM Weather on the Garmin GPSmap 396 for 9,000 feet (left) showed about 50 knots pretty much right on the nose. At our assigned altitude of 8,000 feet it was a bit better, but I was still getting a ground speed about 45 knots less than N631S's true airspeed.

A few minutes after snapping that screenshot this conversation occurred on New York Approach's frequency:

FlightStar 36: Approach, FlightStar 36 would like to descend to 6,000 to get out of this scattered layer. It's pretty bumpy in here.
Approach: FlightStar 36, descend and maintain 6,000.
FlightStar 36: FlightStar 36, down to 6,000. Thanks.
N631S: Approach, Skylane 631 Sierra.
Approach: 631 Sierra, go ahead.
N631S: Any chance of 31 Sierra getting 6,000 too?
Approach: Noooo. Not 'til you get down near Solberg. Will that be what you're looking for?
N631S: Actually, 31 Sierra would like direct LANNA and a descent to 6,000 as soon as those will work for you.
Approach: Well, you can go direct LANNA from there. Join Victor 30 and I'll get lower for you when I can.
N631S: 31 Sierra direct LANNA. Thank you sir.

The early turn to the south toward LANNA intersection pointed me toward lower wind speeds, and after only about 10 miles Approach gave me a descent to 7,000 feet and a few miles later to 6,000 feet. At that altitude the ride was a bit better and I picked up 8 or 10 knots ground speed.

Later as we approached Potomac Airfield from the east shortly before sunset, the combination of sun glare and haze made visibility a real challenge. The final controller had descended me to 2,000 feet and turned me toward the airport, asking that I report the field in sight. I did so, and received clearance for the visual approach to KVKX with the usual option to cancel IFR in the air then, or to wait until I was on the ground.

Now, I just about always cancel in the air. But this time I didn't - not right away. If any of my friends from the Mt. Vernon Sector of PCT are reading this, I'd like to offer a few words of explanation.

When I reported the field in sight, I wasn't fibbing. I could see prominent features that I know are associated with the airport. But with the challenging visibility I didn't feel certain that I'd be able to keep the field in sight. Landing was not, as they say, assured so I chose to stay in the system.

But as I descended below the floor of the Class Bravo airspace, to about 1,400 feet, I passed below the base of the haze layer. In seconds, visibility about doubled. I went back over to Approach frequency and cancelled IFR.

And that's the answer, if you were thinking, "What the %#!! is he doing?"

When I left Connecticut on Friday I thought the weather forecast for Monday looked quite promising for a return flight. As of now (Sunday afternoon) it isn't so hot. A fast moving low pressure system will be sweeping across the northeast early on the first full day of spring, bringing clouds, light rain and low freezing levels. So I'll be with AmTrak tomorrow morning and will be happy when we finally get back to consistently warm weather aloft.


Royski said...

I was flying Friday and noticed a low-level wind shear advisory in the area around VKX. I've never flown in a mountain wave, but flying back to VKX from Richmond early that afternoon it felt like one - a few minutes of pulling back on the yoke to keep altitude while loosing airspeed, alternating with opposite.

Frank Van Haste said...

Hi, Royski!

It's easy to look at the wind charts and fall into the subtle trap of thinking that they depict a two-dimensional vector field. But the map is not the terrain!

Often (and certainly last Friday) my autopilot will remind me of the z-axis. As I fly into a region of descending flow, N631S has to fly "uphill" to maintain the pre-set altitude. Pitch increases a bit, TAS falls off 4 or 5 knots, and the annunciator asks for nose-up trim.

Then, invariably, a few miles down the airway we'll cross into an area of rising air. Pitch decreases, the airspeed recovers, and the annunciator calls for nose-down trim.

These phugoids are most noticable, for me, flying into a stiff headwind. More than once I've been prompted to scan the power setting indications with extra care to make sure I haven't messed something up.

It's fun to watch Mother Nature at work!

Thanks for reading and commenting.