Tuesday, May 8, 2012


When N631S and I left KBDR at about 20Z last Friday for our weekly flight down to the DC area there were a number of indications that convective weather might be a factor. Earlier, a SIGMET had been active over eastern Pennsylvania for a line of thunderstorms in the York – Harrisburg area, but those seemed to be dissipating. And the 18Z Terminal Area Forecast (TAF) for Washington's National Airport (KDCA) indicated that some thundershowers might show up:
TAF KDCA 041726Z 0418/0518 00000KT P6SM SCT045 SCT100 OVC140
FM042300 28006KT P6SM VCTS BKN050CB BKN150
FM050100 31006KT P6SM BKN050 BKN150 
FM050900 35007KT P6SM SCT050 BKN150 
FM051600 02009KT P6SM OVC050=
The "VCTS" means "thundershowers in the vicinity" – normally, within five to ten miles of the field. I expected to get to Potomac Airfield (KVKX) about 2230Z (i.e., before the thundershowers were forecast) but the destination weather would bear watching.

And in fact, there was no weather worth mentioning for the first 90 minutes or so. That's about when N631S and I were passing Lancaster, PA and entering Potomac Approach airspace. Looking at the NEXRAD weather depiction down the road, I saw that a cell was working over KDCA and heading eastward toward KVKX. I hoped it would move on to the east fast enough to be a non-factor for my arrival.

Passing Baltimore, I picked up the METAR for KDCA to see what conditions were like:

METAR KDCA 042152Z 18012KT 10SM FEW040 BKN110 BKN200 26/16
 A2990 RMK AO2 WSHFT 2121 TSB10E30RAB13E32
 SLP125 VCSH S CB DSNT S MOV E P0000 T02560156=
The METAR indicated that the big airport was having good weather, but that a thunderstorm had begun at 2110Z and lasted until 2130Z. The associated precipitation had begun at 2113Z and lasted until 2132Z.

The weather observer saw showers to the south, and cumulonimbus clouds to the distant south with cell movement to the east. The NEXRAD base image at left (click to enlarge) is from about the same time. There were a couple of cloud-to-ground lightning strike returns. The red line is the route I would normally get from ATC, south from Baltimore to the Nottingham VOR (OTT), departing thence on a 250° heading then turning toward KVKX for a visual approach. Given the current conditions, I didn't think that would be a great plan.

As I pressed on I could see the cell clearly to the south. (I wish I had a photo for you, but I was a little busy...) I didn't want to dive into the cell and try to find KVKX visually...and I wasn't thrilled with the prospect of the RNAV Rwy 6 instrument procedure either, as it would involve passing through the cell to approach the field from the southwest. Of course, I had lots of fuel so I could just ask ATC to send me somewhere to hold for 45 minutes or so while the weather cleared the area. But...looking over to the west, I could see that Andrews AFB (KADW) was in the clear. And knowing where KVKX was relative to Andrews, I could see that it was emerging from the rain. So I keyed the mike:

N631S: "Approach, Skylane 31 Sierra, request."

PCT: "31 Sierra, go ahead."

31S: "Can you turn me west right along the south boundary of Andrews? That's in the clear and I can make a left-base visual approach to VKX."

PCT: "OK, I have your request."
Not more than two minutes later, the controller came back with:
"Skylane 31 Sierra, steer heading 195. I have to keep you going south a little further, but the supervisor is talking to Andrews about your request. I think we can work this out for you. Meanwhile, descend and maintain 3,000."
I gave him a "wilco" and started a fairly rapid descent. Before I got down to 3,000 the controller cleared me down to 2,000 and turned me to the west. And after a couple of miles it was, "Cleared for the visual approach to VKX." The image at left shows the the weather situation as I approached the field and the routing that Potomac Approach and Andrews Tower arranged for me. (Again, click to enlarge.) Have I mentioned that I love Air Traffic Controllers?

I descended to 1,500 feet and as N631S and I were crossing just south of the arrival ends of Runways 1R and 1L at KADW I said to the controller, "Please pass my thanks along to Andrews Tower. I appreciate their doing this for me." At that point, all that was left was a 30° turn to the left and a three mile straight in visual to a dry Runway 24.

Just for fun, here's the track of the last few minutes of the flight, courtesy of FlightAware.com. The weather depiction in this image is from 2130Z, about 50 minutes before N631S and I landed.


Anonymous said...

Great poast, Frank. And one more proof that the professionals at ATC are doing their very best. I guess the A-#1 rule remains in place: Talk to them and keep them informed about your route and enroute needs. If they KNOW what you are thinking, they will try to make it work for you. Their second-worst nighmare is a pop-up with no skill and assumes that the is the only airplane flying. Great lesson, sir. -C.

Anonymous said...

Make that 'post,' please. -C.

Frank Van Haste said...

Thanks, Craig. I've never understood pilots who are reluctant to talk to ATC. Getting you and you're airplane on the ground, at the intended destination, and in a condition that allows for future flying, is a team effort...there's really no such thing as 'solo'.



Peter said...

This post really underscores the benefit of you (the pilot) speaking up to let us (ATC) know what you need. Just because what you wanted -- the Andrews flyby -- isn't what's normally done, doesn't mean it can't be done. On our end, it's usually a straightforward matter of hitting a button on our voice switch to call up the tower and coordinate your request. Granted, we can't always work things out the way you like, but if you let us know with enough time, often these types of things are possible.

The worst response you'll get is "Cessna 61S, unable due to traffic at Andrews" ... and hopefully followed by an alternative plan of action. Because believe me, I try to keep pilots as far away from thunderstorms as I can. The last thing I want is to watch you barrel through the middle of a cell because the "only option" was the RNAV approach.

Gary said...

Excellent post,. Communication and working a plan together with ATC. Working your "plan B" makes this happen. Good lesson for all pilots!

Frank Van Haste said...

Gary, thanks for stopping by. Yes, I'm a big proponent of "working together" with ATC.

Peter, thanks to you, too. You folks are the BEST. As I noted in the post, I was good on fuel so the fallback was to go and hold someplace (I was NOT going through the cell). Best safety feature on my airplane is long range tanks with 6 hrs. of fuel!