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Monday, January 28, 2013

A Fairly Bad Week (Part 2 of 2)

As mentioned at the end of the previous post, the forecast on Friday morning foretold a large ridge of warm air arriving in the East, bringing rain but no risk of icing.
The low centered over Chicago at 12Z (left) was headed eastward with it's associated occluded front at roughly the speed of a runaway freight train. I could expect a long, hard slog against stiff headwinds for the westbound portions of my trip and anticipated that ceilings and visibilities would deteriorate some time after 00Z, making an early departure advisable. The computer was telling me to anticipate about 2:40 enroute so I planned on a 20Z departure to be in the DC area well before 23Z. The relevant Terminal Forecasts (TAF's) reflected these expectations:

TAF AMD KDCA 111844Z 1119/1218 21005KT P6SM -RA OVC028
FM112200 16006KT 3SM -RA OVC015 
FM120000 17006KT 2SM BR OVC008 
FM120600 00000KT 1/2SM FG OVC003 
FM121500 11003KT 5SM BR BKN015 OVC035=

TAF AMD KADW 1120/1223 16009KT 9000 -SHRA SCT010 OVC014 WS020/21042KT QNH3004INS
TEMPO 1121/1202 3200 -SHRA OVC009
BECMG 1205/1206 23006KT 3200 BR SCT010 BKN020 QNH3004INS
BECMG 1208/1209 27005KT 1600 BR FEW020 QNH3008INS
BECMG 1210/1211 28005KT 0800 FG FEW100 QNH3008INS
BECMG 1215/1216 30009KT 4800 BR FEW180 QNH3008INS
BECMG 1216/1217 32009KT 9999 NSW FEW180 QNH3008INS T17/1219Z T05/1211Z 
AMD 112023 LIMITED METWATCH 1201 TIL 1211=
The KDCA forecast issued just before my departure was calling for good visibility in light rain and light southerly winds under a 1500 foot overcast on arrival – no problem for the RNAV Rwy 6 approach into KVKX. Even if the conditions forecast to prevail after 00Z were to arrive early I'd be looking at two miles visibility under an 800 foot overcast – still acceptable. The weather wasn't forecast to get really bad until 06Z.

As a cross-check, I looked at the forecast prepared by the Air Force met watch for Andrews AFB. They were advertising the same light southerly winds, with a couple of miles visibility under a 1400 foot ceiling through 05Z with brief periods of 1/2 mile visibility and 900 foot ceiling. Also not too bad. One notable feature for the Andrews forecast was the "WS020/21042KT" group. That's a wind shear warning projecting wind at 2000 feet from 210 degrees at 42 knots. Not in itself a problem but worthy of note.

N631S and I were off the ground within minutes of 20Z and on our way. The clearance routed us from KBDR westward to Sparta VOR (SAX) then south to Solberg (SBJ), west again to East Texas (ETX) then south via Lancaster (LRP) and Baltimore (BAL) toward home. As expected, progress to the west was very slow with ground speeds between 85 and 95 knots (while true airspeed was about 140 knots). This implied a headwind component of about 45 to 50 knots.

About an hour into the flight I checked the weather at Washington National and didn't like what I saw:

SPECI KDCA 112116Z 22003KT 1 3/4SM -DZ BR OVC008 06/05 A3020 RMK AO2 P0000=

That 800 foot ceiling was three hours early and that suggested conditions in the DC area were deteriorating more quickly than forecast. This was not good. If the trend continued I might be unable to land at KVKX and have to divert to an alternate. My filed alternate was Manassas (KHEF), which had been legal when I filed. But Manassas was to the west, "up-weather", and if DCA was going down the tubes HEF would probably be at least as bad.

There was nothing for it but to press on and see what I'd have to deal with in the destination area. And as expected, N631S and I passed Baltimore and were heading south to the Nottingham VOR (OTT) at about 2140Z. That's about when the Potomac Approach controller asked, "Skylane 31 Sierra, what are your intentions?" At that point the weather looked grim:

SPECI KDCA 112142Z 20003KT 1SM R01/P6000FT -RA BR OVC006
07/05 A3018 RMK AO2 DZE39RAB39 P0000=

SPECI KADW 112151Z AUTO 00000KT 1SM R01L/P6000FT -DZ BR VV007
06/05 A3016 RMK AO2 DZB2145 SLP216

METAR KHEF 112155Z 17003KT 3/4SM BR OVC003 06/06 A3015=

The reports for DCA and ADW implied marginal conditions at best for VKX. The minima for the RNAV Rwy 6 approach at VKX are 680-1 (i.e., the approach requires 1 statute mile flight visibility and the Decision Height is 680 feet AGL). The METARs for DCA and ADW were not encouraging and my filed alternate (HEF) was looking none too good, even for an ILS approach.

I responded to the controller's query with: "I guess 31 Sierra's intentions are to try the RNAV 6 approach at VKX."

He replied, "A Pilatus just tried it and missed and he diverted to Easton. There's a Colombia 350 inbound for the approach. He'll get there before you; I'll keep you informed on how he makes out."

I thanked the controller and continued to motor on – slowly – toward OTT. Before too long, the controller was back. He told me, "31 Sierra, that Colombia missed at VKX and has diverted to Manassas. What do you want to do?"

I thought about it for a few seconds. First, two aircraft had missed at VKX, and the weather wasn't going to get better. I saw absolutely no point in trying to get in there. But where to go? I asked the controller, "Approach, 31 Sierra, can you say the weather at Manassas?"

He answered quickly, "300 and 3/4 in mist, wind 170 at 3."

That was doable but not great – especially if the trend was worsening. I asked, "Approach, 31 Sierra, could you say current conditions at Easton?"

The reply, after a few seconds, was, "Easton is reporting 7 miles, 1300 overcast, wind calm."

Sold! I said, "Approach, 31 Sierra would like to divert to Easton."

The immediate reply was, "November 631 Sierra is cleared to the Easton airport via radar vectors. Turn left to 050 and maintain 3,000 feet." A moment later, "31 Sierra, you can expect the ILS for Runway 4 at Easton."

I'd already descended to 3,000 feet on the way south from Baltimore, so I turned to the northeast and bid VKX farewell for the evening. As I rolled out on the 050 heading my groundspeed went from the low 90's to 173 knots. Remember that wind shear group in the Andrews TAF? A 40+ knot tailwind at 2,000 feet was going to make for a sporty ILS approach.

In what seemed like no time at all the controller said, "Skylane 31 Sierra, turn right to 080, descend and maintain 2,000 until intercepting the localizer. Cleared ILS 4 approach at Easton."

I acknowledged the approach clearance and got down to 2,000 feet as the localizer needle centered. I configured 631S for the ILS...manifold pressure 15", 10 flaps, indicated airspeed 90 or 100 knots, pitch for about 500 feet per minute descent...and watched as the glideslope indicator plunged toward the bottom of the instrument. With the tailwind, my ground speed was still 135 knots. I reduced the power further and pitched for 1,000 fpm descent and the glideslope began to creep back up.

I was still a couple dots high on the glide slope when we broke out at about 1,000 feet. There was that beautiful long runway at KESN, just where it belonged. I pitched up to slow to full flap extension speed and deployed all of the flaps and then did one of those "helicopter" descents that the 182 is so good at. We flared and touched down on the 1,000 foot touchdown zone markings. The tower asked where I was parking and I told them I needed an FBO and was unfamiliar. They advised me to turn left at the end of the runway onto Maryland Air's ramp.

I found the ramp, shut down, and walked over to the FBO – which proved to be locked up tight. So I returned to '31S and called the tower controller on the radio. Did he know of anyone that could help a poor wandering pilot on a dismal night? He said he'd call the Maryland Air after-hours number and see if they could help. Very soon he came back and told me they'd said to stand by, someone would be there soon.

In about 15 minutes, Bob from Maryland Air showed up to rescue me. He'd interrupted his Friday evening to open up the FBO and issue me a rental car for the hour-and-a-half drive home. And so I was on my way, soon to be done with a long and trying week.

My friend Sarah, who's a controller at Potomac TRACON, said in a comment to the last post that, "I was working approach that day and worked the first guy into (and right back out of) VKX. I almost got to say hi to you, but then watched you fly off my scope. Good call! That weather was no joke. Can't wait to hear how it all ended... :)"

Well, Sarah, there you have it.

7 comments:

Gary said...

Frank,

It was a brutal three days of fog in our area. Easton is/was a good choice, friendly folks at the FBO.

It's all about that plan B and keeping it updated which you have demobnstarted more than once in previous posts. Good stuff we all need to review, thanks for sharing the process.

Frank Van Haste said...

Gary, concur that the Maryland Air folks are friendly and helpful.

This one was sort of "Plan 'B' on the fly", as I really thought I had ample margin on the timing of the wx going down. Keys are situational awareness and flexibility. You can't stay married to a plan as it goes down the tubes.

Thanks for visiting and commenting,

Frank

Chris said...

Great post, Frank. As an instrument student, I appreciate these types of accounts that show real world IFR. Looks like it pays to stay flexible!

Frank Van Haste said...

Thanks, Chris -- glad you find it useful.

Y'know, the met people have gotten so good that we've come to expect forecasts to be close to correct. I don't even say "weatherguesser" anymore! But it's good to look at blown forecasts (like the ones in this post) and to realize that in dynamic weather systems any forecast can fall apart any time.

Best regards,

Frank

Comrade Misfit said...

Good head work.

Frank Van Haste said...

Dear Miss Fit:

You're too kind...thank you.

Frank

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