Monday, June 02, 2008

Wind and Time

Out of Lincoln I planned for a five and a half hour flight to Florida. The forecast showed that I should get pretty much a direct crosswind for the first part of the flight, and then a little bit of a push further on. I didn't count on the tailwind for the flight plan; I was just going to take it as a bonus if it happened.

Almost immediately after takeoff I suspected that that plan was not conservative enough. As soon as I turned en route my groundspeed dropped, and at level-off the ETA calculated by the GPS remained above six hours after the airplane had sped up to cruise. A weather system moves a little further east or west than forecast, doesn't have to be far, and the associated winds aren't going in the forecast direction at the point you are. Oh well. I originally planned this trip on a different route, one that would have given me howling tailwinds most of the way, but other operational concerns (i.e. my boss) dictated the route I took. So this is where I am. I'll keep a good eye on my watch and probably stop somewhere in Alabama. I've never been to Alabama.

Nebraska gives way to Kansas, and I get the song "Everything's Up To Date in Kansas City" stuck in my head. This is doubly irritating because Kansas City isn't even in Kansas. It's in Missouri. And when I say "song" I mean that one line, it's all I know of the song. I don't even know the tune. So I have the words "everything's up to date in Kansas City" running through my head for an entire state.

Eventually I'm distracted by the changing accents of the air traffic controllers. As soon as I crossed the 49th parallel the American accents became apparent. There's a change in the vowel length and something happens to medial Ts, but entering the southeast corner of the state there's another change from merely American to Dukes of Hazzard American. People from around here can probably identify the state someone is from, but I can't.

I'm approaching a giant river. It's so large that I don't need to look at the sectional chart to know that it is the Mississippi. I think this is my first time flying across it in daylight. Maybe I've flown across further north where it is less impressive. I have the autopilot on so I can get out the camera, but before I can take any pictures for you there is an air traffic controller yelling at me. Oh firetruck. The autopilot has silently disconnected and the airplane has descended 350 feet. I grovel an apology, regain the lost altitude, and suffer contritely the air traffic controller's diatribe against me. Now I lose any trust I had in that autopilot. I breathe on it and it disconnects. I think I exude a hormone or an electro-magnetic field that messes with autopilots. My aviation career is one long history of autopilots not doing what they were supposed to. They dive and climb and roll and fail to follow the bug.

The Mississippi was big and wide, curvy and muddy, snaking through flat green country as far as I can see in either direction. The cities here tend to be small and flat. I haven't seen any clusters of glass and steel towers, but I know there are some big cities around here.

The headwind has subsided and the ETE is hovering just below six hours. I'm carrying six and a half hours of fuel. A half hour is the minimum legal fuel I may plan to land with, but that only applies to day, and the day is getting on. Plus there could be thunderstorms at destination. I need forty-five minutes reserve fuel for night, and I'm still going both south and east, both bringing night closer, this time of year. The other issue is my duty day: if I can't reasonably expect to shut down at destination within 14 hours of the time I caught an airport cab this morning, then I can't take off. I do duty day math. I have enough time for a fuel stop if I need one.

I call flight services, looking for any CBs, forecast thunderstorms or new NOTAMs at my destination. It looks good. I ask for official night, something I should have found in my original flight planning, but I'm not sure where to find it on the US weather site. Neither is the briefer. He eventually comes back and tells me nightfall is at 20:45. I look at my watch, not the one on my wrist, which is still set to Mountain Time, but the Zulu watch on my clipboard. That was two hours ago. I ask him to confirm. "That doesn't sound right. It's already dark there?" The sun behind me is at about a 40 degree angle to the horizon. He double checks and realizes he has given me local time. He translates to Zulu. I'm golden. I'll be there an hour before dark. My groundspeed is still increasing. It looks like I'll land in daylight with 40 minutes of fuel remaining.

US briefers often do that: translate times to local, often without telling me. They are trying to be helpful, but it's dangerous and confusing. I think they have a tool that allows them to redisplay the weather products in local. I don't mind comments like "convective activity not really expected until mid afternoon" or "the rain will probably stop by midnight" but when you give the time in numbers, those numbers should be UTC.

I land at my destination airport in Florida, and, cleared to taxi, I take a few moments to orient myself. I've been here before. The best part is that the staff at the FBO remember me and welcome me back. I know recognizing customers and being nice to them is part of their job, but it's a really good feeling. I'm not sure which I like better in my job: going to new places and meeting new people, or going back to places I've been before and getting to see them again.

Oh and I'm going to start adding the tags "airplanes," "commercial aviation" and "flying" to all the posts they suit, even though those are the default topics for the blog, because I looked at my tag cloud and realized it made this look like a weather and avionics blog.

13 comments:

Lord Hutton said...

I camped by the mighty River Trent in England, Europe last weekend. 100 miles from the sea it is a stream but within those 100 miles it grows into a mighty estuary, spanned by what was briefly the longest bridge in Europe

dpierce said...

Following along on your journey is a blast. The autopilot doesn't give you an audible when it disconnects?

Paul Tomblin said...

Most GPSes have a page where they'll tell you sunrise and sunset times. Unfortunately I think they'll only tell you for where you are, not where you're going. If you have a Palm Pilot, the CoPilot flight planning software will tell you "Day Start" and "Day End" (in Zulu) for every waypoint, but I'm not sure if that's sunset, civil twilight, or what.

Mike said...

You have wind we have fog this morning:

TTF SPECI YMML 022130Z 27006KT 0200 FOG OVC002 07/07 Q1028
RMK RF00.0/000.2

We're not going anywhere anytime soon. RVR 250m. A/c is here but all movements are stopped.

Rather have the wind I think.

Have a great trip.

Mike

Luke said...

Nitpick alert...

There is, in fact, a Kansas City, Kansas. They adjoin each other along the state line; there are actually residential streets that transit from Missouri to Kansas with pretty much no interruption in the cityscape.

Anonymous said...

The cause of the crash

The autopilot had been switched from Command Mode, to CWS (Control Wheel Steering Mode). In the latter, any small inputs to the flight controls will instruct the autopilot how to alter the airplane's course.

------------
Undetected autopilot mode changes have been The Cause of serious crashes. Happily not in your case.

Anonymous said...

Is the requirement at night 45 minutes of fuel?

Aviatrix said...

Yes, Canadian and American VFR rules require 30 minutes reserve fuel by day and 45 minutes by night.

And no, sadly, this particular autopilot does not warble on disconnect. At least, not over Memphis.

MrV said...

Got hear via Phil The FA.... poked around and i liked wat I saw, so you have a new reader hear. Usally our paths cross only cross when something is broken. Your blog gives me a nice view into life outside the hanger....

bigpeteb said...

You've talked a lot about autopilots before, mostly when they're broken. :-) Maybe you could write a post on how they work, what they can do, and how to use them.

Aviatrix said...

Autopilots are as far from standardization as GPS units, so they all work differently, but I will make it a practice now to blog about them as I encounter them. Thanks for the suggestion.

majroj said...

"Iron Mike" was sloppy crossing the US from California to Maine. Our C-130 would repeatedly, in level flight, crab about five degrees to port then snap back. No, it wasn't the concerted snoring of we twenty brave sold in back blowing us sideweays. They fixed it overnight, and good thing; next leg was to Goose Bay, then to Britain.

Greybeard said...

To clarify, the fuel requirement is for flight planning only, so if adverse winds cause you to land with less fuel than you planned, you've broken no rules.
And... helicopter fuel requirements are different than airplane requirements...
Plan for twenty minutes fuel left, whether day or night.