Marqtholomew

Thunderstorm of the Apocalypse

August 23rd, 2007

I’m preparing for a flight to Friday Harbor tomorrow, and I’ve been following the weather forecast carefully over the past week. The forecast along my route of flight has been good, until I checked the national weather service’s graphical area forecast of the pacific northwest:

Thunderstorm of the Apocalypse!!

The NWS seems to be forecasting a super-thunderstorm of apocalyptic proportions which will cover the entire northwest around 5pm PDT tomorrow, accompanied by heavy rainfall. Apparently Utah will be spared from its wrath, as the superstorm will be precisely confined to the Idaho side of the border. Is it just a glitch in the NWS software, or cause to repent?

There’s a site called SkyVector.com that provides free access to scanned aeronautical sectional charts through a user interface similar to google maps. The maps also overlay routine weather observations (METAR) and provide detailed airport/runway information.

But here’s the cool part–they’ve recently added the ability to compute course headings and distances between points on the sectional chart and assemble a flight plan from the points. You just right-click anywhere on the sectional chart, select a waypoint, and repeat until you’ve created a list of waypoints defining your flight plan.

SkyVector Flight Planning Feature

*A disclaimer indicates that the feature is “not for navigation.” Nevertheless it is still a useful tool for rough high-level planning, as it is much more convenient than a plotter for getting an idea of how much distance the flight will cover. I’ll continue to use my flight planning software and the paper sectionals for my actual planning and navigation, but it does seem that SkyVector.com is moving their service in the direction of a software package fit for actual flight planning.

Marcware Weight and Balance Calculation Screen - Outside of Limits!
Marcware Weight and Balance Limit Entry Screen
Marcware Weight and Balance Fuel Calculator
Marcware Weight and Balance Station Entry Screen

I finally got around to packaging up my Weight and Balance program for the Pocket PC, and it is now available for download. The product page describes the program and has a few screen shots. I recently added a fuel calculator feature to the program which allows you to specify how many gallons of fuel you’ll have at takeoff, how many gallons will be consumed en route, and it will calculate the takeoff and landing fuel weights. I have been using it before all of my flights to compute the takeoff and landing weight and balance figures so it has undergone some real-world testing. Although it does have pretty decent unit test coverage I certainly make no claim that it is defect-free, so exercise caution and common sense when using this program for actual calculations. Let me know if you discover any problems, or have any requests for additional features.

Update: Marcware W&B has been reviewed on AviationReviews.com! See the review here.

This evening I added another command to the SMS Service for retriving winds aloft forecast data from the National Weather Service. The command is “FD”, which is the product code for the textual winds aloft forecast. You can query the service with the code for a major airport, and the service will reply with the wind direction, wind speed, and temperature for each altitude. The response for the command “FD PDX” might look like this:

[FD PDX] 3000:3422 6000:2720+04 9000:2533+02 12000:2539-03 18000:2454-17 24000:2363-28 30000:227143 34000:237750 39000:237053

So at 6000 feet, the wind is blowing from 270 at 20 knots, and the temperature is 4 degrees C. At 9000 feet the wind is coming from 250 at 33 knots, and the temperature has dropped to 2 degrees. They don’t give the temperature at 3000 feet.

See the SMS Services page for more information on this command.

I have a strange need to be constantly aware of the current weather conditions at the local airports, even if I have no intentions of flying any time soon. I found myself calling the Automated Surface Observation Station (ASOS) at Hillsboro Airport multiple times throughout the day and tying up the phone line, which led me to build a SMS service so I could get the same information through text messages. I started out with the METAR and TAF commands, allowing me to obtain routine weather observations and terminal aerodrome forecasts.

Last night I added a non-aviation related command for retrieving video game ratings from Gamespot. To try it out, just send this text message to sms(-at-)marqtholomew.com:

REVIEW ZELDA WINDWAKER

A minute or so later you will get this reply:

The Legend of Zelda: The Windwaker (GC): 9.3 The Wind Waker is a strong achievement in every way, from its stunning graphical presentation to its tight control

The “9.3” is the gamespot rating on a scale of 1-10, and is followed by their short synopsis. Very useful for those times when you’re in the video game aisle and desperately need to make an impulse purchase.

I also put together a page that describes the supported commands and gives examples on how to use them. The service is implemented as a python script scheduled to run every minute in a cron job. The script processes the messages and issues replies to the sender’s address.

I’ve been working on a program for the Pocket PC to perform aircraft weight and balance calculations, implemented in C# using version 1.1 of the Mobile .NET Framework. There are plenty of programs available that do this, but they all had little usability quirks and few had all of the features I was looking for: a graphical CG envelope, takeoff and landing fuel calculations, and multiple airplane profiles.

Marcware Weight and Balance Station Entry Screen Marcware Weight and Balance CG Calculation Screen

You start out by creating a new airplane profile, then configuring the center of gravity limits from the chart in the Pilot’s Operating Handbook. Then you enter the actual weight and arm values for each station (including Takeoff and Landing fuel weights), and hit the “Calc” button. A screen appears that shows the values for the Takeoff, Landing, and Zero-Fuel center of gravity at the top, and plots the values in the graphical envelope. If any of the center of gravity values are out of the limits, they will appear in  red .

At the moment there are still a few features I’d like to implement before I make it publicly available, such as the ability to specify moments instead of just arm values for each station. I’ll probably put together a product page in the next few weeks. In the interim it’s been a useful tool for speeding up the pre-flight calculations!

What I need now is a good name for the program. “Weight and Balance” is terribly unoriginal (but it is descriptive!).

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