Wednesday, January 29, 2014

Collaborative Descision Making or Why Is My Flight Late

The FAA and the airlines (and some business aviation) have an agreement. If there is no space for the airplane, leave it on the ground. The FAA has a set of systems monitoring all flight plans, scheduled flights and the weather, mushes it all together to determine if there is room for the aircraft in the National Airspace System. If there is too much traffic at a certain point, then the FAA will issue a program, and tell the airlines to keep their aircraft on the ground.

If there is fog at an airport, and the rate the airport can take aircraft in is reduced to less than the volume of scheduled flights into the airport, then the FAA will issue a ground delay program (GDP). This ground delay will cause flights to be delayed at the departure airport. Typically the delay will  begin after the weather starts slowing things down, and will continue until the forecast shows things will get better.

Most passengers find this frustrating, but the reason is quite sound. The flight is going to be late to that airport anyway. Rather than risk stranding passengers at another destination, because the aircraft had to hold waiting for a slot at the destination, and the aircraft ran low on fuel, the passengers are left at the departure airport, and can choose a different itinerary, or just wait it out.

Other programs include an airspace flow program (AFP). An AFP is used when there is a line of weather across several states, causing many flights to be planned to go around that weather, all at a single choke point. The choke point is like an airport, where not all flights can get through, and may have to hold to allow proper spacing. Rather than getting too many aircraft through a small hole, it is better to leave the aircraft at the departure airport, with a delay, rather than possibly holding, and diverting.

Any of the delay programs are just a delay. The flight is delayed a known amount based on forecast weather. Sometimes, the delays can be adjusted based on current local forecasts. Sometimes the weather is better than forecast, other times not.

The last major program is a full Ground Stop (GS) program. This is where the conditions at the destination airport are not conducive to landing any more aircraft. One scenario for a ground stop would be malfunctioning equipment at a destination, and the time to repair is not determined.  The delayed aircraft may get an updated expected departure time, or they will get a next update time.

With the DOT 3hour rules and other reasons, some airlines may elect to cancel a flight or two due to one of these programs. Cancelling flights allow space to be made available. The FAA allows airlines to trade these spaces, or hold them for other flights. If airline A decides that it would be better to delay flight 123 that only is 60% full, they may decide to put most of those passengers on flight 456 that is 50% full, but leaving an hour later. That way the airline can make 48 people only a little late, and they will tell their friends how the airline "saved" them. The other 32 will just be frustrated, and may not complain too loudly.

The swaps and adjustments are part of the Collaborative Decision Making (CDM) program the FAA organizes. The CDM organization actually has several arms, and is chaired both by the airlines and the FAA. Some of the arms include groups working on weather, ground movement, and flight planning.

One of the programs the CDM group is working on, is collaborative flight planning. If the FAA and the airlines could make plans based on know congestion areas, then some of the programs might be eliminated. If the FAA gets a bunch of flight plans that all show the flights going around the south end of a storm, the FAA can suggest that going the north way might get the flight there sooner, even though the mileage is longer.

There is still a long way to go with all the information the airlines and the FAA  have to get passengers to their destination when they want to be there. Things are getting better all the time.

Wednesday, January 8, 2014

How Can Flight Planning be Accurate?

In pilot training, we all learned to use an E6-B or something similar, along with winds aloft forecast to do our flight planning. The values were pretty good, about as good as we could get considering it was all we knew. If the trip was short (about 500 miles or less) being careful, it can be nailed pretty well.

Now imagine flying a jet, over 2500 miles non stop, flying airways, in or near the jetstream, with an E6-B and the winds aloft forecast. It can be very accurate, but will be very time consuming to calculate. The interpolation alone will be a tremendous effort, and then calculating along the route, and keeping it all added correctly can be quite a challenge.

The computer has a small advantage in calculating the flight plan. Computers are great at keeping track of all the numbers, and interpolating. The National Weather Service (US NWS) and UK Meterological Office (UKMO) all model the weather in little rectangular 3D shapes, that the computer can look at and determine winds and temperature for the airspace.

There are multiple wind models used in various systems for flight planning. The Global Forecast System (GFS) model is pretty good, and available almost world wide. The GFS model is run 4 times a day, and forecasts can go as long as 16 days, with the first day having a specific forecast every hour, starting the second day every third hour up to 8 days, and every twelfth hour up to 16 days. The 3D rectangles are about 27km square and about 500 feet thick. The US also produces a finer grained model, called RAP or Rapid Refresh model which is updated more often has smaller 3D rectangles (13km squares, by about 600feet) and only covers the CONUS for 12 hours. (A high resolution rapid refresh model (HRRR) is being developed with 3km squares).

If a flight plan is created that will take an aircraft from Los Angeles to New York, flying at FL370 using the route:


The computer will look at all the 3D rectangles that the aircraft will pass through, and using the winds and temperature for that airspace, calculate the ground speed, distance and time for the aircraft in that area. The accumulation of all the times will be accumulated, and the end result will be the total flight time. That result is most of the time, then the book values for the aircraft can be used for climb to, and descend from altitude.

Normally the flight planning computer will expand out the OSHNN4 departure to all the waypoints, and calculate them individually to top of climb (TOC) then start calculating in the in the 3D rectangles at altitude. The flight planning computer will expand out the LENDY6 arrival and determine the top of descent (TOD) calculating everything up to that point using the flight level 3D rectangles, and the proper rectangles on the way down.

For airlines, a dispatcher will normally generate these flight plans. The dispatcher will look at the flights coming up for their area, and maybe run a preliminary plan (just an FYI, the Jeppesen Jetplan Flight Planning Engine takes about 6 seconds to run a plan similar to the Los Angeles to New York above). The dispatcher can look at the flight plan result, and plot it on a map to see where there may be weather or other congestion, and adjust it accordingly.

Once the dispatcher is happy with the plan, they will file it with the FAA ATC. The FAA ATC can look at that plan, and suggest changes or let the pilot fly it as it is. The FAA will keep the plan on file and use it in various calculations, including URET and other collaborative decision making (CDM) systems.

Overall, the computer makes flight planning much easier. There is much more to flight planning, this only covers winds and temperatures aloft, and how it applies to flight planning.

What should I cover next?

Saturday, January 4, 2014

trying to get ahead of the learning curve

Over the last couple months, I have been behind the learning curve in a big way. I started a new job in a new domain, and I decided to get my instructors rating. Since I haven't flown for a couple years, I decided to concentrate on my ground instructor rating, then I can go look at flight instructor another time. Two big domains of information cramming stuff into my little brain has been a challenge finding time to explain stuff. (nevermind the holidays and family issues, and all).

The FAA is changing the testing for everyone, and that could be a good thing, but it may not be. As part of the advanced ground instruction (AGI) rating I completed recently, there were two distinct parts. There was the flying instruction, and the fundamentals of instruction (FOI) part. The flying part was relatively easy, since I feel pretty confident in my understanding of the fundamentals of flight. The ground instruction test was pretty easy, and the questions and answers mostly matched the test prep I used.

The FOI was a real challenge. The FOI test is the one the FAA has changed significantly in the last couple of years. The main book for the test is the Aviation Instructors Handbook (FAA-H-8083-9A). It looks a little more colorful than most of the other FAA documents, and seems to have some really good information in it. Lots of learning theory, and psychology presented in a way to help the reader understand how people in general, and pilots in particular learn. Things that may offer help in overcoming difficulty when instructing different individuals.

The FOI test took a left turn from there. There are plenty of really informative good ideas in the book, but the test rather than focusing on those items, decided to test on nuances that may not be applicable. One example of the test, it asked the details of Bloom's Taxonomy of the Cognitive Domain, and not why they matter, or how to apply them. Like in a flight while teaching, I will consider Knowledge, Comprehension, Application, Analysis, Synthesis, and Evaluation, when  dealing with a student about to cross control an aircraft in a base to final turn. As we are spinning into the ground, I will think more about the application of control inputs, and how I should have emphasized them more, without considering the students comprehension.

Other places in the FOI test, they put in three perfectly good answers. I know at least twice in the test, I said to myself, "all of the above". Other places, there were three answers that contradicted the book. A question about the PTS asked what they are for. They are for testing, but the answer choices where all over the place, were they teaching aids (well the book says introduce them in the last three hours, sounds like a teaching aid to me).

I felt like I worked really hard preparing for this test. None of my practice tests since Christmas (when I re-read the book) did I get less than an 82. When I got done with the real test, I knew I didn't do that well and felt my score, if I passed, was just above 70. It was above 70, but not by much.

I guess end of the day, in 3 years when teaching a class no one will ask me if I got a 99 on the test or a 71, I passed, and I will continue to learn, and part of being a professional includes research (that was another question on the test). I shall be a professional.

What will I do with my new knowledge, and skill? I hope to introduce people to the concepts of flying. I want my classes to be broad enough that it will answer peoples questions about how aircraft work, with enough detail to allow the students to pass the private pilot ground school at the end, and give them the tools to do something with their knowledge. I am considering another blog around teaching people to fly.

What do you all want to know?