Gate to Gate

Over the last couple years, I have written about many bits of technology that aircraft use. I really haven't discussed too much what bits are used when, and for what. This post, I will try and tie all the items and their use into a comprehensive post. I'll use a commercial airliner (Part 121) for the discussion, both because they typically use more technology, and because that is what my background is. I will also base most of this on flights in the US, to keep it simpler.

We can start a few hours before the flight actually leaves. As the flight approaches it's scheduled time to leave, a group of folks have started planning for the flight. Sure, there is network planning, they set up the schedules and try to be sure the flight will make money, and provide continuity, and such, but that is usually done months in advance. There are also the simulators that the pilots use for proficiency checks, and training, but that is on going and not related to a particular flight, but important none the less.

Dispatchers and meteorologists are considering the situation between the origin and the destination of the flight. The meteorologists are generalists, looking at the weather over the country, where dispatchers are more concerned with the weather along the route between the cities. The dispatcher needs to consider the situation at the specific airports, for runway closures, and other challenges unrelated to weather. There is a tool called Collaborative Decision Making (CDM), where the dispatchers work with the other airlines so everyone can utilize the airports and airspace as optimally as possible.

The dispatchers can use CDM to look for areas to avoid when selecting a route between the two cities. If there is a bad thunderstorm along the optimum route and all the other airlines are avoiding it to the south, the dispatcher may pick a northern route to stay out of everyone elses way. Once the dispatcher selects a route, they need to build the rest of the flight plan. The dispatcher will build a flight plan using many tools. The dispatcher may allow the flight planning engine to select routes, or the amount of fuel. Depending on aircraft maintenance situation, and MEL deferrals and such the flight planning engine can accurately predict the fuel burn based on weather and route.

Once the dispatchers are happy with route and fuel selected, they will file a flight plan. The flight plan will be filed with the Air Navigation Service Provider (ANSP) for both the origin and the destination. For the US the ANSP is the FAA, in Canada is is NavCanada, and in the UK it is NATS. The ANSP handles all the RADAR and air traffic control (ATC) functions. The flight plan will give the ATC controllers a heads up on what the aircraft was planning on doing once in the air.

As the pilots get to the aircraft, one will typically do a walk around of the outside of the aircraft making sure the aircraft looks safe and no damage is visible. The other pilot will typically go to the cockpit and begin setting things up. There may be a the initialization of the FMS, maybe a RAIM check of the GPS, and entering the flight plan prepared by the dispatcher into the FMS. The dispatcher provided flight plan will usually include weather information for the route, and any other non weather realted information for the route (IE ATC changes, etc), The flight plan will also contain fuel and time information that the pilot can double check, insuring the dispatcher hasn't made any mistakes.

When the pilot know the fuel situation, they may confer with the fueler to adjust any fuel amounts to be put on board. The pilot will also need to know how many bags and passengers are on the flight, so they may make proper weight and balance calculations. Some airlines have a load planner who takes care of the weight and balance, others still let the pilot take care of this. Depending on the aircraft, it may be necessary to have a person dedicated to making the load calculations.

As all the passengers are seated, and the pilot is about to move the aircraft, they will ask for permission to move. There may be a ground controller dedicated to the gate area, and there will need to be taxi clearances and such needed from them. Other airports everything is controlled from the tower, and any movement must be cleared through the tower controllers. An ACARs message may be sent requesting the Pre Departure Clearance (PDC), that will be a version of the flight plan sent to the ATC with any ATCneeded changes to the plan. The PDC will also contain the code the pilot needs to enter into the transponder. The pilot must acknowledge receipt of the message.

After the aircraft is taxied to the runway, the pilot will ask the tower for the final airport clearance, by announcing "ready for takeoff". Once the ATC controller gives the pilot final instructions the pilot can access the runway and start the takeoff. The ATC instructions will be the route the pilot should take to get from the runway to the beginning of the flight plan route. Every bit of the instructions and plans for the takeoff are there in case there is a failure. If there is a radio failure either from ATC or the Aircraft, the instructions given are good enough for the pilot to take off, fly the planned route, and approach the destination. It is a safety situation, should the plan be the safest and most expeditious way to fly the route.

Once the aircraft is above about 300 ft, depending on the  airport, the aircraft will appear on RADAR. The first RADAR that will show the aircraft is the TRACON, who will control the aircraft after tower hands off the aircraft. The TRACON controller will control the aircraft until it is more than 30-50 miles from the airport. The TRACON will hand the aircraft off the enroute controllers who will control the flight until it is 30-60 miles from the destination airport. The RADAR data will be collected and sent to the FAA command center for others to view, and use the ADSI information. As we move into NextGen, there may be more ADS/B position reporting, instead of RADAR.

Once the aircraft is on the route, the pilots will typically engage the autopilot. The autopilot will help maintain the route of flight, altitude and throttle settings to insure the aircraft flies the route planned, and uses the fuel planned. The pilot must monitor the autopilot to be sure it is engaged, and doing the right thing the whole flight. Occasionally pilots will hand fly the aircraft, for practice. Once in a while the autopilot will fail, and the pilots must had fly the aircraft. The systems in the aircraft are designed for certain reliability levels.

During the enroute portion of the flight, there may be messages the pilots need to send to the company operations center. The pilots will usually send a text message over ACARS if they don't have a lot of urgency to the message. The pilots also have an option for voice communication using company assigned frequencies. If there were to be a medical emergency, the voice communications will be used, if a pilot is looking for a weather report for 400 miles ahead, they will use ACARS.

As the aircraft gets closer to the destination, ATC will typically begin having the aircraft start to descend. Newer approaches follow a continuous descent profile, where the pilots set the throttles to idle at altitude, and basically use the potential energy to glide the aircraft to the runway, reducing noise, fuel burn and pollution.

Current approaches typically are designed for the aircraft to provide it's own guidance. That is there are airs on the ground (or satellite) to provide the aircraft the information it needs to know where it is, and fly to the runway. Features like DME and ILS radions are on the ground, and GPS satellites are in the air.

The enroute controller will hand the flight off to the TRACON controller about 50 miles from the airport, where the aircraft will be below about 10,000ft. The TRACON controller will clear the flight for the approach that it will use to get to the airport. At about 5 miles out, the pilot will be told to contact the tower, and the tower and the pilot will make the final checks and be cleared for the runway to land on. Once on the ground, the pilot will talk to the ground controllers to get to the proper parking area, and maybe a gate controller for certain airports. Once the wheels are chocked, and the engines shutdown, the pilots are mostly done with the flight.

Yes, there is a bit of technology going on between each gate, and a little before. Ever think about that before.

The Connected Cockpit

The internet of things (IoT) is kind of the current discussion in many publications. The idea behind the internet of things is that everything will be connected to the internet, allowing monitoring and control of those things. As things are going, it is still too expensive to connect everything to the internet, and there many implications of connecting everything to the internet.

Many aircraft are getting WiFi in the cabin, people think the next step is putting an iPad in the cockpit, and connecting to the cabin WiFi and that should do it. Get all the flight plans, updates, weather and other data from headquarters we are all done. The trouble is, and was pointed out in the first post of this blog, there are security thoughts that need to be considered.

On transport aircraft, most of the cockpit is connected. Well connected, in that the FMS talks to the airopilot, and the EFIS may talk to the ACARS system, and the radios share a common bus. The trouble is, the cockpit is not talking IP, so it isn't easy to connect it to the WiFi, and it probably isn't a good idea.

In your GA business jet, it might be OK to connect the cabin to the cockpit. The people in the aircraft are usually well vetted, and may actually own it. They have a serious reason to be riding in the aircraft to the destination. Smaller aircraft may not have the means to get WiFi to the ground, but WiFi or other Ethernet connections could actually be done allowing the GPS to talk to the ADS-B transciever, and the MFD in the panel.

Allowing the cabin WiFi be connected to the cockpit of a part 121 transport aircraft is probably a bad idea. Probably the biggest problem would be if the aircraft were in a place with weak connection to the ground, and bandwidth was limited, who would get priority, the passenger watching Netflix or the cockpit needing a new route around some weather. The marketing department might argue the passengers, but flight operations department might argue the cockpit should have priority.

The other reason connecting the cockpit to the cabin using WiFi is a bad idea would be straight up security. There would be 100 people in the back bored wondering what is going on in the flight. It may be a curiosity for some, or a goal for others, they may just want to look at things, and manage to get access to say the current flight plan, in the FMS, and accidentally adjust it. Sure there could be firewalls and whitelists and other techniques to keep only the cockpit in the cockpit network, but there are ways for others to get in.

Having a separate cockpit connection to the ground is probably the right answer to the security question. having an isolated cockpit will make it harder to keep the cabin people out of the cockpit network.  It will be important to consider all the connections to the cockpit, and how secure they may be. If there is only an unsecured connection to the cockpit, then the cabin can probably still get to it through some ground station. Worse, if the cockpit doesn't have a secure connection to the ground, now there may be thousands of bored people trying to see what is going on in the aircraft.

Security has to be the first thought when building cockpit connected interfaces. Security through obscurity isn't real security, so proprietary standards won't be a long term solution. Bored people look at proprietary standards as a new challenge, and eventually they get figured out. Using industry best practices will be the only way to insure interoperability along with proper security.

It may be that the aircraft cockpits are only connected using one vendor (IE ARINC as things are today), where they provide an isolated network that only they can get to the aircraft. The messages will have to pass though a filter, and have proper originator white lists. All messages would be encrypted such that only known originators and destinations can see and use the messages. Certainly ARINC can't let Southwest Airlines read Delta Airlines messages, as well as some random person on the ground should not be able to sent messages to any aircraft.

It will take a bit of time for things to shake out, but eventually the cockpits will be connected.