Why can't flight management systems receive instructions directly from the controller?

Question

If an aircraft's flight management system has auto pilot and auto thrust coupling, and it can make changes to the aircraft speed and direction along the entire route without pilot intervention, then why can't controllers just be allowed to make these changes directly without the need to ask the pilot to do it?

Pilots and controllers would still be monitoring the aircraft should things go wrong, but gone would be the days of endless voice instructions like "Flight xyz turn heading 123 climb and maintain...join the localizer for runway xx" "Contact xxxx on 123.xyz"

So many accidents happen due to misheard or unheard voice communication between pilot and controller, along with the pilot's misunderstanding of how flight director modes work.

The FAA should make this a goal, much like adoption of ADS-B.

Answer 1

Short answer: it's coming soon.

---

For why can't they, the answer is limited data transfers at the moment, which is being worked on.

• See: How can shifting to TCP/IP make current aviation systems more delay-tolerant?

Once implemented, it will be like the current CPDLC, where an instruction awaits the crew to press accept, reject, or cancel. A plane like the Boeing 787 already supports simple instructions to be loaded directly into the Mode Control Panel (MCP): the pilot's interface with the autopilot for the different lateral/vertical modes. The 787 is also ready to accept route changes from ATC via the FMS:

Boeing 787 CDU message for accepting a route uplink from ATC. The crew can then press LOAD FMC to view the changes before activating it.

• See MCP interface here: What are the differences between ACARS and CPDLC?

When to expect it?

In ICAO's Global Air Navigation Plan, it is expected to be in 'Block 1':

FANS3/C with CNS integration (via ATN B2) will be available providing communication and surveillance integration through a connection between the FANS and NAV (FMS) equipment. This avionics integration typically supports the automatic loading in the FMS of complex ATC clearances transmitted by data link.

(Emphasis mine.)

Block 1 is between 2018 and 2023. Of course it requires new equipment on airplanes alongside the new ground equipment.

You give an example of an instruction to intercept the ILS. With the avionics integration discussed above, the ATC will receive a downlink from the airplane for its FMS computed performance (e.g., descent performance based on weight and winds). And based on that the flight will receive an uplink with the assigned optimized arrival route to the runway based on 4D navigation (3D + time). The pilot then needs to arrive at each 'checkpoint' at the correct time for traffic separation. This is an example of a "complex ATC clearance".

Above example is still a decade or more in the future (Block 2). The implementation will be in steps. Of those steps is the extension of the arrival management to the en-route area, to be deployed in late 2023 in Europe.

Answer 2

Because the pilot in command of the flight is responsible for the safe outcome of the flight, not air traffic control. Pilots are responsible to evaluate a clearance and accept or decline it. Controllers have very limited information on a flight's situation and circumstances, information the pilot(s) must be aware of and must take into account in accepting a clearance. Such information could include aircraft system status, fuel state, weather conditions, and passenger needs.

Pilots make mistakes, and so do controllers. A single controller handling multiple aircraft in his or her sector is not expected to have a full awareness of each aspect of each aircraft's situation. That is the job of the pilots. The pilots and controllers work as a team, but the ultimate responsibility rests with the pilot in command.