FAA’s AC 120-123 places increased emphasis on flightpath management.
By Don Witt
ATP. Learjet series, Airbus A320, Boeing 737, Boeing 757/767
Early in the jet age, a new aircraft design feature – the T tail – was thought to be a good way to design jets for a number of aerodynamic advantages. Unfortunately, there was a yet unknown hazard in that configuration. It first reared its ugly head on an Oct 1963 BAC One-Eleven test flight over southern England as a so-called deep stall (unrecoverable stall). Eventually, various T-tailed aircraft experienced deep stalls that took many lives, both civil and military.
The worst of these tragedies was the deep stall and crash of a Hawker Siddeley Trident. This occurred 3 minutes into a Jun 1972 revenue flight (British European Airways Flight 548) out of LHR (Heathrow, London, England). The deep stall was due to premature retraction of leading-edge devices, and all 118 on board died in the now infamous Staines air disaster.
The cure for such tragedies was found to be a requirement for stick pushers in everything from Learjets to production BAC One-Elevens. Those devices mitigated the deep stall hazard. The Staines air disaster also kicked off development of crew resource management (CRM) training in the United Kingdom. In the US, CRM began later, in 1978, in response to a United Airlines DC-8 crash near PDX (Intl, Portland OR).
The cockpits of today’s jets display automation wizardry that is literally beautiful to behold. This is super helpful gadgetry for today’s pilots, and has many advantages for safety. However, like the deep stall that lurked unforeseen in T-tail designs, modern advanced automation also brought with it a hidden, very significant safety hazard.
This deadly hazard is surfacing in the form of a loss of basic pilot flight skills due to lack of practice. Many professional pilots are losing both skill and awareness because they hardly ever hand fly the aircraft other than during takeoff and landing.
Pilots have flown highly automated and perfectly functioning aircraft into terrain short of the landing runway (Asiana Flight 214 at SFO [Intl, San Francisco CA]) or into the sea (Armavia Flight 967 at AER [Sochi, Russia]), or crashed elsewhere because the pilots lost control of the flightpath. Other pilots have failed to manage the flightpath of their aircraft after “fail down” of automation (for example, Air France Flight 447).
Serious errors in flightpath management (FPM) can happen when automation is working correctly but pilots simply mismanage it. In the Asiana Flight 214 crash at SFO in 2013, for example, the pilot flying (PF) did not seem to understand autothrottle action with autopilot in FLCH and autothrottle in HOLD.
FPM can also go wrong when automation failures, instrument failures and mode reversions confuse both PF and pilot monitoring (PM). This scenario led to the Air France Flight 447 catastrophe in the North Atlantic in 2009.
Finally, FPM can go deadly wrong when a pilot attempting to fly manually simply loses control due to lack of proficiency, as happened in a go-around while Armavia Flight 967 was approaching AER in 2006.
AC 120-123, Flightpath Management, was published in Nov 2022. It addresses how proper training can assist crews to achieve effective guidance and control of aircraft trajectory and energy using skills in manual flight operations (MFOs), management of automation (autopilot, flight director, autothrottles, and FMS), and their own understanding of energy management.
It also stresses the training and proper duty of the PM, clearly stating that the PM bears exactly equal responsibility to that of the PF in ensuring safe FPM.
In the mid-1990s, 2 groups – the Performance-Based Operations Aviation Rulemaking Committee (PARC) and the Commercial Aviation Safety Team (CAST) – began working together on training issues.
In 2013, they issued a final report which included concerns about FPM. FAA then took that report as a basis to establish the Air Carrier Training Aviation Rulemaking Committee (ACT ARC), which eventually issued recommendations to FAA which are addressed now in AC 120-123.
The AC is divided into several chapters addressing, in turn, FPM, MFOs, managing automated systems, pilot monitoring responsibilities, and energy management. Clearly, a lot of thought and research went into the text of these chapters, and much teamwork was involved.
In the chapter “Flightpath Management – General,” it is stressed that both PF and PM are equally responsible for the flightpath of the aircraft, and both are responsible for being “fully capable of manually flying
the aircraft to achieve the desired flightpath.” Here, and again in the chapter that directly addresses PM, this point is hammered home. There are no excuses for copilots being trained to a lesser level of manual flying proficiency.
Furthermore, AC 120-123 recognizes that the PM is tasked with various additional duties aside from aircraft FPM, such as communications, navigation, and systems management, but it clarifies that this does not relieve the PM of his duty to monitor flightpath. Therefore, it does require a PM to develop skill in “attention management” – the often criticized but in this context required “multi-tasking” – while placing FPM always at the top of his priorities. In each of the accidents already mentioned above, it is clear that pilot monitoring failed.
The section on MFOs stresses the need for practice to retain proficiency. Specifying in SOP when the autopilot must be engaged (such as below certain ceiling and visibility minimums on an approach) is relatively easy. Unfortunately, specifying when and where hand flying may be required would be far too complex. This MFO section must then simply encourage pilots to hand fly as much as possible, and managers and trainers to stress this voluntary practice.
Practice, practice, practice
The better the automation, the more pilots rely on it. This is one reason Airbus pilots tend to hand fly less. FBW Airbus automation is highly capable, but if an Airbus pilot clicks off the autopilot, he/she is now flying an airplane that responds in a different way than any others he/she has ever flown.
Modern Airbus aircraft are essentially “flightpath stable,” not “speed stable.” From a level, stable flightpath, autopilot off, if the Airbus pilot pulls throttles to idle, the nose does not pitch down to maintain its trimmed airspeed (speed stability). Instead, it will eventually pitch up to maintain the angle (level flight) of its flight path. FAR 25 requires speed stability, but Airbus has a waiver based on the capability and excellence of its autothrottle.
Flightpath stability makes hand flying an ILS, for example, quite a different eye/hand task. Of course, you never really hand fly an Airbus aircraft unless you are in Direct Law due to failures. Still, this and other characteristics, like its excellent and nearly full-time autothrottle, make it even more important for a pilot to click off the autopilot and autothrottle and hand fly whenever practical to maintain proficiency.
AC 120-123 makes it clear that solutions are a team effort. Both PF and PM are tasked with maintaining a high level of hand flying proficiency, as well as skill with the automation. Operations managers are tasked with encouraging and ensuring these proficiencies in their crews (line checks). Training organizations are tasked with bringing hand flying skills back in focus during simulator training and checking. Coming years should see significant changes that mitigate the hidden hazard of loss of proficiency from over-reliance on automation.
Don Witt was a USAF F-4 pilot and holds a DFC. He is a retired United Boeing 767 and Airbus A320 captain and former safety manager for a large corporate flight department. He is presently a Learjet instructor and has been a long-time aerobatic instructor.