CONTEXT DEPENDENT TOTAL ENERGY ALERT FOR THE DETECTION OF LOW ENERGY APPROACHES M A S T E R ’ S T H E S I S P R O P O S A L M I C H A E L P O R T M A N
INTRODUCTION • Commercial aviation operations have encountered a series of suboptimal approach profiles, collectively named “unstable approaches” • Consist of metrics including energy states • Alerts exist which warn pilots of each individually • However, no system exists which combines these metrics into a low total energy alert • Such an alert is proposed in this thesis • Integrates data already available onboard • Estimates current energy state and trend in total energy • Predicts whether the total energy will become too low, and alerts pilots with enough time for corrective action
CONTRIBUTIONS • Much research has taken place evaluating the use of energy metrics in aviation • No specific research on an alert for all modes of approaches • Will determine the ability of alert to guard against low energy unstable approaches better than current technology • Application of FOQA data allows for larger scale analysis of energy alerts than previous research • Real world application and validation
LITERATURE REVIEW Focus of literature review centers around five significant questions: 1. What is the function of an alert? 2. What is total energy? 3. What is context dependency? 4. Why would we need a total energy alert? 5. What are the attributes of a good total energy alert?
Q1. WHAT IS THE FUNCTION OF AN ALERT? Pritchett (2001): “An alerting system is an electro-mechanical system capable of monitoring for, detecting and announcing conditions anticipated (by the operator or the system designer) to impact the operator’s near-term activities.” • Properly detect certain conditions • Announce the presence of these conditions • Conditions are anticipated to impact the operator’s near-term activities Pritchett, 2001
Q2. WHAT IS TOTAL ENERGY? • Kinetic energy (airspeed) + gravitational potential energy (height above ground) • Energy naturally decays over the course of the approach (descent reduces potential energy) • Energy can be “transferred” between stores (by pitching) • Energy is added by increasing thrust • Low energy is when there is too little energy, system-wide, to respond by pitching • Adding energy/thrust is a required response
Q3. WHAT IS CONTEXT DEPENDENCY? • Allows alert to be tailored to each individual circumstance • Earlier alerting to allow more time to respond • Better prediction • Later desensitization/inactivation • Consists of knowledge of: • Phase of flight • Modeled ideal aircraft approach profile (speed, altitude) • Aircraft configuration • Local conditions (e.g. terrain, wind)
Q4. WHY WOULD WE NEED A TOTAL ENERGY ALERT? Asiana Flight 214 Unstabilized Approaches http://www.gatco.org/gatco-news/2016/10/17/new-guidance-material-on-unstable-approaches-published/ https://www.sfgate.com/bayarea/article/72-passengers-reach-settlement-over-Asiana-crash-6113481.php
ASIANA 214 OVERVIEW • Crashed on approach into SFO • Manual approach flown by pilots used to Autoland • Began with high approach • Pilots tried to lower approach, resulting in low energy unstable approach Boeing, 2014
ASIANA 214 INVESTIGATION • NTSB investigation cited lack of pilot awareness of autoflight functions and lack of situational awareness • Recommendation to FAA (A-14-43): Task a panel of human factors, aviation operations, and aircraft design specialists…to develop design requirements for context-dependent low energy alerting systems for airplanes engaged in commercial operations. NTSB, 2013
UNSTABILIZED APPROACHES AND STABILIZED APPROACH CRITERIA FSF ALAR Stabilized Approach Definitions: • Aircraft is on the correct flight path • Only small changes in heading/pitch required to maintain correct flight path • Aircraft speed is close to V ref (No more than V ref + 20 kts, no less than V ref ) • Aircraft is in the correct landing configuration • Sink rate <1000 feet per minute • Power setting appropriate for set configuration • Briefings and checklists conducted • Special circumstances accounted for and briefed FSF, 2000
Q5. WHAT ARE THE ATTRIBUTES OF A GOOD TOTAL ENERGY ALERT? • Alert: • Direct pilot’s attention to the predicted low total energy state of the aircraft’s approach • Total Energy: • Measure stability based on evaluation of both altitude and airspeed metrics together • Context Dependent: • Be aware of phase of flight, aircraft configuration, and local conditions to individualize alerting threshold • Good: • Better able to identify low total energy approaches than current onboard systems • Allows more time for pilot corrective action • Additional Considerations
REVIEW OF CURRENT TECHNOLOGY • Currently installed and operational • Autothrottle Wakeup • Autothrottle feature which advances throttles when airspeed is sensed to be too low • Inactivates in certain autopilot modes • EGPWS • Monitors aircraft location with respect to terrain, glide slope • Desensitized below 150ft radar altitude on approach • LAA • Alerts when 30% into amber band • Inactivated below 200ft radar altitude on approach Boeing, 2014
REVIEW OF CURRENT LITERATURE Several broad categories of research surrounding energy metrics: • General Aviation education applications (PEGASAS) • Commercial Aviation post-flight analysis • Energy based automatic flight control systems • Energy based alerting for autoflight approaches Puranik, et al., 2016; de Boer, et al., 2014; Lambregts, 1985; Shish, et al., 2015; Shish, et al., 2016; FAA, 2013; FAA, 2017
PROPOSED SYSTEM Design Overview: • Designed explicitly for use during approach and landing phases of flight • Monitors kinetic energy (airspeed) and above ground gravitational potential energy (radar altitude), as well as their decay over time • If decay is predicted to cause too little energy in the amount of time needed to safely abort the approach, an alert sounds
PROPOSED SYSTEM Mathematics: 1. 𝑈𝐹 = 𝑛𝑨↓𝑢𝑓𝑠 + 1 / 2 𝑛𝑊↑ 2 5. ∆ 𝑈𝐹 ≈ (𝑒𝑈𝐹/𝑒𝑢 ) ∗ 𝑢↓𝑡𝑏𝑔𝑓 1. 𝑈𝐹↓𝑔𝑗𝑜𝑏𝑚 = 𝑈𝐹 + ∆ 𝑈𝐹 2. 𝑒𝑈𝐹/𝑒𝑢 = 𝑛(𝑨 ↓𝑢𝑓𝑠 + 𝑊𝑏) or 𝑛𝑨 ↓𝑢𝑓𝑠 + 𝐺𝑊 6. If 𝑈𝐹↓𝑔𝑗𝑜𝑏𝑚 ≤ 𝑈𝐹↓𝑛𝑗𝑜 , the alarm sounds 1. F = T-D 3. 𝑢↓𝑡𝑏𝑔𝑓 = 𝑢↓𝑡𝑞𝑝𝑝𝑚 + 𝑢↓𝑠𝑓𝑏𝑑𝑢𝑗𝑝𝑜↑ ∗ 7. If T commanded is sufficiently high such that the system predicts the aircraft 1. 𝑢↓𝑡𝑞𝑝𝑝𝑚 = −4.55 ln � ( 1− (𝐸/𝜀𝑈 )) will recover, the alert will be silenced*. 4. 𝑈𝐹↓𝑛𝑗𝑜 = 𝑛𝑨↓𝑠𝑓𝑟↑ ∗ + 1 / 2 𝑛 𝑊↓𝑛𝑗𝑜↑ 2∗ 1. 𝑨↓𝑠𝑓𝑟↑ ∗ = 𝑒 ∗ 𝑢𝑏𝑜𝐻𝑇
PROPOSED BENEFITS • Functions for both manual and automated approaches • Context dependency allows for proper response (including thrust) from pilots • Alerts earlier than current onboard systems, giving more time to respond • Allows for later ability to alert than systems without dynamic thresholds (deactivates later)
ALERTING CONSIDERATIONS • Sensor metrics • Human factors Sensor lag Reaction time • • Frequency of data capture Dependent on many factors • • Primary reaction • Built-in uncertainty • Immediate go-around reaction • • Aircraft performance trainable, reducing needed time Engine spool time • Decision making allowance? • Time to arrest descent • Allows pilots to evaluate for themselves • the condition of the aircraft Necessitates earlier warning • Previous pilot knowledge of event • Potential for nuisance alarm • However, justifies go-around call •
PROPOSED WORK • Start with application of alerting criteria to Asiana 214 Preliminary application completed • Validate preliminary research • • Application to large set of FOQA data Data collected from major American carrier • Approaches into SFO and LAX • Similar approach profiles and aircraft to Asiana 214 • Determine which flights trigger alert, compare to: • Current FOQA unstable approach flagging • Current onboard alerting systems • Deeper analysis into flights which trigger alert •
PROPOSED WORK • Application/modification of real world influencing factors: • Human reaction time • Variation of total energy parameters • Minimum allowable airspeed/altitude • Thrust commanded vs. Thrust actual • Time permitting: • Evaluation of non-standard approaches • Phased alerting • More complex configuration effects in contextual awareness • Determination of optimal sensor suite characteristics for alert • Sensor limitations
WORK TO DATE • Application of alert to Asiana 214 • Graphical analysis shows alert would have sounded ~22-27 seconds before impact • 0.8-1nmi before runway • Approximately doubles advanced warning time Boeing, 2014
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