Short-haul Flights Research Articles

Parameterization of a Conventional and Regenerated UHB Turbofan

AbstractThe attempt to improve aircraft engines efficiency resulted in the evolution from turbojets to the first generation low bypass ratio turbofans. Today, high bypass ratio turbofans are the most traditional type of engine in commercial aviation. Following many years of technological developments and improvements, this type of engine has proved to be the most reliable facing the commercial aviation requirements. In search of more efficiency, the engine manufacturers tend to increase the bypass ratio leading to ultra-high bypass ratio (UHB) engines. Increased bypass ratio has clear benefits in terms of propulsion system like reducing the specific fuel consumption. This study is aimed at a parametric analysis of a UHB turbofan engine focused on short haul flights. Two cycle configurations (conventional and regenerated) were studied, and estimated values of their specific fuel consumption (TSFC) and specific thrust (Fs) were determined. Results demonstrate that the regenerated cycle may contribute towards a more economic and friendly aero engines in a higher range of bypass ratio.

First Masquerading as Gallstones, Pulmonary Hypertension Mimics PE

Patients presenting to emergency and urgent care centers with calf pain after long and short-haul flights are a common presentation throughout Europe. Patients fitting an epidemiological risk profile for cholelithiasis and presenting with right upper quadrant abdominal pain can also be a common presentation fitting of a specific patient profile. However, pulmonary hypertension can present in a nuanced and possible missed chronic and acute presentation. The patient case we present profiles a mildly obese 54-year-old Caucasian woman and recent holiday maker with unilateral calf pain and shortness of breath after traveling on a long-haul flight with tertiary symptoms of indigestion and epigastric discomfort indicative of gastroenteritis. This case highlights the required diligence for emergency physicians to maintain a high index of suspicion and broad differential diagnosis in the undifferentiated patient with seemingly common or classic presentations. We find that a serendipitous definitive diagnosis is made by following a systematic and organized approach.

Fatigue Detection in Commercial Flight Operations: Results Using Physiological Measures

In an effort to better understand the impact of fatigue on commercial flight operations, we collected physiological and performance data from commercial flight crews performing simulated operations under both rested and fatigued conditions. The purpose of this research was 1) to evaluate the effects of varying levels of fatigue and workload on pilot performance and physiological responses, and 2) to determine whether any technology exists to detect symptoms of fatigue in real time. Thirty-two airline pilots were fitted with a variety of physiological measurement devices to measure characteristics that are affected by fatigue. Each crew of two pilots flew a “rested” and a “fatigued” session in a high-fidelity B-777 simulator. Crews were assigned to one of two flight scenarios: either one 6.5 hour “long-haul” flight or four consecutive 0.5 to 1.5 hour “short haul” flights. Subjective fatigue ratings accurately reflected the rested and fatigued conditions; however, performance on a psychomotor vigilance task did not vary significantly between rested and fatigued conditions or between short and long haul flights. Further, although physiological data allowed a general distinction between larger and smaller fatigue effects for most individuals, no single measurement device was found to reliably indicate fatigue levels with enough granularity to allow for useful fatigue detection. However, a statistical/machine learning model was constructed that was able to accurately categorize fatigued data for each individual pilots using that pilot's combined sensor data with a success rate greater than 95%. It is probable that by optimizing the parameters of the model and improving the quality of sensor data, an algorithm-based solution to real-time fatigue detection can be developed. The applicability of this type of approach extends beyond the commercial flight deck to any work environment that requires multi-shift or other non-traditional scheduling.

Slot premium: London Heathrow versus London Gatwick

This paper provides a historical review of slot trades and transactions at London Heathrow Airport, and conduct an empirical analysis of revenue premium of flights out of Heathrow over Gatwick to see whether the sale prices of British West Indian Airways (BWIA) and Air Jamaica's Heathrow slots reflect the revenue premiums. Our results show that the average yield for short haul flights out of Heathrow more than doubles that for flights out of Gatwick, whereas the average yield for long haul flights out of Heathrow is about 11% higher than that out of Gatwick. Overall, the average yield for flights to/from Heathrow is about 45% higher than that for flights to/from Gatwick. The present values of the revenue premium of BWIA and Air Jamaica's Heathrow slots are estimated at £78 million and £83 million at 8% discount rate, respectively. Therefore, the sale prices of £5 million and £5.1 million for these slots in 2006 and 2007 appear to be undervalued.

A correlation linking the predicted mean vote and the mean thermal vote based on an investigation on the human thermal comfort in short-haul domestic flights

The results of an experimental investigation on the human thermal comfort inside the cabin of some Airbus A319 aircrafts during 14 short-haul domestic flights, linking various Italian cities, are presented and used to define a correlation among the predicted mean vote (PMV), a procedure which is commonly used to assess the thermal comfort in inhabited environments, and the equivalent temperature and mean thermal vote (MTV), which are the parameters suggested by the European Standard EN ISO 14505-2 for the evaluation of the thermal environment in vehicles.The measurements of the radiant temperature, air temperature and relative humidity during flights were performed. The air temperature varied between 22.2 °C and 26.0 °C; the relative humidity ranged from 8.7% to 59.2%. The calculated values of the PMV varied from −0.16 to 0.90 and were confirmed by the answers of the passengers. The equivalent temperature was evaluated using the equations of Fanger or on the basis of the values of the skin temperature measured on some volunteers.The correlation linking the thermal sensation scales and zones used by the PMV and the MTV resulted quite accurate because the minimum value of the absolute difference between such environmental indexes equalled 0.0073 and the maximum difference did not exceed the value of 0.0589. Even though the equivalent temperature and the MTV were specifically proposed to evaluate the thermal sensation in vehicles, their use may be effectively extended to the assessment of the thermal comfort in airplanes or other occupied places.

Leisure Travel: Implications for Airline Alliances

The rationale behind the formation of airline alliances includes the reaping of scale and scope economies and the acquisition of marketing and branding advantages. To really add value to the airline customer, however, alliances should consider the purpose of travel, i.e. they should appreciate and understand the derived nature of the airline product. The relevant literature seems to understate this issue or at best focus on business passengers. Given the rising importance of leisure travel and tourism in the world economy, its implications should be explicitly assessed. The emergence of low cost carriers and the subsequent simplifications in the holiday packages offered by charter airlines have played a major role in boosting leisure travel in Europe at least. Still, the intelligent management of frequent flyer programmes and the creation of a seamless network in long haul (or even intercontinental) air travel may induce leisure passengers to opt for an allied airline instead. This paper addresses the topic by undertaking primary research in the form of semi-structured interviews with airline executives and structured questionnaires addressed to passengers. The interviewees are supportive of the view that alliances of network carriers may offer benefits to leisure passengers although they do recognise the competitive threat posed by low cost carriers. Similarly, the statistical analysis of the questionnaire results reveals that frequent flyers and more affluent respondents are more knowledgeable about strategic alliances and have a tendency to prefer allied carriers for long-haul but not for short-haul flights. This outcome may add to the understanding of airline alliances and consumer behaviour and have important implications for airline strategy at a global level.

Significance of time awake for predicting pilots' fatigue on short-haul flights: implications for flight duty time regulations.

European regulations restrict the duration of the maximum daily flight duty period for pilots as a function of the duty start time and the number of scheduled flights. However, late duty end times that may include long times awake are not specifically regulated. In this study, fatigue levels in pilots finishing their duty late at night (00:00-01:59 hour) were analysed and compared with pilots starting their duty early (05:00-06:59 hour). Fatigue levels of 40 commercial short-haul pilots were studied during a total of 188 flight duty periods, of which 87 started early and 22 finished late. Pilots used a small handheld computer to maintain a duty and sleep log, and to indicate fatigue levels immediately after each flight. Sleep logs were checked with actigraphy. Pilots on late-finishing flight duty periods were more fatigued at the end of their duty than pilots on early-starting flight duty periods, despite the fact that preceding sleep duration was longer by 1.1 h. Linear mixed-model regression identified time awake as a preeminent factor predicting fatigue. Workload had a minor effect. Pilots on late-finishing flight duty periods were awake longer by an average of 5.5 h (6.6 versus 1.1 h) before commencing their duty than pilots who started early in the morning. Late-finishing flights were associated with long times awake at a time when the circadian system stops promoting alertness, and an increased, previously underestimated fatigue risk. Based on these findings, flight duty limitations should consider not only duty start time, but also the time of the final landing.

The Costs of Airline Service - The Short-Haul Problem

<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-fareast-font-family: 'MS Mincho'; mso-ansi-language: EN-GB; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-GB">Cost of airline service consist of many parameters, including load factor, which is important for airline decision making. Short-haul flights compete with many other ways of transportation on short distances which makes demand very sensitive. This brings up the question how to set optimal costs for short haul flights.</span>

Thermal comfort assessment in civil aircraft cabins

Aircraft passengers are more and demanding in terms of thermal comfort. But it is not yet easy for aircraft crew to control the environment control system (ECS) that satisfies the thermal comfort for most passengers due to a number of causes. This paper adopts a corrected predicted mean vote (PMV) model and an adaptive model to assess the thermal comfort conditions for 31 investigated flights and draws the conclusion that there does exist an uncomfortable thermal phenomenon in civil aircraft cabins, especially in some short-haul continental flights. It is necessary to develop an easy way to predict the thermal sensation of passengers and to direct the crew to control ECS. Due to the assessment consistency of the corrected PMV model and the adaptive model, the adaptive model of thermal neutrality temperature can be used as a method to predict the cabin optimal operative temperature. Because only the mean outdoor effective temperature ET∗ of a departure city is an input variable for the adaptive model, this method can be easily understood and implemented by the crew and can satisfy 80–90% of the thermal acceptability levels of passengers.

Source apportionment of airborne particles in commercial aircraft cabin environment: Contributions from outside and inside of cabin

Airborne particles are an important type of air pollutants in aircraft cabin. Finding sources of particles is conducive to taking appropriate measures to remove them. In this study, measurements of concentration and size distribution of particles larger than 0.3 μm (PM>0.3) were made on nine short haul flights from September 2012 to March 2013. Particle counts in supply air and breathing zone air were both obtained. Results indicate that the number concentrations of particles ranged from 3.6 × 102 counts L−1 to 1.2 × 105 counts L−1 in supply air and breathing zone air, and they first decreased and then increased in general during the flight duration. Peaks of particle concentration were found at climbing, descending, and cruising phases in several flights. Percentages of particle concentration in breathing zone contributed by the bleed air (originated from outside) and cabin interior sources were calculated. The bleed air ratios, outside airflow rates and total airflow rates were calculated by using carbon dioxide as a ventilation tracer in five of the nine flights. The calculated results indicate that PM>0.3 in breathing zone mainly came from unfiltered bleed air, especially for particle sizes from 0.3 to 2.0 μm. And for particles larger than 2.0 μm, contributions from the bleed air and cabin interior were both important. The results would be useful for developing better cabin air quality control strategies.

Flight Schedules and Occupational Accidents Among Cabin Crew: a Longitudinal Study

Flight schedules of cabin crew involve early starts, long working hours, night flights, and the crossing of time zones, all of which might contribute to the risk of onboard occupational accidents. Because it is unclear if cumulative flight schedule exposure affects the incidence of occupational accidents, the objective of this study is to examine this association among cabin crewmembers. Data from the 5-yr historic MORE cohort was used. The study population consisted of 6311 cabin crewmembers. For each employee, all flight schedules from 2005 to 2008 and registered occupational accidents in 2009 were collected. The association between the cumulative exposure to different types of flights and the occurrence of occupational accidents was determined using logistic regression analyses. In 2009, 289 cabin crewmembers reported at least 1 occupational accident. The adjusted logistic regression models showed that the number of short-haul flights during the period 2005-2008 was positively associated with the occurrence of occupational accidents in 2009. Less exposure to long-haul flights was also associated with reporting an occupational accident. The results of this study suggest that cumulative exposure to short-haul flights is associated with an increased risk for occupational accidents among cabin crewmembers. This increased risk may be caused by the specific characteristics of short-haul flights. Future research should focus on possible underlying mechanisms, such as fatigue accumulation, and on the influence of adjustments to short-haul schedules. Airline companies can increase their focus on the short-haul operation in order to reduce onboard accidents.

Specification issues in a generalised random parameters attribute nonattendance model

An extensive literature has recognised that when travel choices are made, only a subset of the attributes of the choice alternatives may be considered or attended to by each decision maker. Numerous econometric approaches have been employed to identify attribute nonattendance (ANA), with the most prevalent in the literature being an adaptation of the latent class model. However, the two latent class structures so far employed either incur a potentially very high parametric cost, or rely on an assumption that nonattendance is independent across all attributes. We present a generalised model that allows for an arbitrary degree of correlation of nonattendance across attributes. In the presented stated choice study investigating short haul flights, this generalised model outperforms the existing approaches. Like two recent papers, the model handles both ANA and preference heterogeneity by combining continuously distributed random parameters with latent classes. However, we present recommendations regarding a number of identification issues stemming from the combination of these two forms of random parameters not covered in those papers. Further, covariates can be introduced into our generalised model to allow insights to be gained into ANA behaviour. We investigate stated ANA as a covariate, and find inferred ANA rates to be more aligned with stated ANA responses than alternative methods.

404 Longitudinal associations between flight schedules and occupational accidents among cabin crew

ObjectivesWork schedules of cabin crew involve early starts, long working hours, night flights and the crossing of time zones. This can impose disturbed sleep, fatigue, lack of alertness, and possibly...

Method to predicting optimal cabin operative temperature for civil aircraft

Aircraft passengers are becoming more demanding in terms of thermal comfort, and many researches were conducted on this issue. But it is not yet easy for aircraft crew to control the Environment Control System (ECS) to satisfy the thermal comfort for passengers. By surveying 31 investigated flights, we draw the conclusion that there were uncomfortable levels of thermal phenomena in some civil aircraft flights, especially in some short-haul continental flights. It is then necessary to develop an easy way to predict and control the optimal operative temperature for a civil aircraft cabin so that the thermal comfort requirements can be satisfied for most of the passengers. In this paper, we use a Corrected Predicted Mean Vote (CPMV) model to obtain the thermal neutrality temperatures (Tn,CPMV) for the investigated flights. We constructed a linear regressive relationship between Tn,CPMV and the mean outdoor new effective temperature (ET*). The statistical significance of regression probably reflects the dependence of Tn,CPMV on the outdoor climate of the departure city. By using this relationship, an optimal cabin operative temperature can be predicted easily. Hence the method presented in this paper can help the crew to control cabin temperature easily and directly according to the ET* of the departure city.

Circadian adaptation of airline pilots during extended duration operations between the USA and Asia

This study tracked circadian adaptation among airline pilots before, during, and after trips where they flew from Seattle (SEA) or Los Angeles (LAX) to Asia (7--9 time zones westward), spent 7--12 d in Asia, and then flew back to the USA. In Asia, pilots' exposures to local time cues and sleep opportunities were constrained by duty (short-haul flights crossing ≤1 time zone/24 h). Fourteen captains and 16 first officers participated (median age = 56 versus 48 yrs, p.U) < 0.001). Their sleep was monitored (actigraphy, duty/sleep diaries) from 3 d pre-trip to 5 d post-trip. For every flight, Karolinska Sleepiness and Samn-Perelli Fatigue scales and 5-min psychomotor vigilance task (PVT) tests were completed pre-flight and at top of descent (TOD). Participants had ≥3 d free of duty prior to outbound flight(s). From 72--24 h prior to departure (baseline sleep), mean total sleep/24 h (TST) = 7.00 h (SD = 1.18 h) and mean sleep efficiency = 87% (SD = 4.9%). Most pilots (23/30) flew direct to and from Asia, but 7 LAX-based pilots flew via a 1-d layover in Honolulu (HNL). On flights with ≥2 pilots, mean total in-flight sleep varied from 0.40 to 2.09 h outbound and from 0.74 to 1.88 h inbound. Duty patterns in Asia were variable, with ≤2 flights/d (mean flight duration = 3.53 h, SD = 0.53 h). TST on days 17 in Asia did not differ from baseline (p.F) = 0.2031). However, mean sleep efficiency was significantly lower than baseline on days 5--7 (p.F) = 0.0041). More pilots were on duty between 20:00 and 24:00 h on days 57 (mean = 21%) than on days 24 (mean = 14%). Sleep propensity distribution phase markers and chi-square periodogram analyses suggest that adaptation to local time was complete by day 4 in Asia. On pre-flight PVT tests in Asia, the slowest 10% of responses improved for flights departing 14:00--19:59 h (p.F) = 0.0484). At TOD, the slowest 10% of responses improved across days for flights arriving 14:00--19:59 h (p.F) = 0.0349) and 20:00--01:59 h (p.F) = 0.0379). Sleepiness and fatigue ratings pre-flight and at TOD did not change across days in Asia. TST on post-trip day 1 was longer than baseline (estimated mean extension = 1.68 h; adjusted p(t) < 0.0001). On all post-trip days, sleep efficiency was comparable to baseline. Sleep propensity distribution phase markers and chi-square periodogram analyses suggest complete readaptation in 12 d. Two opposing influences appeared to affect sleep and PVT performance across days in Asia: progressive circadian adaptation to local time and increasing duty during local night, which displaced sleep from the optimal physiological time. Cumulative sleep restriction across the return flight may explain the large rebound in TST on day 1 post-trip. Thereafter TST, sleep efficiency, and sleep timing suggest that readaptation was complete. Rapid post-trip readaptation may be facilitated by pilots having unconstrained nocturnal sleep opportunities, coupled with stronger patterns of family and social cues than in Asia.

Air quality and relative humidity in commercial aircrafts: An experimental investigation on short-haul domestic flights

Nowadays the achievement of a comfortable environment in aircraft cabins is a factor of paramount importance in air travel business competition; on the other hand, the need of reducing the propulsion fuel cost has driven the airline companies to adopt air handling systems that may reduce the levels of thermal comfort and air quality inside the cabins of commercial airliners. With the aim of contributing to a better knowledge of this matter, this paper reports the results of an experimental study upon the indoor air quality aboard commercial aircrafts for 14 domestic flights less than 1 h and half long. The parameters monitored were temperature, relative humidity and carbon dioxide concentration; the measurements were performed during the whole flight from the take-off to the landing.The relative humidity inside the cabin was also calculated using the rates of outside air and the carbon dioxide as a ventilation tracer; the theoretical results were compared with the measured data. The relationship between relative humidity and carbon dioxide concentration during fights was highlighted in order to define the environmental conditions that may provide acceptable levels of both the air quality and hygrometric comfort to the crew and passengers. The results of calculations confirmed the possibility of improving the hygrometric conditions in aircraft cabins without the need of using humidification systems.

Schedule Preference and Pricing Decision for Short-haul Flights in Airlines

Schedule Preference and Pricing Decision for Short-haul Flights in Airlines

Broadband Noise Predictions from Uninstalled Contra-Rotating Open Rotors

This paper presents broadband noise predictions from uninstalled contra-rotating open rotors (CRORs). CRORs are being increasingly investigated as an alternative to single propellers and turbofan engines for power plants on aircraft, since they yield a significant reduction in fuel burn for short-haul flights. However, there is the need to develop schemes by which CROR noise can be predicted and reduced. Using semi-analytical prediction schemes, the principal broadband noise source mechanisms (rotor trailing edge noise and rotor-rotor interaction noise) are investigated, leading to strategies for their mitigation. For the configuration considered, trailing-edge broadband noise is predicted to be dominant at low rotor loading conditions (typical of cruise and approach) whereas rotor-rotor interaction broadband noise is predicted to be dominant at high rotor loading conditions (typical of take-off). A systematic parameter study is also presented in which the dependence of CROR broadband noise on the rotor-rotor gap, rotor speeds and blade numbers are investigated at constant engine power, torque split and solidity.

Airline Pricing Behaviour Under Limited Intermodal Competition

This paper empirically analyses airline pricing for short-haul flights in contexts with no credible threat of inter-modal competition. To this end, we explore the southern Italian market since it is less accessible by other transport modes and thus fares are the direct outcome of air-related competition. We show, in fact, that market power matters, depending on the level of intra-modal competition, and that airlines apply differentiated mark-ups. Besides, consistent with the implementation of inter-temporal price discrimination (IPD), we find a non-monotonic inter-temporal profile of fares with a turning point included in the interval of the 43th to 45th days before departure. Finally, we provide evidence that in more competitive markets, airlines are more likely to engage in IPD.

Internal sensations as a source of fear: exploring a link between hypoxia and flight phobia

Although flight phobia is very common in the general population, knowledge of the underlying mechanisms is limited. The aim of the current study is to determine whether hypoxia is selectively associated with flight anxiety. We wanted to explore levels of oxygen saturation (SpO2) and the associated subjective somatic sensations in flight phobics and controls. The data collected in this study were obtained from 103 participants: 54 had flight phobia, 49 were controls. SpO2 as well as a subjective report of somatic sensations and anxiety were measured during short haul flights, both at ground level and at cruising altitude. Results indicated that both flight phobics and controls showed a comparable clinical significant decrease in SpO2 from sea level to cruising altitude. Next, at ground level the flight phobic group reported more somatic sensations, most likely due to the elevated levels of anxiety at that point. However, at cruising altitude the flight phobic group still reported more somatic sensations while the level of anxiety was no longer significantly different from controls. This finding points to altered symptom perception in flight phobia and stresses the importance of somatic sensations in this particular phobia.