Weather and Climate (1997) 17 (2): 11-22 1 1 METEOROLOGCAL LMTS ON THE USE OF NEW ZEALAND ARPORTS FOR FLGHT TRANNG T Steiner School of Aviation, Massey University, Palmerston North ABSTRACT An analysis is made of the suitability of New Zealand airports for flight training. Examination of published data on sunshine, and frequency of days with strong wind gusts and with fog identified airports worthy of further study. For a selection of such airports, the airport climatology publications produced in the 198s were examined Data extracted from the publications indicates that Nelson, Woodbourne (Blenheim) and certain airports in the centre and northeast of the North sland are the most favourable. However the publications do not consider cloud and visibility thresholds as stringent as those for flight training. t was therefore necessary to access the archive of airport meteorological data. Synoptic (three hourly) weather reports were examined for a selection of eight airports, which the earlier parts of the study suggested might be favourable. Nelson, Woodbourne and Gisborne are found to be the most suitable for ab initio training and Woodbourne is the most favourable for more advanced students. The results need to be treated with caution. Other meteorological parameters such as turbulence and the extent of the favourable weather beyond the airport are not assessed and nor are non-meteorological logistic issues. Some further applications of the analysed series are suggested. NTRODUCTON Aviation is an expanding industry, particularly in the Asia-Pacific sector. There is accordingly a demand to train many new pilots. n someasia-pacific countries there are limited opportunities for training because there are only a small number of airports and these are heavily used by airlines. There is thus scope for countries such as New Zealand, with airports that are not heavily utilised for air operations, to undertake flight training, not only of nationals but also of foreign students. The School of Aviation at Massey University participates in this training with its aircraft based at Palmerston North Airport. Since the School began flight training in 1987, it has become apparent that unsuitable meteorological conditions are a major impediment to flight training. Weather limitations on student pilots, particularly those commencing their training, are more restrictive than the minima for Visual Flight set by the Civil Aviation Authority and are far less than the weather limitations on aircraft operating under nstrument Flight Rules. The limitations are those of wind speed, cross-wind component on the airport runway, visibility and height of significant amounts of cloud. A survey of the views of Massey University School of Aviation flight instructors on the meteorological limits for trainee pilots was undertaken (G. Miller, pers. comm) The limits established are shown in Table 1. Because weather related disruptions cause significant delays to the flight training programme, there is a need to consider whether there are airports in New Zealand that would be more suitable than Palmerston North for flight training. Suitability is determined not only by weather but also by non-meteorological factors. The latter include the presence of adequate runways, availability of air traffic services and logistical issues such as the availability of hangars, fuel and accommodation. Only meteorological factors
12 The use of New Zealand Airports for Flight Training Parameter Ab initio training (Al) More advanced training (MA) Wind speed 2 knots or less 25 knots or less Cross wind component 5 knots or less 17 knots or less Visibility at least 3 km at least 2 km Lowest Cloud (4 oktas or more) at least 25 feet Table 1. Limits on flying conditions for ab initio and more advanced trainee pilots. at least 2 feet are considered in this study. Although it was initiated to contribute to resolving a particular problem for the University, it is of general relevance for planning any flight training in New Zealand. There are several ways of estimating the meteorological suitability of New Zealand airports for flight training. A simple approach makes use of a general knowledge of the climate of the country. t suggests that the most suitable locations are in the lee of the mountains much of the time and in areas that are not very windy, but also not subject to persistent low cloud or fog and with an appropriate direction of a runway, preferably sealed and therefore useable even following heavy rain. This method does not yield quantitative results but it is the only method available for considering the suitability of the airports for which there is little data available. t suggests that places in the north and east of both islands are likely to be among the most suitable. Another simple approach, adopted in the first part of the present study, uses published statistics (New Zealand Meteorological Service, 1983 and 1985) to determine the frequency of measured parameters that are related to suitability for flight training. Twenty-eight airports were considered and the most favourable were identified. During the 198s a series of New Zealand airport climatologies were published, e.g. "The Climatology of Auckland nternational Airport" (New Zealand Meteorological Service, 1982). These publications provide statistics of the wind and cross wind and of the frequency of conditions below certain thresholds of cloud, of visibility or of both, according to the wind direction and speed. The publications do not provide the particular data required for the present study. They were produced for determining the frequency of weather unsuitable for air transport services, rather than for flight training. The least stringent weather criteria for which they contain statistics is for either or both of 4 oktas or more of cloud below 15 feet and visibility less than 5 metres. The cloud and visibility limits for ab initio pilot training are much higher than these. Furthermore the publications group both day and night data whereas for ab initio training, flying is only during daylight. Nevertheless statistics were extracted from these publications. The application of published statistics is discussed in the next section. Because of the limited applicability of the published data and the fact that the computer programmes used in the airport climatologies are no longer available, an analysis was made of the weather reports from a selection of airports. The data was analysed to yield statistics of the frequency of unsuitable flying conditions for both ab initio and more advanced students. Statistics were produced for particular times of the day in each season, using the criteria in Table 1. These analyses are discussed in a subsequent section. The remainder of the paper includes interpretation of the results and discussion of additional uses of the combined wind, cloud and visibility data. USE OF PUBLSHED NFORMATON To get some initial guidance as to which airports might be suitable for more detailed study, data on sunshine was extracted for 28 airports from the sunshine normals publication (New Zealand Meteorological Service, 1985). To this was added data on
The use of New Zealand Airports for Flight Training 1 3 mean winds, average number of days per year of wind gusts exceeding 63 km/hour and average number of days per year of fog from the "Summaries of Climatological Observations to 198" (New Zealand Meteorological Service, 1983). For some airports either or both of the wind statistics were not available. For each parameter, the airports were marked according to the quartile of the range in which their data occurred with the most favourable quartile ranked one. Thus the places with the highest sunshine, least number of days with high gusts, lowest mean wind and lowest frequency of fogs received a mark of one for these parameters. Of the two wind parameters, the days of strong gusts were available for more of the locations than the mean wind data so the mean wind data was not incorporated in any further analysis. The marks for the three parameters, sunshine, wind gusts and fog were added to provide a crude index of suitability. Clearly the best locations would have a mark of three and the worst a mark of 12. The results are shown in Table 2. The most favoured locations were Tauranga, Whakatane, Napier and Woodbourne (Blenheim) with four marks, Whangarei and Nelson with five marks, Rotorua, Ohakea and Palmerston North with six. (The worst locations were Dunedin and nvercargill with Airport Kaitaia Whangarei Whenuapai Auckland Tauranga Whakatane Rotorua Taupo Hamilton New Plymouth Gisborne Napier Masterton Wanganui * Ohakea Palmerston N. * Paraparaumu Wellington * Blenheim Nelson Westport Hokitika Christchurch Timaru Oamaru Dunedin Queenstown nvercargill 1 Sunshine Sunshine (hours) class Days of gusts >63 kmihr 2 Gusts class Mean hourly wind speed (kmihr) Wind speed class 3 Days of Fog fog class 4 Combined class 2113 2 58.7 3 16 2 21 3 8 1923 3 31.3 1 12 1 5 239 2 44.7 3 13 1 54 4 9 291 2 56.8 3 18 4 19 3 8 2217 1 34 1 17 3 16 2 4 2325 1 29.8 1 2 2 4 2151 2 3.2 1 12 1 2 3 6 25 3 49 4 7 1981 3 92 4 7 2157 1 79.5 4 2 4 18 3 8 2173 1 55.3 3 14 2 41 4 8 2187 1 47.7 2 17 3 7 1 4 1944 3 17 3 1 2 5 233 2 76.3 4 1 2 8 274 2 55.3 3 16 2 3 1 6 29 2 53.2 3 2 1 6 243 2 82.5 4 3 1 7 26 3 173 4 27 4 6 1 8 2341 1 43.3 2 16 2 5 1 4 2372 1 35.2 1 11 1 25 3 5 1893 4 36.3 2 13 1 8 2 8 1889 4 37.3 2 11 1 17 2 8 1982 3 51.5 3 14 2 5 4 1 1828 4 3.9 1 17 2 7 1793 4 19 3 7 1694 4 68.3 4 13 2 64 4 12 1865 4 43.7 2 3 1 7 1595 4 11.5 4 17 3 5 4 12 Lower Q Median Upper Q 1916 221 2153 35.75 47.7 57.75 13 16 17 7.75 17.5 29 Table 2: Marking of New Zealand airports according to the quartile in which the data occurs. (Asterisk indicates that some of the data is for a site not at the airport.)
14 T h e use of New Zealand Airports for Flight Training the maximum mark of 12.) Of the four locations for which wind gust data was not available, Hamilton, Taupo and Oamaru all had at least seven marks from just the sunshine and fog data. However the remaining location in this category, Masterton, had a mark of five. f strong wind gusts are infrequent it could be, on the basis used here, comparable in suitability to Rotorua, Ohakea and Palmerston North. The other approach using published data involved the extraction of information from published airport climatologies. The climatologries for 17 airports were examined. These publications provide various statistical tables based on the hourly aviation weather reports. The publications examined included all those for which the overall marks were low, according to the previous analysis, with the exception of Masterton, for which there is no publication, and Ohakea. The latter is a military airport and not available for civil flight training. A few additional airports were selected either because it was considered they might actually be more suitable than the above analysis suggested or because there appeared to be logistical advantages in operating from them. The analysis began by noting the proportion of observations used in the published statistics that were between 8 and 17 hours, local time. This was taken as an estimate of the proportion of daytime data. t varied from 42% at the international airports ofauckland and Christchurch, where observations are made routinely on the hour throughout the day and night, to 97% at Whakatane and Taupo. This difference causes complications in interpreting the data. At those airports where the published data includes many night observations, the statistics for unsuitability because of wind or 2 Percentage unsuitable: summer Windixwind: light Additional, cloud/visibility: dark 2 Percentage unsuitable: autumn Wind/mind: light Additional, cloud/visibility: dark 1 18 16 16 14 a 12 1 8 6 4. 12 1 1!!!!! 1 _ 2 2 2 %- 2 P, _ '' 2 5 '' 2 2 2 5 2 8 2 1 16 Percentage unsuitable: winter Wind/mind: light Additional, cloud/visibility: dark 2 16 Percentage unsuitable: spring Wind/mind: light Additional, cloud/visibility: dark 14 6 1 1 z 2 i'.2 2 ' C ; i g 2 5, 8 i Figure 1: The percentage of times when weather conditions are unsuitable based on airport climatology publications. Unsuitability is based on any of wind greater than 2 knots, cross wind on the main runway greater than 17 knots, 4 oktas or more of cloud less than 15 feet and visibility less than 5 metres. The percentage of the time unsuitable because of wind is shown in light shading. The additional percentage of times when cloud or cross wind makes the airport unsuitable is shown in heavy shading. The codes for each airport are as in Table 3.
The use of New Zealand Airports for Flight Training 1 5 cross wind might be expected to be better than the daytime statistics. On the other hand the frequency of low cloud or poor visibility may be worse at night so the airports with many night observations could also appear to be worse for flight training than they actually are. The tables used were those that yield the frequency of 4 oktas or more of cloud below 15 feet, a visibility of less than 5 metres or both for wind speed and direction classes and also the overall wind summary for the same classes. These summaries are available for each season (Summer = December, January, February, etc). The wind speed classes include calm, 1-5 knots, 6-1 knots, etc up to 36-4 knots and over 4 knots. Winds are reported to the nearest 1 degrees but the tables combine adjacent directions: 36-1' True, 2-3' True etc. t was not practicable to extract data precisely equivalent to that in both categories of Table 1. The technique used was to first of all determine the frequency of all winds greater than 2 knots. An approximation was then made to determine the number of cross winds greater than fifteen knots. This involved the assumption that winds in any speed-direction category had the mean values for that category. Thus wind in the 15-2 knot range from directions within 56' of the (True) main sealed runway direction were also considered unsuitable on the assumption that the cross wind exceeded 15 knots. The total frequency of reports below the cloud-visibility criteria was determined. From this number were removed any reports already counted as unsuitable because of the wind or cross wind. Finally an overall frequency of unsuitable conditions was determined by adding the frequency of reports only unsuitable because of poor visibility or low cloud to the frequency of reports unsuitable because of wind or cross wind. The results of this analysis for each season is shown in Figure 1. The airports are shown approximately from north to south. The lower column for each airport represents the frequency of unsuitable conditions because of wind or cross wind and the upper column represents the additional frequency Airport Per cent of Observations 8-17 (Mean of seasons) Average per cent of time Unsuitable Whangarei WR 75 1.64 11 Auckland AA 42 1.49 9 Hamilton HN 72 9.9 8 Tauranga TG 59 9.26 5 VVhakatane WK 97 7.74 4 Rotorua RO 51 11.58 12 Taupo AP 97 7.4 2 Gisborne GS 5 7.42 3 Napier NR 75 1.64 1 Wanganui WG 77 15.72 15 Palmerston North PM 86 9.63 7 Blenheim WB 67 5.73 1 Nelson NS 46 8.8 6 Christchurch CH 42 18.22 17 Wigrram WG 81 16.89 16 Timaru TU 74 13.78 13 Oamaru OU 73 14.12 14 Rank Table 3. Mean frequency of unsuitable conditions for the four seasons for 17 airports and the ranking of the airports based on this frequency. Note that the data includes all observations made. The proportion of observations between 8 and 17 local time is shown to give an approximation to the number of observations in daylight. (Airport codes used in this Table are also used in the figures.)
16 T h e use of New Zealand Airports for Flight Training unsuitable only because of low cloud or poor visibility. While the four seasonal diagrams look superficially similar, there are some differences in the ranking of individual airports between seasons. As examples, Palmerston North's ranking goes from second best in winter to 12th in summer and Timaru, while generally among the least favoured locations, is ranked fifth best in winter. The overall ranking of Palmerston North is 7th. Figure 1 also shows that at some airports, notably those in the east of the South sland but also including Rotorua, cloud and visibility is the main factor leading to unsuitability. On the other hand, wind or cross wind is much more significant at Auckland and Wanganui. At many of the other airports the contributions of wind and cross wind and of cloud and visibility are of similar magnitude. The results are summarised in Table 3. The least favourable airports are those in the east of the South sland. The most favourable are those in the north of the South sland, with Blenheim ranked first and Nelson sixth, and those in the centre to northeast of the North sland, with Taupo ranked second, Gisborne third, Whakatane fourth and Tauranga fifth. The other two airports in this general area, Napier and Rotorua are less favourable. Rotorua's high frequency of unsuitability due to low cloud or poor visibility has been noted. Napier is significantly affected by wind. The main runway at Napier is approximately north-south and there is a high frequency of significant cross winds, particularly westerlies. The above results need to be considered with caution. Some of the airports might be more favourable if the analysis also included Airport Data period Comments Total reports Reports rejected Whangarei Jul 79 - Sep 88 9841 51 Tauranga Aug 67 - Jan 89 Not all daytime synoptic hours for whole period 26469 167 Rotorua Apr 64 - Sep 95 636 39 Gisbome Dec 61 - Sep 95 7426 21 Napier Aug 67 - Nov 95 Not all daytime synoptic hours for whole period Palmerston North Jan 65 - Dec 7 Jul 79 - Sep 88 Mar 95 - Nov 95 Woodboume (Blenheim) Jan 7 - Dec 75 Jul 79 - Mar 87 Jan 95 - Nov 95 3844 94 19612 95 23755 85 Nelson Dec 61 - Sep. 95 7181 41 Table 4. Synoptic data used for detailed study. The total number of reports includes all synoptic reports made, day and night. Reports were rejected because of errors or when there were only a few reports in a particular three month season.
The use of New Zealand Airports for Flight Training 1 7 the possibility of reducing cross wind by using any other runway. n the case of all the airports except Christchurch, any other runways are unsealed and therefore often unsuitable for flight training when they are wet. Moreover some of them are rather short for flight training Other reasons for caution include the short data records, as little as four years, in some cases, the different numbers of daylight observations and the fact that the criteria for unsuitability were not exactly as in either criterion of Table 1. n order to obtain statistics of airport suitability that corresponded precisely with Table 1 it was necessary to undertake a new analysis of archived records. Hourly weather reports from airports are not routinely archived by the National nstitute of Water and Atmospheric Research Ltd (NWA). However NWA holds an archive of synoptic (three hourly) reports from airports that includes wind, cloud and visibility data. The synoptic data was obtained for eight airports, Whangarei, Tauranga, Rotorua, Gisborne, Napier, Palmerston North, Woodbourne (Blenheim) and Nelson. This group includes many of the airports identified as among the most favourable in the earlier parts of this study. Data from Whakatane was not available. All synoptic reports for the periods listed in Table 4 were examined. The reports include the wind speed in knots, the wind direction to the nearest 1 degrees (True), the visibility in metres and information on clouds. The amount (in oktas) and height above the airport (in feet) of the lowest cloud are given. A second layer is included if it is more than three oktas and a third layer if it is more than five oktas. The exception to this procedure is that any layer of cumulonimbus cloud is always included so there may be up to four cloud groups. Examination of the data revealed that the archived cloud base heights were unusual. They were generally just below a round number of feet. J. Sansom (pers comm) FREQUENCY OF UNSUTABLE CONDTONS: AB NTO, YEAR WindDrwind: Left Cloud/visibility: Centre Either or both: Right 9 8 7 6 5 4 3 2 1 _., 1 PM B R G S R O T G W R N S V V B Figure 2: The percentage of times when weather conditions are unsuitable for ab initio flight training on an annual basis based on synoptic reports at 9, 12 and 15 local time. For each airport unsuitability, because of wind, cross wind or both is shown in light hatching, unsuitability because of visibility or cloud is shown in dark hatching and unsuitability for any reason is in black. The codes for each airport are as in Table 3.
18 T h e use of New Zealand Airports for Flight Training advised that the data, originally reported in feet had been converted to metres and then back to feet with some downward adjustment occurring due to rounding. This was corrected. Some of the winds were reported as being of variable direction. n these cases a worst case was assumed, the cross wind was taken to be the same as the wind speed. ncomplete reports were rejected. Examples are reports with a wind speed and no direction or with an amount of cloud given for a layer but without a height being specified for the layer. When there were only isolated days in a given quarter with data, these days were also excluded. The data was analysed for all synoptic hours separately for all seasons, using the same seasonal classification as for the published climatologies. During the period of the data, daylight saving was introduced to New Zealand. The start and finish dates for Daylight Time have differed year to year. These changes were ignored. Data was grouped according to the current local time. The reports were classified according to whether the wind or cross wind or both were unsuitable for flying, whether the cloud or visibility or both were unsuitable and whether any of the parameters were unsuitable. Unsuitability was determined separately for ab initio (Al) and more advanced (MA) students using the criteria in Table 1. Data for 9, 12,15 and 18 hours was used for summer and for all but 18 for the other three seasons. This essentially groups all daytime data. An annual analysis using 9,12 and 15 hours data was also produced. The Al results are in Figure 2, which shows the annual data, and in Figure 3, which illustrates results for the seasons separately. t is noteworthy that the frequency of unsuitable conditions is high. The annual statistics for Nelson, Woodbourne (Blenheim) and Gisborne show that these places are unsuitable for ab initio flying just under half the time - the frequencies are.446 for Nelson,.465 for Woodbourne and.475 for Gisborne. At all other airports conditions are unsuitable much more than half the time. With the exception of Whangarei, which was clearly the least suitable place, wind or cross wind contributes more to unsuitability than cloud or visibility. When the seasonal results are FREQUENCY OF UNSUTABLE CONDTONS: AB NTO, AUTUMN 9 6 7 6 5 OA.3 2 1 FREQUENCY OF UNSUTABLE CONDTONS: AB NTO, SUMMER 9.8.7.6.5 OA 1.3 1 2 ' 1 ; 1 PM ER OS RO G WE US WE PM N R G S R O T O W E N S W E. 2 6 o s 4 2 1 FREQUENCY OF UNSUTABLE CONDTONS: AB NTO, WNTER FREQUENCY OF UNSUTABLE CONDTONS: AB NTO, SPRNG 9 OS 7.6 5 4,3 2 1 PM N M O S R O T O W E N S W E PM N M O S M O T G W E N S W E Figure 3: The percentage of times when weather conditions are unsuitable for ab initio flight training in each season based on synoptic reports at 9, 12 and 15 local time for autumn, winter and spring and in addition to these times, on 18 local time reports in summer. Shadings are as in Figure 2. The codes for each airport are as in Table 3.
The use of New Zealand Airports for Flight Training 1 9 compared, Gisborne is the most favourable location in summer and Nelson and Woodbourne are both appreciably more favourable than any of the others in winter. n the other two seasons, Gisborne, Nelson and Woodbourne are the most suitable with the differences between them quite small. Nevertheless the frequencies of unsuitability for wind, cross, wind, visibility and cloud combined are significantly different at the 5% level for all seasons between all pairs of airports. The MA results are in Figures 4 (seasons) and 5 (yearly). The frequencies of unsuitable conditions are clearly very much lower with the MA thresholds. The much less restrictive wind and cross wind thresholds lead to a situation whereby cloud and visibility become the principal contributors to unsuitability in the MA case. Woodbourne is the most favourable location in all seasons. On an annual basis it is unsuitable less than one tenth of the time. Nelson and Tauranga are second and third best in all seasons. Gisborne, is ranked less highly than in thea case, being behind not only Woodbourne, Nelson and Tauranga, but also Napier. On an annual basis the differences between airports for the combination of all parameters, wind, cross wind, visibility and cloud, are significantly different at the 5 per cent level but not all the differences are significant in every season. t is interesting to note the position of Palmerston North in the ranking of the eight airports. For the ab initio students it ranks 6th in all seasons. There are about three unsuitable times at Palmerston North for every two at any of Gisborne, Woodbourne or Nelson. For the more advanced students Palmerston North ranks seventh or eighth in all seasons. On an annual basis there are more than twice as many unfavourable times at Palmerston North as at Woodbourne and 5 per cent more than at Nelson. DSCUSSON The analysis of the synoptic reports generally confirms the impression gained from the earlier components of the study that there are places significantly more suitable for flight training than is Palmerston North. The two airports studied that are located in the north of the South sland are confirmed FREQUENCY UNSUTABLE: MORE ADVANCED, ANNUAL Winclawind: left, Cloud/Visibility: centre, Either/Both right 25 2 15-1 - 5 PM N R G S R O T G W R N S W S Figure 4: The percentage of times when weather conditions are unsuitable for more advanced flight training on an annual basis based on synoptic reports at 9, 12 and 15 local time. Shadings are as in Figure 2. The codes for each airport are as in Table 3.
T, 2 The use of New Zealand Airports for Flight Training FREQUENCY OF UNSUTABLE CONDTONS: MORE ADVANCED, AUTUMN FREQUENCY OF UNSUTABLE CONDTONS: MORE ADVANCED, SUMMER 25.2 25 5 1 14: 15-1 -.5 5 - ' A 1-- 1 1 1 PM N R G S R O 1 G V V R M S W e PM NR GS R O T G W R M S WB FREQUENCY OF UNSUTABLE CONDTONS: MORE ADVANCED, SPRNG FREQUENCY OF UNSUTABLE CONDTONS: MORE ADVANCED, WNTER 25.3 2.25 15 Olin 1 PM M R G S R O T O W R M S W B.2.15,1,5 PM N R O S R O S Figure 5: The percentage of times when weather conditions are unsuitable for more advanced flight training in each season based on synoptic reports at 9, 12 and 15 local time for autumn, winter and spring and in addition to these times, on 18 local time reports in summer. Shadings are as in Figure 2. The codes for each airport are as in Table 3. as being very good locations, while Gisborne and Tauranga in the northeast of the North sland are also confirmed as good sites, the former for ab initio flying and the latter for more advanced students. There may be other airports that would be suitable for flight training. The high frequency of suitability noted at Taupo from the published airport climatology suggests that this may be a site worthy of further consideration. Even some of the sites, not evidently attractive from the published climatologies, may be in fact more suitable than these reveal. Thus Christchurch has a relatively high frequency of cloud below 15 feet or visibility below 5 metres. t may be that the frequency of cloud between 15 and 25 feet and visibilities between 5 metres and 3 kilometres is relatively low so that Christchurch is not as unsuitable for flight training as the published climatology data suggests. On the other hand the published climatologies showed that Palmerston North had a fairly low frequency of cloud below 15 feet or visibility below 5 metres in winter but Palmerston North does not show up as favourable in winter in the analysis of the synoptic reports. This is probably because cloud bases of around 2-25 feet are fairly common in Palmerston North. Results might also differ if allowance was made for grass runways. This would not only extend the possibilities to places such as Ashburton or Masterton but might make the frequency of useability of some of the airports already studied higher. f rainfall data was used together with the airport weather reports one could make some simple assessments of when the grass runway was likely to be useable. The present study considers only wind (and cross wind), cloud and visibility at the airport. There are other meteorological factors that need to be considered but for which there is no quantitative data. t has been suggested for example (J. Rankin, pers. comm.) that WoodbourneAirport is not as attractive as the present study suggests. Although flying conditions are often very good at the airport, the favourable weather is restricted to a limited area. A further factor that might restrict the use of some airports is the
The use of New Zealand Airports for Flight Training 2 1 frequency of significant turbulence. There may be places which get frequent low level turbulence without there being strong winds at the airport. This is suggested as a possibility at Nelson (New Zealand Meteorological Service, 1982).Another factor is the incidence of frost. Frost has to be removed from aircraft, and not recur, before flight training can commence. Thus frost would impact on flight training time in the colder months at places such as Nelson and Taupo. Finally there are non-meteorological factors to be considered. These include existing level of activity at the airport, the availability of air traffic services and issues such as accommodation for aircraft, students and instructors. The events of the last two years also demonstrate that a partially meteorological factor, the distribution of volcanic ash, can significantly disrupt flight training. t would be desirable to be able to predict seasonal useability of airports for flight training One step in this direction might be to develop a statistical link of seasonal useability with the Southern Oscillation ndex. As an initial step in this direction, the relatively short and broken data record for daytime useability in summers at Palmerston North was compared with the standardised Tahiti minus Darwin Southern Oscillation ndex as provided by NOAA on the nternetllr. No significant correlation was established. t is noteworthy perhaps that in 1983 when the Southern Oscillation ndex was at a record low level (-4.2 in January), the useability of Palmerston North for ab initio students was the lowest among the 16 summers. The airport would have been useable for these students only 16% of the time. Further examination of this topic should separately examine winds, cloud and visibility. The possibility of establishing the interannual variability of the four weather parameters was anticipated in the course of this study. For each synoptic hour (both day and night) the data for every quarter was classified into seven ranges of visibility and of cloud base (4 oktas or more) and into 5 classes of wind and cross wind. This data makes it possible to undertake analyses of the variability each of these parameters between seasons. While it has applications to airport climatology some of the data, particularly that on cloud may have applications to study of climate and climatic change generally. ACKNOWLEDGMENTS This work was made possible as a result of funding from the Board of the School of Aviation. The assistance of Gavin Miller of the School's Flight Systems Centre in establishing the weather criteria for flight training is acknowledged. also wish to acknowledge the assistance of John Sansom of NWA with the provision of the data and of staff of Massey Computing Services in transferring it to me. School of Aviation undergraduate students from 1994 to 1996 participated in the extraction of data from the published climatologies. REFERENCES New,..Zealand Meteorological Service 1982: The Climatology of Auckland nternational Airport. NZMS Misc Pub 171(2). Wellington, 2 pp. Also additional publications in the NZMS Misc Pub 171(x) series on other airports. New Zealand Meteorological Service, 1983: Summaries of Climatological Observations to 198. NZMS Misc Pub 177 Wellington, 172 pp. New Zealand Meteorological Service, 1985: Sunshine normals 1951 to 198. NZMS Misc Pub 186. Wellington, 28 pp. [1]* Source is http://nic.flanoaa.govidata/cddb/cddbisoi.
22 T h e use of New Zealand Airports for Flight Training