Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents

Involving Smaller Aircraft

1 Introduction

In 2001, AEA Technology completed a risk assessment study on behalf of the

Norwegian Civil Aviation Authority to support the development of national rules for

aerodrome physical design that address the requirements identified in ICAO Annex 14.

The findings and recommendations arising from that study have led to the development

of proposals for aerodrome physical design by the Norwegian Civil Aviation Authority

and these have been subject to review and comment by interested parties during the

course of a consultation exercise.

Comments have been received in response to the consultation exercise concerning the

validity of the overrun risk modelling approach that was used in the development of

recommendations concerning RESA length provisions. Specifically the possibility that

the model may not be representative of the behaviour of smaller aircraft or of the

performance of commercial carriers (as distinct from general aviation) has been raised.

The original studies undertaken by AEA Technology made some initial assessment of

the significance of aircraft size in determining overrun risk and no clear correlation

between the two was observed. The modelling approach originally proposed also took

some account of the better safety performance of certain types of operation.

However, it is recognised that the initial model development did not exhaustively

consider all of the points that have been raised during the consultation process. To

address these concerns some more specific and targeted studies have been undertaken to

determine the validity of the application of the model to the operation of smaller aircraft

by commercial carriers.

2 Model Background

The model for estimating risk is based on empirical data concerning historical overrun

incidents and provides for the quantitative determination of:

• the likelihood of an overrun accident occurring on either take-off or landing;

• the likely distance travelled in the event that either a take-off or landing overrun

occurs.

The modelling approach allows for the use of different likelihoods of occurrence of

overruns, according to the nature of operations. Different rates of occurrence have been

EXHIBIT

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Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

determined for take-off and landing events and, for landing, rates applicable for

precision approach and visual/non-precision approach have been identified.

Two different models for the likely distance travelled in the event of an overrun were

developed, the one addressing take-off overruns and the other addressing landing

overruns.

In assessing the validity of the model in describing the types of operation of interest it

will be important to consider these two elements of the model, that relate to first the

frequency and second the consequence of an overrun and that together determine the

overall risk.

3 Revised Analysis

3.1 OVERRUN CONSEQUENCE

3.1.1 Analysis Method

For the purposes of the model, the consequence element of risk is determined according

to the distance beyond the runway end that an aircraft travels in the event of an overrun.

In order to test the validity of this element of the model, selected data sets

corresponding with smaller aircraft and those operated by commercial carriers only

were analysed in the manner employed during the original model development process.

In the first instance, two data subsets comprising all aircraft with a maximum certified

gross weight ofless than 30 tonnes were compiled separately for the available take-off

and landing overrun data. The largest aircraft within these selected data sets was found

to be the HS 748, with a weight of 46500 lbs, equivalent to 21.1 tonnes.

Further selected data sets were then compiled that comprised operations by commercial

carriers only. The majority of these were identified within the available data set as

undertaken in accordance with FAR Part 135. A much smaller number were undertaken

in accordance with FAR Part 121. For the non-US operations (from Canada and the

United Kingdom) data were included in the commercial carrier data sub-set where

operations were identified as passenger, scheduled passenger, non-scheduled passenger,

freight, scheduled freight or non-scheduled freight. All data relating to general aviation,

most of which was subject to FAR Part 91 rules and representing a mixture of business,

corporate, personal, positioning, maintenance and training flights was thus removed.

A selected data set comprising turboprop aircraft only was also compiled for landing

and take-off overruns.

The data sets were then analysed by plotting cumulative probability distribution

functions describing the probability of travel to a given distance or beyond and

exponential fits to the observed distribution functions were determined. The results

obtained for the various sub-sets of data were then compared to determine whether any

significant differences could be identified between them. The forms of the distributions

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Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

functions derived from the empirical data were reviewed to determine the quality of the

fit and extent to which they might provide a reliable basis for the prediction of the

expected behaviour.

Finally, the available narrative describing the event sequences to which the identified

data relate was reviewed to determine whether there may be any justification for

excluding any data points. For take-off overruns, an outlying point relating to a take-off

from the wrong runway was eliminated on the basis that this would not be

representative of the Norwegian cases of interest. There may be some justification also

for eliminating a second outlying point relating to an incident in which an aircraft

became airborne before developing a problem and returning to the runway. Such an

incident may be regarded as not being an overrun and hence may be considered to be

beyond the scope of incidents that the RESA provision can be expected to

accommodate.

3.1.2 Landing Overrun Analysis Results

The data sub-sets compiled for landing overrun are summarised in Appendix 1 and the

data is presented graphically in Appendix 2. The available data set includes 67 landing

overruns involving smaller aircraft «21.2 tonnes) and 22 of these cases involved

commercial carriers, the majority of which were subject to FAR Part 135 Rules and

were dual pilot operated flights.

The different data sets give generally similar results that are consistent with the value

originally proposed for the distribution function based on the complete data set,

including events that involved larger aircraft in excess of 30 tonnes. There is an

indication that landing overruns involving turboprop aircraft result in generally slightly

shorter overrun distances than is found for smaller jet and turboprop aircraft as a whole

but, due to the presence of two outlying points that have a significant influence on the

exponential function, this is not reflected in the modelled cumulative probability

distribution function. Similarly, landing overruns involving commercial carriers appear

to result in slightly shorter overrun distances than is found for smaller aircraft as a

whole. There is one significantly outlying point within the commercial carrier data set,

with an overrun distance of 478 m and review of the available narrative reveals that this

relates to unusual circumstances. The incident involved a power off forced landing with

a touchdown well beyond the threshold. On that basis it might be argued that it is

unrealistic to expect standard RESA provisions to protect against this type of extreme

incident and a further refined data sub-set with this data point removed has also been

analysed.

The distribution functions determined for the various data sub-sets are summarised

below:

• Original distribution function "best estimate" (all data): M(x) = exp (-0.0081 x)

• Original distribution function "lower bound" (all data): N, (x) = exp (-0.0101 x)

• New small aircraft distribution function: M(x) = exp (-0.0075 x)

• Small turboprop only distribution function: N,(x) = exp (-0.0072 x)

• Small aircraft, commercial carrier distribution function: M(x) = exp (-.00079 x)

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Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

• Small aircraft, commercial carrier, extreme outlying point removed distribution

function: N/(x) = exp (-0.0103 x)

It may be noted that, when using an exponential function of the form exp (- a x) to

represent a distribution function, the larger the coefficient a the quicker the function

falls off with distance. The last function, derived from the small aircraft and

commercial carrier data set with the outlying point removed is seen to give the most

rapid fall off with distance but is not seen to be very greatly different from the

distribution functions originally proposed on the basis of the full data set. This data

provides a function that is very close to the "lower bound" function used in the original

assessment.

Review of the data and the extent to it correlates with the exponential distribution

functions indicates that the functions that have been determined provide a sensible basis

for modelling in the area of primary interest, i.e. up to ofthe order of300 metres from

the runway end. The log plot for the small aircraft and commercial carrier data set with

the outlying point removed gives good linearity throughout the range and there is no

indication that the function truncates rapidly before 300 metres: it is concluded that the

function should give a reasonably reliable basis for extrapolation beyond the immediate

limit of the empirical data set.

The data set is found to include a number of points in the region of more particular

interest in the current context: i.e. in the range at or beyond the 150 m limit of the ICAO

standard distance of runway end strip plus RESA for a Code 3 & 4 instrument runway.

Six out of 22 points (27%) are found to lie in this region, the furthest being an overrun

of 260 metres (with 2 points of these located at 152 metres) and the empirical data

therefore demonstrates that a non-trivial proportion of smaller aircraft operated by

commercial carriers can be expected to travel a distance of 150 metres or more during a

landing overrun. The best fit exponential distribution function indicates 21.3 % of

landing overruns travelling to this distance or more. The original model predicts a

slightly higher proportion of 29.7% oflanding overruns travelling to 150 metres or

more.

3.1.3 Take-off Overrun Analysis Results

The data sub-sets compiled for take-off overrun are summarised in Appendix 3 and the

data is presented graphically in Appendix 4. The available data set includes 21 take-off

overruns involving smaller aircraft «21.2 tonnes) and 10 ofthese cases involved

commercial carriers, the majority of which were subject to FAR Part 135 Rules.

As was found for the landing overruns, the different subsets of data exhibit comparable

distributions and are generally consistent with the model previously proposed on the

basis of the complete data set including larger aircraft. Again, having regard to the

available narrative, a data sub-set excluding the most extreme point was analysed, this

point corresponding with an incident in which an aircraft became airborne before

developing a problem and returning to the runway.

The distribution functions determined for the various data sub-sets are summarised

below:

• Original distribution function "best estimate" (all data): Nt (x) = exp (-0. 0058 x)

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Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

• New small aircraft distribution function: Nt (x) = exp (-0.0051 x)

• Small turboprop only distribution function: Nt (x) = exp (-0.0042 x)

• Small aircraft, commercial carrier distribution function: N, (x) = exp (-0.0039 x)

• Small aircraft, commercial carrier, extreme outlying point removed distribution

function: N,(x) = exp (-.00051 x)

The starting data set is somewhat smaller for take-off overruns than landing overruns,

take-off overruns being generally less frequent events. The selected data sub-sets are

therefore somewhat small and the cumulative probability functions derived from them

are correspondingly subject to some statistical uncertainty. It may be noted that the

distribution function derived from the small aircraft and commercial carrier data sub-set

indicates a generally higher probability of overrun to greater distances than the function

derived previously on the basis of all data including larger aircraft. Four out of 9 points

(44.4%) in the data set for small aircraft operated by commercial carriers with the

extreme outlying point removed are found to lie beyond 150 m and the empirical data

therefore demonstrates that a non-trivial proportion of smaller aircraft operated by

commercial carriers can be expected to travel a distance of 150 metres or more during a

take-off overrun. The original model based on the full data set indicated 41.9% of takeoff overruns travelling to this distance or more and the new model based on smaller

aircraft operated by commercial carriers indicates a slightly higher proportion of 46.5%

travelling to this distance.

3.1.4 Conclusions

Our overall conclusion is that the model developed for predicting the distance travelled

in the event of either a take-off or a landing overrun using the complete data set that

included larger as well as smaller aircraft provides a generally good representation of

the behaviour of smaller aircraft «21.2 tonnes) operated by commercial carriers.

Similar behaviour, within the general limits of the statistical uncertainty of the data sets,

was observed whichever way the data was divided. That is to say that, as far as the

distance travelled during an overrun is concerned, smaller and larger aircraft exhibit

similar behaviour, turboprop and jet aircraft exhibit similar behaviour and aircraft

operated by commercial carriers and general aviation exhibit similar behaviour.

In the case of landing overruns, a new model, based on smaller aircraft data alone

predicts slighter shorter overrun distances whereas in the case of take-off overruns such

a model predicts slighter longer overrun distances. The models based on the restricted

data sets, in particular that for take-off, are subject to some uncertainty due to the

limited number of data points available and the observed differences in the predictions

of the various models may not be significant.

3.2 OVERRUN FREQUENCY

The original analysis of overrun frequency undertaken by AEA Technology specifically

sought to derive a value that is appropriate to commercial carriers. Specific data on the

numbers of overruns and movements for commercial carriers from which to derive an

overrun rate for commercial carriers was not readily available but data on the rate of

overruns for commercial carriers involving a total loss of the aircraft was available.

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Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Using information on the proportion of overruns that result in a total loss, an overrun

rate for commercial aircraft was derived. The value obtained should therefore not be

influenced by a high rate of overruns for general aviation. The basic accident rate that

served as the basis for the model was based on "first world operations". It specifically

excluded all business jet aircraft and identified rates for turboprop aircraft and larger jet

aircraft separately, thereby ensuring that any higher rate of accident in certain types of

operation (e.g. commuter / air taxi operations in the US that are undertaken in

accordance with FAR Part 135 requirements rather than the more stringent FAR Part

121 requirements) not applicable to the current case could be accounted for, assuming

that the observed large jet accident rate is generally representative of the highest

standard of operation.

Consideration was given to the dependence of overrun rate during landing on the

availability of precision approach landing aids. Available data indicates that the

precision approach landing overrun rate is significantly lower than the rate encountered

during non-precision and visual approach operations. The "best estimate" overrun rates

determined in the previous studies are as follows:

• Take-off overrun rate: 0.33 per million movement movements;

• Average landing overrun rate: 1 per million movements;

• Precision approach overrun rate: 0.6 per million movements;

• Non-precision/visual approach overrun rate: 4.68 per million movements.

Some uncertainty in the method for determining these rates was noted in the original

report and "lower bound" rates that are half the above values were also proposed.

A further factor investigated in the previous study was the dependence of overrun rate

on the amount of runway available in excess of the identified landing distance required

for the operation concerned. The analysis performed indicated that the overrun rate

where no excess runway is available is of the order of ten times higher than the average

rates indicated above. Where the amount of excess runway is more than the order of

750 m, the overrun rate is found to be very much lower than the above average values.

It may be noted that half of the identified smaller aircraft take-off overrun incidents

involved non-commercial carrier (general aviation) operations and two thirds of the

smaller aircraft landing overrun incidents involved non-commercial carriers. These are,

however, very much the minority of incidents as a whole. General aviation accounted

for 36 out of 118 landing incidents for which overrun distances are available and for 7

out of 39 take-off incidents for which overrun distances are available. On that basis it

may be concluded that, even if the attempts to exclude non-commercial carrier overruns

from the data upon which the incident frequencies were based were not to have been

successful the impact on the estimated commercial carrier rate would be limited (less

than a 30% overestimate of the landing overrun rate and less than a 20% overestimate of

the take-off overrun rate).

The same general argument applies to the possible influence of higher rates of certain

types of commercial carrier operation (e.g air taxi / commuter operations). The

numbers of overruns within the database relating to different types of non-general

aviation operations is summarised below in Tables 1 & 2, for take-off and landing

operations respectively.

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Risk Analysis in Support of Aerodrome Design Rules:

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Table 1: Take-off Overrun: Categories of Non-GA Operations

Type of Operation Number of Incidents

Part 121 16

Part 129 1

Part 135 8

Other / Non-US 6

Table 2: Landing Overrun: Categories of Non-GA Operations

Type of Operation Number of Incidents

Part 121 24

Part 129 2

Part 135 16

Other / Non-US 22

The largest single contribution to the total number of incidents is made by Part 121

operations and these comprise the majority of US operations. (A significant

contribution to the total is made by non-US operations (UK, Canada, Australia) and

these operations cannot be split in accordance with US operating rules.) It is to be

emphasised that the incident rate employed in the risk assessment is based on the

historical accident rates determined for different aircraft types (commercial jets,

turboprop and executive jets). The majority of the Part 135 accidents are found to relate

to executive jet operations and will therefore not have been counted in the estimation of

incident rates. On that basis it is concluded that any higher rate of incidents for certain

types of Part 135 operations will have a negligible impact on the overall incident rates

employed in the modelling exercise. The possible influence of such a higher rate can be

accommodated by use of a "lower bound" value for the incident rate when determining

the overall risk, as described in the following section.

3.3 REVISED RISK ESTIMATION

Using the modelling approach used previously, risk estimates have again been derived

for various lengths of runway end strip and RESA. On the basis of the foregoing

analysis, we identify the following model parameters as the most optimistic values that

might be justified:

• Take-off overrun "lower bound": 0.167 per million movements;

• Landing overrun "lower bound" precision: 0.3 per million movements;

• Take-off overrun distance, original "lower bound" function: N, (x) = exp (-0.0065 x)

• Landing overrun, revised smaller aircraft function: N, (x) = exp (-0.0103 x)

Risk estimates based on these values for various runway end strip and RESA distances

have been calculated and are presented below in Table 3. The total risk mitigation

benefit associated with RESA provision also includes an element associated with

undershoot and this is included in the data in the table.

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Risk Analysis in Support of Aerodrome Design Rules:

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Table 3 Residual Risk Estimates according to RESA/strip length

Distance/m Overrun Risk

Take-off Landing Mean Undershoot Total risk

10 0.15649 0.270638 0.213564 b.125782 0.276455

20 0.146642 0.24415 0.195396 0.1 07921 0.249356

30 0.137413 0.220254 0.178834 0.095382 0.226525

40 0.128766 0.198697 0.163731 0.085661 0.206562

50 0.120662 0.17925 0.149956 0.077744 0.188828

60 0.113068 0.161706 0.137387 0.0711 0.172938

70 0.105953 0.14588 0.125916 0.065409 0.158621

80 0.099285 0.131602 0.115443 0.060458 0.145672

90 0.093037 0.118722 0.105879 0.056101 0.13393

100 0.087182 0.107102 0.097142 0.052231 0.123257

110 0.081695 0.09662 0.089157 0.048767 0.113541

120 0.076554 0.087163 0.081859 0.045647 0.104682

130 0.071736 0.078632 0.075184 0.042821 0.096594

140 0.067222 0.070936 0.069079 0.040249 0.089203

150 0.062991 0.063994 0.063492 0.037898 0.082442

160 0.059027 0.05773 0.058379 0.035743 0.07625

170 0.055312 0.05208 0.053696 0.03376 0.070576

180 0.051831 0.046983 0.049407 0.03193 0.065372

190 0.048569 0.042384 0.045477 0.030237 0.060595

200 0.045513 0.038236 0.041875 0.028666 0.056208

210 0.042649 0.034494 0.038571 0.027207 0.052175

220 0.039965 0.031118 0.035541 0.025848 0.048465

230 0.03745 0.028072 0.032761 0.024579 0.045051

240 0.035093 0.025325 0.030209 0.023394 0.041906

250 0.032884 0.022846 0.027865 0.022284 0.039007

260 0.030815 0.02061 0.025712 0.021244 0.036334

270 0.028876 0.018593 0.023734 0.020267 0.033868

280 0.027058 0.016773 0.021916 0.019349 0.03159

290 0.025355 0.015132 0.020244 0.018485 0.029486

300 0.02376 0.013651 0.018705 0.01767 0.02754

We conclude that, on the basis of the most optimistic assumptions concerning overrun

rates and distributions, a RESA extending to 300 m from the runway end (the ICAO

recommendation for a Code 3 & 4 runway and a Code 1 & 2 instrument runway of a

60m strip plus 240 m RESA) provides risk mitigation at the TLS level of 10'8 per

movement that has been identified as a basic target to be achieved where practicable. A

RESA extending to 150 m from the runway end (the ICAO standard for a Code 3 & 4

runway and a Code 1 & 2 instrument runway of a 60m strip ..plUS90 m RESA) provides

risk mitigation to the "benchmark" quantitative target of 10' per movement that

represents the identified normal minimum recommended risk limit.

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Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

The strip lengths of 30 m and 60 m, representing the ICAO standards for Code I and

Code 2 non-instrument runways, are identified as insufficient to meet the 10-7per

movement risk level.

4 Other Issues

In addition to the comments concerning the general validity of the risk model that have

been considered in the previous section, a number of specific questions have been raised

that merit comment, as set out below.

4.1.1 Runway Length

Of 104 landing overruns where the runway length is identified 7 took place at Code 1

runways (:s 800 metres) and 10 took place at Code 2 runways (> 800 m and s 1200 m).

A further 40 took place on Code 3 runways but 12 of these are found to have occurred at

relatively short Code 3 runways (:s 1400 m). The remaining 47 took place at Code 4

runways (> 1800 m), the longest of which was 3382 metres in length. Six of the 7 Code

1 incidents involved commercial carriers, 5 of the 10 Code 2 incidents involved

commercial carriers and 5 of the 12 incidents on shorter Code 3 runways involved

commercial carriers.

For take-off overruns, of the 39 incidents for which runway length information is

available, no incidents took place on Code 1 runways, 4 took place on Code 2 runways,

7 took place on Code 3 runways and the remaining 28 incidents took place at Code 4

runways, the longest of which was 4442 metres. Of these incidents, 2 Code 2 runway

events involved commercial carriers and 4 Code 3 runway events involved commercial

carriers.

It may be concluded on the basis of this information that a significant number of

overrun incidents do take place at shorter runways and that a significant fraction of

these involve commercial carriers.

In the absence of specific information on the number of movements that took place at

runways of identified length it is not possible to make any specific conclusions

concerning the relative rates per movement of overruns at shorter or longer runways.

As was determined in the original analysis, there is clear evidence that the overrun rate

is dependent on the amount of runway available in excess of the identified landing

distance required for the operation concerned. This basic conclusion is expected to

apply to larger and smaller aircraft alike. A certain proportion of operations of smaller

aircraft can be expected to take place at relatively long runways. For example, hub and

spoke type operations between larger and smaller airports involving smaller aircraft

would be expected to involve at least lout of every two movements at a relatively long

runway. In addition, point-to-point operations for certain routes between two larger

airports where there is limited demand may involve smaller aircraft movements at long

runways only. On that basis it would be expected that the historical rate of overruns for

AEA Technology 9 19 December 2003
Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving SmalIer Aircraft

smaller aircraft may be less than that for larger aircraft. However in the absence of the

relevant data it is not possible to make any further sensible comment on this issue.

4.1.2 Approach Aid Availability

As has been discussed briefly above, previous analysis has indicated that historical

incident rates are significantly lower for operations where precision approach aids are

available. In response to a specific request, we provide the following specific

information concerning the proportion of incidents within the available data set where

different approach aids (lLS, VASI, PAPI) were available for different categories of

operation (General Aviation, Passenger and Freight).

This data is presented in the following tables.

Table 4: ILS Glide path Operations

Flight Aircraft Size

category Total Small Large

Total 36 10 26

GA 9 7 2

Passenger 25 2 23

Freight 4 2 2

Table 5: Visual with VASI glide path

Flight Aircraft Size

category Total Small Large

Total 10 9 1

GA 6 6 0

Passenger 2 0 2

Freight 3 3 0

Table 6: Visual with PAPI glide path

Flight Aircraft Size

category Total Small Large

Total 6 4 2

GA 2 2 0

Passenger 4 1 3

Freight 1 1 0

Table 7: Visual/no glide path indicator

Flight Aircraft Size

category Total Small Large

Total 6 6 0

GA 2 2 0

Passenger 1 1 0

Freight 3 3 0

AEA Technology 10 19 December 2003
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Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Table 8: No information provided

Flight Aircraft Size

category Total Small Large

Total 77 54 23

GA 34 32 2

Passenger 34 15 19

Freight 9* 7 1

* no aircraft type identified for one incident

Again, in the absence of specific information concerning the number of movements

within each of the above types of operation it is not possible to draw any firm

conclusions concerning relative incident rates. A significant proportion of incidents

take place where ILS glide path indication is available and the majority of these involve

larger aircraft. The relative proportion of incidents involving larger and smaller aircraft

is generally consistent with the relative numbers of the two types of aircraft in the

international fleet and their relative numbers of movements.

A larger proportion of incidents where VASI and PAPI glide path indication is provided

to visual approaches involve smaller aircraft. This would be generally consistent with

the expectation that more movements of smaller aircraft take place at smaller airports

with limited facilities. All the events where no glide path indication is identified

involved smaller aircraft, in line with the above comments. For those cases where no

information is provided, the majority involved smaller aircraft. We may speculate that a

good proportion of these incidents took place at airports with relatively limited

approach aid facilities.

In total, 83 incidents involved smaller aircraft and 52 involved large aircraft. The

higher number of incidents involving smaller aircraft, for which we would expect a

slightly lower number of movements, indicates a higher rate of incidents for smaller

aircraft. This observation would be consistent with a higher rate of incidents for general

aviation and, to some extent, US air taxi and commuter operations.

5 Overall Conclusions

On the basis of the above analysis we would reaffirm the conclusions and

recommendations presented in the earlier report concerning RESA and runway end strip

lengths:

• Combined length of runway end strip and RESA not less than the current ICAO

Annex 14 standard of 150 m in any runway case (basic requirement to meet a TLS

of 10-7per movement for average risk movements);

• Combined length of runway end strip and RESA preferably approaching the current

ICAO Annex 14 recommendation of300 m in relation to take-off and landing

overrun risk mitigation (objective to achieve a TLS of 10-8per average movement

where practicable and a TLS of 10-7 per movement for higher risk movements);

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Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Following re-examination of the available data in the light of the points raised, we see

no grounds in relation to the specific characteristics of smaller aircraft operations,

operations at shorter runways or characteristics of commercial carrier operations not

previously taken into account in our original analysis that would change our earlier

conclusions. The historical accident record supports the conclusion that overrun

accidents are a significant contributor to the overall rate of serious accidents involving

fatalities and total hull loss and that RESA provision, in accordance with the above

recommendations, should help to reduce the risk associated with such events.

Whichever way the available data on overrun distance is sub-divided, according to the

type of operation, comparable cumulative probability distributions are found. Smaller

and larger aircraft exhibit similar behaviour, turboprop and jet aircraft exhibit similar

behaviour and smaller aircraft operated by commercial carriers and general aviation

exhibit similar behaviour. On that basis we conclude that the available cumulative

distribution functions are generally representative of the operations of interest.

As far as the overrun incident rate element of the model is concerned, specific attention

was taken during the initial development of the model to identify a rate that was

appropriate for the types of commercial operations of interest and to ensure that this was

not an over -estimate due to the inclusion of non-representative higher risk operations in

the data set from which the rate was derived.

AEA Technology 12 19 December 2003
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Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Appendix 1: Commercial Carrier Operated Smaller Aircraft Landing Overrun Dataset

Date x/m Aircraft Engine type Type of Operation Operator Instrument / Glide Slope Indicator

01/08/81 53DHC-6 Turboprop Canadian Passenger N/A

01/10/82 3 HS 748 Turboprop UK Passenger N/A

15/06/83 30 Grumman Gulfstream G1159 Turboprop Part 135 Scheduled freight Orion Air Inc. visual - no glide path indicator

10/09/83 76 Beechcraft B-90 Turboprop Part 135 Non-scheduled passenger Mayo Aviation Incorporated visual - no glide path indicator

29/11/83 40 HS 748 Turboprop UK Scheduled passenger visual with PAPI

06/07/84 9HS 748 Turboprop Canadian Passenger Quebecair N/A

15/12/84 152 Cessna CE-500 Citation Turbofan Canadian Non-scheduled passenger Austin Airways Ltd. N/A

31/01/85 116 Fairchild SA-227 Turboprop Part 135 Scheduled freight Sat -Air Inc. RNAV/ visual, VASI glide path indication

17/11/88 60 Gates Learjet Turbofan Part 135 Non-scheduled passenger Pacific Flight, Inc. visual - no glide path indicator

15/02/89 61 Falcon 20 Turbofan Part 135 Non Scheduled freight Reliant Airlines Inc. ILS-complete and VASI

06/06/90 478 CE 208 Turboprop Part 135 Scheduled freight West Air Industries visual - no glide path indicator

02/07/91 168 Gates Learjet Turbofan Part 135 Non Scheduled freight Connie Kalitta Services Inc. visual with VASI glide slope indication

06/10/92 6 Fairchild SA-227 Turboprop Part 135 Scheduled passenger Northeast Express Regional airlines Inc. ILS-complete, including glide path

22/11/92 61 Gates Learjet Turbofan Part 135 Non-scheduled passenger Flight operations Inc. ILS-complete, including glide path indication

29/04/93 209 EMB-120 Turboprop Part 135 Scheduled passenger Continental Express, Inc. N/A

21/07/93 46 Convair 580 Turboprop Canadian Non-scheduled passenger Canair visual - no glide path indicator

26/01/96 85 Falcon 20 Turbofan Part 135 Non Scheduled freight Yip Group Inc. N/A

13/08/96 96 Gates Learjet Turbofan UK Non-scheduled passenger MAC Aviation Sociedad Anonima PAR

19/08/97 260 Fairchild SA-226 Turbofan Part 135 Non Scheduled freight Superior Aviation Inc. ILS-Iocaliser only, VASI glide path indication

18/02/98 72 Falcon Turbofan Canadian freight Reliant Airlines Inc. NDB and PAPI glide slope indication

23/05/98 152 Gates Learjet Turbofan Part 135 Non-scheduled passenger Panther Aviation visual - ILS-Iocaliser only

06/08/98 137 HS 748 Turboprop Canadian freight Wasaya Airways Ltd. visual

AEA Technology 13 19 December 2003
Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Appendix 2: Graphs of Landing Overrun Distributions for Smaller Aircraft

Figure A2.1 Plot of all data for smaller aircraft landing overruns and best

exponential fit

• All Data

• Turbo prop only

Commercial Carriers

only

--Expon. (All Data)

y = e-O.007SX

o 200 400 600

Figure A2.2 Plot of turboprop data and best exponential fit

AEA Technology 14 19 December 2003
Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Figure A2.3 Plot of Commercial Carrier only data and best exponential fit

1.2

y = e-G·0079X

R

2

= 0.9297

1

0.8

0.6

0.4

0.2

o

o 100 200 300 400 500 600

Figure A2.4 Logarithmic Plot of Commercial Carrier only data and line of best

fit

0.1

0.01

o 100 200 300 400 500 600

AEA Technology 15 19 December 2003
Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Figure A2.5 Plot of Commercial Carrier only data with outlying point removed

and best exponential fit

1.2

1

0.6

y = e-O.0103x I

R

2 = 0.9441

0.4

0.2

o 100 200 300

Figure A2.6 Logarithmic Plot of Commercial Carrier only data with outlying

point removed and line of best fit

0.1

0.01

o 50 100 150 200 250 300

AEA Technology 16 19 December 2003
Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Appendix 3: Commercial Carrier Operated Smaller Aircraft Take-off Overrun Dataset

Date

28/07/1984

13/08/1985

26/05/1987

16/08/1988

15/04/1992

12/05/1994

13/07/1994

16/08/1996

29/11/1997

28/08/1998

AEA Technology

x/m Aircraft Engine type Type of Operation Operator

35 Gates Learjet Turbofan Part 135 Non-scheduled passenger Panarama Flight Service Incorporated

274 Gates Learjet Turbofan Part 135 Scheduled freight Konnie Kalitta Services

355 BAe J-3101 Jetstream Turboprop Part 135 Scheduled passenger Air New Orleans

255 Fairchild SA-226 Turboprop Part 135 Scheduled passenger Britt Airways

o Fokker F28 Turbofan Part 121 Scheduled passenger USAir

63 Saab SF-340B Turboprop Part 121 Scheduled passenger Wings west airlines

136 Gates Learjet Turbofan Part 135 Non-scheduled passenger Mid-Atlantic Jet Carrier

250 HS 748 Turboprop UK Freight Emerald

61 Beech 1900 Turboprop Canadian Scheduled Passenger Ministic

613 Falcon 20 Turbofan Part 135 Non Scheduled freight Reliant Airlines

17 19 December 2003
Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Appendix 4: Graphs of Take-off Overrun Distributions for Smaller Aircraft

Figure A4.1 Plot of all smaller aircraft take-off overrun data and best

exponential fit

1.2

y = e-O.OO51X

R2 = 0.9632

---- - 1

y = e-O.0042X

R

2 = 0.8639

400

0.8

• Commercial carriers

Turboprop only

-Expon. (All data)

AEA Technology 18

0.6

0.4

0.2

o

o 200 400 600 800

Figure A4.2 Plot of turboprop data and best exponential fit

o 50 100 150 200 250 300 350

19 December 2003
Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

5.1.1 Figure A4.3 Plot of Commercial Carrier only data and best exponential

fit

1.2

0.4

y = e-O.0039x

R2 = 0.9638

0.8

0.6

0.2

o

o 100 200 300 400 500 600 700

Figure A4.4 Logarithmic Plot of Commercial Carrier only data and best line of

fit

0.1

y = e-O.0039x

R

2 = 0.9638

0.01

o 100 200 300 400 500 600 700

AEA Technology 19 19 December 2003
Risk Analysis in Support of Aerodrome Design Rules:

Additional Studies Concerning Overrun Accidents Involving Smaller Aircraft

Figure A4.5 Plot of Commercial Carrier only data with outlying point removed

and best exponential fit

1.2

400

0.8

0.6

0.4

0.2

o

o 100 150 200 250 300 350

Figure A4.6 Logarithmic Plot of Commercial Carrier only data with outlying

point removed and line of best fit

50

0.1

o 50 100 150 200 250 300 350 400

AEA Technology 20 19 December 2003