BIRDTAM, COLLISION PROBABILITY and BIRDSTRIKE RISK MITIGATION PROCEDURE.

Serge SORBI

Belgian Air Force - Aviation Safety Directorate

World Birdstrike Association meeting, Amsterdam 5 – 9 Dec 2016

1

Agenda

1. NATO Stanag

2. From Bird density to BIRDTAM

3. Collision probability.

4. BIRDTAM & mitigation procedure assessment.

5. Example of BAF mitigation procedure.

2

NATO STANAG

3

STANAG 3879 AFSP 1,4 Bird Intensity Scale

Participating nations agree to exchange BIRDTAM’s with neighbouring countries using the format detailed in Annex A whenever a bird intensity of 5 or greater is present,

following the intensity levels :

Intensity Bird strike Risk

0 Nil

1 Extremely small

2 Very small

3 Small

4 Fairly small

5 Fairly great

6 Great

7 Very great

8 Extremely great

Bird Intensity => BIRDTAM

4

STANAG is implemented at BAF, RNLAF & GAF by the broadcasting of BIRDTAM having influences on Ops operations.

BIRDTAM > 5

=> Flying limitations

Broadcast of BIRDTAM.

5

by Georef square via flight planning software.

What does it mean exactly ?

Usual pilots questions :

• How many birds means exactly BIRDTAM 8 ?

• What is the probability to strike a bird?

6

Answering pilots question…

7

• Bird density by altitude.

• Need of a collision probability assessment.

Probability of birdstrike

Given data: – Cube of reference : 1 km³

– Aircraft frontal cross section (m²)

– Distance travelled by the aircraft

– Number of birds (birds / km³)

Assumptions: – Birds uniformly spread

in the cube.

– Speed of birds considered as 0.

8

Probability of birdstrike

𝑃 𝑏𝑖𝑟𝑑𝑠𝑡𝑟𝑖𝑘𝑒 = 𝑁. 𝐿². 𝐷1

1010 .

𝐴

𝐿² . 104 = 𝑁. 𝐷. 𝐴 .

1

106

9

N: Number of birds per Km³ 200 V: Aircraft speed (km/h) 600

D: Distance (km) 1

A: Aircraft cross section (m²) 6,6 Probability of birdstrike after 1 hour: 0,5473

P(birdstrike) = N*D*A/10^6

Excel tool: collision probability during 1 hr flight.

Example:

A : 6,6 m² N: 200 birds / km³ Speed : 600 km/hr P(birdstrike) = 0,5473 (54%)

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5 6 7 8

BIRDTAM:

BIRDTAM thresholds assessment

7 8 BIRDTAM:

Mitigation procedure assessment by reducing collision probability

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Birds / km³ BIRDTAM F16 - 150 kt F16 - 280 Kt F16 - 400 Kt Ajet - 120 Kt Ajet- 280 Kt Ajet - 400 Kt SF-260 - 100 Kt SF-260 - 170 Kt C-130 - 170 Kt C-130 - 230 Kt

5 5 0,8 1,6 2,1 0,5 1,2 1,7 0,2 0,3 8,8 12

10 6 1,6 3,2 4,2 1 2,4 3,5 0,4 0,7 17 22

40 7 6 12 15 4 10 13 1,7 2,8 53 63

80 8 12 23 29 8 18 25 3,4 6 78 86

100 15 28 35 10 22 30 4,2 7 85 92

300 39 62 72 28 53 66 12 19 99 99

500 56 80 88 42 71 84 19 30 100 100

Probability of birdstrike after one hour expressed in %

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Mitigation procedure F16 En route / Ops area

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Local Bird Intensity Matrix Departure/Recovery / Local patterns

Combining “ground situation” (BCU obs) & BIRDTAM

=> L, M or H probability of collision

Nbr, size of birds & persistence to harassment => BCU Obs

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Mitigation procedure F16 Departure/Recovery / Local patterns

QUESTIONS ?