Airprox Report 2013085

1
AIRPROX REPORT No 2013085
Date/Time: 22 Jul 2013 1906Z
Position: 5214N 00111W
(4nm NW Daventry)
Airspace: Daventry CTA (Class: A/C)
Reporting Ac Reported Ac
Type: A320 DH8D
Operator: CAT CAT
Alt/FL: FL200 FL190
Weather: IMC KLWD VMC CLAC
Visibility: Nil 10km
Reported Separation:
400ft V/2nm H 400ft V
Recorded Separation:
400ft V/6.2nm H
1400ft V/2.3nm H
PART A: SUMMARY OF INFORMATION REPORTED TO UKAB
THE A320 PILOT reports inbound to Heathrow (LHR), under the control of London ATC Centre. Anti-
collision and navigation lights were illuminated, and SSR Modes C and S were selected. While
deviating for weather, and in level flight at FL200, ATC instructed an immediate left turn for avoiding
action. With Auto Pilot (AP) engaged, and turning left in response to the ATC instruction, he heard a
TCAS RA climb instruction. AP and Flight Director (FD) were disengaged and a climb initiated in
response to the RA. The aircraft climbed approximately 309ft and turned left 40°. From the TCAS
read-out, he estimated that the other aircraft was never closer than 400ft. He did not see the other
aircraft as he was in cloud and it was behind his aircraft. The other aircraft appeared suddenly on the
TCAS display behind his aircraft and remained there until it disappeared from the display.
He perceived the severity of the incident as ‘Medium’.
THE DH8D PILOT reports inbound to Birmingham (BHX). Position lights and white strobes were
illuminated, the landing lights were selected off. The aircraft was cleared to FL90 on descent into
BHX. There was a fair amount of CB activity at approximately 20nm SE of Honiley (HON) so the
aircraft was descended at 500fpm to stay above a build-up. Passing FL195, a right turn was
requested and approved to avoid a CB that was on the aircraft’s track. Passing FL190 a TCAS TA
was received followed closely by an RA. The AP was disengaged and the TCAS commands were
followed. Concurrent with the TCAS RA, ATC gave an instruction to turn immediately onto a heading
of 300° (he thought), which was carried out immediately. A similar instruction was heard to have been
given to another aircraft immediately prior to this. Once clear of the conflict a report was made over
the radio and clarification of any further instructions was sought.
He assessed the risk of collision as ‘Low’.
THE LTC WELIN CONTROLLER reports that there was a lot of weather avoidance being carried out
in his sector. He had co-ordinated the DH8D to enter Cowly’s airspace from HEMEL. Because the
Cowly controller had aircraft inbound to Bovingdon (BNN), he descended the DH8D to FL170 i.e.
beneath all the LHR traffic in the Cowly sector. He then issued further descent to the aircraft to FL90.Diagram based on radar dataA320
CPA 1906:42
1400ft V/2.3nm H
F203
NM
0
5
10
DH8
F202
F199
F201
F205
F189
F190
F195
F197
F198
06:30
06:18
06:06
05:54