Airprox Incident Boeing 737-204 Adv. EI-CJE, Tuesday 30 September 1997

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Date:	Tuesday 30 September 1997
Time:	13:53
Type:	Boeing 737-204 Adv.
Owner/operator:	Ryanair
Registration:	EI-CJE
MSN:	22639/863
Year of manufacture:	1982
Fatalities:	Fatalities: 0 / Occupants: 110
Other fatalities:	0
Aircraft damage:	None
Location:	9 NM Southwest of London-Stansted Airport (STN/EGSS) - United Kingdom
Phase:	Initial climb
Nature:	Passenger - Scheduled
Departure airport:	London-Stansted Airport (STN/EGSS)
Destination airport:	Dublin Airport (DUB/EIDW)
Investigating agency:	AAIB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
A loss of separation occurred between a Ryanair Boeing 737-200 (EI-CJE),departing from London
(Stansted), and an Air UK BAe 146 (G-UKJF), inbound to London-City Airport.
The two aircraft passed at the closest proximity of 0.91 nm horizontally and 200 feet vertically,

The B737 was planned to operate a scheduled passenger service from London (Stansted) to Dublin.
As part of the pre-flight procedure the crew had obtained the latest ATIS information which included a surface wind of 250°/06 kt, a visibility of 6,000 meters, the surface temperature was 19°C, the QNH 1023 mb and the cloud was reported as 'few' at 900 feet, broken at 2,600 feet; Runway 23 was the runway in use. At 1312 hrs the crew contacted the Stansted ground control frequency to acknowledge receipt of the relevant ATIS and requested ATC clearance. A BUZAD FOUR ROMEO Standard Instrument Departure (SID) was allocated, as expected, and a transponder setting was also given.

The BUZAD FOUR ROMEO SID (see Jeppesen Guide extract, part 1 and part 2) requires that, after take off, the aircraft should climb straight ahead and, at 11·5 DME from Brookmans Park (BPK), which is coincident with the 160° radial from Barkway (BKY), the aircraft should turn right to intercept the BKY 175°radial inbound to BKY by 8 DME from BKY. The aircraft is then required to proceed inbound towards BKY. Separate routing instructions then apply for the remainder of the SID. The initial altitude constraint for this SID is to cross the 5 DME point from BKY at 3,000 feet.

The commander was to be the handling pilot for this leg. He therefore set the navigation aids as follows: BKY VOR on navigation box 1, BPK VOR on navigation box 2, 355° was set on both omni-bearing selectors (OBSs) and both remote magnetic indicators (RMIs) were set to dual VOR. These navigation aids were then checked by both pilots for the correct aural identification.

The crew requested clearance to push back and start engines at 1337 hrs after which clearance was given to taxi to the holding point for Runway 23. Whilst taxiing the flight was transferred to the frequency for the aerodrome control tower who cleared it for take off at 1349 hrs. During this period there were no amendments to the original departure clearance.

Meanwhile control of the BAe 146, on a scheduled passenger service from Edinburgh to London City Airport, had been passed to the North East sector of the London Terminal Control Area (LTCA) at 1350 hrs at which time the aircraft was descending to FL70 on a radar heading of 120°M; this heading would take it about 4 nm to the north east of BPK. This same controller was also responsible for the Stansted departures at that time.

The B737 took off from Stansted at 1350:35 hrs and climbed straight ahead as the BAe 146, descending through FL 90, was 21 nm to the west maintaining the radar heading of 120°M. Stansted handed the B737 over to the departure controller at 1350:55 hrs as the aircraft was passing through 1,500 feet, however, due to the amount of radio traffic on the new frequency, contact was not established until one minute later by which time the flaps were raised and the aircraft had leveled at 3,000 feet. From the recorded flight data it was determined that at this time the aircraft was already one nautical mile past the start point for the right turn towards BKY required by the SID. The BAe 146 had by now been cleared to descend to 4,000 feet.

When the crew of the B737 called level at 3,000 feet it was instructed to 'Squawk Ident', climb to
FL 70 and the speed restriction of 250 KIAS below FL 100 was removed. Ident was selected
(causing the aircraft transponder to transmit its code to the ground radar),and the aircraft
recommenced the climb. However, the aircraft maintained the runway heading until 13:52:43 hrs,
when at an altitude of 4300 feet and 6·8 nm from BPK, the aircraft commenced a right turn. Just as
this aircraft entered the turn the ATC controller instructed the flight to 'TURN RIGHT
IMMEDIATELY HEADING 360°'. The BAe 146 was then instructed to 'TURN RIGHT IMMEDIATELY
HEADING 180° STOP YOUR DESCENT ALTITUDE 5500 FEET'. The B737 was then told 'AVOIDING
ACTION DESCEND IMMEDIATELY ALTITUDE 4,000 FEET TRAFFIC OPPOSITE DIRECTION SAME LEVEL'.

The commander of the B737 then reported being visual with the BAe 146 and the two aircraft passed at the closest proximity of 0.91 nm horizontally and 200 feet vertically, calculated from the Stansted radar head. At the point of minimum separation, 5.4 nm northeast of the BPK VOR, the BAe 146 was at 5,400 feet and climbing slightly to achieve 5,500 feet whilst the B737 was at 5,200 feet and about to descend. Both aircraft were then in a right turn.

The B737 leveled at 4,300 feet QNH (FL 40) before requesting clearance to climb to FL 70. Both aircraft were subsequently given radar vectors before they left the frequency.

This reconstruction was compiled using a combination of recorded radar data, recordings of the radio transmissions and information from the Flight Data Recorder (FDR) from the B737. The FDR had been removed from the aircraft upon the completion of the twelfth sector following the incident. The Cockpit Voice Recorder had been operational throughout that time but, having only a 30 minute loop facility, it had recorded audio data subsequent to the period of the incident. Supporting evidence for the event was provided by recordings from the Stansted Airport Noise Unit and data from the Separation Monitoring Function at LATCC.

The navigation equipment on the B737 was serviceable for this flight. There is no evidence of any unserviceability of the ground navigation aids and all other aircraft allocated this SID in the same period followed it correctly.

Accident investigation: