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F15 / E145, en-route, Bedford UK, 2005

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Summary
On 27 January 2005, two USAF-operated McDonnell Douglas F15E fighter aircraft, both continued to climb and both passed through the level of an Embraer 145 being operated by British Airways Regional on a scheduled passenger flight from Birmingham to Hannover, one seen at an estimated range of 100 feet.
Event Details
When January 2005
Actual or Potential
Event Type
AGC, AI, HF, LB, LOS
Day/Night Day
Flight Conditions IMC
Flight Details
Aircraft BOEING F-15 Strike Eagle
Operator United States Air Force
Domicile United States
Type of Flight Military/State
Origin RAF Lakenheath
Intended Destination RAF Lakenheath
Actual Destination RAF Valley/Anglesey Airport
Flight Phase Climb
ICL / ENR
Flight Details
Aircraft EMBRAER ERJ-145
Operator British Airways
Domicile United Kingdom
Type of Flight Public Transport (Passenger)
Origin Birmingham International Airport
Intended Destination Hannover
Actual Destination Hannover
Flight Phase Climb
ICL / ENR
Location
Approx. near Bedford, UK
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General
Tag(s) Aircraft-aircraft near miss
Inadequate Aircraft Operator Procedures
Inadequate ATC Procedures
Military Fast Jet Formation
Foreign Military Aircraft
AGC
Tag(s) Military Formation Clearance
Military/Civil Coordination
AI
Tag(s) CA Incursion
Aircraft not in contact with Airspace ATC
HF
Tag(s) ATC Unit Co-ordination
Ineffective Monitoring
Manual Handling
Procedural non compliance
Violation
LB
Tag(s) Accepted ATC Clearance not followed
Manual flight
LOS
Tag(s) Accepted ATC Clearance not followed
Required Separation not maintained
Level Bust
Near Miss
Military Aircraft involved
Apparent de-selection of transponder
Safety Net Mitigations
Malfunction of Relevant Safety Net No
TCAS Available but ineffective
STCA Available but ineffective
Outcome
Damage or injury No
Causal Factor Group(s)
Group(s) Aircraft Operation
Air Traffic Management
Safety Recommendation(s)
Group(s) None Made
Investigation Type
Type Independent

Description

Two USAF-operated McDonnell Douglas F15E fighter aircraft declared as operating as a formation were pulling up from low level after encountering potential delays at their intended post-exercise destination due to deteriorating weather in preparation for a diversion. Despite being cleared to FL150 only, both continued to climb and both passed through the level of an Embraer 145 being operated by British Airways Regional on a scheduled passenger flight from Birmingham to Hannover, one seen at an estimated range of 100 feet. The aircraft were on different ATC control frequencies, being Operational Air Traffic and General Air Traffic respectively.

Investigation

An Investigation into this event was carried out by the UK AAIB because it was assessed as too dangerous to be handled by the UK AIRPROX Board which routinely deals with routine losses of separation.

The Investigation found that the infringement of controlled airspace by the two USAF aircraft had followed a level bust through their cleared level of FL150 and that Mode ’C’ altitude returns from both aircraft temporarily disappeared during the 1 minute 21 seconds they were passing through the airway. Visual contact with the civil aircraft was admitted by the F15 involved on their military ATC frequency with an apology.

It was found that "despite replying to the transmission correcting their cleared level to FL150, by the time the aircraft were handed over to London Military Tahoe 52 was already passing FL160 in the climb and both aircraft continued until level at FL230, suggesting the clearance was either misunderstood or ignored."

The Investigation had “concerns about the fact that the secondary radar data disappeared as the aircraft entered controlled airspace and only re-appeared once the aircraft had cleared the airway it has been suggested that the disappearance was due to a failure of the ground radar, however because the secondary data from the F15E disappeared on more than one ground radar but other aircraft were unaffected, this does not seem to be the case.” It was noted that the absence of the secondary data….effectively disabled both the ground radar STCA and the TCAS RA protection on the Embraer 145, “representing a serious loss in conflict warning and resolution ability for all the aircraft and ATC”.

The Investigation conformed that the USAF aircraft had both climbed through their cleared flight level and then climbed though controlled airspace without transponding into conflict with the Embraer 145 which was in level flight at FL210. It found that “inadequate transmission and acknowledgement of clearances within the USAF formation plus the crews inability to fly either as a coherent formation or as two independent aircraft during their diversion were major contributory factors to the ensuing general confusion.”

It was also noted that the USAF aircraft had made “poor use… of the highly sophisticated aids available to the crews in monitoring fuel loads, monitoring ground position and using airborne radar” and that “whilst it is accepted that aircraft such as the F15E necessarily operate at times close to their minimum fuel requirements, this places an even greater emphasis on the need to make early decisions when a deteriorating weather situation makes a diversion more probable. This is especially so when the diverting aircraft are required to negotiate some of the UK’s busiest areas of civil controlled airspace.”

The full AAIB Report of the Investigation was published on 2 February 2006. No Safety Recommendations were made.

Further Reading