SAFE WINGS. This issue LEVEL BUST AN INCIDENT INVOLVING LEVEL BUST. * For Internal Circulation Only

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1 SAFE WINGS Issue 40, SEPTEMBER 2015 This issue ü ü LEVEL BUST AN INCIDENT INVOLVING LEVEL BUST * For Internal Circulation Only

2 SAFE WINGS September Edition 40 EDITORIAL In today s busy and congested airspace, precise flying is essential to ensure safety and avoid unsafe situations. Despite aircraft being equipped with modern technology and precision flying instruments, the aviation industry frequently encounters altitude deviations or level bust incidents. In this edition of the magazine we have featured an article on LEVEL BUST along with a related incident. ACKNOWLEDGEMENTS The posting of stories, reports and documents in this magazine does not in any way, imply or necessarily express or suggest that all the information is correct. It is based on details gathered from various sources and is for information purpose only. The Flight Safety Department is making this material available in its efforts to advance the understanding of safety. It is in no way responsible for any errors, omissions or deletions in the reports. 1 P age

This may take one of three different forms: An aircraft in level flight climbs or descends without clearance An aircraft climbing or descending fails to level off accurately at the correct level

3 September Edition 40 SAFE WINGS LEVEL BUST A LEVEL BUST occurs when an aircraft fails to fly at the level for which it has been cleared. A level burst can be defined as any unauthorised vertical deviation of more than 300 feet from an ATC flight clearance. Within RVSM airspace this limit is reduced to 200 feet. This may take one of three different forms: An aircraft in level flight climbs or descends without clearance An aircraft climbing or descending fails to level off accurately at the correct level (either passing through and continuing the climb or descent, or passing through and then returning to the correct level) An aircraft levelling off at the correct level or altitude, but with an incorrect altimeter setting Types of Level Bust The following types exclude involuntary transient departure from acquired levels attributable to the effects of turbulence: Aircraft both accepts a clearance and sets/records it correctly but then does not follow it [flight management error (usual) or technical fault (rarely)] Aircraft accepts a clearance correctly but then sets it incorrectly without the error being picked up by the crew [flight management error] Aircraft reads back clearance incorrectly and this error is not picked up by ATC so it is then recorded/set and followed [ATC error] Aircraft is unable to react fast enough to a late reclearance and passes through new cleared level [ATC error]. 2 P age

4 SAFE WINGS September Edition 40 Aircraft follows clearance with the wrong altimeter sub scale setting Aircraft departs cleared flight level without clearance to do so. CAUSAL FACTORS Mis-hear An ATCO (Air Traffic Control Officer) failed to detect an incorrect readback. Mis hear errors are recorded when an ATCO fails to detect and correct an incorrect pilot R/T read back which is audible. These errors are more common at ATC centres with high R/T workload. Correct pilot readback followed by incorrect action The pilot readback the controllers instruction correctly however performed an incorrect action (e.g., climbed to incorrect FL). Some events in this category will involve occasions where crews have received a clearance to a level which is known to cause confusion such as FL100/FL110 or FL200/220. In 2004 there were 8 recorded occasions where a crew have correctly acknowledged a descent clearance to FL110 but have then descended to FL100. Other events will involve a breakdown in cockpit SOPs; It is not fully understand why this type of event occurs but it is possible that high R/T loading, high cockpit workload and communication issues are all contributory factors. Incorrect pilot readback by correct aircraft The pilot's readback of the controller instruction was erroneous (e.g., wrong level) Pilot readback by incorrect aircraft A pilot read back an instruction that had been issued to another aircraft. 3 P age

Gatwick, Stansted and Luton all have step climb SIDs and these errors normally involve an aircraft failing to stop at the first stop altitude.

5 September Edition 40 SAFE WINGS Failed to follow cleared SID The pilot failed to follow comply with the level restrictions include in a SID. Failed to follow cleared SID is a particular issue with departures from Gatwick, Stansted, and Luton although other airports are affected. Gatwick, Stansted and Luton all have step climb SIDs and these errors normally involve an aircraft failing to stop at the first stop altitude. Altimeter setting error The crew did not have the correct pressure set. Altimeter setting error is a problem mainly reported in the London TMA, 80% of the errors occur when the aircraft is in the climb, is above the transition altitude/level and the standard pressure setting isn't set. Poor manual handling The pilot's manual flying of the aircraft led to aircraft failing to comply with clearance. Aircraft technical problem Technical problems exist with the aircraft Failure to follow ATC instruction The pilot did not comply with an ATC instruction (e.g., the aircraft failed to hold when instructed). Recommendations for improvement The following recommendations improve communications and situational awareness: (a) Be aware that readback/hearback errors involve both the pilot and the controller; - The pilot may be interrupted or distracted when listening to a clearance, be subject to forgetfulness or be subject to the bias of expectation when listening to or reading back the instruction (this bias is also termed wishhearing) or may be confused by similar callsigns; and, - The controller may confuse similar callsigns, be distracted by other radio communications or by telephone communications, or be affected by blocked transmissions or by workload. (b) Use standard phraseology for clear and unambiguous pilot-controller communications and crew communication: - Standard phraseology is a common language for pilots and controllers, and this common language increases the likelihood of detecting and correcting errors. 4 P age

6 SAFE WINGS September Edition 40 (c) Use expanded phraseology such as: - Announcing when leaving a flight level or altitude (e.g. leaving [ ] for [ ], or, leaving [ ] and climbing/descending to [ ] ), thus increasing the controller s situational awareness; - Combining different expressions of specific altitudes (e.g. one one thousand feet that is eleven thousand feet ); and, - Preceding each number by the corresponding flight parameter (flight level, heading, airspeed [e.g. descend to flight level two four zero instead of descend to two four zero ]). (d) When in doubt about a clearance, request confirmation from the controller; do not guess about the clearance based on crew discussion. Task Prioritisation And Task Sharing The following recommendations should enable optimum prioritisation of tasks and task sharing: (a) Stop nonessential tasks during critical phases of flight. - A Sterile Cockpit rule has been established which defines critical stages of flight and what activities are permitted during them. Many European operators enforce similar procedures by their crews. - Some operators consider the final 1,000 feet before reaching the cleared altitude or flight level as a critical stage of flight; (b) Monitor/supervise the operation of autopilot/fms to confirm correct level-off at the cleared altitude and for correct compliance with altitude or time restrictions; (c) Plan tasks that preclude listening to ATC communications (e.g. ATIS, company calls, public-address announcements) for periods of infrequent ATC communication; and, (d) When one pilot does not monitor the ATC frequency while doing other duties (e.g. company calls) or when leaving the flight deck, the other pilot should: - Acknowledge that he/she has responsibility for ATC radio communication and aircraft control, as applicable; - Check that the radio volume is adequate to hear an ATC call; - Give increased attention to listening/ confirming/reading back (because of the absence of cross-checking); and, - Brief the other pilot when he/she returns, highlighting any relevant new information and any change in ATC clearance or instructions. Altitude-Setting Procedures The following techniques enhance standard operating procedures (SOPs): 5 P age

7 September Edition 40 SAFE WINGS (a) When receiving a level clearance, immediately set the cleared altitude in the selected altitude window; (b) Ensure that the selected level is crosschecked by both pilots (e.g. each pilot should announce what he/she heard and then point to the selected altitude window to confirm that the correct value has been set); (c) Ensure that the cleared level is above the minimum safe altitude (MSA); and, (d) Positively confirm the level clearance when receiving radar vectors. CALLOUTS Use the following calls to increase PF/PNF situational awareness and to ensure effective backup and challenge, (and to detect a previous error in the cleared altitude or flight level): (a) Mode changes on the flight mode annunciator (FMA) and changes of targets (e.g. airspeed, heading, altitude) on the primary flight display (PFD) and navigation display (ND); (b) Leaving [...] for [ ] and, (c) One to go, One thousand to go, or [ ] for [ ] when within 1000 feet of the cleared altitude or flight level. When within 1000 feet of the cleared altitude or flight level or an altitude restriction in visual meteorological conditions (VMC), one pilot should concentrate on scanning instruments (one head down) and one pilot should concentrate on traffic watch (one head up). FLIGHT LEVEL OR ALTITUDE CONFUSION Confusion between FL 100 and FL 110 (or between 10,000 feet and 11,000 feet) is usually the result of the combination of two or more of the following factors: (a) Readback/hearback error because of similar sounding phrases; (b) Phraseology used, e.g.: - ICAO standard phraseology is flight level one zero zero and flight level one one zero ; - The non-standard phraseology: flight level one hundred is used by a number of European air navigation service providers (ANSPs); (c) Mindset tending to focus only on one zero and thus to understand more easily flight level one zero zero ; (d) Failing to question the unusual (e.g. bias of expectation on a familiar standard terminal arrival [STAR]); and/or, (e) Subconsciously interpreting a request to slow down to 250 kt as a clearance to descend to FL 100 (or 10,000 feet). TRANSITION ALTITUDE/LEVEL The transition altitude is the altitude at or below which the vertical position of an aircraft is controlled by reference to altitude. The transition level is a variable level above the transition altitude, above which the vertical position of the aircraft is determined by reference to flight level. The transition level varies according to the local atmospheric pressure and temperature. 6 P age

8 SAFE WINGS September Edition 40 The transition altitude may be either: (a) Fixed for the whole country (e.g. 18,000 feet in the United States);or, (b) Fixed for a given airport (as indicated on the approach chart); Depending on the airline s or flight crew s usual area of operation, changing from fixed transition altitude to variable transition level may result in a premature resetting or a late resetting of the altimeter. An altitude restriction (expressed in altitude or flight level) may also advance or delay the change of the standard altimeter setting ( hpa or in. Hg) possibly resulting in crew confusion. In countries operating with QFE, the readback should indicate the altimeter reference (i.e. QFE). HIGH RATES OF CLIMB AND DESCENT High rates of climb and descent increase the likelihood of a level bust and reduce the opportunity for correcting error before a dangerous situation arises. High rates of climb or descent may also trigger ACAS nuisance warnings. In any airspace ATC may impose minimum and maximum rates of climb and descent; this is particularly true within RVSM airspace during the last 1,000 feet of climb or descent to cleared flight level. Whether or not a restriction applies, it is good practice to reduce the rate of climb or descent to below 1,500 feet/min when within 1,000 feet of the cleared flight level. LEVEL BUSTS IN HOLDING PATTERNS Controllers assume that pilots will adhere to a clearance that the pilot has read back correctly. Two separate holding patterns may be under the control of the same controller on the same frequency. With aircraft in holding patterns, controllers place particular reliance on pilots because the overlay of aircraft data labels on the controller s radar display may not allow the immediate detection of an impending traffic conflict. Accurate pilot-controller communication is essential when descending in a holding pattern because of the reduced effectiveness of the usual safety-net of short term conflict alert (STCA) and (ACAS): (a) STCA may in some cases be disabled; (b) SSR transponders may be required to be switched off; and, (c) ACAS may be required to be switched to TA only. The following pilot actions are important when in a holding pattern: (a) Do not take a communication intended for another aircraft (by confusion of similar callsigns); and, (b) Prevent or minimise the risk of blocked transmission, (e.g. simultaneous readback by two aircraft with similar callsigns, or simultaneous transmissions by the pilot and the controller); 7 P age

September Edition 40 SAFE WINGS SUMMARY Level busts can be prevented by adhering to SOPs to: (a) Set the altimeter reference; and, (b) Select the cleared altitude or flight level.

Blame-free reporting of level bust events should be encouraged to broaden knowledge of the causal factors of level busts.

9 September Edition 40 SAFE WINGS SUMMARY Level busts can be prevented by adhering to SOPs to: (a) Set the altimeter reference; and, (b) Select the cleared altitude or flight level. To be effective, an altitude awareness programme should be emphasised during transition training, recurrent training and line checks. Blame-free reporting of level bust events should be encouraged to broaden knowledge of the causal factors of level busts. The following should be promoted: (a) Adhere to the pilot-controller confirmation/ correction process (communication loop); (b) Practice flight crew cross-checking to ensure that the selected altitude is the cleared altitude; (c) Cross-check that the cleared altitude is above the MSA; (d) Monitor instruments and automation when reaching the cleared altitude or flight level; and, (e) In VMC, apply the technique one head down and one head up when reaching the cleared altitude or flight level. 8 P age

SAFE WINGS September Edition 40 LEVEL BUST INCIDENT INVOLVING PIA - A310 & SAS - B736 Given below is an account of a Level Bust Incident involving two aircrafts A310 / B736 adopted from AIBN Report

separation with an SAS BOEING 737-600 inbound to Oslo from Alesund in which response to a co-ordinated TCAS RA by the A310 was not in accordance with its likely activation (descend).

10 SAFE WINGS September Edition 40 LEVEL BUST INCIDENT INVOLVING PIA - A310 & SAS - B736 Given below is an account of a Level Bust Incident involving two aircrafts A310 / B736 adopted from AIBN Report DESCRIPTION On 21 February 2001, a level bust 10 nm north of Oslo Airport in day VMC by a climbing PIA AIRBUS A-310 operating a scheduled passenger flight from Oslo to Copenhagen led to loss of separation with an SAS BOEING inbound to Oslo from Alesund in which response to a co-ordinated TCAS RA by the A310 was not in accordance with its likely activation (descend). The B736 received and correctly actioned a Climb RA. SUMMARY The incident occurred 10 NM north of ENGM, and led to a violation of separation minimums between an Airbus A-310 from Pakistan International Airlines (PIA 752) and a Boeing from Scandinavian Airlines System (SAS 2367). SAS 2367 inbound to ENGM from Ålesund airport Vigra (ENAL), called Oslo ATCC Approach (APP) sector East at time 14:04:40 UTC, established on Standard Arrival Route (STAR) MES 2A arrival. The crew was cleared down to FL 100. PIA 752, flying from ENGM to Copenhagen airport Kastrup (EKCH), called APP sector East at 14:07:37 UTC climbing to 7000 ft on Standard Instrument Departure (SID) GOTUR 2A. PIA 752 was radar identified, and the crew was cleared climb to FL 090, and instructed to level off at FL 090 due to crossing traffic above (SAS 2367). The crew correctly read back the clearance to FL 090. At time 1509, both crew reported TCAS-alarm. At that time SAS 2367 was level at FL 100, and PIA 752 was approaching FL 090. The crew of PIA 752 did not stop their climb at FL 090, and as SAS 2367 passed just overhead the vertical distance had been reduced to 800 ft. The SAS 2367 crew had climbed to FL 102, according to TCAS Resolution Advisory (RA), and according to radar transcript, PIA 752 passed FL 094 and was still climbing. PIA 752 continued climb to FL 097, before staring descend back to FL 090. The horizontal distance though, had been increasing from the moment the vertical distance between the two aircraft was 800 ft. 9 P age

September Edition 40 SAFE WINGS COMMENTS FROM THE ACCIDENT INVESTIGATION BOARD It is the AAIB/Ns opinion that there was a risk of collision involved during this incident.

In this incident the crew of PIA 752 did not adhere to their clearance limit of FL 090, thus leading to a violation of separation minimums.

11 September Edition 40 SAFE WINGS COMMENTS FROM THE ACCIDENT INVESTIGATION BOARD It is the AAIB/Ns opinion that there was a risk of collision involved during this incident. The ATC planning was according to radar separation rules, but any traffic planning is depending on the involved aircrews acting according the instructions and clearances that has been issued. In this incident the crew of PIA 752 did not adhere to their clearance limit of FL 090, thus leading to a violation of separation minimums. Both crews reported TCAS warnings, and the SAS 2367 crew acted according to TCAS RA-climb. The PIA 752 crew also reported receiving RA-climb, but this seems inconsistent with how the ACAS system works, as the different TCAS installations are supposed to be communicating in order not to create additional conflicts. According to radar transcripts, PIA 752 was observed in a steady climb to FL 094, and then a short halt followed by further climb to FL 097. As mentioned earlier there are different cause for level busts, some of them are as follows: Complexity of SIDs Density of traffic (causing lack of hearback by the controllers) Long/complex clearances Expect level clearances Callsign confusion FMS (Flight Management System) equipment modes Simultaneous transmissions Final Conclusion/Comments: It is of utmost importance that the airlines focus on this issue in their training programs. CRM (Crew Resource Management), Situational Awareness, procedures for altimeter setting and the use of correct FMS modes are all important issues in the work for reducing the amount of level busts. Another important aspect is that SIDs and STARs should be constructed in a way that minimizes the consequences if a level bust occurs. 10 P age

12 We give utmost importance to your valuable comments and feedback. Please do mail us at or PROMISING A SAFER SKY, AIR INDIA, AIR INDIA EXPRESS & ALLIANCE AIR Editorial: - Bhavish B S, Indu P G Designed by Bhavish BS

Level Bust. European Action Plan for the Prevention of Level Bust. Edition 1.0 July EATM European Air Traffic Management

Level Bust. European Action Plan for the Prevention of Level Bust. Edition 1.0 July EATM European Air Traffic Management Level Bust European Action Plan for the Prevention of Level Bust Edition 1.0 July 2004 EATM European Air Traffic Management Table of Contents 1. Statement of Commitment 2. Introduction and Background 3.