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Altimeter Setting Procedures

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Article Information
Category: Level Bust Level Bust
Content source: SKYbrary About SKYbrary
Content control: EUROCONTROL EUROCONTROL

Contents

Description

The aircraft altimeter barometric sub-scale must be set to the appropriate setting for the phase of flight. These are:

  • Flight level. Standard pressure setting (1013 hPa) is set when flying by reference to flight levels above the transition altitude;
  • Altitude. Regional or airfield pressure setting (QNH) is set when flying by reference to altitude above mean sea level below the transition level;
  • Height. Altimeter pressure setting indicating height above airfield or touchdown (QFE) is set when approaching to land at airfield where this procedure is in use.
altimeter setting
Altimeter Setting

Failure to set the appropriate barometric sub-scale pressure setting may result in a significant deviation from the cleared altitude or Flight Level

Types of Altimeter Setting Error

  • The pilot mishears the transmitted pressure setting and sets an incorrect figure.
  • The pilot hears the transmitted pressure setting correctly but fails to set it or mis-sets it.
  • The pilot fails to change the pressure setting at the appropriate point in a departure, climb, descent or approach.

Effects

Defences

Effective SOPs contained in company flight operations manuals which specify appropriate procedures for the setting and cross-checking of altimeter barometric sub scales.

Typical Scenarios

  • A pilot fails to ensure that standard pressure is set when passing the transition altitude in the climb, and levels the aircraft at a flight level which differs from the cleared level by an amount depending on the difference between the QNH and 1013 hPa.
  • A pilot fails to set QNH when passing the transition level in the descent and levels the aircraft at an altitude which differs from the cleared altitude by an amount depending on the difference between QNH and 1013 hPa.
  • A pilot un-used to landing with QFE set, does not remember that the altimeter now indicates height above airfield elevation or touch-down and consequently that the aircraft is likely to be closer, and possibly a lot closer, to the ground than with QNH set.

Solutions

  • The existence of appropriate SOPs for the setting and cross-checking of altimeter sub scales and their strict observance is the only universal primary solution to eliminate incorrect altimeter setting.
  • Use of the aircraft radio altimeter to monitor the aircraft proximity with the ground can help to improve situational awareness provided that the flight crew are generally familiar with the terrain over which they are flying;
  • GPWS/TAWS provide a safety net against CFIT and in the case of TAWS Class 'A' with its option of a simple terrain mapping display, it can also be used to directly improve routine situational awareness.

Related Articles

Accidents and Incidents

Events in which the incorrect altimeter pressure setting was either a cause or contributing factor in a Level Bust or CFIT/near CFIT:

  • A320, vicinity Oslo Norway, 2008 (CFIT LB HF AGC) (On 19 December 2008, an Aeroflot Airbus A320 descended significantly below its cleared and acknowledged altitude after the crew lost situational awareness at night whilst attempting to establish on the ILS at Oslo from an extreme intercept track after a late runway change and an unchallenged incorrect readback. The Investigation concluded that the response to the EGPWS warning which resulted had been “late and slow” but that the risk of CFIT was “present but not imminent”. The context for the event was considered to have been poor communications between ATC and the aircraft in respect of changes of landing runway.)
  • DH8D, Vicinity Exeter UK, 2010 (CFIT LB AW HF) (On 11 September 2010, a DHC8-400 being operated by Flybe on a scheduled passenger flight from Bergerac France to Exeter failed to level as cleared during the approach at destination in day VMC and continued a premature descent without the awareness of either pilot due to distraction following a minor system malfunction until an EGPWS ‘PULL UP’ Hard Warning occurred following which a recovery climb was initiated. There were no abrupt manoeuvres and no injuries to any of the 53 occupants.)
  • GLF5 / A319, south-eastern France, 2004 (LB LOS HF) (On 16 September 2004, a loss of separation occurred over Geneva between Air France A319 and a Gulfstream 5 which commenced descent without clearance by ATC and with coordinated TCAS RAs not followed by either aircraft.)
  • B733, vicinity Helsinki Finland, 2008 (LB CFIT HF) (On 26 March 2008, a Ukraine International Airlines’ Boeing 737-300 being vectored by ATC to the ILS at destination Helsinki in IMC descended below its cleared altitude and came close to a telecommunications mast. ATC noticed the deviation and instructed a climb. The investigation attributed the non-compliance with the accepted descent clearance to the failure of the flight crew to operate in accordance with SOPs. The ability of ATC safety systems as installed and configured at the time of the occurrence was also noted.)
  • A310 / B736, en-route, Southern Norway, 2001 (LB LOS HF) (On 21 February 2001, a level bust 10 nm north of Oslo Airport by a climbing PIA A310 led to loss of separation with an SAS B736 in which response to a TCAS RA by the A310 not being in accordance with its likely activation (descend). The B736 received and correctly actioned a Climb RA.)
  • … further results

warning.png"Pressure altimeter setting error" is not in the list of possible values (Accepted ATC Clearance not followed, SID bust, Clearance readback error undetected, TCAS RA response, Manual flight) for this property.

  • B734, Amsterdam Netherlands, 2010 (BS CFIT LOC HF) (On 6 June 2010, a Boeing 737-400 being operated by Atlas Blue, a wholly owned subsidiary of Royal Air Maroc, on a passenger flight from Amsterdam to Nador, Morocco encountered a flock of geese just after becoming airborne from runway 18L in day VMC close to sunset and lost most of the thrust on the left engine following bird ingestion. A MAYDAY was declared and a minimal single engine climb out was followed by very low level visual manoeuvring not consistently in accordance with ATC radar headings before the aircraft landed back on runway 18R just over 9 minutes later.)
  • E145, en route, north east of Madrid Spain, 2011 (CFIT LB HF AGC) (On 4 August 2011, a Luxair Embraer 145 flying a STAR into Madrid incorrectly read back a descent clearance to altitude 10,000 feet as being to 5,000 feet and the error was not detected by the controller. The aircraft was transferred to the next sector where the controller failed to notice that the incorrect clearance had been repeated. Shortly afterwards, the aircraft received a Hard EGPWS ‘Pull Up’ Warning and responded to it with no injury to the 47 occupants during the manoeuvre. The Investigation noted that an MSAW system was installed in the ACC concerned but was not active.)
  • D328, Sumburgh UK, 2006 (CFIT HF) (On 11 June 2006, a Dornier 328 operated by City Star Airlines whilst positioning in marginal visibility for a day approach at Sumburgh, Shetland Isles UK, and having incorrectly responded to TAWS Class A warnings/alerts by not gaining safe altitude, came to close proximity with terrain . The approach was continued and a safe landing was made at the airport.)
  • A320, vicinity Bahrain Airport, Kingdom of Bahrain, 2000 (CFIT HF) (On 23 August 2000, a Gulf Air Airbus A320 flew at speed into the sea during an intended dark night go around at Bahrain and all 143 occupants were killed. It was subsequently concluded that, although a number of factors created the scenario in which the accident could occur, the most plausible explanation for both the descent and the failure to recover from it was the focus on the airspeed indication at the expense of the ADI and the effect of somatogravic illusion on the recently promoted Captain which went unchallenged by his low-experience First Officer.)
  • A306, East Midlands UK, 2011 (LOC AW HF) (On 10 January 2011, an Air Atlanta Icelandic Airbus A300-600 on a scheduled cargo flight made a bounced touchdown at East Midlands and then attempted a go around involving retraction of the thrust reversers after selection out and before they had fully deployed. This prevented one engine from spooling up and, after a tail strike during rotation, the single engine go around was conducted with considerable difficulty at a climb rate only acceptable because of a lack of terrain challenges along the climb out track.)
  • … further results

warning.png"Pressure altimeter setting error" is not in the list of possible values (Into water, Into terrain, Into obstruction, No Visual Reference, Lateral Navigation Error, Vertical navigation error, VFR flight plan, IFR flight plan) for this property.

Further Reading

ICAO

  • Doc 8168 (PANS-OPS), Volume I, Flight Procedures - Part VI - Altimeter Setting Procedures - Chapter 3.
  • ICAO Video: Altimetry - Basic Principles;

Flight Safety Foundation ALAR Toolkit

EUROCONTROL Level Bust Toolkit

Airbus Briefing Notes

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