Visual References
Visual References
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Description
The phrase 'Required Visual Reference' is used in relation to the transition from control of an aircraft by reference to flight deck instrumentation to control by reference to external visual references alone. Those visual references, including aids, should have been in view for sufficient time for the pilot to have made an assessment of the aircraft position and rate of change of position in relation to the desired flight path. In Category III operations with a decision height the required visual reference is that specified for the particular procedure and operation. (ICAO Annex 6, and PANS-ATM).
The establishment of visual references at the completion of an instrument approach is an important process which determines whether the approach may be continued to landing, or a go-around must be flown.
Note: the vertical or slant view of the ground through broken clouds or fog patches does not constitute an adequate visual reference to conduct a visual approach or to continue an approach below the applicable MDA/H or DA/H.
The section below headed "European Regulations" details what these visual references must be. The remainder of this article deals with the process of transition within the aircraft cockpit.
According to Flight Safety Foundation (FSF) Approach-and-landing Accident Reduction (ALAR) Briefing Note 7.3 — Visual References , "The transition from instrument references to external visual references is an important element of any type of instrument approach."
The briefing note points out that two common Task task-sharing philosophies are common:
- "Pilot flying-pilot not flying (PF-PNF) task-sharing with differences about the acquisition of visual references, depending on the type of approach and on the use of automation:
- Nonprecision and Category (CAT) I instrument landing system (ILS) approaches; or,
- CAT II/CAT III ILS approaches (the captain usually is the PF, and only an automatic approach and landing is considered); and,
- "Captain-first officer (CAPT-FO) task-sharing, which usually is referred to as a shared approach, monitored approach or delegated-handling approach.
"Differences in the philosophies include:
- The transition to flying by visual references; and,
- Using and monitoring the autopilot."
"The task-sharing for the acquisition of visual references and for the monitoring of the flight path and aircraft systems varies, depending on:
- The type of approach; and,
- The level of automation being used:
- Hand-flying (using the Flight Director [FD]); or,
- Autopilot (AP) monitoring (single or dual AP)."
The briefing note than proceeds to discuss task sharing and other considerations for different types of approach.
European Regulations
AMC1 to IR-OPS CAT.OP.MPA.305(e) and Appendix 1 to EU-OPS 1.430 define the required visual references for continuion of a precision approach or a non-precision approach as follows:
Non-Precision Approach A pilot may not continue an approach below MDA/H unless at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:
(i) Elements of the approach light system;
(ii) The threshold;
(iii) The threshold markings;
(iv) The threshold lights;
(v) The threshold identification lights;
(vi) The visual glide slope indicator;
(vii) The touchdown zone or touchdown zone markings;
(viii) The touchdown zone lights;
(ix) Runway edge lights; or
(x) Other visual references accepted by the Authority.
Precision Approach A pilot may not continue an approach below the Category I decision height ... unless at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:
(i) Elements of the approach light system;
(ii) The threshold;
(iii) The threshold markings;
(iv) The threshold lights;
(v) The threshold identification lights;
(vi) The visual glide slope indicator;
(vii) The touchdown zone or touchdown zone markings;
(viii) The touchdown zone lights; or
(ix) Runway edge lights.
Category II Operations A pilot may not continue an approach below the Category II decision height ... unless visual reference containing a segment of at least 3 consecutive lights being the centre line of the approach lights, or touchdown zone lights, or runway centre line lights, or runway edge lights, or a combination of these is attained and can be maintained. This visual reference must include a lateral element of the ground pattern, i.e. an approach lighting crossbar or the landing threshold or a barette of the touchdown zone lighting.
Category IIIA Operations For Category IIIA operations, and for Category IIIB operations with failpassive flight control systems, a pilot may not continue an approach below the decision height ... unless a visual reference containing a segment of at least 3 consecutive lights being the centreline of the approach lights, or touchdown zone lights, or runway centreline lights, or runway edge lights, or a combination of these is attained and can be maintained.
Category IIIB Operations For Category IIIB operations with fail-operational flight control systems using a decision height a pilot may not continue an approach below the Decision Height ... unless a visual reference containing at least one centreline light is attained and can be maintained.
Accidents and Incidents
The following events on SKYbrary involve lack of visual reference as a factor:
On 10 June 2024, a Dornier 228 impacted terrain near its destination in Malawi when it entered instrument meteorological conditions (IMC) when already operating in marginal visual flying conditions in daylight. The aircraft was destroyed and the three crew and six passengers on board were killed. The accident was attributed to the decision to continue flight at a low height over terrain, a lack of pilot situational awareness and inadequate pre-flight preparation. The passengers on the flight were civilians but the aircraft was owned by the Malawi Government and was operated by the Malawi Air Force.
On 31 October 2019, an Airbus Helicopters EC225LP departing a helipad at Dokdo, South Korea, at night crashed into the sea after the pilot became spatially disoriented and did not respond to alerts from both the travelling engineer and the copilot to the unintended descending flight path. All seven occupants were killed and the helicopter was destroyed. The absence of a departure briefing was assessed as contributory. However, findings on the underlying context for the accident involved procedural and training issues regarding the operational regime for emergency medical flights.
On 6 November 2022 adverse weather delayed an ATR42 beginning its visual-only approach to Bukoba. When an approach was commenced, adequate visual reference was not maintained due to continued adverse weather. No corrective action was taken in response to three successive automated excessive descent rate alerts or the first officer’s calls to reduce descent rate. Although response did follow a ‘PULL UP’ warning, it was too late to prevent a high-energy impact with the surface of Lake Victoria close to the shoreline, and both pilots and 17 of the passengers were killed.
On 12 August 2024, an ATR 72-500 making a Category 1 ILS approach to Guernsey with thick fog breached an approach ban by continuing its descent below the applicable minimum altitude of 1,000 feet agl. The aircraft then continued below what would have been the applicable 200 feet agl Decision Altitude without visual reference. At around 70 feet agl, a go-around was called but not correctly commenced, and the aircraft passed close to an unseen mast north of the runway before it eventually climbed. In the absence of any visibility improvement, a diversion to Southampton then followed.
On 11 February 2022 an Airbus A320 making a visual approach to Guadeloupe at night was advised by ATC of a descent below the minimum safe altitude. This advisory came as the crew continued the approach after visual reference was temporarily lost. A repeat of this warning by ATC prompted crew recognition that the aircraft was low and off the required approach track. A go-around was initiated from 460 feet agl. The decision to attempt a visual approach in unsuitable circumstances and a delay in recognising the need for a go-around were found to have been symptomatic of poor tactical decision-making.
Further Reading
- ICAO Doc 4444: PANS-ATM;
- IR-OPS CAT.OP.MPA.305
- AMC & GM CAT.OP.MPA.305
- EU-OPS 1.430;
- EASA SIB 2025-05 Development and Usage of Procedures for Visual Manoeuvring with Prescribed Tracks Relying on RNP
Flight Safety Foundation
The Flight Safety Foundation ALAR Toolkit provides useful training information and guides to best practice. Copies of the FSF ALAR Toolkit may be ordered from the Flight Safety Foundation ALAR website
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