Safety Advisory Notice SAN19980023

Safety Advisory Notice issued to: Australian regional airline operators

Recommendation details
Output No: SAN19980023
Date issued: 08 July 1998
Safety action status: Closed



Between October 1995 and July 1997 the Bureau of Air Safety Investigation undertook a study of the safety of Australian regional airlines. The objectives of this study were to:

(a) identify safety deficiencies affecting regional airline operations in Australia; and
(b) identify means of reducing the impact on safety of these deficiencies.

For the purposes of the survey, regional airlines were grouped according to the number of passenger seats fitted to the largest aircraft operated by that airline in January 1997. The groups are defined as follows:

(a) group 1: 1-9 seats;
(b) group 2: 10-19 seats; and
(c) group 3: more than 20 seats.

The study involved analysing data obtained from:

(a) responses to a survey of Australian regional airline employees;
(b) discussions with Australian regional airline employees and managers; and
(c) air safety occurrence reports involving regional airlines over a 10-year period (1986-1995) from the BASI database.

This Safety Advisory Notice addresses one of the safety deficiencies identified as a result of this study.


Some pilots are intentionally descending below published safety altitudes in conditions under which terrain clearance cannot be assured.

Survey Results

When respondents were asked to describe a safety incident, occurrences of pilots breaking instrument flight rules (IFR) constituted one of the most common types of incident described. Pilots were asked to agree or disagree with the statement that their company flies strictly by the IFR. The large majority of pilots (94.7%) agreed with this statement, while 4.1% disagreed. When the responses to this question were analysed by airline group, there was no significant difference between the answers from pilots from the three airline groups.

Pilots were also asked to describe any deviations from the IFR, and the reasons for these deviations. A numerical summary of the responses can be found in attachment 1.

Descent Below Safety Altitudes

From the survey responses, some of the deviations involving descent below a published safety altitude included:

(1) descent below the steps during a Distance Measuring Equipment (DME) or Global Positioning System (GPS) arrival while in instrument meteorological conditions (IMC);
(2) descent to circuit altitude at night outside the instrument approach circling area;
(3) descent below instrument approach minimum descent altitude (MDA) while in IMC; and
(4) diversion off-track to descend in IMC over water to an altitude lower than the destination MDA.

For the purpose of this study, "safety altitude" is a generic term meaning "lowest safe altitude", "minimum safe altitude", "minimum altitude" for a given DME/GPS distance in an arrival procedure or "minimum descent altitude" in an instrument approach.

Examples of survey responses

"When breaking clear of cloud, [there is a] tendency to adopt visual procedures with little or no forward visibility in rain. If not visual upon reaching minimum altitude, a large number of captains immediately descend further. [This is caused by] lazy, undisciplined captains and a perceived "uncoolness" in just missing an approach."
- Pilot, respondent 085

"[A common deviation from IFR is] descent below the lowest safe altitude on route sectors to aerodromes without a navigation aid in conditions that are non-VMC. [This is done] to enable the flight to get into an aerodrome where conditions are marginal but is not surrounded by terrain or obstacles."
- Pilot, respondent 178

"One or two management pilots have a willingness to push the minimums i.e. they suffer from get-in-at-all-costs. Old habits die hard. One suffers tunnel vision and talks himself into continuing, for example, "it is only a couple of hundred feet", "you've done it before", "one must be flexible" and "the rules are only a guide"."
- Pilot, respondent 568


Descent below the published safety altitude has been a factor in many accidents, including the crash of the Monarch Airlines Piper Chieftain at Young, NSW in June 1993. Any descent below the safety altitude, in conditions under which terrain clearance cannot be assured, increases the risk of a controlled-flight-into-terrain-accident, and represents a significant safety issue.

Output text

Australian regional airline operators should note the deficiency identified in this document and take appropriate action.

Initial response
Date issued:
Response from: Hazelton Air Services Pty Limited
Action status: Not Required
Response text:
Last update 01 April 2011