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Recommendation issued to: Sportavia Soaring Centre

Recommendation details
Output No: R19970092
Date issued: 13 August 1997
Safety action status:
Background:

SUBJECT

Unsafe circuit procedures at airfields with considerable glider activity.

OCCURRENCE SUMMARY

Immediately after release from a tug aircraft, a two-seat glider commenced circling in the circuit area at Tocumwal at about 2,000 ft above ground level . At the same time, a high performance single-seat glider approached the circuit at high speed from the north-west, pulled up and collided with the circling glider. Both aircraft were severely damaged by the collision and subsequent ground impact, and all three occupants were fatally injured.

SAFETY DEFICIENCY

There were no procedures in place for the use of radio in the circuit area although both aircraft were equipped with VHF radios tuned to the Common Traffic Advisory Frequency (CTAF).

There were no procedures in place to prevent gliders entering the circuit area at high speed in an area where other gliders were manoeuvring at slow speed.

Neither glider involved in this accident were painted with high-visibility markings even though gliders can be particularly difficult to see in the air.

ANALYSIS

Similar accidents investigated by the Bureau of Air Safety Investigation:

Four fatal mid-air collisions that involved at least one glider have occurred since 1990, in or near the circuit area of airfields where considerable gliding activity was taking place:
Tocumwal NSW, 2 November 1990, mid-air collision VH-CAG/VH-GXO;
Tocumwal NSW, 8 February 1992, mid-air collision VH-UKT/VH-GQR;
Jondaryan Qld, 1 November 1992, mid-air collision VH-SCT/VH-WQR;
Benalla Vic, 24 November 1993, mid-air collision VH-AYB/VH-GMN.

Including the latest accident at Tocumwal, a total of eight fatalities have resulted from these five accidents.

A procedure for the use of radio to broadcast position and intentions near the circuit area would have lessened the risk of collision.

The Gliding Federation of Australia (GFA) produces a handbook for glider pilots (Airways and Radio Procedures for Glider Pilots), which mentions the use of radios in a CTAF but does not specifically recommend a circuit entry call (see attachment 1).

Recommendations have been made by various state coroners regarding the use of radios near the circuit area to minimise the risk of collision.

The coroner who carried out the inquest into the midair collision at Tocumwal on 8 Feb 1992 recommended that a Mandatory Traffic Advisory Frequency (MTAF) be established for the purpose of pilot to pilot communication within the traffic area. He believed that if the glider pilot had been required to broadcast his intention to modify his circuit on the gliding frequency, the pilot of the tug involved in the collision would have heard this transmission. He also believed that in those circumstances, it is unlikely that the accident would have happened (see attachment 2).

As the limitations of unalerted see-and-avoid to prevent collisions are well known, better use of radios now fitted to most gliders would reduce the risk of collision near the circuit areas of busy gliding airfields. Although powered aircraft also operate into CTAFs where there is gliding activity, they are normally easier to see than gliders, especially from directly in front or behind. Powered aircraft normally fly a more predictable circuit pattern and are less affected by weather conditions in the circuit area. Because of the variable height and speed of gliders in the circuit area, they are considered to pose a higher collision risk than powered aircraft.

Due to the variable speed and tracking involved in glider flying, the requirements for the use of radio in CTAFs, as covered in AIP OPS NCTL-14 (see attachment 3), do not provide sufficient protection from collision. The very large CTAF at Tocumwal (15 NM radius) could result in gliders operating for considerable time away from the circuit but still within the CTAF and therefore not required to make a CTAF entry radio call. On the day of the most recent midair collision at Tocumwal, no calls were heard from the pilot of the high-performance single-seat glider during his last flight of over 6 hours. In addition, CTAF areas where there is considerable gliding activity vary in size from the standard 5 NM radius with some at 10 NM and Tocumwal at 15 NM radius. Because of the differences in dimensions of the CTAFs, the time between the CTAF entry call and circuit entry depends on the airfield. A circuit entry call at 3 NM miles would remove any possible confusion as to the distance a glider is from the field.

The pilot of the glider that approached Tocumwal airfield at high speed on 5 January 1997 was probably practising a competition manoeuvre called a "final glide". A final glide is used during competition to achieve the shortest possible time over the last sector and ends with the glider passing over the timing point on the airfield at low level and high speed. The pilot then rapidly climbs the glider, reduces its speed and positions it in the circuit for landing. While these manoeuvres are expected during a competition, it is unsafe to have gliders that are difficult to see entering an area at high speed when they are not expected, especially if they are performing sudden pull-ups where other aircraft are circling. Modern high-performance gliders have never-exceed speeds (Vne) of over 140 kts and may operate close to Vne during a final glide. Normal circling and circuit speeds are between 45 kts and 65 kts.

Gliders are designed with minimum frontal area to reduce drag and the frontal area of modern high-performance gliders is very small, with the pilot in a semi-reclined seating position, making them especially difficult to see from the front. Most composite gliders are coloured white, giving poor contrast against clouds or hazy sky. Most older metal gliders are unpainted and the bare aluminium finish is reportedly difficult to see against a clear blue sky. The adoption of high-visibility markings may assist pilots in seeing another glider in time to avoid a collision.

Following discussions with BASI, both the Gliding Federation of Australia and the Sports Aviation section of CASA agree that some protection is necessary near busy circuit areas and that a speed limit and radio advisory call should improve safety. Although radio use in gliders is not mandatory in CTAF type operations, some countries in Europe require a pilot to hold a formal radio operator's licence before they can undertake a cross-country glider flight. The GFA is considering introducing similar radio qualifications in Australia.

REFERENCES

1. Gliding Federation of Australia, Airways and radio Procedures for Glider Pilots, March 1996.

2. Document:"Inquest Before Coroner Sitting Alone concerning the death of Alan Leslie Whitely", dated 26 November 1992.

3. AIP OPS NCTL-14, paragraph 4, issued 7 December 1995.

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority in conjunction with the Gliding Federation of Australia:

1. establish a protected circuit area around airfields that have considerable gliding activity;

2. establish a procedure that all inbound aircraft be required to make an all-stations radio call advising their intention to enter the protected circuit area mentioned above;

3. apply a speed restriction of 80 kts indicated airspeed to gliders operating in this protected circuit area at all times other than during official competition events, (aircraft other than gliders should operate at minimum safe speed within the area); and

4. investigate the benefit of the application of high-visibility markings for all Australian-registered gliders.

Initial response
Date issued: 06 December 1999
Response from: Sportavia Soaring Centre
Action status: Closed - Accepted
Response text:

There are three matters relating to air safety that I would like to discuss with you.

1 . Further to the air Safety Accident/Incident Report of 11\3\99 concerning our aircraft VH-GIE and a visiting Aerocommander VH-MIW:

I have developed a "Pilot Information Folder' which contains details of airspace, aerodrome and radio procedures relevant to Tocurnwal and surrounding areas. A copy is kept in each Sportavia glider and copies are held in the Briefing Room. All pilots are required to read and become familiar with the information in the folders. I have enclosed one of these folders for your perusal.

2. After discussion with [name], C.A.S.A Inspector, Wagga Wagga
last month, I have formulated a procedure to record infringements of the Tocurnwal aerodrome airspace. These infringements are not necessarily of the Accident/Incident level but are worthy of being noted and reflected upon. I feel that it is more beneficial to all concerned if these infringements are documented. We have noticed that most infringements occur because, apparently, pilots have not read the E.R.S.A. Pilots flying IFR commercial flights are of the most concern to me being heavy and fast aircraft in the circuit.

I am sending you four Reports that have been compiled since the second week in November. In future I will send these reports monthly.

3. We have started to instigate proceedings through our local Berrigan Shire Council to change the designation of the Tocurnwal airspace from the current CTAF to MBZ status. This change will allow straight in approaches by heavy and/or fast aircraft and in our opinion will lessen the chance of a mid-air collision with gliders in the circuit area. I enclose a copy of our letter to the Berrigan Shire.

I would be happy to hear from you regarding the above three points.


GLIDING RADIO FREQUENCIES

122.9 Tocurnwal Base and C.T.A.F. 119.63 Chat
122.5 Benalla C.T.A.F. 119.83 Chat
122.7 Chat 120.18 Chat
118.03 Chat 122.03 Chat

After 5.30pm contact or blind call Tocumwal Base, and give position every 15 to 30 minutes.

If landing late and unable to contact Tocumwal Base on 122.9 or telephone on 03 58742063 by 2100hrs (9pm). Call International Distress frequency on 121.5. Pass on your approx position and status.

TOCUMWAL C.T.A.F. RADIO PROCEDURE

1. A mandatory 15 nm inbound radio transmission by all gliders

2.A 3nm inbound transmission by all gliders entering the circuit area

3. A radio call on executing the circuit entry

4. 80 Knots or 150 kph indicated airspeed maximum for all gliders in. the circuit area

5. The circuit is defined as below 2400ftQNH and 3 rim radius (730metres QNH, 5.5kilometres)

SAMPLE

TOCUMWAL GLIDER GOLF OSCAR X-RAY
15 MILES NORTH EAST INBOUND AT 450Oft

TOCUMWAL GLIDER GOLF OSCAR X-RAY
JOINING DOWN WIND FOR RUNWAY 36 LEFT

 
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Last update 01 April 2011