Braking Action Table
The birth of the ICAO Braking action table
Scandinavian perspective
Before 1950
Prior to 1950 the term Good, bad and indifferent, as practised in UK, were used for estimation of braking action with respect to aircraft operations. Triggered by the wish to concentrate as much as possible of the traffic in the Oslo area, DNL (SAS) wanted to transfer the continental traffic with DC-4 from Gardermoen airport to Fornebu airport. For winter operations a testing program was initiated and led by the airport manager at Fornebu, Ottar K. Kollerud. The outcome was a method using a GMC six by six,10 wheeler truck which was brought to a complete stop from a speed of 40 km/h. Stopping distance and stopping time was measured, and a retardation number (R m/sec2) generated. This was related to the stopping performance of the aircraft. The method got official Norwegian approval 18th January 1950.
1950 – 1960
Norway: The Kollerud method – also known as “Full stop method” were used at Fornebu airport throughout the 50’s. For the rest of the Norwegian airport the braking action was assessed.
Estimate - Retardation (R)
Good ≥ 2.7
Medium 2.2 – 2.6
Poor ≤ 2.1
In March 1954 Ottar Kollerud made a report describing the method. Report on the procedure for correction of Minimum Runway Length under Winter conditions at Oslo Airport, Fornebu. When ICAO published their first Circular with respect to operations on snow and ice, the Kollerud report was part of that Circular. (Circular 43-AN/38, Ice and Snow on Runways, 1955)
Denmark: The Kollerud method was also used at Kastrup airport, but from the winter 1957-58 the Tapleymeter were used.
Estimate - Measured friction
Good ≥ 0.35
Medium 0.26 – 0.34
Poor ≤ 0.25
Finland: Tapleymeter installed in 6.5 ton Sisu truck used at all airports from the winter 1959-60. Together with pilots following table were used.
Estimate - Measured friction
Good ≥ 0.45
Medium 0.30 – 0.44
Poor ≤ 0.29
Sweden: At Bromma airport four methods were tested. The Kollerud method, Taplymeter method in two different configurations, and the “skiddometer” method. At other airports the Tapleymeter were used.
Estimate - Measured friction
Good ≥ 0.35
Medium 0.25 – 0.35
Poor ≤ 0.25
According to regulations from 1958 the term medium could be divided into medium to good or medium to poor when close to the limits for good and poor respectively.
Harmonising
At a meeting in Stockholm 13th to 14th October 1959 the estimation of braking action were harmonised between Norway, Denmark, Finland and Sweden and one agreed upon using following table for Tapleymeter measurement at compacted snow and ice surfaces.
Estimate - Measured friction
Good ≥ 0.40
Medium to Good 0.36 – 0.39
Medium 0.30 – 0.35
Medium to Poor 0.26 – 0.29
Poor ≤ 0.25
ICAO
When ICAO (1967/68) established the SNOWTAM-format (Annex 15) this braking action table became a part of the SNOWTAM-format and thus became the world standard.
And now to my question:
Have a look into your manuals and tell me how many different braking action tables are in operational use today (46 years later)?