1. Rovaniemi airport EFRO
cold and humid climate
Photo: Sippo Nevalainen

2. Rovaniemi is situated in North Finland (They say, that Santa lives next to us…)

3. EFRO Arctic Circle latitude 66,3
Runway 3kmx60m
21: heading direction 210
03: heading direction 030
Altitude differences:
03 : 633ft
21 : 609ft
midpoint: 642ft !
Altitude from
EFKE:n 600ft
@ The Comet program

4. In Finnish sky : During wintertime no convective clouds (cumulus, cumulonimbus), but stratiform clouds…
Stratus has a very low cloudbase
Stratus can be very local
Stratocumulus

5. EFRO in wintertime
Photo: Tapani Kuoksa

6. Rime and frost are typical for cold and humid climate

7. AGA 3-10 includes national regulations for runway friction
2.3.3 Each airport maintenance shift shall have a nominated person responsible for ensuring that runway inspections and friction measurements are carried out and their results reported appropriately. The airport manager or a person designated by him shall select and list those members of airport staff who are qualified to perform friction measurements and runway inspections, and friction assessments where necessary.
2.3.5 The verbal assessment corresponds to the measured friction
Measured or calculated coefficient Estimated braking action Code
0.40 and above Good 5
0.39 to Medium to good 4
0.35 to Medium 3
0.29 to Medium to poor 2
0.25 and below Poor 1
Unreliable Unreliable 9
Friction is reported for every third of runway lenght

8. How to improve friction?
3.2.3 Apart from urea, only such chemicals shall be used for friction improvement that have been determined to meet the current applicable SAE Aerospace MaterialSpecification or any equivalent European standard.
3.2.4 If sand is used, grain size must be such that all particles pass a 4 mm sieve. If any oversized particles, stones, solid pieces or foreign objects are found in the material, that load of sand shall not be spread over areas used by turbojet aircraft unless it is sieved again.
3.2.5 When sand is no longer needed, it shall be removed from the pavement
AGA M3-10

9. Monitoring and measuring friction
2.1.5 For monitoring the changing runway conditions, every airport shall have a surface temperature meter or ice warning system with sensor(s) permanently installed on runway surface and a display located in the airport maintenance duty room.
AGA M3-10

10. Airport runway maintenance uses Vaisala Rosa DM32 program
-some theoretical examples when slippery conditions appear – or not
-real examples by Rovaniemi airport collected by Tapani Kuoksa

11. Radiative cooling during a cloudless calm night
Ilman lämpötila
Kastepiste
Pintalämpötila
Air temperature
Dew point
Surface +4 +3 +2 +1
Explain what happens between at surface level. Why? -1 18 03 06 24

12. Warming after a lond cold period+1 -1 -2
Air temperature
Dewpoint
Surface
Explain, what happens after 14 o’clock on runway surface. Explain, why. -3 -4 -5 09 15 18 12

13. Influence of topography
Air temperature
Dew point
Surface
0oC
What happens at the place an arrow shows? Does it affect the friction?
-8C 1km 2km 3km

14. 3.7.2008 In July afternoon. Runway temperature can reach +42 oC
Air temperature
Dew point
Surface
Relative humidity
In July afternoon. Runway temperature can reach +42 oC
Cloudiness
Rainfall
Warning
Alarm
In July afternoon. Runway temperature can reach +42 oC

15.
An autumn day: During early morning air temperature sinks near zero, surface tempeperature below zero and is colder than dewpoint. On the runway there developes hoar frost and a warning is on. After sunrise temperature rises , the most rapid rise takes place in runway temperature, and runways is getting dry.
An autumn day: During early morning air temperature sinks near zero, surface tempeperature below zero and is colder than dewpoint. On the runway there developes hoar frost and a warning is on. After sunrise temperature rises , the most rapid rise takes place in runway temperature, and runways is getting dry.

16.
In the morning on there is hoar frost on the runway. When surface temperature rises higher than dewpoint temperature, hoar frost will evaporate. After 16:00 o’clock all temperatures drop below zero, warning is on. Sweepers keep friction moderate.
In the morning on there is hoar frost on the runway. When surface temperature rises higher than dewpoint temperature, hoar frost will evaporate. After 16:00 o’clock all temperatures drop below zero, warning is on. Sweepers keep friction moderate.

17.
Air temperature goes at 2 o’clock below zero. Runway is wet, chemicals added on the surface and freezing point dropped toward -4oC. Action helped, no warning.
Air temperature goes at 2 o’clock below zero. Runway is wet, chemicals added on the surface and freezing point dropped toward -4oC. Action helped, no warning.

18.
Earlier event continues….. Chemical added again at 13:10 . Purple curve shows how freezing point decreases ( -10 oC), runway surface becomes wet and salty.
Earlier event continues….. Chemical added again at 13:10 . Purple curve shows how freezing point decreases ( -10 oC), runway surface becomes wet and salty.

19.
When surface temperature is several degrees below dew point temperature, it causes heavy formation of hoar frost. Sometimes display shows runway surface state ”snowy”, even there has not been snowfal. .Instrumental false alarm!
When surface temperature is several degrees below dew point temperature, it causes heavy formation of hoar frost. Sometimes display shows runway surface state ”snowy”, even there has not been snowfal. .Instrumental false alarm!

20.
Event continues… mild weather, chemicals added at Decrease of freezing point stops hoar frost formation, state of runway is ”wet”.
Event continues… mild weather, chemicals added at Decrease of freezing point stops hoar frost formation, state of runway is ”wet”.

21.
Friction measured at 17:00 and 21:00 0,30. After 01:10 surface temperature remains below dew point temperature, when temperature is rising. A rapid sweeper drive at 05:00, result is better friction 0.45
Friction measured at 17:00 and 21:00 0,30. After 01:10 surface temperature remains below dew point temperature, when temperature is rising. A rapid sweeper drive at 05:00, result is better friction 0.45

22.
In the morning hoar frost warning. Rapid sweeper drive keeps friction good ( at ,40,43) and at (44,55,57) During night runway temperature drpops below dewpoint temperature and frost formation gets stronger, friction at o’clock 34,34,45)
In the morning hoar frost warning. Rapid sweeper drive keeps friction good ( at ,40,43) and at (44,55,57) During night runway temperature drpops below dewpoint temperature and frost formation gets stronger, friction at o’clock 34,34,45)

23.
Example of too late chemical spreading. Friction at 21:00 good ” 5 ”, runway wet. Right time should have been at 01:00. Luckily this time chemical had enough effect and friction was
Example of too late chemical spreading. Friction at 21:00 good ” 5 ”, runway wet. Right time should have been at 01:00. Luckily this time chemical had enough effect and friction was