Performance Considerations

Part B of the Ops Manual will contain type specific information on procedures associated with take-off and landing on contaminated runways, together with performance data and any wind limitations. (Crosswind, tail wind and possibly headwind gust limits).

SNOWTAMs

SNOWTAMs are issued by aerodromes where contamination is a common occurrence. ATPL students are to be familiar with item (F), type of contaminant, item (G), depth of contaminant over each third of the runway in mm, and item (H), braking action on each third of the runway, stated as a 2 figure number to indicate measured coefficient, or a one figure number to indicate braking action. The validity of a SNOWTAM is up to 24 hours. The codes for types of contaminant are:

NIL CLEAR AND DRY

1DAMP

2WET or water patches

3RIME OR FROST COVERED (depth normally < 1 mm)

4DRY SNOW

5WET SNOW

6SLUSH

7ICE

8COMPACTED OR ROLLED SNOW

9FROZEN RUTS OR RIDGES

The following are examples of SNOWTAMS;

Note: Validity of a SNOWTAM is 24 hours.

(N) 2,6 (R) 2,6 (T) RWY 08l PLANNED TO BE CLOSED DUE TO SLUSH REMOVAL

This decode is as follows:

AMunich

B11 Dec 0810Z

CRwy 08L

FOver the whole of the runway there is slush reported

GThe mean depth of the slush is 1 mm over the entire length

HThe friction measurements are:

Contaminated Runways 19

1.If 30% of the surface area of a runway is covered by surface water more than 3 mm deep, by slush, by loose snow or compacted snow which resists further compression, or ice (including wet ice), the runway is classified as:

a.wet

b.contaminated

c.unusable

d.useable with care

2.If the surface of a runway is not dry, but the moisture on it does not give a shiny appearance, the runway is:

a.wet

b.wet but not contaminated

c.dry

d.damp

3.If a runway is covered with water which is less than 3 mm deep, or where the surface appears reflective but without standing water patches, it is said to be:

a.wet

b.wet but not contaminated

c.dry

d.damp

4.A dry runway is one which:

a.can be wet if it has sufficient camber to allow the water to drain quickly off the surface therefore maintaining an ‘effective dry’ braking action

b.is wet but not to a depth of water greater than 3 mm

c.is not contaminated

d.can be wet if it has specially prepared grooved or porous surfaces, which

maintain ‘effectively dry’ braking action

5.If a runway is contaminated with dry snow, the depth that will preclude operations is:

a.60 mm

b.15 mm

c.10 mm

d.3 mm

6.If a runway is contaminated with wet snow, slush or water, the depth that will preclude operations is:

a.60 mm

b.15 mm

c.10 mm

d.3 mm

Questions 19

Questions 19

7.The effect whereby a tyre is lifted from the runway due to aeroplane speed along the runway is known as:

a.surface water effect

b.hydroplaning

c.aqua-skimming

d.surface tension

8.For any given contaminant (by specific gravity), the aquaplaning speed is given by:

a.nine times the square of the tyre pressure (lb/sq in)

b.the tyre pressure (bars) divided by nine

c.nine times the square root of the tyre pressure (lb/sq in)

d.the square root of the tyre pressure (bars) multiplied by nine

9.One bar (barometric pressure unit) is equal to:

a.14.5 psi

b.28.82 in Hg

c.29.92 lb/sq in

d.1013.25 hPa m-2

10.Braking action on contaminated runways is given by:

a.a simple code (1 – 5) or a description (excellent - bad)

b.a simple code (0.25 – 0.4) or a description (good – bad)

c.a simple code (1 – 5), a description (good – poor) or the measured coefficient of braking effect (< 0.25 - > 0.40)

d.the coefficient of braking action related to a simple code where 1 is poor and 5 is good, supplemented by a description of the braking effect and an aquaplaning warning

11.Apart from aquaplaning and reduced braking efficiency, what other hazards are associated with heavy rain contamination of runways?

a.Wet aeroplanes do not perform as well as dry ones

b.The efficiency of jet engines is reduced by the ingress of water diluting the fuel

c.The refraction of light from landing lights causes visual impairment

d.Water ingress into engines can cause flame-out

12.In a SNOWTAM information is given concerning friction measurements (braking coefficient × 100) in which field of the message?

a.F

b.G

c.H

d.N