Grüße und Vorstellung » e potential for hydroplaning on these surfaces

Research for this article about hydroplaning was gleaned from many sources. The biggest contributor was Thomas J Yager’s Research Memorandum Letter 85652 from the NASA research center in Langley Twins Kirby Puckett Jersey , Virginia. The Boeing aircraft company and the Flight Safety Foundation also provided generalized information. Extracting and simplifying relevant information for the line pilot to help the decision making process when confronted with a potential hydroplaning scenario is the objective for this article.

Most pilots are familiar with the three types of hydroplaning: Viscous Hydroplaning, Reverted Rubber Hydroplaning, and Dynamic Hydroplaning.

Viscous Hydroplaning can occur on all wet runways and is a technical term used to describe the normal slipperiness of wet runway surfaces. It does not normally reduce friction to a point that inhibits wheel spin up after touchdown Authentic Justin Morneau Jersey , or prevent the synchronous properties of the anti-skid system from functioning. It is the most commonly encountered source of low braking efficiency on wet runways. It is often mistaken as dynamic hydroplaning. When a pilot experiences the effects of trying to turn-off a runway at a 90 degree intersection with a little too much forward speed, the resulting slide is the direct effect of viscous hydroplaning coupled with Newton’s first law. Oil and dusty surfaces can also have the same results.

Reverted Rubber Hydroplaning usually occurs when the wheels become locked on a wet or icy runway. The resulting friction causes heat which in turn melts the rubber compound in contact with the runway surface. The heat generates steam which lifts the tire from the surface often leaving a light grey streak on the runway surface.

Chance encounters with this type of hydroplaning have been significantly reduced by the advances of anti-skid and Boeing designed auto-braking systems.

Dynamic Hydroplaning occurs when there is excess water on the runway and the aircraft ground speed equals or exceeds the escape velocity of the water drainage from the footprint. At this point, choked water flow causes a buildup of dynamic pressure between the runway surface and the tire. A wedge of water then begins to partially or fully detach the tire from the runway surface. This results in a significant loss of braking efficiency and can lead to partial or full loss of directional control. This maybe further aggravated by cross winds especially at velocities over 10kts.

The British government first recognized the dangers of hydroplaning in the late 1950s. The Royal Air Force wanted to reduce the number of incidents they were experiencing under wet and standing water runway conditions. A study discovered that grooving and crowning runways improved the braking efficiency and drainage capabilities. As a direct result of this research Authentic Rod Carew Jersey , the US and many other countries around the world have made grooved and crowned runway construction a standard.

NASA has graded the different types of runway surfaces based on runway texture (macrotexture), and the depth of grooves and crowning. Class 1 runway surfaces have the highest macrotexture depth values and Class 5 have the lowest macrotexture depth values. Since the potential for dynamic hydroplaning varies inversely with the runway surface texture, Class 1 surfaces are identified as having the least hydroplaning potential whereas Class 5 surfaces are considered to be the most susceptible.

Class 1:- Deep grooves Authentic Bert Blyleven Jersey , 2% crown, open texture. Porous friction course overlay. The potential for hydroplaning on these surfaces is LOW.

Class 2:- Shallow grooving, scoring and wire combing some large aggregate and asphalt. The potential for hydroplaning on these surfaces is POOR

Class 3:- Heavily textured concrete Authentic Kent Hrbek Jersey , some mixed-gradation, aggregate asphalt. The potential for hydroplaning on these surfaces is FAIR.

Class 4:- Lightly textured concrete, most small aggregate asphalt. The potential for hydroplaning on these surfaces is GOOD.

Class 5:- Very little texture Authentic Tony Oliva Jersey , rubber coated and heavily trafficked. The potential for hydroplaning on these surfaces is HIGH.

Where do these different surfaces fit in to the overall scheme of things? The US, Canada, and most of the countries in Europe Authentic Paul Molitor Jersey , have runways that fit in to the first 2 classes. Unfortunately, in certain countries in the Caribbean, Mexico and South America the level of construction falls in to the class 4 & 5 area. This means that the exposure to the risk of a hydroplaning encounter is significantly increased.

The one glaring example of this significant increased risk is Mexico City. The runway surface there falls between class 4 and 5. The density altitude increases the TAS well above the hydroplaning threshold speed Vp Authentic Harmon Killebrew Jersey , see fig 1. The subtle indentations along the runway tend to puddle water especially after a heavy rain shower. This would then easily meet the FAA criteria for contaminated runways. A runway is considered contaminated when more than 25% of the runway surface area (whether in isolated areas or not) within the required length and width being used is covered by surface water more than 18 of an inch or 3mm deep or slush and loose snow equivalent.

The conditions in the US are the best in the world. Too often one can be lulled in to a false sense of security, especially if one has not operated an aircraft out of the United States for several months.

There are many variables that effect the hydroplaning equation. The following matrix shows the variables and puts them in an easy to understand process flow.





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