Aviation Topic of the Week
By Michael Oxner, December 14, 2003


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This week's topic:
Aircraft Movement Surface Condition Reports

Completely in line with the season, we'll take a real world turn to runway surface conditions. I have to admit, I hadn't yet heard them called by the name used as the title this week, but apparently that's the official name. I've heard "Runway Surface Condition" reports, abbreviated to "RSC", and "Runway Condition Reports", abbreviated to "RCR", and a few others, but not the official name. Funny what you pick up when you read.

Purpose of AMSCR
Description of Terms
When AMSCRs are Issued
Example

Purpose of AMSCR

The AIP, AIR 1.6.4, is our primary reference for this week's topic. The AMSCR is intended to provide pilots with advance notice of runway conditions. The format of the report is intended to give a plain language description, allowing the pilot to get a picture of the runway environment. As it's called, runway "contamination" can make a big difference in how the aircraft handles, and can make the difference as to whether a runway is even useable. Braking performance is affected to various degrees by different types of runway contamination, as is an aircraft's ability to handle crosswind components. Also, many people don't consider the effects on take-off ability. Trained pilots in the real world will. Read on.

Light aircraft generally don't have to consider it, since many runways in use are very long, but larger aircraft must consider braking on take-off. In the event of a rejected take-off, the aircraft must have enough runway to abort without overrunning it. This is particularly important if snowbanks are at the far end, or if there is soft turf beyond the runway. Rejecting a take-off might occur whether an engine fails before V1, gauges give bad readings on throttle up, or whatever. Runway contaminants affect the braking ability here just as well as for arrivals. For example, on a bare and dry runway, a jet may normally, considering runway slope, current temperature, pressure and humidity, and winds, require 5,500 feet of runway to complete a take-off roll to V1 and, using proper technique, come to complete stop. A wet runway may increase that distance significantly, maybe upwards of 8,000 feet. Now put a little snow or slush into the picture and a pilot may not be able to ensure a safe take-off on a given runway.

For the real world, I'll offer one recommendation when requesting runway reports from ATS personnel. Don't call on GND frequency for the destination airport when you're in the air. The problem is that many airports share a common frequency for GND. For example, Halifax International uses 121.9, and so did Saint John when the tower was open there a few years back. This means that when an aircraft halfway between the two airports (100 NM apart) called Saint John GND in the air at 14,000 feet, everyone on 121.9 at Halifax heard this call. This ties up another airport's frequency unnecessarily. If the report needed cannot be obtained from the ATC of FSS unit working your flight, ask them for another frequency or call the TWR instead. At least the TWR frequency is expected to be used for airborne aircraft, so the likelihood of interfering with another unit on the same frequency is reduced, even though it still exists depending on you distance from destination and your altitude. If TWR is too busy to provide this for you, you may have to put off your landing until you can get the information required. If at all practical, you should try to find a runway report in NOTAMs before you leave.

Description of Terms

As mentioned earlier, this is intended to be a plain language report. While the concepts are pretty much standardized, the descriptive terms allow flexibility in order to provide a reasonable snapshot of what can be expected.

The conditions typically considered when reporting runway conditions include, but are not limited to, the following list:
  1. Bare and dry pavement
  2. Bare and wet pavement
  3. Frost cover
  4. Loose snow, and its depth
  5. Slush
  6. Snow drifts (snow cover uneven in depth)
  7. Compacted snow
  8. Ice
The contamination by any of the above listed terms is generally given in terms of a percentage of cover. If a runway has received snowfall and snow removal hasn't commenced, the report would be likely to include merely, "100% snow covered, up to 4 inches in depth", or whatever the depth would actually be. In the case of drifting where the surface is uneven in depth, the deepest value is likely to be used. When snow removal has commenced, the runway is generally first cleared to length, often leaving the edges for a later period. This ensures the runway is useable with better conditions where required most. If this is the case, the report will indicate the width of the cleared "centerline", and it will also indicate the remaining portion of the runway and the conditions there. See the examples below. One thing I'll mention here, though, is that in such a case, there will often be little hills of snow lining the edges of the cleared portion. These are called "windrows", and are expressed with that term and their depth, if they exist. Occasionally, a runway may be cleared in the central portion, but it may not be centered on the runway. If more of the runway is cleared on one side of the centerline than on the other, both sides will be described individually. For gravel runways where reports are issued, it is common not only to report the surface contamination, but also what underlies the surface. For example, they might report "snow on top of ice".

When AMSCRs are Issued

A Notice to Airmen (NOTAM) is issued for a field whenever winter maintenance is provided and any of the following runway conditions exists:
  1. Slush or wet snow on the runway;
  2. Loose snow exceeding a depth of 1/4";
  3. The runway is not cleared to full width. When the runway is partially cleared the report will also include a description of the uncleared portion(s);
  4. The CRFI reading is 0.40 or less.
The last one, CRFI, is the Canadian Runway Friction Index, and I'll go into that one next week in a separate topic.

Examples

The NOTAMs will be published with the location identifier, the term "RSC" to identify the report, the report information, and the date-time group. The standard format for the date-time group is 10 digits, beginning with the last two digits of the year, and two digits for each month, day, hour and minute. Just remember largest unit to smallest. The time, and the date, will always be UTC. I mention this because UTC is ahead of all regions in Canada, so a report late in the day might seem to have the wrong date. For example, 0300z on the 08th day of the month UTC is actually 2200 EST on the 07th. Here are some examples, right out of the AIP.

For paved runways:
This one was not in the AIP. I made it up for the sake of an example:
For gravel runways:
The lack of punctuation, namely periods, does make these a little difficult for the uninitiated to read, but you get used to them fairly quickly. Also, taxiway and apron surfaces are generally reported when airports provide winter maintenance, although ATS personnel may or may not have access to that information.




A recent storm at home in Moncton, and a reader request, started this topic. Next we'll move on to another winter consideration (CRFI). I'm reachable at my regular e-mail, moxner@nbnet.nb.ca. Thanks for taking the time to read!