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CONTINGENCY FLIGHT RULES
Weather criteria for an emergency landing must be considered along
with launch criteria since the possibility exists for a Return To Launch
Site abort (RTLS), landings at the Trans-Oceanic Abort Landing Sites (TAL),
the Abort Once Around (AOA) sites and the first day Primary Landing Site
(PLS). These forecasts are prepared by the NOAA National Weather Service
Spaceflight Meteorology Group in Houston and briefed by them to the
astronauts, Flight Director and Mission Management Team. All criteria refer
to observed and forecast weather conditions except for the first day PLS
which is forecast weather only.
 For RTLS with redundant Microwave Landing System (MLS) capability and a
weather reconnaissance aircraft, cloud coverage 4/8 or less below 5,000 feet
and a visibility of 4 statute miles or greater are required. For AOA and
PLS sites, cloud coverage 4/8 or less below 8,000 feet and a visibility of 5
statute miles or greater is required. For TAL sites, cloud coverage 4/8 or
less below 5,000 feet and a visibility of 5 statute miles or greater are
required.
For landing on a hard surface runway without redundant Microwave Landing
System (MLS) capability all sites require a ceiling not less than 10,000
feet and a visibility of at least 7 statute miles. Landing at night on a
lake bed runway may occur if the ceiling is not lower than 15,000 feet and
the visibility is 7 miles or greater with at least non-redundant MLS
capability .
For the RTLS site and TAL sites, no thunderstorms, lightning, or
precipitation within 20 nautical miles of the runway, or within 10 nautical
miles of the final approach path extending outward to 30 nautical miles from
the end of the runway.
An RTLS rule exception may be made for light precipitation within 20
nautical miles of the runway if the specific criteria listed below are met:
- The tops of the clouds containing precipitation do not extend into
temperature regions colder than 41 (F.); they have not been colder than 14
(F. ) within 2.5 hours prior to launch; the radar reflectivity is less than
30 dbz at all levels within and below the clouds.
- Precipitation covers less than 10% of the area within 20 nautical miles
of the runway, or multiple heading alignment circles are clear of showers.
- The movement of the showers is observed to be consistent and no
additional convective development is forecast.
- Touchdown/rollout criteria and associated navigational aids meet the
specified prelaunch go/no go requirements.
If showers exceed either parameter of part a.) above, an RTLS landing
may still occur if a 2 nautical mile vertical clearance can be maintained
from the top of any shower within 10 nautical miles of the approach paths.
For RTLS and TAL sites, no detached opaque thunderstorm anvils less than
three hours old within 15 nautical miles of the runway, or within 5 nautical
miles of the final approach path extending outward to 30 nautical miles from
the end of the runway.
For AOA and PLS sites, no thunderstorms, lightning or precipitation
within 30 nautical miles of the runway, or within 20 nautical miles of the
final approach path extending to 30 nautical miles from the end of the
runway.
For RTLS and the TAL sites, no detached opaque thunderstorm anvil cloud
less than 3 hours old within 15 nautical miles of the runway or within 5
nautical miles of the final approach path extending outward to 30 nautical
miles from the end of the runway.
For AOA and PLS sites, no detached opaque thunderstorm anvil cloud less
than 3 hours old within 20 nautical miles of the runway or within 10
nautical miles of the final approach path extending to 30 nautical miles
from the end of the runway.
The RTLS crosswind component may not exceed 15 knots. If the astronaut
flying weather reconnaissance in the Shuttle Training Aircraft executes the
approach and considers the landing conditions to be acceptable, this limit
may be increased to 17 knots. For the TAL, AOA and PLS sites there is a
night-time crosswind limit of 12 knots.
Headwind: not to exceed 25 knots.
Tailwind: not to exceed 10 knots average, 15 knots peak.
Turbulence: conditions must be less than or equal to moderate intensity.
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