Glossary
Alaska Airstrip Types
bush strip – A remote airstrip, typically unimproved and not connected to the road system. A bush strip may be difficult to spot from the air, consisting only of wheel tracks visible on a natural feature such as alpine tundra or a braided river bar.
cub strip – A short, challenging airstrip, typically in a remote location. Cub strips may be rough, narrow, or one-way. They require a highly skilled pilot and the ruggedness and STOL performance typical of a bush-modified Piper Super Cub.
natural feature – A naturally occurring landform. In our context, a natural feature is a naturally occurring landform (with or without vegetation) that has been or could be used as an airstrip or landing site. Some natural feature types may lack visible evidence of previous landings because of surface integrity. Visible wheel tracks may be ephemeral due to flooding, ecological succession, weathering, or erosion.
one-way strip – An airstrip or natural feature where a go-around is not possible or prudent beyond the abort point.
sheep strip – An airstrip or landable natural feature (often a cub strip) that provides access for Dall Sheep hunting. Sheep strips are typically located in mountainous terrain and can be very hazardous.
Bush Flying / General Aviation
abort – The premature termination of a flight procedure, e.g. the approach or takeoff (ground roll) phases of flight.
abort point – A point during the approach or takeoff phase beyond which a termination of the procedure may yield undesirable and/or catastrophic results.
abort point, landing approach – The point beyond which discontinuing the approach (going around) is not safe or possible and the airstrip is considered one-way.
abort point, takeoff – The point beyond which aborting the takeoff is considered to be unsafe. In bush operations, continuing the takeoff run beyond the abort point is often necessary to get airborne – especially in a heavily loaded airplane.
bush mods – Airplane modifications to enhance safety, durability, utility, and STOL performance for private and commercial off-airport/bush flying operations. Popular bush mods include shoulder harnesses, tundra tires, heavy-duty nose wheel fork, high-pressure double-puck brakes, heavy-duty extended landing gear, landing gear long step, bush shocks (main gear suspension), landing gear safety cables, two-bolt tailwheel, fat tailwheel tire, 1.5″ tail spring or tailwheel suspension system, climb prop, PSTOL flaps, leading-edge wing cuffs, vortex generators, over-spar wing tie-downs, spar lifting eyes, extended baggage, cargo pod, gross weight increase, long-range fuel, all-metal gascolator, and engine power upgrades.
bush pilot – A pilot who operates (flying, navigating, landing and taking off) small airplanes in remote and often uninhabited areas.
bush plane – Airplanes used for bush flying operations in remote, undeveloped areas that lack ground transportation options. High-wing conventional landing gear configurations (tailwheel or taildragger airplanes) with bush/STOL modifications are preferred. Proven examples include the Piper Super Cub (PA-18), Cessna Skywagon (C-185 and C-180), DeHavilland Beaver (DHC-2), DeHavilland Otter (DHC-3), and the less common Helio Courier. Tricycle gear configurations (nosewheel airplanes) are used for less hazardous airstrip surface conditions. Popular models include the Cessna Stationaire (C-206), Cessna Stationaire 7 (C-207), Cherokee Six (PA-32), and Cessna Caravan (C-208).
decision point – A point in space and time when a final decision must be made.
decision point, landing approach – A point during the landing approach when the final decision to either land or to abort must be made. The decision point precedes the abort point allowing time for a go-no-go decision to be made.
crosscurrent – Current with a perpendicular component to the approach path or landing track of an airplane, i.e., the current direction is not parallel to the flight path.
field repair – Improvised, makeshift repairs, often urgent in nature, accomplished at inconvenient or remote locations without available resources such as infrastructure, communication, parts, tools, and sometimes without the aid of a certified mechanic. Field repairs are often temporary with the goal of getting the plane out of the bush or ferrying it to a location where permanent repairs can be made.
STOL – Acronym for “short takeoff and landing” used to describe the performance characteristics of a small airplane.
tundra tires – Oversized airplane tires commonly used on bush planes that enable landings on rough terrain; also for exhibition. Tundra tires such as Alaskan Bushwheels, are sometimes under-inflated to improve cushioning, floatation, and minimize bounce. Taildraggers run the largest sizes (29”, 31”, and 35”) and often have corresponding fat “baby Bushwheel” tailwheel tires.
Vc current speed – The speed of the water current component aligned with the landing track.
Vm safety margin – Additional speed that is added for safety (this is usually a subjective value).
Vp penetration speed – The airplane’s speed, relative to water, at which point the airplane’s main wheels begin hopping or progressively penetrating.
Vwater waterski speed – Minimum (safe) water touchdown ground speed.
Natural Environment
alluvial fan – A low, outspread mass of loose materials such as silt, sand, gravel, rocks, and mud shaped like an open fan, deposited by a stream. It is steepest near its apex which points upstream and slopes gently and convexly outward (downstream) with a gradual decrease in gradient
ash flow – (aka pyroclastic flow) A superheated mixture of volcanic gases and ash, traveling down the flank of a volcano or along the surface of the ground forming a sheet; produced by the explosive disintegration of viscous lava in a volcanic crater, or by the explosive emission of gas-charged ash from a fissure. The solid materials contained in a typical ash flow are generally unsorted and ordinarily include volcanic dust, pumice, scoria, and blocks in addition to ash.
beach terrace – A landform that consists of a wave-built terrace of well-sorted sand and gravel of marine (sea) or lacustrine (lake) origin.
braided river – A river (or stream) with multiple channels that interweave as a result of repeated divisions and convergence of flow around bars, resembling the strands of a complex braid. Braiding is generally confined to broad, shallow rivers and streams whose overall courses are not intricate or overly winding that have non-cohesive bank material and high bed load.
diurnal —Having a daily cycle; showing periodic alteration of conditions with day and night.
diurnal winds — Diurnal winds are cyclic, 24-hour wind patterns driven by the sun’s heating and cooling of terrain. In complex topography, e.g., mountains, diurnal winds shift based on the sun’s position and thermal gradients.
- Daytime (Valley Winds): Air on mountain slopes warms and becomes more buoyant, causing it to rise. Cooler, denser air in the valley settles and pushes up the slope, replacing the rising air.
- Nighttime (Mountain Winds): As the sun sets, the earth’s surface cools, making the adjacent air denser and causing it to sink and flow down the slopes into the valleys.
estuary – (a) A seaward end or the tidal mouth of a river valley where fresh water comes into contact with seawater and where tidal effects are evident. (b) A portion of an ocean or an arm of the sea affected by fresh water.
glacial outwash – Stratified and sorted sediments of sand, gravel, and silt washed out from a glacier by melt-water streams and deposited downstream of the end moraine or the margin of a glacier. The coarser material is deposited nearer to the ice.
kame terrace – An elongated, relatively flat-topped bench or constructional terrace composed of stratified glaciofluvial or glaciolacustrine sediments. It is deposited by meltwater streams or by trapped proglacial water bodies within the trough between the lateral margin of a glacier and the adjacent, ice-free valley wall. Following the complete thermal ablation and retreat of the supporting ice mass, these proximal edge accumulations are left stranded as elevated, positive-relief landforms along the hillside.
marginal valley (lateral moraine trough) – An elongated, linear topographic trough formed between the outer (distal) flank of a lateral moraine and the adjacent sideslope. Mass wasting from the mountainside – rockfalls, avalanches, and debris flows cannot reach the main glacier because of the dam formed by the lateral moraine.
Minor side valleys and gullies dump alluvial and debris-flow sediment directly into the trough, which is filled, sorted, and leveled by fluvial and lacustrine processes. While glaciers themselves produce unsorted, coarse rocky debris (till), the unique micro-environment of a marginal valley filters out these large boulders, filling the space with highly stratified, sorted, and leveled finer sediments.
The long, linear shape and fluvial sorting of marginal valleys often produce relatively smooth and flat landing sites in an otherwise unlandable alpine environment.
muskeg – A sphagnum bog, sometimes with hummocks, growing in wet, poorly drained boreal regions often occurring in but not exclusive to areas of permafrost.
stream terrace – Flat-topped landforms in a stream valley that flank and are parallel to the stream channel, originally formed by a previous stream level, and representing remnants of an abandoned flood plain, stream bed, or valley floor.
toe-cut fan – An alluvial fan whose distal margin has been laterally truncated by a cross-cutting axial river, resulting in an erosional scarp that disconnects the fan body from the local base level and forces incision of its tributary drainage network.
tidal flat – An extensive, nearly horizontal, barren or sparsely vegetated tract of land that is alternately covered and uncovered by the tide, and consists of unconsolidated sediment (mostly clays, silts and/or sands and organic materials).
tundra – A treeless zone with low temperatures and a short growing season. Alpine tundra is found at high elevations. Arctic tundra is found north of the permafrost line, generally north of the arctic circle.
water course – A natural channel through which water flows. Watercourses, aka water channels, may be dry.