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Semi Prepared Runway Operations (SPRO)

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Semi Prepared Runway Operations (SPRO) are most often considered those operations conducted by military aircraft to a marginal airfield or to a temporary landing zone (LZ). However, many of the factors that are discussed in this article are also applicable to light General Aviation aircraft conducting off-strip operations.

SPRO may be used for, but are not limited to, combat operations where flight operations to a semi prepared runway might take place close to the Forward Edge of the Battle Area (FEBA). In many cases, however, semi prepared runway operations are used for disaster support or famine relief operations.

Semi Prepared Runways

A semi prepared runway can take on many forms. In many cases, an existing general aviation airfield is enhanced to enable it to be utilised by the anticipated airlift aircraft types. Such improvements might include lengthening and/or widening of the existing runway, creating ramp areas for offload, removal of trees or other obstacles to create runway clearways and increasing the load-bearing capability of the landing area by using pierced steel planking (PSP) or other engineered materials. In many cases, however, a semi prepared runway, or landing zone, is created simply by clearing a potential landing area, such as a dry riverbed, a field, a frozen lake or a patch of dessert, of snow, rocks, bushes or other obstructions, filling any holes and leveling and strengthening the surface to the extent possible.

Establishing Operations

Quite often, a semi prepared runway is established by elements of the force that intends to conduct operations at that landing zone. In these cases, the location, orientation, dimensions and load bearing capability of the runway are known in advance. In other circumstances, as is most often the case with relief or disaster support operations, the landing zone (LZ) is established by a third party and the location and runway parameters provided to the user may be somewhat vague. In this case, the crew of the first flight into the runway must validate the location, orientation and length of the semi prepared surface and evaluate the landing zone for capability and operational limitations. The following first flight criteria and evaluation methodology for a LZ constructed by a third party might be considered:

  • Choice of Crew - Semi prepared runway operations can impose significant challenges to the crews involved. These challenges might include, but are not limited to, limited or no approach aids, lack of runway lighting, landing distance limitations, obstacles that demand one-way-in, one-way-out profiles, lack of ground support equipment, unavailability of fuel, limitations on the number of aircraft that could be on the ground at one time and so forth. It is, therefore, important that the crew assigned to conduct the LZ validation flight be well experienced on the aircraft type and thoroughly understand both the capabilities and the limitations of the aircraft that will be conducting SPRO at the LZ under evaluation.
  • Intended LZ Utilisation - To effectively assess the operational capability of a semi prepared runway, the evaluating crew must be aware of how the SPRO will be conducted. Primarily, they must know if the LZ is intended for inbound loads, outbound loads or for lift in both directions. They should also be provided with an estimate of the total number of aircraft movements that the LZ might reasonably be expected to sustain.

First Flight Methodology

Wherever possible, the evaluation (or recce) flight should be conducted with an empty or lightly loaded aircraft. The evaluation crew should ensure that they carry enough fuel to fly to the LZ, conduct a number of low passes and touch and go landings prior to actually stopping on the runway, and then spend a period of time on the ground with engines running, prior to returning to the point of origin or other nominated airfield with adequate fuel reserves remaining. The mission should be pre-briefed with all crew present so everyone on board understands the intended flight profile and expectations.

  • Given current GPS technology, it is unlikely that the location of the intended landing zone will be in question. That notwithstanding, the evaluation crew should obtain an appropriate scale topographical chart of the area to permit a pre-study of the terrain in the vicinity of the proposed landing zone. Once the LZ has been located, the aircraft should be slowed to approach speed and several low (200-500' AGL) passes of the runway should be conducted. During these passes the crew should:
    • confirm the useable length of the landing surface using time and groundspeed calculations
    • evaluate both the approach and departure ends of the runway for obstacles and obstructions
    • determine if arrival and departure from the LZ can be made in both directions or if the field will be limited to one way operations
    • observe the immediate area for signs of human or animal activity
    • examine the landing surface for ruts, holes and signs of recent rain (puddles, standing water, washout etc)
    • confirm that there is adequate clearway at runway ends and along the runway edges to safely accommodate the intended aircraft types
    • evaluate if there is sufficient space and clearway to turn around at runway ends

LZ Capability Assessment

Once the observation passes have been completed and the corresponding data recorded, the load bearing capability of the runway should be evaluated as follows:

  • the aircraft should be configured for landing and a touch and go landing profile flown. The touchdown should be made on the runway centreline in the touchdown zone
  • after the touch and go, a low pass should be flown (50-100' as dictated by obstacles), offset from the centreline, to evaluate the depth of the ruts created by the touch and go landing
  • if LZ width and clearways allow, a further touch and go on either side of the original touchdown point can be made to evaluate the overall load bearing capability of the touchdown zone
  • If the load bearing capability of the runway is deemed acceptable, the next task of the evaluation profile is to land the aircraft and evaluate the remainder of the LZ environment. Under most circumstances, the APU and at least one engine should be kept running during the ground time to preclude stranding the aircraft in the event of a subsequent failure

Post Landing Assessment

After touchdown, the Pilot Flying (PF) should quickly bring the aircraft to taxy speed and continue to the end of the runway. Once at the end of the runway:

  • the aircraft should be turned around noting any wing tip clearance issues or soft areas near the end and edges of the runway or turning bay
  • the aircraft should then be taxyed the full length of the runway, offset from the centreline to enable the ruts (if any) from the landing to be evaluated.
  • upon reaching the approach end of the zone, the aircraft should, once again, be turned around and the area evaluated for wing clearance and turning issues such as soft spots or rutting during the turn.
  • the off load area should then be evaluated. This assessment should answer questions such as:
    • surface condition and composition - will it be able to sustain operations during heavy rain?
    • manoeuvring potential and wing clearance
    • dimensions (capacity) - single or multiple aircraft capability
    • is there adequate clearance from the landing surface to allow other aircraft to arrive or depart whilst the ramp is occupied
    • where is the most appropriate siting for ground support equipment (GSE) or fuel storage

Ground Assessment

Personnel will normally be deplaned at this stage to conduct any required load bearing measurement protocols or dimensional measurements and to assess the landing zone more closely. Associated tasks include:

  • assessment of the landing surface for tyre puncture risk
  • assessment of the landing area for soft spots, rut depth, amount of surface material displacement at runway ends during turns
  • determination of clearway length and obstacle height should be assessed at both ends of the LZ

When all of the required tasks have been completed, all personnel should return to the aircraft and prepare for departure. Prior to departure, the mission commander should:

  • confirm that all members of the recce team are on board
  • review the assessment plan and ensure that all intended items have been evaluated


The aircraft should now be restarted, if applicable, and prepared for departure. The takeoff considerations should include:

  • use of the full length of the runway for the departure
  • use of maximum performance takeoff procedures
  • use of timed acceleration protocols to assess any performance penalties that the LZ surface might impose on aircraft capability

The Assessment Report

The mission commander should compile all of the information gathered during the LZ evaluation for submission to the appropriate authorities and eventual dissemination to the airlift crews. The report should include as much detail as possible on the physical dimensions and capacity of the semi prepared runway and ramp area as well as an assessment of the hazards and risks associated with operations at the LZ. Recommendations on the most appropriate arrival and departure profiles, the maximum number of aircraft that can be on the ground at any point in time, what ground support equipment might be required, whether Engine Running Offload (ERO) procedures should be used and if any special aircraft modifications (such as removing antenna from the bottom of the aircraft) are necessary.

LZ Utilisation and Maintenance

The SPRO will generally be initiated using the plan derived from the recce flight. However, as the airlift timings evolve, or if the type and amount of cargo, troops or displaced civilians to be moved in and/or out of the LZ change, some modifications to the airlift plan may be required.

Some deterioration of the LZ should be expected over time. If this deterioration is accelerated due to adverse weather, additional use or heavier than originally anticipated loads, repairs may be required to keep the landing surface operational. As a minimum, the need to fill ruts and holes should be anticipated and sufficient time for LZ maintenance should be built into the airlift plan.