Facts About Airport Sweepers
The runways, ramps, aprons, and taxiways of all private airports, heliports, and international airports, must be kept clear of any debris that could be categorized as foreign object debris (FOD).
FOD can be any material and any size, often smaller than what can be seen by just looking out over an open airport, according to the National Aerospace FOD Prevention, which defines it as a substance, debris, or article alien to a vehicle or system that has the potential to cause harm. Most airports undertake routine FOD checks when airport staff drive back and forth across the runways and taxiways checking for FOD because of the possibility of foreign object damage (FOD). While they conduct their usual checks for larger FOD, several airports have people devoted to operating sweepers on the airfield to sweep any debris.
FOD costs the aerospace sector between $1.1 and $2.0 billion USD annually in direct expenditures and up to 10 times that amount in indirect costs from delays, aircraft changes, additional fuel costs, and unplanned maintenance, for a total of $12 billion USD annually.
Airport management should strongly consider implementing routine sweeping with airport sweepers as a Best Management Practice (BMP) to minimize FOD at their airfields given the high cost of damage that can be caused by FOD that might only be as big as a piece of safety wire as well as any potential injuries caused by FOD.
High Speed Runway Sweeping at Airports
People use air travel as a mode of transportation at an increasing rate each year. Airport managers are working to boost aviation traffic while preserving their current resources. Time becomes particularly precious for all tasks carried out by airport staff as a result. It is crucial that all FOD be removed from such locations when airport maintenance personnel does normal sweeping over runways, ramps, aprons, and taxiways, but it is also becoming more crucial that those areas be swept rapidly. The United States Military have a High Speed Runway Sweeper Performance Specification, which called for six distinct tests to be performed over 13 000 square metres of level, paved ground.
- Sand Test: 0.5 lbs/sq ft at 15 mph with a required performance of 95%
- Test for Pea Gravel: 0.5 lbs/sq ft, 95% of Required Performance at 15 mph
- Ten stones with a nominal diameter of 2″ and a required performance of 100% at 15 mph are used in the stone test.
- Ten 1″ diameter by 3″ long solid steel cylinders with a required performance of 100% at 15 mph were tested.
- Joint Cleaning Test: Sand-filled joint measuring 1/2 inch by 1/2 inch by 6-and-a-half feet with a required performance of 40% at 15 mph
- Seven of each of the following objects were put on the track for the miscellaneous pick up test. Performance of 54 pieces at 15 mph is necessary.
- Balls – 1/2″ diameter
- Nails – 2-1/2” long
- Flat Washers – 1/2 I.D.
- Screw Cap – 1/4″ diameter x 2”
- Hexagon Nut – 1/2″
- Air Craft Safety Wire – 1/2″ long, crumpled
- Sheet – 2” sq x 1/8” thick
- Rivets – 1/4″ diameter x 1”
What is FOD
Foreign Object Damage or FOD
The question, “What is a foreign item that might harm an engine? ” has a number of potential responses. For this reason, everything that enters the engine from the outside (Foreign Object Damage = FOD) or originates in the engine itself (Own Object Damage = OOD or Domestic Object Damage = DOD) and is not a part of the normal inlet air or the specified auxiliary materials is referred to in this chapter as a “foreign object.” Foreign items include particles that contaminate the oil flow as well as erosive (Chapter 5.3) and corrosive (Chapter 5.4) media in the air flow. Foreign items might also include bolts that come loose within the engine.
Weather factors like ice, hail, and rain, which were covered individually in Chapter 5.1, may also be seen broadly as alien objects.
Because huge, hard foreign items and foreign objects with a technological origin may be distinguished from bird attacks and weather elements, the categorization of foreign objects into “non-biological foreign objects” and “bird strikes” was made at random.
If corrosion and erosion are also included under FOD, FOD becomes a determining factor for engine cost, accounting for more than 50% of the whole cost of purchase in military equipment, for instance (Fig. “Overhaul statistics”). Parts with FOD exceeding the limitations indicated (as described in maintenance manuals, overhaul handbooks, etc.) must typically be overhauled, and if this is no longer practicable, replaced.
The risk of short circuits generated by very small pieces of carbon fiber is heightened by the expanding usage of electric and electronic engine components like regulators. These are produced when fiber-reinforced elements, such as fuselage sheeting, are burned or reworked (cut) (Ref. 5.2.1-1).
Dust ingestion may result in erosive compressor wear as well as obstruct cooling air ducts in hot sections, raising temperatures to dangerous levels.
However, some FOD is reversible and can be removed fairly simply. This includes fouling of the compressor blading through oil and dust, which sticks to the blades and can greatly decrease compressor performance. Washing and cleaning procedures that remove these coatings are a necessary part of routine maintenance.
Bird strike is one of the most feared types of FOD and is treated in a separate chapter (Chapter 5.2.2) due to its unique effects. However, even insects can have a similarly unallowable, if less spectacular, effect on engines. If insects carried by the airflow become stuck on the blading upon impact, it results in so-called “insect roughness” which can have a considerable effect on compressor performance. For example, in one case a small 100 kW gas turbine ingested a mosquito swarm which worsened the surge limit of the radial compressor so quickly that compressor surges made further operation impossible and required immediate cleaning.
This illustration illustrates the usual foreign object damages. It demonstrates how FOD affects operational behavior, or the effectiveness of the engine’s individual parts and as a whole. These damage processes often have a lengthy incubation time, including erosion, deposit accumulation, or wear.
At the very least, the slow deterioration of engine performance raises the danger of hot component damage (higher temperatures needed to generate the requisite power) and, under unfavorable operating circumstances, compressor surges/stalls.
Some military and older commercial aircraft models use this kind of construction as the intake guide assembly/intake (front) bearing (V1) . When this assembly is impacted, either directly or indirectly via the input cone, many components are put under stress. Experience has demonstrated that compared to setups with spinning nose cones and no intake guide vanes, this design has several drawbacks.
Blade failure is one of the damages that may be caused by strong forces acting on the fan and low-pressure compressor blades (V2). The guiding vanes, which often have narrow profiles and are sensitive to high-speed contact from big bird parts that pass through the fan entire, are especially vulnerable to this. As a result of having to use more energy to accelerate the mass of the swallowed bird, adjustable/variable guide vanes are more susceptible to damage to the adjustment mechanism and/or shutting of the vanes at slower flight speeds.
Bird pieces accumulating on a housing strut in front of the compressor and then colliding with the comparatively delicate compressor blading as a big mass is an illustration of a hazardous scenario.
Spinner (spinning nose cone) (V4): Imbalances brought on by the deformation of metallic spinners and pieces of synthetic fiber-reinforced spinners
Main bearings (V5): The main bearing is temporarily overstressed due to high axial forces (depending on the spinner’s rigidity, for example) and/or dynamic overstress brought on by imbalances (results: fractures, fatigue).
Bird flock (small birds):
Even little birds may cause serious damage to smaller engines, especially if they are exceedingly filigreed and/or built of particularly sensitive materials like fiber-reinforced synthetics or aluminum alloys. Guide vanes of the low-pressure compressor (VS1):
Large volumes of bird matter might accumulate on struts or guiding vanes and enter the compressor as a big mass, causing damage to the high-pressure compressor blading (VS2). This calls for extra attention to be paid to the initial high-pressure compressor rotor stage.
Dust and sand
Fan and low-pressure compressor (S1): Wear, minor notches, and blading erosion.
- High-pressure compressor (S2): In bypass engines, the majority of the sand is kept out of the high-pressure compressor by centrifuging it. On the blading, nevertheless, there will be erosive wear, roughing, and tiny notches (particularly close to the points). The clearance gap at the blade tips will widen when the inner housing wall erodes, particularly where there are soft abradable coatings.
- Labyrinths (S4): The cooling air flow causes erosion of labyrinths.
- Cooled hot parts (S3): Blockages in the cooling air ducts result in overheating and significant life span reductions; adverse responses (hot gas corrosion, sulfidation) with the hot parts’ inner and outer surfaces.
Small rocks and split:
Fan, low-pressure compressor (F1) and high-pressure compressor (F2); small notches that can usually be reworked.
Hail and ice:
Damage to the fan (for example, exit guide vanes made from Al alloys or fiber-reinforced plastics) and low-pressure compressor (H1); because the ice particles melt before impact, no damage is to be expected in the high-pressure compressor. However, a compressor stall (H2) due to the created water and/or unstable combustion or flame-out are possible results (H3). These effects are especially dangerous in hail, because hailstones are more massive than rain drops and less likely to be diverted into the bypass duct, causing a larger amount of water to enter the high-pressure area.
Rain and spray
Rain can cause rain erosion, i.e. rain drop impact in the fan (R1). While microscopic traces of rain erosion can be detected on titanium blades, there does not seem to be any acute risk of damage. Noticeable damage is possible on the surfaces of coated parts or those made from fiber-reinforced plastics. In the high-pressure compressor and combustion chamber, the same damage can occur as with hail ingestion (R2 and R3), usually in combination with hail, since rain is more likely to be directed through the bypass duct away from the high-pressure section.