Flight Literacy

Flight Training Educational Materials

Weight-Shift Control Aircraft Flight

Preflight Inspection (Part One)

Filed Under: WSC Preflight and Ground Operations

Each aircraft must have a routine preflight inspection before flight. Use a written checklist during preflight and ground operations to maintain an established procedure. [Figure 5-40] A written checklist is required so nothing is forgotten. Ground checklists include preflight preparation, preflight inspection, occupant preflight brief, flight deck management, startup, taxi, before takeoff, and aircraft shutdown. Be smart and follow the regulations—use a written checklist. All checklists should be secured so they do not fly out of the flight deck in flight and hit the propeller. Securing with zippered pockets and having lanyards for the checklists is recommended. Manufacturers of Special Light-Sport Aircraft (S-LSA) have checklists that come with the aircraft. Pilots with an experimental aircraft may need to develop their own.

Figure 5-40. Laminated index cards are handy for checklists, and sized to fit into the flight suit zippered pocket.
Figure 5-40. Laminated index cards are handy for checklists, and sized to fit into the flight suit zippered pocket.

Certificates and Documents

The first step of preflight inspection is to ensure the aircraft is legally airworthy which is determined in part, by the following certificates and documents:

  • Airworthiness certificate
  • Registration certificate
  • Operating limitations, which may be in the form of an FAA-approved AFM/POH, placards, instrument markings, or any combination thereof
  • Weight and balance

ARROW is the acronym commonly used to remember these items. The PIC is responsible for making sure the proper documentation is on board the aircraft when operated. [Figure 5-41]

Figure 5-41. Registration and airworthiness certificates are required to be in plain view.
Figure 5-41. Registration and airworthiness certificates are required to be in plain view.

Aircraft logbooks are not required to be on board when it is operated. However, inspect the aircraft logbooks prior to flight to confirm the WSC aircraft has had all required inspections. The owner/operator must keep maintenance records for the airframe and powerplant. At a minimum, there must be an annual condition inspection within the preceding 12 calendar months. In addition, the WSC aircraft may also need a 100-hour inspection in accordance with 14 CFR part 91 if it is used for hire (e.g., for training operations). [Figure 5-42] If a transponder system is used, the transponder must be inspected within each preceding 24 calendar months.

Figure 5-42. Maintenance requirements for WSC LSA.
Figure 5-42. Maintenance requirements for WSC LSA.

The pilot must have in his or her possession a Sport pilot certificate for the aircraft being flown, medical eligibility, and government-issued photo identification. For a Sport Pilot Certificate, medical eligibility can be a valid United States driver’s license, which also serves as government-issued photo identification.

To fly the aircraft with Private Pilot privileges, the pilot needs a valid FAA minimum third-class medical certificate accompanied by a government-issued photo identification and Private Pilot certificate for WSC aircraft. See Chapter 1, Introduction to Weight-Shift Control, for details on specific pilot certificates and privileges.

Routine Preflight Inspection

The accomplishment of a safe flight begins with a careful and systematic routine preflight inspection to determine if the aircraft is in a condition for safe flight. The preflight inspection should be performed in accordance with a printed checklist provided by the manufacturer for the specific model of the aircraft. However, the following general areas are applicable to all WSC aircraft.

The preflight inspection begins as soon as a pilot approaches the aircraft. Since the WSC aircraft can be transported by trailer, first and foremost, look for any damage that may have occurred during takedown, loading, transit, unloading, and setup. Make note of the general appearance of the aircraft, looking for obvious discrepancies such as tires with low air pressure, structural distortion, wear points, and dripping fuel or oil leaks. All tie-downs, control locks, and chocks should be removed during the unloading process.

The pilot must be thoroughly familiar with the locations and functions of the aircraft systems, switches, and controls. Use the preflight inspection as an orientation when operating a particular model for the first time.

The actual walk-around routine preflight inspection has been used for years from the smallest general aviation airplane to the largest commercial jet. The walk-around is thorough and systematic, and should be done the same way each time an aircraft is flown. In addition to seeing the aircraft up close, it requires taking the appropriate action whenever a discrepancy is discovered. A WSC aircraft walk-around covers four main tasks:

  1. Wing inspection
  2. Carriage inspection
  3. Powerplant inspection
  4. Equipment check

Throughout the inspection, check for proper operation of systems, secure nuts/bolts/attachments/hardware, look for any signs of deterioration or deformation of any components/ systems, such as dents, signs of excessive wear, bending, tears, or misalignment of any components and/or cracks.

Each WSC aircraft should have a specific routine preflight inspection checklist, but the following can be used as an example and guideline.

Wing Inspection

Start with the nose. Inspect the nose plates and the attachment to the leading edges and keel. Ensure the nose plates are not cracked and the bolts are fastened securely. Check the wire attachments, top and bottom.

Inspect the control frame, down tubes and control bar for dents and ensure they are straight. Inspect the control frame attachment to the keel. Inspect the control bar to down tube brackets and bolts. [Figure 5-43] Inspect fore and aft flying wire condition, attachment to the keel, and the lower control bar corner brackets.

Figure 5-43. Inspecting the control frame brackets and flying wire components. attachments.
Figure 5-43. Inspecting the control frame brackets and flying wire components. attachments.

Inspect the left side flying wire attachment to the control bar bracket and condition of the flying wire up to the wing attachment. Examine the flying wire attachment to the leading edge and crossbar, as well as all hardware at this crossbar and leading edge junction. [Figure 5-44] Inspect the condition of the crossbar and the leading edge from the nose to the tip. Any discrepancies or tears in the leading edge fabric must lead to more detailed investigation of the leading edge spar itself.

Figure 5-44. Inspecting the flying wire attachment to the leading edge and crossbar along with all the hardware at this junction.
Figure 5-44. Inspecting the flying wire attachment to the leading edge and crossbar along with all the hardware at this junction.

Inspect the tip area, including the washout strut and general condition of the tip. If it is a double surface wing, look inside the tip and examine the inside of the wing and its components. [Figure 5-45]

Figure 5-45. Examining inside the tip of the wing to inspect all the components.
Figure 5-45. Examining inside the tip of the wing to inspect all the components.

From the tip, inspect the surface condition of the fabric. Generally, if the fabric has not been exposed to sunlight for long periods and stored properly, the wing fabric should stay in good shape.

Move along the trailing edge of the wing, inspecting the condition of the trailing edge and the tip batten attachments back to the keel. [Figure 5-46] Inspect the sail material, top and bottom, on the wing. Note that the trailing edge is vulnerable to rocks flying up from the wheels and hitting the propeller. Therefore, it is especially important to inspect the trailing edge in detail before each flight.

Figure 5-46. Inspecting the trailing edge of the wing.
Figure 5-46. Inspecting the trailing edge of the wing.

At the aft keel area in the middle of wing, inspect the kingpost and all the condition of the wires from the kingpost to ensure they are not wrapped around the trailing edge battens. [Figure 5-47] Inspect the wing tensioning hardware where the crossbar tensioning cables attach to the rear of the keel. Repeat this same sequence for the right (or opposite) side of the wing, in the reverse order. Inspect the condition of the wing attachment to the carriage, including the backup cable. [Figure 5-48]

Figure 5-47. Inspecting the kingpost, top wires, and crossbar tension hardware.
Figure 5-47. Inspecting the kingpost, top wires, and crossbar tension hardware.
Figure 5-48. Inspecting the wing attachment to the carriage.
Figure 5-48. Inspecting the wing attachment to the carriage.

Carriage Inspection

Inspect the mast from the top to the bottom and the carriage keel from the back to the front. [Figure 5-49] Check the front tube attachment and top and bottom security attachments. Check the seat security and seat attachments from the keel to the mast.

Figure 5-49. Inspecting the front keel and seat attachments to the keel.
Figure 5-49. Inspecting the front keel and seat attachments to the keel.

Check the front nose wheel for proper play, tire inflation, and secure axle bolt. Test the ground steering bar and ensure there is smooth steering range of motion. Check the front shocks, if installed, the brakes for rust and corrosion, loose nuts/bolts, alignment, cracks, signs of hydraulic fluid leakage, and hydraulic line security and abrasion, if so equipped. [Figure 5-50] Check the foot throttle for smooth operation and assure the parking brake is secured.

Figure 5-50. Checking the front wheel, tire, and front fork assembly.
Figure 5-50. Checking the front wheel, tire, and front fork assembly.

Inspect the main landing gear drag struts, attachment to the keel, and attachment to the rear wheels. Examine the rear tires for proper inflation and tread plus the wheel attachment nut for security. Check main landing gear strut, landing gear shock absorber strut, and shock absorber operation. [Figure 5-51] Inspect all landing gear strut attachments to the airframe. Inspect the other side’s rear landing gear by repeating the above procedure in reverse. Check all cowling for secure attachment and cracks. [Figure 5-52]

Figure 5-51. Checking the rear landing gear struts.
Figure 5-51. Checking the rear landing gear struts.
Figure 5-52. Checking the cowl attachment for security and cracks.
Figure 5-52. Checking the cowl attachment for security and cracks.

Powerplant Inspection

Inspect engine attachment to the carriage for security and cracks. In addition to looking at the bolts and mounts, shake the propeller, as shown in Figure 5-53, to provide a secure check of the propeller, gearbox, engine, and engine attachment to the carriage.

Figure 5-53. Checking the security of the engine to the airframe.
Figure 5-53. Checking the security of the engine to the airframe.

Fuel System

  • Inspect fuel tank attachment and condition.
  • Inspect fuel vent system, and ensure the fuel supply line is open (some WSC aircraft have fuel shut off valves outside the fuel tank).
  • Inspect fuel pickup and fuel line running up to fuel filter. While inspecting all fuel lines, jiggle all fittings and connections to ensure they are secure.
  • Inspect fuel filter and continue to follow fuel line up to fuel pump.
  • Inspect the security and condition of fuel pump.
  • Inspect fuel lines up to carburetors. [Figure 5-54]
Figure 5-54. Checking the security and condition of the fuel lines and fuel filter condition.
Figure 5-54. Checking the security and condition of the fuel lines and fuel filter condition.

Induction System

  • Inspect carburetors, including float bowl attachment and rubber bushing from carburetors into engine.
  • Inspect fuel lines from float bowls to carburetor inlet.
  • Inspect air inlet filter to ensure it is clean and secure. [Figure 5-55]
Figure 5-55. Checking the security of the air inlet filter and the security of the carburetors to the engine.
Figure 5-55. Checking the security of the air inlet filter and the security of the carburetors to the engine.

Ignition System

  • Inspect ignition system wires to spark plugs.
  • Inspect spark plug caps and wires to CDI units to ensure they are secure and fastened. [Figure 5-56]
  • Ensure ignition switches are turned off.
Figure 5-56. Checking spark plug cap security to the spark plugs.
Figure 5-56. Checking spark plug cap security to the spark plugs.

Cooling Systems

Ensure there is clear airflow for any cooling system fan or radiator. Ensure no insects or birds created an obstruction to the airflow for the engine cooling system.

Air-cooled—rotate the propeller and ensure that the cooling fan rotates also.

Water-cooled—check the coolant level to ensure there is cooling fluid in the system.

Four-stroke with additional oil coolers—ensure the oil cooler has clear airflow and that nothing is blocking it.

Exhaust Systems

Inspect exhaust attachment to engine, and EGT senders. Slightly jiggle the exhaust system to inspect the springs holding it together. All springs must be secure. Inspect the condition of exhaust system for cracks and attachment security. [Figure 5-57]

Figure 5-57. Inspecting the exhaust system by jiggling the outlet pipe and checking the springs.
Figure 5-57. Inspecting the exhaust system by jiggling the outlet pipe and checking the springs.

Propeller Gearbox

Rotate the propeller in the proper direction only and inspect blades for cracks or nicks. Listen and feel for smooth operation and engine compression while rotating the propeller. Inspect propeller attachment to the gearbox and the gearbox attachment to the engine.

Throttle System

Check all throttle controls for smooth operation and proper travel and locking. Also check choke and/or primer system for proper operation and travel.

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Wing Tuning

Filed Under: WSC Preflight and Ground Operations

Wings are designed to fly straight with a range of trim speeds determined by the manufacturer. If the wing does not fly straight or trim to the manufacturer’s specifications, it must be tuned to fly properly. Any wing adjustment can change the handling and stability characteristics of the wing. Each wing is unique and the tuning procedures are unique for each wing. It is very important to follow the specific tuning procedures in the POH/AFM for the specific wing. The following are general guidelines to understand the tuning process.

Tuning the Wing To Fly Straight

Wings may turn to the right or left (depending on which way the propeller turns) at high power settings because of the turning effect described earlier in the aerodynamics section. If it does not fly straight for cruising flight, visually examine for any asymmetric right and left features on the wing before making any adjustments. Look for symmetry in the twist angle. Inspect the leading edge for any discontinuities, bumps, or an irregular leading edge stiffener. Ensure the pockets are zippered and symmetrical on both sides. Ensure the reflex lines are clear, straight, and routed properly. Check the battens to ensure the right and left match (do not make any adjustments in the battens initially because reflex may have been added at the factory initially for tuning), and ensure the battens match the manufacturer’s batten pattern. Check the batten tension on both sides and the leading edge tension to ensure it is symmetrical. If it is a used wing just acquired, research the history of the wing to see what might have happened which would cause it to not fly straight. For new wings, contact the manufacturer for advice.

If these checks do not make the wing fly straight, then adjust the twist in the wing according to the manufacturer’s instructions. More twist on one side decreases angle of attack, produces less lift, and will drop the wing, which makes it turn in the direction where more twist was added. For example, with an unwanted left hand turn, either decrease the twist on the left hand wing (increase angle of attack at the tip) or increase the twist on the right hand wing (decrease the angle of attack at the tip).

Batten tension is one way of fixing very mild turns. Increasing the batten tension at the tips especially decreases twist and raises the wing. For normal mild turns, most wings have an adjustment at the tip where you can rotate the wing tip around the leading edge. This is the easiest and most effective wing twist adjustment. [Figure 5-39] For some models, reflex at the root can be adjusted on a side to adjust a significant turn. More reflex on a side means wing up, similar to reducing twist in a wing. As emphasized above, the POH for each manufacturer must be used for adjusting twist for wing tuning.

Figure 5-39. Left hand wing tip twist adjustment shown without sail.
Figure 5-39. Left hand wing tip twist adjustment shown without sail.

Adjusting the tension on the leading edge is another method of adjusting the wing twist. However, different wings will react differently when tension is adjusted, so the POH must be followed for a particular wing. Some manufacturers do not suggest adjusting sail tension to adjust twist, but require equal tension with other adjustments to remedy an unwanted turn. For those wings utilizing asymmetrical sail tension to adjust twist, the following information is provided. Adjusting sail tension is most effective on slower wings with lots of twist. Adjusting sail tension affects some high performance wings differently, making it necessary to consult the POH. However, on most wings, increasing sail tension at the tip increases leading edge flex, resulting in more twist.

Tuning the Wing To Fly Slower or Faster

Most wings allow the hang point attachment to move forward to increase trim speed and back to decrease trim speed. If there is a situation where the hang point is at the most forward position and the wing trims below the manufacturer recommended speed, or the trim speed is within 10 miles per hour (mph) of the stall speed, an alternate method for increasing the trim speed is needed. For this situation, the twist must be reduced symmetrically to increase the angle of attack on the tips so they provide more lift and lower the nose for proper trim.

This can be done by pulling back more on the crosstube tensioning cables which reduces the twist in the wing. However, this procedure reduces the stability of the wing and decreases the handling ability of the wing because it is stiffer. This is a common adjustment for hang gliding wings for inflight trim, however this adjustment should only be made on WSC wings as specified in the POH for a specific wing.

Raising and lowering the reflex lines affects airfoil reflex and also changes the trim speed of the wing. Lower reflex lines speed the wing up and make it less stable, raising the reflex lines slows the wing and make it more stable. Some manufactures have this as an adjustable setting which can be varied during flight, other manufactures have this adjustment where it can be made on the ground. Other manufactures do not recommend this adjustment because it can lower the certified stability of the wing.

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Rod Machado's Private Pilot Handbook -Flight Literacy recommends Rod Machado's products because he takes what is normally dry and tedious and transforms it with his characteristic humor, helping to keep you engaged and to retain the information longer. (see all of Rod Machado's Products).

Weight, Loading, and Transporting (Part Two) Setup and Takedown

Filed Under: WSC Preflight and Ground Operations

Setting Up the WSC Aircraft

Find a suitable area to set up the wing, such as grass, cement, or pavement out of the wind. Inside a large hangar is preferable since wind gusts are not a problem. If setting up outside, align the wing perpendicular to the wind. Most wings set up with the same basic procedure shown in Figures 5-11 through 5-33, but the POH should be referenced for the specific WSC aircraft.

Figure 5-11. Wing positioned for setup.
Figure 5-11. Wing positioned for setup.

Rotate the wing bag so the zipper is facing up. [Figure 5-11] Unzip the bag. When setting up the wing, pay close attention to the specific pads, where they are located, and how they are attached for each component of the wing. As shown in Figure 5-12, the padding is made specifically for the control frame between the downtubes and the control bar. If every pad is not utilized when taking it down and transporting, there will be wear on components with cosmetic and/or structural damage to the wing. The POH may specify where pads go during the setup and takedown. However, when setting up any wing it is a good idea to take pictures, draw sketches, or take notes regarding protective pad location so they can be put back in the proper location during take down.

Figure 5-12. Wing cover bag unzipped, showing unique padding around control frame corner brackets.
Figure 5-12. Wing cover bag unzipped, showing unique padding around control frame corner brackets.
Figure 5-13. Assembling control frame.
Figure 5-13. Assembling control frame.

Assemble the triangular control frame without attaching the wires to the nose. [Figure 5-13] Rotate the wing up onto its control frame. [Figure 5-14] Place the front wires near the control bar so no one walks on them, remove, and roll up the cover bag. [Figure 5-15] Release the wing tie straps that are holding the leading edges together. [Figure 5-16] Spread the wing slightly. Remove the pads from the wing keel and kingpost. Note the protective pads still on the wingtips protecting them from the ground during most of the wing set up procedure. [Figure 5-17] Continually manage the wing pads and wing tie straps by rolling the pads into the cover bag so they do not blow away. [Figure 5-18] If the kingpost is loose, insert it onto the keel to stand upright. If the kingpost is attached, swing it upright. Topless wings have no kingpost. Spread the wings as necessary to keep the kingpost straight up, [Figure 5-19] spreading them out carefully and evenly. Do not force anything. Ensure the wires are not wrapped around anything. Separate the right and left battens. Separate the straight battens (for a double surface wing) and set them to the side. Lay out the battens, longest to shortest from the root to the tip next to the pocket they go into on both sides. Note the protective pads are still on the wing tips so they are protected. [Figure 5-20] Insert the battens into the batten pockets, starting at the root and work out to the tip. [Figure 5-21] Most batten attachments are double pull. [Figure 5-22] Some manufacturers use cord or elastic, and others use a system that slips into the sail itself. See the POH for wing details. Insert battens from the root towards the tip about ¾ the way out on each side. Leave the tip battens for later. Spread the wings as far as possible. [Figure 5-23] Check to ensure all the wires are straight, not wrapped around, and clear to tension the wing. Tension the wing by pulling back on the crossbar tensioning cable and pulling the crossbar back into position. This may require significant effort for some wings. Secure the tensioning cable to the back of the keel. [Figure 5-24] If the keel does not extend out, then support the aft end of the keel to lift the tips off of the ground. [Figure 5-25] Move to the front and secure the front control frame flying wires to the underside nose attachment. [Figure 5-26] Remove the tip bag protectors and install the tip battens, continuing to move from the root to the tips on each side. Insert the washout strut into the leading edge. Each manufacturer has its own washout strut systems and tip battens. Some manufacturers have no washout struts. Refer to the POH for wing specifics. [Figure 5-27]

Figure 5-14. Rotating the wing onto its control frame.
Figure 5-14. Rotating the wing onto its control frame.
Figure 5-15. Placing the front wires at the control frame.
Figure 5-15. Placing the front wires at the control frame.
Figure 5-16. Removing the straps holding the two wings together.
Figure 5-16. Removing the straps holding the two wings together.
Figure 5-17. Wings spread slightly to raise the kingpost.
Figure 5-17. Wings spread slightly to raise the kingpost.
Figure 5-18. Pads and wing tie straps neatly rolled into wing cover bag.
Figure 5-18. Pads and wing tie straps neatly rolled into wing cover bag.
Figure 5-19. Raising the kingpost and spreading the wings as needed to keep the kingpost upright.
Figure 5-19. Raising the kingpost and spreading the wings as needed to keep the kingpost upright.
Figure 5-20. Wings spread and battens organized to insert into wings. Note small stepladder holding up keel.
Figure 5-20. Wings spread and battens organized to insert into wings. Note small stepladder holding up keel.
Figure 5-21. Inserting batten into batten pocket.
Figure 5-21. Inserting batten into batten pocket.
Figure 5-22. Attaching double pull batten (inset). Batten secured into batten pocket.
Figure 5-22. Attaching double pull batten (inset). Batten secured into batten pocket.
Figure 5-23. Wing ready to tension.
Figure 5-23. Wing ready to tension.
Figure 5-24. Attaching the tensioning cables to the back of the wing to complete the wing tensioning step.
Figure 5-24. Attaching the tensioning cables to the back of the wing to complete the wing tensioning step.
Figure 5-25. The wing tensioned.
Figure 5-25. The wing tensioned.
Figure 5-26. Attaching the front flying wires to the nose attachment.
Figure 5-26. Attaching the front flying wires to the nose attachment.
Figure 5-27. Installing the wing tip battens.
Figure 5-27. Installing the wing tip battens.

Insert bottom battens for a double surface. If inside a hangar where there is no wind, this can be done by putting the nose down, making it easier to install the lower battens. [Figure 5-28] If not already accomplished, lift up on the back of the keel and put the wing on its nose. Lower the undercarriage mast and line up the undercarriage behind the wing exactly in the middle. Move the undercarriage forward and attach the mast to the proper hang point location on the wing keel. Consult the POH for the proper hang point for desired trim, speed, and loading at this time. Attach the backup cable at this time also. [Figure 5-29]

Figure 5-28. Installing the lower surface battens.
Figure 5-28. Installing the lower surface battens.
Figure 5-29. Attaching the mast to the wing after checking the POH for the proper hang point location.
Figure 5-29. Attaching the mast to the wing after checking the POH for the proper hang point location.

Lift up the nose and let the carriage roll backward until the wing is level and the control bar is in front of the front wheel of the carriage. Engage the parking brake and chock the back of the carriage wheels. Ensure everything in the flight deck is free and clear so the wing can be lifted freely into position. [Figure 5-30] Lift the wing into position and lock the carriage mast. This position is unique to each manufacturer as some masts hinge above the flight deck. Refer to the POH for details on a specific aircraft. [Figure 5-31] Install the carriage front tube. Secure the control bar to the front tube with a bungee. [Figure 5-32] Attach any fairing or seats as required. [Figure 5-33]

Figure 5-30. Wing in position and carriage chocked to lift the wing.
Figure 5-30. Wing in position and carriage chocked to lift the wing.
Figure 5-31. Lifting the wing up into position.
Figure 5-31. Lifting the wing up into position.
Figure 5-32. Attaching the front tube.
Figure 5-32. Attaching the front tube.
Figure 5-33. Installing the seats.
Figure 5-33. Installing the seats.

An alternate method of setting up the wing is to do so on the ground. This is not preferable because the sail is susceptible to getting dirty. However, this method could be used for setting up wings if it is windy or if recommended by a particular manufacturer. The ground method steps are the same as those in the assembly procedure except after the control bar is assembled, the wing is rolled over so the control frame is under the wing. The wing is assembled as if it were standing on its control frame. After the wing is tensioned, the nose is lifted, the control frame pulled forward, and the nose wire secured. This is not a common practice, and the POH should be reviewed for details on this method if it is allowed by the manufacturer.

Taking Down the WSC Aircraft

Find a suitable area to take down the wing, preferably grass, cement, or pavement out of the wind. The best place is in a large hangar so no wind gusts can affect the takedown. If outside, align the wing perpendicular to the wind.

It is important to note that during the take down process, all protective pads must be put in the proper place so that no hardware can rub against the sail or frame during transport. The POH should specify what pads go where. Overall, pad everything along the wing keel plus the kingpost to prevent cosmetic and/or structural damage occurring during transport.

Taking down a WSC aircraft is done in the reverse order of assembly with the following additional steps provided to get the wing neatly packed and organized into the bag. After the wing is detensioned and the battens have been removed from the wing, keep the right and left battens separate for easier sorting during the next assembly.

Figure 5-34. Padding the keel and kingpost with the right hand sail over the top of the leading edge.
Figure 5-34. Padding the keel and kingpost with the right hand sail over the top of the leading edge.
Figure 5-35. Left hand side rolled up and secured with wing tie. Rolling right hand sail which will also be secured with wing tie.
Figure 5-35. Left hand side rolled up and secured with wing tie. Rolling right hand sail which will also be secured with wing tie.

Carefully bring the wings in towards the keel and pull the sail material out and over the top of the leading edges. Lower the kingpost and pad it top and bottom. This is also the time to pad the area underneath where the control frame is attached to the keel and where the wires are attached to the rear of the keel. [Figure 5-34] Bring the leading edges to the keel and keep the sail pulled out over the top of the leading edge, roll it up, and tuck the sail into the leading edge stiffener. Fasten around the leading edge with sail ties. [Figure 5-35] It is best to take one sail tie and secure the two leading edges together so it fits into the bag. [Figure 5-36] Continue with the reverse order (bag on, flip wing over, and disassemble control frame at downtube and control bar junction). After the control frame is disassembled and laid flat along the wing as shown, the wires are not organized. [Figure 5-37] Pull the cables forward towards the nose and organize them so they are straight. Install the protective control frame pads and carefully zip up the bag while tucking everything in so there is no stress on the zipper. [Figure 5-38]

Figure 5-36. Securing both leading edges together so the wing easily fits into the bag.
Figure 5-36. Securing both leading edges together so the wing easily fits into the bag.
Figure 5-37. Control bar folded down along leading edges but wires not yet organized.
Figure 5-37. Control bar folded down along leading edges but wires not yet organized.
Figure 5-38. Carefully zipping bag with minimum stress by tucking in wires and organizing components.
Figure 5-38. Carefully zipping bag with minimum stress by tucking in wires and organizing components.

Flight Literacy Recommends

Rod Machado's Private Pilot Handbook -Flight Literacy recommends Rod Machado's products because he takes what is normally dry and tedious and transforms it with his characteristic humor, helping to keep you engaged and to retain the information longer. (see all of Rod Machado's Products).

Weight, Loading, and Transporting (Part One)

Filed Under: WSC Preflight and Ground Operations

Weight and Loading

Weight and loading must be considered before each flight. Do not exceed the maximum gross weight as specified in the pilot’s operating handbook (POH). The balance of the pilot, passenger, fuel, and baggage is usually not an issue, but must be reviewed in the POH for the specific make/model since some may have balance limitations. The fore and aft carriage attachment to the wing hang point must be within the limits as specified in the POH for weight and loading of the carriage. Always follow the POH performance limitations.

Transporting

It is best to keep the WSC aircraft in an enclosed hangar, but trailers may be used to transport, store, and retrieve the WSC carriage. If the trailer is large enough, the wing can also fit inside the trailer. If not, then it must fit on top of a trailer, truck, or recreational vehicle (RV). [Figure 5-9]

Figure 5-9. Enclosed trailer containing carriage and wing on top of RV.
Figure 5-9. Enclosed trailer containing carriage and wing on top of RV.

Enclosed trailers are preferred so the carriage is protected from the outside elements such as dust, rain, mud, road debris, and the interested person who may want to tinker with the carriage. The WSC carriage should fit snuggly without being forced, be guarded against chafing, and well-secured within any trailer. It is best to utilize hardpoints on the carriage frame and secure each wheel so the carriage cannot move fore and aft during transport. This is best accomplished by first tying the front wheel from the axles, the fork, or a hard point on the frame with a slight forward pull. Then, secure the rear wheels from the axles or a hard point on the frame with a slight rearward pull. Guides on the side of the wheels and wheel chocks in front and back of each wheel are additionally helpful to secure the carriage on any trailer.

The wing must have ample padding and should have at least three support points where it rests for transport. Transporting the wing properly is of critical importance because the wing resting on any hard surface can wear a hole in the sail and cause structural damage to the tubing. The greatest wear and tear on a wing can occur during transportation. Each support point should have equal pressure—no single point taking most of the load. The wing should be tied down at each attachment point to secure it, but not tight enough to damage the wing. Wide straps are better than thin ropes because the greater width creates less concentrated pressure on the wing at each tie-down point.

Once the loading of the carriage and wing is complete [Figure 5-9], take a short drive, stop, and check for rubbing or chafing of components.

Prior to taking the tow vehicle and trailer on the road, inspect the tires for proper inflation and adequate tread. Ensure all lights are operable, the hitch is free moving and well lubricated, the tow vehicle attachment is rated for the weight of the trailer, and the vehicle and trailer brakes are operable. Avoid towing with too much or too little tongue weight, which causes the trailer to fishtail at certain speeds, possibly rendering it uncontrollable.

Figure 5-10. Crane used for one person to lift 110-pound wing on top of RV for transport.
Figure 5-10. Crane used for one person to lift 110-pound wing on top of RV for transport.

Be extremely cautious when unloading the wing and carriage. This is best done with two people since the wing usually weighs more than 100 pounds [Figure 5-10] and the carriage usually must roll down some incline to get from the trailer to the ground. Some carriages may be tail heavy without the wing, and caution must be exercised, especially moving up and down ramps. Check propeller clearance on the ground when transitioning onto or off of a ramp and propeller clearance going into and out of an enclosed trailer. If the carriage is transported in an open trailer, it should be covered and the propeller secured so it does not rotate/windmill during transport.

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Weather (Weight-Shift Control Aircraft)

Filed Under: WSC Preflight and Ground Operations

Weather is a determining factor for all flight operations. Before any flight is considered, pilots should obtain regional and local information to first determine if the predicted weather for the planned flight is safe.

Regional Weather

Understanding the overall weather in the region being flown provides an overview of conditions and how they can change during flight. Fronts, pressure systems, isobars, and the jet stream determine the weather. There are a number of information resources from which to find the regional view of weather systems, observed and predicted. Surface analysis charts show these regional systems, which are common on weather internet sites and TV broadcasts. [Figure 5-4] Review the Pilot’s Handbook of Aeronautical Knowledge for a comprehensive understanding of weather theory, reports, forecasts, and charts for weather concepts covered throughout this weather section.

Figure 5-4. Standard surface analysis showing fronts, pressure systems, and isobars (top) and composite surface analysis which adds radar and infrared satellite to show cloud cover (bottom).
Figure 5-4. Standard surface analysis showing fronts, pressure systems, and isobars (top) and composite surface analysis which adds radar and infrared satellite to show cloud cover (bottom).

There are many sources for obtaining a weather briefing, such as www.aviationweather.gov, www.nws.noaa.gov, 1- 800-WX-BRIEF, and a variety of internet sites that specialize in local and regional weather.

Local Conditions

In gathering weather information for a flight, obtain current and forecast conditions where flying, as well as alternate airports in case landing at the intended destination is not possible. These conditions should include wind (surface and winds aloft), moisture, stability, and pressure.

Surface wind predictions and observations can be looked at with a number of internet resources. The National Weather Aviation service provides observations (METAR) and forecasts (TAF) for areas with weather reporting capabilities.

Winds aloft are forecast winds at higher altitudes than the surface for locations throughout the United States. Refer to the Pilot’s Handbook of Aeronautical Knowledge for an understanding of the winds and temperatures aloft tables. Winds aloft, too, are important for flight planning and safety.

A typical situation during morning hours is cold air from the night settling, creating calm winds at the surface with the winds aloft (300 to 3,000 feet) at 30 knots. As the surface begins to warm from the sun, the cold surface air starts to warm and rise, allowing the high winds from above to mix and lower to the surface. The wind sheer area in between the high winds above and calm winds below is usually turbulent and can overwhelm aircraft or pilot capabilities. Therefore, it is a dangerous practice to look only at the windsock for surface winds when there could be strong winds above. Winds aloft must be evaluated for safe flight. [Figure 5-5]

Figure 5-5. Typical morning inversion layer—calm cold air is below; high winds are above.
Figure 5-5. Typical morning inversion layer—calm cold air is below; high winds are above.

During initial solo flights, the wind should be relatively calm to fly safely. As experience is gained, pilot wind limitations can be increased. It is not until the pilot has had dual training in crosswinds, bumpy conditions, and significant pilot in command (PIC) time soloing in mild conditions that pilot wind conditions should approach the aircraft limitations. A safe pilot understands aircraft and personal limitations.

Moisture in the air has a significant effect on weather. If the relative humidity is high, the chance of clouds forming at lower altitudes is more likely. Clouds forming at lower altitudes create visibility problems that can create Instrument Meteorological Conditions (IMC) in which the visibility is below that required for safe flight. The temperature-dew point spread is the basis for determining at what altitude moisture condenses and clouds form. It is important to be particularly watchful for low visibilities when the air and dew point temperatures are within a spread of three to four degrees.

The closer these temperatures are to each other, the greater the chance for fog or clouds forming with reduced visibility conditions. Consider a scenario where the destination airport currently has a temperature-dew point spread of 4 °F, and it is evening when the atmosphere is cooling down. Since the temperature-dew point convergence rate is 4.4° for every thousand feet, the clouds/ceiling would be about 1,000 feet above ground level (AGL). Since it is cooling down, the temperature-dew point spread is decreasing, lowering the cloud level. Therefore, the 1,000 foot AGL ceiling is lowering, creating IMC conditions that are not safe. For this scenario, the flight should not be attempted.

Air temperature and humidity directly affect the performance of the WSC wing and engine. The higher the temperature, humidity, and actual altitude of the operating field, the greater role density altitude plays in determining how much runway the WSC aircraft needs to get off the ground with the load on board, and how much climb performance is required once airborne. The WSC aircraft may have cleared the obstacle at 8 a.m. when the weather conditions were cooler with less humidity; at 1 p.m. with increased air temperature and higher humidity levels, the pilot must reevaluate the performance of that same aircraft. A full understanding of density altitude is necessary to be a safe WSC pilot; refer to the Pilot’s Handbook of Aeronautical Knowledge for density altitude and weight effects on performance.

The rate of temperature decrease with increased altitude determines the stability of the air. The stability of the air determines the vertical air currents that develop during the day as the area is heated by the sun. These rising vertical air currents are commonly known as thermals. Generally, stable air has mild thermals and therefore less turbulence than unstable air. Unstable air rises faster, creating greater turbulence. Highly unstable air rises rapidly and, with enough moisture, can build into thunderstorms.

Air stability is easily determined by the rate at which the temperature drops with increased altitude. A standard atmosphere is where the temperature drops 2 °C for every 1,000 foot increase. If the temperature drops less than 2 °C per thousand feet, the air is more stable with less vertical wind (thermals) developed during the day. If the temperature drops more than 2 °C per thousand feet, the air is more unstable with more powerful vertical air currents developed during the day, creating greater turbulence.

In addition to air stability, barometric pressure has a large effect on weather. Low pressure in the area, below the standard atmosphere of 29.92 “Hg, is generally rising air with dynamic and unsettled weather. High pressure above the standard atmosphere in the area is generally sinking air resulting in good weather for flying.

Many airports have automated weather systems in which pilots can call the automated weather sensor platforms that collect weather data at airports and listen to this information via radio and/or landline. Radio frequencies are on the sectional chart and the A/FD has the telephone numbers for these stations. The systems currently available are the Automated Surface Observing System (ASOS), Automated Weather Sensor System (AWSS), and Automated Weather Observation System (AWOS).

Local conditions of wind, moisture, stability, and barometric pressure are factors that should be researched before flight to make a competent decision of go or no go to fly. High winds and moist unstable air with a low barometric pressure indicate undesirable flying conditions. Light winds and dry stable air with high pressure indicate favorable flying conditions. Pilots should research and document these local conditions before flight to predict the flying conditions and compare the actual flying conditions to the predictions to learn and develop knowledge from the information resources available for flight.

In addition to weather, the National Airspace needs to be checked to ensure there are no temporary flight restrictions (TFR) for the locations planned to fly. TFRs may be found at www.tfr.faa.gov/. For a complete preflight briefing of weather and TFRs, call 1-800-WX-BRIEF.

Clouds visually tell what the air is doing, which provides valuable information for any flight. To understand the different cloud formations and the ground/air effects produced, refer to weather theory in the Pilot’s Handbook of Aeronautical Knowledge. [Figure 5-6] Cloud clearance and visibility should be maintained for the operations intended to be conducted. The chapter covering the National Airspace System (NAS) provides cloud clearance requirements in each class of airspace. A pilot should not fly when ground and flight visibility are below minimums for his or her pilot certificate and the class of airspace where operating.

Figure 5-6. Cloud diagram.
Figure 5-6. Cloud diagram.

Knowledge of mechanical turbulence and how to determine where it can occur is also important. The lee side of objects can feel turbulence from the wind up to ten times the height of the object. The stronger the wind is, the stronger the turbulence is. [Figures 5-7 and 5-8]

Figure 5-7. Turbulence created by manmade items.
Figure 5-7. Turbulence created by manmade items.
Figure 5-8. Turbulence created by natural land formations.
Figure 5-8. Turbulence created by natural land formations.

In addition to adhering to the regulations and manufacturer recommendations for weather conditions, it is important to develop a set of personal minimums such as wind limitations, time of day, and temperature-dew point spread. These minimums will evolve as a pilot gains experience and are also dependent on recency and currency in the make/model of aircraft being flown.

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Where To Fly and Preflight Actions

Filed Under: WSC Preflight and Ground Operations

Where To Fly

The weight-shift control (WSC) aircraft can be transported by trailer from one flying field to the next. For as many benefits as this provides, transporting the aircraft into unfamiliar territory also includes some safety and operational issues.

Figure 5-1. Contact the local airport management to find an acceptable location to stay at the airport.
Figure 5-1. Contact the local airport management to find an acceptable location to stay at the airport.

Contact airport management to inquire about any special arrangements to be made prior to arriving by trailer [Figure 5-1] and there may be special considerations for flying WSC aircraft with other aircraft. With smaller patterns typically used by WSC aircraft, as covered in Chapter 10, Airport Traffic Patterns, airport management may want a pilot to operate over sparsely populated areas rather than the normal airplane patterns over congested areas because of the unique noise of the WSC aircraft. [Figure 5-2] Check the Airport/Facility Directory (A/FD) all required airport information per Title 14 of the Code of federal Regulations (14 CFR) part 91 section 103, Preflight information. Some operation examples are traffic pattern information, noise abatement procedures, no fly zones surrounding the airport, and special accommodations that may need to be arranged for WSC aircraft.

Figure 5-2. Contact local airport management to determine best operation for the aircraft and its type of operation.
Figure 5-2. Contact local airport management to determine best operation for the aircraft and its type of operation.

Because of the wide range of flying characteristics of the WSC aircraft, inform local pilots about some of the incidentals of the specific WSC aircraft (e.g., flying low and slow for certain configurations). The more non-WSC aircraft pilots know about WSC flight characteristics and intentions, the better they understand how to cooperate in flight. Sharing the same airspace with various aircraft categories requires pilots to know and understand the rules and understand the flight characteristics and performance limitations of the different aircraft.

For operations at nonaircraft fields, special considerations must be evaluated. Permission is necessary to use private property as an airstrip. Locate the area on an aeronautical sectional chart to check for possible airspace violations or unusual hazards that could arise by not knowing the terrain or location. Avoid loitering around residential structures and animal enclosures because of the slow flight characteristics of WSC aircraft and distinct engine noise.

While selecting a takeoff position, make certain the approach and takeoff paths are clear of other aircraft. Fences, power lines, trees, buildings, and other obstacles should not be in the immediate flightpath unless the pilot is certain he or she is able to safely clear them during takeoff and landing operations.

Walk the entire length of the intended takeoff and landing area prior to departure. [Figure 5-3] Look for holes, muddy spots, rocks, dips in the terrain, high grass, and other objects that can cause problems during takeoff and landing. Physically mark areas of concern with paint, flags, or cones. Uneven ground, mud, potholes, or items in fields such as rocks might not be visible from the air. Plowed rows and vegetation are larger than they appear from the air. Unfamiliar fields can make suitable landing areas for emergencies, but should not be used as intended landing areas. Extreme caution must be exercised when operating from a new field or area for the first time.

Figure 5-3. Fields that look like good landing areas from the air may actually be hazardous.
Figure 5-3. Fields that look like good landing areas from the air may actually be hazardous.

Preflight Actions

A pilot must become familiar with all available information concerning the flight, including runway lengths at airport of intended use, takeoff and landing distance accounting for airport elevation and runway slope, aircraft gross weight, wind, and temperature. For a cross-country flight not in the vicinity of the takeoff/departure airport, information must include weather reports and forecasts, fuel requirements, and alternatives available if the planned flight cannot be completed.

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Starting, Oil, and Engine Cooling Systems

Filed Under: WSC Powerplants

Starting System

Most small aircraft use a direct-cranking electric starter system. This system consists of a source of electricity, wiring, switches, and solenoids to operate the starter and a starter motor. The starter engages the aircraft flywheel or gearbox, rotating the engine at a speed that allows the engine to start and maintain operation.

Electrical power for starting is usually supplied by an on-board battery. When the battery switch is turned ON, electricity is supplied to the main power bus through the battery solenoid. Both the starter and the starter switch draw current from the main bus, but the starter will not operate until the starting solenoid is energized by the starter switch being turned to the “start” position. When the starter switch is released from the “start” position, the solenoid removes power from the starter motor. The starter motor is protected from being driven by the engine through a clutch in the starter drive that allows the engine to run faster than the starter motor.

Oil Systems

In a four-stroke engine, the engine oil system performs several important functions, including:

  • Lubricating the engine’s moving parts.
  • Cooling the engine by reducing friction.
  • Removing heat from the cylinders.
  • Providing a seal between the cylinder walls and pistons.
  • Carrying away contaminants.

Four-stroke engines use either a wet sump or dry sump oil system. Refer to the Pilot’s Handbook of Aeronautical Knowledge for more information on four-stroke oil systems.

Engine Cooling Systems

The burning fuel within the cylinders produces intense heat, most of which is expelled through the exhaust system. Much of the remaining heat, however, must be removed, or at least dissipated, to prevent the engine from overheating.

While the oil system in a four-stroke engine and the fuel-oil mix in a two-stroke engine is vital to the internal cooling of the engine, an additional method of cooling is necessary for the engine’s external surface. WSC engines operate with either air-cooled or liquid-cooled systems.

Many WSC aircraft are equipped with a cylinder head temperature (CHT) gauge. This instrument indicates a direct and immediate cylinder temperature change. This instrument is calibrated in degrees Celsius or Fahrenheit. Proper CHT ranges can be found in the POH/AFM/AOI for that machine. [Figure 4-20]

Figure 4-20. Cylinder head temperature probe (yellow wire) is under spark plug.
Figure 4-20. Cylinder head temperature probe (yellow wire) is under spark plug.

Air cooling is accomplished by air being pulled into the engine shroud by a cooling fan. Baffles route this air over fins attached to the engine cylinders where the air absorbs the engine heat. Expulsion of the hot air takes place through one or more openings in the shroud. If cylinder head temperatures rise too much in an air-cooled engine, it is because of lubrication problems, cooling fan drive belt damage or wear, or air blockage in the cooling fins by a bird or insect nest. [Figure 4-1]

Figure 4-1. Two-stroke air-cooled engine.
Figure 4-1. Two-stroke air-cooled engine.

Liquid cooling systems pump coolant through jackets in the cylinders and head. The heated liquid is then routed to a radiator where the heat is radiated to the atmosphere. The cooled liquid is then returned to the engine. If the radiator is mounted close to the propeller, the propeller can constantly move air across the radiator and keep the engine cool even when the WSC is not moving. [Figure 4-21] Radiators mounted away from the propeller make it more difficult for the radiator to cool the engine unless the WSC is moving. [Figure 4-22]

Figure 4-21. Cooling radiators—oil cooler is on top and water cooler is on bottom.
Figure 4-21. Cooling radiators—oil cooler is on top and water cooler is on bottom.

Breaking in an engine through ground runs on a hot day is when radiator placement is most critical. Liquid-cooled engines can overheat for a number of reasons, such as coolant not at proper levels, a leak, failed water pump, or a blockage of the radiator.

Figure 4-22. Side-mounted water cooler radiators integral with cowl.
Figure 4-22. Side-mounted water cooler radiators integral with cowl.

Operating an engine above its maximum design temperature can cause a loss of power and detonation. It will also lead to serious permanent damage, such as scoring the cylinder walls and damaging the pistons and rings. Monitor the engine temperature instruments to avoid high operating temperature. Operating the engine lower than its designed temperature range can cause piston seizure and scarring on the cylinder walls. This happens most often in liquid-cooled WSC aircraft in cold weather where large radiators designed for summer flying may need to be partially blocked off.

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WSC Fuel Systems (Part Two)

Filed Under: WSC Powerplants

Fuel Contamination

Clean fuel is imperative for the safe operation of a WSC aircraft. Of the accidents attributed to powerplant failure from fuel contamination, most have been traced to:

  • Failure to remove contamination from the fuel system during preflight.
  • Servicing aircraft with improperly filtered fuel from small tanks or drums.
  • Storing aircraft with partially filled fuel tanks.
  • Lack of proper maintenance.

Rust is common in metal fuel containers and is a common fuel contaminant. Metal fuel tanks should be filled after each flight, or at least after the last flight of the day to prevent moisture condensation within the tank.

Another way to prevent fuel contamination is to avoid refueling from cans and drums. Use a water filtering funnel or a funnel with a chamois skin when refueling from cans or drums. However, the use of a chamois will not always ensure decontaminated fuel. Worn out chamois will not filter water; neither will a new, clean chamois that is already water-wet or damp. Most imitation chamois skins will not filter water.

Bad Gasoline

Letting fuel sit for weeks without using it will cause it to go bad. Even if gas does not go bad, it will often lose octane with time. For premixed gasoline and two-stroke oil, there is another set of problems. Fuel and oil are normally mixed at a 50:1 ratio. If premixed gas sits in a plastic container for a while, the gas will evaporate leaving a richer oil mixture in the container. In any case, fresh gas should be used when possible.

Refueling Procedures

Never mix oil and fuel in an enclosed area. Not only are the fumes irritating, but with the right fuel/air mixture can cause an explosion. Do all oil and gas mixing outside. Refueling from fuel cans should also be done outside. Never smoke while refueling. Be careful when refueling an aircraft that has just landed. There is danger of spilling fuel on a hot engine component, particularly an exhaust system component. Refueling should be done using only safety-approved fuel containers marked with the type of fuel stored in them. Confusing premixed fuel and fuel that has no oil in it can be disastrous.

Metal Versus Plastic Fuel Containers

There are advantages to using both metal and plastic containers. Metal cans will not allow the sun’s ultraviolet rays in to harm the fuel. It also will not develop static charges that a plastic container develops. However, a metal can is more prone to sweating when going from cool to warm temperatures on humid days. Metal cans and gas tanks are best kept either empty or full of fuel to leave no room for moist air.

Plastic fuel containers are easy to handle, inexpensive, available at discount stores, and do not scratch the finish on airframes. Plastic cans also do not sweat, and do not need to be stored topped off. However, fuel does deteriorate a little faster in plastic. Also, plastic containers can get charged with static electricity while sliding around in the bed of a pickup truck, especially if the truck has a plastic bed liner. [Figure 4-19]

Figure 4-19. With these translucent containers, it can be noted that the left hand container is just auto fuel and the right hand container shows the auto fuel is premixed with oil for a two-stroke engine.
Figure 4-19. With these translucent containers, it can be noted that the left hand container is just auto fuel and the right hand container shows the auto fuel is premixed with oil for a two-stroke engine.

Many states now have laws prohibiting people from filling plastic containers unless first placed on the ground. Static electricity can also be formed by the friction of air passing over the surfaces of a WSC aircraft in flight and by the flow of fuel through the hose and nozzle during refueling, if fueling at a pump. Nylon, Dacron, and wool clothing are especially prone to accumulate and discharge static electricity from the person to the funnel or nozzle. To guard against the possibility of static electricity igniting fuel fumes, a ground wire should be attached to the aircraft before the fuel cap is removed from the tank. The refueling nozzle should then be grounded to the aircraft before refueling is begun and should remain grounded throughout the refueling process. The passage of fuel through a chamois increases the charge of static electricity and the danger of sparks.

The aircraft must be properly grounded and the nozzle, chamois filter, and funnel bonded to the aircraft. If a can is used, it should be connected to either the grounding post or the funnel. Cell phones should not be used while refueling due to possible fire risks.

Mixing Two-Stroke Oil and Fuel

Two-stroke engines require special two-stroke oil to be mixed into the fuel before entering the engine to provide lubrication. In some engines, an oil injection pump is used to deliver the exact amount of oil into the intake of the engine depending on the throttle setting. An advantage of an oil injection system is that pilots do not need to premix any oil into the fuel. However, an important preflight check is to ensure the two-stroke oil reservoir is properly filled.

If a two-stroke engine does not have an oil injection system, it is critical to mix the oil with the fuel before it is put into the tank. Just pouring oil into the fuel tank does not allow the oil to mix with the gas, and makes it difficult to measure the proper amount of oil for mixing.

To mix two-stroke oil:

  • Find a clean, approved container. Pour some gas into it to help pre-dilute the two-stroke oil.
  • Pour in a known amount of two-stroke oil into the container. Oil should be approved for air-cooled engines at 50:1 mixing ratio (check the engine manufacturer for proper fuel to oil ratio for the WSC aircraft). Use a measuring cup if necessary. Shake the oil-gas mixture to dilute the oil with gasoline.
  • Add gasoline until the 50:1 ratio is reached. If using a water separating funnel, ensure the funnel is grounded or at least in contact with the fuel container.
  • Put the cap on the fuel can and shake the gasoline and oil mixture thoroughly.

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WSC Fuel Systems (Part One)

Filed Under: WSC Powerplants

The fuel system is designed to provide an uninterrupted flow of clean fuel from the fuel tank to the engine. See Chapter 3, Components and Systems, for more information on fuel tanks. See earlier section in this chapter for specifics on fuel injection systems. The fuel must be available to the engine under all conditions of engine power, altitude, attitude, and during all approved flight maneuvers. [Figure 4-17]

Figure 4-17. Typical Carburetor Fuel System.
Figure 4-17. Typical Carburetor Fuel System.

Fuel Pumps

WSC aircraft with carburetors have engine-driven fuel pump systems. A diaphragm pump is the primary pump in the fuel system for two-stroke engines. Air pulses in the crankcase actuate a diaphragm and provide fuel under pressure to the carburetor. Four-stroke engines have a mechanical pump driven directly off the engine.

Sometimes an electric auxiliary pump is provided for use in engine starting and in the event the engine pump fails. The auxiliary pump, also known as a boost pump, provides added reliability to the fuel system. The electric auxiliary pump is controlled by a switch in the flight deck.

Fuel Plunger Primer

The optional fuel plunger primer is used to draw fuel from the tanks to supply it directly into the engine prior to starting. This is particularly helpful during cold weather when engines are hard to start because there is not enough heat available to vaporize the fuel in the carburetor. For some aircraft, it is the only way to deliver fuel to the engine when first starting. After the engine starts and is running, the fuel pump pushes fuel to the carburetors and begins normal fuel delivery. To avoid overpriming, read the priming instructions in the POH.

Choke

A choke or fuel enriching system is an alternate method to provide additional fuel to the engine for initial cold starting. Actuating the choke control allows more fuel to flow into the carburetor.

Fuel Bulb Primer

The fuel bulb primer is manually actuated by squeezing the bulb to draw fuel from the fuel tanks. This charges the fuel lines and carburetor float bowls before starting the engine the first time on a given day. After the engine starts, the fuel pump is able to deliver the fuel to the fuel bowls. An electric auxiliary fuel pump can also be used to charge the fuel lines and carburetor fuel bowls before starting. This auxiliary fuel pump is also used as a backup pump of the engine-driven fuel pump fails.

Fuel Gauges

The fuel quantity gauge indicates the amount of fuel measured by a sensing unit in each fuel tank and is displayed in gallons. Do not depend solely on the accuracy of the fuel quantity gauge. Always visually check the fuel level in the tank during the preflight inspection, and then compare it with the corresponding fuel quantity indication. It is also important to track inflight fuel consumption. Be sure to consult the POH and know the approximate consumption rate to ensure sufficient fuel for flight. If an auxiliary electric fuel pump is installed in the fuel system, a fuel pressure gauge is sometimes included. This gauge indicates the pressure in the fuel lines. The normal operating pressure can be found in the POH.

Fuel Filter

After leaving the fuel tank, the fuel passes through a filter before it enters the fuel pump or carburetor. This filter removes sediments that might be in the fuel. [Figure 4-18]

Figure 4-18. Fuel system showing fuel filter to fuel pump to carburetor float bowls.
Figure 4-18. Fuel system showing fuel filter to fuel pump to carburetor float bowls.

Fuel

Aviation gasoline (AVGAS) is identified by an octane or performance number (grade) which designates the antiknock value or knock resistance of the fuel mixture in the engine cylinder. The higher the grade of gasoline, the more pressure the fuel can withstand without detonating. Lower grades of fuel are used in lower compression engines because these fuels ignite at a lower temperature. Higher grades are used in higher compression engines, because they must ignite at higher temperatures but not prematurely. If the proper grade of fuel is not available, use the next higher grade as a substitute. Never use a lower grade. This can cause the cylinder head temperature to exceed its normal operating range, which may result in detonation. Unfortunately, AVGAS 100 Low Lead (LL) may not be recommended by two-stroke engine manufacturers and may not be preferred by the four-stroke manufactures. Even though the “LL” stands for low lead, 100LL contains more lead than the old leaded gas dispensed at automotive filling stations. The lead in the fuel leaves deposits in the piston ring grooves, freezing the rings in position and reducing engine performance. Spark plugs are also very susceptible to lead fouling. This is especially true in two-stroke engines that use cooler ignition temperatures than standard aircraft engines.

AVGAS does have some advantages. It degrades slower than auto gas, maintaining its efficiency for a full 3 months. AVGAS 100LL has no seasonal or regional variations and is manufactured according to a standardized “recipe” worldwide. If the airport has only 100LL available, it is permissible, absent any limitations of the engine manufacturer, to mix 100LL and auto gasoline for use in two-stroke engines. A 50–50 ratio will boost the octane rating and limit the amount of lead available for fouling. Generally speaking, this is a reasonable compromise when the proper auto gas octane is not available.

Manufacturers of two-stroke engines and four-stroke engines used on WSC aircraft typically recommend the use of 89 octane minimum auto fuel for their engines. Additives are put into auto gas primarily to reduce harmful emissions rather than boost performance. The additives are supposed to be listed at the pump, but the accuracy of this posting should be questioned.

Methanol alcohol has corrosive properties and can damage engines. Engine manufacturers do not recommend more than five percent methanol in fuel. Consult the POH for specifics on an engine.

Ethanol alcohol is less corrosive than methanol. However, it attracts water and is not as economical as gasoline. Ethanol does not get very good fuel economy. Avoid fuels with any more than 10 percent of ethanol.

Consult the POH for specifics on an engine. Manufacturers provide specific recommendations for the percentage of alcohol in fuel. The posting on the pump may not be accurate and alcohol content can vary greatly between fuel brands and stations. Additionally, higher percentages of alcohol will be added to auto gas in the future.

A simple test can be conducted to measure the fuel’s alcohol content to ensure the fuel used stays within the manufacturer’s recommendations. Use a general aviation sump collector which includes graduation marks. Add water to a specific mark. Then add fuel to fill the collector up to the line for gas. Cover the top and shake it vigorously. After it settles, the water and alcohol will combine and it will look like there is now more water in the sump collector. The difference between the initial amount of water first put into the collector and the new level of combined water and alcohol equals the amount of alcohol in the fuel. Compare this amount of alcohol and the amount of fuel to determine the percentage of alcohol content in the fuel.

Methyl tertiary–butyl ether (MTBE) does not have the corrosive or water attractive properties of the previously mentioned additives and is added to fuel to improve air quality. It has been banned in several states because it is carcinogenic and has been found in groundwater. It does not attract water, but it is expensive, and found only in some of the better grade fuels.

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Ignition System and Combustion

Filed Under: WSC Powerplants

Ignition System

The typical ignition system on WSC aircraft provides the spark that ignites the fuel/air mixture in the cylinders and is made up of magneto/generators, control boxes, spark plugs, high-voltage leads, and the ignition switch. For most LSA engines designed specifically for aircraft, a magneto/ generator uses a permanent magnet to generate an electric current independent of the aircraft’s electrical system, which might include a battery. The aircraft electrical system can fail—the battery can go dead. However, this has no effect on the ignition system.

The electricity from the ignition magneto/generator goes into the ignition control box where the correct voltage is produced and timed to fire the spark plugs at the proper time. Modern WSC aircraft use an electronic capacitance discharge system that operates without any moving parts to increase reliability and efficiency. Capacitance Digital Systems (CDI) operate similarly but they have the ability to change the timing of the spark for different rpm. Consult the POH for the particular system for each engine.

The system begins to fire when the starter is engaged and the crankshaft begins to turn. It continues to operate whenever the crankshaft is rotating. Most WSC aircraft incorporate a dual ignition system with two individual magneto/ generators, separate sets of wires, separate sets of control boxes, and separate sets of spark plugs to increase reliability of the ignition system. Each magneto/generator operates independently to fire one of the two spark plugs in each cylinder. If one of the systems fails, the other is unaffected. The engine will continue to operate normally, although a slight decrease in engine power can be expected.

The operation of the magneto/generator output to the ignition system is controlled in the flight deck by the ignition switch. Since there are two individual ignition systems, there are normally two separate ignition toggle switches or separate positions on the ignition control, as shown in Figure 4-16.

Figure 4-16. Keyed ignition system with integral starter.
Figure 4-16. Keyed ignition system with integral starter.

Identification of a malfunctioning ignition system during the pre-takeoff check is observed by the decrease in rpm that occurs when first turning off one ignition switch, turning it back on, and then turning off the other. A noticeable decrease in engine rpm is normal during this check. If the engine stops running when switching to one ignition system or if the rpm drop exceeds the allowable limit, do not fly until the problem is corrected. The cause could be fouled plugs, broken or shorted wires between the magneto/generator and spark plugs, or improperly timed firing of the plugs because of a defective control box. It should be noted that “no drop” in rpm is not normal, and in that instance, the aircraft should not be flown. Following engine shutdown, keep the ignition switches in the OFF position. Even with the battery and master switches OFF, the engine can fire and turn over if an ignition switch is left ON and the propeller is moved because the magneto/generator requires no outside source of electrical power. The potential for serious injury in this situation is obvious.

Standard category aircraft engine systems are described in the Pilots Handbook of Aeronautical Knowledge; however, these engines are not typically used on WSC. Automobile engines or other non-aircraft engines may be used on WSC where the ignition system runs off the battery rather than a magneto/generator system. In this case if the battery system fails, the engine ignition system will fail and the engine will stop.

Combustion

During normal combustion, the fuel/air mixture burns in a very controlled and predictable manner. Although the process occurs in a fraction of a second, the mixture actually begins to burn at the point where it is ignited by the spark plugs, then burns away from the plugs until it is consumed completely. This type of combustion causes a smooth buildup of temperature and pressure and ensures that the expanding gases deliver the maximum force to the piston at exactly the right time in the power stroke.

Detonation is an uncontrolled, explosive ignition of the fuel/air mixture within the cylinder’s combustion chamber. It causes excessive temperatures and pressures which, if not corrected, can quickly lead to failure of the piston, cylinder, or valves. In less severe cases, detonation causes engine overheating, roughness, or loss of power.

Detonation is characterized by high cylinder head temperatures and is most likely to occur when operating at high power settings. Some common operational causes of detonation include:

  • Using a lower fuel grade than that specified by the aircraft manufacturer or operating the engine after it has been sitting for an extended period; after 3 weeks or as indicated by the POH, drain old fuel and replenish with fresh fuel.
  • Operating the engine at high power settings with an excessively lean mixture.
  • Extended ground operations.

Detonation may be avoided by following these basic guidelines during the various phases of ground and flight operations:

  • Make sure the proper grade of fuel is being used. Drain and refuel if the fuel is old.
  • Develop a habit of monitoring the engine instruments to verify proper operation according to procedures established by the manufacturer.

Preignition occurs when the fuel/air mixture ignites prior to the engine’s normal ignition event. Premature burning is usually caused by a residual hot spot in the combustion chamber, often created by a small carbon deposit on a spark plug, a cracked spark plug insulator, or other damage in the cylinder that causes a part to heat sufficiently to ignite the fuel/air charge. Preignition causes the engine to lose power and produces high operating temperature. As with detonation, preignition may also cause severe engine damage because the expanding gases exert excessive pressure on the piston while still on its compression stroke.

Detonation and preignition often occur simultaneously and one may cause the other. Since either condition causes high engine temperature accompanied by a decrease in engine performance, it is often difficult to distinguish between the two. Using the recommended grade of fuel and operating the engine within its proper temperature and RPM ranges reduce the chance of detonation or preignition.

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