--- title: "Flaps: Rigging, Motors and Alignment" description: "Flaps: Rigging, Motors and Alignment. Builder questions and answers from Van's Builder Technical Support." --- [Skip to content](https://support.vansaircraft.com/knowledge-base/flaps-rigging-motors-and-alignment#main-content) English Show submenu for translations ![](https://support.vansaircraft.com/hs-fs/hubfs/vans_icon_orange.png?width=58&height=48&name=vans_icon_orange.png) Open main navigation Close main navigation - English Show submenu for translations - [Contact us](mailto:info@vansaircraft.com) [Contact us](mailto:info@vansaircraft.com) How can we help you? - There are no suggestions because the search field is empty. 1. [Van's Aircraft Knowledge Base](https://support.vansaircraft.com/knowledge-base?hsLang=en) 2. [Wing](https://support.vansaircraft.com/knowledge-base/wing?hsLang=en) 3. [Flaps](https://support.vansaircraft.com/knowledge-base/wing?hsLang=en#flaps) October 5, 2026 # Flaps: Rigging, Motors and Alignment ## Builder Tech Support answers on flaps: rigging, motors and alignment This article collects Builder Technical Support answers on flaps: rigging, motors and alignment. ### Flap-to-fuselage alignment is not always symmetric Builders sometimes find that after rigging the wing for correct sweep and incidence, and using the alignment tool to set the aileron and flap in trail, the flap trailing edge does not perfectly kiss the bottom fuselage skin - it can hang noticeably low on one side. This is normal. The flap-to-fuselage interface is almost never identical side to side, and the priority is correct wing sweep, incidence, and aileron/flap streamline with the wing chord - not a perfect cosmetic match to the fuselage. Set the wing geometry first; live with whatever gap that produces at the fuselage. ### Flap trailing edge to fuselage clearance A small clearance (on the order of 1/32 inch) between the upper flap surface and the fuselage side is acceptable provided the flap moves freely through its full range without contact or rubbing. Verify with the flap fully retracted, fully extended, and through the entire travel. ### Pulled Rivet Substitution on Bottom Wing Skins For builders riveting bottom wing skins (RV-7, RV-9, RV-10, RV-14) using the recommended "L" pattern starting from the rear spar, the inboard corners can be impossible to reach with a bucking bar. Van's has approved Cherry Max blind rivets as a substitution in certain locations — notably near the flap brackets on the RV-14. For most other approved substitutions, MSP-32 series Cherry Max rivets in the correct grip length are acceptable. Important caveats: - Pulled rivet substitution is location-specific. Do not assume blanket approval. Confirm with Tech Support for the specific rivet line and rib. - Substitution is generally not approved for ribs that attach to the main spar (for example W-709 ribs on the RV-7) without case-by-case review. - Always use the correct grip length per the Cherry Max grip gauge. ### Edge distance under 1D If a trimmed flap brace or skin ends up with less than 1D edge distance at a rivet, it is generally not acceptable to proceed. The standard fix is to add a doubler or replace the part. Send photos to Builder Tech Support before riveting. For case-specific wing structure questions, contact Van's Builder Tech Support with your builder number, the plans page, photos of the affected location, and a description of how the situation occurred. ### Ordering the service kit and individual parts The SB 16-03-28 service kit is available through Van's Parts. Quote requests should include your aircraft model, serial number, and shipping address. Common related part orders include VA-101 threaded rod ends, VA-256 hex flap push rods, and pitot tubes. Place these through Parts with your customer number. ### RV-14 Flap Bracket Area The rivets nearest the flap brackets on the RV-14 lower wing skin are the most commonly asked-about substitution. MSP-32 Cherry Max in the correct grip length has been confirmed acceptable in this area. ### Common gotchas - Assuming matched-hole means "no deburring" - it doesn't - Discovering laser-cut parts in an inherited project and not knowing the SB scope - Rigging flaps before checking aileron neutral - get the order right per plans - Selling a project mid-canopy and the buyer inheriting a partially fitted bubble ### About this article The RV-14 wing kit is the highest-ticket-volume section in Builder Support. Recurring topics include spar status under the 2023 service campaign, flap skin trailing edge details, miss-shipped or duplicate parts, and laser-cut part discovery. ### Flap skins (FL-00002A/B, page 21-05) On page 21-05 step 3, builders ask whether the FL-00002A and FL-00002B flap skins get their trailing edges crimped where they overlap the trailing edge extrusions. The plans answer: - The trailing edge crimp is not always called out explicitly for every overlap on this page. Follow the plans as written. - If the skins do not lay flat on the trailing edge after dimpling, a light crimp at the overlap is acceptable to flush the joint - do not crimp aggressively. ### Related sections - Section 14-17 (wing ribs, spars, skins) - Section 18-19 (leading edge, fuel tank) - Section 20-22 (flaps, ailerons) - Current main spar service notification ### Flap pushrod orientation If you are looking at the RV-8 (or similar) plans and the inboard flap rib appears to point in opposite directions between two drawing sheets, you are reading them correctly only if you account for the part being shown from different sides. Verify against the assembled position, not the orphan drawing - the flap inboard rib should point inboard toward the fuselage with the pushrod attachment on the forward face. If still uncertain, send photos to Builder Tech Support before riveting. ### About this article The RV-8 / RV-8A wing kit is a long-running design with a stable build sequence, but Builder Support still sees consistent question patterns: rib attach hardware, flap installation, wing root intersection fairing mounting, and (for kits shipped in the affected window) laser-cut parts. ### Flap installation RV-8 flap installation questions usually involve hinge alignment and the flap-to-wing gap at the inboard and outboard ends. The flap should travel through its full deflection without rubbing on the fuselage or the aileron. Adjust the hinge brackets if needed; do not trim the flap or wing skin to clear. ### Related sections - RV-8 wing kit plans (Section 14 onward) - RV-8 flap and aileron sections - RV-8 wing root fairing detail - Laser cut parts replacement guidance ### RV-12 flaperon "extra hole" (page 18-06) The extra hole on the flaperon is for spar/rib alignment only. Match-drill to the ribs as the plans direct; do not match-drill the extra hole to the spar unless the plans explicitly call for it. ### Recurring quirks - **Flap position sensor** - calibration drift is normal over time; follow the sensor manufacturer's recalibration procedure - **Gascolator** - drain regularly; condensation accumulates faster in the RV-12 than larger RVs due to tank geometry - **F-1208 frame** and similar fuselage frames - inspect for shipping damage on receipt; report immediately - **Laser-cut parts (SB-00128)** - check whether your RV-12 wing or fuse kit is in scope and follow the bulletin ### Custom Alerts for Legacy SLSA RV-12 For an SLSA RV-12, modifying the aircraft to add a flap position sensor requires factory (Van's) approval. ELSA conversion expands what builders can modify. The G3X supports custom airspeed-based alerts (e.g., flaps-extended overspeed) once the sensor is installed. Initiate the factory approval process through Builder Support before installing the sensor. ### Flap torque tube friction RV-10 flap torque tubes installed per Section 40 should rotate smoothly. Roughly 20 in-lb to break free, or about 4-5 lb of pull at the end of the flap crank, is on the higher end but not unusual. If the outboard tube ends are rubbing the seat rib subassemblies, you can either enlarge the rib pass-through holes slightly or trim/dress the tube ends - either is acceptable as long as edge distances are preserved. ### Gap Fairings (W-921, W-924) The flap gap fairing (W-921) on the RV-9A and the aileron gap fairing (W-924) need to be riveted to the rear spar BEFORE the main ribs are riveted, because the hole pattern places the fairings under the ribs. The drawings (for example DWG 11 area F1) show the rivet callouts but the instruction sequencing is easy to miss. ### Electric flap retrofit (RV-4 manual flap to electric) The electric flap kit for RV-4 is available through the Van's store. Installation time varies significantly by builder experience and aircraft condition; an A&P should plan on a multi-day job. Contact Builder Tech Support if you need installation guidance specific to a particular airframe serial number. ### Van's Tech Q&A: Flap Motor Maintenance *Copied from Van's Aircraft Tech Q&A on 2026-10-01. Source: [Flap Motor Maintenance](https://www.vansaircraft.com/faq/flap-motor-maintenance/).* **Official PDF:** [flap\_motor.pdf](https://www.vansaircraft.com/wp-content/uploads/2019/02/flap_motor.pdf) (4 pages). If the viewer below does not load, open the PDF with this link. **Text of the PDF** *Copied word for word from the PDF. Figures, drawings and table layouts are in the PDF above.* **FLAKY FLAP MOTORS** Over the years, we’ve received the occasional report of intermittent flap motor operation. We never found a consistent problem. Sometimes it was poor wiring or a bad ground, a couple times it was a switch giving up, occasionally the problem would be with the motor itself. But problems were rare, and the flap motors in our demonstrator airplanes worked day in, day out, for years. In 2002, we switched suppliers, replacing the units we’d received from Motion Systems with a custom made unit powered by a Pittman brand motor. The new units can identified by the Van’s logo incised on the aluminum gear box housing. Not long after the change was made we got a significant number of complaints about motors failing after just a few hours. Naturally, we suspected the new motors…but as it turns out, the newer “Van’s” units were not the culprit. Instead, the problem seems to appear in one of the last batches of Motion Systems units. These we received about three years ago and they are now starting to appear in finished airplanes. The problem is usually caused by an excess of grease in the gearbox (that’s the almost cubical casting where the flap actuator tube and the motor meet at right angles). As the unit spins, hydraulic pressure pushes grease back into the motor unit and coats the windings, commutator and brushes. Grease is an insulator, and when the brushes are insulated from the commutator, yo’ motor don’ motate no mo’. Cleanliness is next to…well, it makes your flap motor work better too. You can remove the cap on the end of the motor and wipe the commutator shaft clean and your motor will work for a while. But to really solve the problem, all the grease must be removed from the flap motor or the whole cycle will just repeat. Remove the actuator unit from the aircraft and take it a clean, well-lighted bench. Assemble a small jar of clean lacquer thinner, some cotton swabs, a Phillips screwdriver, an allen key set, tweezers and some of those very thin wire ties that come on loaves of bread. If you’re of an age and have a magnifying visor, bring it. Remove the Phillips screws from the motor assembly and gently, carefully, remove the steel cap from the end of the motor. Inside is a black plastic horseshoe wrapped around a shaft. Notice the three small holes in the heel of the horseshoe. Turn over the cap and look inside – see the little index pin? See where it goes – that hole in the horseshoe? Remember that. There are several washers on the shaft. These must be reinstalled in the order they came out, so carefully note and preserve their orientation as you remove them. Slide the horseshoe gently off the motor shaft. A couple of little copper colored things are going to jump out (those are the brushes). They are retained by very thin wire springs. Now use the allen key to remove the bolts holding the motor to the gear box. Pull the motor winding/shaft assembly out of the cylindrical housing (the magnets will resist, but it will come out) and inspect it for grease and corruption. Clean the motor and brush assembly with lacquer thinner or some other clean solvent. Scoop any excess grease out of the gearbox. There should be enough to lubricate the gears, but the whole cavity does not need to be full of grease. Be careful not to disturb the tiny o-ring in the recess of the gearbox. Clean the commutator (the shiny part of the shaft that the brushes ride on) with the cotton swabs or even a bit of scotchbrite. Reassembling the motor can be more difficult than getting it apart. Begin by teasing the little springs that go behind the brushes back into their recess and tie them back with the wire ties. This may take some patience… When the springs are held back, use the tweezers to re-insert the brushes, taking care that curve worn on their contact surface matches the curve of the motor shaft. Tie the brushes back. Insert the gear end of the motor shaft back into the gearbox and check to see the baseplate is down tight. Put the cylinder/magnet back around the motor – the little notch in the rim should be on end away from the gearbox. Gently, carefully put the horseshoe back around the shaft and slide the wire ties out. The springs should force the brushes up against the commutator. Reinstall the washers. Reinstall the cap with the long Phillips screws. Find a 12-v battery and test the motor by holding the wires against the posts. Reversing the wires should make the motor run the other direction. *Figure and photo captions from the PDF:* The motor unit and screws securing the housing to the gearbox. The long phillips-head and short allen-head screws have been removed or backed off and the motor separated from the gear box. The motor cap and the horseshoe shaped brush housing have been removed. The brushes have popped out of the housing, and if you look closely, you can see the tiny spring that must be behind the brush when it is re-inserted. The springs keep the brushes up against the motor armature. The motor armature has been removed from within the motor housing and the washers removed from the motor shaft. Tucking the springs and brushes back into their cubbyholes is the toughest part of the exercise. Be careful not to bend the springs. A small spacer made of any non-magnetic scrap, that keeps the brushes pushed back will help get the “horseshoe” back on the shaft. - [Wing](https://support.vansaircraft.com/knowledge-base/wing?hsLang=en#main-content) - [Ailerons](https://support.vansaircraft.com/knowledge-base/wing?hsLang=en#ailerons) - [Spars](https://support.vansaircraft.com/knowledge-base/wing?hsLang=en#spars) - [Flaps](https://support.vansaircraft.com/knowledge-base/wing?hsLang=en#flaps) - [Fuel System](https://support.vansaircraft.com/knowledge-base/fuel-system?hsLang=en#main-content) - [Senders, Vents and Fittings](https://support.vansaircraft.com/knowledge-base/fuel-system?hsLang=en#senders-vents-and-fittings) - [Fuel Tanks](https://support.vansaircraft.com/knowledge-base/fuel-system?hsLang=en#fuel-tanks) - [Fuselage](https://support.vansaircraft.com/knowledge-base/fuselage?hsLang=en#main-content) - [Fuselage Structure](https://support.vansaircraft.com/knowledge-base/fuselage?hsLang=en#fuselage-structure) - [Canopy and Windows](https://support.vansaircraft.com/knowledge-base/fuselage?hsLang=en#canopy-and-windows) - [Finishing Kit](https://support.vansaircraft.com/knowledge-base/finishing-kit?hsLang=en#main-content) - [Wheels and Tires](https://support.vansaircraft.com/knowledge-base/finishing-kit?hsLang=en#wheels-and-tires) - [Fairings](https://support.vansaircraft.com/knowledge-base/finishing-kit?hsLang=en#fairings) - [Firewall Forward](https://support.vansaircraft.com/knowledge-base/firewall-forward?hsLang=en#main-content) - [Engine Mounts and Isolators](https://support.vansaircraft.com/knowledge-base/firewall-forward?hsLang=en#engine-mounts-and-isolators) - [Oil System](https://support.vansaircraft.com/knowledge-base/firewall-forward?hsLang=en#oil-system) - [Engine Selection and Installation](https://support.vansaircraft.com/knowledge-base/firewall-forward?hsLang=en#engine-selection-and-installation) - [Cowling and Baffles](https://support.vansaircraft.com/knowledge-base/firewall-forward?hsLang=en#cowling-and-baffles) - [Avionics](https://support.vansaircraft.com/knowledge-base/avionics?hsLang=en#main-content) - [EFIS and Displays](https://support.vansaircraft.com/knowledge-base/avionics?hsLang=en#efis-and-displays) - [Wiring, Harness and Panel](https://support.vansaircraft.com/knowledge-base/avionics?hsLang=en#wiring-harness-and-panel) - [Finishing](https://support.vansaircraft.com/knowledge-base/finishing?hsLang=en#main-content) - [Primers, Paint and Corrosion](https://support.vansaircraft.com/knowledge-base/finishing?hsLang=en#primers-paint-and-corrosion) - [Registrations](https://support.vansaircraft.com/knowledge-base/registrations?hsLang=en#main-content) - [Registration and Ownership](https://support.vansaircraft.com/knowledge-base/registrations?hsLang=en#registration-and-ownership) - [Inspection and First Flight](https://support.vansaircraft.com/knowledge-base/registrations?hsLang=en#inspection-and-first-flight) - [General](https://support.vansaircraft.com/knowledge-base/general?hsLang=en#main-content) - [Materials, Sealants and Composites](https://support.vansaircraft.com/knowledge-base/general?hsLang=en#materials-sealants-and-composites) - [Tools and Workshop](https://support.vansaircraft.com/knowledge-base/general?hsLang=en#tools-and-workshop) - [Rivets and Fasteners](https://support.vansaircraft.com/knowledge-base/general?hsLang=en#rivets-and-fasteners) - [Plans, Manuals and Drawings](https://support.vansaircraft.com/knowledge-base/general?hsLang=en#plans-manuals-and-drawings) [![](https://support.vansaircraft.com/hs-fs/hubfs/vans_icon_orange.png?width=58&height=48&name=vans_icon_orange.png)](https://support.vansaircraft.com/?hsLang=en) [mailto:email@email.com](mailto:email@email.com) Copyright © 2026, Van's Aircraft, Inc.