Development milestones
Designer: Rudolf Kaiser
First flight: February 1979
Aircraft librarySchleicher ASK 21
Huhu Uet · CC BY 3.0 · Schleicher ASK 21 picturedSchleicher ASK 21
A tandem two-seat sailplane designed for instruction and broader soaring use.
Glider2 profile choices
Know the plane
The ASK 21 has a glass-fibre structure, long wings, a T-tail and tandem seats for an instructor and student. The design also supports cross-country and aerobatic instruction within its operating limits.
X-Plane documents aerotow and winch launching for its implementation, together with instruments including the total-energy variometer.
Schleicher ASK 21 · Specifications (ASK 21) · real aircraft; source units retained
More about this aircraft on AirframeDB
Linked sticks and spring trim
Schleicher's maintenance pages show the front and rear sticks connected mechanically, with rods and bellcranks transmitting elevator movement. The trim system uses two levers, a connecting rod and two springs. Its friction arrangement holds the selected trim position, while a separate indicator shows that setting. The accompanying drawing makes the relationship between both seats' sticks and trim levers visible. These are details of the manufacturer's documented mechanical arrangement, without assuming how a simulator or force-feedback device reproduces it.
A birthday solo after a lunch break resets the day
Elliott had spent months preparing for his first solo, including winter practice in a cockpit simulator and an intensive flying course. When his birthday arrived, nerves unsettled his early circuits. A lunch break with his father gave him a chance to relax before returning to the airfield for another attempt.
Three better flights followed. Expecting another check, he instead found his instructor closing the rear canopy and sending him off alone. In the air, attention to traffic and his position replaced the anticipation. Back on the ground, celebration included the club’s water and shirt traditions. The story makes the short flight significant through the preparation, family support and sudden change from pupil to solo pilot.
His parents arrive just in time for a long-awaited solo
Moving between countries, study and work had repeatedly interrupted Pinder’s progress towards solo flight. A friendly conversation at an airshow eventually led him to EZAC, where members welcomed him despite his limited Dutch. Regular flying and the club’s camps finally gave him the continuity he had been missing.
During a July camp, instructor David Lindberg asked whether he was ready to go alone. At almost that moment, his parents arrived by chance on a journey through the area. A successful landing brought an enormous shout of satisfaction after a wait stretching back twenty-four years. The club’s ceremonial tyre and a second solo flight completed an afternoon made memorable by the people there to share it.
An evening checkout between work and gathering rain
Finishing work early gave Kasprzyk a chance to hurry from his hotel to Booker before dusk and building clouds ended the flying. David Byass agreed to a checkout in the ASK21. Behind the towplane, Kasprzyk found it quiet and well balanced, with a reassuringly smooth climb despite the rutted grass below.
Rain and weakening lift limited the outing, but the surroundings supplied another kind of interest: a Blériot on the field and Concorde approaching Heathrow. Byass flew Concordes for work, giving the two pilots plenty to discuss alongside Kasprzyk’s fighter experience. After an easy return, the airfield pub provided shelter from the arriving downpour and a place to continue their conversation.
Public sources 10
- Schleicher ASK 21Research background · Wikipedia revision 1372986619 · retrieved 2026-09-12
- X-Plane 12 Desktop Manual
- X-Plane aircraft and avionics manuals
- X-Plane 11 Desktop Manual
- ASK21 continued airworthiness trim system bulletinSchleicher manual amendment pages, TN 11, 20 December 1983; stick/trim drawing dated 9 March 1983
- Gearing Up for My Glider SoloRyan Elliott · 9 May 2017
- My long journey to finally going solo in a glider3 February 2020; recollection of July 2018 first solo
- Soaring in the UK - May 1999Stan Kasprzyk · Booker checkout with David Byass
- ICAO — special designatorsGlider and motorglider categories; checked 2026-09-14
- f7 Simulations ASK 21 for MSFS-2020 – iniBuilds StoreProduct listing captured 2026-09-30; edition scope from the reviewed catalogue
How the profile models it
Schleicher ASK 21
Free + ProX-Plane 12X-Plane 11
The ASK 21 has a glass-fibre structure, long wings, a T-tail and tandem seats for an instructor and student. The design also supports cross-country and aerobatic instruction within its operating limits.
This starting point selects Schleicher ASK 21. Its aircraft-level settings do not select a particular developer’s custom systems.
The profile supplies the glider’s selected stick balance. Spring resistance builds with the selected airspeed response. A separate aerodynamic term adds speed-dependent control load.
Spring trim supplies pitch context rather than an external elevator tab. Valid trim provides the configured pressure relief. Autopilot following is off.
Controls and trim
The ASK21 is a two-seat aerobatic glider with fixed-wheel landing gear, spoilers and no engine or wing flaps in the reviewed configuration. Its pitch spring-trim arrangement is distinct from an elevator-tab aircraft.
About the values
The gains are normalized profile settings. They describe the chosen effect balance; hand force depends on the device and its output limits. IAS references are tuning values rather than operating limits. Physical acceptance of this revision remains pending.
Master gain & control system
Master gain85%
The final overall output scale applied to everything the model produces, before the device cap.
More: everything (spring, loads, effects) gets stronger together.
Less: everything softens together.
Why here: Scales overall profile strength while preserving effect balance, subject to device and output limits.
Forces
Spring strength64%
The base centring force that pulls the stick back to centre. Every other force stacks on it. Too low and the stick feels limp in normal flight; too high and it fights your hand and masks the smaller cues layered above it.
More: firmer centring that resists your hand at all times.
Less: a limper stick that leans on aerodynamic load alone.
Why here: The profile supplies the glider’s selected stick balance. The baseline spring is 0.64. Its low-speed blend reaches baseline strength at 32.5 KIAS.
f7 Simulations ASK 21 for MSFS-2020Spring deadband4%
A small neutral zone around centre where the spring stays quiet, so tiny movements at rest don't chatter. Wider is calmer but looser; narrower is more precise but can twitch around centre.
More: a calmer but looser centre with more free play.
Less: a tighter centre that may chatter at rest.
Why here: Sets travel around the centre before the baseline spring resists. Smaller values engage it sooner.
Overall aerodynamic load100%
A master scale over both sustained axis loads, applied before their independent balance. Profiles normally leave this alone and tune the two axis loads instead.
More: both axes load up harder.
Less: both axes lighten together.
Why here: The aerodynamic-load gain is 1 with an indicated-speed reference of 65 KIAS. This supplies speed-dependent loading alongside the spring.
Airspeed blendingTrue
Enables the low-speed spring engagement window (start/full knots above). Off, the spring is constant at all speeds.
Why here: Allows baseline spring strength to rise with indicated airspeed where the control law permits it.
Low-speed spring floor40%
How much of the spring survives at a standstill, before airspeed can build any aerodynamic force. A high floor keeps the parked stick firm; a low floor gives the loose, cable-slack feel of a parked light aircraft.
More: a firmer stick while parked and taxiing.
Less: a floppier parked stick that only wakes up with airspeed.
Why here: Sets low-speed spring strength as a fraction of baseline when blending is enabled. One keeps full strength.
Spring engagement start9.1 kt
The airspeed where the spring begins climbing from its low-speed floor toward full strength: the controls "coming alive" on the takeoff roll.
Why here: Sets the IAS where the low-speed spring blend starts rising. This is a feel threshold, not a flight limit.
Spring engagement full32.5 kt
The airspeed where the spring reaches full strength. Between the start and this point, centring firms up progressively as airflow builds over the controls.
Why here: Sets the IAS where the low-speed blend reaches baseline strength; high-speed stiffening also uses it.
Force tuning speed65
The indicated airspeed where aerodynamic load reaches its designed full level. It anchors the whole load curve to the aircraft's real speed range: a 172 loads up by 110 knots, a jet much later.
More: loads arrive later; the stick stays light up to a higher speed.
Less: loads arrive earlier and cruise feels heavier.
Why here: Sets the IAS reference for aerodynamic loading. It is an estimate, not published cruise TAS or a flight limit.
Centre firmness vs speed30%
How much the centring itself stiffens with speed, on top of the deflection loads. Zero keeps centre feel constant; more makes the stick centre harder at cruise and looser in the pattern.
More: a centre that hardens noticeably as you go faster.
Less: constant centre feel at every speed.
Why here: The high-speed spring-stiffening gain is 0.3. It strengthens the permitted spring response above 32.5 KIAS, with the squared-speed ratio capped at 5.
Centre stiffening cap5
The upper limit on speed-driven centre stiffening, so very fast flight can't wind the spring up without bound.
More: more total stiffening allowed at high speed.
Less: stiffening clamps off sooner.
Why here: Limits the squared airspeed ratio used for high-speed spring stiffening; it is not a device-force cap.
Aileron load60%
The sustained roll load from aileron deflection and airspeed, balanced independently of pitch. Together with the elevator load it sets the control-harmony ratio reviewers talk about.
More: heavier roll forces.
Less: lighter, quicker-feeling ailerons.
Why here: Roll and pitch aerodynamic scales are 0.6 and 0.78, respectively. They set the aerodynamic axis balance. No custom spring-travel curve is enabled.
Elevator load78%
The sustained pitch load from elevator deflection and airspeed, balanced independently of roll. This is the main lever behind a type's pitch weight. It does not touch aileron, spring, trim, or buffet forces.
More: heavier sustained pitch forces at speed.
Less: a lighter elevator that takes less muscle to hold.
Why here: Scales pitch aerodynamic loading; pitch spring travel and trim responses are separate settings.
Max output force55%
A cap on each steady pitch or roll force before it reaches the device, guarding against slamming or saturating the hardware in strong maneuvers.
More: stronger peak steady forces before clipping.
Less: a gentler ceiling; hard maneuvers flatten out sooner.
Why here: Caps directed-force output. Native spring effects and device limits remain separate.
Trim
Trim relief (elevator)30%
How strongly elevator trim relieves held pitch force and shifts where the stick settles. At 100%, a properly trimmed aircraft needs no held pressure, the trim-away-the-load workflow of real flying.
More: trim removes more of the held pitch force; at 100% full trim zeroes it.
Less: you keep holding force even when trimmed.
Why here: Spring trim supplies pitch context rather than an external elevator tab. Pitch authority 0.3 provides load relief and permitted centre movement; roll authority is 0.1.
f7 Simulations ASK 21 for MSFS-2020Trim relief (aileron)10%
The same relief for roll trim. Most GA types have no real aileron trim, so this stays at zero; types with roll trim get a matching value.
More: roll trim removes more held roll force.
Less: roll trim does less.
Why here: Scales supported roll-trim relief and permitted centre movement. Zero removes roll response.
Effect gains · ground
Runway rumble30%
Rolling surface vibration from wheel speed and surface type: pavement, grass, or gravel under the gear.
More: louder surface texture through the stick.
Less: a smoother taxi.
Why here: Sets rolling texture strength, modified by speed, surface and undercarriage configuration.
Gear bumps30%
Short discrete bumps from expansion joints, ruts, and rough surface, punctuating the continuous rumble.
More: sharper hits from joints and ruts.
Less: softer ground detail.
Why here: Sets gear-bump texture during ground motion, separate from touchdown impact.
Effect gains · airframe
Stall buffet40%
Airframe shake approaching the stall and while the stall warning is active: how loudly this wing announces it is unhappy. Types with a crisp break get modest buffet and let the horn carry the warning.
More: a louder pre-stall shake.
Less: a quieter wing; the horn carries the warning.
Why here: Sets stall-buffet strength. Zero removes the cue without changing simulator stalls or warnings.
Mach buffet0%
Transonic buffet approaching the Mach limit. Meaningful for jets near MMO, zero for pistons and turboprops that never get there.
More: stronger transonic buffet near the Mach limit.
Less: a smoother high-Mach ride.
Why here: Sets high-Mach buffet strength; onset and full-strength thresholds are separate.
Flap buffet0%
Low-frequency airframe vibration with flaps extended into the airflow, in the speed window where they actually work the air.
More: a rougher ride with flaps working the air.
Less: smoother approach flap.
Why here: Sets flap buffet at the configured position and speed gates. Flap movement texture is separate.
Gear buffet0%
Airframe drumming from retractable gear hanging in the airstream. Zero for fixed-gear types, where the airframe never changes shape.
More: more drumming with the wheels hanging out.
Less: cleaner gear-down flight.
Why here: Sets gear aerodynamic buffet; movement and ground-contact cues are separate.
Stick shaker50%
The dedicated stall stick-shaker buzz, fired by the aircraft's own stall-warning system. Only types with a real shaker get a value; everything else relies on aerodynamic buffet and the horn.
More: a harder stick-shaker buzz.
Less: a subtler shaker.
Why here: Sets triggered shaker strength; inactive while the shaker feature is disabled.
Effect gains · engine, mechanical & drag
Touchdown thump50%
The one-shot kick when the wheels meet the runway, scaled by sink rate: a greaser whispers, a firm arrival thumps.
More: a harder kick at touchdown.
Less: softer arrivals.
Why here: Sets landing-impact strength; landing telemetry and response shape determine the pulse.
Reverse rumble0%
Rollout vibration while reverse thrust or beta-range props are working. Zero for types without reverse.
More: a rougher rollout under reverse.
Less: quieter reverse.
Why here: Sets reverse-thrust vibration with valid reverser and engine conditions. Zero removes the cue.
Engine rumble0%
Continuous powerplant vibration following RPM between idle and full power, the ever-present reminder that something is burning fuel up front.
More: more engine through the stick.
Less: a quieter powerplant.
Why here: Sets estimated engine vibration using configured telemetry and response, not measured cockpit vibration.
Flap motion0%
Continuous vibration only while the sim reports the flap surfaces actually travelling. It follows real actuator motion and failures, not an estimated timer.
More: more vibration while the flap surfaces travel.
Less: quieter flap runs.
Why here: Sets texture from observed flap movement; a command without movement does not establish the cue.
Autopilot follow
AP follow authority5%
How far autopilot commands may physically move the stick. Kept tiny in MSFS, where a moved axis can read back as pilot input; zero disables following entirely.
More: the autopilot visibly moves your stick further.
Less: a barely perceptible follow.
Why here: Sets admitted AP-follow gain, not a percentage of travel. Runtime ownership and input limits still apply.
Stick feel
StickFeel · Trim feel enabledTrue
Whether this feature is active in this profile.
Why here: Retained for compatibility and group membership. Trim relief, rather than this flag, controls centre movement.
StickFeel · Trim relief enabledTrue
Whether this feature is active in this profile.
Why here: Allows trim relief with supported control law and valid telemetry. Axis authorities set its amount.
StickFeel · Force trim enabledFalse
Whether this feature is active in this profile.
Why here: Enables local force trim, separate from aircraft-owned trim and add-on integration qualification.
StickFeel · G load enabledTrue
Whether this feature is active in this profile.
Why here: Allows load-factor changes to modify permitted spring laws. Passive fly-by-wire feel can suppress it.
StickFeel · Rate damping enabledTrue
Whether this feature is active in this profile.
Why here: Enables rate damping with the configured coefficients and control law.
Autopilot
Autopilot · Follow enabledFalse
Whether this feature is active in this profile.
Why here: Autopilot following is off; the configured spring and load retain the hardware feel.
Autopilot · Neutral hold enabledFalse
Whether this feature is active in this profile.
Why here: Permits centering hold during a supported AP state, separate from following a moving target.
Autopilot · Neutral hold strength0.6
Why here: Sets admitted AP neutral-hold strength; inactive while neutral hold is disabled.
Aero
Aero · EnabledTrue
Whether this feature is active in this profile.
Why here: Enables aerodynamic cues; each still needs nonzero strength and its simulator conditions.
Aero · Max flap index1
Where this effect reaches full strength (or has fully faded, for washouts).
More: a more gradual build to a later peak.
Less: a quicker build.
Why here: Sets the final flap index for detent normalization. UP plus three detents uses maximum index3.
Aero · Min flap index1
Where this effect begins fading in.
More: the effect begins later.
Less: it begins earlier.
Why here: Sets the first flap detent that admits buffet; this is a handle index, not degrees.
Aero · Shaker enabledFalse
Whether this feature is active in this profile.
Why here: Permits shaker at supported warning conditions; the switch does not establish aircraft equipment.
Ground
Ground · EnabledTrue
Whether this feature is active in this profile.
Why here: Enables ground effects; each still needs its own strength and contact or motion telemetry.
Engine
Engine · EnabledFalse
Whether this feature is active in this profile.
Why here: Enables engine cues with nonzero settings and valid running-engine telemetry.
Mechanical
Mechanical · EnabledTrue
Whether this feature is active in this profile.
Why here: Enables accessory cues with configured strengths and observed accessory movement.
Mechanical · Gain0
The strength of this effect.
More: a stronger effect.
Less: a weaker one.
Why here: Sets texture from observed gear movement, separate from aerodynamic and touchdown effects.
All profile settings
| Parameter | Value | What it controls and why |
|---|---|---|
| Spring strength | 0.64 | The profile supplies the glider’s selected stick balance. The baseline spring is 0.64. Its low-speed blend reaches baseline strength at 32.5 KIAS. |
| Spring deadband | 0.04 | Sets travel around the centre before the baseline spring resists. Smaller values engage it sooner. |
| Force gain | 1 | The aerodynamic-load gain is 1 with an indicated-speed reference of 65 KIAS. This supplies speed-dependent loading alongside the spring. |
| Master gain | 0.85 | Scales overall profile strength while preserving effect balance, subject to device and output limits. |
| Dynamic-pressure blend | True | Allows baseline spring strength to rise with indicated airspeed where the control law permits it. |
| Minimum spring factor | 0.4 | Sets low-speed spring strength as a fraction of baseline when blending is enabled. One keeps full strength. |
| Spring wake-up speed | 9.1 kt | Sets the IAS where the low-speed spring blend starts rising. This is a feel threshold, not a flight limit. |
| Spring full-strength speed | 32.5 kt | Sets the IAS where the low-speed blend reaches baseline strength; high-speed stiffening also uses it. |
| Force tuning speed | 65.0 kt | Sets the IAS reference for aerodynamic loading. It is an estimate, not published cruise TAS or a flight limit. |
| Airspeed spring stiffening | 0.3 | The high-speed spring-stiffening gain is 0.3. It strengthens the permitted spring response above 32.5 KIAS, with the squared-speed ratio capped at 5. |
| Airspeed stiffening cap | 5 | Limits the squared airspeed ratio used for high-speed spring stiffening; it is not a device-force cap. |
| Aileron force scale | 0.6 | Roll and pitch aerodynamic scales are 0.6 and 0.78, respectively. They set the aerodynamic axis balance. No custom spring-travel curve is enabled. |
| Elevator force scale | 0.78 | Scales pitch aerodynamic loading; pitch spring travel and trim responses are separate settings. |
| Maximum output force | 0.55 | Caps directed-force output. Native spring effects and device limits remain separate. |
| StickFeel · Trim feel enabled | True | Retained for compatibility and group membership. Trim relief, rather than this flag, controls centre movement. |
| StickFeel · Trim relief enabled | True | Allows trim relief with supported control law and valid telemetry. Axis authorities set its amount. |
| StickFeel · Elevator authority | 0.3 | Spring trim supplies pitch context rather than an external elevator tab. Pitch authority 0.3 provides load relief and permitted centre movement; roll authority is 0.1. |
| StickFeel · Aileron authority | 0.1 | Scales supported roll-trim relief and permitted centre movement. Zero removes roll response. |
| StickFeel · Force trim enabled | False | Enables local force trim, separate from aircraft-owned trim and add-on integration qualification. |
| StickFeel · G load enabled | True | Allows load-factor changes to modify permitted spring laws. Passive fly-by-wire feel can suppress it. |
| StickFeel · Rate damping enabled | True | Enables rate damping with the configured coefficients and control law. |
| Autopilot · Follow enabled | False | Autopilot following is off; the configured spring and load retain the hardware feel. |
| Autopilot · Follow authority | 0.05 | Sets admitted AP-follow gain, not a percentage of travel. Runtime ownership and input limits still apply. |
| Autopilot · Neutral hold enabled | False | Permits centering hold during a supported AP state, separate from following a moving target. |
| Autopilot · Neutral hold strength | 0.6 | Sets admitted AP neutral-hold strength; inactive while neutral hold is disabled. |
| Aero · Enabled | True | Enables aerodynamic cues; each still needs nonzero strength and its simulator conditions. |
| Aero · Gain | 0.4 | Sets stall-buffet strength. Zero removes the cue without changing simulator stalls or warnings. |
| Aero · Gain | 0 | Sets high-Mach buffet strength; onset and full-strength thresholds are separate. |
| Aero · Gain | 0 | Sets flap buffet at the configured position and speed gates. Flap movement texture is separate. |
| Aero · Max flap index | 1 | Sets the final flap index for detent normalization. UP plus three detents uses maximum index3. |
| Aero · Min flap index | 1 | Sets the first flap detent that admits buffet; this is a handle index, not degrees. |
| Aero · Gain | 0 | Sets gear aerodynamic buffet; movement and ground-contact cues are separate. |
| Aero · Shaker enabled | False | Permits shaker at supported warning conditions; the switch does not establish aircraft equipment. |
| Aero · Amplitude | 0.5 | Sets triggered shaker strength; inactive while the shaker feature is disabled. |
| Ground · Enabled | True | Enables ground effects; each still needs its own strength and contact or motion telemetry. |
| Ground · Gain | 0.3 | Sets rolling texture strength, modified by speed, surface and undercarriage configuration. |
| Ground · Gain | 0.3 | Sets gear-bump texture during ground motion, separate from touchdown impact. |
| Ground · Gain | 0.5 | Sets landing-impact strength; landing telemetry and response shape determine the pulse. |
| Ground · Gain | 0 | Sets reverse-thrust vibration with valid reverser and engine conditions. Zero removes the cue. |
| Engine · Enabled | False | Enables engine cues with nonzero settings and valid running-engine telemetry. |
| Engine · Gain | 0 | Sets estimated engine vibration using configured telemetry and response, not measured cockpit vibration. |
| Mechanical · Enabled | True | Enables accessory cues with configured strengths and observed accessory movement. |
| Mechanical · Gain | 0 | Sets texture from observed flap movement; a command without movement does not establish the cue. |
| Mechanical · Gain | 0 | Sets texture from observed gear movement, separate from aerodynamic and touchdown effects. |
Public sources 10
- Schleicher ASK 21Research background · Wikipedia revision 1372986619 · retrieved 2026-09-12
- f7 Simulations ASK 21 for MSFS-2020Exact product and reviewed configuration passagesProduct listing captured 2026-09-30; edition scope from the reviewed catalogue
- X-Plane 12 Desktop Manual
- X-Plane aircraft and avionics manuals
- X-Plane 11 Desktop Manual
- ASK21 continued airworthiness trim system bulletinSchleicher manual amendment pages, TN 11, 20 December 1983; stick/trim drawing dated 9 March 1983
- Gearing Up for My Glider SoloRyan Elliott · 9 May 2017
- My long journey to finally going solo in a glider3 February 2020; recollection of July 2018 first solo
- Soaring in the UK - May 1999Stan Kasprzyk · Booker checkout with David Byass
- ICAO — special designatorsGlider and motorglider categories; checked 2026-09-14
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