TVM

TVM (Target Velocity Match)

TVM evaluates the velocity of a selected target and uses the ship thrust to match both it's speed and direction.

Orbital rendezvous: The Orbit instrument can plan a transfer to a future point approximately 5 km behind a station or spacecraft and execute it with DOR. See the Orbit rendezvous procedure for planning, warnings and execution. TVM is a separate target-relative velocity control; selecting a TVM closure speed does not calculate an orbital transfer. The manual TVM approach procedure below remains separate from the Orbit planner.

DOR rendezvous handoff: When DOR successfully completes a rendezvous, it automatically engages TVM with TVM SET 0.000 km/s and keeps the selected station or spacecraft. The Autoflyte disconnect sound plays once as DOR switches off. Manual cancellation and automatic aborts do not trigger this handoff. You can also select TVM manually while DOR is active; this disengages DOR and resets the TVM closing speed to zero. See rendezvous completion and TVM.

Surface journeys (planning only): The Orbit surface planner compares AUTO / ATM / SUB / ORB profiles at a chosen PASS deadline. PLAN ONLY / ATM HANDOFF does not automatically select TVM or another Autoflyte mode and does not command atmospheric flight or landing. The pilot remains responsible for selecting and operating suitable controls.

Closure Rate

At a desired closing speed of 0.000 km/s, TVM commands a velocity match with the selected target. It does not actively hold a particular separation, restore the Orbit planner's 5 km trail position, or provide collision avoidance. Monitor actual separation and relative motion during the approach; engine response and external forces still affect the result.

If you adjust the desired to a positive number you will be moved parallel to the target plus the closure speed and direction you are aiming. Your direction the nose is point and the desired closure speed is added to the target's vector as an additional vector.

If you adjust the desired to a negative number you will be moved parallel to the target minus the closure speed and direction you are aiming. Your direction the nose is point and the desired closure speed is subtracted from the target's vector.

TVM CUR shows the signed instantaneous rate at which the straight-line distance to the selected target changes, in km/s: positive means closing, negative means separating. Station targets use the station centre. For unchanged positions and velocities, rotating either vehicle does not change CUR. A zero reading can also occur during sideways relative motion, so it does not by itself confirm a complete velocity match. TVM SET remains the commanded additional velocity along the nose direction described above; with a nonzero SET, turning can change actual closure over time as TVM applies thrust.

Small axial corrections: When the speed error and required force fit the installed forward/reverse RCS, TVM uses those jets instead of bringing up the main engines. It accounts for remaining main thrust during spool-down. Larger errors or sustained force demand return to main thrust, with separate entry and exit thresholds to avoid rapid switching. This applies to the fore/aft correction; main-engine lift required for hover or controlled descent remains active independently. Engine and RCS limits still apply.

Collision warning

While TVM is controlling an airborne or free-flying vehicle with a station or vehicle selected, a large red COLLISION flashes in the centre of the PFD when the current relative-motion path intersects the target's estimated collision envelope and the estimated braking distance reaches the remaining clearance. The collision alarm repeats continuously while the warning is active. Both the compact and wide PFD show the warning.

The estimate uses relative motion, loaded mass, current attitude, available main-engine and translation-RCS thrust, engine condition and response. A fast pass whose projected path clears the target does not trigger it. Loaded hull bounds help distinguish solid station structure from open space; when distant geometry is unavailable, the estimate uses the target's outer bounds. These bounds are approximate and can warn before an exact hull intersection.

The warning clears when the projected path is clear or sufficient braking margin is restored. It also clears when TVM is disengaged, the selected target is lost, guidance stops updating, power is lost, flight is frozen, or the vehicle lands or docks. Selecting another target evaluates that target afresh. WAYPT ground standby does not provide this warning. It remains available during hover, atmospheric flight, ascent, coast, orbit and re-entry, and in simulator training, while valid TVM target guidance is active.

This warning does not command an avoidance manoeuvre, change TVM SET or apply emergency braking. Begin slowing early and monitor separation yourself. It is a straight-line forecast using current motion and thrust; future orbital curvature, gravity differences, aerodynamic forces and target manoeuvres can change the outcome. It checks the selected target, not terrain or every nearby object. Silence is not confirmation of a safe approach.

Ground standby and takeoff

Select a valid entry in the waypoint manager, select WAYPT as the target, then press K to engage TVM while on the ground. The source indication shows TVM and the A/T area shows SBY on the compact PFD or STDBY on the wide FMA. Standby keeps TVM selected while its automatic translation and leveling wait for liftoff.

Hold F9 for the normal upward-thrust request. Once airborne, TVM begins its normal control automatically; you do not need to press K again. With the ground-reference BCL controls described below, the indication changes to ASC on the compact PFD or CLIMB on the wide FMA while F9 remains held. Release F9 to request hover. Loading, engine condition, attitude and the vehicle's VTOL limits still determine whether it can lift off and hover.

While on the ground, switching away from WAYPT, clearing the selected waypoint or leaving no valid waypoint selected disengages TVM. A selected vehicle or station cannot provide ground standby. Select a valid waypoint and press K again to re-engage; restoring the selection alone does not re-arm it. Pressing K again also cancels standby. On aircraft touchdown, TVM disengages and the engines are commanded back to forward thrust once. You can select reverse manually afterward; continued ground contact does not cancel that selection.

Vertical Landings

With a ground waypoint selected as the reference, TVM allows a controlled descent in a VTOL vehicle with suitable vertical thrust. A vehicle or ARJ stationary on the ground can also provide a ground-relative velocity reference.

Select TVM with K and use 0.000 km/s commanded closing speed to damp motion relative to the selected reference. On the E-10, E-11, A-4 and W-6, ground-referenced TVM in BCL provides these vertical controls:

• Hold F9 to request maximum upward thrust. Engine condition, loading, attitude and the VTOL operating limits still constrain the delivered lift.
• Hold F8 to select a descent rate based on radio height above ground and the vehicle's descent schedule below. Keep monitoring actual vertical speed; a selected rate is not a guarantee of the achieved sink rate.
• Release either key to request hover again. Hover means zero vertical velocity relative to the ground reference, not a selected altitude or position hold. Allow for the aircraft's response and remaining momentum.

E-10/E-11: the table shows the shared nominal descent ceilings and an example of how braking limits reduce the command. All rates are downward metres per second; heights are radio height above ground (AGL), not altitude above sea level. The controller reduces the ceilings using available braking thrust, loading, attitude, engine/nozzle response and a forecast of current downward motion. It begins braking automatically while F8 remains held.

The E-10 example assumes a healthy aircraft at 147,421 kg, level, with sea-level engine output, no horizontal airspeed, fully positioned VTOL nozzles and no initial vertical motion or acceleration. Its values are rounded to 0.1 m/s. They are initial command ceilings, not a promised descent path: once descending, the motion forecast can lower the command further. The E-11 shares the nominal schedule but its available thrust produces different braking limits.

E-10/E-11 F8 descent schedule and reference E-10 commands

Height (m AGL)	E-10/E-11 nominal ceiling (m/s down)	Reference E-10 command after braking limit (m/s down)
1	1.0	1.0
10	1.0	1.0
25	6.25	2.5
50	15.0	6.3
65	18.0	8.5
100	25.0	13.1
250	40.0	29.2
500	65.0	49.4
850	100.0	71.5
1,000	100.0	79.7
1,500	100.0	100.0

The nominal ceiling is 1 m/s at or below 10 m; it increases linearly to 15 m/s at 50 m and 25 m/s at 100 m, then by 10 m/s per additional 100 m until reaching the 100 m/s ceiling at 850 m. Braking limits and the motion forecast still apply throughout. The table's 2.5 m/s at 25 m is the reference E-10 braking limit, not a universal 25 m target.

At 1 m AGL the normal held-F8 command is still 1 m/s down. Briefly releasing F8 requests hover and can be used to descend more slowly; allow enough height for the existing descent to stop.

A-4/W-6: the nominal schedule remains 1 m/s at or below 25 m AGL, rising to 10 m/s at 50 m, holding 10 m/s through 100 m and allowing faster descent above that. Braking limits can select lower rates. This ground-reference descent schedule retains its total-airflow allowance of 81 m/s or less; the W-6 also reserves margin below its door-pressure limit using local air density. That scheduled-descent allowance is separate from door availability and does not impose a manual F9 speed cutoff.

A heavy or damaged aircraft may not have enough lift to arrest a descent or hover. The schedules do not add thrust or guarantee clearance from terrain.

Manx hover-capacity warning: While the W-6 is airborne in ground-reference BCL TVM, its current HOVER / CLIMB / DES indication flashes red when available steady main-engine lift cannot support the loaded weight at the current altitude. The compact labels are HOV / ASC / DES. The collision alarm loops while this condition persists. This applies with a ground waypoint or an on-ground vehicle selected, including a moving ground vehicle, and in simulator training. The comparison includes the Manx's 70% downward-flow limit, local engine output, engine condition, wear and available trim authority.

The warning clears after lift capacity recovers to at least 2% above weight, avoiding rapid on/off changes at the limit. It also clears when vertical TVM control ends, the reference becomes invalid, guidance stops updating, flight is frozen or the aircraft touches down; ground standby remains quiet. An independent selected-target collision warning can keep the same alarm sounding. This is a steady, level-hover capacity warning: it does not predict ground impact or account for temporary engine spool-up, door travel or pressure inhibition, attitude loss, or remaining descent momentum. Monitor height, vertical speed and the landing area even when the warning is silent.

In this BCL ground-reference mode the closing-speed setting controls the horizontal component along the nose direction; F8/F9 control the vertical request separately. Other references, ACL operation and the P-13/T-19 retain their usual TVM and translation behavior. On the E-10, E-11 and A-4, upward main-engine vectoring remains available at any altitude, including vacuum. The Manx also permits upward main thrust at any altitude, including vacuum, subject to its door dynamic-pressure protection: inhibit above 4,000 Pa and re-enable below 3,200 Pa. It uses vertical RCS while the doors are inhibited. See VTOL operating limits.

Near a station, use short manual translation inputs and monitor relative velocity. E-series/A-4/W-6 F9 can command much stronger main-engine upward thrust, while stopping upward drift still relies on weaker downward RCS. TVM continues to request braking after release, but engine rundown and available opposite thrust limit how quickly it can stop.

Below-stall leveling: while matching a ground waypoint or grounded vehicle in subsonic flight, TVM uses thrust augmentation to bring the nose and wings level with the local horizon. Keep thrust augmentation enabled and serviceable, with cockpit power available. Leveling controls pitch and roll; you retain yaw control. Holding a pitch or roll key overrides leveling on that axis; releasing it resumes the assistance. With a joystick, deflecting the stick overrides that axis and centering it resumes leveling. This automatic key-release behavior applies only while below-stall ground-reference leveling is available; ordinary keyboard controls retain their normal behavior elsewhere. The default Numpad 5 (Null Rates) control also centers retained manual inputs.

Leveling is strongest below 90% of the computed stall speed and fades to zero at the stall speed. It also fades from Mach 0.8 to Mach 1, using the full airflow speed, so low IAS during fast ascent or re-entry does not command a landing attitude. It does not apply to airborne or orbital targets, while docked or on the ground, during flight freeze, or without valid stall-speed data and available rotational thrust. It becomes available again automatically when those conditions permit, while TVM remains selected. Available thrust, vehicle mass, damage and wear limit how quickly the aircraft can level.

Monitor attitude, vertical speed, height above ground and the landing area throughout the descent. Selecting a ground waypoint supplies the velocity reference; it does not steer the vehicle to that waypoint's position or provide terrain avoidance or an automatic flare. Aircraft touchdown disengages TVM and selects forward thrust once. You can select reverse manually after landing. The thrust-lever settings and normal engine/reverser response remain in effect. See Autoflyte special modes for the relationship between TVM and ordinary flight guidance.

Wide FMA indications

The wide Flight Mode Annunciator used by the E-11 and W-6 shows TVM in its upper source cell. The cell immediately below, normally used for A/T, shows standby or the active translation command:

• STDBY — valid WAYPT ground standby, awaiting liftoff.
• HOVER — ground-reference BCL vertical hold, with F8/F9 released.
• CLIMB — F9 maximum upward-thrust request in that mode.
• DES — F8 scheduled-descent request in that mode.
• MATCH — ordinary target-relative velocity control, including ACL and airborne/orbital references.

HOVER, CLIMB and DES apply to the ground-reference BCL controls described above for the E-10, E-11, A-4 and W-6. These labels identify the commanded mode, not the achieved vertical speed or a guarantee of sufficient lift.

LEVEL appears in the lower pitch/vertical cell while TVM owns nose leveling and in the lower lateral cell while it owns wings leveling. It remains visible while holding an already level attitude. Holding a pitch or roll key, or deflecting a joystick, removes LEVEL from that axis. Releasing the key or centering the stick restores the indication when leveling is available. The two axes can therefore show LEVEL independently.

The active indications clear when their control is unavailable, frozen or no longer updating. DOR or ordinary Autoflyte handoffs show the new controller's indications. Armed LOC/G/S remain in the upper row.

Compact FMA indications

The E-10 and A-4 show TVM at the upper left of the PFD attitude indicator. The right-aligned upper-right indication shows standby or the current translation command:

• SBY — valid WAYPT ground standby, awaiting liftoff.
• HOV — ground-reference BCL hover command, with F8/F9 released.
• ASC — commanded climb/upward thrust with F9.
• DES — commanded descent with F8.
• MATCH — ordinary target-relative velocity matching.

These are commanded modes, not confirmation of achieved vertical speed. For example, ASC can be displayed while upward thrust is still arresting a descent.

The compact FMA shows steady LEVEL independently in the lateral and vertical active-mode cells while TVM owns roll or pitch leveling. Manual input releases that axis and blanks its cell; the other axis can remain LEVEL. Assistance reappears when the control is released and leveling is available. Source and command labels do not alternate.

Unavailable, stale or frozen controller status removes the TVM command and LEVEL labels; engaged TVM still shows its source and A/T status on the PFD. DOR or ordinary Autoflyte takes display precedence when it takes control. Armed LOC/G/S remain in the upper FMA row, and active guidance changes retain their normal three-second highlight.

The compact and wide displays describe the same TVM controls. Neither display adds altitude/position capture or guarantees that the aircraft has enough thrust and attitude authority to hover.

Using TVM to approach a Space Station

One of the most useful things you can do with TVM is docking with CPOC or TAC

Remember as the station orbits the planet of course it is a giant circle. E is a perfect circle for the stations, CPOC is at 3000km often the shortest route is through the planet. You MUST always monitor your orbital path.

1. Look at the Ground Track figure out where the station will be when you have climbed out of the atmosphere.
2. Take off heading on a course to intercept.
3. Climb to approximately 100KM
4. AIM the nose of the ship at the Direction of target of the station
5. Turn On TVM and set it to a close speed to 3-4KM/sec closure speed Version 2.2.7.3 and newer the game controller set for "Engine 1" will control TVM closure)
6. Keep aiming the nose at the station
7. Keep looking at VSI to make sure it is NOT going negative
8. As you get close to the station start to slow down. An E-10 NOT full of cargo will take over 250KM to to slow to 0.250 KM/sec A heavy E-10 can take over 400Km. Brake early your goal is to not have the station remind you of the 0.250 km/sec speed limit.
9. Ask for clearance to dock.
10. Stop with in 100m of the new waypoint.
11. Press 'd' to dock

Congratulations you are docked.