VTOL

VTOL means vertical take-off and landing. The A-4, E-10, E-11 and W-6 use main-engine thrust for VTOL. Reaction control (RCS) supplies attitude control and a small amount of vertical translation. The P-13 uses its separate TGD drive; the T-19 has no VTOL system.

Controls

The default F9 binding requests upward translation and F8 requests downward translation. Equivalent requests can be assigned to a game controller. Main-engine throttle and forward/reverse selection continue to request longitudinal acceleration. Autoflyte requests use the same propulsion limits as manual controls.

With TVM engaged against a ground reference in BCL, the E-10, E-11, A-4 and Manx use F9 for maximum upward demand, F8 for a height-scheduled descent, and key release to request hover. This does not select a fixed altitude, steer to the reference's position or guarantee sufficient lift. See TVM vertical landings for the descent schedule and limitations.

No separate nozzle or VTOL-door control is required. The propulsion system combines the vertical and longitudinal requests automatically. Requesting lift can increase main-engine output even with the longitudinal throttle at idle. Allow for engine thrust buildup before attempting to leave the ground; nozzle or door travel alone does not provide full lift.

See RCS for the separate reaction-control installation, translation controls, nozzle ratings and shared attitude/translation limits. An upward F9 request can use main-engine lift; it is not an RCS-only command.

Engine arrangements

E-10, E-11 and A-4

The front and rear outlets on the two side engines tilt down through 54 degrees. Full nozzle travel takes about 1.5 seconds. Each engine can supply its full rated thrust through each opposing outlet. At 54 degrees, about 80.9% of each outlet's thrust acts vertically and 58.8% acts longitudinally. Equal opposing flows cancel longitudinal force while adding lift; both flows consume fuel. Unequal flows permit braking or acceleration while producing lift.

The side-engine nozzles can move while the engines are firing. While airborne, applying or releasing lift starts nozzle travel immediately; thrust buildup and rundown still take time. Forward or reverse thrust can develop during the transition, without waiting for both wing engines to extinguish.

When grounded and idle below 20 km MSL and 100 m/s air-relative speed, the side-engine nozzles automatically park at 54 degrees downward, including during shutdown. This provides an inspection position and removes the tilt delay from a subsequent VTOL request; it does not produce thrust or remove engine spool-up time. Forward or reverse thrust requests return the nozzles toward axial unless lift is also requested. After taxi thrust is released, remaining axial flow runs down before the nozzles park. Releasing lift while still grounded leaves fully tilted nozzles down as thrust runs down.

The E-10 and E-11 aft engine is mechanically fixed along the aircraft's longitudinal axis in every mode, including with AUG on. It supplies forward or reverse thrust and approximately one third of the three-engine axial rating; it does not tilt for VTOL or vector for pitch control. AUG uses the available RCS attitude authority, with aerodynamic controls contributing when airflow permits. The A-4 has two engines and no aft engine.

W-6 Manx

The Manx routes thrust through protected downward outlets. Its underside doors take about 0.6 seconds to open. Downward exhaust is inhibited until the doors are fully open, and the downward flow is shut off before they close.

Each engine shares one thrust budget between its forward, reverse and downward outlets. Full downward thrust leaves no thrust available for longitudinal acceleration. Partial lift can be combined with forward or reverse thrust. The engine rating is unchanged: a heavy Manx may be unable to hover.

Operating envelope

The E-10, E-11 and A-4 have no altitude cutoff for main-engine vertical thrust. F9 can request nozzle vectoring in atmospheric flight, high-altitude ascent, suborbital coast and orbit, including vacuum. Power, engine condition and the available force and balance limits still apply.

On the E-10, E-11 and A-4, hold F9 during forward flight to request upward thrust while continuing to command forward or reverse thrust. The tilting nozzles do not use the Manx door dynamic-pressure interlock. This is not an exemption from the aircraft's operating-speed, heating or control limits; allow for nozzle travel and engine spool response.

The W-6 Manx protects its downward-outlet doors using dynamic pressure (q), calculated from local atmospheric mass density and total air-relative speed: q = ½ρV². Airflow in every direction counts, including vertical descent and sideslip. There is no independent altitude, airspeed or vacuum restriction.

Door protection condition	Dynamic pressure
Enable or re-enable	Below 3,200 Pa (3.2 kPa)
Remain enabled	Up to and including 4,000 Pa (4.0 kPa)
Inhibit downward thrust and close doors	Above 4,000 Pa (4.0 kPa)

Between 3.2 and 4.0 kPa the system retains its previous state. An inhibited system must fall below 3.2 kPa to re-enable. At the reference surface density of 3.063 kg/m³, the re-enable and inhibit thresholds correspond to about 45.7 and 51.1 m/s through the air; local temperature and density change these speeds.

F9 can request the protected downward outlets during atmospheric flight, high-altitude ascent, suborbital coast and orbit whenever the pressure limit permits. In vacuum the aerodynamic pressure is zero, so orbital speed alone does not inhibit them. Doors open only when lift is requested, and downward exhaust waits until they are fully open. Normal release allows thrust to spool down before closure; exceeding the pressure limit cuts downward flow before the doors close. Power, engine condition, docking and available force/balance limits still apply. This aerodynamic-load interlock does not establish thermal protection for exposed outlets during re-entry.

When the Manx doors are inhibited, vertical translation uses RCS only; its axial main engines remain available. Opening the doors does not add engine output: forward, reverse and downward thrust share the same per-engine budget.

On the E-10, E-11, A-4 and W-6, downward main exhaust produces force toward the aircraft's top; it does not provide main-engine downward translation. F8 still uses downward RCS outside TVM's BCL descent mode. In orbit, a sustained F9 input can build upward velocity much faster than downward RCS can remove it. Allow for engine rundown and braking time when maneuvering near a station.

Hover capability and balance

Available lift depends on loaded mass, engine condition, power, atmospheric performance and the torque that can be balanced about the centre of gravity. The allocator varies front/rear and left/right output, with RCS supplying the remaining attitude correction. It reduces thrust when the requested combination cannot be balanced. Maximum gross weight is not a guarantee of VTOL capability.

Vertical RCS on these four vehicle types provides approximately 0.5 m/s² at maximum gross weight at full power and condition. Its acceleration increases at lower mass and decreases with power or wear. It supplements main-engine lift and provides downward translation. On the Manx it is the source of vertical translation while the doors are inhibited. The P-13's TGD operation is separate.

Aircraft-specific nominal-CG, hover-capacity and powered-ascent references are available under E-10 operating envelope and E-11 operating envelope.

Near-surface effects

Main-engine exhaust can raise dust, snow, mist or steam wherever its spreading plume reaches nearby ground or water around your own A-4, E-10, E-11 or W-6. Ground wash follows actual engine output and nozzle direction in manual flight and with Autoflyte; it does not require VTOL operation. For example, an E-11 pitched steeply nose-up can blow the ground with its aft engine. Wash can extend beyond the visible exhaust glow, becoming broader and weaker with distance. Parked nozzles alone do not produce wash.

Dry loose sand produces more dust than roads or hard ground. Mineral dust forms faint rolling clouds with a muted tint from the terrain; paved surfaces produce lighter gray dust. Wet ground suppresses dry dust and produces pale mist with a subtle steam component. Open water produces spray and a much denser, taller white steam cloud. Snow-covered ground can produce pale airborne snow. Surface wetness uses accumulated weather when available; low cloud by itself does not mean wet ground. The visible steam represents condensed droplets mixed with spray. This is a visual effect and does not calculate heat transfer, boiling or water consumption.

Dry snow and loose sand/dirt can form dense clouds that severely reduce outside visibility during hover, landing and low passes. Sustained exhaust feeds waves of cloud that spread outward, with more flow toward the downstream side of an angled plume. Snow also carries small flakes and streaks along this outward flow. Clouds left behind by a moving or stopped source drift with surface wind and fade over several seconds; steam also rises, more strongly over open water than over wet ground. Dust, mist, spray and steam affect visibility, not available lift or vehicle handling, and are absent in the flight simulator. Distant terrain, intervening structures and shoreline transitions are approximate.

See also TVM, Autoflyte, Airspeed and Vieneo.