1,360
edits
Space Shuttle: Difference between revisions
Jump to navigation
Jump to search
→Automated flight
| Line 497: | Line 497: | ||
Automated flight is available for all nominal mission phases except for the final approach and touchdown (for which in reality no AP is available either) as well as all single engine loss intact aborts and all two engine out contingency aborts. | Automated flight is available for all nominal mission phases except for the final approach and touchdown (for which in reality no AP is available either) as well as all single engine loss intact aborts and all two engine out contingency aborts. | ||
Unlike an airplane which is usually in or close to a steady-state equilibrium (level flight at cruise altitude) when under AP control, this is almost never the case for the Shuttle. Thus, the AP requires a context to work properly - whether a current state vector is good or bad depends on what one wants to achieve. Usually this context is a guidance target (i.e. a desired orbit, a landing site, an abort MECO condition,...) and if no such target is provided, the AP will not engage. | |||
If there is a valid guidance target, the PFD will display error needles even if the AP is disengaged which reflect what the AP would try to do in the current situation which can be used for manual piloting. The AP can be used separately in the pitch and yaw/roll axis and independently for throttle/speedbrake control. | |||
Once disengaged, it is as a rule not wise to re-engage the AP if the Shuttle has deviated too much from the intended state. Many AP stages are based on closed loop guidance and will try to steer back to the desired solution, however this may not be possible. | |||
Also, automated flight does not mean the pilot can lean back and the Shuttle will handle all aborts on its own - some AP modes specifically need to be engaged or augmented by DPS options to properly work - see the Crew Operations Manual for detailed instructions. In particular, if in an emergency the wrong AP mode is engaged, the Shuttle may try to solve a kinematically impossible maneuver which usually results in loss of control. | |||
Finally, do not expect miracles from the AP. It will usually save the orbiter even after the loss of two engines, but it may not always on its own find a viable solution to a landing site in an abort scenario. In general, automated flight is much better at manging the instantaneous state (holding an alpha schedule, aiming at a waypoint) than at longer-term planning (managing gliding range after an abort,...). | |||
Different from the powered and gliding phase, the orbital DAP contains automatic routines for attitude management - pointing the Shuttle, tracking a location or a celestial object or automated OMS burn maneuvers. | |||
Operating the Shuttle AP properly is very different from operating airplane APs and requires a profound knowledge of OPS sequences and major mode transitions as well as strict adherence to the published procedures. | |||
== Payload handling == | == Payload handling == | ||