Autopilot modes HELP..

[ollycopter]

Hey guys. Having a bit of brain dump. Have a sim session on a Citation V and am struggling with the modes.. Could anyone give me a quick run down on the functions of IAS FLC V/S and NAV settings? I just need a booster. Its been so long since I flew and this sim ride came up quickly. Had little time to do something about it. I have left all my books abroad for weight travel reasons but this site could yet be a job saver. If anyone could help I would be forever in their debt. Many thanks. Ollycopter

[BOAC]

Citation I know not, but 737:

IAS demands speed for autothrottle in Cruise (and V/S), and sets speed for LVL CHG - pitch then controls IAS.

LVL CHG is throttles closed or at 'Climb Power', pitch to maintain IAS; V/S provides power and pitch inputs to maintain selected V/S at selected IAS. Any help or too simple?

[ollycopter]

Hi, thanks.. It does help.. The citation has no auto throttles so am still a little unsure what I am doing. Did MCC in 737 so am getting use to throttles again.. Thanks so much for getting back to me.. Happy flying.. Olly

[moggiee]

With no autothrottle, IAS will control the aircraft speed by adjusting the pitch (i.e. climbing is excess power, descending if too little).

[Old Smokey]

ollycopter,

IAS, FLC, V/S, and NAV settings

Until a real Citation V pilot comes along, I'll do my best to answer your question for typical AFDS equipment for that generation of aircraft. Thus it is a 'generic' answer, but I hope that it's of some assistance.

IAS - As the name says, this holds the selected speed. Without auto-throttle, this is accomplished through pitch changes up and down to maintain speed with (presumably) a constant thrust. It is used during climb and descent, and STRICTLY NOT on cruise. With excess thrust set on climb, the aircraft will pitch up to maintain the selected speed, resulting in a climb. With a thrust deficit during descent (idle), or a single-engine drift-down (one engine at MCT), the aircraft will pitch down to maintain speed, providing a descent (or during a OEI drift-down, the least descent Rate/Angle). The Rate of Climb or Descent will depend upon the thrust set, thus it is strictly NOT used during cruise, where ALT hold is used instead, both ALT and IAS are 'Pitch' modes, and both cannot be used simultaneously.

The selected speed is usually that at the time on mode engagement, but may be varied either by digital selection on your MCP, or, if you have the facility, by 're-synchronising" to a new speed via the Control Wheel switch. IAS doubles as a Mach Hold, and holds Mach number after manual selection of Changeover by you on the MCP.

Unlike FLC, IAS has no senseing of whether a Climb or Descent is required, and will give you a descent in lieu of climb if thrust is insufficient, and Vice Versa.

FLC - has it's similarities to IAS inasmuch as it holds a pre-selected speed, but senses whether a Climb or descent is required by comparing your present Altitude to the target altitude set on the MCP. It will be at a fixed speed schedule, as set by the manufacturer, typically taking care of the 250 KIAS limit below 10,000 feet, and usually has an automatic IAS/Mach changeover for the fixed speed schedule. There is usually one standard IAS / Mach schedule for climb, and one for descent, although there may be a second selectable (usually higher) speed schedule. A good aspect of FLC is that it ensures at least 500 fpm climb during acceleration, or 500 fpm rate of descent during deceleration to comply with the ATC requirements.

V/S - holds the selected Vertical Speed. Usually this is the V/S at the time of engagement, which may be modified on the MCP, or through the Control Wheel 'synch' switch to a new value. Without Auto-Throttle as your first line of defence, IAS / Mach must be guarded carefully during V/S engagement to ensure that speed does not decay or decrease excessively. V/S is another Pitch mode, and the required V/S is achieved through pitch changes. As a pitch mode, it cannot be simultaneously engaged with IAS, FLC, ALT, or G/S modes.


NAV - NAV will engage to whatever Lateral Navigation display that you have displayed on your HSI, whether it be FMC/FMS track, a VOR radial, or a Localiser. As Roll modes, these 3 modes cannot be simultaneously engaged. If Localiser is the selected Lateral Navigation mode, steering will NOT be to the same degree of accuracy as during the Approach mode. HDG (and TRK if available) are also Lateral / Roll modes, and cannot be engaged simultaneously with FMC/FMS track, a VOR radial, or a Localiser, BUT these latter 3 may be 'Armed' for capture whilst in HDG or TRK mode. Once captured, HDG (and TRK if available) become idle.

Generic answers for the current generation of equipment that you operate, and I hope that there is some guidance here for your operation.

Standing by for a REAL Citation V pilot...................

Regards,

Old Smokey