PHI GOM S-92 - AFCS Flashcards
S-92 - Automatic Flight Control System PTM CHAPTER 15
What provides signals for SSAS?
AHRS (Attitude Heading Reference System)
Rate Gyros provide signals for the _____.
How many rate gyros are there?
PSAS
6
There are two rate gyros for each PSAS axis ( pitch, roll, and yaw). The No. 1 rate gyros supply rate signals for PSAS 1 , and the No. 2 rate gyros supply the rate signals for PSAS 2 .
What is the difference between the SSAS and PSAS computers?
Computer functions are identical.
The only difference is attitude and acceleration input.
AHRS for SSAS
Rate Gyros for PSAS
What limitation(s) are associated with SSAS?
Airspeed 120 KIAS
Takeoff in SSAS prohibited.
since secondary SSAS and the autopilot both have the same attitude input there is no error crosscheck like PSAS to AP. MTM
What does SAS provide?
Is it inner loop or outer loop?
SAS provides short-term rate damping.
Inner loop.
What is the function of the Rotary Variable Differential Transiometers (RVDT’s) in the AFCS system?
Give flight control position information to the AFCS system. One is on each control rod near trim actuators.
Bonus: Additional RVDT’s are in the throttle quadrant and collectives to send inputs to the FADECs.
The ___________ and ______provide signal input for Enhancements in the AFCS System.
What are the enhancements?
accelerometers for:
Hover Augmentation
Gust Alleviation
AHRS:
Heading Hold
Turn Coordination
There are six accelerometers: a pair of lateral , a pair of longitudinal, and a pair of vertical.
If both AP computers are turned off, will enhancements and trim beepers still be functional.
No.
At least one AP must be engaged for trim beepers and enhancements to be operational.
With the AP switches off, the corresponding SAS function (via PSAS computer) still provides its rate damping stablization but the enhancement functions (via AP computers) are removed from that SAS actuator.
What provides attitude inputs for the AP computers?
AHRS (Attitude Heading Reference System)
If AHRS #1 fails, what indications will be seen in the cockpit?
Loss of Attitude Indicator, HSI, and IVSI.
AP #1 FAIL
Why should the pilot turn off a failed autopilot?
To prevent any erroneous signals being sent to the flight controls resulting in an un-commanded movement or hardover.
What is the trim rate of the trim system in ATT mode?
10% per second
What maximum angle of bank is used by the Autopilots when coupled to the FD? What about decoupled using the cyclic trim switch?
23 degrees- flight director
30 degrees- cyclic trim
use the max trim limit for steep turns during your 297 ride
What FD mode(s) may be coupled below 50 KIAS (Vmini)?
RALT and RIG approach
What is the default climb or descent rate when utilizing ALTP to initiate a climb or descent?
500 FPM
Why would a pilot select the VAP FD mode when flying a VOR approach rather than NAV?
VAP changes the sensitivity to provide more accuracy in tracking.
How many different ways may a pilot de-couple or disengage the FD?
3 - SBY push button on the MSP,
FD disengage button on the cyclic, or
the COUPLE push button on the AFCS panel.
What must be functional in the AFCS system to allow coupled flight?
Must be in ATT mode .
In order to have ATT mode available:
(2:1 rule or “rule of 3”)
1 PSAS with both AP with cyclic and yaw trim or Both PSAS with 1 AP with cyclic and yaw trim
For ALT hold: Collective trim is also required.
What is the maximum rate of climb that may be commanded by flight director
2100 fpm
Are both AHRS information sent to both AP?
Yes,
The AHRS outputs are averaged and sent to both AP.
Same with the ADC.
In the event the AFCS can’t determine which AHRS is going bad what will it do?
The AFCS will turn off ATT mode and turn on SAS mode.
You may recover the ATT mode by determining which AHRS is bad and deselecting the associated AP. Then reselect ATT mode.
The AFCS will not accept AHRS reversion while in dual AP mode.
MTM
The DCL function brings the airspeed down to _____knots at the runway and ___ft RADALT.
60 knots
50 feet
At the bottom of the glideslope, the auto level function captures the radar altitude at 50 AGL even though there is no RALT mode on the MSP selected.
What does ATT mode provide?
with FD decoupled
Attitude hold for pitch, roll and yaw.
Heading hold/turn coordination.
(you can see when these are operating on the health page)
Collective trim beep is simply a position control without the FD coupled to Altitude.
Can you hand fly an ILS using only the collective?
Yes
The collective “heading trim switch” sets half standard rate coordinated turn, so anticipate turns. The collective trim release allows descent on the glide slope.
