The autopilot mode control panel on the Lockheed L-1011 is split into four (4) different component pieces. The panel shown in this posting is the NAV MODE panel. It controls the navigation mode of the L-1011 autopilot.
The selectable modes are:
A/L .... Auto Land
APR .... Approach
LOC .... Localizer
NAV .... VOR capture and tracking.
Here is a more detailed description of the modes taken from an Eastern Airlines Flight Manual:
A/L - The APFDS is armed for approach and autoland when either one of both autopilots are engaged and ILS frequency is selected. LOC ARM, GS ARM and A/L ARM appear in both AFCS mode annunciators. Usable as CAT-II or CAT-III operation with dual A/L or CAT-II with single channel A/L including autoland.
APR - Arms APFDS for capture and tracking of localizer and glideslope of CAT-I quality. LOC ARM and GS ARM appear in both AFCS mode annunciators. ILS frequency must be selected.
LOC - Arms APFDS for capture and tracking of localizer. Glideslope capture not available. LOC ARM appears in both AFCS mode annunciators. Not usable for back course approaches.
NAV - Arms APFDS for VOR capture and tracking. VOR ARM appears in both AFCS mod annunciators.
The COURSE SELECTOR KNOB - Sets No. 1 VOR receiver or No. 2 VOR receiver to desired course. Positions course pointer on captains and F/Os HSI. Provides VOR or LOC course reference for APFDS A and B. When set to an ILS course, provides heading information to computer for wind data integration, localizer capture, and runway alignment.
The VOR SELECTOR SWITCH has the following positions:
SPLIT - APFDS A receives signals from NAV1 radio; APFDS B receives signals from NAV 2 radio.
1 - Both autopilots receive signals from NAV 1 radio.
2 - Both autopilots receive signals from NAV 2 radio.
If A/L, APR, or LOC mode is swelected, the VOR selector switch automatically returns to SPLIT. The HSI is always refereenced to individual receivers unless the ALTN DEV switch is actuated.
The RADIO/NAV switch selector switch location on the glare shield:
Panel Location
Since the VOR selection is always in SPLIT mode when an ILS mode is selected, how does the autopilot know which signal to use if the two VHF radios are tuned to different ILS frequencies?
ReplyDeleteLOC or APR mode is selected by tuning at least one of the ILS receivers to the airport localizer frequency, setting in the localizer course with the course knob and pressing the LOC switch, for example. From what I have been told, if both ILS receivers have a valid signal, the one associated with the autopilot channel is chosen. This blog posting here might make it a little easier to understand:
ReplyDeletehttp://l1011project.blogspot.com/2011/07/l-1011-autoflight-localizer-arm-capture.html
Ah, I think I may have worked it out, so please let me know if I'm thinking along the right lines...
ReplyDeleteI was confused because you need BOTH autopilots on in order to do a Category II or III autoland (so given that the VOR selection is forced into SPLIT, it is unclear which VHF radio is used).
But now I realize that since it is only possible to switch on a second autopilot AFTER autoland mode is engaged, then presumably the VHF radio for whichever autopilot was switched on when autoland mode was first engaged would be used, right?
That's right. The radio head actually has an ILS annunciator on it.
ReplyDeleteDoes the SPLIT/1/2 switch also determine which VOR signals are displayed on the HSIs? Presumably then in INS mode (which you said was also on this switch on INS-equipped L-1011s* with the analogue autopilot), the HSIs would display INS data instead of VOR data then?
ReplyDelete*I'm surprised INS wasn't standard equipment for the L-1011 -- I assumed it was for all wide-body jets.
George, according to the documentation the NAV SOURCE switch is only relevant to the autopilot and not the HSIs. Each HSI has a set of switches that allow the source control for the HSI. However, the course select knob on the left sets the No. 1 VOR receiver to the desired course and positions the course pointer on the captain's HSI ... when that HSI is set to RADIO. The course selector on the right sets the No. 2 VOR receiver to the desired course and also positions the course pointer on the F/Os HSI ... also if that one is set to RADIO. If the NAV source is FMS or OMS (or any other INS source) then the two course selectors have no meaning because the heading is driven by the respective computer (FMS/OMS).
ReplyDeleteOK, where on the instrument panel are the switches which control the source for the two HSIs?
ReplyDeleteGeorge, I included two pictures for you in the original blog posting. See above.
ReplyDeleteThanks for that -- do those switches also switch between VOR and INS for the autopilot as well? I've seen photos of the flight decks of INS-equipped L-1011s with the original autopilot, and with no extra positions (other than SPLIT, 1 and 2) on the VOR selector switch...
ReplyDeleteThat is right. The switches also select between VOR and INS for the AP.
ReplyDeleteGeorge, you might find this here helpful when you program the AP for your flight simulator. Below is a descriptions of the activities and indicators during an approach and an ILS landing:
ReplyDeleteA) Approach Phase
1. Tune both(!) ILS's and set up inbound course with course knobs.
2. Set DH on radio altimeter
3. Set Flight Directors to ON (they should really already be on). Set the desired Autopilot to CMD mode
4. Use HDG Select to maneuver towards LOC capture
5. Use VS or ALT for a pitch mode while flying the aircraft towards the LOC intercept
6. Update the approach speeds in the IAS window as flaps configurations change.
7. Engage Autothrottles if not already on
8. Set the final intercept heading with the heading knob.
9. Select APR mode when cleared to intercept and heading within 60º of inbound course
The AFCS Mode Annunciator will show:
LOC ARM
GS ARM
HDG SEL
ALT (if ALT was set as the pitch mode)
B) The Localizer Capture
The localizer capture now happens automatic and the the HDG SEL disengages and the AFCS Modes now change to:
LOC
GS ARM
ALT
At this point the pilot is expected to update the heading to the inbound heading in the heading select window. This, however, has not direct impact on the already captured localizer but will be helpful in the case of a go-around or loss of the localizer.
C) Glide Slope Capture
Since the glideslope capture is already armed the aircraft will automatically pitch over to a 750FPM descent. Any selected pitch mode now disengages and the auto-throttle systems goes to ALPHA mode once 30º of flaps are extended. Now the Go-Around system is also armed ... however, there is no direct indication of that in the cockpit. The aircraft uses now DLC to hold the ALPHA speed. The AFCS Mode annunciator now shows:
LOC
GS
D) At Decision Height
At DH, as annunciated, the pilot will disengage the autopilot and ATS by pressing the AP Disconnect switch on the control wheel and will land the aircraft manually. Or, initiate a go-around by pressing the TO/GA switch.
How does the pilot cancel an autoland (other than by pressing the TOGA button)?
ReplyDeleteI guess the next way of canceling out of the Approach/Land (A/L) program is to disconnect the AP all together (press the AP Disconnect switch on the control wheel) and drop it from CMD mode into CWS mode or OFF state. Also A/L will cancel when both Flight Directors (F/D) are turned off.
ReplyDeleteWhat is an interesting behavior is that this will not disconnect the Autothrottle System, that has to be done as a 2nd step.
Also, does the original autopilot have any ability to follow a localizer back course? And if so, how is it engaged?
ReplyDeleteGeorge, sorry for the late reply. I am not aware of a BC feature in the original autopilot.
ReplyDeleteIf the Captain's NAV/RADIO switch is set to RADIO and the FO's switch is set to NAV, would selecting the Captain's ALTN DEV switch change the Captain's HSI from VOR 1 to VOR 2 while selecting the FO's ALTN DEV switch change the FO's HSI from INS 2 to INS 1 (if two INS units are fitted)?
ReplyDeleteOr would the Captain's ALTN DEV switch change the Captain's HSI from VOR 1 to INS 2 and FO's ALTN DEV switch change the FO's HSI from INS 2 to VOR 1?
I'm guessing it's the second...
What happens if an attempt is made to switch to LOC, or APR or A/L mode if either of both of the HSIs are set to NAV (INS) instead of RADIO? Will these modes be disabled, or will selecting one of these modes automatically switch both HSIs to RADIO (as well as setting the VOR selector switch to SPLIT)?
ReplyDeleteThe HSI receives data from many different sources at the same time. So for example, the HSI receives heading data from the primary system on one set of cables and data from the standby system on another set of cables. The switch that selects the ALT source for either the captain or the first officer switches the signals displayed within the HSI. The alternate source switches for the captain and the first officer are not combined, so selecting alternate on one site has no effect on the other. The ALT switches do not interact with any other aircraft systems but the actual displays.
ReplyDeleteSelecting a mode that does not require coupling of the two NAV sources will return the switch back to SPLIT.
ReplyDeleteI think you misunderstood my question -- my question is what happens when a RADIO-specific navigation mode (LOC, APR or A/L) is selected when the aircraft is currently using INS navigation. Does it switch the HSIs back to RADIO mode as well as switching the VOR selector switch to SPLIT?
ReplyDeleteI see. Yes I guess I did misunderstand your question. Sorry, I have no answer for you on that.
ReplyDeleteDoes autoland on the L-1011 retard the throttles to idle for the flare and deploy the reversers after touchdown?
ReplyDeleteHere is what happens on touchdown when in Automatic Approach/Landing Mode:
Delete- At touchdown, the automatic ground spoilers deploy.
- The ATS drives they throttles to ground idle, arranging the throttle linkage so reverse thrust can be applied manually.
- Aileron and rudder control inputs continue, with control emphasis shifting to the rudder. This control transfer is quite rapid when the automatic ground spoilers deploy.
- The nose gear is allowed to descent to the runway at a controlled rate (2º pitch per second) to avoid hard contact.
- The nose wheels will be aligned with the runway at initial contact even though the rudder pedals may be displace from center by the parallel rudder control inputs.
- Weight on the nose gear places the nose wheels under control of rudder pedal steering. Heading control is maintained through the parallel rudder control inputs as the rudder loses its aerodynamic effectiveness.
- At approximately 60 knots, manual control of the nose wheel steering should assumed.
- Guidance for directional control is provided by the HSI localizer and the expanded localizer in the ADI's when supplemental hand steering control, asymmetric braking or reverse thrust application is required.
Hope this helps.
Thanks for that, but what would happen if the pilot attempted to select A/L mode with the autothrottle off?
ReplyDeleteThe ATS and the Approach/Land mode are independent. The A/L will engage and expect the pilot to control the necessary airspeed pending on the fast/slow indication on the HSI in reference to the speed set in the IAS window. When the L-1011 is set to automatic landing the aircraft goes into ALPHA speed mode once LOC and GS has been established and the speed setting in the I/A window is no longer relevant. The speed in the IAS windows i covered with a blue flag and the word ALPHA.
Delete