No Flight Director when onside autopilot is in control - behaviour in autoland

[Sylle]

Hello |-|ardy,

Using the PSX model option 'no F/D if A/P on same source' I noticed the following which I would like to clarify.

Using the L AP in flight results correctly in not having the FD displayed on the captains PFD.
Same for the F/O side when using the right AP.

However, the onside F/Ds do appear on the PFD when all 3 autopilots are engaging below 1500ft AGL with LAND3 annunciation.
Is this behaviour correct??

I was expecting the opposite - having the F/D's disappear on both PFD's during the time all 3 FCCs are controlling the autoland maneuver...

Regards,
Sylvain

[emerydc8]

I'm not familiar with the variations on this and I suspect they are largely airline-dependent, but I understand that United has this feature where you either see the F/D with no A/P, or use the A/P with no F/D in view. I looked at their FCOM and it looks like their setup is for neither F/D to give any guidance. But this may just be one airline's preference.

FLIGHT CONTROL COMPUTERS
The three flight control computers (FCCs) integrate the functions of the autopilots and flight directors. Each FCC sends control signals to its respective autopilot control servo which operates the flight controls through separate actuators powered by hydraulic systems 1, 2, and 3.

The FCC also sends signals to the flight director command bars on the PFD. Any one of the FCCs can perform all the AFDS functions except autoland, which requires at least two autopilots. Flight director commands are not available during triple autoland operation.

[John H Watson]

Strange... I'm sure this was working during beta tests. It was a feature in PS1 days, too. Has one of the updates affected the F/D's behaviour?

[Britjet]

Presumably airline-specific. BA system doesn't behave in this manner. FD appearance is independent of Autopilot selection.
Peter.

[Sylle]

It is indeed a customer option that has not been very popular amongst airlines Peter. Hardy was so kind to provide it in PSX though...
United is the most famous operator to have this option.
They also have to manually engage the two remaining autopilots after pressing APP to do an autoland. Also something you do not see in many other airlines...

Regards,
Sylvain

[Sylle]

I'm not familiar with the variations on this and I suspect they are largely airline-dependent, but I understand that United has this feature where you either see the F/D with no A/P, or use the A/P with no F/D in view. I looked at their FCOM and it looks like their setup is for neither F/D to give any guidance. But this may just be one airline's preference.

FLIGHT CONTROL COMPUTERS
The three flight control computers (FCCs) integrate the functions of the autopilots and flight directors. Each FCC sends control signals to its respective autopilot control servo which operates the flight controls through separate actuators powered by hydraulic systems 1, 2, and 3.

The FCC also sends signals to the flight director command bars on the PFD. Any one of the FCCs can perform all the AFDS functions except autoland, which requires at least two autopilots. Flight director commands are not available during triple autoland operation.

Thank you emery for this United FCOM extract! I think that answers my question

Our company used to operate an ex-Varig 767-300 that also had this option 'no F/D on the side of the engaged A/P'.
To keep the F/D in view on both EADI's we always flew with CTR autopilot engaged.
I remember clearly that during an autoland both F/D's would disappear below 1500ft AGL but I was not sure the 744 would behave the same way...

@|-|ardy, any chance to get this correction on your to-do list please?

Regards,
Sylvain

[John H Watson]

I believe it's an option selected by not shorting a Flight Control Computer "program pin" to earth:

The option is labelled "Full Time F/D" (The F/D command bars are displayed if either or both flight directors are turned on regardless of A/P channel engagement. Some books mention F/D inhibit with single channnel flare under the same option title)

They also have to manually engage the two remaining autopilots after pressing APP to do an autoland. Also something you do not see in many other airlines...

I believe a number of options were selected by grounding a single pin on the back of the FCC. i.e. if you had one unusual option... it included other unusual options, too 

[emerydc8]

Thank you emery for this United FCOM extract! I think that answers my question

Our company used to operate an ex-Varig 767-300 that also had this option 'no F/D on the side of the engaged A/P'.
To keep the F/D in view on both EADI's we always flew with CTR autopilot engaged.
I remember clearly that during an autoland both F/D's would disappear below 1500ft AGL but I was not sure the 744 would behave the same way...

Sylvain,

Ironically, I am going over to the 767-300ER next month and the aircraft my company operates are also ex-Varig (s/n 24752 and s/n 24753). I am told that they got the 744 MCP approved, so we at least have altitude intervention, but since I haven't been in the airplane yet, I don't know what to expect. I am pretty sure it's a different setup than the Boeing sim in MIA, so I'm not too excited about that.

They just bought three more and are ferrying them over from Spain.

Jon

[Jeroen Hoppenbrouwers]

Any one of the FCCs can perform all the AFDS functions except autoland, which requires at least two autopilots.

Does anybody know whether the two required autopilots cannot individually perform all computations for autoland and in some way need to combine resources, or this is all 100% regulatory and only a safety measure to increase the chance that a failing FCC will leave a good one active to complete the autoland?


Hoppie

[Sylle]

Oh Jon, really? You're leaving the 744?? Curious to hear how you will like her smaller sister the 763...

Ours was s/n 24844. Apparently with so many flight hours it wasn't even interesting to convert to a freighter at the end of the lease. It sadly got turned into sardine cans!

Yours are even older but probably with less hours/cycles on the frame. Hope they will treat you well!
Do they already come with the improved Pegasus FMC?

Good luck with the training!
Sylvain

[Jeroen Hoppenbrouwers]

\o/ Pegasus!  One whole megabyte nav database memory! Nobody will ever need more than that!

Just done configuring a few 767-300ERs for Icelandair. These airframes easily get second and third lives.


Hoppie

[Hardy Heinlin]

With this United option, I think in autoland the FDs were displayed in PS1 too.

I didn't know, or I forgot, that they should be removed in autoland too. OK, I'll try to modify this, and I hope United will sell at least some of their remaining 744s to active operators, and that these operators will keep that option!

What is really new to me is the option for autoland that requires the crew to engage the three A/Ps manually. Is this option linked with the option above or a separate pin?


|-|ardy

[emerydc8]

Hardy,

Maybe this engaging the second and third A/P was a carry-over from the classic. On the classic, you had to have one A/P engaged and then select LAND on a rotary switch, then engage the remaining autopilots. Could Boeing have decided that this monkey-motion could be simplified with the 744?

Sylvain,

Our airplanes have the Pegasus package; so I got that going for me . . . which is nice.  Actually, I'm looking forward to not having to deal with all the problems that come with international flights, not the least of which is augmented crews and 30-hour duty days. I think flying widebodies domestically is the best of both worlds.

Jon

[John H Watson]

I believe a number of options were selected by grounding a single pin on the back of the FCC. i.e. if you had one unusual option... it included other unusual options, too 

False alarm. There were confusing pin names...

In the Maintenance Manual, there was a mention of  "FCC OPTION 2" (which included the individual CMD button engagement, Full Time No Land 3, GS Capture Inhibit and a few others)

In the wiring diagrams was "CUST OPT PIN 2" (a single pin) which I assumed was the same. It isn't. After further investigation, the individual CMD button engagement option has its own unique option pin "G13".

[Hardy Heinlin]

Thanks!

I assume ...

... if this pin is set, and one A/P is engaged and the RA is > 1500 ft and APP is selected, the other two CMD switch lights won't illuminate (if this pin is not set, they will -- to indicate they are armed).

... if this pin is set, and the RA is > 1500 ft and APP is selected and three CMD switches are pressed, all CMD switch lights will illuminate (the first pressed one being the engaged and post-TOGA-single-channel A/P, the other two being the armed A/Ps).

... if this pin is set, and the RA is <= 1500 ft and APP is selected and three CMD switches are pressed, all A/Ps will engage (the first pressed one being the engaged and post-TOGA-single-channel A/P).

Does anyone disagree?


|-|ardy

[John H Watson]

Maybe this engaging the second and third A/P was a carry-over from the classic. On the classic, you had to have one A/P engaged and then select LAND on a rotary switch, then engage the remaining autopilots. Could Boeing have decided that this monkey-motion could be simplified with the 744?

Some early 767's had 3 mechanical paddles for A/P engagement (like the Classic 747). You can select one paddle, but the other two would have to be engaged manually.  You can fit some Boeing 767 Flight Control Computers to 744s....  so I (wrongly) assumed the option was only there for the 767.

Ironically, I am going over to the 767-300ER next month

It's hard to believe the 767s are still flying around... When I left my old company, I think we only had one left.. and that was for cargo ops. Do the Varig aircraft have FADEC engines?

Does anybody know whether the two required autopilots cannot individually perform all computations for autoland and in some way need to combine resources, or this is all 100% regulatory and only a safety measure to increase the chance that a failing FCC will leave a good one active to complete the autoland?

It's only a safety thing. Each FCC has it's own set of single data sources (Rad Alt, ILS, IRU, etc). However, if you have 2 or 3 computers, they can provide redundancy and talk to each other, sharing and comparing sensor data and  providing mechanical "voting". It's not like FCC Left controls the ailerons, FCC Right Controls the elevator and FCC Centre controls the rudder. All 3 A/Ps are doing the same jobs during autoland (although the first A/P in command may have an extra function or two)

[John H Watson]

... if this pin is set, and one A/P is engaged and the RA is > 1500 ft and APP is selected, the other two CMD switch lights won't illuminate (if this pin is not set, they will -- to indicate they are armed).

Currently reading a manual for the 767 with this option...

Things to consider... Autoland Bus Isolation won't happen until all three switches are pushed.

Can we assume that the first in command doesn't need to be in, say, LOC engaged mode before the other A/Ps are allowed to be armed?

From the 767 manual..

Pitch Channel - Autoland
(a) Autoland status can only be achieved when two or more A/P channels are armed with APP selected. One channel must already be in approach command to initiate multichannel autoland. Each additional A/P engage switch must be manually selected. The switches remain in CMD only if APP is selected.The Autoland Status Annunciator (767 thing) shows channel engagement. The ASA display indications assume FULL TIME NO LAND 3 option is active. ()
Pitch Multi-Channel Engage
1) Pitch multi-channel engage occurs at 1500....

[Hardy Heinlin]

I assume the APP light being illuminated is the only condition to allow the other A/P's to be armed. It's already illuminated when LOC and G/S are just armed, and not engaged yet.

Actually, the LOC mode is irrelevant. G/S is the only feature that turns a simple LOC mode into an APP mode. In other words: The other A/Ps can be selected when G/S is armed or engaged. Are you assuming the same?

[emerydc8]

Our 767s have the same logic as the 744 -- With an A/P engaged, pushing APP arms the remaining two.

It's hard to believe the 767s are still flying around... When I left my old company, I think we only had one left.. and that was for cargo ops. Do the Varig aircraft have FADEC engines?

We do have the FADEC engines. There seems to be a renewed interest in the 767 at least within the US domestic cargo market. Amazon will be operating 40 767s for their new hub in Wilmington, Ohio. FedEx, UPS and DHL all seem to be expanding with the 767.

[Jeroen Hoppenbrouwers]

I suppose that for about the same age airframe, you buy two engines less with a 767 compared to a 747 and that's what drives the math. A 747 with two engines would be what they really wanted...


Hoppie