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Guest 747Skipper

CTD on GA

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Guest 747Skipper

Hi,I have a rather intriguing problem, and I suspect it is related to a larger problem.The larger problem relates to Cat.III autolands that fail on flights where VNAV wasn't used, and the FMC wasn't programmed with a route (just using VOR-to-VOR navigation).In that scenario, when FLARE commands idle power, it fails to idle properly, instead retarding the power to a distinct 66% N1. At ROLLOUT going active, instead of the AT system soft-disconnecting, SPD becomes the active mode, and AP just holds the flare pitch, resulting in it just floating down the runway 1ft off the deck.If during this exact configuration TOGA is hit, it results in a CTD. If it is not in this specific config, the CTD does NOT occur.Over at the other forum someoner else tried the failed autoland and they too could reproduce. As for the CTD, no-one would try.I have the latest updates installed, and the sim and the install are fine. My comp is fine, as is the install of FS.To re-create, put the 744 at the end of RW27R at EGLL. Don't program the FMC with a route, except for the weight data required for the TO speeds, and tuning up the ILS. Fly a hand-flown circuit. Use the AP for the autoland. It should fail to land properly.I can re-create this at will, and on shorter flights where I would like to use the FMC and VOR-to-VOR navigation to hand-fly the whole way, is very annoying.Does anyone have a work around for this issue (apart from programming and using the FMC?)Best regards,Robin.

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Guest Just747-400

Unfortunately I will not be home for at least one week to test that scenario.To answer to your question, that is wrong, the airplane should do an auto land without any problems. Actually we go in some airports not being part of data base and there are no problems. My question would be if this happens only at this airport and only for this rwy.Would you be so kind and try at least 3 x 4 different airports and report back, also some pictures will help. In this forum is much easier posting pictures.

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Guest neeraj.pendse

Hi Robin,I tried to reproduce your problem, and it did not appear. One big question for you I had was- without a route, how did you manage to select an ILS Freq in the first place?Here's my comments and how I did it:1. Started cold and dark at KSEA-34R2. FMC Setup: INIT Ref, Weights and V-speeds only. Also entered cruise alt of 3,000.3. On downwind: attempt to manually select 110.30/340 for ILS failed.4. Put in KSEA for arrival/ departure airports, DID NOT activate route.5. Went to departure page, selected KSEA 34R arrival6. RAD NAV page DID NOT tune ILS automatically.7. Went to RTE page, and hit Activate, Execute8. Voila! I have ILS autotuned in RAD NAV.9. Selected VREF... now on hand flown visual approach, final at 200kt, 10 deg flap.10. Engaged A/P for the first time (HDG HOLD, ALT-2000)11. A/P kept disconnecting a couple times12. Engaged A/T at 185kt, DID NOT MAINTAIN SPEED although engaged. (needs further analysis -> maybe I forgot to hit SPEED on MCP?)13. Engaged APPCH mode, it was selected on standby in the PFD Now we are deccelerating (A/T does not work, probably my fault) But LOC and ALT are active, G/S capture coming up14. As soon as G/S mode became active, A/T went to "MCP Speed" Now flying the G/S nicely at 185 kts.15. Dialed MCP down to 160 kts16. Engaged AP2,3 -> now in LAND3 Mode, ROLLOUT and FLARE are standing by.17. At 100 feet, aircraft started pitchup, then reduced power to idle -> Banged on the runway at about -400 ft per minute.18. Rest of the rollout was fine. Did not initiate G/A19. Pics are attached.- Neeraj Pendse(Happy to be back on AVSIM)

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Guest 747Skipper

Hi,It occurs anywhere in the world on any RW that has an ILS and I haven't used the FMC to actually fly the route. I just used EGLL as an example as it is my test airport.Regarding the cruise alt - I couldn't figure out what this had to do with the problem of the failed Autoland. If you enter a cruise alt (e.g. 3000ft) but do NOT make 3000ft, even if you fly through it, it does not consider itself to be in the cruise, or to have ever made cruise. ???????How does the real FMC decide it had reached "cruise", or is this yet another very subtle item that is inaccurate? You can see what mode it *thinks* it is in pressing INIT REF - if it shows the TO thrust and CLIMB settings, even if you are on downwind and have been stable at an altitude (even using the AP ALT HOLD mode) it doesn't consider itself to have reached cruise. Is it based off altitude maybe??I'll have a look at that and report back (again, NOT programming the FMC).I was wondering if the failed autoland was based off the fact that "NO TDZ" is displayed just below the altimeter tape. It didn't make sense that this HAD to be programmed in, and the fact that you can land at any airport not in the database confirms that thought (I was already aware aircraft in the RW could operate at airports not in their databases, but hadn't applied that thought to this particular problem). :)Here are two screenshots showing the system just after wheels initially touched down, and just before it commenced floating:http://www.antarctic-networks.co.uk:47392/...744-rollout.jpgIt will hold this pitch angle and float like this until intervention is made. To hit TOGA now would result in an instant CTD:http://www.antarctic-networks.co.uk:47392/...744/b744-15.jpgThis is where it CTDs when you hit TOGA whilst floating as above:http://www.antarctic-networks.co.uk:47392/.../PMDG744CTD.jpgBest regards,Robin.

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Guest neeraj.pendse

Hi Robin,[1] I still did not understand how you manage to program the ILS into RAD NAV without having the dest airport in the FMC. It seems to me that it should be possible (because otherwise one will not be able to land in airports which are not in the aircraft's data base) ... I just do not know how to do it. Can you tell me?[2] One difference I noted between your pictures and mine is that during ROLLOUT, you have SPD selected on the MCP -> I don't.Back to some trials and will see ...- Neeraj.

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Guest 747Skipper

>Hi Robin,>>[1] I still did not understand how you manage to program the>ILS into RAD NAV without having the dest airport in the FMC.>It seems to me that it should be possible (because otherwise>one will not be able to land in airports which are not in the>aircraft's data base) ... I just do not know how to do it. Can>you tell me?>Press RAD NAV on the FMC, then enter the ILS freq/Course into the scratchpad e.g.: 110.30/273 then line select PARK (or the already existing ILS freq). I think it is LSK4 (note: NOT LSK1 or RSK1).>[2] One difference I noted between your pictures and mine is>that during ROLLOUT, you have SPD selected on the MCP -> I>don't.>PRECISELY!!!!!!!!!! On a correctly proceding autoland, SPD shouldn't be there at all; no speed mode should be active. It should be blank, leaving ROLLOUT on its own.Before touchdown/flare:SPD | LOC | GS << GREEN | ROLLOUT | FLARE << WHITEAt the flare (before touchdown still). I do NOT see this when FLARE goes active on a failed autoland:IDLE (in white) | LOC | [FLARE] << GREEN | ROLLOUT | << WHITE.....instead I see (INCORRECTLY):SPD | LOC | [FLARE] << GREEN | ROLLOUT | << WHITEAND....... on a FAILED autoland, it then proceeds to do THIS:SPD | [ROLLOUT] | << GREEN | | << ALL FIELDS BLANK (correct)instead of: | [ROLLOUT] | << GREEN | | << ALL FIELDS BLANK (correct)which is what it SHOULD do.It fails to activate IDLE as the speed mode, and de-rotate. Instead it is holding the flare pitch etc. When ROLLOUT goes active, the speed mode (IDLE) should disappear leaving a blank for the speed mode but SPD remains active thorughout. The AP continues to hold the FLARE pitch, and doesn't derotate the aircraft.If it fails to autoland correctly, and I simply kill the AT and idle the power manually, it STILL tries to maintain the flare pitch, only de-rotating when it effectively stalls and the nose drops due to gravity. During a normal autoland, this does not occur.>Back to some trials and will see ...>Indeed. I hope you can re-create it, because then we might be able to work on a work-around, or more accurately, find the fail condition so we can tell PMDG what it is they need to fix.The only things you did different to me (from your explainations) were:* Programmed in a route IN FLIGHT* Selected a DEPARTURE RW in flight (?)* Activated the ROUTE (in flight!)EDIT: > 16. Engaged AP2,3 -> now in LAND3 Mode, ROLLOUT and FLARE are> standing by.Really???? When I press APP, all 3 APs go active. Hmm!! A bug at this point here??? How did you make it so that YOU had to select all 3 APs??? In PMDG -> Options menu? I'm trying this now!! :DBest regards,Robin.

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Guest neeraj.pendse

OK I am dumb. I was not putting the "" last time! Now I have the ILS tuned in and V-SPEEDs but NO other FMC Setup ... will report back in 15 min what happens.

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Guest 747Skipper

Great! Thanks!! :)Best regards,Robin.

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Guest neeraj.pendse

OK Robin,I confirm! 66% thrust on ROLLOUT. Flare goes fine, but EICAS shows "GA" after touchdown. So far, to summarize:* Problem occurs when FMC does not know which airport and runway it is landing at.* Whether or not ILS is manually tuned, if the FMC knows the airport and runway, there is no problem.* No TDZ is displayed on the PFD.* A/P is in ROLLOUT Mode, but:* A/T is in GA mode, and comands SPD.* In absence of pitch up from A/P, only partial throttle is needed to maintain VREF without climbing.* Beats me why exactly 66% throttle. We both must have different weights, I was 635K pounds.I was hoping to understand what is going on by looking at replay. But it seems not all variables are set correctly in REPLAY, so I need to make another flight.Later,- Neeraj.

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Guest 747Skipper

Hi,That is the weird part - it always targets 66%!!!I've been very light and heavy, and it alays targets that specific thrust setting, using whatever elevator trim is required to hold the pitch and remain 1ft off the floor. VERY odd!!Thanks again for trying! :) I'm going to try programming in the destination and arrival RW to remove No TDZ from the PFD.BRB! :)Best regards,Robin.

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Guest 747Skipper

Hi,I programmed a dept airport (EGLL) into the FC, selected the arrival RW, activated the route, got rid of the No TDZ message, and it still failed to autoland properly.Best regards,Robin.

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Guest neeraj.pendse

Hi Robin,I flew a circuit at EGLL with full FMC programing and the autoland went OK, except that the aircraft flares too late IMHO, and hits the runway at -500 fpm. This time it even bounced once!I do not remember why I had to activite all autopilots manually one time -> do not remember the conditions now.- Neeraj.http://forums.avsim.net/user_files/132829.jpghttp://forums.avsim.net/user_files/132830.jpg

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