Qavion2

Here's a 747-400 display after a 4 hour flight... Note that the display (from the FMC) heavily favours the GPS position ">-O-<" and nav radio updating, not the IRU "weighted average". If one IRU wanders too far off, it will be ignored, and not used as part of the weighted average.

Strange. That was my understanding of how it worked. The official nav databases have an ILS-DME offset value and they have been incorporated in at least one high end desktop sim. If anyone is going to notice this, it's light aircraft pilots. Do you normally get 0.0nm at the glideslope transmitter? (allowing for the distance from the runway to the ground antenna).

Since they are forward of the main landing gear, it's probably best to have your gear up to prevent interference. I'm wondering if the original poster still had his langing gear lever down when he got the glideslope alert? As far as I can see, there should be no alert with the gear lever up (or off). The DME component of the glideslope ground transmitter is probably omnidirectional (as well as the receiving antennae). Caution must be used when using ILS-DME. DME transmissions contain an electronic offset to compensate for different ground antenna locations (with respect to the runway threshold). i.e. the transmitter may alter the response time delay to compensate for the antenna location. Depending on the relative position of the aircraft in relation to the antenna, you may get a substantial distance error.

My books specify a front course. This surely means the GPWS is just as smart as the PFD displays. The GS needle won't show on the PFD for intercept angles greater than 90 degrees to the front course. The indications will probably be so erratic after passing the transmitter (relying on reflections from ground objects), it wouldn't generate a warning. How many cockpit landings can you find on YouTube where the G/S pointer remains in view past, say, the mid point of the runway? Engineering 747-400 manual quote: Mode 5 is armed when the airplane descends below 1000 feet RA, the landing gear is down and the localizer is captured (within 2 dots) before descending below 500 ft. To rearm mode 5, the airplane must either descend below 30 ft RA or ascend above 1000 ft RA. Heading Compare The backcourse compare circuit inhibits mode 5 annunciations during backcourse. The airplane is in backcourse when the angle between selected runway heading and magnetic track is greater than 90 degrees.

Even if the logic didn't need to be armed by the aircraft reaching 1000', there will be no usable glideslope signals in that scenario because of ground antenna design and fuselage/gear signal sheilding. The glideslope ground antenna (near the start of the runway) is designed to only work in one direction and even if it wasn't, since the aircraft receiving antenna is mounted on the nose, the ground station signal would have to go through up to 70 metres of metal fuselage when the aircraft is flying in the wrong direction. Not applicable in this case, but my books say that the warning logic needs to see the aircraft flying on an ILS front course. If, for example, you are using a runway where the ILS frequency is the same in both directions, you will need to be flying in roughly the same direction as the runway course you have selected on the Nav Rad page before you get warnings.

I believe the key is found in the arming conditions for this mode. The aircraft must descend through 1000ft ra (with the gear down) The GPWS computer probably monitors the changing altitudes and only arms this mode if the aircraft is seen to be descending through 1000'. Similarly, the altitude callouts need to be armed by the aircraft climbing above a certain height. This prevents nuisance height callouts during climb. The maintenance manual checks for the G/S aural begin by simulating a starting altitude of 1500ra. Reference 747-400 AMM 34-46-00-865-099-001 Section (i) Mode 5/Mode 6 Configuration Test. Hope this helps. (I don't know if this arming is modelled in QOTSII)

Sounds plausible to me, too. I haven't heard the A/T aural simply by putting the switch to OFF on the ground. There would have to be at least an active mode shown on the PFD FMA. There are a few airlines which only arm the A/T just before entering the runway for safety reasons. My old airline wasn't one of these. The odds of the TOGA switches being pushed accidentally are pretty remote (and easily cancelled).

The 60' callout is a famous option requested by Cathay Pacific (when they flew into Kai Tak). You can hear it just after 4:00 in this YouTube video:

Similar proportions to ours. I was also looking at the BA schematics (I think everything after G-CIVB has the newer system). By "checking the doors", I meant by pushing the alternate switches in the cockpit (not by climbing in the wheel well 😛 ). The doors can still trap your arm in freefall if you're in the wrong place. I'll continue my struggle to analyse the circuit. My biggest problem is understanding how the internal and external microswitches attached to the motors influence the relays at specific times. Thanks, Cheers, JHW

Paul, do you know if this applies to those aircraft which have a reset system which keeps the alternate gear motors running through a full cycle even if you prematurely put the alternate gear extension switch back to off? A maintenance manual procedure (32-35-00 p501~) mentions pulling the alternate gear extension reset circuit breakers in the Main Equipment Center prior to doing alternate gear extension door checks. Does this mean that the system fitted to newer aircraft (and retrofitted aircraft) inhibits door opening? Or does pulling the CBs allow the correct parts of the circuits to be checked? I had a look at the wiring schematic, but I can't make any sense of it. The same maintenance procedure (above) mentions moving the lever to OFF prior to checking the doors. I can't see the point of this. Doesn't the alternate gear extension cable system position the hydraulic valves so that hydraulic power doesn't impeded the door opening/gear deployment?

Sorry, no. The lights should work in both the configurations you mentioned. I would submit a ticket.

The 777 does have these white COMM messsages related to the FMC. Have these been incorporated into the 744 software? Or is this only on the 747-8?

My photo was taken in 2013.... Who knows 😋 (EDIT: A QRH dated 2015 shows "FMC MESSAGE")

There was a Boeing Service Letter 747-SL-31-092 (8 Nov 2010) which mentioned this: Do they mean the NG software? And does it apply to those aircraft which don't have new FMCs? Surely they didn't have NG FMCs back in 2010?

Is "FMC" (alone) a message?

Is the problem related to main deck cargo power? Are you touching the EXT PWR #2 or APU PWR #2 switches on the overhead panel. See the "Why isn't my cargo door opening" sticky thread. Cheers JHW

Indeed it has... and it has been messy.... the panels literally explode and the shrapnel can go everywhere. Fortunately, the pieces are lightweight and the damage is usually limited to scratches and small dents and perhaps some wiring damage. I have heard it is audible in the cabin (perhaps not the explosion, but the sudden change in pack behaviour when the affected pack air exits the aircraft instead of going to the cabin).

The packs must be turned off prior to the connection of conditioned air (and left off). There is a one way (check) flapper valve on the conditioned air connection (see diagram). Conditioned Air setup If the pack output pressure and the conditioned air pressure are roughly equal, the valve may open and close rapidly. We believe this causes premature failure of the valve hinge. We have found the valve flapper detached and stuck downstream of the connection. This may cause air to be diverted into the body fairing panel area and blow out the panels (The panels are of relatively thin composite material... and will not survive the pressurisation forces (which the packs are generating). Also, if the valve is not noticed to be missing, the pack may reverse pressure the ground conditioned air ducts and damage the ground air compressor. The pilots must tell the engineers downstairs if they intend turning on the APU and packs (so the engineers can remove the conditioned air hoses).

P.S. Note: There may be airlines with hydromechanical CWT scavenge systems, but still only use the #2 aft boost pump to feed the APU.

From memory, it has exactly 10 turns end to end, but that would be good if you could check it. It's shown as a simple potentiometer in the wiring schematics rather than a "rotary encoder". interesting. I can't say I've ever seen a 744 which had both an electric scavenge system and dual tank APU feed. The electric scavenge aircraft are easy to spot because they have a manual scavenge switch on the overhead panel. I assumed that if the #2 aft boost pump (only) fed the APU, fuel usage would be compensated for later in the flight by the CWT electric pump scavenging fuel from the CWT into the #2 tank. Hydromechanical pumps put scavenged CWT fuel into both tanks, so this seems a natural match to the dual boost pump feed system. If you can find an aircraft in your fleet with both an electrical switch on the overhead maintenance panel and two aft boost pump lights extinguished during APU ops, please let me know. Thanks! Cheers JHW

Just a few questions and tips (if you didn't already know)... 😉 I've noticed in the past that our flight crews make sure the Jettison Fuel To Remain knob is wound fully anticlockwise. Do you have any procedures like this? Do you take note of which PRESS lights remain not illuminated on the Fuel Panel? This could give you a clue as to what type of CWT scavenge pump system has been fitted (hydromechanical or electrical). Do you normally check to make sure that the LDG ALT PUSH ON button is not active (by checking the Upper EICAS indications?) Is the autoland status indicator (beneath the RMI on the captain's panel) checked during this particular panel scan, or is it done earlier? A few tips: Leaving Pack #1 on gives a better airflow to the cockpit (There are baffles in the pack plenum to direct most of pack #1 air to the cockpit). With another pack on, the air will find its way around the baffles, but at a slower flow rate). I have noticed that, on rare occasions, flipping the guarded toggle switch covers closed, doesn't always move the switch to its intended position. Fortunately, in most cases, the EICAS gives you warning of wrong positions. Sometimes I move the switch independently of the guard, then close the guard, especially with the stab trim cutout switches. On passenger aircraft, selecting the PA receive button is a good tip (even though your Cabin Interphone Panel should advise you that PA is in use). Cheers JHW

Setting it to GMT saves you from having to change your clock when daylight savings starts/ends 😉 True, if you don't fly to those European airports in Finland, Greece, Latvia, Estonia, England, Portugal, Ireland, Scotland, etc.

More great tips, thanks! I like the one about the rotary light switches (I could never remember those). I just noticed that your printer paper is getting a little low (the indicator is close to empty and the red stripe is showing on the paper) 😉

I'm not sure what kind of fluid they put in the windshield washer bottle. I'm wondering if it has any antifreeze in it. In this case, we won't want the people on the tarmac to have any contact with it.

Unusual rainshower ... or if we were too lazy to grab a bucket from the toolcrib or pushed for time, we'd use leftover bottles of water from Business Class. A more expensive improvisation (but not nearly as expensive as delaying an aircraft departure). Unfortunately, we had no control over who got wet on the tarmac below 😊