>FUEL TANK/ENG

[downscc 1,327]

I recall during beta the discussions on delays built into various messages, not that I remember the specifics but the simulation detail is there.

[scandinavian13 5,192]

7 hours ago, Qavion2 said:

Perhaps the active pilots on the beta team can confirm this. i.e. the manuals agree with the real aircraft.

Confirmed as part of the beta process.

[Qavion2 39]

8 hours ago, scandinavian13 said:

Confirmed as part of the beta process.

And what did they confirm may I ask?

[scandinavian13 5,192]

11 hours ago, Qavion2 said:

And what did they confirm may I ask?

You were the one who asked if it was confirmed. I answered that it was confirmed. What kind of answer are you looking for here?

The trigger for the message displays in the same conditions as in the real aircraft, and we spent quite a lot of time getting all of the timing and conditions of the messages down. This is why the EICAS messages are saved in the panel state, otherwise, if you reloaded the state without the saved messages, the various messages would show up after the relevant wait time.

[Qavion2 39]

13 hours ago, scandinavian13 said:

You were the one who asked if it was confirmed. I answered that it was confirmed. What kind of answer are you looking for here?

 

I was just wondering which manuals the aircraft agrees with, since 99.9% of the manuals say "main tanks equal" and go no further. 

The problem is...  I don't know how the real aircraft behaves.  I don't know if this obscure wiring schematic logic manifests itself on the real aircraft or whether there is so much randomness in the fuel quantity indicating system, it's not possible to observe. Note that the Boeing wiring schematics call the message a Memo message, so that simply adds to the confusion. I'm sure the real aircraft doesn't agree with this (part of the) manual.

The wiring schematics say the first wing to have equal quantities (inboard and outboard) will generate the message. Unfortunately, I am at a disadvantage... I can't test various scenarios for myself because my computer is too ancient to run QOTS2 (even though I have a legal copy ready to go), At the moment I'm relying on third party information and YouTube videos regarding sim behaviour, so forgive the line of questioning.

Cheers

JHW

Edited April 21, 2018 by Qavion2

[kevinh 409]

The impression I got from Kyle’s response was that the pilots confirmed the sim operated like the aircraft. Of course what the FCOM says is simplified compared to actual schematics, so you wouldn’t expect references to time delays.

I’ve not actively tested the logic but I can say that 747v3 works exactly as you might expect with only the FCOM for reference. Unlike 747v2 which often displayed X FEED CONFIG after reconfiguring to tank to engine in response to the EICAS prompt. I suspect correctly including the time delays ensures this won’t happen. 

[downscc 1,327]

What Kevin said, and that PMDG, through the provisions of their license with Boeing, had access to engineering data and much more information than just the FCOM samples that we get as end users.  That and they had a pretty good group of pilots and mechanics on board the technical review team as well as RSR is type rated in the quad.

[berts 97]

On 13/04/2018 at 7:03 AM, Qavion2 said:

Kyle has a good point, but, if the team is not so busy... Someone on the Aerowinx forum said (about two years ago) that an FCOM had the following text:

Chapter 15
Alerts inhibited during take-off
EICAS advisory message TCAS OFF - inhibited on ground until 400ft RA.

Alerts inhibited during landing
EICAS advisory message TCAS OFF - inhibited from 400ft RA until go-around at 400ft RA.

A British Airways 744 pilot responded and said that he didn't get a TCAS OFF message in his company sim. Another 744 pilot (Atlas) commented that he had never seen the message on the ground. I also found a mention of it in an old Boeing Service Letter (circa 1998):

IDS software Update:

>TCAS OFF (Level C) Revised logic to inhibit the message if radio altitude is less than 400 feet.

It would be far easier for one of your real (current) pilots to check this than for me to look through hundreds of pages of Service notes. Also, if your pilot is from an independent airline, it would add a 5th reference.

Note that I have manuals which say the TCAS OFF message does appear on the ground, but they are well out of date. I also have a really old photo showing the TCAS OFF message on the ground during Standby Power only. This may either be because the photo was really old (pre-service bulletin) or because the relevant radio altimeters were not powered.

The comments on the Aerowinx forum were temporarily "muddied" because some of the manuals didn't specify if it was a takeoff inhibit or if the inhibit was in force at all times below 400feet. The big sim tests seemed to prove that it wasn't just a takeoff inhibit.

The EICAS message >TCAS OFF is not to be confused with the one on the ND (which does appear on the ground)..

Cheers

JHW

 

John, apologies for coming late into this discussion. 

I think we have to be very careful not to get too bogged down in the finer detail, because it is very likely that there may be different TCAS equipment and logic in use, depending on the airline as well as the age and type of B744 aircraft.  For example, some TCAS units have a 3 position selector switch to increase the height above and below the aircraft at which TCAS warnings may be generated (this is not currently modelled in the PMDG B744 QOTS, but in all other respects I have found the TCAS, PWS and EGPWS to be are very realistic when they do go off!).

Generally speaking, Alerts are inhibited when they are not appropriate or operationally necessary. They are inhibited during normal system operation and during part of the takeoff to avoid distracting the crew.   It is perhaps also worth stating that some EICAS Alert messages are inhibited if another related alert message is displayed, whilst others can be time delayed even though the related flight deck panel lights are illuminated.  For example, I have found the fuel system, pump and valve indications etc to be faithfully modelled in the QOTS II when compared to the B744's I am familiar with.

The TCAS OFF EICAS Advisory Alert message will display whenever the TCAS mode (RA/TA or TA) is not selected or is not operating. This means that there will be no TCAS RA guidance displayed on the PFD's, no TCAS messages or TCAS traffic symbols on the ND's and there will be no TCAS voice annunciations heard.  This statement applies whether PWS is fitted to the aircraft or not. 

During takeoff:  where PWS is fitted to the aircraft the following Alerts are inhibited on the ground up to approximately 1,000ft RA: All TCAS RA's and TCAS TA voice alerts.  In addition TCAS Descent RA's are also inhibited.

During Landing:   TCAS INCREASE DESCENT RA's are inhibited below approx 1,500ft RA and will end during a missed approach at approximately 1,500ft RA  (for TCAS DESCENT RA's the inhibit height is reduced to approx 1,000ft RA).  ALL TCAS RA's and TCAS voice alerts are inhibited at approximately 500ft RA and the inhibit will end when a missed approach is flown and the aircraft climbs above approx 500ft RA.

Hope this is helpful.

Bertie

Edited April 22, 2018 by berts
typo and addition

[Qavion2 39]

3 hours ago, berts said:

This statement applies whether PWS is fitted to the aircraft or not. 

Now things are really getting complicated. PWS is a seemingly independent weather radar-related system. I don't know if your manual reflects a general EICAS software change implemented on your fleet which happened to coincide with a new radar system fitted (which had PWS) or if there was a necessity to modify TCAS logic as a result of PWS being fitted.  What happens if the weather is perfectly fine and TCAS detects an impending collision?

Having said that, your TCAS aural inhibit heights seem relatively normal, irrespective of whether PWS is fitted or not.

Here's an extract from someone's maintenance manual (not mine)

C. TCAS INHIBITS
(1) When a ground proximity or windshear alert occurs, the TCAS will be set to the TA-ONLY mode
and all TCAS voice alerts are inhibited. [type of windshear alert not specified]
(2) All RAs are inhibited when the airplane radio altitude is less than 1100 feet if the airplane is
climbing.
(3) All RAs are inhibited when the airplane radio altitude is less than 900 feet if the airplane is
descending.
Aeroplane registrations XYZ, and ABC Post-service bulletin 747-34-2529*
(4) All audio warnings are inhibited below 1100 feet radio altitude during ascent and 900 feet during
descent.
Aeroplanes  XYZ, ABC, etc
(5) No TCAS "Increase descent" commands are given when the airplane radio altitude is less than
1450 feet.
(6) No TCAS "Descend" commands are given when the airplane radio altitude is less than 1200 feet
if the airplane is ascending, and 1000 feet if the airplane is descending.
(7) TCAS Climb RA commands are inhibited above a barometer altitude of 48,000 feet.

*Unfortunately, I don't know what the service bulletin relates to (other than it's relation to Navigation). The date of the manual (2004) seems pretty ancient. I can't recall when PWS was introduced to the 744.

Anyway, getting back on topic..

4 hours ago, berts said:

For example, I have found the fuel system, pump and valve indications etc to be faithfully modelled in the QOTS II when compared to the B744's I am familiar with

A pilot just commented on the PPRuNe forum that it's normal for the inboards to be slightly less than the outboards by 1~200kg about the time that TANK/ENG message appears. Can you say that this has also been your experience?

Another pilot found an additional line in his QRH (I checked and it was the same as ours).

*On the ground after refueling, after initial electrical power established, or after CMC ground test; main tank 2 quantity less than or equal to main tank 1 quantity plus 500 kgs and main tank 3 quantity less than or equal to main tank 4 quantity plus 500 kgs

I'm not sure what this is trying to tell us. Is it saying that, even with relatively low fuel loads (say, 10 tonnes in each tank) and the inboards are (less than) 500kgs above the outboards, that you will still get a FUEL/TANK ENG message? Is it possible to top up the tanks on the ground (prior to takeoff) with these values in QOTS II? M1=10.0, M2=10.4, M3=10.4, M4=10.0. In this configuration, does the FUEL TANK/ENG message appear?

Thanks,

Cheers

JHW

[Qavion2 39]

11 hours ago, downscc said:

What Kevin said, and that PMDG, through the provisions of their license with Boeing, had access to engineering data and much more information than just the FCOM samples that we get as end users.  That and they had a pretty good group of pilots and mechanics on board the technical review team as well as RSR is type rated in the quad.

Yes, I'm well aware of the technical expertise on the team... quite some time ago, I used to be one of the "experts" on that team However, this and other 744 sims have been developed over the years (even decades) and there has always been something new to discover (and refine). Sometimes a newbie (or not so newbie) can ask a relatively innocuous question that takes you down a figurative rabbit warren, where you discover whole new worlds (and reveal just how oblivious we "experts" are to the finer technical details).

By the way, I consider myself to be more than an "end user". I have accessed and used (in the field) Boeing engineering manuals of varying accuracy/reliability from various airlines as part of my (former) employment in aircraft maintenance engineering over 3 or 4 decades (The 744 was my speciality). Also, having dealt with Boeing before, I know that it's not always possible to get timely responses to requests for additional data (unless you have a real aircraft in real trouble). In some (simulator) cases the solution has to be of the "Band Aid" type until further information comes to hand.

Meanwhile, the FUEL/TANK ENG message has some set and reset logic which I'm still trying to wrap my head around....

 

 

[downscc 1,327]

11 hours ago, Qavion2 said:

By the way, I consider myself to be more than an "end user". I have accessed and used (in the field) Boeing engineering manuals of varying accuracy/reliability from various airlines as part of my (former) employment in aircraft maintenance engineering over 3 or 4 decades (The 744 was my speciality). Also, having dealt with Boeing before, I know that it's not always possible to get timely responses to requests for additional data (unless you have a real aircraft in real trouble). In some (simulator) cases the solution has to be of the "Band Aid" type until further information comes to hand.

I certainly agree, and I have learned much from you.  I feel a professional kinship because I consider Avionics something I would have spent my career with had I the opportunity but the AF chose ground communications-electronics for me, which I enjoyed immensely.

[berts 97]

18 hours ago, Qavion2 said:

Now things are really getting complicated. PWS is a seemingly independent weather radar-related system. I don't know if your manual reflects a general EICAS software change implemented on your fleet which happened to coincide with a new radar system fitted (which had PWS) or if there was a necessity to modify TCAS logic as a result of PWS being fitted.  What happens if the weather is perfectly fine and TCAS detects an impending collision?

Having said that, your TCAS aural inhibit heights seem relatively normal, irrespective of whether PWS is fitted or not.

*Unfortunately, I don't know what the service bulletin relates to (other than it's relation to Navigation). The date of the manual (2004) seems pretty ancient. I can't recall when PWS was introduced to the 744.

Now things are really getting complicated.  I said as much!  I believe PWS (which is independent of TCAS) was introduced in the late 1990's around the same time or shortly after the introduction of EGPWS.  TCAS logic was described in greater technical detail when PWS was introduced, presumably to explain the differences between the two systems with respect to their altitude warning criteria.

What happens if the weather is perfectly fine and TCAS detects an impending collision?  You will get an RA provided you are operating in RA/TA mode and both aircraft are providing altitude data.  However, assuming your own aircraft is below the altitudes mentioned earlier, you will not get the INCREASE DESCENT or DESCEND RA's etc. Vertical guidance is always co-ordinated between the two conflicting aircraft, even in this particular example, because the advisories each TCAS generates are based on the three dimensional airspace around the aircraft where a high likelihood of traffic collision exists.  The dimesions of this airspace are also contingent upon the closure rate of the conflicting traffic.

18 hours ago, Qavion2 said:

A pilot just commented on the PPRuNe forum that it's normal for the inboards to be slightly less than the outboards by 1~200kg about the time that TANK/ENG message appears. Can you say that this has also been your experience?

Yes, but it is not unusual or anything to get excited about.  Aftyer all, when you are burning around 12,000ks/hour in the cruise what's 1~200Kgs between friends (oops, I mean tanks)?!  The difference can be due to normal system tolerances or simply because the pilots didn't spot the >FUEL TANK/ENG message as soon as it first appears.

18 hours ago, Qavion2 said:

*On the ground after refueling, after initial electrical power established, or after CMC ground test; main tank 2 quantity less than or equal to main tank 1 quantity plus 500 kgs and main tank 3 quantity less than or equal to main tank 4 quantity plus 500 kgs

I'm not sure what this is trying to tell us. Is it saying that, even with relatively low fuel loads (say, 10 tonnes in each tank) and the inboards are (less than) 500kgs above the outboards, that you will still get a FUEL/TANK ENG message?

According to Boeing, YES.  The >FUEL TANK/ENG message can display on the ground with a 500Kgs difference (increase) between an inboard main and its adjacent outboard main tank. I believe this is because of the considerable dihedral which causes a static head of pressure from the outboard tanks and differences between individual pump output pressures. For example, two pumps of the same type (main or overide) do not always supply fuel against one pump of a similar type in another tank.

18 hours ago, Qavion2 said:

Is it possible to top up the tanks on the ground (prior to takeoff) with these values in QOTS II? M1=10.0, M2=10.4, M3=10.4, M4=10.0. In this configuration, does the FUEL TANK/ENG message appear?

I don't think so to both of your questions, but I haven't tried this in the QOTS II yet.  The >FUEL TANK/ENG message will definitely not appear if the tank to engine criteria has been met and, because the fuel imbalance between the two inboard and outboard tanks is less than 450Kgs you won't get a >FUEL IMBAL message either.

Bertie 

Edited April 22, 2018 by berts
correction

[Qavion2 39]

10 hours ago, berts said:

The >FUEL TANK/ENG message will definitely not appear if the tank to engine criteria has been met

I'm having trouble understanding that statement. If the tank to engine criteria, in all its complexities, has been met, the message should appear at the required time.

I stumbled upon some more information regarding this in the Fault Isolation Manual, Some, if not all aircraft, now incorporate a modification made to the Fuel Quantity Processing Unit (FQPU) which matches the description in the QRH (My wiring schematic logic is seriously out of date (despite the modern date printed on the bottom):

"A. Fault Isolation Procedure (for >FUEL TANK ENG)
(1) This EICAS message alerts the flight crew to configure the fuel system to establish a tank-to-engine
fuel-feed configuration.
During flight, when the fuel quantity for the inboard main tanks becomes equal to the outboard
main tanks, the EICAS advisory message FUEL TANK/ENG will show (M1 = M2 or M3 = M4).
The flight crew action is to manually close crossfeed valves 1 and 4 and put the M2 and M3
override/jettison pumps to the off position. This will initiate a tank-to-engine fuel-feed
configuration until the end of the flight.

Airline X ALL; AIRPLANES WITH FQPU BLOCK B UPGRADE (SB 28-2182)
(2) The >FUEL TANK/ENG message contains logic to prevent fuel-feed configuration messages
from showing on short flights during takeoff and initial climb. The logic allows the airplane to be
established in an early tank-to-engine configuration when the inboard main tanks are within
1000 lbs (455 kgs) of the outboard main tanks.
Additional logic will maintain the fuel-feed configuration established on the ground for 8 minutes
after the airplane transitions from ground to air. Specifically, for 8 minutes after the transition
from ground to air, the status of the tank-to-engine alert bit shall remain the same as its status
prior to the ground-to-air transition. This will prevent the >FUEL TANK/ENG and >X-FEED
CONFIG messages from showing during takeoff and initial climb.
Airline X ALL
(3) The EICAS message >FUEL TANK/ENG (ADVISORY) shows when all of these conditions are
true:
   (a) The No. 1 or 4 crossfeed valve(s) are not closed.
   (b) All main tanks contain more than 2000 lbs (910 kgs) of fuel [This is the low fuel trigger]
   (c) Jettison mode is not active.
   (d) The TANK TO ENGINE ALERT discrete is set (2-minute time delay).
(4) The TANK TO ENGINE ALERT discrete is set when these conditions are true:
  (a) The airplane is not in refuel mode (the refuel control panel door is closed and/or the
airplane is in air mode).
  (b) The M2 fuel quantity is less than 32,000 lbs (14,500 kgs) or the M3 fuel quantity is less than
32,000 lbs (14,500 kgs).
NOTE: M2 fuel qty is less than M1 VTO+2000 lbs (910 kgs) or M3 fuel qty is less than M4
VTO+2000 lbs (910 kgs).
  (c) One of these conditions is true:
  1) The M2 fuel quantity is equal to or less than M1 or the M3 fuel quantity is equal to or
less than M4.
Airline X ALL; AIRPLANES WITH FQPU BLOCK B UPGRADE (SB 28-2182)
  2) The M2 fuel quantity is not more than 1000 lbs (455 kgs) greater than the M1 fuel
quantity and the M3 fuel quantity is not more than 1000 lbs (455 kgs) greater than the M4
fuel quantity and one of these events occur:
   a) The fuel quantity processor unit is powered up
   b) The CMC ground test >FUEL QUANTITY IND is performed
   c) The refuel panel door is cycled from open to closed and in ground mode."

All this is well above my current paygrade.... I'll let the sim programmers decipher this. Maybe we can work through some examples.

The above logic refers to an RR-powered aircraft (fuel quantities may vary on GE and PW).

11 hours ago, berts said:

Yes, but it is not unusual or anything to get excited about.  Aftyer all, when you are burning around 12,000ks/hour in the cruise what's 1~200Kgs between friends (oops, I mean tanks)?! 

Yes, that thought also crossed my mind, but I see the 120 second (2 minute) logic is also mention in the Fault Isolation Manual. At least one inboard tank must surely be lower than its respective (same wing) outboard tank at the time the message appears.
 

11 hours ago, berts said:

What happens if the weather is perfectly fine and TCAS detects an impending collision?  You will get an RA provided you are operating in RA/TA mode and both aircraft are providing altitude data. 

Now clear. I thought you were saying that you wouldn't get the warnings irrespective of active PWS warnings.

 

10 hours ago, berts said:

TCAS logic was described in greater technical detail when PWS was introduced, presumably to explain the differences between the two systems with respect to their altitude warning criteria.

Ah... OK... I was wondering what the tie in was. So, despite the two systems not being directly related, the inhibits had to be modified to avoid conflict.

Thanks!

Cheers.

JHW

[berts 97]

11 hours ago, Qavion2 said:

I'm having trouble understanding that statement. If the tank to engine criteria, in all its complexities, has been met, the message should appear at the required time.

There are other Fuel System EICAs messages which are relevant to proper fuel management on the B744 and some of the fuel figures you mention appear to be inter-related.  Another relevant set of messages are the >FUEL IMBALANCE messages and because I didn't mention them earlier that is why I loosely referred to the complexities of the fuel system. 

Take the >FUEL IMBALANCE Advisory message as an example: This message will appear when there is a fuel difference of 2,720Kgs between inboard mains 2 & 3 and/or outboard mains 1 & 4 after the FUEL TANK/ENG condition is met.  At other times the fuel difference between tanks 2 & 3 is still quoted as 2,720Kgs, but between 1 & 4 It is only 1,360Kgs.  These fuel imbalance messages will not disappear until the fuel difference in all three cases is less than 450Kgs. 

Unlike ground or flight engineers, pilots converting onto the B744 are not expected to have the sort of in-depth technical knowledge you obviously have and have already described in this post.  The mind boggles if pilots are expected to remember everything in detail about FQPU BLOCK B UPGRADE (SB 28-2182)!  However, what they are expected to know is how to operate the fuel system correctly and, more importantly, how to manage the operation when something goes wrong. Provided pilots keep any fuel imbalance between the relevant main tanks below 1,000KGs then they should normally never see a fuel imbalance message. This practical advice doesn't mean that a pilot should accept a 1,000Kgs fuel imbalance and most try to keep it to an absolute minimum (professional pride and all that... etc. etc.)!  But this one example goes to show what a well-designed and forgiving aircraft the B744 actually is.

Bertie         

[Qavion2 39]

7 hours ago, berts said:

This practical advice doesn't mean that a pilot should accept a 1,000Kgs fuel imbalance and most try to keep it to an absolute minimum (professional pride and all that... etc. etc.)!

Most definitely. We once had a 744 arrive at the gate with around 4.6 tonnes (total). With a 1000kg imbalance, it might have been a little more serious than tea and biscuits with the Chief Pilot.

Anyway, time for a break. The conversations on the >FUEL TANK/ENG message on this forum and the other 744 sim forums are making my head hurt   (On one forum, we're contemplating what would happen to the logic if the wing refuelling control panel door were left fully open)