Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
747-400 Flight Deck Question  
User currently offlineGkyip From United Kingdom, joined Apr 2006, 163 posts, RR: 0
Posted (7 years 7 months 1 week 2 days 8 hours ago) and read 5980 times:
Support Airliners.net - become a First Class Member!

Another baffler for you regarding another 747-400 flight deck photo!  boggled 

This time, where are the stab fuel pump switches?


View Large View Medium
Click here for bigger photo!

Photo © Serge Bailleul - AirTeamImages




The strength of the turbulence is directly proportional to the temperature of your coffee
15 replies: All unread, jump to last
 
User currently offlineThrottleHold From South Africa, joined Jul 2006, 655 posts, RR: 1
Reply 1, posted (7 years 7 months 1 week 2 days 8 hours ago) and read 5977 times:

They're the switches for the fuel tanks in the horizontal stabiliser.

User currently offlineGkyip From United Kingdom, joined Apr 2006, 163 posts, RR: 0
Reply 2, posted (7 years 7 months 1 week 2 days 8 hours ago) and read 5973 times:
Support Airliners.net - become a First Class Member!

apologies, let me clarify...  duck 

If you look at the fuel control panel on the OH, the switches for the stab tank are missing. They should be below the center tank pump switches? Is it controlled automatically on KLM 744s or has this A/C not got a stab tank?

[Compare with these photos]


View Large View Medium
Click here for bigger photo!

Photo © Max Hergemoeller
View Large View Medium
Click here for bigger photo!

Photo © Gabriel Savit - AirTeamImages



Many Thanks



The strength of the turbulence is directly proportional to the temperature of your coffee
User currently offlineProk From Netherlands, joined May 2005, 36 posts, RR: 0
Reply 3, posted (7 years 7 months 1 week 2 days 7 hours ago) and read 5959 times:

KLM doesn't have a stabiliser tank on the 747-400 full pax and the freighter, only the combi has one.

User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 4, posted (7 years 7 months 1 week 2 days ago) and read 5883 times:

Quoting Gkyip (Thread starter):
This time, where are the stab fuel pump switches?

Wow, you must have eagle eyes to see the presence or absence of switches on the overhead panel from the angle in that photo  Wow!!

Quoting Prok (Reply 3):
KLM doesn't have a stabiliser tank on the 747-400 full pax and the freighter, only the combi has one.

Yep, I remember servicing a KLM 744 many years ago, and being mildly shocked that there was no stab tank. I thought that it was fitted as standard to all 744's.

All this leads me to an interesting question, would the stab trim charts for a 744 without a stab tank be completely different to a 744 with a stab tank? IIRC, the stab tank can hold about 12,000 L of Jet A-1, which is about 9,600kg of weight in the tailplane. Surely this amount of weight at the extremity of the aircraft will have an effect on the C of G and hence stabiliser trim. Does anyone know?

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineGkyip From United Kingdom, joined Apr 2006, 163 posts, RR: 0
Reply 5, posted (7 years 7 months 1 week 1 day 22 hours ago) and read 5847 times:
Support Airliners.net - become a First Class Member!

Quoting JetMech (Reply 4):
I thought that it was fitted as standard to all 744's

yes i thought that as well! Think it's a bit odd how they don't have it. What is the reasoning behind this? anyone know?

Quoting Prok (Reply 3):
KLM doesn't have a stabiliser tank on the 747-400 full pax and the freighter, only the combi has one.

Surely the 744ERF has one? Otherwise it wouldn't be very ER!  Silly

Gary



The strength of the turbulence is directly proportional to the temperature of your coffee
User currently offlineTristarSteve From Sweden, joined Nov 2005, 3983 posts, RR: 34
Reply 6, posted (7 years 7 months 1 week 1 day 13 hours ago) and read 5804 times:

BA also has four B744 which have no stab tank. They are called B744 Lite.
A B744 does not need a stab tank until about 12hours sector.


User currently offlineGkyip From United Kingdom, joined Apr 2006, 163 posts, RR: 0
Reply 7, posted (7 years 7 months 1 week 3 hours ago) and read 5636 times:
Support Airliners.net - become a First Class Member!

Quoting TristarSteve (Reply 6):
BA also has four B744 which have no stab tank. They are called B744 Lite.

Does anyone know the reg of these aircraft?

I suppose the benefit of having no stab tank is saving weight? If you don't need it until about 12 hours into the flight then the weight saved by removing these setups will benefit on flghts to say North America etc.

Gary



The strength of the turbulence is directly proportional to the temperature of your coffee
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17003 posts, RR: 67
Reply 8, posted (7 years 7 months 1 week 3 hours ago) and read 5635 times:

Quoting Gkyip (Reply 7):

I suppose the benefit of having no stab tank is saving weight? If you don't need it until about 12 hours into the flight then the weight saved by removing these setups will benefit on flghts to say North America etc.

Correct. Same reason the GE-90 is not always the best powerplant for the 777. The RR engines confer advantages over shorter sectors given they weigh quite a bit less.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineAmerican 767 From United States of America, joined May 1999, 3742 posts, RR: 12
Reply 9, posted (7 years 7 months 10 hours ago) and read 5354 times:
AIRLINERS.NET CREW
FORUM MODERATOR

Quoting JetMech (Reply 4):
Surely this amount of weight at the extremity of the aircraft will have an effect on the C of G and hence stabiliser trim. Does anyone know?

Yes, this amount of weight sure has an effect on the CG. It makes the CG moves closer to the tail. The CG moves along the center line of the fuselage while in cruise, the more the CG is on the front the more stable the aircraft is, but: the more the CG is closer to the tail the more fuel efficient the aircraft is. I think that's why the fuel contained in the stab tank is burned later than the fuel in the center and wing tanks.

Ben Soriano
Brussels Belgium



Ben Soriano
User currently offlineBellerophon From United Kingdom, joined May 2002, 583 posts, RR: 59
Reply 10, posted (7 years 7 months 8 hours ago) and read 5330 times:

American 767

...I think that's why the fuel contained in the stab tank is burned later than the fuel in the center and wing tanks. ...

Actually it isn't.

It is burned very early in a long range flight, before most of the centre wing tank fuel or virtually any of the wing tanks fuel.

A full CWT is 52,167 kg, and a full stabilizer tank is 10,030 kg. Somewhere around 90 minutes after take-off, when the CWT fuel has decreased to 36,470 kg, the Fuel Management System Cards will automatically open the appropriate valves and activate the transfer/jettison pumps and transfer all the stabilizer fuel from the stabilizer tank into the CWT.

All the stabilizer tank fuel should be gone around two and a half to three hours into a 12+ hour flight.

Your reasoning, regarding the aerodynamics of the situation, was broadly correct, but the above procedure is designed to avoid a rather nasty potential problem.

If we left the stabilizer tank fuel to the end of our long flight, when we have no fuel in the centre tank and little fuel in the wing tanks, and at that point we discovered that both the transfer/jettison pumps had failed leaving fuel trapped in the stabilizer tank, then, with little or no fuel in the centre or wing tanks, the CG would be far too far aft for the aircraft to land safely, and there would be very little we could do about it.

So, to guard against this problem, if there is to be a failure of both transfer/jettison pumps, we need to know about it early in the flight, so that we can land whilst we still have sufficient fuel in the centre and wing tanks to keep the CG forward of the aft limit.

This scenario is generally covered on conversion courses, and new B744 pilots are often surprised at how awkward a problem this can is. Very broadly, you will have to land within 6-7 hours, not the 12 -15 hours you'd planned!



Gkyip

...Does anyone know the reg of these aircraft? ...

G-CIVF / G / H / I


Best regards

Bellerophon


User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 11, posted (7 years 7 months 8 hours ago) and read 5316 times:

Quoting Bellerophon (Reply 10):

Is this system similar to that of the Concorde? I recall reading that Concorde had a series of tanks and pumps that moved the fuel accordingly in order to change the CG of the aircraft, which had something to do with transitioning between supersonic and subsonic flight (the CG shifts...if I am correct).


User currently offlineKaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 26
Reply 12, posted (7 years 7 months 7 hours ago) and read 5285 times:

The A340 uses the Stab tank to trim, the B744 uses it as a place to store fuel...


Whoever said "laughter is the best medicine" never had Gonorrhea
User currently offlineDavid L From United Kingdom, joined May 1999, 9524 posts, RR: 42
Reply 13, posted (7 years 7 months 5 hours ago) and read 5240 times:

Quoting N231YE (Reply 11):
Is this system similar to that of the Concorde?

Since Bellerophon appears to be unable to come to the phone right now, I'll stick my nose in.

Quoting Kaddyuk (Reply 12):
The A340 uses the Stab tank to trim, the B744 uses it as a place to store fuel...

As I understand it, in order to be "similar to that of the Concorde", you'd need to be able to pump fuel to and fro on demand - can that be done on the A340 or is it entirely automatic? On Concorde, it wasn't only used for low-drag trim. For example, for approach and landing, fuel was pumped rearwards, causing a tail-heavy situation. This was counteracted by nose-down elevon, resulting in a "flap" effect. Given that the 747 and 340 have separate flaps and elevators, perhaps this feature just wouldn't be of any use.

 duck  I'll now sit low while we wait for the real answer from the expert.  Smile


User currently offlineGkyip From United Kingdom, joined Apr 2006, 163 posts, RR: 0
Reply 14, posted (7 years 6 months 4 weeks 1 day 20 hours ago) and read 5117 times:
Support Airliners.net - become a First Class Member!

Quoting N231YE (Reply 11):
Is this system similar to that of the Concorde?

Concorde had a tremendously complex fuel system, one that was used, not only as a power source for the engines, but also as a trim device for the whole aircraft. As Concorde did not have a horizontal stabiliser, it did not have elevator trim and therefore to balance the aircraft in flight, it moved fuel around the aircraft (more so in the fwd to aft sense due to the moments involved). As I understand it, Concorde would move fuel aft for supersonic flight and bring it forward for normal flight, but (like David L) I think i'll leave it to the real experts on this well educated forum!

Gary



The strength of the turbulence is directly proportional to the temperature of your coffee
User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 15, posted (7 years 6 months 4 weeks 1 day 14 hours ago) and read 5054 times:

Quoting American 767 (Reply 9):
Yes, this amount of weight sure has an effect on the CG.



Quoting Bellerophon (Reply 10):
It is burned very early in a long range flight, before most of the centre wing tank fuel or virtually any of the wing tanks fuel.



Quoting Kaddyuk (Reply 12):
The A340 uses the Stab tank to trim, the B744 uses it as a place to store fuel...

Thanks for the information fellow Techies  bigthumbsup ! I actually started a thread in Tech/Ops a while back discussing the differences in the A340/A330 and B744 trim systems. Any of you care to have a crack at answering my question?

Airbus And Boeing Trim System Differences. (by JetMech Sep 29 2006 in Tech Ops)

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
Top Of Page
Forum Index

Reply To This Topic 747-400 Flight Deck Question
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
747-400 Fuel Capacity Question posted Sun Feb 12 2006 20:24:19 by TropicBird
767 200 Into A 400 Flight Deck? posted Tue Jan 31 2006 09:42:43 by JumboJim747
747-400 Flight Profile posted Sat Jul 5 2003 16:26:35 by Indianguy
Question On 747-400 Slat Retraction posted Wed Jun 28 2006 19:53:37 by UPSMD11
747-400 LAX-LHR 3 Engine Flight Report Now Out. posted Thu Jun 8 2006 20:30:37 by JulianUK
Oxygen Masks In 747 Flight Deck posted Tue Sep 13 2005 07:30:21 by TG992
VC-25A Flight Deck Photo posted Wed Nov 29 2006 23:14:09 by 2H4
Slat Retraction During Reverse Thrust? 747-400 posted Sun Nov 5 2006 00:29:24 by Ajaaron
Is Re-engining A 747-400 With Trent 500s Possible? posted Sat Nov 4 2006 22:59:28 by LTU932
What Naca Airfoil Type Does The 747-400 Use? posted Thu Oct 12 2006 15:06:04 by Flybyguy

Sponsor Message:
Printer friendly format