KrisYYZ From Canada, joined Nov 2004, 1575 posts, RR: 0 Posted (7 years 3 weeks 9 hours ago) and read 4015 times:
I’m sorry if this has been discussed before. I have a two part question regarding the A340/A330.
I realize that the A340 was made for long-haul ops before big engines like the GE90s where developed. That is why the A340 has the 4 CFM engines at 30K thrust instead of 2 engines at 80K or so. I’m still not clear as to how 4 engines at 30-35K thrust is still enough to take the A340 into the air, when the A330 has 2 x 72K thrust and is a significantly lighter plane. Do the less powerful CFM’s create the range for the A340? Do 4 weaker engines burn less than 2 70-80K engines?
In theory, if one was to remove the engines, some fuel tanks and modified the flight deck, could a A340 frame be turned into an A330?
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 1, posted (7 years 3 weeks 9 hours ago) and read 4003 times:
Quoting KrisYYZ (Thread starter): In theory, if one was to remove the engines, some fuel tanks and modified the flight deck, could a A340 frame be turned into an A330?
I would assume that the wing would have to be modified more than the 'frame' as the 330 wing has only two pylons and the 340 has four. These pylons are not just an external feature but must be carried and braced within the wing structure. Likewise, wiring and plumbing must match.
My guess would be a resounding 'maybe' but it would be cheaper to scratch-build one.
Flight deck mods should be rather easy: Unscrew and disconnect throttle quadrant, drop in new one. Same with the fuel levers just below it. Most of the rest of it should be software changes. A CRT or LCD display doesn't care if it is showing 2-engine, 4-engine or reruns of Gilligan's Island.
Happiness is not seeing another trite Ste. Maarten photo all week long.
RichardPrice From , joined Dec 1969, posts, RR: Reply 2, posted (7 years 3 weeks 9 hours ago) and read 3986 times:
Quoting SlamClick (Reply 1):
I would assume that the wing would have to be modified more than the 'frame' as the 330 wing has only two pylons and the 340 has four. These pylons are not just an external feature but must be carried and braced within the wing structure. Likewise, wiring and plumbing must match.
Actually the A330 wings are almost identical to the A340-300 wings, and its one of the features lauded in the tanker bid - it makes additional wing mounted refueling pods very easy as no structural modifications have to be made to the wing due to the outer engine mountpoints.
The A330 also retains the central main gear bay.
I doubt it would be financially viable, but I see no reason why it couldnt be done.
Mir From United States of America, joined Jan 2004, 19717 posts, RR: 56 Reply 3, posted (7 years 3 weeks 9 hours ago) and read 3984 times:
Quoting KrisYYZ (Thread starter): I’m still not clear as to how 4 engines at 30-35K thrust is still enough to take the A340 into the air, when the A330 has 2 x 72K thrust and is a significantly lighter plane.
Remember that twins are always going to be overpowered compared to quads, since one engine has to be powerful enough to take the plane off the ground at MTOW at a certain rate of climb all by itself. Not the case on a quad.
Quoting SlamClick (Reply 1): A CRT or LCD display doesn't care if it is showing 2-engine, 4-engine or reruns of Gilligan's Island.
So that's what they do in cruise!
-Mir
7 billion, one nation, imagination...it's a beautiful day
A319XFW From , joined Dec 1969, posts, RR: Reply 4, posted (7 years 3 weeks 8 hours ago) and read 3957 times:
Quoting KrisYYZ (Thread starter): In theory, if one was to remove the engines, some fuel tanks and modified the flight deck, could a A340 frame be turned into an A330?
From a systems point of view:
The fuel tanks would have to be changed, as the A340 is designed for 4 engines, so has got 4 feed tanks etc, so you'd have to move tank boundaries around, change pumps, pipes, valves etc (as different rotor-burst zones) .
You'd also have to change all the wiring and hydraulics coming off the outboard engines and have it all going into the inboard one (don't exactly know the set-up of EDP's and generators on A330/A340).
For the landing gear, you'd have to remove the CLG and possibly change the pintle pins etc on the attach points (for example, the A321 LG is not interchangable with the A320 LG as the attach points are beefed up)
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 5, posted (7 years 3 weeks 7 hours ago) and read 3922 times:
Quoting SlamClick (Reply 1): The A330 also retains the central main gear bay.
It has the bay, but IIRC there's a small fuel tank there on the 330.
Quoting Mir (Reply 3): Quoting SlamClick (Reply 1):
A CRT or LCD display doesn't care if it is showing 2-engine, 4-engine or reruns of Gilligan's Island.
So that's what they do in cruise!
Beat me to it.
As A319XFW says, very interesting question. The aircraft can be thought of as 1.5 type in many ways since they are so very alike.
My wild guess is that it would be about as easy to go either way.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
A342 From Germany, joined Jul 2005, 4655 posts, RR: 4 Reply 6, posted (7 years 3 weeks 6 hours ago) and read 3892 times:
Quoting KrisYYZ (Thread starter): I’m still not clear as to how 4 engines at 30-35K thrust is still enough to take the A340 into the air, when the A330 has 2 x 72K thrust and is a significantly lighter plane. Do the less powerful CFM’s create the range for the A340? Do 4 weaker engines burn less than 2 70-80K engines?
No, more fuel with a higher MTOW. On shorter flights the A333 burns less.
But if you were going to convert an A343 into an A333, you'd have to lower the MTOW because of the reason stated in reply 3. And there goes your range advantage.
As it has already been stated, maybe you could do it, but it makes no sense.
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 7, posted (7 years 3 weeks 6 hours ago) and read 3882 times:
Quoting KrisYYZ (Thread starter): I realize that the A340 was made for long-haul ops before big engines like the GE90s where developed. That is why the A340 has the 4 CFM engines at 30K thrust instead of 2 engines at 80K or so. I�m still not clear as to how 4 engines at 30-35K thrust is still enough to take the A340 into the air, when the A330 has 2 x 72K thrust and is a significantly lighter plane. Do the less powerful CFM�s create the range for the A340? Do 4 weaker engines burn less than 2 70-80K engines?
As Mir was explaining, a twin needs more power because worst case engine out scenarios (on take-off) are based on one engine failing. If one engine fails on a quad, you have three left. If one fails on a twin, you have one left. So that one has to be as powerful as the three on the quad, all other things being equal (which they aren't, but anyway).
If you do the math, you will find that a twin needs 50% more total power than an "identical" quad. Consequently, each engine on a twin needs to be twice as powerful as on the "identical" quad.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
Texfly101 From United States of America, joined Jan 2006, 351 posts, RR: 0 Reply 10, posted (7 years 3 weeks 3 hours ago) and read 3818 times:
They do have a commonality that could enable the switch to a twin. The proposed KC-30 tanker is an A330 fuselage mated to an A340 wing. The outer two pylon points are being used as hose and drogue refueling points in addition to the flying boom on the rear of the fuselage. The other switch, i.e. going from 4 to 2 engines is possible and has been proposed in a lot of different aircraft like the 707, DC8 etc. The GE90 was originally tested on a 747 and if memory serves me, there were proposals for twin engine 747 and tri engine 747 when the twin aisles big bodies were originally being designed. But usually the economics aren't there. An older fuselage design accompanied by a new wing is rarely viewed with enthusiasm. But thats just my view.
ReidYYZ From Kyrgyzstan, joined Sep 2005, 536 posts, RR: 1 Reply 12, posted (7 years 3 weeks 2 hours ago) and read 3787 times:
Quoting A319XFW (Reply 9): Quoting Starlionblue (Reply 5):
It has the bay, but IIRC there's a small fuel tank there on the 330.
I don't think that's the case - it's got a 'basic' centre wing tank.
Correct, where the ctr gear would sit is a vast void. Blanking plates cover were the ctr gear doors fit, and above these covers is an empty space. The actual center tank is the center wing section that the wheel wells sit under.
Quoting SlamClick (Reply 1): Unscrew and disconnect throttle quadrant, drop in new one. Same with the fuel levers just below it. Most of the rest of it should be software changes.
This is how it is actually done on simulators. I had engine run sim training for A330 a few years ago, and there was a 4 engine throttle quadrant sitting in the stowage closet at the back of the sim.
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 13, posted (7 years 3 weeks 1 hour ago) and read 3774 times:
Quoting ReidYYZ (Reply 12): Quoting A319XFW (Reply 9):
Quoting Starlionblue (Reply 5):
It has the bay, but IIRC there's a small fuel tank there on the 330.
I don't think that's the case - it's got a 'basic' centre wing tank.
Correct, where the ctr gear would sit is a vast void. Blanking plates cover were the ctr gear doors fit, and above these covers is an empty space. The actual center tank is the center wing section that the wheel wells sit under.
I stand gladly corrected.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
LongHauler From Canada, joined Mar 2004, 4281 posts, RR: 36 Reply 14, posted (7 years 2 weeks 6 days 22 hours ago) and read 3723 times:
Quoting ReidYYZ (Reply 12): This is how it is actually done on simulators. I had engine run sim training for A330 a few years ago, and there was a 4 engine throttle quadrant sitting in the stowage closet at the back of the sim.
One hour is scheduled to change one of our A340 sims to an A330, and vv. The thrust lever quadrant, and the overhead panel is changed. The rest is software.
Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
PurdueAv2003 From United States of America, joined Dec 2005, 246 posts, RR: 1 Reply 15, posted (7 years 2 weeks 6 days 17 hours ago) and read 3657 times:
No one has mentioned one major structural difference: the pylon and wing structure. The 340 has four small pylons for the CFM engines. The 330 requires a much heavier pylon for the larger engines and only requires two. If someone were to actually try to covert a 340 to a 330, they would be better off replacing the entire wing structure than to try to remove two pylons and beef up the other two. On top of that, all of the bleed systems, controls, leading edge devices, etc, would all need to be changed. Then again, the whole idea of converting a 340 to a 330 is ridiculous, anyway.
A342 From Germany, joined Jul 2005, 4655 posts, RR: 4 Reply 16, posted (7 years 2 weeks 6 days 6 hours ago) and read 3568 times:
Quoting PurdueAv2003 (Reply 15): No one has mentioned one major structural difference: the pylon and wing structure. The 340 has four small pylons for the CFM engines. The 330 requires a much heavier pylon for the larger engines and only requires two. If someone were to actually try to covert a 340 to a 330, they would be better off replacing the entire wing structure than to try to remove two pylons and beef up the other two.
Only the inner pylon needs to be beefed up I think. The reason is that the A330 outer wing has to endure higher stresses from turbulence than the A340 wing because the A340's outboard engines weight soften these stresses. In turn, there are no special structural differences other than pylon attachments.
I'm no expert on this, please feel free to correct me if I'm wrong.
ReidYYZ From Kyrgyzstan, joined Sep 2005, 536 posts, RR: 1 Reply 17, posted (7 years 2 weeks 6 days 3 hours ago) and read 3529 times:
Quoting ReidYYZ (Reply 12): The actual center tank is the center wing section that the wheel wells sit under.
Brain fart alert: the wheel wells actually sit under cabin floor BEHIND center wing box. The forward wall of the w/w bay is actually the aft bulkhead of the center wing box, used as a ctr tank or not.
Quoting PurdueAv2003 (Reply 15): No one has mentioned one major structural difference: the pylon and wing structure.
I though of this well after the fact. The pylons installed are engine specific. RR pylons are therefore entirely different in design and manufacture from the P&W and GE ones. The support points at the underside of the wing would be identical, most likely for ease of manufacture. Therefore based on this theory, the attach points would also be identical for the smaller CFM pylon attach points. (Elsewhere there is the thread about re-engining older aircraft: DC-8-70 is an example mentioned. With the new CFM engines, they are strapped to new pylons, not the JT3D pylon with mods done to it.) For the outboard pylon attach points there must be provision for the similar attach point interface on the underside of the wing. One big difference would be the L/E slats. As the O/B pylon sits between two L/E slat surfaces, the slats, at least one maybe both would be different to accommodate the cutout for the pylon upper surface as seen:
The wing structure are identical in size shape etc.... between the A332/3 and A342/3 and up to a certain point, move along the same assembly line where one becomes A34x and the other becomes A33x. That is where the internals differ. To peer inside the L/E of an A33x wing one would find brackets installed that hold nothing, but it would have been a support point for, say, pneumatic ducting for the phantom #1 or #4 engine on a A34x. I have been told in the past that the difference between to two wings, it is a two week time frame from built up to a common point to where they would each be a different wing for the type end products.
Now having said that, I would question:
Quoting Texfly101 (Reply 10): The proposed KC-30 tanker is an A330 fuselage mated to an A340 wing.
I could be wrong in some form or another because the fuselage structure is identical. It is the internal 'guts' that differ.
Quoting PurdueAv2003 (Reply 15): Then again, the whole idea of converting a 340 to a 330 is ridiculous, anyway.
Not neccessarily, due to aircraft manufacturing (A in this case) ideology, it is entirely possible. Financially viable, maybe not so much.
Saintsman From United Kingdom, joined Mar 2002, 2065 posts, RR: 2 Reply 20, posted (7 years 2 weeks 4 days 18 hours ago) and read 3314 times:
On the RAF FSTA aircraft, the wing is a standard A300-200 wing so I see no reason that the KC-30 wing would be different. Externally the wings are the same but internally there are significant differences. For example, why would you need to have the outer engine strenghtening on an A330? Its additional weight that you don't need to carry.
For the pod and pylon fit, there are significant machined fittings attached to Rib 26 and a large fitting on the front spar. The wing under surface is also re-inforced towards the leading edge. Comparing this to something like the KC-10, there is considerably more strengthening required for the A330 wing.
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 21, posted (7 years 2 weeks 4 days 13 hours ago) and read 3273 times:
Quoting Saintsman (Reply 20): For example, why would you need to have the outer engine strenghtening on an A330? Its additional weight that you don't need to carry.
The outer engines actually relieve bending moment, so in some ways a four holer can have a weaker wing than a two holer.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
Texfly101 From United States of America, joined Jan 2006, 351 posts, RR: 0 Reply 22, posted (7 years 2 weeks 4 days 3 hours ago) and read 3168 times:
Quoting ReidYYZ (Reply 17): I could be wrong in some form or another because the fuselage structure is identical. It is the internal 'guts' that differ.
Nope, its as I said. That's the one of the reasons why the Aussies chose the KC-30 over the 767. They felt that it was less risk for the outer two pylon points of the A340 wing to be hard plumbed for refueling points than for the KC-767 wing to be replumbed for hose and drogue points. They felt since the A340 wing already had plumbing for fuel to the outer two pylons, it would be less risk to develop a boom for the A330 fusleage. Add in the cargo capability and they chose the KC-30.
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