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A B747 Two Holer?

Posted: Wed May 04, 2016 2:39 am
by B737900
The B747 in any variant is such a beautiful and iconic aircraft. It seems to me that it is slowly fading away because of the fact that it has four burners. A question to the engineers: could the B747 fly on two 21st century engines?

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 2:51 am
by jetmatt777
The reason it is largely disappearing is a very costly maintenance requirement that is due in 2018.

Not sure about your exact question but it would require recertification as a new type if it were possible. This would also mean the elimination of the seats forward of the 1A door. I believe current requirements are that there must be emergency exits in front of the forward most occupied passenger seat.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 12:09 pm
by Starlionblue
This question is asked periodically.

Simple answer: Yes you could, but the requisite drastic redesign and subsequent recertification means you're much better off building a new plane. This plane is called 777-9X.

Say you still want to build a two-holer 747, here are just some of the issues you'd have to deal with:
- You must have doors both forward and aft of seats, either install a new set of doors at the front, or eliminate seats. Same for the upper deck I think. (The 747 is grandfathered.)
- Increase length of landing gear in order to handle much larger engines.
- Redesign the wing spars to handle the entirely different weight distribution on the wing.
- Redesign the wing profile to handle two larger engines instead of four smaller ones.
- Redesign the fin and rudder. They would need to be larger to handle the increased engine out moment.
- Redesign the entire hydraulic system.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 1:11 pm
by redzeppelin
Quoting Starlionblue (Reply 2):

This question is asked periodically

Here is a random sampling:

The 747 Twin - Drop Two Holes? (by nema Oct 13 2015 in Civil Aviation)

Twin Engined 747...is It Possible? (by Jcchristie Aug 3 2008 in Tech Ops)

Why No Twin Engine 747? (by Boeing nut May 13 2001 in Civil Aviation)

Could There Ever Be A Twin-engined 747? (by DeltaXNA Apr 19 2013 in Tech Ops)

Hey, How about a twin engined 747? (by NYC Int'l Mar 18 1999 in Civil Aviation)

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 1:57 pm
by G-CIVP
Quoting jetmatt777 (Reply 1):
The reason it is largely disappearing is a very costly maintenance requirement that is due in 2018.

Please could you expand.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 2:31 pm
by B737900
Quoting Starlionblue (Reply 2):

Simple answer: Yes you could, but the requisite drastic redesign and subsequent recertification means you're much better off building a new plane. This plane is called 777-9X.

Say you still want to build a two-holer 747, here are just some of the issues you'd have to deal with:
- You must have doors both forward and aft of seats, either install a new set of doors at the front, or eliminate seats. Same for the upper deck I think. (The 747 is grandfathered.)
- Increase length of landing gear in order to handle much larger engines.
- Redesign the wing spars to handle the entirely different weight distribution on the wing.
- Redesign the wing profile to handle two larger engines instead of four smaller ones.
- Redesign the fin and rudder. They would need to be larger to handle the increased engine out moment.
- Redesign the entire hydraulic system.

  

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 5:07 pm
by HOOB747
I'm taking the thread-starters question more literally. I believe he is merely asking if you removed two of the 747s four engines, could the aircraft get off the ground and fly? Or remove all 4 engines and hang two GEnx 2B engines on the 747s wings and roll down the runway. Could the plane fly from Los Angeles to San Diego with passengers and cargo? Or with no passengers and no cargo? Not considering efficiencies or certifications or redesigns.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 5:19 pm
by HOOB747
Quoting G-CIVP (Reply 4):
Quoting jetmatt777 (Reply 1):
The reason it is largely disappearing is a very costly maintenance requirement that is due in 2018.

Please could you expand.

They need to have their fuel tanks retrofitted with an relatively expensive nitrogen inerting system, resulting from concerns about aging fuel tanks (TWA 800). Some operators will retire or unload their 747s instead of performing an un-economical fix.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 6:05 pm
by jetmatt777
Quoting HOOB747 (Reply 6):
'm taking the thread-starters question more literally. I believe he is merely asking if you removed two of the 747s four engines, could the aircraft get off the ground and fly? Or remove all 4 engines and hang two GEnx 2B engines on the 747s wings and roll down the runway. Could the plane fly from Los Angeles to San Diego with passengers and cargo? Or with no passengers and no cargo? Not considering efficiencies or certifications or redesigns.

In the engineering sense anything is possible I guess. But keep in mind, if you throw a rock fast enough it will fly. So these periodic hypotheticals do need to have some basis of reality built into them.

Might as well ask if a double decker CRJ700 would fly. Yes it would. But it would require as much redesign as a two engined 747 -- not even the same aircraft at that point and a pointless hypothetical.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 6:19 pm
by B52overSMF
Quoting G-CIVP (Reply 4):

You can read about it the the associated Advisory Circular here:
'Operator Information for Incorporating Fuel Tank Flammability Reduction Requirements into a Maintenance or Inspection Program'
http://www.faa.gov/documentLibrary/m...Advisory_Circular/AC%20120-98A.pdf

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 6:20 pm
by American 767
The cost of the project would be a lot higher than what it is for developing the 777-8/9X, so Boeing would have to sell a lot of units to the airlines for the project to even reach a break even point.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 8:15 pm
by rbavfan
would love to see the size of the fan for the two 133,000 lb. st. engines to meet the 748's current thrust. Also they would have to add additional thrust for engine out so I'd figure at least min of 155,000 lb. st. Lets se those go throughout testing with current technology.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 8:35 pm
by aw70
Quoting Starlionblue (Reply 2):
Say you still want to build a two-holer 747, here are just some of the issues you'd have to deal with:
- You must have doors both forward and aft of seats, either install a new set of doors at the front, or eliminate seats. Same for the upper deck I think. (The 747 is grandfathered.)
- Increase length of landing gear in order to handle much larger engines.
- Redesign the wing spars to handle the entirely different weight distribution on the wing.
- Redesign the wing profile to handle two larger engines instead of four smaller ones.
- Redesign the fin and rudder. They would need to be larger to handle the increased engine out moment.
- Redesign the entire hydraulic system.


In all fairness, a lot of this (in particular, the new wing) was done for the -8 version of the 747 anyway. With arguably very limited impact in the marketplace. Boeing are certainly not going to invest that much $$$ into the 747 *again*, of course - but if the re-design of the 747 was being done now, the original poster might even have a (weak) point of sorts.

Or not. The 777 is a lovely craft, and it was already designed for two engines from the get-go. No need to bend over backwards to fix the 747, to do something it was never intended to do.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 8:52 pm
by Gasman
The 747 is dead, and has been replaced by a mind-numbingly boring cylindrical sardine can with wings (aka the 773). We need to accept this, grieve and then vote with our wallets by flying the A380 whenever possible.

Quoting rbavfan (Reply 11):
would love to see the size of the fan for the two 133,000 lb. st. engines to meet the 748's current thrust. Also they would have to add additional thrust for engine out so I'd figure at least min of 155,000 lb. st. Lets se those go throughout testing with current technology.

This comment is relevant. The engine technology for a true double-decker VLA twin engine aircraft doesn't practically exist yet.

I can't see anyone designing a VLA trijet. But in 10+ years time, when engine technology has developed to the point where a VLA double decker twinjet is feasible, will Boeing re-enter the market? My guess is yes. Air travel is currently increasing at a stratospheric rate, but airport and ATC space is finite. Eventually, consolidating movements to perhaps slightly less frequent, but much larger aircraft will make more and more sense. I'm expecting Boeing to announce a new VLA sometime between 2020 and 2025.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 8:54 pm
by Skisandy
This thread is just as far fetched and useless as this thread,
which I propose for the first time:

Could a 737 fly from JFK to South Africa? Or at least trans-Atlantic?

That would be a new idea!

Oh, wait - THAT thread has been started many times also already......

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 9:26 pm
by G-CIVP
Quoting HOOB747 (Reply 7):
They need to have their fuel tanks retrofitted with an relatively expensive nitrogen inerting system, resulting from concerns about aging fuel tanks (TWA 800). Some operators will retire or unload their 747s instead of performing an un-economical fix.

I thought that was only specific to older models such as 100's, 200's rather than 400's?

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 9:27 pm
by fanofjets
How about a four-engine Boeing 757?

  

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 9:35 pm
by Gasman
Quoting Skisandy (Reply 14):
This thread is just as far fetched and useless as this thread,
which I propose for the first time:

Could a 737 fly from JFK to South Africa? Or at least trans-Atlantic?

True, but there's no real harm in it - even if it has been asked before. Who amongst us doesn't fantasise/hypothesise about what might or might be possible in the aviation world? Without threads like these (from time to time) airliners.net would be a pretty colourless place.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 9:36 pm
by Gasman
Quoting fanofjets (Reply 16):
How about a four-engine Boeing 757?

You jest, but it leads me to think of the BAE-146. What were they thinking? Really?

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 9:44 pm
by redzeppelin
Quoting fanofjets (Reply 16):
How about a four-engine Boeing 757?

Solves the oft-repeated problem that no engines in the 757's class are currently in production...

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 10:29 pm
by Skisandy
OK, I agree that the 737 JFK-South Africa question is a legitimate one,
then the traveler would have a choice of frequency, rather than the
boring daily wide body.

All that is bearable - just as long as the livery is not Euro- white!

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 10:33 pm
by Viscount724
Quoting Gasman (Reply 17):
True, but there's no real harm in it - even if it has been asked before. Who amongst us doesn't fantasise/hypothesise about what might or might be possible in the aviation world? Without threads like these (from time to time) airliners.net would be a pretty colourless place.

But not when the subject has been addressed at length twice in the past 6 months or so, the last time in this thread in January with 52 replies.
B-747-8i Pax With 2 Engines? (by Delta777Jet Jan 10 2016 in Civil Aviation)

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 10:40 pm
by American 767
Quoting fanofjets (Reply 16):
How about a four-engine Boeing 757?

I would call that the resurrection of the 707.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 10:46 pm
by Wingtips56
Quoting Gasman (Reply 18):
You jest, but it leads me to think of the BAE-146. What were they thinking? Really?

That was to make a quiet airplane that could tippy-toe into noise-restrictive airports. The first aircraft off the line was G-SSSH, to hype the quietness. PSA and AirCal bought them for SNA because of the low noise. (Of course the poor dispatch reliability helped reduce the noise even further.)

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 10:57 pm
by DTWPurserBoy
Quoting fanofjets (Reply 16):
How about a four-engine Boeing 757?
Quoting American 767 (Reply 22):
I would call that the resurrection of the 707.

This one made me laugh. That is exactly what it would be.

Take a look at the A340-200/300 and even 600. Headed for the scrappers or a few VIP operators.

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 11:05 pm
by A330
As far as I know, and I am a Captain on B744, this fuel tank modification requirement is not necessary for non FAA carriers and is also totally unnecessary safety wise. By the way, not only B747 is affected, Also B777, B737 and Airbus A330 and A320 series are involved.
The B744 is a magnificent flying machine, capable to do ANYTHING a B777 or B787 does, but in a more refined way, with more redundancy ( read Safety) and giving a smoother ride to its passengers.
I , and many of my colleagues do not believe the TWA800 story put up by the NTSB.


By the bay, an outer engine failure ( so huge moment) on B744 is far more pronounced than the average twin engine fail...that is one reason why the rudder is so large on B747. ( and A380)

RE: A B747 Two Holer?

Posted: Wed May 04, 2016 11:07 pm
by 77west
Quoting Gasman (Reply 18):
You jest, but it leads me to think of the BAE-146. What were they thinking? Really?

The only plane with no engines but 4 APU's.

I'm not entirely joking either, I believe its engines are derived and or used as APU's.

Also, a 4 engine 757 would be a 707.

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 12:26 am
by LU9092
I think a better question is, "Can Boeing put a hump on a 777-9?"

  

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 1:45 am
by AirlineCritic
Quoting fanofjets (Reply 16):
How about a four-engine Boeing 757?

Heh.

Those two additional engines would finally give some legs to this underpowered aircraft  You could haul some serious fish with it. Sadly, Boeing made a big mistake in destroying the tooling.

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 5:01 am
by CALTECH
Quoting B737900 (Thread starter):
A question to the engineers: could the B747 fly on two 21st century engines?

You mean like this ?

http://www.cardatabase.net/modifiedairlinerphotos/photos/big/00005184.jpg

Quoting fanofjets (Reply 16):
How about a four-engine Boeing 757?

Boeing's 757-400

http://www.cardatabase.net/modifiedairlinerphotos/photos/big/00005993.jpg

http://www.cardatabase.net/modifiedairlinerphotos/photos/big/00001207.jpg

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 3:41 pm
by YellowRibbon
Quoting CALTECH (Reply 29):

The ATA reminds me of the Super 70 DC-8s! Very nice job.

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 3:55 pm
by B737900
Quoting CALTECH (Reply 29):
You mean like this ?

You mean like this ?

http://www.cardatabase.net/modifieda...inerphotos/photos/big/00005184.jpg

   Is that for real? Pretty good 'photo shop' if it's not.

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 4:04 pm
by CF-CPI
Quoting B737900 (Reply 31):
Is that for real? Pretty good 'photo shop' if it's not.

Scary how good digital fakery can be.

Someone actually proposed re-engining the Convair 880 with a pair of CFM56s, but realized there were too few airframes to make it worthwhile.

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 4:48 pm
by American 767
Quoting YellowRibbon (Reply 30):
The ATA reminds me of the Super 70 DC-8s! Very nice job.

Yes that's true. I think so too. I said in a post above that I would call it the resurrection of the 707 but I would also call it a DC-8MAX.

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 5:45 pm
by YellowRibbon
Quoting American 767 (Reply 33):

Well, MD merged with Boeing so they could name it the DC-8?

I'd like to call it the DC-8-85. Super 80 series/ DC-8 MAX

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 6:27 pm
by DarkSnowyNight
Quoting Gasman (Reply 13):
replaced by a mind-numbingly boring cylindrical sardine can with wings (aka the 773). We need to accept this, grieve and then vote with our wallets by flying the A380 whenever possible.

What's with the twin-hate?

You wouldn't call a Veyron "Just another boring 4 tyred road-appliance" would you?

There's more to whether a plane is interesting or not than whether it's a twin or a throw back.

Quoting Gasman (Reply 587):
But in 10+ years time, when engine technology has developed to the point where a VLA double decker twinjet is feasible, will Boeing re-enter the market? My guess is yes. Air travel is currently increasing at a stratospheric rate, but airport and ATC space is finite. Eventually, consolidating movements to perhaps slightly less frequent, but much larger aircraft will make more and more sense. I'm expecting Boeing to announce a new VLA sometime between 2020 and 2025.

We are at that point. Except for engine count, the 779 is more airplane than a 744 in everyway. Even the 748 can only outdo that one as a main deck cargo hauler.

I do firmly believe that a new twin VLA will happen sooner or later. Really later though. Maybe a double deck, maybe not.

But this won't be a reason for it. Air travel will continue to increase in overall volume, but the increase won't be steady and the ATC relief won't be felt by adding a few supers to the mix.

The capacity upscaling will need to come from CR200s turning into CS100s, E175s turning into 738Ms, A319s turning into A321s, etc.

As passengers, we're not giving a millimeter in frequency anytime soon. Airlines know this and they know the best ways to put more seats up is on the lower end of the scale, where they can add a lot more seats for concurrent volume, rather than trade frequency away for some Really Expensive VLAs.

VLAs will keep their place, but this is far more feasible in the form of 779s and A3511s than anything else going.

Quoting Gasman (Reply 17):

True, but there's no real harm in it - even if it has been asked before. Who amongst us doesn't fantasise/hypothesise about what might or might be possible in the aviation world? Without threads like these (from time to time) airliners.net would be a pretty colourless place.

Very true. None of us are here to write an insurance report.

RE: A B747 Two Holer?

Posted: Thu May 05, 2016 7:07 pm
by atypical
Quoting DarkSnowyNight (Reply 35):
I do firmly believe that a new twin VLA will happen sooner or later. Really later though. Maybe a double deck, maybe not.

I think that is a reasonable projection but I don't think it will happen before the fan size gets bumped up once again. This will require a decision on how to get that much clearance. Freakishly tall landing gear, overwing engines, high mount wings. The tall landing gear initially sounds good but then to consider gates, slides, service vehicles and that sounds as if it may be the worst. Have the manufactures given any indication of how they are going to cope with such massive fans?

RE: A B747 Two Holer?

Posted: Fri May 06, 2016 8:19 am
by LAX772LR
Quoting jetmatt777 (Reply 1):
This would also mean the elimination of the seats forward of the 1A door. I believe current requirements are that there must be emergency exits in front of the forward most occupied passenger seat.

Can't have pax more than 60ft (laterally) away from an exit, and must take obstruction into account.

Thus, if the first door on either side are ever blocked during an evac, that places pax in the nose more than 60ft laterally away from an available exit.

Would never get certified today, without the grandfathering in place. Airbus playfully tried to make a stink out of that, and the evac tests, in 2011.  



Quoting DarkSnowyNight (Reply 35):
There's more to whether a plane is interesting or not than whether it's a twin or a throw back.

      
....and people are going to have to do a better job recognizing/understanding that, since 99.999% of everything from here on out will be twins, for the foreseeable future