What are your thoughts on the cancelled Boeing 7J7?
Posted by Realistic-Bid9464@reddit | aviation | View on Reddit | 35 comments
It would have been a short to medium haul airliner with a capacity of 150. Intended to replace the earlier Boeing 727 trijets, this aircraft would have utilized unique propfan engines. The Japan Aircraft Development Corporation would be the parts supplier to this aircraft , hence the 'J' in the name.
aka_Handbag@reddit
I think it could’ve been neat.
ThirdSunRising@reddit
The fact that Boeing received the MD90 and made a batch of Boeing 717 airplanes and then just kinda abandoned it, tells us what we need to know about this. They received a slightly bigger, fully developed in-production version of this thing and walked away
JaggedMetalOs@reddit
Well, not a production version of that thing because it has propfan engines.
agha0013@reddit
the unducted fan engines were quite good at what they did, except for the noise.
I think CFM/SNECMA is trying to revive that idea but I doubt they've been able to do anything significant about the noise issue of the main fan being unducted. Those cowlings on modern turbofans do a lot of work reducing noise.
aside from that, this thing could have been a suitable way to make a new line of more modern narrow bodies to replace the 737 family but it never happened.
DoctorFrick@reddit
I can confirm the noise. Saw this being tested at Mojave many years ago, and even in the pre-Hushkit 727 era, it was the loudest aircraft I'd ever heard.
I remember telling someone "this thing could be the greatest thing since jet engines and that noise will still ensure it never lands at a metropolitan airport."
GeraintLlanfrechfa@reddit
Have you been on the Concorde and tu 144?
DoctorFrick@reddit
No, sir.
Much too poor for that!
GeraintLlanfrechfa@reddit
Yeh me neither, I heard and read that the Concorde was loud inside but bearable, while you kinda couldn’t have a conversation aboard the tu144
NF-104@reddit
At least it wasn’t as loud as the XF-84H Thunderscreech!
Wiki
DoctorFrick@reddit
I will say, after getting a figurative haircut from a V-22 at rooftop height, there might be a new challenger to the UDF's claim of World Champion Noisemaker!
Cogitoergoscribo@reddit
You might be surprised to learn that the new version of the unducted fan, project name RISE, is quieter than a ducted one now and much quieter than the version in OP’s picture. The second set of blades no longer counter-rotates (in either direction) and they used modern supercomputers to shape the blades to reduce air turbulence and eddies and such to greatly reduce their noise.
whiskeytown79@reddit
What's the advantage of a non-ducted propfan like this? Presumably they have positives that were being considered apart from the noise negative.
Captain_Alaska@reddit
Fan size. The largest geared turbofans in the world still lag behind turboprops in terms of fan diameter, propfans aim to close the gap without requiring a monstrously huge cowling around the thing.
AbeFromanEast@reddit
Propfans will be back because it's the next step to get 15% fuel savings. After that it'll be blended wing bodies to get 25% more fuel savings. The concepts will probably be combined.
discombobulated38x@reddit
They may be back, but I doubt it'll happen any time soon. Only one of the big 3 is doing it and that's because they don't fancy the geared turbofan challenge.
AbeFromanEast@reddit
They'll be back when high oil/jet fuel prices stay sustained for a long time period.
Current genius and well-thought-out actions in the Middle East may provide that era of high prices needed to get propfans off the test-stand and onto commercial aircraft.
Bright-light320@reddit
Do they have concepts of large propfan planes ready to build? Otherwise it will take ages...
sofixa11@reddit
Yes: https://en.wikipedia.org/wiki/CFM_International_RISE
AbeFromanEast@reddit
There were large propfans on commercial passenger test aircraft in 1984. Only the oil crash in 1986 stopped their widespread deployment.
PrismDoug@reddit
So which manufacturer(s) should I invest in?
discombobulated38x@reddit
That's very true to be fair
sofixa11@reddit
SNECMA hasn't been a thing in decades, it's now Safran. It's 50% of CFM alongside GE, and yes they have the CFN Rise, which combats the noise issue with variable geometry blades.
hat_eater@reddit
With engines in the back they'd be a good case for ANC, no?
Realistic-Bid9464@reddit (OP)
I do still think that for a rear-mounted twinjets the wings should have been further back, like on the MD80 and fokker 70/100.
agha0013@reddit
probably would have been in the end, don't take too much from early renderings before a real design was completed.
Look at how very different the actual 787 is compared to all the early renderings, same for the A380. they saw some significant changes once reality set in.
flyawaybye@reddit
Thanks for the history! I didn’t realize this was a twin aisle jet!
“The 7J7 was to have a twin-aisle (2+2+2) seating configuration, giving a wide and spacious cabin for its class, with no passenger more than one seat from an aisle. Alternatively, the aircraft could fit a high-density, seven-abreast (2+3+2) seating configuration with 17-inch wide (43 cm)seats and 18-inch wide (46 cm) aisles. The fuselage diameter of 188 inches (478 cm).” -Wiki
BoringBob84@reddit
I think it would have taken the airlines about 5 minutes to request a single aisle, 3 + 4 configuration to maximize revenue. That extra aisle is a large number of paying passengers.
Tony_Three_Pies@reddit
I wonder how much evacuation requirements would affect that. I feel like a 4+3 config down one aisle would take forever to evacuate.
Not to mention being in the window seat of the 4 side would just suck in general.
BoringBob84@reddit
Good point. That configuration may not be certifiable. And like you said, it would suck for everyone. Imagine the flight attendants trying to communicate with those people four seats away!
BasilProfessional09@reddit
Looks like the prototype Maeve MJ500
CaterpillarNo4927@reddit
Where are the fuel tanks located? Curious about the weight balancing with so much less weight in the wings
Ancient_Narwhal_9524@reddit
The majority if not all of the fuel would still be in the wings
laserkitt3nz@reddit
As a frequent flyer, noise is one of my biggest gripes about flying so good riddance as far as I'm concerned
ABCDOMG@reddit
Iirc the CFM rise is supposed to have dealt with the noise issue. Looking forward to the next gen single aisle from the Airbus side to see if they can actually get it certified and sold.
SentientFotoGeek@reddit
Too loud for cities and other noise sensitive areas. Not the quantum leap in efficiency that they were touted to be.