Northrop XB/YB-35, YB-49 and YRB-49

A little speculative question... I'm often wondering whether an analog FBW as per the Arrow F-16 or Mirage 2000 could tame flying wings unherent instability. Or was digital FBW absolutely necessary ? (as per B-2)
 
Archibald said:
A little speculative question... I'm often wondering whether an analog FBW as per the Arrow F-16 or Mirage 2000 could tame flying wings unherent instability. Or was digital FBW absolutely necessary ? (as per B-2)
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Flying wings are not inherent unstable. They just need a lot more attention in the design & optimization process and are most likely less forgiving, once the wing stalls.
 
VTOLicious said:
Archibald said:
A little speculative question... I'm often wondering whether an analog FBW as per the Arrow F-16 or Mirage 2000 could tame flying wings unherent instability. Or was digital FBW absolutely necessary ? (as per B-2)
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Flying wings are not inherent unstable. They just need a lot more attention in the design & optimization process and are most likely less forgiving, once the wing stalls.
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I'm not an aircraft designer, but surely fulcrums come into this, in a flying wing the elevators are on the wing, so I would assume need to be massive to have an effect, if you move them 20-30 feet away from the wing, they become far more effective - if pitch is the most difficult area for non-fbw flying wings. So if it goes a bit south, you are more rapidly out of the recoverable zone, versus tail last, or indeed canards. Also said massive effect will have a further massive effect on drag, which is probably not what you want when in a difficult spot. FBW monitoring the aircraft, and the pilots inputs sounds like the way to go, and seems to have resulted in flyable aircraft, versus what appeared to be generally unflyable aircraft.
 
Fluff said:
VTOLicious said:
Archibald said:
A little speculative question... I'm often wondering whether an analog FBW as per the Arrow F-16 or Mirage 2000 could tame flying wings unherent instability. Or was digital FBW absolutely necessary ? (as per B-2)
Click to expand...
Flying wings are not inherent unstable. They just need a lot more attention in the design & optimization process and are most likely less forgiving, once the wing stalls.
Click to expand...
I'm not an aircraft designer, but surely fulcrums come into this, in a flying wing the elevators are on the wing, so I would assume need to be massive to have an effect, if you move them 20-30 feet away from the wing, they become far more effective - if pitch is the most difficult area for non-fbw flying wings. So if it goes a bit south, you are more rapidly out of the recoverable zone, versus tail last, or indeed canards. Also said massive effect will have a further massive effect on drag, which is probably not what you want when in a difficult spot. FBW monitoring the aircraft, and the pilots inputs sounds like the way to go, and seems to have resulted in flyable aircraft, versus what appeared to be generally unflyable aircraft.
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Flying wings are neither "inherent unstable" nor "generally unflyable aircraft".
 
Maybe you could provide some assertions to this claim instead of repeating the same mantra ? There is a reason why flying wings were abandonned between 1950 and 1980...
 
Fundamentally, you can follow the development from Wright Flyer, through to F16, 787 etc. Whilst I'm sure there are some obscure exceptions, nearly all aircraft accepted and making some production numbers, have found it safer/better to have a fuselage/empennage, and hang the control surfaces in separate places. Chopping off these empennages, and bolting everything to the wing, in the 30's, didn't work, even with a Test Pilot, they crashed. May have been 'outside' the envelope, it doesn't matter, because of the control limitations they could not get back inside the envelope in time. Computer power, and FBW etc made it possible to design such an aircraft, and control it = not crash. So our real world survey says not a good idea, until the control system made it manageable. Nit picking over specific wording doesn't invalidate the premise, that they didn't 'work'. If they had of worked we would all be travelling in them. Instead we travel in highly developed versions of 1960 designs....
 
It is a historical fact that flying wings had a hard time to transition from demonstrators /prototypes to production aircraft. There are many reasons for that, one of them being thight(er) CG limitations (compared to a conventional layout).

However, I refuse to call them "inherent unstable" or "generally unflyable"!

Like any type of aircraft, flying wings have a longitudinal stability margin and the range over which the CG is allowed to move is well specified. Inside this range the aircraft will self-correct longitudinal (pitch) disturbances without pilot input and is considered as inherent stable.
 
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VTOLicious said:
It is a historical fact that flying wings had a hard time to transition from demonstrators /prototypes to production aircraft. There are many reasons for that, one of them being thight(er) CG limitations (compared to a conventional layout).

However, I refuse to call them "inherent unstable" or "generally unflyable"!

Like any type of aircraft, flying wings have a longitudinal stability margin and the range over which the CG is allowed to move is well specified. Inside this range the aircraft will self-correct longitudinal (pitch) disturbances without pilot input and is considered as inherent stable.
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I pretty much agree with you, and respect your opinion.

I think we are talking about the same issue, just in different ways.
 
Archibald said:
A little speculative question... I'm often wondering whether an analog FBW as per the Arrow F-16 or Mirage 2000 could tame flying wings unherent instability. Or was digital FBW absolutely necessary ? (as per B-2)
Click to expand...

The YB-49 series had a yaw stability issue that was difficult to damp, so the nose would slightly wander side to side. However, Bendix made a system to fix that that was used successfully in the YRB-49. However, they were already buying B-36's by then, so I don't think they saw a need for the YRB-49. Plus the politics the government had towards Jack Northrop at the time for not merging/selling to Convair.
 
Ok. also the B-36 had a giganormous bomb bay able to handle the big first generation H-bombs. YB-35 / 49 bays were more fragmented.
Although the Atlas proved how fast could H-bombs shrink, when the big 5-engine design could be dropped for the familiar one.
 
What VTOLicious is saying is quite correct, regarding the CG limitations. Also, flying wings have more complex flight control systems, even though they are doable. As a result, until stealth became a requirement, it was easier to build conventional airframes. Also, the advent of advanced FCS allowed flying wings to use neutral stability, which also lowered trim drag. Advanced FCS systems also allow flying wings to avoid a problem with how flying wings operate in the stall envelope.

With flying wings, due to the way the flight controls work, i.e.-not having a separate tail, under accelerated loading, such as a tightening spiral turn, when the flying wing stalls it tends to stall at the center section while the outer wings are still under load. This creates a massive twist in the wing, since most of the mass is in the center section which can cause the outer portions of the wing to snap off due to the rapid dynamic structural loading. They believe this is what happened with the the YB-49; what caused it to come apart in flight. Advanced aerodynamics and FCS's allow this to be avoidable.
 
Archibald said:
Ok. also the B-36 had a giganormous bomb bay able to handle the big first generation H-bombs. YB-35 / 49 bays were more fragmented.
Although the Atlas proved how fast could H-bombs shrink, when the big 5-engine design could be dropped for the familiar one.
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Just to put that into perspective the B-36 could carry TWO 42,000lb Mk17/24 nuclear weapons or two of the 44,000lb T-12 conventional bombs. Or up to 138 500lb bombs. That's over 60% more than the B-1Bs 84.

"The Convair B-36 was the only aircraft designed to carry the T-12 Cloudmaker, a gravity bomb weighing 43,600 lb (19,800 kg) and designed to produce an earthquake bomb effect. Part of the testing process involved dropping two of the bombs on a single flight mission, one from 30,000 ft (9,100 m) and the second from 40,000 ft (12,000 m), for a total bomb load of 87,200 lb (39,600 kg)."
 
Wow. 87200 pounds of explosives... my mind is blown (lame pun not intentional). Shame the B-52 couldn't carry this in Vietnam. Could they put a pair of T-12 on the Hound Dog / X-15 wing pylons ?

I had always assumed the Tall boys / Grand slam were the largest bombs ever. Or MOAB. Ain't T-12 larger than MOAB ?
 
Sundog said:
What VTOLicious is saying is quite correct, regarding the CG limitations. Also, flying wings have more complex flight control systems, even though they are doable. As a result, until stealth became a requirement, it was easier to build conventional airframes.

Also, the advent of advanced FCS allowed flying wings to use neutral stability, which also lowered trim drag.

Advanced FCS systems also allow flying wings to avoid a problem with how flying wings operate in the stall envelope.
With flying wings, due to the way the flight controls work, i.e.-not having a separate tail, under accelerated loading, such as a tightening spiral turn, when the flying wing stalls it tends to stall at the center section while the outer wings are still under load. This creates a massive twist in the wing, since most of the mass is in the center section which can cause the outer portions of the wing to snap off due to the rapid dynamic structural loading. They believe this is what happened with the the YB-49; what caused it to come apart in flight. Advanced aerodynamics and FCS's allow this to be avoidable.
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Many thanks, very interesting.
 
Archibald said:
Wow. 87200 pounds of explosives... my mind is blown (lame pun not intentional). Shame the B-52 couldn't carry this in Vietnam. Could they put a pair of T-12 on the Hound Dog / X-15 wing pylons ?

I had always assumed the Tall boys / Grand slam were the largest bombs ever. Or MOAB. Ain't T-12 larger than MOAB ?
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MOAB is a paltry 21,000lbs. MOP is 30,000lbs (though a much higher percentage of that is steel casing). Here's a B2A dropping a pair of the latter:

 
To add to the above post by sferrin, this is a comparison pic of the T-12 and a Grand Slam and Tallboy in 1/72 scale. I got the dimensions for the T-12 from a website which now seems to have been discontinued.
 

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Properly designed flying wings don't need no stinkin' advanced FCS or drag rudders!! The Alsomitra Macrocarpa seeds natural flying wings were the inspiration for Alexander Lippisch's and other German designers flying wings as well as the wing of the Taube. Lippisch's Me-163 was the fastest aircraft of WW2 and I have never read of it having anything but exceptional flying qualities.

A couple of current German model flying wings inspired by the flying seeds are in the last 2 vids.

Alsomitra macrocarpa seed flight:


Seed aviation, Travelling, The Private Life of Plants BBC Two:


Zanonia Macrocarpa 1100mm 3D printed Flying Wing Glider:


NFROB 2020: Build thread here: http://www.rc-network.de/forum/showthread.php/773466-NOT-FOR-RES-ONLY-BOW

 
hesham said:
And from the member Ryan Crierie,


here is the Northrop YB-35B and YRB-49A drawings.


Copyright Free Drawings of Aircraft (Warning 300 DPI) - Matrix Games Forums

www.matrixgames.com www.matrixgames.com
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YB-35B was the new designation for the Northrop RB-35B (which was to have been used to train crews to fly the RB-49 reconnaissance flying wing) after the YB-35s selected for conversion to RB-35B configuration were classified as flying shells devoid of tactical equipment after the production order for 30 RB-49As was cancelled in January 1949. The YB-35B differed from the YRB-49A only in lacking provisions for any military equipment. As noted by Tony Chong in his book Flying Wings and Radical Things, the RB-35B received the project number N-39, and when it was redesignated YB-35B, it received the new company designation N-51.
 
I found these technical documents pertaining to the Northrop RB-49A reconnaissance flying wing at Ebay:
www.ebay.com

COPY vtg Northrop RB-49A flying wing blueprint "Master Lines & Stations" DWG 700 | eBay

Hawthorne, CA Northrop Field B-35 B35 YB-49 B-49 B49 RB-49A XB-35 water line station number rear spar trailing edge wing leading. The drawing is marked up in color to highlight bulkheads and the number 1012 is hand written in red pencil but the print is in otherwise good condition (again, for...
www.ebay.com
www.ebay.com

COPY vtg Northrop RB-49A flying wing blueprint Proposed Antenna Location 7/13/48 | eBay

Hawthorne, CA Northrop Field B-35 B35 YB-49 B-49 B49 RB-49A. This item would be of particular interest to any fan of the history of the Northrop Flying wing aircraft but would also be of interest to any military aviation buff in general.
www.ebay.com
www.ebay.com

COPY vtg Northrop RB-49A flying wing blueprint "Diagram Wing Structure" 6/22/48 | eBay

Hawthorne, CA Northrop Field B-35 B35 YB-49 B-49 B49 RB-49A XB-35 bomber. "CONFIDENTIAL" is crossed out on the original and the date is hand-written on it, and there is an age-yellowed crease which is replicated in the copy.
www.ebay.com
www.ebay.com

COPY vtg Northrop B-49 flying wing blueprint RB-49A Diagram camera door openings | eBay

Hawthorne, CA escape hatch. This item would be of particular interest to any fan of the history of the Northrop Flying wing aircraft but would also be of interest to any military aviation buff in general.
www.ebay.com
 
If anyone's aware, the RB-49 (originally FB-49) photo-reconnaissance flying wing was given the company designation N-37, whereas the YRB-49A was called N-41 by Northrop. As described on pages 55 to 56 of the book Flying Wings and Radical Things, the RB-49A (originally FB-49A), of which 30 aircraft were ordered (serial numbers 49-200/229) was powered by eight General Electric J47s; the initial RB-49A design (N-37 sans suffixe) had the eight J47s buried in the wing, but when it was clear that four J47s could not fit comfortably in the same space as four J35s, the RB-49A design evolved into a configuration with six J47s buried in the wing and the other two J47s in individual pods below the wing (N-37D). The proposed RB-49B (N-37A) was powered by six Westinghouse J40 turbojets buried in the wing, while the RB-49C (N-37B) would have had two T37 turboprops and two General Electric J47s.
 
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Tony Chong's book Flying Wings and Radical Things describes on page 57 to 58 an improved version of the YB-49, the N-40. The N-40 was similar to the YB-49 in general layout but differed in having a center bomb bay measuring 170 inches long, 80 inches wide, and 80 inches deep, therefore big enough to carry large diameter nuclear weapons, an APQ-24 bombing/navigation suite on the lower aft part of the crew nacelle to improve bombing accuracy, a chin turret with four 0.50-caliber machine guns on the starboard nose area outboard of the bombardier's glass and an aft upper fuselage turret with 0.50-caliber machine guns, and an E-7 autopilot. The N-40, like the RB-49A, was powered by eight General Electric J47 turbojets, with six in the wing and two in individual pods below the wing; three engine options were considered for the N-40: (1) six Westinghouse J40s or Pratt & Whitney J48s buried in the wing and (2) two T37s and two or four J40s. On August 23, 1948, an amendment to the RB-49A production contract was made to convert one of the RB-49As to N-40 configuration in order for the USAF to rectify stability problems with the YB-49 with the hope of the Air Force placing a production contract for the N-40.
 
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Seldom-noticed photos of the first YB-49 prototype after it was destroyed in a crash during a high-speed taxi run on March 15, 1950 are on pages 175 to 177 of the book Northrop Flying Wings by Garry Pape and John Campbell.
 
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Cutaway view of the planned production RB-49A reconnaissance flying wing. From Garry Pape and John Campbell's 1995 book Northrop Flying Wings.
 

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Rare photos of the nearly complete Northrop RB-35B airframe 42-102377. From Garry Pape and John Campbell's 1995 book Northrop Flying Wings.
 

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View: https://www.reddit.com/r/aviation/comments/ey4uc5/the_evolution_of_the_b2_the_yb35_yb49_and_the_b2/
 

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