• Hi Guest! Forum rules have been updated. All users please read here.

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

Archibald

CLEARANCE: Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
3,370
Reaction score
956
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)
 

VTOLicious

CLEARANCE: Top Secret
Joined
Nov 24, 2008
Messages
667
Reaction score
265
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)
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.
 

Fluff

CLEARANCE: Confidential
Joined
Sep 9, 2019
Messages
181
Reaction score
75
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)
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.
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.
 

VTOLicious

CLEARANCE: Top Secret
Joined
Nov 24, 2008
Messages
667
Reaction score
265
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)
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.
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.
Flying wings are neither "inherent unstable" nor "generally unflyable aircraft".
 

Archibald

CLEARANCE: Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
3,370
Reaction score
956
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...
 

Fluff

CLEARANCE: Confidential
Joined
Sep 9, 2019
Messages
181
Reaction score
75
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....
 

VTOLicious

CLEARANCE: Top Secret
Joined
Nov 24, 2008
Messages
667
Reaction score
265
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.
 
Last edited:

Fluff

CLEARANCE: Confidential
Joined
Sep 9, 2019
Messages
181
Reaction score
75
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.
I pretty much agree with you, and respect your opinion.

I think we are talking about the same issue, just in different ways.
 

Sundog

CLEARANCE: Top Secret
Senior Member
Joined
Aug 2, 2006
Messages
2,753
Reaction score
197
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)
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.
 

Archibald

CLEARANCE: Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
3,370
Reaction score
956
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.
 

Sundog

CLEARANCE: Top Secret
Senior Member
Joined
Aug 2, 2006
Messages
2,753
Reaction score
197
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.
 

sferrin

CLEARANCE: Above Top Secret
Senior Member
Joined
Jun 3, 2011
Messages
13,040
Reaction score
1,079
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.
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)."
 

Archibald

CLEARANCE: Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
3,370
Reaction score
956
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 ?
 

Archibald

CLEARANCE: Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
3,370
Reaction score
956
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.
Many thanks, very interesting.
 

sferrin

CLEARANCE: Above Top Secret
Senior Member
Joined
Jun 3, 2011
Messages
13,040
Reaction score
1,079
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 ?
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:

 

kitnut617

CLEARANCE: Secret
Joined
Dec 15, 2006
Messages
362
Reaction score
76
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.
 

Attachments

Richard N

CLEARANCE: Secret
Senior Member
Joined
Jun 18, 2009
Messages
413
Reaction score
146
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

 
Top